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Sample records for aftershock sequence etas

  1. Estimating Spatially Variable Parameters of the Epidemic Type Aftershock Sequence (ETAS) in California

    NASA Astrophysics Data System (ADS)

    Nandan, Shyam; Ouillon, Guy; Sornette, Didier; Wiemer, Stefan

    2016-04-01

    The ETAS model is widely employed to model the spatio-temporal distribution of earthquakes, generally using spatially invariant parameters, which is most likely a gross simplification considering the extremely heterogeneous structure of the Earth's crust. We propose an efficient method for the estimation of spatially varying parameters, using an expectation maximization (EM) algorithm and spatial Voronoi tessellations. We assume that each Voronoi cell is characterized by a set of eight constant ETAS parameters. For a given number of randomly distributed cells, Vi=1 to N, we jointly invert the ETAS parameters within each cell using an EM algorithm. This process is progressively repeated several times for a given N (which controls the complexity), which is itself increased incrementally. We use the Bayesian Information Criterion (BIC) to rank all the inverted models given their likelihood and complexity and select the top 1% models to compute the average model at any location. Using a synthetic catalog, we also check that the proposed method correctly inverts the known parameters. We apply the proposed method to earthquakes (M>=3) included in the ANSS catalog that occurred within the time period 1981-2016 in the spatial polygon defined by RELM/CSEP around California. The results indicate significant spatial variation of the ETAS parameters. Using these spatially variable estimates of ETAS parameters, we are better equipped to answer some important questions: (1) What is the seismic hazard (both long- and short-term) in a given region? (2) What kind of earthquakes dominate triggering? (3) are there regions where earthquakes are most likely preceded by foreshocks? Last but not the least, a possible correlation of the spatially varying ETAS parameters with spatially variable geophysical properties can lead to an improved understanding of the physics of earthquake triggering beside providing physical meaning to the parameters of the purely statistical ETAS model.

  2. An experimental approach to non - extensive statistical physics and Epidemic Type Aftershock Sequence (ETAS) modeling. The case of triaxially deformed sandstones using acoustic emissions.

    NASA Astrophysics Data System (ADS)

    Stavrianaki, K.; Vallianatos, F.; Sammonds, P. R.; Ross, G. J.

    2014-12-01

    Fracturing is the most prevalent deformation mechanism in rocks deformed in the laboratory under simulated upper crustal conditions. Fracturing produces acoustic emissions (AE) at the laboratory scale and earthquakes on a crustal scale. The AE technique provides a means to analyse microcracking activity inside the rock volume and since experiments can be performed under confining pressure to simulate depth of burial, AE can be used as a proxy for natural processes such as earthquakes. Experimental rock deformation provides us with several ways to investigate time-dependent brittle deformation. Two main types of experiments can be distinguished: (1) "constant strain rate" experiments in which stress varies as a result of deformation, and (2) "creep" experiments in which deformation and deformation rate vary over time as a result of an imposed constant stress. We conducted constant strain rate experiments on air-dried Darley Dale sandstone samples in a variety of confining pressures (30MPa, 50MPa, 80MPa) and in water saturated samples with 20 MPa initial pore fluid pressure. The results from these experiments used to determine the initial loading in the creep experiments. Non-extensive statistical physics approach was applied to the AE data in order to investigate the spatio-temporal pattern of cracks close to failure. A more detailed study was performed for the data from the creep experiments. When axial stress is plotted against time we obtain the trimodal creep curve. Calculation of Tsallis entropic index q is performed to each stage of the curve and the results are compared with the ones from the constant strain rate experiments. The Epidemic Type Aftershock Sequence model (ETAS) is also applied to each stage of the creep curve and the ETAS parameters are calculated. We investigate whether these parameters are constant across all stages of the curve, or whether there are interesting patterns of variation. This research has been co-funded by the European Union

  3. Intermediate-term forecasting of aftershocks from an early aftershock sequence: Bayesian and ensemble forecasting approaches

    NASA Astrophysics Data System (ADS)

    Omi, Takahiro; Ogata, Yosihiko; Hirata, Yoshito; Aihara, Kazuyuki

    2015-04-01

    Because aftershock occurrences can cause significant seismic risks for a considerable time after the main shock, prospective forecasting of the intermediate-term aftershock activity as soon as possible is important. The epidemic-type aftershock sequence (ETAS) model with the maximum likelihood estimate effectively reproduces general aftershock activity including secondary or higher-order aftershocks and can be employed for the forecasting. However, because we cannot always expect the accurate parameter estimation from incomplete early aftershock data where many events are missing, such forecasting using only a single estimated parameter set (plug-in forecasting) can frequently perform poorly. Therefore, we here propose Bayesian forecasting that combines the forecasts by the ETAS model with various probable parameter sets given the data. By conducting forecasting tests of 1 month period aftershocks based on the first 1 day data after the main shock as an example of the early intermediate-term forecasting, we show that the Bayesian forecasting performs better than the plug-in forecasting on average in terms of the log-likelihood score. Furthermore, to improve forecasting of large aftershocks, we apply a nonparametric (NP) model using magnitude data during the learning period and compare its forecasting performance with that of the Gutenberg-Richter (G-R) formula. We show that the NP forecast performs better than the G-R formula in some cases but worse in other cases. Therefore, robust forecasting can be obtained by employing an ensemble forecast that combines the two complementary forecasts. Our proposed method is useful for a stable unbiased intermediate-term assessment of aftershock probabilities.

  4. Triggered Swarms and Induced Aftershock Sequences in Geothermal Systems

    NASA Astrophysics Data System (ADS)

    Shcherbakov, R.; Turcotte, D. L.; Yikilmaz, M. B.; Kellogg, L. H.; Rundle, J. B.

    2015-12-01

    Natural geothermal systems, which are used for energy generation, are usually associated with high seismic activity. This can be related to the large-scale injection and extraction of fluids to enhance geothermal recovery. This results in the changes of the pore pressure and pore-elastic stress field and can stimulate the occurrence of earthquakes. These systems are also prone to triggering of seismicity by the passage of seismic waves generated by large distant main shocks. In this study, we analyze clustering and triggering of seismicity at several geothermal fields in California. Particularly, we consider the seismicity at the Geysers, Coso, and Salton Sea geothermal fields. We analyze aftershock sequences generated by local large events with magnitudes greater than 4.0 and earthquake swarms generated by several significant long distant main shocks. We show that the rate of the aftershock sequences generated by the local large events in the two days before and two days after the reference event can be modelled reasonably well by the time dependent Epidemic Type Aftershock Sequence (ETAS) model. On the other hand, the swarms of activity triggered by large distant earthquakes cannot be described by the ETAS model. To model the increase in the rate of seismicity associated with triggering by large distant main shocks we introduce an additional time-dependent triggering mechanism into the ETAS model. In almost all cases the frequency-magnitude statistics of triggered sequences follow Gutenberg-Richter scaling to a good approximation. The analysis indicates that the seismicity triggered by relatively large local events can initiate sequences similar to regular aftershock sequences. In contrast, the distant main shocks trigger swarm like activity with faster decaying rates.

  5. The (Un)Productivity of the 2014 M6.0 South Napa Aftershock Sequence

    NASA Astrophysics Data System (ADS)

    Llenos, A. L.

    2014-12-01

    The M6.0 South Napa mainshock produced fewer aftershocks than expected for a California earthquake of its magnitude, which became apparent a few days into the sequence. In the first 4.5 days, only 59 M≥1.8 aftershocks had occurred, the largest of which was a M3.9 that happened a little over two days after the mainshock. In contrast, during the same time period the 2004 M6.0 Parkfield earthquake had over 220 M≥1.8 aftershocks, 6 of which were M≥4. Here I investigate the aftershock productivity and other sequence statistics of the South Napa sequence and compare it with other M~6 California mainshock-aftershock sequences. By focusing on similar size events, they have similar finite extents within the seismotectonic environment. While the productivities of these sequences vary quite a bit, the b-values of the magnitude-frequency distributions all fall in the 0.6-0.8 range for the northern California sequences, slightly lower than the b-value of ~1 typical of southern California seismicity. Despite the relatively low productivity of the South Napa sequence, I show that the Epidemic-Type Aftershock Sequence (ETAS) model (Ogata, JASA, 1988) describes the sequence well and investigate whether the ETAS model parameters suggest that low-productivity sequences are typical for the region. I also explore how quickly after a mainshock these types of models can capture the low productivity of the sequence. The productivity of a sequence is a critical parameter in determining the aftershock probabilities reported in the days following the mainshock. Therefore, the sooner an accurate representation of the aftershock productivity can be obtained, the sooner more accurate aftershock probability reports can be produced.

  6. A random effects epidemic-type aftershock sequence model

    PubMed Central

    Lin, Feng-Chang

    2013-01-01

    We consider an extension of the temporal epidemic-type aftershock sequence (ETAS) model with random effects as a special case of a well-known doubly stochastic self-exciting point process. The new model arises from a deterministic function that is randomly scaled by a nonnegative random variable, which is unobservable but assumed to follow either positive stable or one-parameter gamma distribution with unit mean. Both random effects models are of interest although the one-parameter gamma random effects model is more popular when modeling associated survival times. Our estimation is based on the maximum likelihood approach with marginalized intensity. The methods are shown to perform well in simulation experiments. When applied to an earthquake sequence on the east coast of Taiwan, the extended model with positive stable random effects provides a better model fit, compared to the original ETAS model and the extended model with one-parameter gamma random effects. PMID:24039322

  7. A random effects epidemic-type aftershock sequence model.

    PubMed

    Lin, Feng-Chang

    2011-04-01

    We consider an extension of the temporal epidemic-type aftershock sequence (ETAS) model with random effects as a special case of a well-known doubly stochastic self-exciting point process. The new model arises from a deterministic function that is randomly scaled by a nonnegative random variable, which is unobservable but assumed to follow either positive stable or one-parameter gamma distribution with unit mean. Both random effects models are of interest although the one-parameter gamma random effects model is more popular when modeling associated survival times. Our estimation is based on the maximum likelihood approach with marginalized intensity. The methods are shown to perform well in simulation experiments. When applied to an earthquake sequence on the east coast of Taiwan, the extended model with positive stable random effects provides a better model fit, compared to the original ETAS model and the extended model with one-parameter gamma random effects.

  8. How Long is an Aftershock Sequence?

    NASA Astrophysics Data System (ADS)

    Godano, Cataldo; Tramelli, Anna

    2016-07-01

    The occurrence of a mainschok is always followed by aftershocks spatially distributed within the fault area. The aftershocks rate decay with time is described by the empirical Omori law which was inferred by catalogues analysis. The sequences discrimination within catalogues is not a straightforward operation, especially for low-magnitude mainshocks. Here, we describe the rate decay of the Omori law obtained using different sequence discrimination tools and we discover that, when the background seismicity is excluded, the sequences tend to last for the temporal extension of the catalogue.

  9. Processing Aftershock Sequences Using Waveform Correlation

    NASA Astrophysics Data System (ADS)

    Resor, M. E.; Procopio, M. J.; Young, C. J.; Carr, D. B.

    2008-12-01

    For most event monitoring systems, the objective is to keep up with the flow of incoming data, producing a bulletin with some modest, relatively constant, time delay after present time, often a period of a few hours or less. Because the association problem scales exponentially and not linearly with the number of detections, a dramatic increase in seismicity due to an aftershock sequence can easily cause the bulletin delay time to increase dramatically. In some cases, the production of a bulletin may cease altogether, until the automatic system can catch up. For a nuclear monitoring system, the implications of such a delay could be dire. Given the expected similarity between a mainshock and aftershocks, it has been proposed that waveform correlation may provide a powerful means to simultaneously increase the efficiency of processing aftershock sequences, while also lowering the detection threshold and improving the quality of the event solutions. However, many questions remain unanswered. What are the key parameters for achieving the best correlations between waveforms (window length, filtering, etc.), and are they sequence-dependent? What is the overall percentage of similar events in an aftershock sequence, i.e. what is the maximum level of efficiency that a waveform correlation could be expected to achieve? Finally, how does this percentage of events vary among sequences? Using data from the aftershock sequence for the December 26, 2004 Mw 9.1 Sumatra event, we investigate these issues by building and testing a prototype waveform correlation event detection system that automatically expands its library of known events as new signatures are indentified in the aftershock sequence (by traditional signal detection and event processing). Our system tests all incoming data against this dynamic library, thereby identify any similar events before traditional processing takes place. In the region surrounding the Sumatra event, the NEIC EDR contains 4997 events in the 9

  10. Statistical estimation of the duration of aftershock sequences

    NASA Astrophysics Data System (ADS)

    Hainzl, S.; Christophersen, A.; Rhoades, D.; Harte, D.

    2016-05-01

    It is well known that large earthquakes generally trigger aftershock sequences. However, the duration of those sequences is unclear due to the gradual power-law decay with time. The triggering time is assumed to be infinite in the epidemic type aftershock sequence (ETAS) model, a widely used statistical model to describe clustering phenomena in observed earthquake catalogues. This assumption leads to the constraint that the power-law exponent p of the Omori-Utsu decay has to be larger than one to avoid supercritical conditions with accelerating seismic activity on long timescales. In contrast, seismicity models based on rate- and state-dependent friction observed in laboratory experiments predict p ≤ 1 and a finite triggering time scaling inversely to the tectonic stressing rate. To investigate this conflict, we analyse an ETAS model with finite triggering times, which allow smaller values of p. We use synthetic earthquake sequences to show that the assumption of infinite triggering times can lead to a significant bias in the maximum likelihood estimates of the ETAS parameters. Furthermore, it is shown that the triggering time can be reasonably estimated using real earthquake catalogue data, although the uncertainties are large. The analysis of real earthquake catalogues indicates mainly finite triggering times in the order of 100 days to 10 years with a weak negative correlation to the background rate, in agreement with expectations of the rate- and state-friction model. The triggering time is not the same as the apparent duration, which is the time period in which aftershocks dominate the seismicity. The apparent duration is shown to be strongly dependent on the mainshock magnitude and the level of background activity. It can be much shorter than the triggering time. Finally, we perform forward simulations to estimate the effective forecasting period, which is the time period following a mainshock, in which ETAS simulations can improve rate estimates after the

  11. The Aftershock Risk Index - quantification of aftershock impacts during ongoing strong-seismic sequences

    NASA Astrophysics Data System (ADS)

    Schaefer, Andreas; Daniell, James; Khazai, Bijan; Wenzel, Friedemann

    2016-04-01

    The occurrence and impact of strong earthquakes often triggers the long-lasting impact of a seismic sequence. Strong earthquakes are generally followed by many aftershocks or even strong subsequently triggered ruptures. The Nepal 2015 earthquake sequence is one of the most recent examples where aftershocks significantly contributed to human and economic losses. In addition, rumours about upcoming mega-earthquakes, false predictions and on-going cycles of aftershocks induced a psychological burden on the society, which caused panic, additional casualties and prevented people from returning to normal life. This study shows the current phase of development of an operationalised aftershock intensity index, which will contribute to the mitigation of aftershock hazard. Hereby, various methods of earthquake forecasting and seismic risk assessments are utilised and an integration of the inherent aftershock intensity is performed. A spatio-temporal analysis of past earthquake clustering provides first-hand data about the nature of aftershock occurrence. Epidemic methods can additionally provide time-dependent variation indices of the cascading effects of aftershock generation. The aftershock hazard is often combined with the potential for significant losses through the vulnerability of structural systems and population. A historical database of aftershock socioeconomic effects from CATDAT has been used in order to calibrate the index based on observed impacts of historical events and their aftershocks. In addition, analytical analysis of cyclic behaviour and fragility functions of various building typologies are explored. The integration of many different probabilistic computation methods will provide a combined index parameter which can then be transformed into an easy-to-read spatio-temporal intensity index. The index provides daily updated information about the probability of the inherent seismic risk of aftershocks by providing a scalable scheme fordifferent aftershock

  12. Properties of aftershock sequences in southern California

    NASA Astrophysics Data System (ADS)

    Kisslinger, Carl; Jones, Lucile M.

    1991-07-01

    The temporal behavior of 39 aftershock sequences in southern California, 1933-1988, was modeled by the modified Omori relation. Minimum magnitudes for completeness of each sequence catalog were determined, and the maximum likelihood estimates of the parameters K, p, and c, with the standard errors on each, were determined by the Ogata algorithm. The b value of each sequence was also calculated. Many of the active faults in the region, both strike slip and thrust, were sampled. The p values were graded in terms of the size of the standard error relative to the p value itself. Most of the sequences were modeled well by the Omori relation. Many of the sequences had p values close to the mean of the whole data set, 1.11±0.25, but values significantly different from the mean, as low as 0.7 and as high as 1.8, exist. No correlation of p with either the b value of the sequence or the mainshock magnitude was found. The results suggest a direct correlation of p values is with surface heat flow, with high values in the Salton Trough (high heat flow) and one low value in the San Bernardino Mountains and on the edge of the Ventura Basin (both low heat flow). The large fraction of the sequences with p values near the mean are at locations where the heat flow is near the regional mean, 74 mW/m2. If the hypothesis that aftershock decay rate is controlled by temperature at depth is valid, the effects of other factors such as heterogeneity of the fault zone properties are superimposed on the background rate determined by temperature. Surface heat flow is taken as an indicator of crustal temperature at hypocentral depths, but the effects on heat flow of convective heat transport and variations in near-surface thermal conductivity invalidate any simple association of local variations in heat flow with details of the subsurface temperature distribution. The interpretation is that higher temperatures in the aftershock source volume caused shortened stress relaxation times in the fault

  13. Evidence for fluid-triggering underlying the year 2014 aftershock sequences in NW Bohemia

    NASA Astrophysics Data System (ADS)

    Hainzl, S.; Fischer, T.; Cermakova, H.; Bachura, M.; Vlcek, J.

    2015-12-01

    The West Bohemia/Vogtland region, central Europe, is a place of localized repeating swarm activity continuously monitored during the last two decades, allowing a detailed study of the driving mechanisms. Previous earthquake episodes where characterized by swarm-type activity with gradual onsets and decays which were not related to mainshocks. However, the latest activity in the year 2014 occurred exactly in the same location as previous swarm activity but consisted of three classical aftershock sequences triggered by a M4.4 event and two ~M3.5 events. The apparent system change from swarm-type to mainshock-aftershock characteristics can have important implications for the understanding of swarm and aftershock generation as well as for seismic hazard assessment in this region. Thus we have analyzed in detail the spatiotemporal aftershock sequence based on a relocated earthquake catalog. Our analysis shows that the largest mainshock occurred in a step-over region of the fault plane with increased Coulomb stress due to previous activity. Its rupture plane connecting both segments is significantly rotated compared to most aftershocks, which occurred in-plane. The aftershock characteristics are classical in the way that (i) the aftershocks are clearly triggered by the mainshock, (ii) the maximum magnitude of the aftershocks is approximately 1.2 units less than the mainshock magnitude (Bath law), and (iii) the decay can be well fitted by the Omori-Utsu law. However, the absolute number of aftershocks and the fitted c and p values of the Omori-Utsu decay are significantly larger than for typical sequences. The fit of the epidemic type aftershock sequence (ETAS) model reveals a time-dependent background activity which exponentially decays with time after the mainshock. Pore pressure simulations with an exponentially decreasing flow rate of the fluid source show a good agreement with the observed spatial migration front of the aftershocks extending approximately with log

  14. On the relationship between lower magnitude thresholds and bias in epidemic-type aftershock sequence parameter estimates

    NASA Astrophysics Data System (ADS)

    Schoenberg, Frederic Paik; Chu, Annie; Veen, Alejandro

    2010-04-01

    Modern earthquake catalogs are often described using spatial-temporal point process models such as the epidemic-type aftershock sequence (ETAS) models of Ogata (1998). Earthquake catalogs often have issues of incompleteness and other inaccuracies for earthquakes of magnitude below a certain threshold, and such earthquakes are typically removed prior to fitting a point process model. This paper investigates the bias in the parameters in ETAS models introduced by the removal of the smallest events. It is shown that in the case of most of the ETAS parameters, the bias increases approximately exponentially as a function of the lower magnitude cutoff.

  15. Statistical Variability and Tokunaga Branching of Aftershock Sequences Utilizing BASS Model Simulations

    NASA Astrophysics Data System (ADS)

    Yoder, Mark R.; Van Aalsburg, Jordan; Turcotte, Donald L.; Abaimov, Sergey G.; Rundle, John B.

    2013-01-01

    Aftershock statistics provide a wealth of data that can be used to better understand earthquake physics. Aftershocks satisfy scale-invariant Gutenberg-Richter (GR) frequency-magnitude statistics. They also satisfy Omori's law for power-law seismicity rate decay and Båth's law for maximum-magnitude scaling. The branching aftershock sequence (BASS) model, which is the scale-invariant limit of the epidemic-type aftershock sequence model (ETAS), uses these scaling laws to generate synthetic aftershock sequences. One objective of this paper is to show that the branching process in these models satisfies Tokunaga branching statistics. Tokunaga branching statistics were originally developed for drainage networks and have been subsequently shown to be valid in many other applications associated with complex phenomena. Specifically, these are characteristic of a universality class in statistical physics associated with diffusion-limited aggregation. We first present a deterministic version of the BASS model and show that it satisfies the Tokunaga side-branching statistics. We then show that a fully stochastic BASS simulation gives similar results. We also study foreshock statistics using our BASS simulations. We show that the frequency-magnitude statistics in BASS simulations scale as the exponential of the magnitude difference between the mainshock and the foreshock, inverse GR scaling. We also show that the rate of foreshock occurrence in BASS simulations decays inversely with the time difference between foreshock and mainshock, an inverse Omori scaling. Both inverse scaling laws have been previously introduced empirically to explain observed foreshock statistics. Observations have demonstrated both of these scaling relations to be valid, consistent with our simulations. ETAS simulations, in general, do not generate Båth's law and do not generate inverse GR scaling.

  16. Implications of an inverse branching aftershock sequence model.

    PubMed

    Turcotte, D L; Abaimov, S G; Dobson, I; Rundle, J B

    2009-01-01

    The branching aftershock sequence (BASS) model is a self-similar statistical model for earthquake aftershock sequences. A prescribed parent earthquake generates a first generation of daughter aftershocks. The magnitudes and times of occurrence of the daughters are obtained from statistical distributions. The first generation daughter aftershocks then become parent earthquakes that generate second generation aftershocks. The process is then extended to higher generations. The key parameter in the BASS model is the magnitude difference Deltam* between the parent earthquake and the largest expected daughter earthquake. In the application of the BASS model to aftershocks Deltam* is positive, the largest expected daughter event is smaller than the parent, and the sequence of events (aftershocks) usually dies out, but an exponential growth in the number of events with time is also possible. In this paper we explore this behavior of the BASS model as Deltam* varies, including when Deltam* is negative and the largest expected daughter event is larger than the parent. The applications of this self-similar branching process to biology and other fields are discussed.

  17. Can current New Madrid seismicity be explained as a decaying aftershock sequence?

    NASA Astrophysics Data System (ADS)

    Page, M. T.; Hough, S. E.; Felzer, K. R.

    2012-12-01

    It has been suggested that continuing seismicity in the New Madrid, central U.S. region is primarily composed of the continuing long-lived aftershock sequence of the 1811-1812 sequence, and thus cannot be taken as an indication of present-day strain accrual in the region. We examine historical and instrumental seismicity in the New Madrid region to determine if such a model is feasible given 1) the observed protracted nature of past New Madrid sequences, with multiple mainshocks with apparently similar magnitudes; 2) the rate of historically documented early aftershocks from the 1811-1812 sequence; and 3) plausible mainshock magnitudes and aftershock-productivity parameters. We use ETAS modeling to search for sub-critical sets of direct Omori parameters that are consistent with all of these datasets, given a realistic consideration of their uncertainties, and current seismicity in the region. The results of this work will help to determine whether or not future sequences are likely to be clusters of events like those in the past, a key issue for earthquake response planning.

  18. Explanation of temporal clustering of tsunami sources using the epidemic-type aftershock sequence model

    USGS Publications Warehouse

    Geist, Eric L.

    2014-01-01

    Temporal clustering of tsunami sources is examined in terms of a branching process model. It previously was observed that there are more short interevent times between consecutive tsunami sources than expected from a stationary Poisson process. The epidemic‐type aftershock sequence (ETAS) branching process model is fitted to tsunami catalog events, using the earthquake magnitude of the causative event from the Centennial and Global Centroid Moment Tensor (CMT) catalogs and tsunami sizes above a completeness level as a mark to indicate that a tsunami was generated. The ETAS parameters are estimated using the maximum‐likelihood method. The interevent distribution associated with the ETAS model provides a better fit to the data than the Poisson model or other temporal clustering models. When tsunamigenic conditions (magnitude threshold, submarine location, dip‐slip mechanism) are applied to the Global CMT catalog, ETAS parameters are obtained that are consistent with those estimated from the tsunami catalog. In particular, the dip‐slip condition appears to result in a near zero magnitude effect for triggered tsunami sources. The overall consistency between results from the tsunami catalog and that from the earthquake catalog under tsunamigenic conditions indicates that ETAS models based on seismicity can provide the structure for understanding patterns of tsunami source occurrence. The fractional rate of triggered tsunami sources on a global basis is approximately 14%.

  19. Characterization of Fault Networks and Diffusion of Aftershock Epicenters From Earthquake Catalogs: Fuzzy C-means Clustering and a Modified ETAS Model

    NASA Astrophysics Data System (ADS)

    Moulik, P.; Tiampo, K. F.

    2009-05-01

    The information on three-dimensional geometry as well as the identification of active fault segments is critical to our assessment of seismic risks. Numerical modeling of the aftershock locations, times and magnitudes are also crucial to characterize a fault zone. In this study, a pattern recognition technique based on the Fuzzy C- means clustering algorithm (Bezdek, 1981) is proposed to allow each earthquake to be associated with different fault segments. The spatial covariance tensor for each cluster and the associated earthquakes are used to find optimal anisotropic clusters and designate them as faults, similar to the OADC method (Ouillon et al., 2008). The location, size and orientation of the reconstructed faults segments are characterized using a fuzzy covariance matrix (Gustafson and Kessel, 1978). The output consists of a set of distinct fault segments along with the associated earthquakes at different fuzzy membership grades (Zadeh, 1965). A resultant matrix consists of the fuzzy membership grade for different earthquakes and corresponding faults segments specifying their degree of association with values from zero to one. The spatial distribution of earthquakes of different magnitudes and membership grades for a fault segment is incorporated in an anisotropic spatial kernel which characterizes the aftershock density at a distance vector in the ETAS model (Kagan and Knopoff, 1987; Ogata, 1988). An optimal spatio-temporal distribution of aftershocks is obtained for each fault segment without considering a priori distributions such as Gaussian or power law (Helmstetter et al., 2006; Helmstetter and Sornette, 2002). The model is tested on the aftershock sequence from the Denali, 2002 earthquake in Alaska and the fault reconstruction results compared with the known faults in the area. Therefore, a new method to incorporate the anisotropic nature of aftershock diffusion along with the reconstruction of fault networks from seismicity catalogs is formulated in

  20. Statistical signatures of aftershock sequences generated by supershear mainshocks

    NASA Astrophysics Data System (ADS)

    Bhattacharya, P.; Shcherbakov, R.; Tiampo, K. F.; Mansinha, L.

    2010-12-01

    The rupture process during supershear earthquakes generates a seismic shock wave redistributing stress away from the fault resembling a sonic boom produced by a supersonic aircraft. This leads to a relative quiescence in aftershock activity along the supershear segment of the rupture. The occurrence of supershear ruptures is also generally associated with a region of local high pre-stress and an unusually smooth friction profile over the supershear segment, leading to a conspicuous absence of high frequency ground motions. We have considered the aftershock sequences of five well-known supershear earthquakes from around the world (1979 Imperial Valley, 1992 Landers, 1999 Izmit and Duzce and 2002 Denali earthquakes) to test whether the aftershock statistics around the supershear rupture are different from the statistics in the rest of the region due to the aforementioned stress conditions and redistributions. Specifically, we have looked at the frequency-magnitude distribution in order to study the variation of the b value for each of the sequences and observe statistically significant variations. In particular, we have determined that the b value is always higher in the zone surrounding a supershear segment than in the rest of the aftershock region. The Omori Law, however, does not show such clear trends. We also looked at the average difference in magnitude between the mainshock and the largest aftershock and found it is larger than that predicted by Bath's law. The results certainly point towards a relationship between aftershock statistics and the mainshock rupture process and might facilitate a physical process based understanding of the empirical laws of earthquake statistics.

  1. Computational Software for Fitting Seismic Data to Epidemic-Type Aftershock Sequence Models

    NASA Astrophysics Data System (ADS)

    Chu, A.

    2014-12-01

    Modern earthquake catalogs are often analyzed using spatial-temporal point process models such as the epidemic-type aftershock sequence (ETAS) models of Ogata (1998). My work introduces software to implement two of ETAS models described in Ogata (1998). To find the Maximum-Likelihood Estimates (MLEs), my software provides estimates of the homogeneous background rate parameter and the temporal and spatial parameters that govern triggering effects by applying the Expectation-Maximization (EM) algorithm introduced in Veen and Schoenberg (2008). Despite other computer programs exist for similar data modeling purpose, using EM-algorithm has the benefits of stability and robustness (Veen and Schoenberg, 2008). Spatial shapes that are very long and narrow cause difficulties in optimization convergence and problems with flat or multi-modal log-likelihood functions encounter similar issues. My program uses a robust method to preset a parameter to overcome the non-convergence computational issue. In addition to model fitting, the software is equipped with useful tools for examining modeling fitting results, for example, visualization of estimated conditional intensity, and estimation of expected number of triggered aftershocks. A simulation generator is also given with flexible spatial shapes that may be defined by the user. This open-source software has a very simple user interface. The user may execute it on a local computer, and the program also has potential to be hosted online. Java language is used for the software's core computing part and an optional interface to the statistical package R is provided.

  2. Aftershocks triggered by fluid intrusion: Evidence for the aftershock sequence occurred 2014 in West Bohemia/Vogtland

    NASA Astrophysics Data System (ADS)

    Hainzl, S.; Fischer, T.; Čermáková, H.; Bachura, M.; Vlček, J.

    2016-04-01

    The West Bohemia/Vogtland region, central Europe, is well known for its repeating swarm activity. However, the latest activity in 2014, although spatially overlapping with previous swarm activity, consisted of three classical aftershock sequences triggered by ML3.5, 4.4, and 3.5 events. To decode the apparent system change from swarm-type to mainshock-aftershock characteristics, we have analyzed the details of the major ML4.4 sequence based on focal mechanisms and relocated earthquake data. Our analysis shows that the mainshock occurred with rotated mechanism in a step over region of the fault plane, unfavorably oriented to the regional stress field. Most of its intense aftershock activity occurred in-plane with classical characteristics such as (i) the maximum magnitude of the aftershocks is significantly less than the mainshock magnitude and (ii) the decay can be well fitted by the Omori-Utsu law. However, the absolute number of aftershocks and the fitted Omori-Utsu c and p parameters are much larger than for typical sequences. By means of the epidemic-type aftershock sequence model, we show that an additional aseismic source with an exponentially decaying strength triggered a large fraction of the aftershocks. Corresponding pore pressure simulations with an exponentially decreasing flow rate of the fluid source show a good agreement with the observed spatial migration front of the aftershocks extending approximately with log(t). Thus, we conclude that the mainshock opened fluid pathways from a finite fluid source into the fault plane explaining the unusual high rate of aftershocks, the migration patterns, and the exponential decrease of the aseismic signal.

  3. Sequence-based Parameter Estimation for an Epidemiological Temporal Aftershock Forecasting Model using Markov Chain Monte Carlo Simulation

    NASA Astrophysics Data System (ADS)

    Jalayer, Fatemeh; Ebrahimian, Hossein

    2014-05-01

    Introduction The first few days elapsed after the occurrence of a strong earthquake and in the presence of an ongoing aftershock sequence are quite critical for emergency decision-making purposes. Epidemic Type Aftershock Sequence (ETAS) models are used frequently for forecasting the spatio-temporal evolution of seismicity in the short-term (Ogata, 1988). The ETAS models are epidemic stochastic point process models in which every earthquake is a potential triggering event for subsequent earthquakes. The ETAS model parameters are usually calibrated a priori and based on a set of events that do not belong to the on-going seismic sequence (Marzocchi and Lombardi 2009). However, adaptive model parameter estimation, based on the events in the on-going sequence, may have several advantages such as, tuning the model to the specific sequence characteristics, and capturing possible variations in time of the model parameters. Simulation-based methods can be employed in order to provide a robust estimate for the spatio-temporal seismicity forecasts in a prescribed forecasting time interval (i.e., a day) within a post-main shock environment. This robust estimate takes into account the uncertainty in the model parameters expressed as the posterior joint probability distribution for the model parameters conditioned on the events that have already occurred (i.e., before the beginning of the forecasting interval) in the on-going seismic sequence. The Markov Chain Monte Carlo simulation scheme is used herein in order to sample directly from the posterior probability distribution for ETAS model parameters. Moreover, the sequence of events that is going to occur during the forecasting interval (and hence affecting the seismicity in an epidemic type model like ETAS) is also generated through a stochastic procedure. The procedure leads to two spatio-temporal outcomes: (1) the probability distribution for the forecasted number of events, and (2) the uncertainty in estimating the

  4. Short-term forecasting of aftershock sequences, microseismicity and swarms inside the Corinth Gulf continental rift

    NASA Astrophysics Data System (ADS)

    Segou, Margarita

    2014-05-01

    Corinth Gulf (Central Greece) is the fastest continental rift in the world with extension rates 11-15 mm/yr with diverse seismic deformation including earthquakes with M greater than 6.0, several periods of increased microseismic activity, usually lasting few months and possibly related with fluid diffusion, and swarm episodes lasting few days. In this study I perform a retrospective forecast experiment between 1995-2012, focusing on the comparison between physics-based and statistical models for short term time classes. Even though Corinth gulf has been studied extensively in the past there is still today a debate whether earthquake activity is related with the existence of either a shallow dipping structure or steeply dipping normal faults. In the light of the above statement, two CRS realization are based on resolving Coulomb stress changes on specified receiver faults, expressing the aforementioned structural models, whereas the third CRS model uses optimally-oriented for failure planes. The CRS implementation accounts for stress changes following all major ruptures with M greater than 4.5 within the testing phase. I also estimate fault constitutive parameters from modeling the response to major earthquakes at the vicinity of the gulf (Aσ=0.2, stressing rate app. 0.02 bar/yr). The generic ETAS parameters are taken as the maximum likelihood estimates derived from the stochastic declustering of the modern seismicity catalog (1995-2012) with minimum triggering magnitude M2.5. I test whether the generic ETAS can efficiently describe the aftershock spatio-temporal clustering but also the evolution of swarm episodes and microseismicity. For the reason above, I implement likelihood tests to evaluate the forecasts for their spatial consistency and for the total amount of predicted versus observed events with M greater than 3.0 in 10-day time windows during three distinct evaluation phases; the first evaluation phase focuses on the Aigio 1995 aftershock sequence (15

  5. A Variety of Aftershock Decays in the Rate- and State-Friction Model Due to the Effect of Secondary Aftershocks: Implications Derived from an Analysis of Real Aftershock Sequences

    NASA Astrophysics Data System (ADS)

    Iwata, Takaki

    2016-01-01

    The model based on rate- and state-dependent friction law reproduces the temporal decay of an aftershock sequence with the p value of the Omori-Utsu law equal to 1, if we simply assume a constant stress rate over time. However, because p values vary in real aftershock sequences, this model requires some modification. This study examined the effect of secondary aftershocks on the variety of the p value. A large aftershock causes a stepwise stress increase in the aftershock area, and the expected seismicity rate derived from the friction law also increases abruptly. These multiple increases in the seismicity rate during its decay following a mainshock could cause variation in the apparent p value. In this study, a model incorporating this idea is applied to two aftershock sequences observed in Japan and is shown to substantially modify the modeling of aftershock activity.

  6. Magnitude-dependent epidemic-type aftershock sequences model for earthquakes

    NASA Astrophysics Data System (ADS)

    Spassiani, Ilaria; Sebastiani, Giovanni

    2016-04-01

    We propose a version of the pure temporal epidemic type aftershock sequences (ETAS) model: the ETAS model with correlated magnitudes. As for the standard case, we assume the Gutenberg-Richter law to be the probability density for the magnitudes of the background events. Instead, the magnitude of the triggered shocks is assumed to be probabilistically dependent on that of the relative mother events. This probabilistic dependence is motivated by some recent works in the literature and by the results of a statistical analysis made on some seismic catalogs [Spassiani and Sebastiani, J. Geophys. Res. 121, 903 (2016), 10.1002/2015JB012398]. On the basis of the experimental evidences obtained in the latter paper for the real catalogs, we theoretically derive the probability density function for the magnitudes of the triggered shocks proposed in Spassiani and Sebastiani and there used for the analysis of two simulated catalogs. To this aim, we impose a fundamental condition: averaging over all the magnitudes of the mother events, we must obtain again the Gutenberg-Richter law. This ensures the validity of this law at any event's generation when ignoring past seismicity. The ETAS model with correlated magnitudes is then theoretically analyzed here. In particular, we use the tool of the probability generating function and the Palm theory, in order to derive an approximation of the probability of zero events in a small time interval and to interpret the results in terms of the interevent time between consecutive shocks, the latter being a very useful random variable in the assessment of seismic hazard.

  7. Magnitude-dependent epidemic-type aftershock sequences model for earthquakes.

    PubMed

    Spassiani, Ilaria; Sebastiani, Giovanni

    2016-04-01

    We propose a version of the pure temporal epidemic type aftershock sequences (ETAS) model: the ETAS model with correlated magnitudes. As for the standard case, we assume the Gutenberg-Richter law to be the probability density for the magnitudes of the background events. Instead, the magnitude of the triggered shocks is assumed to be probabilistically dependent on that of the relative mother events. This probabilistic dependence is motivated by some recent works in the literature and by the results of a statistical analysis made on some seismic catalogs [Spassiani and Sebastiani, J. Geophys. Res. 121, 903 (2016)10.1002/2015JB012398]. On the basis of the experimental evidences obtained in the latter paper for the real catalogs, we theoretically derive the probability density function for the magnitudes of the triggered shocks proposed in Spassiani and Sebastiani and there used for the analysis of two simulated catalogs. To this aim, we impose a fundamental condition: averaging over all the magnitudes of the mother events, we must obtain again the Gutenberg-Richter law. This ensures the validity of this law at any event's generation when ignoring past seismicity. The ETAS model with correlated magnitudes is then theoretically analyzed here. In particular, we use the tool of the probability generating function and the Palm theory, in order to derive an approximation of the probability of zero events in a small time interval and to interpret the results in terms of the interevent time between consecutive shocks, the latter being a very useful random variable in the assessment of seismic hazard.

  8. Magnitude-dependent epidemic-type aftershock sequences model for earthquakes.

    PubMed

    Spassiani, Ilaria; Sebastiani, Giovanni

    2016-04-01

    We propose a version of the pure temporal epidemic type aftershock sequences (ETAS) model: the ETAS model with correlated magnitudes. As for the standard case, we assume the Gutenberg-Richter law to be the probability density for the magnitudes of the background events. Instead, the magnitude of the triggered shocks is assumed to be probabilistically dependent on that of the relative mother events. This probabilistic dependence is motivated by some recent works in the literature and by the results of a statistical analysis made on some seismic catalogs [Spassiani and Sebastiani, J. Geophys. Res. 121, 903 (2016)10.1002/2015JB012398]. On the basis of the experimental evidences obtained in the latter paper for the real catalogs, we theoretically derive the probability density function for the magnitudes of the triggered shocks proposed in Spassiani and Sebastiani and there used for the analysis of two simulated catalogs. To this aim, we impose a fundamental condition: averaging over all the magnitudes of the mother events, we must obtain again the Gutenberg-Richter law. This ensures the validity of this law at any event's generation when ignoring past seismicity. The ETAS model with correlated magnitudes is then theoretically analyzed here. In particular, we use the tool of the probability generating function and the Palm theory, in order to derive an approximation of the probability of zero events in a small time interval and to interpret the results in terms of the interevent time between consecutive shocks, the latter being a very useful random variable in the assessment of seismic hazard. PMID:27176281

  9. Adaptive forecasting of aftershock activity after the main shock

    NASA Astrophysics Data System (ADS)

    Omi, Takahiro; Ogata, Yosihiko; Hirata, Yoshito; Aihara, Kazuyuki

    2014-05-01

    Forecasting aftershock activity is useful to reduce seismic risks in the affected area after the main shock. The difficulties to forecast aftershocks are (i) a forecasting model should be tailored to each aftershock sequence because the statistical property varies greatly according to an individual aftershock sequence and (ii) the forecasting model has to be estimated from highly deficient data where a significant fraction of early small aftershocks are missing from seismic records. To overcome this difficulty, we have been developing a statistical model to deal with incompletely detected aftershocks, in which the detection rate of aftershocks is sequentially estimated in a state-space modeling approach. Our method enables us to robustly estimate the forecasting model of underlying aftershocks including not only observed aftershocks but also missing ones from the incomplete catalog. We show that the Omori-Utsu formula can be well estimated only from a few hours of the data, and then it can be revised by the epidemic type aftershock sequence (ETAS) model to adaptively forecast an aftershock sequence with the individual cascading feature as the data size increases in real-time. We demonstrate that how these estimated models can effectively forecast the aftershock activity. We also discuss how these models can be implemented in an operational system for earthquake forecasting. References: T. Omi, Y. Ogata, Y. Hirata, and K. Aihiara, "Forecasting large aftershocks within one day after the main shock", Scientific Reports, 3, 2218 (2013). T. Omi, Y. Ogata, Y. Hirata, and K. Aihiara, "Estimating the ETAS model from an early aftershock sequence", (In submission).

  10. Anomalous power law distribution of total lifetimes of branching processes: Application to earthquake aftershock sequences

    SciTech Connect

    Saichev, A.; Sornette, D.

    2004-10-01

    We consider a general stochastic branching process, which is relevant to earthquakes, and study the distributions of global lifetimes of the branching processes. In the earthquake context, this amounts to the distribution of the total durations of aftershock sequences including aftershocks of arbitrary generation number. Our results extend previous results on the distribution of the total number of offspring (direct and indirect aftershocks in seismicity) and of the total number of generations before extinction. We consider a branching model of triggered seismicity, the epidemic-type aftershock sequence model, which assumes that each earthquake can trigger other earthquakes ('aftershocks'). An aftershock sequence results in this model from the cascade of aftershocks of each past earthquake. Due to the large fluctuations of the number of aftershocks triggered directly by any earthquake ('productivity' or 'fertility'), there is a large variability of the total number of aftershocks from one sequence to another, for the same mainshock magnitude. We study the regime where the distribution of fertilities {mu} is characterized by a power law {approx}1/{mu}{sup 1+{gamma}} and the bare Omori law for the memory of previous triggering mothers decays slowly as {approx}1/t{sup 1+{theta}}, with 0<{theta}<1 relevant for earthquakes. Using the tool of generating probability functions and a quasistatic approximation which is shown to be exact asymptotically for large durations, we show that the density distribution of total aftershock lifetimes scales as {approx}1/t{sup 1+{theta}}{sup sol{gamma}} when the average branching ratio is critical (n=1). The coefficient 1<{gamma}=b/{alpha}<2 quantifies the interplay between the exponent b{approx_equal}1 of the Gutenberg-Richter magnitude distribution {approx}10{sup -bm} and the increase {approx}10{sup {alpha}}{sup m} of the number of aftershocks with mainshock magnitude m (productivity), with 0.5<{alpha}<1. The renormalization of the

  11. Anomalous power law distribution of total lifetimes of branching processes: application to earthquake aftershock sequences.

    PubMed

    Saichev, A; Sornette, D

    2004-10-01

    We consider a general stochastic branching process, which is relevant to earthquakes, and study the distributions of global lifetimes of the branching processes. In the earthquake context, this amounts to the distribution of the total durations of aftershock sequences including aftershocks of arbitrary generation number. Our results extend previous results on the distribution of the total number of offspring (direct and indirect aftershocks in seismicity) and of the total number of generations before extinction. We consider a branching model of triggered seismicity, the epidemic-type aftershock sequence model, which assumes that each earthquake can trigger other earthquakes ("aftershocks"). An aftershock sequence results in this model from the cascade of aftershocks of each past earthquake. Due to the large fluctuations of the number of aftershocks triggered directly by any earthquake ("productivity" or "fertility"), there is a large variability of the total number of aftershocks from one sequence to another, for the same mainshock magnitude. We study the regime where the distribution of fertilities mu is characterized by a power law approximately 1/ mu(1+gamma) and the bare Omori law for the memory of previous triggering mothers decays slowly as approximately 1/ t(1+theta;) , with 0aftershock lifetimes scales as approximately 1/ t(1+theta;/gamma) when the average branching ratio is critical (n=1) . The coefficient 1aftershocks with mainshock magnitude m (productivity), with 0.5

  12. Three Ingredients for Improved Global Aftershock Forecasts: Tectonic Region, Time-Dependent Catalog Incompleteness, and Inter-Sequence Variability

    NASA Astrophysics Data System (ADS)

    Page, M. T.; Hardebeck, J.; Felzer, K. R.; Michael, A. J.; van der Elst, N.

    2015-12-01

    Following a large earthquake, seismic hazard can be orders of magnitude higher than the long-term average as a result of aftershock triggering. Due to this heightened hazard, there is a demand from emergency managers and the public for rapid, authoritative, and reliable aftershock forecasts. In the past, USGS aftershock forecasts following large, global earthquakes have been released on an ad-hoc basis with inconsistent methods, and in some cases, aftershock parameters adapted from California. To remedy this, we are currently developing an automated aftershock product that will generate more accurate forecasts based on the Reasenberg and Jones (Science, 1989) method. To better capture spatial variations in aftershock productivity and decay, we estimate regional aftershock parameters for sequences within the Garcia et al. (BSSA, 2012) tectonic regions. We find that regional variations for mean aftershock productivity exceed a factor of 10. The Reasenberg and Jones method combines modified-Omori aftershock decay, Utsu productivity scaling, and the Gutenberg-Richter magnitude distribution. We additionally account for a time-dependent magnitude of completeness following large events in the catalog. We generalize the Helmstetter et al. (2005) equation for short-term aftershock incompleteness and solve for incompleteness levels in the global NEIC catalog following large mainshocks. In addition to estimating average sequence parameters within regions, we quantify the inter-sequence parameter variability. This allows for a more complete quantification of the forecast uncertainties and Bayesian updating of the forecast as sequence-specific information becomes available.

  13. Discrete characteristics of the aftershock sequence of the 2011 Van earthquake

    NASA Astrophysics Data System (ADS)

    Toker, Mustafa

    2014-10-01

    An intraplate earthquake of magnitude Mw 7.2 occurred on a NE-SW trending blind oblique thrust fault in accretionary orogen, the Van region of Eastern Anatolia on October 23, 2011. The aftershock seismicity in the Van earthquake was not continuous but, rather, highly discrete. This shed light on the chaotic nonuniformity of the event distribution and played key roles in determining the seismic coupling between the rupturing process and seismogeneity. I analyzed the discrete statistical mechanics of the 2011 Van mainshock-aftershock sequence with an estimation of the non-dimensional tuning parameters consisting of; temporal clusters (C) and the random (RN) distribution of aftershocks, range of size scales (ROSS), strength change (εD), temperature (T), P-value of temporal decay, material parameter R-value, seismic coupling χ, and Q-value of aftershock distribution. I also investigated the frequency-size (FS), temporal (T) statistics and the sequential characteristics of aftershock dynamics using discrete approach and examined the discrete evolutionary periods of the Van earthquake Gutenberg-Richter (GR) distribution. My study revealed that the FS and T statistical properties of aftershock sequence represent the Gutenberg-Richter (GR) distribution, clustered (C) in time and random (RN) Poisson distribution, respectively. The overall statistical behavior of the aftershock sequence shows that the Van earthquake originated in a discrete structural framework with high seismic coupling under highly variable faulting conditions. My analyses relate this larger dip-slip event to a discrete seismogenesis with two main components of complex fracturing and branching framework of the ruptured fault and dynamic strengthening and hardening behavior of the earthquake. The results indicate two dynamic cases. The first is associated with aperiodic nature of aftershock distribution, indicating a time-independent Poissonian event. The second is associated with variable slip model

  14. Missing data in aftershock sequences: explaining the deviations from scaling laws.

    PubMed

    Lennartz, Sabine; Bunde, Armin; Turcotte, Donald L

    2008-10-01

    In this paper we extend the branching aftershock sequence model to study the role of missing data at short times and small amplitudes after a mainshock. We apply this model, which contains three parameters characterizing the missing data, to the magnitude and temporal statistics of four aftershock sequences in California. We find that the observed time-dependent deviations of the frequency-magnitude scaling from the Gutenberg-Richter power law dependency can be described quantitatively by the model. We also show that, for the same set of parameters, the model is able to explain quantitatively the observed magnitude-dependent deviations of the temporal decay of aftershocks from Omori's law. In addition, we show that the same sets of data can also reproduce quite well the various functional forms of the probability density functions of the return times between consecutive events with magnitudes above a prescribed threshold, as well as the violation of scaling at short and intermediate time scales.

  15. Scaling Analysis of Time Distribution between Successive Earthquakes in Aftershock Sequences

    NASA Astrophysics Data System (ADS)

    Marekova, Elisaveta

    2016-08-01

    The earthquake inter-event time distribution is studied, using catalogs for different recent aftershock sequences. For aftershock sequences following the Modified Omori's Formula (MOF) it seems clear that the inter-event distribution is a power law. The parameters of this law are defined and they prove to be higher than the calculated value (2 - 1/p). Based on the analysis of the catalogs, it is determined that the probability densities of the inter-event time distribution collapse into a single master curve when the data is rescaled with instantaneous intensity, R(t; Mth), defined by MOF. The curve is approximated by a gamma distribution. The collapse of the data provides a clear view of aftershock-occurrence self-similarity.

  16. Statistical monitoring of aftershock sequences: a case study of the 2015 Mw7.8 Gorkha, Nepal, earthquake

    NASA Astrophysics Data System (ADS)

    Ogata, Yosihiko; Tsuruoka, Hiroshi

    2016-03-01

    Early forecasting of aftershocks has become realistic and practical because of real-time detection of hypocenters. This study illustrates a statistical procedure for monitoring aftershock sequences to detect anomalies to increase the probability gain of a significantly large aftershock or even an earthquake larger than the main shock. In particular, a significant lowering (relative quiescence) in aftershock activity below the level predicted by the Omori-Utsu formula or the epidemic-type aftershock sequence model is sometimes followed by a large earthquake in a neighboring region. As an example, we detected significant lowering relative to the modeled rate after approximately 1.7 days after the main shock in the aftershock sequence of the Mw7.8 Gorkha, Nepal, earthquake of April 25, 2015. The relative quiescence lasted until the May 12, 2015, M7.3 Kodari earthquake that occurred at the eastern end of the primary aftershock zone. Space-time plots including the transformed time can indicate the local places where aftershock activity lowers (the seismicity shadow). Thus, the relative quiescence can be hypothesized to be related to stress shadowing caused by probable slow slips. In addition, the aftershock productivity of the M7.3 Kodari earthquake is approximately twice as large as that of the M7.8 main shock.

  17. Generalized Omori-Utsu law for aftershock sequences in southern California

    NASA Astrophysics Data System (ADS)

    Davidsen, J.; Gu, C.; Baiesi, M.

    2015-05-01

    We investigate the validity of a proposed generalized Omori-Utsu law for the aftershock sequences for the Landers, Hector Mine, Northridge and Superstition Hills earthquakes, the four largest events in the southern California catalogue we analyse. This law unifies three of the most prominent empirical laws of statistical seismology-the Gutenberg-Richter law, the Omori-Utsu law, and a generalized version of Båth's law-in a formula casting the parameters in the Omori-Utsu law as a function of the lower magnitude cutoff mc for the aftershocks considered. By applying a recently established general procedure for identifying aftershocks, we confirm that the generalized Omori-Utsu law provides a good approximation for the observed rates overall. In particular, we provide convincing evidence that the characteristic time c is not constant but a genuine function of mc, which cannot be attributed to short-term aftershock incompleteness. However, the estimation of the specific parameters is somewhat sensitive to the aftershock selection method used. This includes c(mc), which has important implications for inferring the underlying stress field.

  18. Spatial and temporal analysis of the Mw 7.7, 2007, Tocopilla aftershock sequence

    NASA Astrophysics Data System (ADS)

    Eggert, Silke; Sobiesiak, Monika

    2010-05-01

    On 14 November 2007, 15:40:51 UTC a large Mw 7.7 earthquake occurred in the region of Tocopilla in Northern Chile. The epicenter is located at 22.30°S, 69.89°W, ~ 35 km south east of the city of Tocopilla and 160 km north of Antofagasta (earthquake location by GEOFON network). The earthquake took place in the southern part of the Northern Chile seismic gap which is supposed to be at the end of its seismic cycle. Currently, the gap is spanning the rupture area of the Mw=9 1877 Iquique event, a region which is now unbroken for almost 150 years. Therefore, the 2007 Tocopilla earthquake is the first large event that occurred inside the Northern Chile seismic gap since 1877. We present a study of the spatial and temporal distribution of the aftershock activity following the 2007 Tocopilla event using the frequency-magnitude distribution and other parameters. Studying this aftershock sequence will provide closer insight into the fault dimension of this subduction zone earthquake and the tectonic setting of the region. The distribution of aftershocks into depth shows that the majority of the hypocenters are located along the subduction interface, reaching down to ~ 50 km depth. In the western part, the aftershock sequence splits into two branches, one heading towards the trench, the other bending into the crust in front of the Mejillones Peninsula. In the epicentral horizontal, we observe a concentration of aftershocks around the northern part of the Mejillones Peninsula and along the coast up to the Río Loa. This leads to the conclusion that the shallow part in the north west did probably not break during the event. The spatial density of aftershocks shows two offshore patches north-east of the peninsula. Analyzing the spatio-temporal distribution of our aftershock data set, we can see that the fault rupture propagated towards the south west with a fault plane of about 150 km length. These observations are consistent with first results by other studies. Our

  19. The Pegasus Bay aftershock sequence of the Mw 7.1 Darfield (Canterbury), New Zealand earthquake

    NASA Astrophysics Data System (ADS)

    Ristau, John; Holden, Caroline; Kaiser, Anna; Williams, Charles; Bannister, Stephen; Fry, Bill

    2013-10-01

    The Pegasus Bay aftershock sequence is the most recent aftershock sequence of the 2010 September 3 UTC moment magnitude (Mw) 7.1 Darfield earthquake in the Canterbury region of New Zealand. The Pegasus Bay aftershock sequence began on 2011 December 23 UTC with three events of Mw 5.4-5.9 located in the offshore region of Pegasus Bay, east of Christchurch city. We present a summary of key aspects of the sequence derived using various geophysical methods. Relocations carried out using double-difference tomography show a well-defined NNE-SSW to NE-SW series of aftershocks with most of the activity occurring at depths >5 km and an average depth of ˜10 km. Regional moment tensor solutions calculated for the Pegasus Bay sequence indicate that the vast majority (45 of 53 events) are reverse-faulting events with an average P-axis azimuth of 125°. Strong-motion data inversion favours a SE-dipping fault plane for the largest event (Mw 5.9) with a slip patch of 18 km × 15 km and a maximum slip of 0.8 m at 3.5 km depth. Peak ground accelerations ranging up to 0.98 g on the vertical component were recorded during the sequence, and the largest event produced horizontal accelerations of 0.2-0.4 g in the Christchurch central business district. Apparent stress estimates for the two largest events are 1.1 MPa (Mw 5.9) and 0.2 MPa (Mw 5.8), which are compatible with global averages, although lower than other large events in the Canterbury aftershock sequence. Coulomb stress analysis indicates that previous large earthquakes in the Canterbury sequence generate Coulomb stress increases for the two events only at relatively shallow depths (3-5 km). At greater depths, Coulomb stress decreases are predicted at the locations of the two events. The trend of the aftershocks is similar to mapped reverse faults north of Christchurch, and the high number of reverse-faulting mechanisms suggests that similar reverse-faulting structures are present in the offshore region east of Christchurch.

  20. DETERMINATION OF ELASTIC WAVE VELOCITY AND RELATIVE HYPOCENTER LOCATIONS USING REFRACTED WAVES. II. APPLICATION TO THE HAICHENG, CHINA, AFTERSHOCK SEQUENCE.

    USGS Publications Warehouse

    Shedlock, Kaye M.; Jones, Lucile M.; Ma, Xiufang

    1985-01-01

    The authors located the aftershocks of the February 4, 1975 Haicheng, China, aftershock sequence using an arrival time difference (ATD) simultaneous inversion method for determining the near-source (in situ) velocity and the location of the aftershocks with respect to a master event. The aftershocks define a diffuse zone, 70 km multiplied by 25 km, trending west-northwest, perpendicular to the major structural trend of the region. The main shock and most of the large aftershocks have strike-slip fault plane solutions. The preferred fault plane strikes west-northwest, and the inferred sense of motion is left-lateral. The entire Haicheng earthauake sequence appears to have been the response of an intensely faulted range boundary to a primarily east-west crustal compression and/or north-south extension.

  1. No evidence of magnitude clustering in an aftershock sequence of nano- and picoseismicity.

    PubMed

    Davidsen, Jörn; Kwiatek, Grzegorz; Dresen, Georg

    2012-01-20

    One of the hallmarks of our current understanding of seismicity as highlighted by the epidemic-type-aftershock sequence model is that the magnitudes of earthquakes are independent of one another and can be considered as randomly drawn from the Gutenberg-Richter distribution. This assumption forms the basis of many approaches for forecasting seismicity rates and hazard assessment. Recently, it has been suggested that the assumption of independent magnitudes is not valid. It was subsequently argued that this conclusion was not supported by the original earthquake data from California. One of the main challenges is the lack of completeness of earthquake catalogs. Here, we study an aftershock sequence of nano- and picoseismicity as observed at the Mponeng mine, for which the issue of incompleteness is much less pronounced. We show that this sequence does not exhibit any significant evidence of magnitude correlations.

  2. Three ingredients for Improved global aftershock forecasts: Tectonic region, time-dependent catalog incompleteness, and inter-sequence variability

    USGS Publications Warehouse

    Page, Morgan T.; Van Der Elst, Nicholas; Hardebeck, Jeanne L.; Felzer, Karen; Michael, Andrew J.

    2016-01-01

    Following a large earthquake, seismic hazard can be orders of magnitude higher than the long‐term average as a result of aftershock triggering. Because of this heightened hazard, emergency managers and the public demand rapid, authoritative, and reliable aftershock forecasts. In the past, U.S. Geological Survey (USGS) aftershock forecasts following large global earthquakes have been released on an ad hoc basis with inconsistent methods, and in some cases aftershock parameters adapted from California. To remedy this, the USGS is currently developing an automated aftershock product based on the Reasenberg and Jones (1989) method that will generate more accurate forecasts. To better capture spatial variations in aftershock productivity and decay, we estimate regional aftershock parameters for sequences within the García et al. (2012) tectonic regions. We find that regional variations for mean aftershock productivity reach almost a factor of 10. We also develop a method to account for the time‐dependent magnitude of completeness following large events in the catalog. In addition to estimating average sequence parameters within regions, we develop an inverse method to estimate the intersequence parameter variability. This allows for a more complete quantification of the forecast uncertainties and Bayesian updating of the forecast as sequence‐specific information becomes available.

  3. When and where the aftershock activity was depressed: Contrasting decay patterns of the proximate large earthquakes in southern California

    USGS Publications Warehouse

    Ogata, Y.; Jones, L.M.; Toda, S.

    2003-01-01

    Seismic quiescence has attracted attention as a possible precursor to a large earthquake. However, sensitive detection of quiescence requires accurate modeling of normal aftershock activity. We apply the epidemic-type aftershock sequence (ETAS) model that is a natural extension of the modified Omori formula for aftershock decay, allowing further clusters (secondary aftershocks) within an aftershock sequence. The Hector Mine aftershock activity has been normal, relative to the decay predicted by the ETAS model during the 14 months of available data. In contrast, although the aftershock sequence of the 1992 Landers earthquake (M = 7.3), including the 1992 Big Bear earthquake (M = 6.4) and its aftershocks, fits very well to the ETAS up until about 6 months after the main shock, the activity showed clear lowering relative to the modeled rate (relative quiescence) and lasted nearly 7 years, leading up to the Hector Mine earthquake (M = 7.1) in 1999. Specifically, the relative quiescence occurred only in the shallow aftershock activity, down to depths of 5-6 km. The sequence of deeper events showed clear, normal aftershock activity well fitted to the ETAS throughout the whole period. We argue several physical explanations for these results. Among them, we strongly suspect aseismic slips within the Hector Mine rupture source that could inhibit the crustal relaxation process within "shadow zones" of the Coulomb's failure stress change. Furthermore, the aftershock activity of the 1992 Joshua Tree earthquake (M = 6.1) sharply lowered in the same day of the main shock, which can be explained by a similar scenario.

  4. The aftershock sequence of the 2015 April 25 Gorkha-Nepal earthquake

    NASA Astrophysics Data System (ADS)

    Adhikari, L. B.; Gautam, U. P.; Koirala, B. P.; Bhattarai, M.; Kandel, T.; Gupta, R. M.; Timsina, C.; Maharjan, N.; Maharjan, K.; Dahal, T.; Hoste-Colomer, R.; Cano, Y.; Dandine, M.; Guilhem, A.; Merrer, S.; Roudil, P.; Bollinger, L.

    2015-12-01

    The M 7.8 2015 April 25 Gorkha earthquake devastated the mountainous southern rim of the High Himalayan range in central Nepal. The main shock was followed by 553 earthquakes of local magnitude greater than 4.0 within the first 45 days. In this study, we present and qualify the bulletin of the permanent National Seismological Centre network to determine the spatio-temporal distribution of the aftershocks. The Gorkha sequence defines a ˜140-km-long ESE trending structure, parallel to the mountain range, abutting on the presumed extension of the rupture plane of the 1934 M 8.4 earthquake. In addition, we observe a second seismicity belt located southward, under the Kathmandu basin and in the northern part of the Mahabarat range. Many aftershocks of the Gorkha earthquake sequence have been felt by the 3 millions inhabitants of the Kathmandu valley.

  5. Distribution of the largest event in the critical epidemic-type aftershock-sequence model

    NASA Astrophysics Data System (ADS)

    Vere-Jones, David; Zhuang, Jiancang

    2008-10-01

    This Brief Report corrects and extends the results of Zhuang and Ogata [Phys. Rev. E 73, 046134 (2006)] on the asymptotic behavior of the largest event in the epidemic-type aftershock-sequence model for earthquake occurrence. We show that, in the special case that the underlying branching process is critical, there exists a previously unnoticed mode of behavior, which occurs when the expected family size grows relatively slowly.

  6. Distribution of the largest event in the critical epidemic-type aftershock-sequence model.

    PubMed

    Vere-Jones, David; Zhuang, Jiancang

    2008-10-01

    This Brief Report corrects and extends the results of Zhuang and Ogata [Phys. Rev. E 73, 046134 (2006)] on the asymptotic behavior of the largest event in the epidemic-type aftershock-sequence model for earthquake occurrence. We show that, in the special case that the underlying branching process is critical, there exists a previously unnoticed mode of behavior, which occurs when the expected family size grows relatively slowly.

  7. The 2004-2005 Les Saintes (French West Indies) seismic aftershock sequence observed with ocean bottom seismometers

    NASA Astrophysics Data System (ADS)

    Bazin, S.; Feuillet, N.; Duclos, C.; Crawford, W.; Nercessian, A.; Bengoubou-Valérius, M.; Beauducel, F.; Singh, S. C.

    2010-06-01

    On November 21, 2004 an Mw6.3 intraplate earthquake occurred at sea in the French Caribbean. The aftershock sequence continues to this day and is the most extensive sequence in a French territory in more than a century. We recorded aftershocks from day 25 to day 66 of this sequence, using a rapidly-deployed temporary array of ocean bottom seismometers (OBS). We invert P- and S-wave arrivals for a tomographic velocity model and improve aftershock locations. The velocity model shows anomalies related to tectonic and geologic structures beneath the Les Saintes graben. 3D relocated aftershocks outline faults whose scarps were identified as active in recent high-resolution marine data. The aftershocks distribution suggests that both the main November 21 event and its principal aftershock, on February 14, 2005, ruptured Roseau fault, which is the largest of the graben, extending from Dominica Island to the Les Saintes archipelago. Aftershocks cluster in the lower part of the Roseau fault plane (between 8 and 12.6 km depth) that did not rupture during the main event. Shallower aftershocks occur in the Roseau fault footwall, probably along smaller antithetic faults. We calculate a strong negative Vp anomaly, between 4 and 8 km depth, within the graben, along the Roseau fault plane. This low Vp anomaly is associated with a high Vp/Vs ratio and may reflect a strongly fracturated body filled with fluids. We infer from several types of observation that fault lubrication is the driving mechanism for this long-lasting aftershock sequence.

  8. Can We Forecast 1-Month Span Aftershock Activity from the First Day Data after the Main Shock?

    NASA Astrophysics Data System (ADS)

    Omi, T.; Ogata, Y.; Hirata, Y.; Aihara, K.

    2014-12-01

    A large earthquake triggers persistent aftershock activity in and near the focal region. Thus, intermediate term forecasting of aftershocks at its earlier stage is important for mitigating seismic risks. A main difficulty for the early forecasting is the substantial incompleteness of early aftershock data. To deal with such incomplete data, we have developed a statistical model of the incomplete data, enabling us to obtain the immediate estimate of the forecasting models from incomplete data [1, 2]. Another difficulty for the intermediate term forecasting is that we have to determine the parameter values of the forecasting models with high accuracy, because even a small bias in the parameter values can lead to a significant bias of the forecasting in intermediate term. However such accurate estimation is quite difficult at the early stage, especially using the early and incomplete data. Here we present a Bayesian forecasting method by using the epidemic-type aftershock sequence (ETAS) model. The Bayesian forecasting considers not only the best parameter values such as the maximum likelihood estimates or maximum a posteriori estimates but also the estimation uncertainty of the parameter values. By analyzing aftershock sequences in Japan, we show the forecasting performances of the intermediate-term aftershocks can be significantly improved by considering the estimation uncertainty of the ETAS model [3]. Furthermore, we discuss the impact of the modeling of the magnitude frequency distribution of detected aftershocks within a day span on the forecasting of large aftershocks. [1] T. Omi, Y. Ogata, Y. Hirata and K. Aihara, "Forecasting large aftershocks within one day after the main shock", Scientific Reports 3, 2218 (2013). [2] T. Omi, Y. Ogata, Y. Hirata and K. Aihara, "Estimating the ETAS model from an early aftershock sequence", Geophysical Research Letters 41, 850 (2014). [3] T. Omi, Y. Ogata, Y. Hirata and K. Aihara, "Intermediate-term forecasting of aftershocks

  9. Long aftershock sequences within continents and implications for earthquake hazard assessment.

    PubMed

    Stein, Seth; Liu, Mian

    2009-11-01

    One of the most powerful features of plate tectonics is that the known plate motions give insight into both the locations and average recurrence interval of future large earthquakes on plate boundaries. Plate tectonics gives no insight, however, into where and when earthquakes will occur within plates, because the interiors of ideal plates should not deform. As a result, within plate interiors, assessments of earthquake hazards rely heavily on the assumption that the locations of small earthquakes shown by the short historical record reflect continuing deformation that will cause future large earthquakes. Here, however, we show that many of these recent earthquakes are probably aftershocks of large earthquakes that occurred hundreds of years ago. We present a simple model predicting that the length of aftershock sequences varies inversely with the rate at which faults are loaded. Aftershock sequences within the slowly deforming continents are predicted to be significantly longer than the decade typically observed at rapidly loaded plate boundaries. These predictions are in accord with observations. So the common practice of treating continental earthquakes as steady-state seismicity overestimates the hazard in presently active areas and underestimates it elsewhere. PMID:19890328

  10. Long aftershock sequences within continents and implications for earthquake hazard assessment.

    PubMed

    Stein, Seth; Liu, Mian

    2009-11-01

    One of the most powerful features of plate tectonics is that the known plate motions give insight into both the locations and average recurrence interval of future large earthquakes on plate boundaries. Plate tectonics gives no insight, however, into where and when earthquakes will occur within plates, because the interiors of ideal plates should not deform. As a result, within plate interiors, assessments of earthquake hazards rely heavily on the assumption that the locations of small earthquakes shown by the short historical record reflect continuing deformation that will cause future large earthquakes. Here, however, we show that many of these recent earthquakes are probably aftershocks of large earthquakes that occurred hundreds of years ago. We present a simple model predicting that the length of aftershock sequences varies inversely with the rate at which faults are loaded. Aftershock sequences within the slowly deforming continents are predicted to be significantly longer than the decade typically observed at rapidly loaded plate boundaries. These predictions are in accord with observations. So the common practice of treating continental earthquakes as steady-state seismicity overestimates the hazard in presently active areas and underestimates it elsewhere.

  11. Implications of mainshock-aftershocks interactions during the 2013 Ebreichsdorf sequence, Austria

    NASA Astrophysics Data System (ADS)

    Tary, Jean-Baptiste; Apoloner, Maria-Theresia; Bokelmann, Götz

    2015-04-01

    The Vienna basin is a pull-apart basin located at the contact between the Alpine arc and the Eurasian plate, with the Eastern Alps to the West, the Western Carpathian to the East, the Bohemian massif to the North, and the Pannonian basin to the South. The southern border of this basin, called the Vienna Basin Fault System (VBFS), is accommodating part of the extrusion of the Pannonian basin (~1-2 mm/yr) due to the convergence between the Adriatic microplate and the Eurasian plate. The VBFS is a sinistral strike-slip fault and one of the most active fault in Austria. Along the VBFS, the seismicity is mainly concentrated in separate clusters with a spacing of approximately 20 km. In 2000 and 2013, two sequences constituted by two main shocks and 20-30 aftershocks occurred in one of these clusters located close to Ebreichsdorf, approximately 30 km south of Vienna. We focus here on the sequence of 2013 whose earthquakes were relocated using the double-difference method. The two main shocks, with local magnitudes of 4.2 and very similar focal mechanisms (N63, sinistral strike-slip), seem to be almost collocated. The aftershocks are located mainly to the northwest and at shallower depths compared with the main shocks. In order to better understand the relationships between the two main shocks and their aftershocks, we use two simple models of Coulomb failure stress to investigate possible coseismic static stress transfer between the main shocks and the aftershocks: the constant apparent friction model and the isotropic poroelastic model. The Coulomb failure stress change at the location of most aftershocks is positive but under 0.01 MPa. Aftershock triggering due to coseismic static stress is then unlikely. On the other hand, two other mechanisms could drive this sequence i.e., rapid non-linear pore pressure diffusion along the fault plane or aseismic slip. Given inter-event distances and times of ~0.5-1 km and hours to days, respectively, a high hydraulic diffusivity of

  12. The Mw 8.1 2014 Iquique, Chile, seismic sequence: a tale of foreshocks and aftershocks

    NASA Astrophysics Data System (ADS)

    Cesca, S.; Grigoli, F.; Heimann, S.; Dahm, T.; Kriegerowski, M.; Sobiesiak, M.; Tassara, C.; Olcay, M.

    2016-03-01

    The 2014 April 1, Mw 8.1 Iquique (Chile) earthquake struck in the Northern Chile seismic gap. With a rupture length of less than 200 km, it left unbroken large segments of the former gap. Early studies were able to model the main rupture features but results are ambiguous with respect to the role of aseismic slip and left open questions on the remaining hazard at the Northern Chile gap. A striking observation of the 2014 earthquake has been its extensive preparation phase, with more than 1300 events with magnitude above ML 3, occurring during the 15 months preceding the main shock. Increasing seismicity rates and observed peak magnitudes accompanied the last three weeks before the main shock. Thanks to the large data sets of regional recordings, we assess the precursor activity, compare foreshocks and aftershocks and model rupture preparation and rupture effects. To tackle inversion challenges for moderate events with an asymmetric network geometry, we use full waveforms techniques to locate events, map the seismicity rate and derive source parameters, obtaining moment tensors for more than 300 events (magnitudes Mw 4.0-8.1) in the period 2013 January 1-2014 April 30. This unique data set of fore- and aftershocks is investigated to distinguish rupture process models and models of strain and stress rotation during an earthquake. Results indicate that the spatial distributions of foreshocks delineated the shallower part of the rupture areas of the main shock and its largest aftershock, well matching the spatial extension of the aftershocks cloud. Most moment tensors correspond to almost pure double couple thrust mechanisms, consistent with the slab orientation. Whereas no significant differences are observed among thrust mechanisms in different areas, nor among thrust foreshocks and aftershocks, the early aftershock sequence is characterized by the presence of normal fault mechanisms, striking parallel to the trench but dipping westward. These events likely occurred

  13. Automatic Classification of Extensive Aftershock Sequences Using Empirical Matched Field Processing

    NASA Astrophysics Data System (ADS)

    Gibbons, Steven J.; Harris, David B.; Kværna, Tormod; Dodge, Douglas A.

    2013-04-01

    The aftershock sequences that follow large earthquakes create considerable problems for data centers attempting to produce comprehensive event bulletins in near real-time. The greatly increased number of events which require processing can overwhelm analyst resources and reduce the capacity for analyzing events of monitoring interest. This exacerbates a potentially reduced detection capability at key stations, due the noise generated by the sequence, and a deterioration in the quality of the fully automatic preliminary event bulletins caused by the difficulty in associating the vast numbers of closely spaced arrivals over the network. Considerable success has been enjoyed by waveform correlation methods for the automatic identification of groups of events belonging to the same geographical source region, facilitating the more time-efficient analysis of event ensembles as opposed to individual events. There are, however, formidable challenges associated with the automation of correlation procedures. The signal generated by a very large earthquake seldom correlates well enough with the signals generated by far smaller aftershocks for a correlation detector to produce statistically significant triggers at the correct times. Correlation between events within clusters of aftershocks is significantly better, although the issues of when and how to initiate new pattern detectors are still being investigated. Empirical Matched Field Processing (EMFP) is a highly promising method for detecting event waveforms suitable as templates for correlation detectors. EMFP is a quasi-frequency-domain technique that calibrates the spatial structure of a wavefront crossing a seismic array in a collection of narrow frequency bands. The amplitude and phase weights that result are applied in a frequency-domain beamforming operation that compensates for scattering and refraction effects not properly modeled by plane-wave beams. It has been demonstrated to outperform waveform correlation as a

  14. Seismological aspects of the 27 June 2015 Gulf of Aqaba earthquake and its sequence of aftershocks

    NASA Astrophysics Data System (ADS)

    Abd el-aal, Abd el-aziz Khairy; Badreldin, Hazem

    2016-07-01

    On 27 June 2015, a moderate earthquake with magnitude Mb 5.2 struck the Gulf of Aqaba near Nuweiba City. This event was instrumentally recorded by the Egyptian National Seismic Network (ENSN) and many other international seismological centres. The event was felt in all the cities on the Gulf of Aqaba, as well as Suez City, Hurghada City, the greater Cairo Metropolitan Area, Israel, Jordan and the north-western part of Saudi Arabia. No casualties were reported, however. Approximately 95 aftershocks with magnitudes ranging from 0.7 to 4.2 were recorded by the ENSN following the mainshock. In the present study, the source characteristics of both the mainshock and the aftershocks were estimated using the near-source waveform data recorded by the very broadband stations of the ENSN, and these were validated by the P-wave polarity data from short period stations. Our analysis reveals that an estimated seismic moment of 0.762 × 1017 Nm was released, corresponding to a magnitude of Mw 5.2, a focal depth of 14 km, a fault radius of 0.72 km and a rupture area of approximately 1.65 km2. Monitoring the sequence of aftershocks reveals that they form a cluster around the mainshock and migrated downwards in focal depth towards the west. We compared the results we obtained with the published results from the international seismological centres. Our results are more realistic and accurate, in particular with respect to the epicenteral location, magnitude and fault plane solution which are in accordance with the hypocentre distribution of the aftershocks.

  15. An Autonomous System for Grouping Events in a Developing Aftershock Sequence

    SciTech Connect

    Harris, D. B.; Dodge, D. A.

    2011-03-22

    We describe a prototype detection framework that automatically clusters events in real time from a rapidly unfolding aftershock sequence. We use the fact that many aftershocks are repetitive, producing similar waveforms. By clustering events based on correlation measures of waveform similarity, the number of independent event instances that must be examined in detail by analysts may be reduced. Our system processes array data and acquires waveform templates with a short-term average (STA)/long-term average (LTA) detector operating on a beam directed at the P phases of the aftershock sequence. The templates are used to create correlation-type (subspace) detectors that sweep the subsequent data stream for occurrences of the same waveform pattern. Events are clustered by association with a particular detector. Hundreds of subspace detectors can run in this framework a hundred times faster than in real time. Nonetheless, to check the growth in the number of detectors, the framework pauses periodically and reclusters detections to reduce the number of event groups. These groups define new subspace detectors that replace the older generation of detectors. Because low-magnitude occurrences of a particular signal template may be missed by the STA/LTA detector, we advocate restarting the framework from the beginning of the sequence periodically to reprocess the entire data stream with the existing detectors. We tested the framework on 10 days of data from the Nevada Seismic Array (NVAR) covering the 2003 San Simeon earthquake. One hundred eighty-four automatically generated detectors produced 676 detections resulting in a potential reduction in analyst workload of up to 73%.

  16. Implications of spatial and temporal development of the aftershock sequence for the Mw 8.3 June 9, 1994 Deep Bolivian Earthquake

    NASA Astrophysics Data System (ADS)

    Myers, Stephen C.; Wallace, Terry C.; Beck, Susan L.; Silver, Paul G.; Zandt, George; Vandecar, John; Minaya, Estela

    On June 9, 1994 the Mw 8.3 Bolivia earthquake (636 km depth) occurred in a region which had not experienced significant, deep seismicity for at least 30 years. The mainshock and aftershocks were recorded in Bolivia on the BANJO and SEDA broadband seismic arrays and on the San Calixto Network. We used the joint hypocenter determination method to determine the relative location of the aftershocks. We have identified no foreshocks and 89 aftershocks (m > 2.2) for the 20-day period following the mainshock. The frequency of aftershock occurrence decreased rapidly, with only one or two aftershocks per day occuring after day two. The temporal decay of aftershock activity is similar to shallow aftershock sequences, but the number of aftershocks is two orders of magnitude less. Additionally, a mb ∼6, apparently triggered earthquake occurred just 10 minutes after the mainshock about 330 km east-southeast of the mainshock at a depth of 671 km. The aftershock sequence occurred north and east of the mainshock and extends to a depth of 665 km. The aftershocks define a slab striking N68°W and dipping 45°NE. The strike, dip, and location of the aftershock zone are consistent with this seismicity being confined within the downward extension of the subducted Nazca plate. The location and orientation of the aftershock sequence indicate that the subducted Nazca plate bends between the NNW striking zone of deep seismicity in western Brazil and the N-S striking zone of seismicity in central Bolivia. A tear in the deep slab is not necessitated by the data. A subset of the aftershock hypocenters cluster along a subhorizontal plane near the depth of the mainshock, favoring a horizontal fault plane. The horizontal dimensions of the mainshock [Beck et al., this issue; Silver et al., 1995] and slab defined by the aftershocks are approximately equal, indicating that the mainshock ruptured through the slab.

  17. Time-dependent Induced Seismicity Rates Described with an Epidemic Type Aftershock Sequence Model at The Geysers Geothermal Field, California

    NASA Astrophysics Data System (ADS)

    Johnson, C. W.; Totten, E. J.; Burgmann, R.

    2015-12-01

    To improve understanding of the link between injection/production activity and seismicity, we apply an Epidemic Type Aftershock Sequence (ETAS) model to an earthquake catalog from The Geysers geothermal field (GGF) between 2005-2015 using >140,000 events and Mc 0.8 . We partition the catalog along a northeast-southwest trending divide, which corresponds to regions of high and low levels of enhanced geothermal stimulation (EGS) across the field. The ETAS model is fit to the seismicity data using a 6-month sliding window with a 1-month time step to determine the background seismicity rate. We generate monthly time series of the time-dependent background seismicity rate in 1-km depth intervals from 0-5km. The average wellhead depth is 2-3 km and the background seismicity rates above this depth do not correlate well with field-wide injected masses over the time period of interest. The auto correlation results show a 12-month period for monthly time series proximal to the average wellhead depths (2-3km and 3-4km) for northwest GGF strongly correlates with field-wide fluid injection masses, with a four-month phase shift between the two depth intervals as fluid migrates deeper. This periodicity is not observed for the deeper depth interval of 4-5 km, where monthly background seismicity rates reduce to near zero. Cross-correlation analysis using the monthly time series for background seismicity rate and the field-wide injection, production and net injection (injection minus production) suggest that injection most directly modulates seismicity. Periodicity in the background seismicity is not observed as strongly in the time series for the southeast field. We suggest that the variation in background seismicity rate is a proxy for pore-pressure diffusion of injected fluids at depth. We deduce that the contrast between the background seismicity rates in the northwest and southeast GGF is a result of reduced EGS activity in the southeast region.

  18. The Hellenic Seismological Network Of Crete (HSNC): Validation and results of the 2013 aftershock sequences

    NASA Astrophysics Data System (ADS)

    Chatzopoulos, Georgios; Papadopoulos, Ilias; Vallianatos, Filippos

    2015-04-01

    The number and quality of seismological networks in Europe has increased in the past decades. Nevertheless, the need for localized networks monitoring areas of great seismic and scientific interest is constant. Hellenic Seismological Network of Crete (HSNC) covers this need for the vicinity of the South Aegean Sea and Crete Island. In the present work with the use of Z-map software (www.seismo.ethz.ch) the spatial variability of Magnitude of Completeness (Mc) is calculated from HSNC's manual analysis catalogue of events for the period 2011 until today, proving the good coverage of HSNC in the areas. Furthermore the 2013, South Aegean seismicity where two large shallow earthquakes occurred in the vicinity of Crete Island, is discussed. The first event takes place on 15th June 2013 in the front of the Hellenic Arc, south from central Crete, while the second one on 12th October, 2013 on the western part of Crete. The two main shocks and their aftershock sequences have been relocated with the use of hypoinverse earthquake location software and an appropriate crust model. The HSNC identified more than 500 and 300 aftershocks respectively followed after the main events. The detailed construction of aftershocks catalogue permits the applicability of modern theories based on complexity sciences as described recently in the frame of non extensive statistical physics. In addition site effects in the stations locations are presented using event and noise recordings. This work was implemented through the project IMPACT-ARC in the framework of action "ARCHIMEDES III-Support of Research Teams at TEI of Crete" (MIS380353) of the Operational Program "Education and Lifelong Learning" and is co-financed by the European Union (European Social Fund) and Greek national funds References A. Tzanis and F. Vallianatos, "Distributed power-law seismicity changes and crustal deformation in the EW Hellenic Arc", Natural Hazards and Earth Systems Sciences, 3, 179-195, 2003 F. Vallianatos, G

  19. Signature of Fault Healing in an Aftershock Sequence? The 2008 Wenchuan Earthquake

    NASA Astrophysics Data System (ADS)

    Zhang, Shengfeng; Wu, Zhongliang; Jiang, Changsheng

    2016-01-01

    We analyzed the aftershock sequence of the 2008 Wenchuan earthquake from May 12, 2008 to May 12, 2013 using the earthquake catalog of the China Earthquake Networks Center (CENC). In the analysis performed, we took under consideration the temporary variation in the completeness of the earthquake catalog just after the Wenchuan mainshock. The cutoff completeness magnitude from May 12 to June 27, 2008 was above 3.0 due to the impact of the earthquake sequence on the seismological observatory practice. It was observed that the b value has an increasing trend from June 27, 2008 to late April 2009, while since May 2009, the b value has remained stable. If these characteristics were associated with the possible signature of fault healing, the `apparent healing time' could be pinpointed by this measure as around 1 year. Due to two strong asperities present on the rupture of the Wenchuan mainshock, the aftershock zone can be divided into two segments, namely the north and the south segment. The b values of the two segments seem to show different trends of temporal variation. The main contribution of the increasing trend comes from the south segment, or the `initiation segment' of the main rupture.

  20. Mixture of a seismicity model based on the rate-and-state friction and ETAS model

    NASA Astrophysics Data System (ADS)

    Iwata, T.

    2015-12-01

    Currently the ETAS model [Ogata, 1988, JASA] is considered to be a standard model of seismicity. However, because the ETAS model is a purely statistical one, the physics-based seismicity model derived from the rate-and-state friction (hereafter referred to as Dieterich model) [Dieterich, 1994, JGR] is frequently examined. However, the original version of the Dieterich model has several problems in the application to real earthquake sequences and therefore modifications have been conducted in previous studies. Iwata [2015, Pageoph] is one of such studies and shows that the Dieterich model is significantly improved as a result of the inclusion of the effect of secondary aftershocks (i.e., aftershocks caused by previous aftershocks). However, still the performance of the ETAS model is superior to that of the improved Dieterich model. For further improvement, the mixture of the Dieterich and ETAS models is examined in this study. To achieve the mixture, the seismicity rate is represented as a sum of the ETAS and Dieterich models of which weights are given as k and 1-k, respectively. This mixture model is applied to the aftershock sequences of the 1995 Kobe and 2004 Mid-Niigata sequences which have been analyzed in Iwata [2015]. Additionally, the sequence of the Matsushiro earthquake swarm in central Japan 1965-1970 is also analyzed. The value of k and parameters of the ETAS and Dieterich models are estimated by means of the maximum likelihood method, and the model performances are assessed on the basis of AIC. For the two aftershock sequences, the AIC values of the ETAS model are around 3-9 smaller (i.e., better) than those of the mixture model. On the contrary, for the Matsushiro swarm, the AIC value of the mixture model is 5.8 smaller than that of the ETAS model, indicating that the mixture of the two models results in significant improvement of the seismicity model.

  1. Exploring the limits of waveform correlation event detection as applied to three earthquake aftershock sequences.

    SciTech Connect

    Resor, Megan E.; Carr, Dorthe Bame; Young, Christopher John

    2010-05-01

    Swarms of earthquakes and/or aftershock sequences can dramatically increase the level of seismicity in a region for a period of time lasting from days to months, depending on the swarm or sequence. Such occurrences can provide a large amount of useful information to seismologists. For those who monitor seismic events for possible nuclear explosions, however, these swarms/sequences are a nuisance. In an explosion monitoring system, each event must be treated as a possible nuclear test until it can be proven, to a high degree of confidence, not to be. Seismic events recorded by the same station with highly correlated waveforms almost certainly have a similar location and source type, so clusters of events within a swarm can quickly be identified as earthquakes. We have developed a number of tools that can be used to exploit the high degree of waveform similarity expected to be associated with swarms/sequences. Dendro Tool measures correlations between known events. The Waveform Correlation Detector is intended to act as a detector, finding events in raw data which correlate with known events. The Self Scanner is used to find all correlated segments within a raw data steam and does not require an event library. All three techniques together provide an opportunity to study the similarities of events in an aftershock sequence in different ways. To comprehensively characterize the benefits and limits of waveform correlation techniques, we studied 3 aftershock sequences, using our 3 tools, at multiple stations. We explored the effects of station distance and event magnitudes on correlation results. Lastly, we show the reduction in detection threshold and analyst workload offered by waveform correlation techniques compared to STA/LTA based detection. We analyzed 4 days of data from each aftershock sequence using all three methods. Most known events clustered in a similar manner across the toolsets. Up to 25% of catalogued events were found to be a member of a cluster. In

  2. Variation of b and p values from aftershocks sequences along the Mexican subduction zone and their relation to plate characteristics

    NASA Astrophysics Data System (ADS)

    Ávila-Barrientos, L.; Zúñiga, F. R.; Rodríguez-Pérez, Q.; Guzmán-Speziale, M.

    2015-11-01

    Aftershock sequences along the Mexican subduction margin (between coordinates 110ºW and 91ºW) were analyzed by means of the p value from the Omori-Utsu relation and the b value from the Gutenberg-Richter relation. We focused on recent medium to large (Mw > 5.6) events considered susceptible of generating aftershock sequences suitable for analysis. The main goal was to try to find a possible correlation between aftershock parameters and plate characteristics, such as displacement rate, age and segmentation. The subduction regime of Mexico is one of the most active regions of the world with a high frequency of occurrence of medium to large events and plate characteristics change along the subduction margin. Previous studies have observed differences in seismic source characteristics at the subduction regime, which may indicate a difference in rheology and possible segmentation. The results of the analysis of the aftershock sequences indicate a slight tendency for p values to decrease from west to east with increasing of plate age although a statistical significance is undermined by the small number of aftershocks in the sequences, a particular feature distinctive of the region as compared to other world subduction regimes. The b values show an opposite, increasing trend towards the east even though the statistical significance is not enough to warrant the validation of such a trend. A linear regression between both parameters provides additional support for the inverse relation. Moreover, we calculated the seismic coupling coefficient, showing a direct relation with the p and b values. While we cannot undoubtedly confirm the hypothesis that aftershock generation depends on certain tectonic characteristics (age, thickness, temperature), our results do not reject it thus encouraging further study into this question.

  3. The variability of PSV response spectra across a dense array deployed during the Northridge aftershock sequence

    USGS Publications Warehouse

    Field, E.H.; Hough, S.E.

    1997-01-01

    This study addresses the variability of pseudo-velocity response spectra across an array deployed on stiff soil in the San Fernando Valley during the Northridge (Mw 6.7) aftershock sequence. The separation between stations ranged from 0.5 to 5 km, and the aftershock magnitudes ranged from 2.3 to 4.0. We find that 95-percent of observed response spectra are within a factor of 1.9 to 2.6 of the network average. Statistically significant relative amplification factors were found for some of the sites, but the variability of observed response spectra is not significantly reduced by correcting for these effects. This implies that microzonation efforts on less than 5-km distance scales are not warranted at these types of sites. We also found a distance dependence for the response-spectral variability between neighboring sites. 95-percent are within a factor of ???2.3 at 0.5 km, increasing to 95-percent within a factor of ???4.2 at 5 km. No frequency dependence in these values could be resolved. Additional work is needed to examine the influence of other factors such as earthquake magnitude.

  4. Long aftershock sequences in North China and Central US: implications for hazard assessment in mid-continents

    NASA Astrophysics Data System (ADS)

    Liu, Mian; Luo, Gang; Wang, Hui; Stein, Seth

    2014-02-01

    Because seismic activity within mid-continents is usually much lower than that along plate boundary zones, even small earthquakes can cause widespread concerns, especially when these events occur in the source regions of previous large earthquakes. However, these small earthquakes may be just aftershocks that continue for decades or even longer. The recent seismicity in the Tangshan region in North China is likely aftershocks of the 1976 Great Tangshan earthquake. The current earthquake sequence in the New Madrid seismic zone in central United States, which includes a cluster of M ~ 7.0 events in 1811-1812 and a number of similar events in the past millennium, is believed to result from recent fault reactivation that releases pre-stored strain energy in the crust. If so, this earthquake sequence is similar to aftershocks in that the rates of energy release should decay with time and the sequence of earthquakes will eventually end. We use simple physical analysis and numerical simulations to show that the current sequence of large earthquakes in the New Madrid fault zone is likely ending or has ended. Recognizing that mid-continental earthquakes have long aftershock sequences and complex spatiotemporal occurrences are critical to improve hazard assessments.

  5. Estimation of the parameters of ETAS models by Simulated Annealing.

    PubMed

    Lombardi, Anna Maria

    2015-02-12

    This paper proposes a new algorithm to estimate the maximum likelihood parameters of an Epidemic Type Aftershock Sequences (ETAS) model. It is based on Simulated Annealing, a versatile method that solves problems of global optimization and ensures convergence to a global optimum. The procedure is tested on both simulated and real catalogs. The main conclusion is that the method performs poorly as the size of the catalog decreases because the effect of the correlation of the ETAS parameters is more significant. These results give new insights into the ETAS model and the efficiency of the maximum-likelihood method within this context.

  6. Estimation of the parameters of ETAS models by Simulated Annealing

    PubMed Central

    Lombardi, Anna Maria

    2015-01-01

    This paper proposes a new algorithm to estimate the maximum likelihood parameters of an Epidemic Type Aftershock Sequences (ETAS) model. It is based on Simulated Annealing, a versatile method that solves problems of global optimization and ensures convergence to a global optimum. The procedure is tested on both simulated and real catalogs. The main conclusion is that the method performs poorly as the size of the catalog decreases because the effect of the correlation of the ETAS parameters is more significant. These results give new insights into the ETAS model and the efficiency of the maximum-likelihood method within this context. PMID:25673036

  7. Applications of the predictability of the Coherent Noise Model to aftershock sequences

    NASA Astrophysics Data System (ADS)

    Christopoulos, Stavros-Richard; Sarlis, Nicholas

    2014-05-01

    A study [1] of the coherent noise model [2-4] in natural time [5-7] has shown that it exhibits predictability. Interestingly, one of the predictors suggested [1] for the coherent noise model can be generalized and applied to the case of (real) aftershock sequences. The results obtained [8] so far are beyond chance. Here, we apply this approach to several aftershock sequences of strong earthquakes with magnitudes Mw ≥6.9 in Indonesia, California and Greece, including the Mw9.2 earthquake that occurred on 26 December 2004 in Sumatra. References. [1] N. V. Sarlis and S.-R. G. Christopoulos, Predictability of the coherent-noise model and its applications, Physical Review E, 85, 051136, 2012. [2] M.E.J. Newman, Self-organized criticality, evolution and the fossil extinction record, Proc. R. Soc. London B, 263, 1605-1610, 1996. [3] M. E. J. Newman and K. Sneppen, Avalanches, scaling, and coherent noise, Phys. Rev. E, 54, 6226-6231, 1996. [4] K. Sneppen and M. Newman, Coherent noise, scale invariance and intermittency in large systems, Physica D, 110, 209 - 222. [5] P. Varotsos, N. Sarlis, and E. Skordas, Spatiotemporal complexity aspects on the interrelation between Seismic Electric Signals and seismicity, Practica of Athens Academy, 76, 294-321, 2001. [6] P.A. Varotsos, N.V. Sarlis, and E.S. Skordas, Long-range correlations in the electric signals that precede rupture, Phys. Rev. E, 66, 011902, 2002. [7] Varotsos P. A., Sarlis N. V. and Skordas E. S., Natural Time Analysis: The new view of time. Precursory Seismic Electric Signals, Earthquakes and other Complex Time-Series (Springer-Verlag, Berlin Heidelberg) 2011. [8] N. V. Sarlis and S.-R. G. Christopoulos, "Visualization of the significance of Receiver Operating Characteristics based on confidence ellipses", Computer Physics Communications, http://dx.doi.org/10.1016/j.cpc.2013.12.009

  8. Triggering of tsunamigenic aftershocks from large strike-slip earthquakes: Analysis of the November 2000 New Ireland earthquake sequence

    NASA Astrophysics Data System (ADS)

    Geist, Eric L.; Parsons, Tom

    2005-10-01

    The November 2000 New Ireland earthquake sequence started with a Mw = 8.0 left-lateral main shock on 16 November and was followed by a series of aftershocks with primarily thrust mechanisms. The earthquake sequence was associated with a locally damaging tsunami on the islands of New Ireland and nearby New Britain, Bougainville, and Buka. Results from numerical tsunami-propagation models of the main shock and two of the largest thrust aftershocks (Mw > 7.0) indicate that the largest tsunami was caused by an aftershock located near the southeastern termination of the main shock, off the southern tip of New Ireland (Aftershock 1). Numerical modeling and tide gauge records at regional and far-field distances indicate that the main shock also generated tsunami waves. Large horizontal displacements associated with the main shock in regions of steep bathymetry accentuated tsunami generation for this event. Most of the damage on Bougainville and Buka Islands was caused by focusing and amplification of tsunami energy from a ridge wave between the source region and these islands. Modeling of changes in the Coulomb failure stress field caused by the main shock indicate that Aftershock 1 was likely triggered by static stress changes, provided the fault was on or synthetic to the New Britain interplate thrust as specified by the Harvard CMT mechanism. For other possible focal mechanisms of Aftershock 1 and the regional occurrence of thrust aftershocks in general, evidence for static stress change triggering is not as clear. Other triggering mechanisms such as changes in dynamic stress may also have been important. The 2000 New Ireland earthquake sequence provides evidence that tsunamis caused by thrust aftershocks can be triggered by large strike-slip earthquakes. Similar tectonic regimes that include offshore accommodation structures near large strike-slip faults are found in southern California, the Sea of Marmara, Turkey, along the Queen Charlotte fault in British Columbia

  9. Inferring Aftershock Sequence Properties and Tectonic Structure Using Empirical Signal Detectors

    NASA Astrophysics Data System (ADS)

    Junek, William N.; Kværna, Tormod; Pirli, Myrto; Schweitzer, Johannes; Harris, David B.; Dodge, Douglas A.; Woods, Mark T.

    2015-02-01

    Seismotectonic studies of the 2008 Storfjorden aftershock sequence were limited to data acquired by the permanent, but sparse, regional seismic network in the Svalbard archipelago. Storfjorden's remote location and harsh polar environment inhibited deployment of temporary seismometers that would have improved observations of sequence events. The lack of good station coverage prevented the detection and computation of hypocenter locations of many low magnitude events (mb < 2.5) in the NORSAR analyst-reviewed bulletin. As a result, the fine structure of the sequence's space-time distribution was not captured. In this study, an autonomous event detection and clustering framework is employed to build a more complete catalog of Storfjorden events using data from the Spitsbergen (SPITS) array. The new catalog allows the spatiotemporal distribution of seismicity within the fjord to be studied in greater detail. Information regarding the location of active event clusters provides a means of inferring the tectonic structure within the fault zone. The distribution of active clusters and moment tensor solutions for the Storfjorden sequence suggests there are at least two different structures within the fjord: a NE-SW trending linear feature with oblique-normal to strike-slip faulting and E-W trending normal faults.

  10. Multiple event location analysis of aftershock sequences in the Pannonian basin

    NASA Astrophysics Data System (ADS)

    Bekesi, Eszter; Sule, Balint; Bondar, Istvan

    2016-04-01

    Accurate seismic event location is crucial to understand tectonic processes such as crustal faults that are most commonly investigated by studying seismic activity. Location errors can be significantly reduced using multiple event location methods. We applied the double difference method to relocate the earthquake occurred near Oroszlány and its 200 aftershocks to identify the geometry of the related fault. We used the extended ISC location algorithm, iLoc to determine the absolute single event locations for the Oroszlány aftershock sequence and applied double difference algorithm on the new hypocenters. To improve location precision, we added differential times from waveform cross-correlation to the multiple event location process to increase the accuracy of arrival time readings. We also tested the effect of various local 1-D velocity models on the results. We compared hypoDD results of bulletin and iLoc hypocenters to investigate the effect of initial hypocenter parameters on the relocation process. We show that hypoDD collapses the initial, rather diffuse locations into a smaller cluster and the vertical cross-sections show sharp images of seismicity. Unsurprisingly, the combined use of catalog and cross-correlation data sets provides the more accurate locations. Some of the relocated events in the cluster are ground truth quality with a location accuracy of 5 km or better. Having achieved accurate locations for the event cluster we are able to resolve the fault plane ambiguity in the moment tensor solutions and determine the accurate strike of the fault.

  11. Reduced Aftershock Productivity in Regions with Known Slow Slip Events

    NASA Astrophysics Data System (ADS)

    Collins, G.; Mina, A.; Richardson, E.; McGuire, J. J.

    2013-12-01

    Reduced aftershock activity has been observed in areas with high rates of aseismic slip, such as transform fault zones and some subduction zones. Fault conditions that could explain both of these observations include a low effective normal stress regime and/or a high temperature, semi-brittle/plastic rheology. To further investigate the possible connection between areas of aseismic slip and reduced aftershock productivity, we compared the mainshock-aftershock sequences in subduction zones where aseismic slip transients have been observed to those of adjacent (along-strike) regions where no slow slip events have been detected. Using the Advanced National Seismic System (ANSS) catalog, we counted aftershocks that occurred within 100 km and 14 days of 112 M>=5.0 slab earthquake mainshocks from January 1980 - July 2013, including 90 since January 2000, inside observed regions of detected slow slip: south central Alaska, Cascadia, the Nicoya Peninsula (Costa Rica), Guerrero (Mexico), and the North Island of New Zealand. We also compiled aftershock counts from 97 mainshocks from areas adjacent to each of these regions using the same criteria and over the same time interval. Preliminary analysis of these two datasets shows an aftershock triggering exponent (alpha in the ETAS model) of approximately 0.8, consistent with previous studies of aftershocks in a variety of tectonic settings. Aftershock productivity for both datasets is less than that of continental earthquakes. Contrasting the two datasets, aftershock productivity inside slow slip regions is lower than in adjacent areas along the same subduction zone and is comparable to that of mid-ocean ridge transform faults.

  12. On the adaptive daily forecasting of seismic aftershock hazard

    NASA Astrophysics Data System (ADS)

    Ebrahimian, Hossein; Jalayer, Fatemeh; Asprone, Domenico; Lombardi, Anna Maria; Marzocchi, Warner; Prota, Andrea; Manfredi, Gaetano

    2013-04-01

    Post-earthquake ground motion hazard assessment is a fundamental initial step towards time-dependent seismic risk assessment for buildings in a post main-shock environment. Therefore, operative forecasting of seismic aftershock hazard forms a viable support basis for decision-making regarding search and rescue, inspection, repair, and re-occupation in a post main-shock environment. Arguably, an adaptive procedure for integrating the aftershock occurrence rate together with suitable ground motion prediction relations is key to Probabilistic Seismic Aftershock Hazard Assessment (PSAHA). In the short-term, the seismic hazard may vary significantly (Jordan et al., 2011), particularly after the occurrence of a high magnitude earthquake. Hence, PSAHA requires a reliable model that is able to track the time evolution of the earthquake occurrence rates together with suitable ground motion prediction relations. This work focuses on providing adaptive daily forecasts of the mean daily rate of exceeding various spectral acceleration values (the aftershock hazard). Two well-established earthquake occurrence models suitable for daily seismicity forecasts associated with the evolution of an aftershock sequence, namely, the modified Omori's aftershock model and the Epidemic Type Aftershock Sequence (ETAS) are adopted. The parameters of the modified Omori model are updated on a daily basis using Bayesian updating and based on the data provided by the ongoing aftershock sequence based on the methodology originally proposed by Jalayer et al. (2011). The Bayesian updating is used also to provide sequence-based parameter estimates for a given ground motion prediction model, i.e. the aftershock events in an ongoing sequence are exploited in order to update in an adaptive manner the parameters of an existing ground motion prediction model. As a numerical example, the mean daily rates of exceeding specific spectral acceleration values are estimated adaptively for the L'Aquila 2009

  13. Nucleotide sequences of immunoglobulin eta genes of chimpanzee and orangutan: DNA molecular clock and hominoid evolution

    SciTech Connect

    Sakoyama, Y.; Hong, K.J.; Byun, S.M.; Hisajima, H.; Ueda, S.; Yaoita, Y.; Hayashida, H.; Miyata, T.; Honjo, T.

    1987-02-01

    To determine the phylogenetic relationships among hominoids and the dates of their divergence, the complete nucleotide sequences of the constant region of the immunoglobulin eta-chain (C/sub eta1/) genes from chimpanzee and orangutan have been determined. These sequences were compared with the human eta-chain constant-region sequence. A molecular clock (silent molecular clock), measured by the degree of sequence divergence at the synonymous (silent) positions of protein-encoding regions, was introduced for the present study. From the comparison of nucleotide sequences of ..cap alpha../sub 1/-antitrypsin and ..beta..- and delta-globulin genes between humans and Old World monkeys, the silent molecular clock was calibrated: the mean evolutionary rate of silent substitution was determined to be 1.56 x 10/sup -9/ substitutions per site per year. Using the silent molecular clock, the mean divergence dates of chimpanzee and orangutan from the human lineage were estimated as 6.4 +/- 2.6 million years and 17.3 +/- 4.5 million years, respectively. It was also shown that the evolutionary rate of primate genes is considerably slower than those of other mammalian genes.

  14. The 25 March 1993 Scotts Mills, Oregon, earthquake and aftershock sequence: Spatial distribution, focal mechanisms, and the mount angel fault

    USGS Publications Warehouse

    Thomas, G.C.; Crosson, R.S.; Carver, D.L.; Yelin, T.S.

    1996-01-01

    The 25 March 1993 ML = 5.7 crustal earthquake near Scotts Mills, Oregon, was the largest earthquake to occur in the Pacific Northwest in over a decade. The mainshock was located at 45.033?? N, 122.586?? W and at a depth of about 15.1 km, based on arrival time data from the short-period Pacific Northwest Seismograph Network. Beginning about 12 h after the mainshock, investigators from the U.S. Geological Survey deployed 22 digital seismographs to record aftershocks. Using data from the temporary and permanent stations, we analyzed a subset of 50 after-shocks with quality locations. Hypocenters of these aftershocks lie on a northwesttrending steeply dipping plane (strike 290 ?? 10??, dipping 60 ?? 5?? to the north-northeast), in agreement with the preferred slip plane of the mainshock focal mechanism solution (strike 294??, dipping 58?? to the north-northeast). The planar structure defined by the aftershock locations may be a southeast continuation of the Mount Angel Fault, a reverse fault identified from both surface and subsurface evidence. The mapped southeast extent of the Mount Angel Fault is located less than 10 km west of the Scotts Mills epicentral region. In addition, the mainshock focal mechanism solution, with a combination of reverse motion and right-lateral strike slip, has a geometry and sense of motion consistent with the Mount Angel Fault. While aftershock focal mechanisms are varied, P axes are consistently oriented in a subhorizontal north-south direction. This earthquake sequence, together with the geological and geophysical evidence for the Mount Angel Fault, suggests a significant crustal earthquake hazard for this region of northwest Oregon.

  15. The Hellenic Seismological Network of Crete (HSNC): validation and results of the 2013 aftershock sequences

    NASA Astrophysics Data System (ADS)

    Chatzopoulos, G.; Papadopoulos, I.; Vallianatos, F.

    2016-02-01

    The last century, the global urbanization has leaded the majority of population to move into big, metropolitan areas. Small areas on the Earth's surface are being built with tall buildings in areas close to seismogenic zones. Such an area of great importance is the Hellenic arc in Greece. Among the regions with high seismicity is Crete, located on the subduction zone of the Eastern Mediterranean plate underneath the Aegean plate. The Hellenic Seismological Network of Crete (HSNC) has been built to cover the need on continuous monitoring of the regional seismicity in the vicinity of the South Aegean Sea and Crete Island. In the present work, with the use of Z-map software the spatial variability of Magnitude of Completeness (Mc) is calculated from HSNC's manual analysis catalogue of events from the beginning of 2008 till the end of September 2015, supporting the good coverage of HSNC in the area surrounding Crete Island. Furthermore, we discuss the 2013 seismicity when two large earthquakes occurred in the vicinity of Crete Island. The two main shocks and their aftershock sequences have been relocated with the use of HYPOINVERSE earthquake location software. Finally, the quality of seismological stations is addressed using the standard PQLX software.

  16. The M 7.7 Tocopilla earthquake and its aftershock sequence: deployment of a Task Force local network

    NASA Astrophysics Data System (ADS)

    Sobiesiak, M.; Eggert, S.; Woith, H.; Grosser, H.; Peyrat, S.; Vilotte, J.; Medina, E.; Ruch, J.; Walter, T.; Victor, P.; Barrientos, S.; Gonzalez, G.

    2008-05-01

    After the November 14, 2007 Tocopilla earthquake in northern Chile, a local network of 20 short period seismic stations, 5 strong motion instruments, 6 GPS stations and 3 extensometers has been installed in the fault plane area between Tocopilla and Antofagasta by the German Task Force for earthquakes (GFZ Potsdam). The hydrogeology group of the TF sampled 20 thermal water sources in the area of the El Tatio geyser field, located about 170 km E of the epicentre. In collaboration with the IPG Paris, 4 broad band stations were deployed at the northern end of the fault plane between Tocopilla and Maria Elena. Major targets of the investigations of the aftershock sequence are the segment boundary between the 1995 Antofagasta earthquake and the recent Tocopilla event, stress transfer between both successively ruptured subduction zone segments, structural properties of the fault plane, possible consequences for the northern adjacent Iquique segment, and the influence of earthquake seismic waves on the El Tatio hydrothermal field. In our presentation we would like to show first results on the spatial distribution of the aftershocks and discuss these in relation to studies we have made on the Antofagasta aftershock sequence.

  17. Application of Subspace Detection to the 6 November 2011 M5.6 Prague, Oklahoma Aftershock Sequence

    NASA Astrophysics Data System (ADS)

    McMahon, N. D.; Benz, H.; Johnson, C. E.; Aster, R. C.; McNamara, D. E.

    2015-12-01

    Subspace detection is a powerful tool for the identification of small seismic events. Subspace detectors improve upon single-event matched filtering techniques by using multiple orthogonal waveform templates whose linear combinations characterize a range of observed signals from previously identified earthquakes. Subspace detectors running on multiple stations can significantly increasing the number of locatable events, lowering the catalog's magnitude of completeness and thus providing extraordinary detail on the kinematics of the aftershock process. The 6 November 2011 M5.6 earthquake near Prague, Oklahoma is the largest earthquake instrumentally recorded in Oklahoma history and the largest earthquake resultant from deep wastewater injection. A M4.8 foreshock on 5 November 2011 and the M5.6 mainshock triggered tens of thousands of detectable aftershocks along a 20 km splay of the Wilzetta Fault Zone known as the Meeker-Prague fault. In response to this unprecedented earthquake, 21 temporary seismic stations were deployed surrounding the seismic activity. We utilized a catalog of 767 previously located aftershocks to construct subspace detectors for the 21 temporary and 10 closest permanent seismic stations. Subspace detection identified more than 500,000 new arrival-time observations, which associated into more than 20,000 locatable earthquakes. The associated earthquakes were relocated using the Bayesloc multiple-event locator, resulting in ~7,000 earthquakes with hypocentral uncertainties of less than 500 m. The relocated seismicity provides unique insight into the spatio-temporal evolution of the aftershock sequence along the Wilzetta Fault Zone and its associated structures. We find that the crystalline basement and overlying sedimentary Arbuckle formation accommodate the majority of aftershocks. While we observe aftershocks along the entire 20 km length of the Meeker-Prague fault, the vast majority of earthquakes were confined to a 9 km wide by 9 km deep

  18. Spatial stress variations in the aftershock sequence following the 2008 M6 earthquake doublet in the South Iceland Seismic Zone

    NASA Astrophysics Data System (ADS)

    Hensch, M.; Árnadóttir, Th.; Lund, B.; Brandsdóttir, B.

    2012-04-01

    The South Iceland Seismic Zone (SISZ) is an approximately 80 km wide E-W transform zone, bridging the offset between the Eastern Volcanic Zone and the Hengill triple junction to the west. The plate motion is accommodated in the brittle crust by faulting on many N-S trending right-lateral strike-slip faults of 2-5 km separation. Major sequences of large earthquakes (M>6) has occurred repeatedly in the SISZ since the settlement in Iceland more than thousand years ago. On 29th May 2008, two M6 earthquakes hit the western part of the SISZ on two adjacent N-S faults within a few seconds. The intense aftershock sequence was recorded by the permanent Icelandic SIL network and a promptly installed temporary network of 11 portable seismometers in the source region. The network located thousands of aftershocks during the following days, illuminating a 12-17 km long region along both major fault ruptures as well as several smaller parallel faults along a diffuse E-W trending region west of the mainshock area without any preceding main rupture. This episode is suggested to be the continuation of an earthquake sequence which started with two M6.5 and several M5-6 events in June 2000. The time delay between the 2000 and 2008 events could be due to an inflation episode in Hengill during 1993-1998, that potentially locked N-S strike slip faults in the western part of the SISZ. Around 300 focal solutions for aftershocks have been derived by analyzing P-wave polarities, showing predominantly strike-slip movements with occasional normal faulting components (unstable P-axis direction), which suggests an extensional stress regime as their driving force. A subsequent stress inversion of four different aftershock clusters reveals slight variations of the directions of the average σ3 axes. While for both southern clusters, including the E-W cluster, the σ3 axes are rather elongated perpendicular to the overall plate spreading axis, they are more northerly trending for shallower clusters

  19. Aftershocks of the june 20, 1978, Greece earthquake: A multimode faulting sequence

    USGS Publications Warehouse

    Carver, D.; Bollinger, G.A.

    1981-01-01

    A 10-station portable seismograph network was deployed in northern Greece to study aftershocks of the magnitude (mb) 6.4 earthquake of June 20, 1978. The main shock occurred (in a graben) about 25 km northeast of the city of Thessaloniki and caused an east-west zone of surface rupturing 14 km long that splayed to 7 km wide at the west end. The hypocenters for 116 aftershocks in the magnitude range from 2.5 to 4.5 were determined. The epicenters for these events cover an area 30 km (east-west) by 18 km (north-south), and focal depths ranges from 4 to 12 km. Most of the aftershocks in the east half of the aftershock zone are north of the surface rupture and north of the graben. Those in the west half are located within the boundaries of the graben. Composite focalmechanism solutions for selected aftershocks indicate reactivation of geologically mapped normal faults in the area. Also, strike-slip and dip-slip faults that splay off the western end of the zone of surface ruptures may have been activated. The epicenters for four large (M ??? 4.8) foreshocks and the main shock were relocated using the method of joint epicenter determination. Collectively, those five epicenters form an arcuate pattern convex southward, that is north of and 5 km distant from the surface rupturing. The 5-km separation, along with a focal depth of 8 km (average aftershock depth) or 16 km (NEIS main-shock depth), implies that the fault plane dips northward 58?? or 73??, respectively. A preferred nodal-plane dip of 36?? was determined by B.C. Papazachos and his colleagues in 1979 from a focal-mechanism solution for the main shock. If this dip is valid for the causal fault and that fault projects to the zone of surface rupturing, a decrease of dip with depth is required. ?? 1981.

  20. Detailed velocity ratio mapping during the aftershock sequence as a tool to monitor the fluid activity within the fault plane

    NASA Astrophysics Data System (ADS)

    Bachura, Martin; Fischer, Tomáš

    2016-11-01

    The rheological properties of Earth materials are expressed by their seismic velocities and VP /VS ratio, which is easily obtained by the Wadati method. Its double-difference version based on cross-correlated waveforms enables focusing on very local structures and allows tracking, monitoring and analysing the fluid activity along faults. We applied the method to three 2014 mainshock-aftershock sequences in the West Bohemia/Vogtland (Czech Republic) earthquake swarm area and found pronounced VP /VS variations in time and space for different clusters of events located on a steeply dipping fault zone at depths ranging from 7 to 11 km. Each cluster reflects the spatial distribution of earthquakes along the fault plane but also the temporal evolution of the activity. Low values of VP /VS ratio down to 1.59 ± 0.02 were identified in the deeper part of the fault zone whereas higher values up to 1.73 ± 0.01 were estimated for clusters located on a shallower segment of the fault. Temporally the low VP /VS values are associated with the early aftershocks, while the higher VP /VS ratios are related only to later aftershocks. We interpret this behaviour as a result of saturation of the focal zone by compressible fluids: in the beginning the mainshock and early aftershocks driven by over-pressured fluids increased the porosity due to opening the fluid pathways. This process was associated with a decrease of the velocity ratio. In later stages the pressure and porosity decreased and the velocity ratio recovered to levels of 1.73, typical for a Poissonian medium and Earth's crust.

  1. Cumulative Coulomb Stress Triggering as an Explanation for the Canterbury (New Zealand) Aftershock Sequence: Initial Conditions Are Everything?

    NASA Astrophysics Data System (ADS)

    Bebbington, Mark; Harte, David; Williams, Charles

    2016-01-01

    Using 2 years of aftershock data and three fault-plane solutions for each of the initial M7.1 Darfield earthquake and the larger (M >6) aftershocks, we conduct a detailed examination of Coulomb stress transfer in the Canterbury 2010-2011 earthquake sequence. Moment tensor solutions exist for 283 of the events with M ≥ 3.6, while 713 other events of M ≥ 3.6 have only hypocentre and magnitude information available. We look at various methods for deciding between the two possible mechanisms for the 283 events with moment tensor solutions, including conformation to observed surface faulting, and maximum ΔCFF transfer from the Darfield main shock. For the remaining events, imputation methods for the mechanism including nearest-neighbour, kernel smoothing, and optimal plane methods are considered. Fault length, width, and depth are arrived at via a suite of scaling relations. A large (50-70 %) proportion of the faults considered were calculated to have initial loading in excess of the final stress drop. The majority of faults that accumulated positive ΔCFF during the sequence were `encouraged' by the main shock failure, but, on the other hand, of the faults that failed during the sequence, more than 50 % of faults appeared to have accumulated a negative ΔCFF from all preceding failures during the sequence. These results were qualitatively insensitive to any of the factors considered. We conclude that there is much unknown about how Coulomb stress triggering works in practice.

  2. The 2012 August 11 MW 6.5, 6.4 Ahar-Varzghan earthquakes, NW Iran: aftershock sequence analysis and evidence for activity migration

    NASA Astrophysics Data System (ADS)

    Rezapour, Mehdi

    2016-02-01

    The Ahar-Varzghan doublet earthquakes with magnitudes MW 6.5 and 6.4 occurred on 2012 August 11 in northwest Iran and were followed by many aftershocks. In this paper, we analyse ˜5 months of aftershocks of these events. The Ahar-Varzghan earthquakes occurred along complex faults and provide a new constraint on the earthquake hazard in northwest Iran. The general pattern of relocated aftershocks defines a complex seismic zone covering an area of approximately 25 × 10 km2. The Ahar-Varzghan aftershock sequence shows a secondary activity which started on November 7, approximately 3 months after the main shocks, with a significant increase in activity, regarding both number of events and their magnitude. This stage was characterized by a seismic zone that propagated to the west of the main shocks. The catalogue of aftershocks for the doublet earthquake has a magnitude completeness of Mc 2.0. A below-average b-value for the Ahar-Varzghan sequence indicates a structural heterogeneity in the fault plane and the compressive stress state of the region. Relocated aftershocks occupy a broad zone clustering east-west with near-vertical dip which we interpret as the fault plane of the first of the doublet main shocks (MW 6.5). The dominant depth range of the aftershocks is from 3 to about 20 km, and the focal depths decrease toward the western part of the fault. The aftershock activity has its highest concentration in the eastern and middle parts of the active fault, and tapers off toward the western part of the active fault segment, indicating mainly a unilateral rupture toward west.

  3. A case study of two M~5 mainshocks in Anza, California: Is the footprint of an aftershock sequence larger than we think?

    USGS Publications Warehouse

    Fritts, Karen R.; Kilb, Debi

    2009-01-01

    It has been traditionally held that aftershocks occur within one to two fault lengths of the mainshock. Here we demonstrate that this perception has been shaped by the sensitivity of seismic networks. The 31 October 2001 Mw 5.0 and 12 June 2005 Mw 5.2 Anza mainshocks in southern California occurred in the middle of the densely instrumented ANZA seismic network and thus were unusually well recorded. For the June 2005 event, aftershocks as small as M 0.0 could be observed stretching for at least 50 km along the San Jacinto fault even though the mainshock fault was only ∼4.5 km long. It was hypothesized that an observed aseismic slipping patch produced a spatially extended aftershock-triggering source, presumably slowing the decay of aftershock density with distance and leading to a broader aftershock zone. We find, however, the decay of aftershock density with distance for both Anza sequences to be similar to that observed elsewhere in California. This indicates there is no need for an additional triggering mechanism and suggests that given widespread dense instrumentation, aftershock sequences would routinely have footprints much larger than currently expected. Despite the large 2005 aftershock zone, we find that the probability that the 2005 Anza mainshock triggered the M 4.9 Yucaipa mainshock, which occurred 4.2 days later and 72 km away, to be only 14%±1%. This probability is a strong function of the time delay; had the earthquakes been separated by only an hour, the probability of triggering would have been 89%.

  4. Anomalous stress diffusion, Omori's law and Continuous Time Random Walk in the 2010 Efpalion aftershock sequence (Corinth rift, Greece)

    NASA Astrophysics Data System (ADS)

    Michas, Georgios; Vallianatos, Filippos; Karakostas, Vassilios; Papadimitriou, Eleftheria; Sammonds, Peter

    2014-05-01

    Efpalion aftershock sequence occurred in January 2010, when an M=5.5 earthquake was followed four days later by another strong event (M=5.4) and numerous aftershocks (Karakostas et al., 2012). This activity interrupted a 15 years period of low to moderate earthquake occurrence in Corinth rift, where the last major event was the 1995 Aigion earthquake (M=6.2). Coulomb stress analysis performed in previous studies (Karakostas et al., 2012; Sokos et al., 2012; Ganas et al., 2013) indicated that the second major event and most of the aftershocks were triggered due to stress transfer. The aftershocks production rate decays as a power-law with time according to the modified Omori law (Utsu et al., 1995) with an exponent larger than one for the first four days, while after the occurrence of the second strong event the exponent turns to unity. We consider the earthquake sequence as a point process in time and space and study its spatiotemporal evolution considering a Continuous Time Random Walk (CTRW) model with a joint probability density function of inter-event times and jumps between the successive earthquakes (Metzler and Klafter, 2000). Jump length distribution exhibits finite variance, whereas inter-event times scale as a q-generalized gamma distribution (Michas et al., 2013) with a long power-law tail. These properties are indicative of a subdiffusive process in terms of CTRW. Additionally, the mean square displacement of aftershocks is constant with time after the occurrence of the first event, while it changes to a power-law with exponent close to 0.15 after the second major event, illustrating a slow diffusive process. During the first four days aftershocks cluster around the epicentral area of the second major event, while after that and taking as a reference the second event, the aftershock zone is migrating slowly with time to the west near the epicentral area of the first event. This process is much slower from what would be expected from normal diffusion, a

  5. Non extensive statistical physics properties of the 2003 (Mw6.2), Lefkada, Ionian island Greece, aftershock sequence

    NASA Astrophysics Data System (ADS)

    Vallianatos, F.; Karakostas, V.; Papadimitriou, E.

    2012-04-01

    On 14 August 2003, Lefkada Island (Central Ionian) was affected by an Mw=6.2 earthquake. Due to a dense temporary seismic network that operating immediately after the main shock occurrence, hundreds of aftershocks were recorded and located with high precision whereas relocation of the main shock and early strong aftershocks became also feasible. Thus, the spatio-temporal distribution of aftershocks onto the main and the neighboring fault segments was investigated in detail enabling the recognition of four distinctive seismicity clusters separated by less active patches. The aftershock spatiotemporal properties studied here using the concept of Non-Extensive Statistical Physics (NESP). The cumulative distribution functions of the inter-event times and the inter-event distances are estimated for the data set in each seismicity cluster and the analysis results to a value of the statistical thermodynamic qT and qD parameters for each cluster, where qT varies from 1.15 to 1.47 and qD from 0.5 to 0.77 for the interevent times and distances distributions respectively. These values confirm the complexity and non-additivity of the spatiotemporal evolution of seismicity and the usefulness of NESP in investigating such phenomena. The temporal structure is also discussed using the complementary to NESP approach of superstatistics, which is based on a superposition of ordinary local equilibrium statistical mechanics. The result indicates that the temporal evolution of the Lefkada aftershock sequence in clusters A, B and C governed by very low number of degrees of freedom while D is less organized seismicity structure with a much higher number of degrees of freedom. Acknowledgments. This work was supported in part by the THALES Program of the Ministry of Education of Greece and the European Union in the framework of the project entitled "Integrated understanding of Seismicity, using innovative Methodologies of Fracture mechanics along with Earthquake and non extensive

  6. Properties of foreshocks and aftershocks of the nonconservative self-organized critical Olami-Feder-Christensen model.

    PubMed

    Helmstetter, Agnès; Hergarten, Stefan; Sornette, Didier

    2004-10-01

    Following Phys. Rev. Lett. 88, 238501 (2002)] who discovered aftershocks and foreshocks in the Olami-Feder-Christensen (OFC) discrete block-spring earthquake model, we investigate to what degree the simple toppling mechanism of this model is sufficient to account for the clustering of real seismicity in time and space. We find that synthetic catalogs generated by the OFC model share many properties of real seismicity at a qualitative level: Omori's law (aftershocks) and inverse Omori's law (foreshocks), increase of the number of aftershocks and of the aftershock zone size with the mainshock magnitude. There are, however, significant quantitative differences. The number of aftershocks per mainshock in the OFC model is smaller than in real seismicity, especially for large mainshocks. We find that foreshocks in the OFC catalogs can be in large part described by a simple model of triggered seismicity, such as the epidemic-type aftershock sequence (ETAS) model. But the properties of foreshocks in the OFC model depend on the mainshock magnitude, in qualitative agreement with the critical earthquake model and in disagreement with real seismicity and with the ETAS model.

  7. etas_solve: A robust program to estimate the ETAS parameters

    NASA Astrophysics Data System (ADS)

    Yagi, Y.; Kasahara, A.

    2015-12-01

    The epidemic-type aftershock sequence (ETAS) model introduced by Ogata (1988) has been widely used to quantitatively describe seismicity (e.g. Ogata, 1992; Llenos et al., 2009). However, only a few programs for estimation of the ETAS parameters are publicly available, and it is difficult to automatically apply some of them to observed data due to initial value dependence (e.g. Ogata, 2006). A robust ETAS estimation program is required to meet the recent enhancement of earthquake catalogs. In this study, we developed a new program, etas_solve, that is based on Newton's method and calculates exact gradient and Hessian by using the automatic differentiation technique (Griewank, 1989). The program also supports auxiliary window in time and magnitude (Wang et al., 2010).To demonstrate robustness of the developed program, we tested the dependence of estimated parameters on the choice of initial value by running the program from 1,024 randomly chosen initial values, and then compared the results with that of SAPP (Ogata 2006). We used aftershock data of 26th July 2003 earthquake of M6.2 at the northern Miyagi japan, which is shipped with SAPP, as a testing data. We found that estimation values with etas_solve were independent of the initial value for the testing data, while that with SAPP were varied with the initial value. Although there was initial value dependence in the SAPP's results, the estimated values by SAPP with small (≤10-5) gradient coincided with the solution by etas_solve. etas_solve took longer computation time per iteration than SAPP due to the exact Hessian calculation, but total execution time was comparable to that of SAPP since less number of iterations for convergence was required. In addition, etas_solve was faster than SAPP on multicore machines (around 8-fold speed up with a 16 core machine) since etas_solve is parallelized by OpenMP.etas_solve is written in Fortran and distributed under GNU General Public License at https

  8. Earthquake source parameters for the 2010 January Haiti main shock and aftershock sequence

    NASA Astrophysics Data System (ADS)

    Nettles, Meredith; Hjörleifsdóttir, Vala

    2010-10-01

    Previous analyses of geological and geodetic data suggest that the obliquely compressive relative motion across the Caribbean-North America plate boundary in Hispaniola is accommodated through strain partitioning between near-vertical transcurrent faults on land and low-angle thrust faults offshore. In the Dominican Republic, earthquake focal-mechanism geometries generally support this interpretation. Little information has been available about patterns of seismic strain release in Haiti, however, due to the small numbers of moderate-to-large earthquakes occurring in western Hispaniola during the modern instrumental era. Here, we analyse the damaging MW = 7.0 earthquake that occurred near Port au Prince on 2010 January 12 and aftershocks occurring in the four months following this event, to obtain centroid-moment-tensor (CMT) solutions for 50 earthquakes with magnitudes as small as MW = 4.0. While the 2010 January main shock exhibited primarily strike-slip motion on a steeply dipping nodal plane (strike=250°, dip=71° and rake=22°), we find that nearly all of the aftershocks show reverse-faulting motion, typically on high-angle (30°-45°) nodal planes. Two small aftershocks (MW 4.5 and 4.6), located very close to the main shock epicentre, show strike-slip faulting with geometries similar to the main shock. One aftershock located off the south coast of Haiti shows low-angle thrust faulting. We also examine earthquakes occurring in this region from 1977-2009 successful analysis of four such events provides evidence for both strike-slip and reverse faulting. The pattern of seismic strain release in southern Haiti thus indicates that partitioning of plate motion between transcurrent and reverse structures extends far west within Hispaniola. While we see limited evidence for low-angle underthrusting offshore, most reverse motion appears to occur on high-angle fault structures adjacent to the Enriquillo fault. Our results highlight the need to incorporate seismogenic

  9. Fractal structure and predictability of distances between consecutive events: an analysis of three seismic aftershock sequences in Southern California

    NASA Astrophysics Data System (ADS)

    Martinez, Maria-Dolors; Lana, Xavier; Monterrubio, Marisol; Serra, Carina

    2015-04-01

    Three series of distances between consecutive seismic events are analysed by means of mono- and multifractal techniques with the aim of quantifying the complexity of their physical mechanism and their predictability and predictive instability. These series are also simulated by means of fractional noise by taking into account their self-affine character, the dependence of their power spectra on frequency and the values of Hurst and Hausdorff exponents. The prediction of these series is also attempted by means of an autoregressive AR(p) process to estimate the p+1 distance depending on the previous p distances. The interevent distance series are derived from the aftershock sequences associated with Landers (Mw 7.3 June 28, 1992), Northridge (Mw 6.7 January 17, 1994) and Hector Mine (Mw 7.1 October 16, 1999) mainshocks. The seismic records are obtained from the Southern California Seismic Network (SCSN) catalogue. Aftershocks with Mw equalling to or exceeding 2.0 are considered in order to assure catalogue completeness.

  10. The 1997 Umbria-Marche, Italy, Earthquake Sequence: A first look at the main shocks and aftershocks

    NASA Astrophysics Data System (ADS)

    Amato, A.; Azzara, R.; Chiarabba, C.; Cimini, G. B.; Cocco, M.; Di Bona, M.; Margheriti, L.; Mazza, S.; Mele, F.; Selvaggi, G.; Basili, A.; Boschi, E.; Courboulex, F.; Deschamps, A.; Gaffet, S.; Bittarelli, G.; Chiaraluce, L.; Piccinini, D.; Ripepe, M.

    A long sequence of earthquakes, six with magnitudes between 5 and 6, struck Central Italy starting on September 26, 1997, causing severe damages and loss of human lives. The seismogenic structure consists of a NW-SE elongated fault zone extending for about 40 km. The focal mechanisms of the largest shocks reveal normal faulting with NE-SW extension perpendicular to the trend of the Apennines, consistently with the Quaternary tectonic setting of the internal sector of the belt and with previous earthquakes in adjacent regions. Preliminary data on the main shocks and aftershocks show that extension in this region of the Apennines is accomplished by normal faults dipping at low angle (∼40°) to the southwest, and confined in the upper ∼8 km of the crust. These normal faults might have reactivated thrust planes of the Pliocene compressional tectonics. The aftershock distribution and the damage patterns also suggest that the three main shocks ruptured distinct 5 to 15 km-long fault segments, adjacent and slightly offset from one another.

  11. The Mw 5.8 Mineral, Virginia, earthquake of August 2011 and aftershock sequence: constraints on earthquake source parameters and fault geometry

    USGS Publications Warehouse

    McNamara, Daniel E.; Benz, H.M.; Herrmann, Robert B.; Bergman, Eric A.; Earle, Paul; Meltzer, Anne; Withers, Mitch; Chapman, Martin

    2014-01-01

    The Mw 5.8 earthquake of 23 August 2011 (17:51:04 UTC) (moment, M0 5.7×1017  N·m) occurred near Mineral, Virginia, within the central Virginia seismic zone and was felt by more people than any other earthquake in United States history. The U.S. Geological Survey (USGS) received 148,638 felt reports from 31 states and 4 Canadian provinces. The USGS PAGER system estimates as many as 120,000 people were exposed to shaking intensity levels of IV and greater, with approximately 10,000 exposed to shaking as high as intensity VIII. Both regional and teleseismic moment tensor solutions characterize the earthquake as a northeast‐striking reverse fault that nucleated at a depth of approximately 7±2  km. The distribution of reported macroseismic intensities is roughly ten times the area of a similarly sized earthquake in the western United States (Horton and Williams, 2012). Near‐source and far‐field damage reports, which extend as far away as Washington, D.C., (135 km away) and Baltimore, Maryland, (200 km away) are consistent with an earthquake of this size and depth in the eastern United States (EUS). Within the first few days following the earthquake, several government and academic institutions installed 36 portable seismograph stations in the epicentral region, making this among the best‐recorded aftershock sequences in the EUS. Based on modeling of these data, we provide a detailed description of the source parameters of the mainshock and analysis of the subsequent aftershock sequence for defining the fault geometry, area of rupture, and observations of the aftershock sequence magnitude–frequency and temporal distribution. The observed slope of the magnitude–frequency curve or b‐value for the aftershock sequence is consistent with previous EUS studies (b=0.75), suggesting that most of the accumulated strain was released by the mainshock. The aftershocks define a rupture that extends between approximately 2–8 km in depth and 8–10 km along

  12. Performance of aftershock forecasts: problem and formulation

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Wu, Z.; Li, L.

    2010-12-01

    WFSD project deals with the problems of earthquake physics, in which one of the important designed aims is the forecast of the on-going aftershock activity of the Wenchuan earthquake, taking the advantage of the fast response to great earthquakes. Correlation between fluid measurements and aftershocks provided heuristic clues to the forecast of aftershocks, invoking the discussion on the performance of such ‘precursory anomalies’, even if in a retrospective perspective. In statistical seismology, one of the critical issues is how to test the statistical significance of an earthquake forecast scheme against real seismic activity. Due to the special characteristics of aftershock series and the feature of aftershock forecasts that it deals with a limited spatial range and specific temporal duration, the test of the performance of aftershock forecasts has to be different from the standard tests for main shock series. In this presentation we address and discuss the possible schemes for testing the performance of aftershock forecasts - a seemingly simple but practically important issue in statistical seismology. As a simple and preliminary approach, we use an alternative form of Receiver Operating Characteristic (ROC) test, as well as other similar tests, considering the properties of aftershock series by using Omori law, ETAS model, and/or CFS calculation. We also discussed the lessons and experiences of the Wenchuan aftershock forecasts, exploring how to make full use of the present knowledge of the regularity of aftershocks to serve the earthquake rescue and relief endeavor as well as the post-earthquake reconstruction.

  13. Diffusion of epicenters of earthquake aftershocks, Omori's law, and generalized continuous-time random walk models.

    PubMed

    Helmstetter, A; Sornette, D

    2002-12-01

    The epidemic-type aftershock sequence (ETAS) model is a simple stochastic process modeling seismicity, based on the two best-established empirical laws, the Omori law (power-law decay approximately 1/t(1+theta) of seismicity after an earthquake) and Gutenberg-Richter law (power-law distribution of earthquake energies). In order to describe also the space distribution of seismicity, we use in addition a power-law distribution approximately 1/r(1+mu) of distances between triggered and triggering earthquakes. The ETAS model has been studied for the last two decades to model real seismicity catalogs and to obtain short-term probabilistic forecasts. Here, we present a mapping between the ETAS model and a class of CTRW (continuous time random walk) models, based on the identification of their corresponding master equations. This mapping allows us to use the wealth of results previously obtained on anomalous diffusion of CTRW. After translating into the relevant variable for the ETAS model, we provide a classification of the different regimes of diffusion of seismic activity triggered by a mainshock. Specifically, we derive the relation between the average distance between aftershocks and the mainshock as a function of the time from the mainshock and of the joint probability distribution of the times and locations of the aftershocks. The different regimes are fully characterized by the two exponents theta and mu. Our predictions are checked by careful numerical simulations. We stress the distinction between the "bare" Omori law describing the seismic rate activated directly by a mainshock and the "renormalized" Omori law taking into account all possible cascades from mainshocks to aftershocks of aftershock of aftershock, and so on. In particular, we predict that seismic diffusion or subdiffusion occurs and should be observable only when the observed Omori exponent is less than 1, because this signals the operation of the renormalization of the bare Omori law, also at the

  14. Evidence Against the New Madrid Long-Lived Aftershock Hypothesis

    NASA Astrophysics Data System (ADS)

    Page, M. T.; Hough, S. E.

    2014-12-01

    It has been suggested that continuing seismicity in the New Madrid, central U.S. region is primarily composed of the continuing long-lived aftershock sequence of the 1811-1812 sequence, and thus cannot be taken as an indication of present-day strain accrual in the region. We examine historical and instrumental seismicity in the New Madrid region to determine if such a model is feasible given 1) the observed protracted nature of past New Madrid sequences, with multiple mainshocks with apparently similar magnitudes; 2) historical rates of M≥6 earthquakes after the initial activity in 1811-1812; and 3) the modern seismicity rate in the region. We use ETAS modeling to search for sub-critical sets of direct Omori parameters that are consistent with all of these datasets, given a realistic consideration of their uncertainties. High aftershock productivity is required both to match the observation of multiple mainshocks and to explain the modern level of activity as aftershocks; synthetic sequences consistent with these observations substantially overpredict the number of events of M≥6 that were observed in the past 200 years. Our results imply that ongoing background seismicity in the New Madrid region is driven by ongoing strain accrual processes and that, despite low deformation rates, seismic activity in the zone is not decaying with time.

  15. Evidence that Stress Amplitude Does Not Affect the Temporal Distribution of Aftershocks

    NASA Astrophysics Data System (ADS)

    Felzer, K. R.

    2005-12-01

    Most physical aftershock triggering models, including the rate and state friction model of Dieterich (1994), the stress corrosion model (see discussion in Gomberg, 2001) and other accelerating failure models predict that larger stress changes on a fault will lead to an aftershocks that happens more quickly (larger clock advance), all else equal. Thus as stress change amplitude decreases with distance from the mainshock, there is an expected shift in the aftershock distribution toward longer time delays. This effect was formalized by Dieterich (1994) as an increase of the modified Omori Law c value (N(t) = A/(t+c)p where t = time, N(t) = aftershock rate, and A, p, and c are constants). Jones and Hauksson (1998), however, found no change in c value with distance after the 1992 MW 7.3 Landers earthquake. The assumption that the aftershock temporal distribution is independent of distance is also made in ETAS (Epidemic Triggering Aftershock Sequence) aftershock simulations (Ogata, 1998; Helmstetter, 2002) without adverse affect on fitting real data. Here we verify the independence of stress change and aftershock temporal distribution using a data set of 33 M 5-6 mainshocks from throughout California. These mainshocks are large enough to produce a significant number of aftershocks in the near and far field, but small enough to be frequent and thus provide good statistical sampling. Our data verifies that the temporal distribution of aftershocks is independent of stress change amplitude. We suggest that the most likely explanation for this observation is that the timing of each fault that participates in an aftershock sequence is independent of the amplitude of the stress that triggers it. In this case aftershock decay with distance from the mainshock cannot be caused by smaller clock advances on lesser-stressed faults, as in the Dieterich (1994) model, but rather by a stress amplitude dependent probability that a fault will be clock advanced at all. In future work we

  16. A Nonparametric Bayesian Approach to Seismic Hazard Modeling Using the ETAS Framework

    NASA Astrophysics Data System (ADS)

    Ross, G.

    2015-12-01

    The epidemic-type aftershock sequence (ETAS) model is one of the most popular tools for modeling seismicity and quantifying risk in earthquake-prone regions. Under the ETAS model, the occurrence times of earthquakes are treated as a self-exciting Poisson process where each earthquake briefly increases the probability of subsequent earthquakes occurring soon afterwards, which captures the fact that large mainshocks tend to produce long sequences of aftershocks. A triggering kernel controls the amount by which the probability increases based on the magnitude of each earthquake, and the rate at which it then decays over time. This triggering kernel is usually chosen heuristically, to match the parametric form of the modified Omori law for aftershock decay. However recent work has questioned whether this is an appropriate choice. Since the choice of kernel has a large impact on the predictions made by the ETAS model, avoiding misspecification is crucially important. We present a novel nonparametric version of ETAS which avoids making parametric assumptions, and instead learns the correct specification from the data itself. Our approach is based on the Dirichlet process, which is a modern class of Bayesian prior distribution which allows for efficient inference over an infinite dimensional space of functions. We show how our nonparametric ETAS model can be fit to data, and present results demonstrating that the fit is greatly improved compared to the standard parametric specification. Additionally, we explain how our model can be used to perform probabilistic declustering of earthquake catalogs, to classify earthquakes as being either aftershocks or mainshocks. and to learn the causal relations between pairs of earthquakes.

  17. The 2007 Tocopilla earthquake and its aftershock sequence - A subduction zone earthquake at the edge of the northern Chile seimic gap

    NASA Astrophysics Data System (ADS)

    Eggert, S.; Sobiesiak, M.; Shirzaei, M.

    2010-12-01

    On 14 November 2007 a large Mw 7.7 earthquake occurred in the region of Tocopilla in Northern Chile. The earthquake took place in the southern end of the Northern Chile seismic gap which is supposed to be at the end of its seismic cycle. Studying the event and its aftershock sequence will provide closer insight into the behavior of a subduction zone earthquake at the edge of a subduction zone segment. We present a comprehensive study of the rupture area combining seismic and geodetic data. The aftershock sequence following the earthquake was very well recorded by a local seismic network of 34 short period and broad band stations. The spatial distribution of the aftershock sequence shows a concentration of aftershocks around the north-western part of the Mejillones Peninsula and along the coast up to the Río Loa. The distribution into depth shows that the majority of the hypocenters are located along the subduction interface, reaching down to ~ 50 km depth. In the western part, the aftershock sequence splits into two branches, one heading towards the trench, the other bending into the crust in front of the Mejillones Peninsula. These seismic observations lead to the conclusion that the fault rupture propagated towards the south-west with a fault plane of about 150 km length leaving the shallow part in the north west probably unbroken. To better understand the behavior of the aftershock distribution we model the Coulomb stress transfer along the fault plane. The results show that stresses are increased in the southern part of the rupture area where we find a high concentration of aftershocks. This is consistent with the calculated energy release that shows two main patches along the plate interface rupturing from north to south. The 2007 Tocopilla earthquake is the first large event that occurred inside the Northern Chile seismic gap since the 1877 Iquique event. The rupture process stopped underneath the Mejillones Peninsula, a proposed segment boundary along the

  18. April 25, 2015, Gorkha Earthquake, Nepal and Sequence of Aftershocks: Key Lessons

    NASA Astrophysics Data System (ADS)

    Guragain, R.; Dixit, A. M.; Shrestha, S. N.

    2015-12-01

    The Gorkha Earthquake of M7.8 hit Nepal on April 25, 2015 at 11:56 am local time. The epicenter of this earthquake was Barpak, Gorkha, 80 km northwest of Kathmandu Valley. The main shock was followed by hundreds of aftershocks including M6.6 and M6.7 within 48 hours and M7.3 on May 12, 2015. According to the Government of Nepal, a total of 8,686 people lost their lives, 16,808 people injured, over 500,000 buildings completely collapsed and more than 250,000 building partially damaged. The National Society for Earthquake Technology - Nepal (NSET), a not-for-profit civil society organization that has been focused on earthquake risk reduction in Nepal for past 21 years, conducted various activities to support people and the government in responding to the earthquake disaster. The activities included: i) assisting people and critical facility institutions to conduct rapid visual building damage assessment including the training; ii) information campaign to provide proper information regarding earthquake safety; iii) support rescue organizations on search and rescue operations; and iv) provide technical support to common people on repair, retrofit of damaged houses. NSET is also involved in carrying out studies related to earthquake damage, geotechnical problems, and causes of building damages. Additionally, NSET has done post-earthquake detail damage assessment of buildings throughout the affected areas. Prior to the earthquake, NSET has been working with several institutions to improve seismic performance of school buildings, private residential houses, and other critical structures. Such activities implemented during the past decade have shown the effectiveness of risk reduction. Retrofitted school buildings performed very well during the earthquake. Preparedness activities implemented at community levels have helped communities to respond immediately and save lives. Higher level of earthquake awareness achieved including safe behavior, better understanding of

  19. Typical Scenario of Preparation, Implementation, and Aftershock Sequence of a Large Earthquake

    NASA Astrophysics Data System (ADS)

    Rodkin, Mikhail

    2016-04-01

    We have tried here to construct and examine the typical scenario of a large earthquake occurrence. The Harvard seismic moment GCMT catalog was used to construct the large earthquake generalized space-time vicinity (LEGV) and to investigate the seismicity behavior in LEGV. LEGV was composed of earthquakes falling into the zone of influence of any of the considerable number (100, 300, or 1,000) of largest earthquakes. The LEGV construction is aimed to enlarge the available statistics, diminish a strong random component, and to reveal in result the typical features of pre- and post-shock seismic activity in more detail. In result of the LEGV construction the character of fore- and aftershock cascades was examined in more detail than it was possible without of the use of the LEGV approach. It was shown also that the mean earthquake magnitude tends to increase, and the b-values, mean mb/mw ratios, apparent stress values, and mean depth tend to decrease. Amplitudes of all these anomalies increase with an approach to a moment of the generalized large earthquake (GLE) as a logarithm of time interval from GLE occurrence. Most of the discussed anomalies agree well with a common scenario of development of instability. Besides of such precursors of common character, one earthquake-specific precursor was found. The revealed decrease of mean earthquake depth during large earthquake preparation testifies probably for the deep fluid involvement in the process. The revealed in LEGV typical features of development of shear instability agree well with results obtained in laboratory acoustic emission (AE) study. Majority of the revealed anomalies appear to have a secondary character and are connected mainly with an increase in a mean earthquake magnitude in LEGV. The mean magnitude increase was shown to be connected mainly with a decrease of a portion of moderate size events (Mw 5.0 - 5.5) in a closer GLE vicinity. We believe that this deficit of moderate size events hardly can be

  20. Imaging the high-frequency energy radiation process of a main shock and its early aftershock sequence: The case of the 2008 Iwate-Miyagi Nairiku earthquake, Japan

    NASA Astrophysics Data System (ADS)

    Sawazaki, Kaoru; Enescu, Bogdan

    2014-06-01

    To understand the energy release process that operates at the end of the main shock rupture and start of the aftershock activity, we propose an inversion method that uses continuous high-frequency seismogram envelopes of the main shock and early aftershocks (i.e., events that occur at short times after the main shock). In our approach, the aftershock sequence is regarded as a continuous energy release process, rather than a discrete time series of events. To correct for the contribution of coda wave energy excited by multiple scattering, we use the theoretical envelope synthesized on the basis of the radiative transfer theory as a Green's function. The site amplification factors are corrected considering the conservation of energy flux and using the coda normalization method. The inverted temporal energy release rate for the 2008 MW 6.9 Iwate-Miyagi Nairiku earthquake, Japan, decays following t-1.1, at the lapse time t of 40-900 s after the main shock origin time. This exponent of the decay rate is similar to the p value of the modified Omori law. The amount of estimated energy release is consistent with that calculated from the magnitude listed in the aftershock catalog. Although the uncertainty is large, the location of large energy release at the lapse times of 40-900 s approximately overlaps to that of the aftershocks, which surrounds the large energy release area during the main shock faulting. The maxima of the energy release rate normalized by the average decay rate distributes following a power law, similar to the Gutenberg-Richter law.

  1. Damped regional-scale stress inversions: Methodology and examples for southern California and the Coalinga aftershock sequence

    USGS Publications Warehouse

    Hardebeck, J.L.; Michael, A.J.

    2006-01-01

    We present a new focal mechanism stress inversion technique to produce regional-scale models of stress orientation containing the minimum complexity necessary to fit the data. Current practice is to divide a region into small subareas and to independently fit a stress tensor to the focal mechanisms of each subarea. This procedure may lead to apparent spatial variability that is actually an artifact of overfitting noisy data or nonuniquely fitting data that does not completely constrain the stress tensor. To remove these artifacts while retaining any stress variations that are strongly required by the data, we devise a damped inversion method to simultaneously invert for stress in all subareas while minimizing the difference in stress between adjacent subareas. This method is conceptually similar to other geophysical inverse techniques that incorporate damping, such as seismic tomography. In checkerboard tests, the damped inversion removes the stress rotation artifacts exhibited by an undamped inversion, while resolving sharper true stress rotations than a simple smoothed model or a moving-window inversion. We show an example of a spatially damped stress field for southern California. The methodology can also be used to study temporal stress changes, and an example for the Coalinga, California, aftershock sequence is shown. We recommend use of the damped inversion technique for any study examining spatial or temporal variations in the stress field.

  2. Estimating ETAS: the effects of truncation, missing data, and model assumptions

    NASA Astrophysics Data System (ADS)

    Seif, Stefanie; Mignan, Arnaud; Zechar, Jeremy; Werner, Maximilian; Wiemer, Stefan

    2016-04-01

    The Epidemic-Type Aftershock Sequence (ETAS) model is widely used to describe the occurrence of earthquakes in space and time, but there has been little discussion of the limits of, and influences on, its estimation. What has been established is that ETAS parameter estimates are influenced by missing data (e.g., earthquakes are not reliably detected during lively aftershock sequences) and by simplifying assumptions (e.g., that aftershocks are isotropically distributed). In this article, we investigate the effect of truncation: how do parameter estimates depend on the cut-off magnitude, Mcut, above which parameters are estimated? We analyze catalogs from southern California and Italy and find that parameter variations as a function of Mcut are caused by (i) changing sample size (which affects e.g. Omori's cconstant) or (ii) an intrinsic dependence on Mcut (as Mcut increases, absolute productivity and background rate decrease). We also explore the influence of another form of truncation - the finite catalog length - that can bias estimators of the branching ratio. Being also a function of Omori's p-value, the true branching ratio is underestimated by 45% to 5% for 1.05< p <1.2. Finite sample size affects the variation of the branching ratio estimates. Moreover, we investigate the effect of missing aftershocks and find that the ETAS productivity parameters (α and K0) and the Omoris c-value are significantly changed only for low Mcut=2.5. We further find that conventional estimation errors for these parameters, inferred from simulations that do not account for aftershock incompleteness, are underestimated by, on average, a factor of six.

  3. Space time ETAS models and an improved extension

    NASA Astrophysics Data System (ADS)

    Ogata, Yosihiko; Zhuang, Jiancang

    2006-02-01

    For sensitive detection of anomalous seismicity such as quiescence and activation in a given region, we need a suitable statistical reference model that represents a normal seismic activity in the region. The regional occurrence rate of the earthquakes is modeled as a function of previous activity, the specific form of which is based on empirical laws in time and space such as the modified Omori formula and the Utsu-Seki scaling law of aftershock area against magnitude, respectively. This manuscript summarizes the development of the epidemic type aftershock sequence (ETAS) model and proposes an extended version of the best fitted space-time model that was suggested in Ogata [Ogata, Y., 1998. Space-time point-process models for earthquake occurrences, Ann. Inst. Statist. Math., 50: 379-402.]. This model indicates significantly better fit to seismicity in various regions in and around Japan.

  4. Preliminary report on aftershock sequence for earthquake of January 31, 1986, near Painesville, Ohio (time period: 2/1/86-2/10/86)

    USGS Publications Warehouse

    Borcherdt, R. D.

    1986-01-01

    A ten-station array of broad-band digital instrumentation (GEOS) was deployed by the U. S. Geological Survey with partial support provided by Electric Power Research Institute to record the aftershock sequence of the moderate (mb ~ 4.9) earthquake that occurred on January 31, 1986 (16:46:43 UTC) near Painesville, Ohio. The occurrence of the event has raised questions concerning possible contributory factors to the occurrence of the event and questions concerning the character of earthquake-induced high-frequency ground motions in the area. To aid in the timely resolution of the implications of some of these questions, this preliminary report provides copies of the ground motion time-histories and corresponding spectra for the six identified aftershocks and two events, thought to be quarry blasts, recorded as of February 10, 1986. Recording station locations and epicenter locations based on two preliminary estimates of local seismic velocity structure are provided.

  5. Some statistical features of the aftershock temporal behavior after the M7.4 Izmit earthquake of august 17, 1999 in Turkey

    NASA Astrophysics Data System (ADS)

    Gospodinov, D.; Fajtin, H.; Rangelov, B.; Marekova, E.

    2009-04-01

    An earthquake of magnitude Mw=7.4 struck 8 km. southeast of Izmit, Turkey at 3:02 AM local time on August 17, 1999. The earthquake occurred on one of the world's longest and best studied strike-slip (horizontal motion) faults - the east-west trending North Anatolian fault. Seismologists are not able to predict the timing and sizes of individual aftershocks but stochastic modeling allows determinationof probabilities for aftershocks and larger mainshocks duringintervals following the mainshock. The most widely applied stochastic model to depict aftershocks temporal distribution is the non- homogenous Poisson process with a decaying intensity, which follows the Modified Omori Formula (MOF) (Utsu, 1961). A more complex model, considering the triggering potential of each aftershock was developed by Ogata (1988) and it was named Epidemic Type Aftershock Sequence (ETAS) model. Gospodinov and Rotondi (2006) elaborated a Restricted Epidemic Type Aftershock Sequence (RETAS) model. The latter follows the general idea that only aftershocks stronger than some cut-off magnitude possess the capability to induce secondary aftershock activity. In this work we shall consider the Restricted Epidemic Type Aftershock Sequence (RETAS) model, for which the conditional intensity function turns out to be ‘ K0eα(Mi-M0)- λ (t|Ht) = + (t- ti + c)p ti < t Mi ≥ Mth (1) Here the summation occurs for all aftershocks with magnitude bigger than or equal to Mth, which took place before time. Leaving Mth to take all possible values, one can examine all RETAS model versions between the MOF and the ETAS model on the basis of the Akaike Information Criterion AIC (Akaike, 1974) AIC = - 2max log L+ 2k (2) where k is the number of parameters used in the model and logL is the logarithm of the likelihood function. Then for the model providing the best fit, we choose the one with the smallest AIC value. The purpose of this paper is to verify versions of the RETAS model (including the MOF and the

  6. Imaging the high-frequency energy radiation process of a mainshock and its early aftershock sequence for a crustal earthquake in Japan

    NASA Astrophysics Data System (ADS)

    Sawazaki, K.; Enescu, B.

    2013-12-01

    Waveform recordings of aftershocks occurring immediately after a mainshock are mostly hidden by the coda wave of the mainshock and overlap one with each other. Consequently, the detection of such early events is very difficult and the completeness of earthquake catalogs at short times after large events becomes poor. To overcome this difficulty, we developed an inversion scheme which measures the energy radiation process of the early aftershock sequence using continuous seismogram envelopes in the 1-16 Hz frequency range. This inversion scheme makes use of the coda wave envelope, synthesized on the basis of the radiative transfer theory as the Green's function. Here the multiple isotropic scattering and intrinsic attenuation parameters in a 3-D infinite scattering medium are estimated through the multiple lapse time window analysis. The site amplification factor is also corrected using the coda normalization method. We apply the envelope inversion technique to the 2008 Iwate-Miyagi Nairiku earthquake, Japan (Mw6.9), and its early aftershock sequence. The inverted energy release rate has two stages. At 10-30 s and 30-600 s after the mainshock origin time, the energy release rate decays following t(-4 to -8) and t(-1 to -2), respectively. The modified Omori formula cannot fit the energy release rate before 30 s. This change in the temporal decay rate suggests that the mechanism of energy release process changes; the energy release from the termination stage of the mainshock rupture dominates before 30 s, while that by the early aftershocks dominates at later times.

  7. Phylogenetic relations of humans and African apes from DNA sequences in the Psi eta-globin region

    SciTech Connect

    Miyamoto, M.M.; Slightom, J.L.; Goodman, M.

    1987-10-16

    Sequences from the upstream and downstream flanking DNA regions of the Psi eta-globin locus in Pan troglodytes (common chimpanzee), Gorilla gorilla (gorilla), and Pongo pygmaeus (orangutan, the closest living relative to Homo, Pan, and Gorilla) provided further data for evaluating the phylogenetic relations of humans and African apes. These newly sequenced orthologs (an additional 4.9 kilobase pairs (kbp) for each species) were combined with published Psi eta-gene sequences and then compared to the same orthologous stretch (a continuous 7.1-kbp region) available for humans. Phylogenetic analysis of these nucleotide sequences by the parsimony method indicated (i) that human and chimpanzee are more closely related to each other than either is to gorilla and (ii) that the slowdown in the rate of sequence evolution evident in higher primates is especially pronounced in humans. These results indicate that features unique to African apes (but not to humans) are primitive and that even local molecular clocks should be applied with caution.

  8. The 1979 Homestead Valley earthquake sequence, California: control of aftershocks and postseismic deformation.

    USGS Publications Warehouse

    Stein, R.S.; Lisowski, M.

    1983-01-01

    The coseismic slip and geometry of the March 15, 1979, Homestead Valley, California, earthquake sequence are well constrained by precise horizontal and vertical geodetic observations and by data from a dense local seismic network. These observations indicate 0.52 + or - 0.10 m of right-lateral slip and 0.17 + or - 0.04 m of reverse slip on a buried vertical 6-km-long and 5-km-deep fault and yield a mean static stress drop of 7.2 + or -1.3 MPa. The largest shock had Ms = 5.6. Observations of the ground rupture revealed up to 0.1 m of right-lateral slip on two mapped faults that are subparallel to the modeled seismic slip plane. In the 1.9 years since the earthquakes, geodetic network displacements indicate that an additional 60+ or -10 mm of postseismic creep took place. The rate of postseismic shear strain (0.53 + or - 0.13 mu rad/yr) measured within a 30 X 30-km network centered on the principal events was anomalously high compared to its preearthquake value and the postseismic rate in the adjacent network. This transient cannot be explained by postseismic slip on the seismic fault but rather indicates that broadside release of strain followed the earthquake sequence. -Authors

  9. Source Process of the Mw 5.0 Au Sable Forks, New York, Earthquake Sequence from Local Aftershock Monitoring Network Data

    NASA Astrophysics Data System (ADS)

    Kim, W.; Seeber, L.; Armbruster, J. G.

    2002-12-01

    On April 20, 2002, a Mw 5 earthquake occurred near the town of Au Sable Forks, northeastern Adirondacks, New York. The quake caused moderate damage (MMI VII) around the epicentral area and it is well recorded by over 50 broadband stations in the distance ranges of 70 to 2000 km in the Eastern North America. Regional broadband waveform data are used to determine source mechanism and focal depth using moment tensor inversion technique. Source mechanism indicates predominantly thrust faulting along 45° dipping fault plane striking due South. The mainshock is followed by at least three strong aftershocks with local magnitude (ML) greater than 3 and about 70 aftershocks are detected and located in the first three months by a 12-station portable seismographic network. The aftershock distribution clearly delineate the mainshock rupture to the westerly dipping fault plane at a depth of 11 to 12 km. Preliminary analysis of the aftershock waveform data indicates that orientation of the P-axis rotated 90° from that of the mainshock, suggesting a complex source process of the earthquake sequence. We achieved an important milestone in monitoring earthquakes and evaluating their hazards through rapid cross-border (Canada-US) and cross-regional (Central US-Northeastern US) collaborative efforts. Hence, staff at Instrument Software Technology, Inc. near the epicentral area joined Lamont-Doherty staff and deployed the first portable station in the epicentral area; CERI dispatched two of their technical staff to the epicentral area with four accelerometers and a broadband seismograph; the IRIS/PASSCAL facility shipped three digital seismographs and ancillary equipment within one day of the request; the POLARIS Consortium, Canada sent a field crew of three with a near real-time, satellite telemetry based earthquake monitoring system. The Polaris station, KSVO, powered by a solar panel and batteries, was already transmitting data to the central Hub in London, Ontario, Canada within

  10. The 16 April 2015 M w 6.0 offshore eastern Crete earthquake and its aftershock sequence: implications for local/regional seismotectonics

    NASA Astrophysics Data System (ADS)

    Görgün, Ethem; Kekovalı, Kıvanç; Kalafat, Doğan

    2016-08-01

    We examine the 16 April 2015 M w 6.0 offshore eastern Crete earthquake and its aftershock sequence in southern Aegean Sea. Centroid moment tensors for 45 earthquakes with moment magnitudes (M w) between 3.3 and 6.0 are determined by applying a waveform inversion method. The mainshock is shallow focus thrust event with a strike-slip component at a depth of 30 km. The seismic moment (M o) of the mainshock is estimated as 1.33 × 1018 Nm, and rupture duration of the mainshock is 3.5 s. The focal mechanisms of aftershocks are mainly thrust faulting with a strike-slip component. The geometry of the moment tensors (M w ≥ 3.3) reveals a thrust-faulting regime with NE-SW-trending direction of T axis in the entire activated region. According to high-resolution hypocenter relocation of the eastern Crete earthquake sequence, one main cluster consisting of 352 events is revealed. The aftershock activity in the observation period between 5 January 2015 and 7 July 2015 extends from N to S direction. Seismic cross sections indicate a complex pattern of the hypocenter distribution with the activation of three segments. The subduction interface is clearly revealed with high-resolution hypocenter relocation and moment tensor solution. The best constrained focal depths indicate that the aftershock sequence is mainly confined in the upper plate (depth <40 km) and are ranging from about 4.5 to 39 km depth. A stress tensor inversion of focal mechanism data is performed to obtain a more precise picture of the offshore eastern Crete stress field. The stress tensor inversion results indicate a predominant thrust stress regime with a NW-SE-oriented maximum horizontal compressive stress (S H). According to variance of the stress tensor inversion, to first order, the Crete region is characterized by a homogeneous interplate stress field. We also investigate the Coulomb stress change associated with the mainshock to evaluate any significant enhancement of stresses along Crete and surrounding

  11. Operational Earthquake Forecasting of Aftershocks for New England

    NASA Astrophysics Data System (ADS)

    Ebel, J.; Fadugba, O. I.

    2015-12-01

    Although the forecasting of mainshocks is not possible, recent research demonstrates that probabilistic forecasts of expected aftershock activity following moderate and strong earthquakes is possible. Previous work has shown that aftershock sequences in intraplate regions behave similarly to those in California, and thus the operational aftershocks forecasting methods that are currently employed in California can be adopted for use in areas of the eastern U.S. such as New England. In our application, immediately after a felt earthquake in New England, a forecast of expected aftershock activity for the next 7 days will be generated based on a generic aftershock activity model. Approximately 24 hours after the mainshock, the parameters of the aftershock model will be updated using the observed aftershock activity observed to that point in time, and a new forecast of expected aftershock activity for the next 7 days will be issued. The forecast will estimate the average number of weak, felt aftershocks and the average expected number of aftershocks based on the aftershock statistics of past New England earthquakes. The forecast also will estimate the probability that an earthquake that is stronger than the mainshock will take place during the next 7 days. The aftershock forecast will specify the expected aftershocks locations as well as the areas over which aftershocks of different magnitudes could be felt. The system will use web pages, email and text messages to distribute the aftershock forecasts. For protracted aftershock sequences, new forecasts will be issued on a regular basis, such as weekly. Initially, the distribution system of the aftershock forecasts will be limited, but later it will be expanded as experience with and confidence in the system grows.

  12. Fault-Zone Trapped Waves from Aftershocks of the M7.2 Darfield and M6.3 Christchurch Earthquake Sequence for Document of Subsurface Damage Zones

    NASA Astrophysics Data System (ADS)

    Li, Y.; De Pascale, G. P.; Gravley, D.; Cherrington, J.; Alvarez, M. G.

    2011-12-01

    The M6.3 Christchurch earthquake struck the Canterbury region in NZ's South Island on 22 February 2011, following ~6 months after the Sept. 4, 2010 M7.1 Darfield earthquake in the same region. It has generated a significant series of aftershocks, many of which are considered big for a M6.3 earthquake. It is not know clearly whether the later M6.3 event is technically an aftershock because of its relationship to the ongoing activity since September last year, or it is a separate event, given its location on a separate fault system, a previously unknown blind fault line running 17 km south of Christchurch. In order to study the complicated subsurface structure of the damage zones caused by this sequence of earthquakes in NZ, under the support of NSF-RAPID Program, we deployed 12 PASSCAL seismographs in two ~300-m long seismic lines across the Greendale fault where the horizontal right-lateral slip of 4.5 m and vertical slip of 1.6 m were caused by the 2010 M7.2 Darfield earthquake and the aftershock zone of the M6.3 Christchurch earthquake, respectively, to record fault-zone trapped waves (FZTWs) generated by aftershocks, starting from May 5th, 2011. We have recorded the data for ~300 M>3 aftershocks with good locations and more than ~1000 small events not located yet but with good signal-to-noise ratio at these two arrays, including M5.3, M6, M5.4, M5.1 aftershocks with their clustered events at depths of 10-15 km. Preliminary examination of the waveform data shows FZTWs clearly at stations located within the 50-75-m wide rupture zone with high density of en-echelon cracks on the ground surface along the Greendale fault. 3-D finite-difference simulations of these FZTWs show a distinct low-velocity zone (LVZ) at seismogenic depth, indicating that the Greendale fault has undergone strong dynamic stresses and pervasive cracking during the 2010 M7.2 Darfield earthquake. We interpret this LVZ as being a remnant of damage zone in dynamic ruptures that accumulated damage

  13. Stress shadows of the 2011 Mw=9.0 Tohoku-oki, Japan, earthquake: Suppressed aftershocks of the 2008 Mw=6.6 Iwate-Miyagi inland earthquake

    NASA Astrophysics Data System (ADS)

    Suzuki, Y.; Toda, S.

    2013-12-01

    Numerous papers of stress triggering have been published since 1990s. Among them, only a few studies have evidently shown that seismicity shut down or suppression associated with static Coulomb stress decrease (hereinafter 'stress shadow'). The reason only fewer reports exist is its restrictive conditions to detect stress shadow. To prove statistical significance, the following conditions are satisfied: (i) high seismicity rate before a disturbance, (ii) long elapsed time required since the disturbance, (iii) negative Coulomb stress on most of the pre-existing faults in the area. A preceding aftershocks before the disturbance is often used to satisfy the condition (i) (e.g. Toda and Stein, 2003). But one must strictly consider a temporal decay of aftershocks to fairly compare the post-disturbance rate with the pre-disturbance rate. To calibrate such potential bias, we employ the Epidemic-Type Aftershock Sequence (ETAS) model (Ogata, 1988) which can simulate the temporal decay and effect of secondary aftershocks. Here, we use the Japan Meteorological Agency (JMA) earthquake catalog from 2000 to June 2013 (depth≤25km) and examine any deviation of observed rate from theoretical seismicity predicted by the ETAS model after the 2011 Tohoku-oki earthquake. We here focus on aftershock areas of the 2008 Iwate-Miyagi inland earthquake (Mw 6.6), the 2003 North-Miyagi earthquake (Mw 6.0) and the 2010 Fukushima earthquake (Mw 5.5), all of which are mostly supposed to satisfy all the conditions. To detect seismicity rate change between before and after a stress perturbation, one must estimate the minimum magnitude of completeness (Mc) throughout the testing period. Based on a report of JMA (2012) and our own magnitude-frequency plots, we set Mc=3.0 in the Iwate-Miyagi inland earthquake and the North-Miyagi earthquake, and Mc=2.0 in the Fukushima earthquake regions. To rigorously define their aftershock zones, we calculate seismicity rate before (Rb) and after (Ra) their own

  14. Forecasting magnitude, time, and location of aftershocks for aftershock hazard

    NASA Astrophysics Data System (ADS)

    Chen, K.; Tsai, Y.; Huang, M.; Chang, W.

    2011-12-01

    In this study we investigate the spatial and temporal seismicity parameters of the aftershock sequence accompanying the 17:47 20 September 1999 (UTC) 7.45 Chi-Chi earthquake Taiwan. Dividing the epicentral zone into north of the epicenter, at the epicenter, and south of the epicenter, it is found that immediately after the earthquake the area close by the epicenter had a lower value than both the northern and southern sections. This pattern suggests that at the time of the Chi-Chi earthquake, the area close by the epicenter remained prone to large magnitude aftershocks and strong shaking. However, with time the value increases. An increasing value indicates a reduced likelihood of large magnitude aftershocks. The study also shows that the value is higher at the southern section of the epicentral zone, indicating a faster rate of decay in this section. The primary purpose of this paper is to design a predictive model for forecasting the magnitude, time, and location of aftershocks to large earthquakes. The developed model is presented and applied to the 17:47 20 September 1999 7.45 Chi-Chi earthquake Taiwan, and the 09:32 5 November 2009 (UTC) Nantou 6.19, and 00:18 4 March 2010 (UTC) Jiashian 6.49 earthquake sequences. In addition, peak ground acceleration trends for the Nantou and Jiashian aftershock sequences are predicted and compared to actual trends. The results of the estimated peak ground acceleration are remarkably similar to calculations from recorded magnitudes in both trend and level. To improve the predictive skill of the model for occurrence time, we use an empirical relation to forecast the time of aftershocks. The empirical relation improves time prediction over that of random processes. The results will be of interest to seismic mitigation specialists and rescue crews. We apply also the parameters and empirical relation from Chi-Chi aftershocks of Taiwan to forecast aftershocks with magnitude M > 6.0 of 05:46 11 March 2011 (UTC) Tohoku 9

  15. The LVD signals during the early-mid stages of the L'Aquila seismic sequence and the radon signature of some aftershocks of moderate magnitude.

    PubMed

    Cigolini, C; Laiolo, M; Coppola, D

    2015-01-01

    The L'Aquila seismic swarm culminated with the mainshock of April 6, 2009 (ML = 5.9). Here, we report and analyze the Large Volume Detector (LVD, used in neutrinos research) low energy traces (∼0.8 MeV), collected during the early-mid stages of the seismic sequence, together with the data of a radon monitoring experiment. The peaks of LVD traces do not correlate with the evolution and magnitude of earthquakes, including major aftershocks. Conversely, our radon measurements obtained by utilizing three automatic stations deployed along the regional NW-SE faulting system, seem to be, in one case, more efficient. In fact, the timeseries collected on the NW-SE Paganica fracture recorded marked variations and peaks that occurred during and prior moderate aftershocks (with ML > 3). The Paganica monitoring station (PGN) seems to better responds to active seismicity due to the fact that the radon detector was placed directly within the bedrock of an active fault. It is suggested that future networks for radon monitoring of active seismicity should preferentially implement this setting. PMID:25464041

  16. The LVD signals during the early-mid stages of the L'Aquila seismic sequence and the radon signature of some aftershocks of moderate magnitude.

    PubMed

    Cigolini, C; Laiolo, M; Coppola, D

    2015-01-01

    The L'Aquila seismic swarm culminated with the mainshock of April 6, 2009 (ML = 5.9). Here, we report and analyze the Large Volume Detector (LVD, used in neutrinos research) low energy traces (∼0.8 MeV), collected during the early-mid stages of the seismic sequence, together with the data of a radon monitoring experiment. The peaks of LVD traces do not correlate with the evolution and magnitude of earthquakes, including major aftershocks. Conversely, our radon measurements obtained by utilizing three automatic stations deployed along the regional NW-SE faulting system, seem to be, in one case, more efficient. In fact, the timeseries collected on the NW-SE Paganica fracture recorded marked variations and peaks that occurred during and prior moderate aftershocks (with ML > 3). The Paganica monitoring station (PGN) seems to better responds to active seismicity due to the fact that the radon detector was placed directly within the bedrock of an active fault. It is suggested that future networks for radon monitoring of active seismicity should preferentially implement this setting.

  17. Modeling aftershocks as a stretched exponential relaxation

    NASA Astrophysics Data System (ADS)

    Mignan, A.

    2015-11-01

    The decay rate of aftershocks has been modeled as a power law since the pioneering work of Omori in the late nineteenth century. Although other expressions have been proposed in recent decades to describe the temporal behavior of aftershocks, the number of model comparisons remains limited. After reviewing the aftershock models published from the late nineteenth century until today, I solely compare the power law, pure exponential and stretched exponential expressions defined in their simplest forms. By applying statistical methods recommended recently in applied mathematics, I show that all aftershock sequences tested in three regional earthquake catalogs (Southern and Northern California, Taiwan) and with three declustering techniques (nearest-neighbor, second-order moment, window methods) follow a stretched exponential instead of a power law. These results infer that aftershocks are due to a simple relaxation process, in accordance with most other relaxation processes observed in Nature.

  18. CHARACTERISTICS OF THE AFTERSHOCK SEQUENCE OF THE BORAH PEAK, IDAHO, EARTHQUAKE DETERMINED FROM DIGITAL RECORDINGS OF THE EVENTS.

    USGS Publications Warehouse

    Boatwright, John

    1985-01-01

    The U. S. Geological Survey, Menlo Park, deployed and maintained a network of twelve digital instruments over the 2 weeks following the October 28, 1983, Borah Peak, Idaho, earthquake. The network recorded 45 events with M greater than equivalent to 3. 0, and 6 events with M less than equivalent to 4. 0. The seismic moments of the aftershocks increase with increasing hypocentral depth below 12 km. The dynamic stress drops of the events do not show any systematic variation with depth, however. Most of the events with large stress drops are clustered in the northwest limb of the aftershock distribution; the average stress drop of the southern events is 31 plus or minus 16 bars, while the average stress drop of the events in the northwest limb is 77 plus or minus 52 bars. This clustering of events with large stress drops marks an apparent stress concentration, possibly associated with the arrest of the main shock rupture propagation by a fracture barrier at depth.

  19. Distribution of the largest aftershocks in branching models of triggered seismicity: theory of the universal Båth law.

    PubMed

    Saichev, A; Sornette, D

    2005-05-01

    Using the epidemic-type aftershock sequence (ETAS) branching model of triggered seismicity, we apply the formalism of generating probability functions to calculate exactly the average difference between the magnitude of a mainshock and the magnitude of its largest aftershock over all generations. This average magnitude difference is found empirically to be independent of the mainshock magnitude and equal to 1.2, a universal behavior known as Båth's law. Our theory shows that Båth's law holds only sufficiently close to the critical regime of the ETAS branching process. Allowing for error bars +/- 0.1 for Båth's constant value around 1.2, our exact analytical treatment of Båth's law provides new constraints on the productivity exponent alpha and the branching ratio n: 0.9 approximately < alpha < or =1. We propose a method for measuring alpha based on the predicted renormalization of the Gutenberg-Richter distribution of the magnitudes of the largest aftershock. We also introduce the "second Båth law for foreshocks:" the probability that a main earthquake turns out to be the foreshock does not depend on its magnitude rho.

  20. Clustering analysis of seismicity and aftershock identification.

    PubMed

    Zaliapin, Ilya; Gabrielov, Andrei; Keilis-Borok, Vladimir; Wong, Henry

    2008-07-01

    We introduce a statistical methodology for clustering analysis of seismicity in the time-space-energy domain and use it to establish the existence of two statistically distinct populations of earthquakes: clustered and nonclustered. This result can be used, in particular, for nonparametric aftershock identification. The proposed approach expands the analysis of Baiesi and Paczuski [Phys. Rev. E 69, 066106 (2004)10.1103/PhysRevE.69.066106] based on the space-time-magnitude nearest-neighbor distance eta between earthquakes. We show that for a homogeneous Poisson marked point field with exponential marks, the distance eta has the Weibull distribution, which bridges our results with classical correlation analysis for point fields. The joint 2D distribution of spatial and temporal components of eta is used to identify the clustered part of a point field. The proposed technique is applied to several seismicity models and to the observed seismicity of southern California.

  1. Rupture Processes of the Mw8.3 Sea of Okhotsk Earthquake and Aftershock Sequences from 3-D Back Projection Imaging

    NASA Astrophysics Data System (ADS)

    Jian, P. R.; Hung, S. H.; Meng, L.

    2014-12-01

    On May 24, 2013, the largest deep earthquake ever recorded in history occurred on the southern tip of the Kamchatka Island, where the Pacific Plate subducts underneath the Okhotsk Plate. Previous 2D beamforming back projection (BP) of P- coda waves suggests the mainshock ruptured bilaterally along a horizontal fault plane determined by the global centroid moment tensor solution. On the other hand, the multiple point source inversion of P and SH waveforms argued that the earthquake comprises a sequence of 6 subevents not located on a single plane but actually distributed in a zone that extends 64 km horizontally and 35 km in depth. We then apply a three-dimensional MUSIC BP approach to resolve the rupture processes of the manishock and two large aftershocks (M6.7) with no a priori setup of preferential orientations of the planar rupture. The maximum pseudo-spectrum of high-frequency P wave in a sequence of time windows recorded by the densely-distributed stations from US and EU Array are used to image 3-D temporal and spatial rupture distribution. The resulting image confirms that the nearly N-S striking but two antiparallel rupture stages. The first subhorizontal rupture initially propagates toward the NNE direction, while at 18 s later it directs reversely to the SSW and concurrently shifts downward to 35 km deeper lasting for about 20 s. The rupture lengths in the first NNE-ward and second SSW-ward stage are about 30 km and 85 km; the estimated rupture velocities are 3 km/s and 4.25 km/s, respectively. Synthetic experiments are undertaken to assess the capability of the 3D MUSIC BP for the recovery of spatio-temporal rupture processes. Besides, high frequency BP images based on the EU-Array data show two M6.7 aftershocks are more likely to rupture on the vertical fault planes.

  2. The Aftershock Sequence of the 2008 Achaia, Greece, Earthquake: Joint Analysis of Seismicity Relocation and Persistent Scatterers Interferometry

    NASA Astrophysics Data System (ADS)

    Karakostas, Vassilis; Mirek, Katarzyna; Mesimeri, Maria; Papadimitriou, Eleftheria; Mirek, Janusz

    2016-08-01

    On 8 June 2008 an earthquake of Mw6.4 took place in the northwestern part of Peloponnese, Greece. The main shock was felt in a wide area and caused appreciable damage along the main rupture area and particularly at the antipodal of the main shock epicenter fault edge, implying strongly unilateral rupture and stopping phase effects. Abundant aftershocks were recorded within an area of ~50 km in length in the period 8 June 2008-end of 2014, by a sufficient number of stations that secure location accuracy because the regional network is adequately dense in the area. All the available phases from seismological stations in epicentral distances up to 140 km until the end of 2014 were used for relocation with the double difference technique and waveform cross-correlation. A quite clear 3-D representation is obtained for the aftershock zone geometry and dimensions, revealing the main rupture and the activated adjacent fault segments. SAR data are processed using Stanford Method for Persistent Scatterers (StaMPS) and a surface deformation map constructed based on PS point displacement for the coseismic period. A variable slip model, with maximum slip of ~1.0 m located at the lower part of the rupture plane, is suggested and used for calculating the deformation field which was found in adequate agreement with geodetic measurements. With the same slip model the static stress changes were calculated evidencing possible triggering of the neighboring faults that were brought closer to failure. The data availability allowed monitoring the temporal variation of b values that after a continuous increase in the first 5 days, returned and stabilized to 1.0-1.1 in the following years. The fluctuation duration is considered as the equivalent time for fault healing, which appeared very short but in full accordance with the cessation of onto-fault seismicity.

  3. Model for the Distribution of Aftershock Interoccurrence Times

    SciTech Connect

    Shcherbakov, Robert; Yakovlev, Gleb; Rundle, John B.; Turcotte, Donald L.

    2005-11-18

    In this work the distribution of interoccurrence times between earthquakes in aftershock sequences is analyzed and a model based on a nonhomogeneous Poisson (NHP) process is proposed to quantify the observed scaling. In this model the generalized Omori's law for the decay of aftershocks is used as a time-dependent rate in the NHP process. The analytically derived distribution of interoccurrence times is applied to several major aftershock sequences in California to confirm the validity of the proposed hypothesis.

  4. Model for the distribution of aftershock interoccurrence times.

    PubMed

    Shcherbakov, Robert; Yakovlev, Gleb; Turcotte, Donald L; Rundle, John B

    2005-11-18

    In this work the distribution of interoccurrence times between earthquakes in aftershock sequences is analyzed and a model based on a nonhomogeneous Poisson (NHP) process is proposed to quantify the observed scaling. In this model the generalized Omori's law for the decay of aftershocks is used as a time-dependent rate in the NHP process. The analytically derived distribution of interoccurrence times is applied to several major aftershock sequences in California to confirm the validity of the proposed hypothesis.

  5. Systematic Changes Of Earthquake Rupture With Depth: A Case Study From The 2010 Mw 8.8 Maule, Chile, Earthquake Aftershock Sequence

    NASA Astrophysics Data System (ADS)

    Tolga Şen, Ali; Cesca, Simone; Heimann, Sebastian; Lange, Dietrich; Dahm, Torsten; Tilmann, Frederik

    2015-04-01

    The very shallow part of subduction megathrusts occasionally hosts tsunami earthquakes, with unusually slow rupture propagation. The aftershock sequence of the 2010 MW8.8 Maule earthquake, offshore Chile, provides us with the opportunity to study systematic changes in source properties for smaller earthquakes within a single segment of a subduction zone. We invert amplitude spectra for double couple moment tensors and centroid depths of 71 aftershocks of the Maule earthquake down to magnitudes MW 4.0 and 6.8. In addition, we also derive average source durations. Depending on the availability of data from a 130 broadband station temporary array, we employ two modelling schemes optimised for regional and teleseismic data. The resulting focal mechanisms highlight the correlation of the fault planes thrust earthquakes with the 3D slab model geometry in the area, and the occurrence of normal faulting earthquakes on a crustal fault system in the northernmost part of the study area. We find that shallower earthquakes tend to have longer normalized source durations on average, similar to the pattern observed previously for larger magnitude events. The normalised source durations of normal faulting earthquakes are at the lower end of those for thrust earthquakes, probably because of the higher stress drops of intraplate earthquakes compared to interplate earthquakes. Notably, a similar depth dependence is observable for thrust and normal earthquakes. We tentatively conclude from the similarity of the depth dependence of normal and thrust events and between smaller and larger magnitude earthquakes that the depth-dependent variation of rigidity is primarily responsible for the observed pattern rather than frictional conditional stability at the plate interface Tsunami earthquakes probably require both low rigidity and conditionally stable frictional conditions; the presence of long duration moderate magnitude events is therefore a helpful but not sufficient indicator for

  6. Static stress transfer modeling and aftershock statistics for the 2002 Nenana Mountain-Denali Park, Alaska, sequence

    NASA Astrophysics Data System (ADS)

    Anderson, G.; Jones, L. M.; Ji, C.

    2002-12-01

    On October 23, 2002, the Mw 6.7 Nenana Mountain earthquake occurred in central Alaska. While this was a significant event, it became even more interesting as a foreshock to the Mw 7.9 Denali Park mainshock of November 3, 2002, which was the largest earthquake to occur on land in the United States since the 1857 Fort Tejon earthquake in southern California. Using a finite-fault rupture model and the theory of deformation from dislocations in an elastic half-space, we have modeled static Coulomb stress transfer from the Nenana Mountain event to the hypocentral region of the Denali Park event and find that the Nenana Mountain event transferred about 0.05--0.1 MPa (0.5--1 bar) of Coulomb stress to that area, encouraging failure of the later event. We have also computed the combined stress transferred to several large regional faults from the Nenana Mountain and Denali Park events using our Nenana Mountain and Denali Park rupture models. We find that the two main events combined transferred more than 0.05 MPa (0.5 bar) of Coulomb stress to the northern 50 km of the Cross Creek fault, a 150-km-long right-lateral strike slip fault in east-central Alaska, and up to 0.05 MPa of Coulomb stress to the Muldrow segment of the Denali fault, west of the Nenana Mountain rupture. It is worth noting, however, that these faults are nearest to the mainshock rupture and thus most prone to errors in the stress transfer modeling. Other major faults in the region, including the Tonzona, Farewell, and Boss Creek segments of the Denali fault, the Castle Mountain fault near Anchorage, and the Yakataga subduction interface, experienced insignificant static Coulomb stress changes, though dynamic stresses were probably much larger. Although the stress changes from these events are significant, the rates of aftershocks triggered by the Nenana Mountain foreshock and by the Denali Park mainshock are extremely low. We describe the rate of aftershocks with the Reasenberg and Jones formulation for

  7. 2010 Chile Earthquake Aftershock Response

    NASA Astrophysics Data System (ADS)

    Barientos, Sergio

    2010-05-01

    The Mw=8.8 earthquake off the coast of Chile on 27 February 2010 is the 5th largest megathrust earthquake ever to be recorded and provides an unprecedented opportunity to advance our understanding of megathrust earthquakes and associated phenomena. The 2010 Chile earthquake ruptured the Concepcion-Constitucion segment of the Nazca/South America plate boundary, south of the Central Chile region and triggered a tsunami along the coast. Following the 2010 earthquake, a very energetic aftershock sequence is being observed in an area that is 600 km along strike from Valparaiso to 150 km south of Concepcion. Within the first three weeks there were over 260 aftershocks with magnitude 5.0 or greater and 18 with magnitude 6.0 or greater (NEIC, USGS). The Concepcion-Constitucion segment lies immediately north of the rupture zone associated with the great magnitude 9.5 Chile earthquake, and south of the 1906 and the 1985 Valparaiso earthquakes. The last great subduction earthquake in the region dates back to the February 1835 event described by Darwin (1871). Since 1835, part of the region was affected in the north by the Talca earthquake in December 1928, interpreted as a shallow dipping thrust event, and by the Chillan earthquake (Mw 7.9, January 1939), a slab-pull intermediate depth earthquake. For the last 30 years, geodetic studies in this area were consistent with a fully coupled elastic loading of the subduction interface at depth; this led to identify the area as a mature seismic gap with potential for an earthquake of magnitude of the order 8.5 or several earthquakes of lesser magnitude. What was less expected was the partial rupturing of the 1985 segment toward north. Today, the 2010 earthquake raises some disturbing questions: Why and how the rupture terminated where it did at the northern end? How did the 2010 earthquake load the adjacent segment to the north and did the 1985 earthquake only partially ruptured the plate interface leaving loaded asperities since

  8. Statistical Properties of Mine Tremor Aftershocks

    NASA Astrophysics Data System (ADS)

    Kgarume, T. E.; Spottiswoode, S. M.; Durrheim, R. J.

    2010-02-01

    Mine tremors and their aftershocks pose a risk to mine workers in the deep gold mines of South Africa. The statistical properties of mine-tremor aftershocks were investigated as part of an endeavour to assess the hazard and manage the risk. Data from two gold mines in the Carletonville mining district were used in the analysis. Main shocks were aligned in space and time and the aftershock sequences stacked and analysed. The aftershocks were found to satisfy Gutenberg-Richter scaling, with a b value close to 1. Aftershock activity diminished with time in accordance with the modified Omori law, with p values close to 1. However, the relationship between the main shock and its biggest aftershock violated Båths law, with Δ M L ≈ 1.9 for main shocks with M L < 3 and increasing for main shocks with M L > 3. The aftershock density was found to fall-off with distance as r -1.3, suggesting triggering by dynamic stress.

  9. Recent Experiences in Aftershock Hazard Modelling in New Zealand

    NASA Astrophysics Data System (ADS)

    Gerstenberger, M.; Rhoades, D. A.; McVerry, G.; Christophersen, A.; Bannister, S. C.; Fry, B.; Potter, S.

    2014-12-01

    The occurrence of several sequences of earthquakes in New Zealand in the last few years has meant that GNS Science has gained significant recent experience in aftershock hazard and forecasting. First was the Canterbury sequence of events which began in 2010 and included the destructive Christchurch earthquake of February, 2011. This sequence is occurring in what was a moderate-to-low hazard region of the National Seismic Hazard Model (NSHM): the model on which the building design standards are based. With the expectation that the sequence would produce a 50-year hazard estimate in exceedance of the existing building standard, we developed a time-dependent model that combined short-term (STEP & ETAS) and longer-term (EEPAS) clustering with time-independent models. This forecast was combined with the NSHM to produce a forecast of the hazard for the next 50 years. This has been used to revise building design standards for the region and has contributed to planning of the rebuilding of Christchurch in multiple aspects. An important contribution to this model comes from the inclusion of EEPAS, which allows for clustering on the scale of decades. EEPAS is based on three empirical regressions that relate the magnitudes, times of occurrence, and locations of major earthquakes to regional precursory scale increases in the magnitude and rate of occurrence of minor earthquakes. A second important contribution comes from the long-term rate to which seismicity is expected to return in 50-years. With little seismicity in the region in historical times, a controlling factor in the rate is whether-or-not it is based on a declustered catalog. This epistemic uncertainty in the model was allowed for by using forecasts from both declustered and non-declustered catalogs. With two additional moderate sequences in the capital region of New Zealand in the last year, we have continued to refine our forecasting techniques, including the use of potential scenarios based on the aftershock

  10. The aftershock processes of strong earthquakes in the Western Caucasus

    NASA Astrophysics Data System (ADS)

    Baranov, S. V.; Gabsatarova, I. P.

    2015-05-01

    The aftershock processes of the four strong earthquakes that occurred in the Western Caucasus from 1991 to June 2013 are considered. The main shocks of these earthquakes include the first Racha earthquake (April 29, 1991, Ms = 6.9); second Racha earthquake (June 15, 1991, Ms = 6.2); Oni earthquake (September 7, 2009, Ms = 5.8); and East Black Sea earthquake (December 23, 2012, Ms = 5.6). Based on the simulations with the LPL relaxation model and the ETAS model of triggered seismicity, the differences in the properties of the aftershock processes and the characteristics of the fault zones accommodating the main shocks are revealed. The nonrelaxation character of the aftershocks from the East Black Sea earthquake is established. It is hypothesized and validated that this is a result of the violation of the fluid-dynamic equilibrium in the fault zone due to the destruction of the gas hydrate layer by the main shock and strong aftershocks.

  11. Mechanism diversity of the loma prieta aftershocks and the mechanics of mainshock-aftershock interaction.

    PubMed

    Beroza, G C; Zoback, M D

    1993-01-01

    The diverse aftershock sequence of the 1989 Loma Prieta earthquake is inconsistent with conventional models of mainshock-aftershock interaction because the aftershocks do not accommodate mainshock-induced stress changes. Instead, the sense of slip of the aftershocks is consistent with failure in response to a nearly uniaxial stress field in which the maximum principal stress acts almost normal to the mainshock fault plane. This orientation implies that (i) stress drop in the mainshock was nearly complete, (ii) mainshock-induced decreases of fault strength helped were important in controlling the occurrence of after-shocks, and (iii) mainshock rupture was limited to those sections of the fault with preexisting shear stress available to drive fault slip.

  12. Asymmetric Earthquake Aftershock Distributions Resulting from Timing Within the Seismic Cycle

    NASA Astrophysics Data System (ADS)

    McGuire, J. J.; Collins, J. A.; Boettcher, M. S.; Roland, E. C.

    2010-12-01

    Aftershock sequences are a well documented result of changes in the crustal stress-field resulting from nearby large earthquakes, yet there is typically little (or no) constraint on the initial stress level of the “receiver fault” where the triggered aftershock occurs. Thus, many popular physical and stochastic models of aftershock triggering do not account for the absolute stress-level on a receiver fault, and the importance of this stress level (relative to a fault’s failure threshold) is not easily studied. In 2008 we recorded a series of westward propagating ruptures that marked the end of the most recent seismic cycle on the Gofar transform fault using an array of Ocean Bottom Seismometers (OBSs). The end of the 2002-2008 seismic cycle on the Gofar fault included a series of 4 major rupture events (either M6 earthquakes or large seismic swarms) that propagated ~90 km along the strike of the fault from east to west over the course of 1.5 years. Our OBS dataset covered the last 3 of these events and recorded over 200,000 microearthquakes. Each of the 3 rupture events produced a spatially asymmetric aftershock distribution. On the eastern side of each slipping zone, where the stress is lower because the fault has already ruptured in its cycle-ending event, the large rupture events do not change the seismicity-rate. In contrast, on the western side, where stress is high because the area is nearing the end of it’s seismic cycle, there is a clear increase in seismicity rate (i.e. aftershocks). This asymmetry demonstrates the importance of absolute stress-levels in earthquake triggering. This observation contrasts with the Rate-State seismicity model (Dieterich, 1994), which predicts that seismicity-rate increases will depend only on stressing-rate and the magnitude of a static stress change. Since static stress changes from large ruptures are fairly symmetric along a geometrically simple strike slip fault, like Gofar, the observed aftershock asymmetry

  13. Aftershock Energy Distribution by Statistical Mechanics Approach

    NASA Astrophysics Data System (ADS)

    Daminelli, R.; Marcellini, A.

    2015-12-01

    The aim of our work is to research the most probable distribution of the energy of aftershocks. We started by applying one of the fundamental principles of statistical mechanics that, in case of aftershock sequences, it could be expressed as: the greater the number of different ways in which the energy of aftershocks can be arranged among the energy cells in phase space the more probable the distribution. We assume that each cell in phase space has the same possibility to be occupied, and that more than one cell in the phase space can have the same energy. Seeing that seismic energy is proportional to products of different parameters, a number of different combinations of parameters can produce different energies (e.g., different combination of stress drop and fault area can release the same seismic energy). Let us assume that there are gi cells in the aftershock phase space characterised by the same energy released ɛi. Therefore we can assume that the Maxwell-Boltzmann statistics can be applied to aftershock sequences with the proviso that the judgment on the validity of this hypothesis is the agreement with the data. The aftershock energy distribution can therefore be written as follow: n(ɛ)=Ag(ɛ)exp(-βɛ)where n(ɛ) is the number of aftershocks with energy, ɛ, A and β are constants. Considering the above hypothesis, we can assume g(ɛ) is proportional to ɛ. We selected and analysed different aftershock sequences (data extracted from Earthquake Catalogs of SCEC, of INGV-CNT and other institutions) with a minimum magnitude retained ML=2 (in some cases ML=2.6) and a time window of 35 days. The results of our model are in agreement with the data, except in the very low energy band, where our model resulted in a moderate overestimation.

  14. Aftershock Characteristics as a Means of Discriminating Explosions from Earthquakes

    SciTech Connect

    Ford, S R; Walter, W R

    2009-05-20

    The behavior of aftershock sequences around the Nevada Test Site in the southern Great Basin is characterized as a potential discriminant between explosions and earthquakes. The aftershock model designed by Reasenberg and Jones (1989, 1994) allows for a probabilistic statement of earthquake-like aftershock behavior at any time after the mainshock. We use this model to define two types of aftershock discriminants. The first defines M{sub X}, or the minimum magnitude of an aftershock expected within a given duration after the mainshock with probability X. Of the 67 earthquakes with M > 4 in the study region, 63 of them produce an aftershock greater than M{sub 99} within the first seven days after a mainshock. This is contrasted with only six of 93 explosions with M > 4 that produce an aftershock greater than M{sub 99} for the same period. If the aftershock magnitude threshold is lowered and the M{sub 90} criteria is used, then no explosions produce an aftershock greater than M{sub 90} for durations that end more than 17 days after the mainshock. The other discriminant defines N{sub X}, or the minimum cumulative number of aftershocks expected for given time after the mainshock with probability X. Similar to the aftershock magnitude discriminant, five earthquakes do not produce more aftershocks than N{sub 99} within 7 days after the mainshock. However, within the same period all but one explosion produce less aftershocks then N{sub 99}. One explosion is added if the duration is shortened to two days after than mainshock. The cumulative number aftershock discriminant is more reliable, especially at short durations, but requires a low magnitude of completeness for the given earthquake catalog. These results at NTS are quite promising and should be evaluated at other nuclear test sites to understand the effects of differences in the geologic setting and nuclear testing practices on its performance.

  15. Eta Aquarids

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    A meteor shower that takes place in late April and May. The radiant lies in the constellation Aquarius. The Eta Aquarids occur when the Earth intersects the descending node of the meteor stream from Halley's Comet; the Orionids in October are produced by the Earth's passage through the ascending node. Because Halley's orbit is retrograde, Eta Aquarid meteoroids impact the Earth at a high relative...

  16. Bayesian Predictive Distribution for the Magnitude of the Largest Aftershock

    NASA Astrophysics Data System (ADS)

    Shcherbakov, R.

    2014-12-01

    Aftershock sequences, which follow large earthquakes, last hundreds of days and are characterized by well defined frequency-magnitude and spatio-temporal distributions. The largest aftershocks in a sequence constitute significant hazard and can inflict additional damage to infrastructure. Therefore, the estimation of the magnitude of possible largest aftershocks in a sequence is of high importance. In this work, we propose a statistical model based on Bayesian analysis and extreme value statistics to describe the distribution of magnitudes of the largest aftershocks in a sequence. We derive an analytical expression for a Bayesian predictive distribution function for the magnitude of the largest expected aftershock and compute the corresponding confidence intervals. We assume that the occurrence of aftershocks can be modeled, to a good approximation, by a non-homogeneous Poisson process with a temporal event rate given by the modified Omori law. We also assume that the frequency-magnitude statistics of aftershocks can be approximated by Gutenberg-Richter scaling. We apply our analysis to 19 prominent aftershock sequences, which occurred in the last 30 years, in order to compute the Bayesian predictive distributions and the corresponding confidence intervals. In the analysis, we use the information of the early aftershocks in the sequences (in the first 1, 10, and 30 days after the main shock) to estimate retrospectively the confidence intervals for the magnitude of the expected largest aftershocks. We demonstrate by analysing 19 past sequences that in many cases we are able to constrain the magnitudes of the largest aftershocks. For example, this includes the analysis of the Darfield (Christchurch) aftershock sequence. The proposed analysis can be used for the earthquake hazard assessment and forecasting associated with the occurrence of large aftershocks. The improvement in instrumental data associated with early aftershocks can greatly enhance the analysis and

  17. Mechanical origin of aftershocks.

    PubMed

    Lippiello, E; Giacco, F; Marzocchi, W; Godano, C; de Arcangelis, L

    2015-01-01

    Aftershocks are the most striking evidence of earthquake interactions and the physical mechanisms at the origin of their occurrence are still intensively debated. Novel insights stem from recent results on the influence of the faulting style on the aftershock organisation in magnitude and time. Our study shows that the size of the aftershock zone depends on the fault geometry. We find that positive correlations among parameters controlling aftershock occurrence in time, energy and space are a stable feature of seismicity independently of magnitude range and geographic areas. We explain the ensemble of experimental findings by means of a description of the Earth Crust as an heterogeneous elastic medium coupled with a Maxwell viscoelastic asthenosphere. Our results show that heterogeneous stress distribution in an elastic layer combined with a coupling to a viscous flow are sufficient ingredients to describe the physics of aftershock triggering. PMID:26497720

  18. Mechanical origin of aftershocks.

    PubMed

    Lippiello, E; Giacco, F; Marzocchi, W; Godano, C; de Arcangelis, L

    2015-10-26

    Aftershocks are the most striking evidence of earthquake interactions and the physical mechanisms at the origin of their occurrence are still intensively debated. Novel insights stem from recent results on the influence of the faulting style on the aftershock organisation in magnitude and time. Our study shows that the size of the aftershock zone depends on the fault geometry. We find that positive correlations among parameters controlling aftershock occurrence in time, energy and space are a stable feature of seismicity independently of magnitude range and geographic areas. We explain the ensemble of experimental findings by means of a description of the Earth Crust as an heterogeneous elastic medium coupled with a Maxwell viscoelastic asthenosphere. Our results show that heterogeneous stress distribution in an elastic layer combined with a coupling to a viscous flow are sufficient ingredients to describe the physics of aftershock triggering.

  19. Mechanical origin of aftershocks

    PubMed Central

    Lippiello, E.; Giacco, F.; Marzocchi, W.; Godano, C.; de Arcangelis, L.

    2015-01-01

    Aftershocks are the most striking evidence of earthquake interactions and the physical mechanisms at the origin of their occurrence are still intensively debated. Novel insights stem from recent results on the influence of the faulting style on the aftershock organisation in magnitude and time. Our study shows that the size of the aftershock zone depends on the fault geometry. We find that positive correlations among parameters controlling aftershock occurrence in time, energy and space are a stable feature of seismicity independently of magnitude range and geographic areas. We explain the ensemble of experimental findings by means of a description of the Earth Crust as an heterogeneous elastic medium coupled with a Maxwell viscoelastic asthenosphere. Our results show that heterogeneous stress distribution in an elastic layer combined with a coupling to a viscous flow are sufficient ingredients to describe the physics of aftershock triggering. PMID:26497720

  20. A Fluid-driven Earthquake Cycle, Omori's Law, and Fluid-driven Aftershocks

    NASA Astrophysics Data System (ADS)

    Miller, S. A.

    2015-12-01

    Few models exist that predict the Omori's Law of aftershock rate decay, with rate-state friction the only physically-based model. ETAS is a probabilistic model of cascading failures, and is sometimes used to infer rate-state frictional properties. However, the (perhaps dominant) role of fluids in the earthquake process is being increasingly realised, so a fluid-based physical model for Omori's Law should be available. In this talk, I present an hypothesis for a fluid-driven earthquake cycle where dehydration and decarbonization at depth provides continuous sources of buoyant high pressure fluids that must eventually make their way back to the surface. The natural pathway for fluid escape is along plate boundaries, where in the ductile regime high pressure fluids likely play an integral role in episodic tremor and slow slip earthquakes. At shallower levels, high pressure fluids pool at the base of seismogenic zones, with the reservoir expanding in scale through the earthquake cycle. Late in the cycle, these fluids can invade and degrade the strength of the brittle crust and contribute to earthquake nucleation. The mainshock opens permeable networks that provide escape pathways for high pressure fluids and generate aftershocks along these flow paths, while creating new pathways by the aftershocks themselves. Thermally activated precipitation then seals up these pathways, returning the system to a low-permeability environment and effective seal during the subsequent tectonic stress buildup. I find that the multiplicative effect of an exponential dependence of permeability on the effective normal stress coupled with an Arrhenius-type, thermally activated exponential reduction in permeability results in Omori's Law. I simulate this scenario using a very simple model that combines non-linear diffusion and a step-wise increase in permeability when a Mohr Coulomb failure condition is met, and allow permeability to decrease as an exponential function in time. I show very

  1. A Jurassic Shock-Aftershock Earthquake Sequence Recorded by Small Clastic Pipes and Dikes within Dune Cross-Strata, Zion National Park, Utah

    NASA Astrophysics Data System (ADS)

    Loope, D. B.; Zlotnik, V. A.; Kettler, R. M.; Pederson, D. T.

    2012-12-01

    dune lee slope through a pipe, the erupted sand dried and was buried by climbing wind-ripple strata as the large dune continued to advance downwind. The mapped cluster recording eight distinct seismic events lies within thin-laminated sediment that was deposited by wind ripples during 1 m (~ 1 year) of southeastward dune migration. We conclude that the small pipes and dikes of our study sites are products of numerous >MM 5 earthquakes, some of which recurred at intervals of less than 2 months. We interpret one small cluster of pipes and dikes with well-defined upward terminations as a distinct shock-aftershock sequence. Because the largest modern earthquakes can produce surface liquefaction only up to about 175 km from their epicenters, the Jurassic epicenters must have been well within that distance. The tendency of modern plate boundaries to produce high-frequency aftershocks suggests that the epicenter for this Jurassic sequence lay to the southwest, within the plate boundary zone (not within continental rocks to the east). As eolian dunes steadily migrate over interdune surfaces underlain by water-saturated dune cross-strata, the thin, distinct laminae produced by the wind ripples that occupy dune toes can faithfully record high-frequency seismic events.

  2. Comparison of the non-proliferation event aftershocks with other Nevada Test Site events

    SciTech Connect

    Jarpe, S.; Goldstein, P.; Zucca, J.J.

    1994-04-01

    As part of a larger effort to develop technology for on-site inspection of ambiguous underground seismic events, we have been working to identify phenomenology of aftershock seismicity which would be useful for discriminating between nuclear explosions, chemical explosions, earthquakes or other seismic events. Phenomenology we have investigated includes; the spatial distribution of aftershocks, the number of aftershocks as a function of time after the main event, the size of the aftershocks, and waveform frequency content. Our major conclusions are: (1) Depending on local geologic conditions, aftershock production rate two weeks after zero time ranges from 1 to 100 per day. (2) Aftershocks of concentrated chemical explosions such as the NPE are indistinguishable from aftershocks of nuclear explosions. (3) Earthquake and explosion aftershock sequences may be differentiated on the basis of depth, magnitude, and in some cases, frequency content of seismic signals.

  3. Scale-free networks of earthquakes and aftershocks.

    PubMed

    Baiesi, Marco; Paczuski, Maya

    2004-06-01

    We propose a metric to quantify correlations between earthquakes. The metric consists of a product involving the time interval and spatial distance between two events, as well as the magnitude of the first one. According to this metric, events typically are strongly correlated to only one or a few preceding ones. Thus a classification of events as foreshocks, main shocks, or aftershocks emerges automatically without imposing predetermined space-time windows. In the simplest network construction, each earthquake receives an incoming link from its most correlated predecessor. The number of aftershocks for any event, identified by its outgoing links, is found to be scale free with exponent gamma=2.0(1). The original Omori law with p=1 emerges as a robust feature of seismicity, holding up to years even for aftershock sequences initiated by intermediate magnitude events. The broad distribution of distances between earthquakes and their linked aftershocks suggests that aftershock collection with fixed space windows is not appropriate.

  4. The M w6.7 12 October 2013 western Hellenic Arc main shock and its aftershock sequence: implications for the slab properties

    NASA Astrophysics Data System (ADS)

    Papadimitriou, Eleftheria; Karakostas, Vassilis; Mesimeri, Maria; Vallianatos, Filippos

    2016-01-01

    The 12 October 2013 M w6.7 earthquake offshore Crete Island is one of the few strong earthquakes to have occurred in the last few decades in the southwestern part of the Hellenic subduction zone (HSZ), providing the opportunity to evaluate characteristics of the descending slab. The HSZ has experienced several strong (M ≥ 7.0) earthquakes in historical times with the largest one being the 365 AD, M w = 8.4 earthquake, the largest known ever occurred in the Mediterranean region. The 2013 main shock occurred in close proximity with the 365 event, on an interplate thrust fault at a depth of 26 km, onto the coupled part of the overriding and descending plates. GCMT solution shows a slightly oblique (rake = 130°) thrust faulting with downdip compression on a nearly horizontal (dip = 3°) northeast-dipping fault plane with strike (340°) parallel to the subduction front, with the compression axis being oriented in the direction of plate convergence. The subduction interface can be more clearly resolved with the integration of aftershock locations and CMT solution. For this scope, the aftershocks were relocated after obtaining a v p/v s ratio equal to 1.76, a one-dimensional velocity model and time delays that approximate the velocity structure of the study area, and the employment of double-difference technique for both phase pick data and cross-correlation differential times. The first-day relocated seismicity, alike aftershocks in the first 2 months, shows activation of an area at the upper part of the descending slab, with most activity being concentrated between 13 and 27 km, where the main shock is also encompassed. Aftershocks are rare near to the main shock, implying homogeneous slip on a large patch of the rupture plane. Based on the aftershock distribution, the size of the activated area estimated is about 24 km long and 17 km wide. Coulomb stress changes resolved for transpressive motion reveal negligible off-fault aftershock triggering, evidencing a

  5. The M w6.7 12 October 2013 western Hellenic Arc main shock and its aftershock sequence: implications for the slab properties

    NASA Astrophysics Data System (ADS)

    Papadimitriou, Eleftheria; Karakostas, Vassilis; Mesimeri, Maria; Vallianatos, Filippos

    2016-10-01

    The 12 October 2013 M w6.7 earthquake offshore Crete Island is one of the few strong earthquakes to have occurred in the last few decades in the southwestern part of the Hellenic subduction zone (HSZ), providing the opportunity to evaluate characteristics of the descending slab. The HSZ has experienced several strong ( M ≥ 7.0) earthquakes in historical times with the largest one being the 365 AD, M w = 8.4 earthquake, the largest known ever occurred in the Mediterranean region. The 2013 main shock occurred in close proximity with the 365 event, on an interplate thrust fault at a depth of 26 km, onto the coupled part of the overriding and descending plates. GCMT solution shows a slightly oblique (rake = 130°) thrust faulting with downdip compression on a nearly horizontal (dip = 3°) northeast-dipping fault plane with strike (340°) parallel to the subduction front, with the compression axis being oriented in the direction of plate convergence. The subduction interface can be more clearly resolved with the integration of aftershock locations and CMT solution. For this scope, the aftershocks were relocated after obtaining a v p/ v s ratio equal to 1.76, a one-dimensional velocity model and time delays that approximate the velocity structure of the study area, and the employment of double-difference technique for both phase pick data and cross-correlation differential times. The first-day relocated seismicity, alike aftershocks in the first 2 months, shows activation of an area at the upper part of the descending slab, with most activity being concentrated between 13 and 27 km, where the main shock is also encompassed. Aftershocks are rare near to the main shock, implying homogeneous slip on a large patch of the rupture plane. Based on the aftershock distribution, the size of the activated area estimated is about 24 km long and 17 km wide. Coulomb stress changes resolved for transpressive motion reveal negligible off-fault aftershock triggering, evidencing a

  6. Some facts about aftershocks to large earthquakes in California

    USGS Publications Warehouse

    Jones, Lucile M.; Reasenberg, Paul A.

    1996-01-01

    Earthquakes occur in clusters. After one earthquake happens, we usually see others at nearby (or identical) locations. To talk about this phenomenon, seismologists coined three terms foreshock , mainshock , and aftershock. In any cluster of earthquakes, the one with the largest magnitude is called the mainshock; earthquakes that occur before the mainshock are called foreshocks while those that occur after the mainshock are called aftershocks. A mainshock will be redefined as a foreshock if a subsequent event in the cluster has a larger magnitude. Aftershock sequences follow predictable patterns. That is, a sequence of aftershocks follows certain global patterns as a group, but the individual earthquakes comprising the group are random and unpredictable. This relationship between the pattern of a group and the randomness (stochastic nature) of the individuals has a close parallel in actuarial statistics. We can describe the pattern that aftershock sequences tend to follow with well-constrained equations. However, we must keep in mind that the actual aftershocks are only probabilistically described by these equations. Once the parameters in these equations have been estimated, we can determine the probability of aftershocks occurring in various space, time and magnitude ranges as described below. Clustering of earthquakes usually occurs near the location of the mainshock. The stress on the mainshock's fault changes drastically during the mainshock and that fault produces most of the aftershocks. This causes a change in the regional stress, the size of which decreases rapidly with distance from the mainshock. Sometimes the change in stress caused by the mainshock is great enough to trigger aftershocks on other, nearby faults. While there is no hard "cutoff" distance beyond which an earthquake is totally incapable of triggering an aftershock, the vast majority of aftershocks are located close to the mainshock. As a rule of thumb, we consider earthquakes to be

  7. Retrospective forecast of ETAS model with daily parameters estimate

    NASA Astrophysics Data System (ADS)

    Falcone, Giuseppe; Murru, Maura; Console, Rodolfo; Marzocchi, Warner; Zhuang, Jiancang

    2016-04-01

    We present a retrospective ETAS (Epidemic Type of Aftershock Sequence) model based on the daily updating of free parameters during the background, the learning and the test phase of a seismic sequence. The idea was born after the 2011 Tohoku-Oki earthquake. The CSEP (Collaboratory for the Study of Earthquake Predictability) Center in Japan provided an appropriate testing benchmark for the five 1-day submitted models. Of all the models, only one was able to successfully predict the number of events that really happened. This result was verified using both the real time and the revised catalogs. The main cause of the failure was in the underestimation of the forecasted events, due to model parameters maintained fixed during the test. Moreover, the absence in the learning catalog of an event similar to the magnitude of the mainshock (M9.0), which drastically changed the seismicity in the area, made the learning parameters not suitable to describe the real seismicity. As an example of this methodological development we show the evolution of the model parameters during the last two strong seismic sequences in Italy: the 2009 L'Aquila and the 2012 Reggio Emilia episodes. The achievement of the model with daily updated parameters is compared with that of same model where the parameters remain fixed during the test time.

  8. The Prediction of Spatial Aftershock Probabilities (PRESAP)

    NASA Astrophysics Data System (ADS)

    McCloskey, J.

    2003-12-01

    extent to which this is scientifically feasible in terms of our understanding of the physical phenomena which control the variation of seismicity following a large event due to stress redistribution and practically possible given present limitations on data availability, data quality and computational or data transfer speeds. The project is divided into a number of elements designed to reflect the temporal sequence of tasks that must be undertaken for the prediction of aftershock hazard. These tasks include determining a time-indexed sequence of slip distributions for both real and synthetic events, calculating a suite of time-indexed stress perturbations and quantitatively comprising predicted and observed aftershock distributions, and developing techniques for predicting likely strong ground motion from the predicted spatial distribution of aftershocks.

  9. Aftershocks can Significantly Alter Stress Change Patterns Produced by Their Mainshock

    NASA Astrophysics Data System (ADS)

    Felzer, K. R.; Becker, T. W.; Abercrombie, R. E.; Ekström, G.; Rice, J. R.

    2001-12-01

    Many studies over the last decade have used the static Coulomb stress change produced by a mainshock to predict the locations of triggered earthquakes. This method has shown some success, but often fails to predict the locations of 20% to 40% of the aftershocks of a given mainshock. We use statistical Monte Carlo modeling to show that this amount of failure is consistent with the perturbation to the stress field provided by the aftershocks themselves. Although most aftershocks are more than a magnitude unit smaller than their mainshocks, the ability of earthquakes of all magnitudes to produce large static stress changes at short range, and the pronounced clustering of aftershock hypocenters, implies that many aftershock hypocenters in a sequence may be primarily stressed by a previous aftershock rather than by the mainshock itself. The exact percentage stressed by previous aftershocks increases with the activity of the aftershock sequence, the magnitude of the mainshock, and the time since the mainshock. Our model predicts that two days after the average California M7 earthquake, for example, over 50% of new aftershocks are primarily in response to stress changes from previous aftershocks. This means that the majority of the new aftershocks are most likely to occur near previous aftershocks, and not necessarily within regions of Coulomb stress increase from the mainshock. The same happens three days after the average M6, and three weeks after the average M5 mainshock. Our statistical modeling uses Omori's Law for aftershock decay, the Gutenberg-Richter magnitude frequency relationship, Baath's Law, and the assumptions that earthquakes of all sizes are capable of generating aftershocks and that the timing of each aftershock is essentially determined by a single mainshock. We apply our model to the 1999 M7.1 Hector Mine earthquake, which may be classified as an aftershock of the 1992 M7.3 Landers earthquake. Our modeling shows that at the time of the Hector Mine

  10. Aftershock Decay Rates in the Iranian Plateau

    NASA Astrophysics Data System (ADS)

    Ommi, S.; Zafarani, H.; Zare, M.

    2016-07-01

    Motivated by the desire to have more information following the occurrence of damaging events, the main purpose of this article is to study aftershock sequence parameters in the Iranian plateau. To this end, the catalogue of the Iranian earthquakes between 2002 to the end of 2013 has been collected and homogenized among which 15 earthquakes have been selected to study their aftershock decay rates. For different tectonic provinces, the completeness magnitudes ( M c) of the earthquake catalogue have been calculated in different time intervals. Also, the M c variability in spatial and temporal windows has been determined for each selected event. For major Iranian earthquakes, catalogue of aftershocks has been collected thanks to three declustering methods: first, the classical windowing method of Gardner and Knopoff (Bull Seismol Soc Am 64:1363-1367, 1974); second, a modified version of this using spatial windowing based on the Wells and Coppersmith (Bull Seismol Soc Am 84:974-1002, 1994) relations; and third, the Burkhard and Grünthal (Swiss J Geosci 102:149-188, 2009) scheme. Effects of the temporal windows also have been investigated using the time periods of 1 month, 100 days, and 1 year in the declustering method of Gardner and Knopoff (Bull Seismol Soc Am 64:1363-1367, 1974). In the next step, the modified Omori law coefficients have been calculated for the 15 selected earthquakes. The calibrated regional generic model describing the temporal and magnitude distribution of aftershocks is of interest for time-dependent seismic hazard forecasts. The regional characteristics of the aftershock decay rates have been studied for the selected Iranian earthquakes in the Alborz, Zagros and Central Iran regions considering their different seismotectonics regimes. However, due to the lack of sufficient data, no results have been reported for the Kopeh-Dagh and Makran seismotectonic regions.

  11. The 2010 Haiti earthquake sequence: new insight of the tectonic pattern from aftershocks and marine geophysical data : Haiti-OBS cruise

    NASA Astrophysics Data System (ADS)

    Mercier de Lepinay, B. F.; Mazabraud, Y.; Klingelhoefer, F.; Clouard, V.; Hello, Y.; Graindorge, D.; Marcaillou, B.; Crozon, J.; Saurel, J.; Charvis, P.; Mildor, B. S.; Deschamps, A.; Bouin, M.; Perrot, J.

    2010-12-01

    The devastating 2010 Haiti earthquake ruptured only a relatively short segment (~50km) of the Enriquillo-Plantain Garden fault (EPGF) a 600km long strike-slip fault running onland and offshore from Jamaica to Dominican Republic, with apparently no major surface rupture in the epicentral area. Considering the general behavior of such strike-slip fault (i.e. North Anatolian fault, San Andreas fault), we can expect that, following the 2010 earthquake, other large earthquakes will occur in the near future on adjacent segments. To contribute to the multinational scientific effort for a better understanding of the rupture process and the stress relaxation of this earthquake, we organized the Haiti-OBS cruise of the R/V L'Atalante few weeks after the catastrophe (Feb.5 to Feb.15, 2010, from and to Pointe-a-Pitre, Guadeloupe). Our goal was 1) to deploy a temporary network of seismologic stations -21 OBS, Ocean Bottom Seismometer, and 4 onland stations- and 2) to survey the detailed sea-floor features in relation with the deformation pattern of the area (multibeam bathymetry and mud-penetrator). We show that the distribution pattern of the aftershocks as well as the compressive surface structures observed in the geology and onshore/offshore morphology of the area are consistent with a deformation model implying a major left-lateral component along the EPGF, and a strong reverse component. The January 12, 2010 mainshock has been shown as very complex. However, in the first order, the mainshock and the distribution of the aftershocks, better localized by our temporary network, can be explained by the interaction between the strike-slip EPGF system and a blind folds-and-thrusts system. Thus, the general geological setting shows a southern extension until the southern part of the Canal du Sud area of the well-known fold and thrust system of the Hispaniola main block.

  12. Spatial Distributions of Foreshocks and Aftershocks: Static or Dynamic Triggering

    NASA Astrophysics Data System (ADS)

    Werner, M. J.; Rubin, A. M.

    2012-04-01

    In recent years, the spatial distributions of foreshocks and aftershocks have been scrutinized for evidence supporting either triggering by static stress changes induced by the permanent deformation from prior earthquakes or triggering by the dynamic stresses from seismic waves. Felzer & Brodsky (2006) identified small (m<4) mainshocks and triggered aftershocks, stacked the distances between these pairs and observed a single power-law decay with distance that extends beyond the zone traditionally thought to be affected by static stress changes. On this basis, they argued that dynamic stresses are responsible for triggering earthquakes. Richards-Dinger et al. (2010) and other studies, however, have presented several lines of evidence that suggest otherwise. One crucial question is whether the stacked distances of pairs of earthquakes, representing either mainshock-aftershock or foreshock-mainshock pairs, are in fact correctly identified and not misattributed, unrelated earthquakes. This question is especially important in the critical distance range of several to tens of earthquake radii, over which static stresses are thought to be too small to affect seismicity. If earthquake pairs in this range are not causally related, then the histogram of foreshock-mainshock and mainshock-aftershock pairs should be identical, and the difference between the two histograms can be used to identify remote triggering. Results based on southern Californian seismicity suggest that (1) the existence of a single power-law with a particular exponent may not be a robust observation, (2) geothermal regions seem to play an important role over the relevant distances, (3) remote triggering seems to exist beyond the classical static stress influence zone (perhaps out to 15 km after mainshocks with magnitudes between 3 and 4), (4) simple ETAS model simulations cannot reproduce all observations, and (5) at most one-third of the remote aftershocks had received significant static Coulomb stress

  13. eta and eta' Mesons from Lattice QCD

    SciTech Connect

    Christ, N.H.; Izubuchi, T.; Dawson, C.; Jung, C.; Liu, Q.; Mawhinney, R.D.; Sachrajda, C.T.; Soni, A.; Zhou, R.

    2010-12-08

    The large mass of the ninth pseudoscalar meson, the {eta}{prime}, is believed to arise from the combined effects of the axial anomaly and the gauge field topology present in QCD. We report a realistic, 2+1-flavor, lattice QCD calculation of the {eta} and {eta}{prime} masses and mixing which confirms this picture. The physical eigenstates show small octet-singlet mixing with a mixing angle of {theta} = -14.1(2.8){sup o}. Extrapolation to the physical light quark mass gives, with statistical errors only, m{sub {eta}} = 573(6) MeV and m{sub {eta}} = 947(142) MeV, consistent with the experimental values of 548 and 958 MeV.

  14. Foreshocks and aftershocks of the Great 1857 California earthquake

    USGS Publications Warehouse

    Meltzner, A.J.; Wald, D.J.

    1999-01-01

    The San Andreas fault is the longest fault in California and one of the longest strike-slip faults anywhere in the world, yet we know little about many aspects of its behavior before, during, and after large earthquakes. We conducted a study to locate and to estimate magnitudes for the largest foreshocks and aftershocks of the 1857 M 7.9 Fort Tejon earthquake on the central and southern segments of the fault. We began by searching archived first-hand accounts from 1857 through 1862, by grouping felt reports temporally, and by assigning modified Mercalli intensities to each site. We then used a modified form of the grid-search algorithm of Bakum and Wentworth, derived from empirical analysis of modern earthquakes, to find the location and magnitude most consistent with the assigned intensities for each of the largest events. The result confirms a conclusion of Sieh that at least two foreshocks ('dawn' and 'sunrise') located on or near the Parkfield segment of the San Andreas fault preceded the mainshock. We estimate their magnitudes to be M ~ 6.1 and M ~ 5.6, respectively. The aftershock rate was below average but within one standard deviation of the number of aftershocks expected based on statistics of modern southern California mainshock-aftershock sequences. The aftershocks included two significant events during the first eight days of the sequence, with magnitudes M ~ 6.25 and M ~ 6.7, near the southern half of the rupture; later aftershocks included a M ~ 6 event near San Bernardino in December 1858 and a M ~ 6.3 event near the Parkfield segment in April 1860. From earthquake logs at Fort Tejon, we conclude that the aftershock sequence lasted a minimum of 3.75 years.

  15. Search for invisible decays of eta and eta' in J/psi --> phi eta and phi eta'.

    PubMed

    Ablikim, M; Bai, J Z; Ban, Y; Bian, J G; Cai, X; Chen, H F; Chen, H S; Chen, H X; Chen, J C; Chen, Jin; Chen, Y B; Chi, S P; Chu, Y P; Cui, X Z; Dai, Y S; Diao, L Y; Deng, Z Y; Dong, Q F; Du, S X; Fang, J; Fang, S S; Fu, C D; Gao, C S; Gao, Y N; Gu, S D; Gu, Y T; Guo, Y N; Guo, Y Q; Guo, Z J; Harris, F A; He, K L; He, M; Heng, Y K; Hu, H M; Hu, T; Huang, G S; Huang, X T; Ji, X B; Jiang, X S; Jiang, X Y; Jiao, J B; Jin, D P; Jin, S; Jin, Yi; Lai, Y F; Li, G; Li, H B; Li, H H; Li, J; Li, R Y; Li, S M; Li, W D; Li, W G; Li, X L; Li, X N; Li, X Q; Li, Y L; Liang, Y F; Liao, H B; Liu, B J; Liu, C X; Liu, F; Liu, Fang; Liu, H H; Liu, H M; Liu, J; Liu, J B; Liu, J P; Liu, Q; Liu, R G; Liu, Z A; Lou, Y C; Lu, F; Lu, G R; Lu, J G; Luo, C L; Ma, F C; Ma, H L; Ma, L L; Ma, Q M; Ma, X B; Mao, Z P; Mo, X H; Nie, J; Olsen, S L; Peng, H P; Ping, R G; Qi, N D; Qin, H; Qiu, J F; Ren, Z Y; Rong, G; Shan, L Y; Shang, L; Shen, C P; Shen, D L; Shen, X Y; Sheng, H Y; Sun, H S; Sun, J F; Sun, S S; Sun, Y Z; Sun, Z J; Tan, Z Q; Tang, X; Tong, G L; Varner, G S; Wang, D Y; Wang, L; Wang, L L; Wang, L S; Wang, M; Wang, P; Wang, P L; Wang, W F; Wang, Y F; Wang, Z; Wang, Z Y; Wang, Zhe; Wang, Zheng; Wei, C L; Wei, D H; Wu, N; Xia, X M; Xie, X X; Xu, G F; Xu, X P; Xu, Y; Yan, M L; Yang, H X; Yang, Y X; Ye, M H; Ye, Y X; Yi, Z Y; Yu, G W; Yuan, C Z; Yuan, J M; Yuan, Y; Zang, S L; Zeng, Y; Zeng, Yu; Zhang, B X; Zhang, B Y; Zhang, C C; Zhang, D H; Zhang, H Q; Zhang, H Y; Zhang, J W; Zhang, J Y; Zhang, S H; Zhang, X M; Zhang, X Y; Zhang, Yiyun; Zhang, Z P; Zhao, D X; Zhao, J W; Zhao, M G; Zhao, P P; Zhao, W R; Zhao, Z G; Zheng, H Q; Zheng, J P; Zheng, Z P; Zhou, L; Zhou, N F; Zhu, K J; Zhu, Q M; Zhu, Y C; Zhu, Y S; Zhu, Yingchun; Zhu, Z A; Zhuang, B A; Zhuang, X A; Zou, B S

    2006-11-17

    Using a data sample of 58 x 10(6) J/psi decays collected with the Beijing Spectrometer II detector at the Beijing Electron Positron Collider, searches for invisible decays of eta and eta' in J/psi to phi eta and phi eta' are performed. The phi signals, which are reconstructed in K+K- final states, are used to tag the eta and eta' decays. No signals are found for the invisible decays of either eta or eta', and upper limits at the 90% confidence level are determined to be 1.65 x 10(-3) for the ratio B(eta-->invisible)/B(eta --> gamma gamma) and 6.69 x 10(-2) for B(eta' --> invisible)/B(eta' --> gammagamma). These are the first searches for eta and eta' decays into invisible final states. PMID:17155676

  16. P and S waves tomographic analysis of the area of El Asnam's 1980 ms 7.3 earthquake (Algeria) from its aftershock sequence

    NASA Astrophysics Data System (ADS)

    Bellalem, F.; Bounif, M. A.; Koulakov, I.

    2015-01-01

    We present the 3D seismic model of crustal structure and the distribution of seismicity in the El Asnam region (Algeria) where a strong earthquake (M7.3) occurred in 1980. We apply the local earthquake tomography inversion for the data of temporary networks which recorded the aftershocks of the 1980 event. The results of the tomography inversion have been rigorously tested using a number of different tests. The velocity anomalies from the inversion show pronounced low-velocity anomalies in the surface rupture zone associated with El Asnam fault, which are consistent with the finding of the previous studies (Philip and Meghraoui Tectonics 2:17-49, 1983), Ouyed et al. (Nature 292:26-31, 1981). Moreover, we have also reported the high velocities that exist at shallow crustal depths in the El Asnam zone. We have associated this feature to tectonic, geomorphological, and structural settings in the study area. Finally, we hope that the main features of the interpretation summarized in this article will be the basis for further integrated geophysical and tectonic analyses.

  17. The global aftershock zone

    USGS Publications Warehouse

    Parsons, Thomas E.; Margaret Segou,; Warner Marzocchi,

    2014-01-01

    The aftershock zone of each large (M ≥ 7) earthquake extends throughout the shallows of planet Earth. Most aftershocks cluster near the mainshock rupture, but earthquakes send out shivers in the form of seismic waves, and these temporary distortions are large enough to trigger other earthquakes at global range. The aftershocks that happen at great distance from their mainshock are often superposed onto already seismically active regions, making them difficult to detect and understand. From a hazard perspective we are concerned that this dynamic process might encourage other high magnitude earthquakes, and wonder if a global alarm state is warranted after every large mainshock. From an earthquake process perspective we are curious about the physics of earthquake triggering across the magnitude spectrum. In this review we build upon past studies that examined the combined global response to mainshocks. Such compilations demonstrate significant rate increases during, and immediately after (~ 45 min) M > 7.0 mainshocks in all tectonic settings and ranges. However, it is difficult to find strong evidence for M > 5 rate increases during the passage of surface waves in combined global catalogs. On the other hand, recently published studies of individual large mainshocks associate M > 5 triggering at global range that is delayed by hours to days after surface wave arrivals. The longer the delay between mainshock and global aftershock, the more difficult it is to establish causation. To address these questions, we review the response to 260 M ≥ 7.0 shallow (Z ≤ 50 km) mainshocks in 21 global regions with local seismograph networks. In this way we can examine the detailed temporal and spatial response, or lack thereof, during passing seismic waves, and over the 24 h period after their passing. We see an array of responses that can involve immediate and widespread seismicity outbreaks, delayed and localized earthquake clusters, to no response at all. About 50% of the

  18. Postseismic relaxation and aftershocks

    USGS Publications Warehouse

    Savage, J.C.; Svarc, J.L.; Yu, S.-B.

    2007-01-01

    Perfettini et al. (2005) suggested that the temporal dependence of surface displacements u(t) measured in the epicentral area following an earthquake is related to N(t), the cumulative number of aftershocks, by the equation u(t) = a + bt + cN(t) + d(1 - e-??t), where a, b, c, d, and ?? are constants chosen to fit the data and t is the postearthquake time. N(t) appears in the expression for u(t) because both the aftershocks and a portion of u(t) are thought to be driven by the same source, postseismic fault creep at subseismogenic depths on the downdip extension of the coseismic rupture. We show that this equation with the actually observed N(t) fits the postseismic displacements recorded on several baselines following each of five earthquakes: 1999 M7.6 Chi-Chi (Taiwan), 1999 M7.1 Hector Mine (southern California), 2002 M7.9 Denali (central Alaska), 2003 M6.5 San Simeon (central California), and 2004 M6.0 Parkfield (central California) earthquakes. Although there are plausible physical interpretations for each of the terms in the expression for u(t), the large number of adjustable constants (a, b, c, d, and ??) involved in fitting the rather simple postseismic displacements diminishes the significance of the fit. Because the observed N(t) is well fit by the modified Omori's law, fault creep at depth presumably exhibits the same temporal dependence. That dependence could be explained if the rheology of the fault downdip from the coseismic rupture is consistent with ordinary transient creep. Montesi (2004) demonstrated that power law creep across a shear zone at depth would also produce that temporal signal.

  19. Aftershock Number for Forecasting Short-Term Earthquake Probabilities

    NASA Astrophysics Data System (ADS)

    Christophersen, A.; Smith, E. G.

    2004-12-01

    Data from earthquakes worldwide with depths shallower than 70 km were combined from the International Seismological Centre, the US National Earthquake Information Center, Blacknest, and Harvard. An extensive magnitude and catalogue completeness study defined a `best' magnitude using the Harvard moment as a reference. The catalogue covers the period 1964 to 1995 and is effectively complete for earthquakes of magnitude 5.0 and above. The data were divided into six tectonic settings, and searched for related events using a simple window in space and time. An objective method was developed to define an elliptical aftershock area. The database of aftershock sequences has about 28,000 mainshocks of which about 2,400 have a magnitude M ≥ 6.0, and these were followed by a total of about 7,000 aftershocks. The database was analyzed in space, time, magnitude, and in the number of aftershocks in a sequence, hereafter called abundance. The aftershock decay in time and the magnitude-frequency distribution follow well- established empirical laws, Omori's law and the Gutenberg and Richter relationship. These relationships were analyzed by stacking data from various sequences within the same tectonic setting. The p-value for the aftershock decay in time was found to be 1.0 for subduction and collision zones, and for regions of mixed tectonic character like New Zealand. For mid-ocean ridges the p-value of the present dataset is 1.19 ± 0.08 and for intracontinental zones 0.86 ± 0.14. The b-value of the magnitude-frequency relation is 1.0 for aftershock sequences in all settings. No variation of the b-value with time was observed. The abundance varies greatly from sequence to sequence. It can be modeled by a geometric distribution, where the mean abundance N grows exponentially with mainshock magnitude, M i.e. log N is proportional to M. The distribution parameters for time, magnitude and abundance can be combined to probabilistically predict the number of aftershocks in a given

  20. Eta-nucleon interaction and nuclear production of eta mesons

    SciTech Connect

    Liu, L.C.

    1993-08-01

    Eta-nucleon interaction and eta-nucleus dynamics are discussed. The possibility of using {eta} to probe unnatural-parity nuclear states and to study spin-isospin correlations between two nucleons are demonstrated.

  1. Aftershocks of the 2014 South Napa, California, Earthquake: Complex faulting on secondary faults

    USGS Publications Warehouse

    Hardebeck, Jeanne L.; Shelly, David R.

    2016-01-01

    We investigate the aftershock sequence of the 2014 MW6.0 South Napa, California, earthquake. Low-magnitude aftershocks missing from the network catalog are detected by applying a matched-filter approach to continuous seismic data, with the catalog earthquakes serving as the waveform templates. We measure precise differential arrival times between events, which we use for double-difference event relocation in a 3D seismic velocity model. Most aftershocks are deeper than the mainshock slip, and most occur west of the mapped surface rupture. While the mainshock coseismic and postseismic slip appears to have occurred on the near-vertical, strike-slip West Napa fault, many of the aftershocks occur in a complex zone of secondary faulting. Earthquake locations in the main aftershock zone, near the mainshock hypocenter, delineate multiple dipping secondary faults. Composite focal mechanisms indicate strike-slip and oblique-reverse faulting on the secondary features. The secondary faults were moved towards failure by Coulomb stress changes from the mainshock slip. Clusters of aftershocks north and south of the main aftershock zone exhibit vertical strike-slip faulting more consistent with the West Napa Fault. The northern aftershocks correspond to the area of largest mainshock coseismic slip, while the main aftershock zone is adjacent to the fault area that has primarily slipped postseismically. Unlike most creeping faults, the zone of postseismic slip does not appear to contain embedded stick-slip patches that would have produced on-fault aftershocks. The lack of stick-slip patches along this portion of the fault may contribute to the low productivity of the South Napa aftershock sequence.

  2. Aftershocks and triggered events of the Great 1906 California earthquake

    USGS Publications Warehouse

    Meltzner, A.J.; Wald, D.J.

    2003-01-01

    The San Andreas fault is the longest fault in California and one of the longest strike-slip faults in the world, yet little is known about the aftershocks following the most recent great event on the San Andreas, the Mw 7.8 San Francisco earthquake on 18 April 1906. We conducted a study to locate and to estimate magnitudes for the largest aftershocks and triggered events of this earthquake. We examined existing catalogs and historical documents for the period April 1906 to December 1907, compiling data on the first 20 months of the aftershock sequence. We grouped felt reports temporally and assigned modified Mercalli intensities for the larger events based on the descriptions judged to be the most reliable. For onshore and near-shore events, a grid-search algorithm (derived from empirical analysis of modern earthquakes) was used to find the epicentral location and magnitude most consistent with the assigned intensities. For one event identified as far offshore, the event's intensity distribution was compared with those of modern events, in order to contrain the event's location and magnitude. The largest aftershock within the study period, an M ???6.7 event, occurred ???100 km west of Eureka on 23 April 1906. Although not within our study period, another M ???6.7 aftershock occurred near Cape Mendocino on 28 October 1909. Other significant aftershocks included an M ???5.6 event near San Juan Bautista on 17 May 1906 and an M ???6.3 event near Shelter Cove on 11 August 1907. An M ???4.9 aftershock occurred on the creeping segment of the San Andreas fault (southeast of the mainshock rupture) on 6 July 1906. The 1906 San Francisco earthquake also triggered events in southern California (including separate events in or near the Imperial Valley, the Pomona Valley, and Santa Monica Bay), in western Nevada, in southern central Oregon, and in western Arizona, all within 2 days of the mainshock. Of these trigerred events, the largest were an M ???6.1 earthquake near Brawley

  3. The. eta. -baryon octet

    SciTech Connect

    Tuan, S.F. )

    1992-11-01

    The recent tantalizing experimental support for an {eta}-baryon {ital J}{sup {ital P}}=1/2{sup {minus}} unmixed octet challenges conventional model wisdom. The establishment of the {Xi}(1868) member of the {eta} octet will give strong affirmation that the negative-parity baryon mass spectrum could be mixing-free.

  4. Magnitude estimates of two large aftershocks of the 16 December 1811 New Madrid earthquake

    USGS Publications Warehouse

    Hough, S.E.; Martin, S.

    2002-01-01

    The three principal New Madrid mainshocks of 1811-1812 were followed by extensive aftershock sequences that included numerous felt events. Although no instrumental data are available for either the mainshocks or the aftershocks, available historical accounts do provide information that can be used to estimate magnitudes and locations for the large events. In this article we investigate two of the largest aftershocks: one near dawn following the first mainshock on 16 December 1811, and one near midday on 17 December 1811. We reinterpret original felt reports to obtain a set of 48 and 20 modified Mercalli intensity values of the two aftershocks, respectively. For the dawn aftershock, we infer a Mw of approximately 7.0 based on a comparison of its intensities with those of the smallest New Madrid mainshock. Based on a detailed account that appears to describe near-field ground motions, we further propose a new fault rupture scenario for the dawn aftershock. We suggest that the aftershock had a thrust mechanism and occurred on a southeastern limb of the Reelfoot fault. For the 17 December 1811 aftershock, we infer a Mw of approximately 6.1 ?? 0.2. This value is determined using the method of Bakun et al. (2002), which is based on a new calibration of intensity versus distance for earthquakes in central and eastern North America. The location of this event is not well constrained, but the available accounts suggest an epicenter beyond the southern end of the New Madrid Seismic Zone.

  5. Foreshocks and Aftershocks in Simple Earthquake Models

    NASA Astrophysics Data System (ADS)

    Tiampo, K. F.; Klein, W.; Dominguez, R.; Kazemian, J.; González, P. J.

    2014-12-01

    Natural earthquake fault systems are highly heterogeneous in space; inhomogeneities occur because the earth is made of a variety of materials of different strengths and dissipate stress differently. Because the spatial arrangement of these materials is dependent on the geologic history, the distribution of these various materials can be quite complex and occur over a wide range of length scales. Despite their inhomogeneous nature, real faults are often modeled as spatially homogeneous systems. Here we present a simple earthquake fault model based on the Olami-Feder-Christensen (OFC) and Rundle-Jackson-Brown (RJB) cellular automata models with long-range interactions that incorporates a fixed percentage of stronger sites, or 'asperity cells', into the lattice. These asperity cells are significantly stronger than the surrounding lattice sites but eventually rupture when the applied stress reaches their higher threshold stress. The introduction of these spatial heterogeneities results in temporal clustering in the model that mimics those seen in natural fault systems. We observe sequences of activity that start with a gradually accelerating number of larger events (foreshocks) prior to a mainshock that is followed by a tail of decreasing activity (aftershocks). These recurrent large events occur at regular intervals, as is often observed in historic seismicity, and the time between events and their magnitude are a function of the stress dissipation parameter. The relative length of the foreshock to aftershock sequence depends on the amount of stress dissipation in the system, resulting in relatively long aftershock sequences when the stress dissipation is large versus long foreshock sequences when the stress dissipation is weak. This work provides further evidence that the spatial and temporal patterns observed in natural seismicity are strongly influenced by the underlying physical properties and are not solely the result of a simple cascade mechanism. We find that

  6. International Aftershock Forecasting: Lessons from the Gorkha Earthquake

    NASA Astrophysics Data System (ADS)

    Michael, A. J.; Blanpied, M. L.; Brady, S. R.; van der Elst, N.; Hardebeck, J.; Mayberry, G. C.; Page, M. T.; Smoczyk, G. M.; Wein, A. M.

    2015-12-01

    Following the M7.8 Gorhka, Nepal, earthquake of April 25, 2015 the USGS issued a series of aftershock forecasts. The initial impetus for these forecasts was a request from the USAID Office of US Foreign Disaster Assistance to support their Disaster Assistance Response Team (DART) which coordinated US Government disaster response, including search and rescue, with the Government of Nepal. Because of the possible utility of the forecasts to people in the region and other response teams, the USGS released these forecasts publicly through the USGS Earthquake Program web site. The initial forecast used the Reasenberg and Jones (Science, 1989) model with generic parameters developed for active deep continental regions based on the Garcia et al. (BSSA, 2012) tectonic regionalization. These were then updated to reflect a lower productivity and higher decay rate based on the observed aftershocks, although relying on teleseismic observations, with a high magnitude-of-completeness, limited the amount of data. After the 12 May M7.3 aftershock, the forecasts used an Epidemic Type Aftershock Sequence model to better characterize the multiple sources of earthquake clustering. This model provided better estimates of aftershock uncertainty. These forecast messages were crafted based on lessons learned from the Christchurch earthquake along with input from the U.S. Embassy staff in Kathmandu. Challenges included how to balance simple messaging with forecasts over a variety of time periods (week, month, and year), whether to characterize probabilities with words such as those suggested by the IPCC (IPCC, 2010), how to word the messages in a way that would translate accurately into Nepali and not alarm the public, and how to present the probabilities of unlikely but possible large and potentially damaging aftershocks, such as the M7.3 event, which had an estimated probability of only 1-in-200 for the week in which it occurred.

  7. Seismic moment ratio of aftershocks with respect to main shocks

    NASA Astrophysics Data System (ADS)

    Zakharova, O.; Hainzl, S.; Bach, C.

    2013-11-01

    The empirical Båth's law indicates that the earthquake process is self-similar and provides an opportunity to estimate the magnitude of the largest aftershock subsequent to a main shock. However, the analysis of this relation is limited to a small magnitude range and also depends on the aftershock selection rules. As an alternative, we analyze, in this paper, the cumulative seismic moment of aftershocks relative to the main shock moment, because (i) it is a physical quantity that does not only take the largest aftershock into account; (ii) background activity can be considered and as a result estimations are less affected by selection rules; and (iii) the effects of the catalog cut-off magnitude can be corrected, what leads to larger magnitude range for the analysis. We analyze the global preliminary determination of epicenters U.S. Geological Society catalog (combined with centroid moment tensor focal mechanisms) and find that the seismic moment release of aftershocks is on average approximately 5% of the main shock seismic moment. We show that the results can be well fitted by simulations of the Epidemic Type Aftershock Sequence model. In particular, we test whether simulations constrained by predictions of the static stress-triggering model, proposing a break of self-similarity due to the finite seismogenic width, are in agreement with observations. Our analysis shows that the observed dependency on the main shock magnitude as well as systematic variations with the main shock fault plane solution can be both explained by the constraints based on the static stress triggering.

  8. Aftershock communication during the Canterbury Earthquakes, New Zealand: implications for response and recovery in the built environment

    USGS Publications Warehouse

    Julia Becker,; Wein, Anne; Sally Potter,; Emma Doyle,; Ratliff, Jamie L.

    2015-01-01

    On 4 September 2010, a Mw7.1 earthquake occurred in Canterbury, New Zealand. Following the initial earthquake, an aftershock sequence was initiated, with the most significant aftershock being a Mw6.3 earthquake occurring on 22 February 2011. This aftershock caused severe damage to the city of Christchurch and building failures that killed 185 people. During the aftershock sequence it became evident that effective communication of aftershock information (e.g., history and forecasts) was imperative to assist with decision making during the response and recovery phases of the disaster, as well as preparedness for future aftershock events. As a consequence, a joint JCDR-USGS research project was initiated to investigate: • How aftershock information was communicated to organisations and to the public; • How people interpreted that information; • What people did in response to receiving that information; • What information people did and did not need; and • What decision-making challenges were encountered relating to aftershocks. Research was conducted by undertaking focus group meetings and interviews with a range of information providers and users, including scientists and science advisors, emergency managers and responders, engineers, communication officers, businesses, critical infrastructure operators, elected officials, and the public. The interviews and focus group meetings were recorded and transcribed, and key themes were identified. This paper focuses on the aftershock information needs for decision-making about the built environment post-earthquake, including those involved in response (e.g., for building assessment and management), recovery/reduction (e.g., the development of new building standards), and readiness (e.g. between aftershocks). The research has found that the communication of aftershock information varies with time, is contextual, and is affected by interactions among roles, by other information, and by decision objectives. A number

  9. Larger aftershocks happen farther away: nonseparability of magnitude and spatial distributions of aftershocks

    USGS Publications Warehouse

    Van Der Elst, Nicholas; Shaw, Bruce E.

    2015-01-01

    Aftershocks may be driven by stress concentrations left by the main shock rupture or by elastic stress transfer to adjacent fault sections or strands. Aftershocks that occur within the initial rupture may be limited in size, because the scale of the stress concentrations should be smaller than the primary rupture itself. On the other hand, aftershocks that occur on adjacent fault segments outside the primary rupture may have no such size limitation. Here we use high-precision double-difference relocated earthquake catalogs to demonstrate that larger aftershocks occur farther away than smaller aftershocks, when measured from the centroid of early aftershock activity—a proxy for the initial rupture. Aftershocks as large as or larger than the initiating event nucleate almost exclusively in the outer regions of the aftershock zone. This observation is interpreted as a signature of elastic rebound in the earthquake catalog and can be used to improve forecasting of large aftershocks.

  10. Nonlinear Viscoelastic Stress Transfer As a Possible Aftershock Triggering Mechanism

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Shcherbakov, R.

    2014-12-01

    The earthquake dynamics can be modelled by employing the spring-block system [Burridge and Knopoff, 1967]. In this approach the earthquake fault is modelled by an array of blocks coupling the loading plate and the lower plate. The dynamics of the system is governed by the system of equations of motion for each block. It is possible to map this system into a cellular automata model, where the stress acting on each block is increased in each time step, and the failing process (frictional slip) is described by stress transfer rules [Olami et al, 1992]. The OFC model produces a power-law distribution for avalanche statistics but it is not capable of producing robust aftershock sequences which follow Omori's law.We propose a nonlinear viscoelastic stress transfer mechanism in the aftershock triggering. In a basic spring-block model setting, we introduce the nonlinear viscoelastic stress transfer between neighbouring blocks, as well as between blocks and the top loading plate. The shear stress of the viscous component is a power-law function of the velocity gradient with an exponent smaller or greater than 1 for the nonlinear viscoelasticity, or 1 for the linear case. The stress transfer function of this nonlinear viscoelastic model has a power-law time-dependent form. It features an instantaneous stress transmission triggering an instantaneous avalanche, which is the same as the original spring-block model; and a power-law relaxation term, which could trigger further aftershocks. We incorporate this nonlinear viscoelasticity mechanism in a lattice cellular automata model. The model could exhibit both the Gutenberg-Richter scaling for the frequency-magnitude distribution and a power-law time decay of aftershocks, which is in accordance with Omori's law. Our study suggests that the stress transfer function may play an important role in the aftershock triggering. We have found that the time decay curve of aftershocks is affected by the shape of the stress transfer function

  11. Felt reports and intensity assignments for aftershocks and triggered events of the great 1906 California earthquake

    USGS Publications Warehouse

    Meltzner, Aron J.; Wald, David J.

    2002-01-01

    The San Andreas fault is the longest fault in California and one of the longest strikeslip faults in the world, yet little is known about the aftershocks following the most recent great event on the San Andreas, the M 7.8 San Francisco earthquake, on 18 April 1906. This open-file report is a compilation of first-hand accounts (felt reports) describing aftershocks and triggered events of the 1906 earthquake, for the first twenty months of the aftershock sequence (through December 1907). The report includes a chronological catalog. For the larger events, Modified Mercalli intensities (MMIs) have been assigned based on the descriptions judged to be the most reliable.

  12. Search for B Meson Decays to eta' eta' K

    SciTech Connect

    Aubert, B.

    2006-05-05

    The authors describe searches for decays of B mesons to the charmless final states {eta}'{eta}'K. The data consist of 228 million B{bar B} pairs produced in e{sup +}e{sup -} annihilation, collected with the BABAR detector at the Stanford Linear Accelerator Center. The 90% confidence level upper limits for the branching fractions are {Beta}(B{sup 0} {yields} {eta}'{eta}'K{sup 0}) < 31 x 10{sup -6} and {Beta}(B{sup +} {yields} {eta}'{eta}'K{sup +}) < 25 x 10{sup -6}.

  13. Forecasting Aftershocks from Multiple Earthquakes: Lessons from the Mw=7.3 2015 Nepal Earthquake

    NASA Astrophysics Data System (ADS)

    Jiménez, Abigail; NicBhloscaidh, Mairéad; McCloskey, John

    2016-04-01

    The Omori decay of aftershocks is often perturbed by large secondary events which present particular, but not uncommon, challenges to aftershock forecasting. The Mw = 7.8, 25 April 2015, Gorkha, Nepal earthquake was followed on 12 May by the Mw = 7.3 Kodari earthquake, superimposed its own aftershocks on the Gorkha sequence, immediately invalidating forecasts made by single-mainshock forecasting methods. The complexity of the Gorkha rupture process, where the hypocentre and moment centroid were separated by some 75 km, provided an insurmountable challenge for other standard forecasting methods. Here, we report several modifications of existing algorithms, which were developed in response to the complexity of this sequence and which appear to provide a more general framework for the robust and dependable forecasting of aftershock probabilities. We suggest that these methods may be operationalised to provide a scientific underpinning for an evidence-based management system for post-earthquake crises.

  14. Foreshock Sequences and Short-Term Earthquake Predictability on East Pacific Rise Transform Faults

    NASA Astrophysics Data System (ADS)

    McGuire, J. J.; Boettcher, M. S.; Jordan, T. H.

    2004-12-01

    A predominant view of continental seismicity postulates that all earthquakes initiate in a similar manner regardless of their eventual size and that earthquake triggering can be described by an Endemic Type Aftershock Sequence (ETAS) model [e.g. Ogata, 1988, Helmstetter and Sorenette 2002]. These null hypotheses cannot be rejected as an explanation for the relative abundances of foreshocks and aftershocks to large earthquakes in California [Helmstetter et al., 2003]. An alternative location for testing this hypothesis is mid-ocean ridge transform faults (RTFs), which have many properties that are distinct from continental transform faults: most plate motion is accommodated aseismically, many large earthquakes are slow events enriched in low-frequency radiation, and the seismicity shows depleted aftershock sequences and high foreshock activity. Here we use the 1996-2001 NOAA-PMEL hydroacoustic seismicity catalog for equatorial East Pacific Rise transform faults to show that the foreshock/aftershock ratio is two orders of magnitude greater than the ETAS prediction based on global RTF aftershock abundances. We can thus reject the null hypothesis that there is no fundamental distinction between foreshocks, mainshocks, and aftershocks on RTFs. We further demonstrate (retrospectively) that foreshock sequences on East Pacific Rise transform faults can be used to achieve statistically significant short-term prediction of large earthquakes (magnitude ≥ 5.4) with good spatial (15-km) and temporal (1-hr) resolution using the NOAA-PMEL catalogs. Our very simplistic approach produces a large number of false alarms, but it successfully predicts the majority (70%) of M≥5.4 earthquakes while covering only a tiny fraction (0.15%) of the total potential space-time volume with alarms. Therefore, it achieves a large probability gain (about a factor of 500) over random guessing, despite not using any near field data. The predictability of large EPR transform earthquakes suggests

  15. Self-similar aftershock rates

    NASA Astrophysics Data System (ADS)

    Davidsen, Jörn; Baiesi, Marco

    2016-08-01

    In many important systems exhibiting crackling noise—an intermittent avalanchelike relaxation response with power-law and, thus, self-similar distributed event sizes—the "laws" for the rate of activity after large events are not consistent with the overall self-similar behavior expected on theoretical grounds. This is particularly true for the case of seismicity, and a satisfying solution to this paradox has remained outstanding. Here, we propose a generalized description of the aftershock rates which is both self-similar and consistent with all other known self-similar features. Comparing our theoretical predictions with high-resolution earthquake data from Southern California we find excellent agreement, providing particularly clear evidence for a unified description of aftershocks and foreshocks. This may offer an improved framework for time-dependent seismic hazard assessment and earthquake forecasting.

  16. Self-similar aftershock rates.

    PubMed

    Davidsen, Jörn; Baiesi, Marco

    2016-08-01

    In many important systems exhibiting crackling noise-an intermittent avalanchelike relaxation response with power-law and, thus, self-similar distributed event sizes-the "laws" for the rate of activity after large events are not consistent with the overall self-similar behavior expected on theoretical grounds. This is particularly true for the case of seismicity, and a satisfying solution to this paradox has remained outstanding. Here, we propose a generalized description of the aftershock rates which is both self-similar and consistent with all other known self-similar features. Comparing our theoretical predictions with high-resolution earthquake data from Southern California we find excellent agreement, providing particularly clear evidence for a unified description of aftershocks and foreshocks. This may offer an improved framework for time-dependent seismic hazard assessment and earthquake forecasting. PMID:27627324

  17. Self-similar aftershock rates.

    PubMed

    Davidsen, Jörn; Baiesi, Marco

    2016-08-01

    In many important systems exhibiting crackling noise-an intermittent avalanchelike relaxation response with power-law and, thus, self-similar distributed event sizes-the "laws" for the rate of activity after large events are not consistent with the overall self-similar behavior expected on theoretical grounds. This is particularly true for the case of seismicity, and a satisfying solution to this paradox has remained outstanding. Here, we propose a generalized description of the aftershock rates which is both self-similar and consistent with all other known self-similar features. Comparing our theoretical predictions with high-resolution earthquake data from Southern California we find excellent agreement, providing particularly clear evidence for a unified description of aftershocks and foreshocks. This may offer an improved framework for time-dependent seismic hazard assessment and earthquake forecasting.

  18. MOLECULES IN {eta} CARINAE

    SciTech Connect

    Loinard, Laurent; Menten, Karl M.; Guesten, Rolf; Zapata, Luis A.; Rodriguez, Luis F.

    2012-04-10

    We report the detection toward {eta} Carinae of six new molecules, CO, CN, HCO{sup +}, HCN, HNC, and N{sub 2}H{sup +}, and of two of their less abundant isotopic counterparts, {sup 13}CO and H{sup 13}CN. The line profiles are moderately broad ({approx}100 km s{sup -1}), indicating that the emission originates in the dense, possibly clumpy, central arcsecond of the Homunculus Nebula. Contrary to previous claims, CO and HCO{sup +} do not appear to be underabundant in {eta} Carinae. On the other hand, molecules containing nitrogen or the {sup 13}C isotope of carbon are overabundant by about one order of magnitude. This demonstrates that, together with the dust responsible for the dimming of {eta} Carinae following the Great Eruption, the molecules detected here must have formed in situ out of CNO-processed stellar material.

  19. Search for B decays into {eta}{sup '}p, {eta}{sup '}K*, {eta}{sup '}{phi}, {eta}{sup '}{omega} and {eta}{sup '}{eta}{sup (')}

    SciTech Connect

    Schuemann, J.; Wang, C. H.; Abe, K.; Gershon, T.; Hazumi, M.; Itoh, R.; Iwasaki, Y.; Katayama, N.; Kichimi, H.; Krokovny, P.; Limosani, A.; Nakao, M.; Nakazawa, H.; Nishida, S.; Ozaki, H.; Sakai, Y.; Suzuki, S. Y.; Takasaki, F.; Tamai, K.; Tanaka, M.

    2007-05-01

    We report on a search for the exclusive two-body charmless hadronic B meson decays B{yields}{eta}{sup '}{rho}, B{yields}{eta}{sup '}K*, B{sup 0}{yields}{eta}{sup '}{phi}, B{sup 0}{yields}{eta}{sup '}{omega}, and B{sup 0}{yields}{eta}{sup '}{eta}{sup (')}. The results are obtained from a data sample containing 535x10{sup 6} BB pairs that were collected at the {upsilon}(4S) resonance with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider. We find no significant signals and report upper limits in the range (0.5-6.5)x10{sup -6} for all of the above decays.

  20. Aftershocks illuninate the 2011 Mineral, Virginia, earthquake causative fault zone and nearby active faults

    USGS Publications Warehouse

    Horton, Jr., J. Wright; Shah, Anjana K.; McNamara, Daniel E.; Snyder, Stephen L.; Carter, Aina M

    2015-01-01

    Deployment of temporary seismic stations after the 2011 Mineral, Virginia (USA), earthquake produced a well-recorded aftershock sequence. The majority of aftershocks are in a tabular cluster that delineates the previously unknown Quail fault zone. Quail fault zone aftershocks range from ~3 to 8 km in depth and are in a 1-km-thick zone striking ~036° and dipping ~50°SE, consistent with a 028°, 50°SE main-shock nodal plane having mostly reverse slip. This cluster extends ~10 km along strike. The Quail fault zone projects to the surface in gneiss of the Ordovician Chopawamsic Formation just southeast of the Ordovician–Silurian Ellisville Granodiorite pluton tail. The following three clusters of shallow (<3 km) aftershocks illuminate other faults. (1) An elongate cluster of early aftershocks, ~10 km east of the Quail fault zone, extends 8 km from Fredericks Hall, strikes ~035°–039°, and appears to be roughly vertical. The Fredericks Hall fault may be a strand or splay of the older Lakeside fault zone, which to the south spans a width of several kilometers. (2) A cluster of later aftershocks ~3 km northeast of Cuckoo delineates a fault near the eastern contact of the Ordovician Quantico Formation. (3) An elongate cluster of late aftershocks ~1 km northwest of the Quail fault zone aftershock cluster delineates the northwest fault (described herein), which is temporally distinct, dips more steeply, and has a more northeastward strike. Some aftershock-illuminated faults coincide with preexisting units or structures evident from radiometric anomalies, suggesting tectonic inheritance or reactivation.

  1. Aftershocks of the 2014 M6 South Napa Earthquake: Detection, Location, and Focal Mechanisms

    NASA Astrophysics Data System (ADS)

    Hardebeck, J.; Shelly, D. R.

    2014-12-01

    The aftershock sequence of the South Napa earthquake is notable both for its low productivity and for its geometric complexity. The aftershocks do not clearly define a fault plane consistent with the NNW-striking vertical plane implied by the mainshock moment tensor and the mapped surface rupture, but instead seem to delineate multiple secondary structures at depth. We investigate this unusual sequence by identifying additional aftershocks that do not appear in the network catalog, relocating the combined aftershock catalog using waveform cross-correlation arrival times and double-difference techniques, and determining focal mechanisms for individual events and event clusters. Additional aftershocks are detected by applying a matched filter approach to the continuous seismic data at nearby stations, with the catalog earthquakes serving as the waveform templates. In tandem with new event detections, we measure precise differential arrival times between events, which we then use in double-difference event location. We detect about 4 times as many well-located aftershocks as in the network catalog. We relocate the events using double-difference in both a 1D and a 3D velocity model. Most of the aftershocks occur between 8 and 11 km depth, similar depth to the mainshock hypocenter and deeper than most of the slip imaged seismically and geodetically. The aftershocks form a diffuse NNW-trending structure, primarily to the north of the mainshock hypocenter and on the west side of the main surface rupture. Within this diffuse trend there are clusters of aftershocks, some suggesting a N-S strike, and some that appear to dip to the east or west. Preliminary single-event and composite focal mechanisms also imply N-S striking strike-slip structures. The mainshock hypocenter and many of the aftershocks occur near the intersection of a sharply defined NE-dipping seismicity structure and the probable location of the West Napa fault, suggesting that stress is concentrated at a

  2. Analysing the 1811-1812 New Madrid earthquakes with recent instrumentally recorded aftershocks.

    PubMed

    Mueller, Karl; Hough, Susan E; Bilham, Roger

    2004-05-20

    Although dynamic stress changes associated with the passage of seismic waves are thought to trigger earthquakes at great distances, more than 60 per cent of all aftershocks appear to be triggered by static stress changes within two rupture lengths of a mainshock. The observed distribution of aftershocks may thus be used to infer details of mainshock rupture geometry. Aftershocks following large mid-continental earthquakes, where background stressing rates are low, are known to persist for centuries, and models based on rate-and-state friction laws provide theoretical support for this inference. Most past studies of the New Madrid earthquake sequence have indeed assumed ongoing microseismicity to be a continuing aftershock sequence. Here we use instrumentally recorded aftershock locations and models of elastic stress change to develop a kinematically consistent rupture scenario for three of the four largest earthquakes of the 1811-1812 New Madrid sequence. Our results suggest that these three events occurred on two contiguous faults, producing lobes of increased stress near fault intersections and end points, in areas where present-day microearthquakes have been hitherto interpreted as evidence of primary mainshock rupture. We infer that the remaining New Madrid mainshock may have occurred more than 200 km north of this region in the Wabash Valley of southern Indiana and Illinois--an area that contains abundant modern microseismicity, and where substantial liquefaction was documented by historic accounts. Our results suggest that future large mid-plate earthquake sequences may extend over a much broader region than previously suspected.

  3. Analysing the 1811-1812 New Madrid earthquakes with recent instrumentally recorded aftershocks

    USGS Publications Warehouse

    Mueller, K.; Hough, S.E.; Bilham, R.

    2004-01-01

    Although dynamic stress changes associated with the passage of seismic waves are thought to trigger earthquakes at great distances, more than 60 per cent of all aftershocks appear to be triggered by static stress changes within two rupture lengths of a mainshock. The observed distribution of aftershocks may thus be used to infer details of mainshock rupture geometry. Aftershocks following large mid-continental earthquakes, where background stressing rates are low, are known to persist for centuries, and models based on rate-and-state friction laws provide theoretical support for this inference. Most past studies of the New Madrid earthquake sequence have indeed assumed ongoing microseismicity to be a continuing aftershock sequence. Here we use instrumentally recorded aftershock locations and models of elastic stress change to develop a kinematically consistent rupture scenario for three of the four largest earthquakes of the 1811-1812 New Madrid sequence. Our results suggest that these three events occurred on two contiguous faults, producing lobes of increased stress near fault intersections and end points, in areas where present-day microearthquakes have been hitherto interpreted as evidence of primary mainshock rupture. We infer that the remaining New Madrid mainshock may have occurred more than 200 km north of this region in the Wabash Valley of southern Indiana and Illinois-an area that contains abundant modern microseismicity, and where substantial liquefaction was documented by historic accounts. Our results suggest that future large midplate earthquake sequences may extend over a much broader region than previously suspected.

  4. Iterative Strategies for Aftershock Classification in Automatic Seismic Processing Pipelines

    NASA Astrophysics Data System (ADS)

    Gibbons, Steven J.; Kværna, Tormod; Harris, David B.; Dodge, Douglas A.

    2016-04-01

    Aftershock sequences following very large earthquakes present enormous challenges to near-realtime generation of seismic bulletins. The increase in analyst resources needed to relocate an inflated number of events is compounded by failures of phase association algorithms and a significant deterioration in the quality of underlying fully automatic event bulletins. Current processing pipelines were designed a generation ago and, due to computational limitations of the time, are usually limited to single passes over the raw data. With current processing capability, multiple passes over the data are feasible. Processing the raw data at each station currently generates parametric data streams which are then scanned by a phase association algorithm to form event hypotheses. We consider the scenario where a large earthquake has occurred and propose to define a region of likely aftershock activity in which events are detected and accurately located using a separate specially targeted semi-automatic process. This effort may focus on so-called pattern detectors, but here we demonstrate a more general grid search algorithm which may cover wider source regions without requiring waveform similarity. Given many well-located aftershocks within our source region, we may remove all associated phases from the original detection lists prior to a new iteration of the phase association algorithm. We provide a proof-of-concept example for the 2015 Gorkha sequence, Nepal, recorded on seismic arrays of the International Monitoring System. Even with very conservative conditions for defining event hypotheses within the aftershock source region, we can automatically remove over half of the original detections which could have been generated by Nepal earthquakes and reduce the likelihood of false associations and spurious event hypotheses. Further reductions in the number of detections in the parametric data streams are likely using correlation and subspace detectors and/or empirical matched

  5. Aftershock Statistics explained from Geometric Reductionism

    NASA Astrophysics Data System (ADS)

    Mignan, Arnaud

    2016-04-01

    The decay of aftershocks has recently been shown to follow a stretched exponential function instead of the Omori law (Mignan, Geophys. Res. Lett., 2015). This triggers a complete re-investigation of aftershock statistics in Southern California and a new physical interpretation of these results: (1) After verifying the stretched exponential behavior of aftershocks in time, I show that aftershocks follow a pure exponential in space. I then (re)demonstrate that K(M) = exp(α(M-mmin-ΔmB)) with K the aftershock production by mainshock magnitude M, α the Gutenberg-Richter distribution slope and ΔmB Båth's parameter. Based on these observations, I propose the Recursive Aftershock Stretched Exponential (RASE) model. (2) I investigate the origin of aftershocks using geometric reductionism made possible by the Non-Critical Precursory Accelerating Seismicity Theory postulate, which states that spatial density switches from δb0 for background seismicity to δbp for activated events (such as foreshocks, induced seismicity and here aftershocks) when the static stress field σ(r) exceeds the threshold σ(rA*) ∝ Δσ* with r the distance to source. The postulate explains the exponential spatial distribution (assuming that aftershocks fill a noisy fractal network within rA*) and aftershock production (assuming a constant stress drop) with K(M) = δbp.V(M), V being the volume of a rounded cuboid centred on the fault of length l ∝ exp(αM), and with radius rA*. Finally the observed stretching factor β ≈ 0.4 is explained topologically from the fractal dimension D ≈ 1.5.

  6. Forecasting aftershock activity: 1. Adaptive estimates based on the Omori and Gutenberg-Richter laws

    NASA Astrophysics Data System (ADS)

    Baranov, S. V.; Shebalin, P. N.

    2016-05-01

    The method for forecasting the intensity of the aftershock processes after strong earthquakes in different magnitude intervals is considered. The method is based on the joint use of the time model of the aftershock process and the Gutenberg-Richter law. The time model serves for estimating the intensity of the aftershock flow with a magnitude larger than or equal to the magnitude of completeness. The Gutenberg-Richter law is used for magnitude scaling. The suggested approach implements successive refinement of the parameters of both components of the method, which is the main novelty distinguishing it from the previous ones. This approach, to a significant extent, takes into account the variations in the parameters of the frequency-magnitude distribution, which often show themselves by the decreasing fraction of stronger aftershocks with time. Testing the method on eight aftershock sequences in the regions with different patterns of seismicity demonstrates the high probability of successful forecasts. The suggested technique can be employed in seismological monitoring centers for forecasting the aftershock activity of a strong earthquake based on the results of operational processing.

  7. Monitoring 2015 Nepal aftershocks with the deployment of a TEXAN array in southern Tibet, China

    NASA Astrophysics Data System (ADS)

    Zhou, H. W.; Zou, Z.; Tong, S.; Zhang, J.; Liu, H.

    2015-12-01

    The Mw7.8 Nepal earthquake occurred on 4/25/2015 caused a continuous string of aftershocks, including the Mw7.3 main aftershock on 5/12/2015. The aftershocks, distributed mostly between the main shock and the main aftershock, are indicative of the structure of the main frontal thrust and associated fault system. Shortly after the Mw7.3 main aftershock, we conducted a field deployment of a 100-km-long array of 31 TEXAN miniature seismometers in southern Tibet, north of the Nepal-China boarder, from 5/20/2015 to 6/17/2015. This roughly north-south array with around 3 km in station spacing have recorded many aftershocks of the 2015 Nepal Earthquake series, including 22 aftershocks greater than M4.0, as well as over one hundred teleseismic events greater than M5.0, including the M7.8 deep earthquake in Chichi-shima, Japan and a sequence of M6.0 earthquakes in Solomon Islands. The purposes of deploying this mobile 2D array are: (1) Assessing the feasibility of deploying TEXAN seismometers in southern Tibet and the data quality; (2) Monitoring further aftershocks of the Nepal earthquake series and other events; and (3) Mapping the crustal structure beneath the array using regional and teleseismic data. It is encouraging that our first deployment has resulted in good data quality, and we are making a seismic profile beneath the 2D transect. Since the feasibility of deploying TEXAN's in southern Tibet is proven, we plan to make further deployment of TEXAN arrays to study crustal structure in southern Tibet.

  8. Forecasting area of strong aftershock occurrence

    NASA Astrophysics Data System (ADS)

    Baranov, Sergey; Shebalin, Peter

    2016-04-01

    Forecasting an area of strong aftershock was never, at our knowledge, considered in terms of operational forecasting. Different declustering models exist to separate post-factum the aftershocks from "independent" events. Large number of studies discussed in previous years the form of the distribution of the aftershocks distances from the mainshock fault. Here we present results of our attempts to assimilate the above researches into a model that can be used in operational aftershock forecasting. Our study was based on data provided by ANSS catalog for 1980-2015. We tried more than 20 well known and suggested by ourselves models of aftershock areas to retrospective forecasting of strong aftershock areas. We tried the models based on data for 12 hours after a mainshock and estimated their forecast quality using special modification of L-test to achieve an optimal model. As a result of our study is a model that can be used in operational forecasting area of strong aftershocks. The research was supported by Russian Foundation for Basic Research (Project 16-05-00263A).

  9. Aftershock seismicity of the 2010 Maule Mw=8.8 Chile, earthquake: Correlation between co-seismic slip models and aftershock distribution?

    USGS Publications Warehouse

    Rietbrock, A.; Ryder, I.; Hayes, G.; Haberland, C.; Comte, D.; Roecker, S.

    2012-01-01

    The 27 February 2010 Maule, Chile (Mw=8.8) earthquake is one of the best instrumentally observed subduction zone megathrust events. Here we present locations, magnitudes and cumulative equivalent moment of the first -2 months of aftershocks, recorded on a temporary network deployed within 2 weeks of the occurrence of the mainshock. Using automatically-determined onset times and a back projection approach for event association, we are able to detect over 30,000 events in the time period analyzed. To further increase the location accuracy, we systematically searched for potential S-wave arrivals and events were located in a regional 2D velocity model. Additionally, we calculated regional moment tensors to gain insight into the deformation history of the aftershock sequence. We find that the aftershock seismicity is concentrated between 40 and 140 km distance from the trench over a depth range of 10 to 35 km. Focal mechanisms indicate a predominance of thrust faulting, with occasional normal faulting events. Increased activity is seen in the outer-rise region of the Nazca plate, predominantly in the northern part of the rupture area. Further down-dip, a second band of clustered seismicity, showing mainly thrust motion, is located at depths of 40–45 km. By comparing recent published mainshock source inversions with our aftershock distribution, we discriminate slip models based on the assumption that aftershocks occur in areas of rapid transition between high and low slip, surrounding high-slip regions of the mainshock.

  10. Stress history controls the spatial pattern of aftershocks: case studies from strike-slip earthquakes

    NASA Astrophysics Data System (ADS)

    Utkucu, Murat; Durmuş, Hatice; Nalbant, Süleyman

    2016-09-01

    Earthquake ruptures perturb stress within the surrounding crustal volume and as it is widely accepted now these stress perturbations strongly correlates with the following seismicity. Here we have documented five cases of the mainshock-aftershock sequences generated by the strike-slip faults from different tectonic environments of world in order to demonstrate that the stress changes resulting from large preceding earthquakes decades before effect spatial distribution of the aftershocks of the current mainshocks. The studied mainshock-aftershock sequences are the 15 October 1979 Imperial Valley earthquake (Mw = 6.4) in southern California, the 27 November 1979 Khuli-Boniabad (Mw = 7.1), the 10 May 1997 Qa'enat (Mw = 7.2) and the 31 March 2006 Silakhor (Mw = 6.1) earthquakes in Iran and the 13 March 1992 Erzincan earthquake (Mw = 6.7) in Turkey. In the literature, we have been able to find only these mainshocks that are mainly characterized by dense and strong aftershock activities along and beyond the one end of their ruptures while rare aftershock occurrences with relatively lower magnitude reported for the other end of their ruptures. It is shown that the stress changes resulted from earlier mainshock(s) that are close in both time and space might be the reason behind the observed aftershock patterns. The largest aftershocks of the mainshocks studied tend to occur inside the stress-increased lobes that were also stressed by the background earthquakes and not to occur inside the stress-increased lobes that fall into the stress shadow of the background earthquakes. We suggest that the stress shadows of the previous mainshocks may persist in the crust for decades to suppress aftershock distribution of the current mainshocks. Considering active researches about use of the Coulomb stress change maps as a practical tool to forecast spatial distribution of the upcoming aftershocks for earthquake risk mitigation purposes in near-real time, it is further suggested that

  11. Searches for Charmless Decays B0 --> eta omega, B0 --> eta K0, B+ --> eta rho+, and B+ --> eta' pi+

    SciTech Connect

    Aubert, B

    2004-08-13

    The authors report results for measurements of the decay branching fractions of B{sup 0} to the charmless final states {eta}{omega} and {eta}K{sup 0}, and of B{sup +} to {eta}{rho}{sup +} and {eta}'{pi}{sup +}. None of these decays have been observed definitively. Measurements of the related decays B{sup +} --> {eta}K{sup +}, B{sup +} --> {eta}{pi}{sup +}, and B --> {eta}'K were published recently. Charmless decays with kaons are usually expected to be dominated by b --> s loop (''penguin'') transitions, while b --> u tree transitions are typically larger for the decays with pions and {rho} mesons. However the B --> {eta}K decays are especially interesting since they are suppressed relative to the abundant B --> {eta}'K decays due to destructive interference between two penguin amplitudes. The CKM-suppressed b --> u amplitudes may interfere significantly with penguin amplitudes, possibly leading to large direct CP violation in B{sup +} --> {eta}{rho}{sup +} and B{sup +} --> {eta}'{pi}{sup +}; numerical estimates are available in a few cases. The authors search for such direct CP violation by measuring the charge asymmetry A{sub ch} {equivalent_to} ({Gamma}{sup -} - {Gamma}{sup +})/({Gamma}{sup -} + {Gamma}{sup +}) in the rates {Gamma}{sup {+-}} = {Gamma}(B{sup {+-}} --> f{sup {+-}}), for each observed charged final state f{sup {+-}}. Charmless B decays are becoming useful to test the accuracy of theoretical predictions. Phenomenological fits to the branching fractions and charge asymmetries can be used to understand the importance of tree and penguin contributions and may provide sensitivity to the CKM angle {gamma}.

  12. {eta} and {eta}{sup '} Mesons from Lattice QCD

    SciTech Connect

    Christ, N. H.; Liu, Q.; Mawhinney, R. D.; Dawson, C.; Izubuchi, T.; Jung, C.; Soni, A.; Sachrajda, C. T.; Zhou, R.

    2010-12-10

    The large mass of the ninth pseudoscalar meson, the {eta}{sup '}, is believed to arise from the combined effects of the axial anomaly and the gauge field topology present in QCD. We report a realistic, 2+1-flavor, lattice QCD calculation of the {eta} and {eta}{sup '} masses and mixing which confirms this picture. The physical eigenstates show small octet-singlet mixing with a mixing angle of {theta}=-14.1(2.8) deg. Extrapolation to the physical light quark mass gives, with statistical errors only, m{sub {eta}}=573(6) MeV and m{sub {eta}{sup '}}=947(142) MeV, consistent with the experimental values of 548 and 958 MeV.

  13. Aftershock patterns and main shock faulting

    USGS Publications Warehouse

    Mendoza, C.; Hartzell, S.H.

    1988-01-01

    We have compared aftershock patterns following several moderate to large earthquakes with the corresponding distributions of coseismic slip obtained from previous analyses of the recorded strong ground motion and teleseismic waveforms. Our results are consistent with a hypothesis of aftershock occurrence that requires a secondary redistribution of stress following primary failure on the earthquake fault. Aftershocks followng earthquakes examined in this study occur mostly outside of or near the edges of the source areas indicated by the patterns of main shock slip. The spatial distribution of aftershocks reflects either a continuation of slip in the outer regions of the areas of maximum coseismic displacement or the activation of subsidiary faults within the volume surrounding the boundaries of main shock rupture. -from Authors

  14. Foreshock and Aftershocks in Simple Earthquake Models

    NASA Astrophysics Data System (ADS)

    Kazemian, J.; Tiampo, K. F.; Klein, W.; Dominguez, R.

    2015-02-01

    Many models of earthquake faults have been introduced that connect Gutenberg-Richter (GR) scaling to triggering processes. However, natural earthquake fault systems are composed of a variety of different geometries and materials and the associated heterogeneity in physical properties can cause a variety of spatial and temporal behaviors. This raises the question of how the triggering process and the structure interact to produce the observed phenomena. Here we present a simple earthquake fault model based on the Olami-Feder-Christensen and Rundle-Jackson-Brown cellular automata models with long-range interactions that incorporates a fixed percentage of stronger sites, or asperity cells, into the lattice. These asperity cells are significantly stronger than the surrounding lattice sites but eventually rupture when the applied stress reaches their higher threshold stress. The introduction of these spatial heterogeneities results in temporal clustering in the model that mimics that seen in natural fault systems along with GR scaling. In addition, we observe sequences of activity that start with a gradually accelerating number of larger events (foreshocks) prior to a main shock that is followed by a tail of decreasing activity (aftershocks). This work provides further evidence that the spatial and temporal patterns observed in natural seismicity are strongly influenced by the underlying physical properties and are not solely the result of a simple cascade mechanism.

  15. High-resolution relocation and mechanism of aftershocks of the 2007 Tocopilla (Chile) earthquake

    NASA Astrophysics Data System (ADS)

    Fuenzalida, A.; Schurr, B.; Lancieri, M.; Sobiesiak, M.; Madariaga, R.

    2013-08-01

    We study the distribution of the aftershocks of Tocopilla Mw 7.7 earthquake of 2007 November 14 in northern Chile in detail. This earthquake broke the lower part of the seismogenic zone at the southern end of the Northern Chile gap, a region that had its last megathrust earthquake in 1877. The aftershocks of Tocopilla occurred in several steps: the first day they were located along the coast inside the co-seismic rupture zone. After the second day they extended ocean-wards near the Mejillones peninsula. Finally in December they concentrated in the South near the future rupture zone of the Michilla intermediate depth earthquake of 2007 December 16. The aftershock sequence was recorded by the permanent IPOC (Integrated Plate Boundary Observatory in Chile) network and the temporary task force network installed 2 weeks after the main event. A total of 1238 events were identified and the seismic arrival times were directly read from seismograms. Initially we located these events using a single event procedure and then we relocated them using the double-difference method and a cross-correlation technique to measure time differences for clusters of aftershocks. We tested a 1-D velocity model and a 2-D one that takes into account the presence of the subducted Nazca Plate. Relocation significantly reduced the width of the aftershock distribution: in the inland area, the plate interface imaged by the aftershocks is thinner than 2 km. The two velocity models give similar results for earthquakes under the coast and a larger difference for events closer to the trench. The surface imaged by the aftershocks had a length of 160 km. It extends from 30 to 50 km depth in the northern part of the rupture zone; and between 5 and 55 km depth near the Mejillones peninsula. We observed a change in the dip angle of the subduction interface from 18° to 24° at a depth of 30 km. We propose that this change in dip is closely associated with the upper limit of the rupture zone of the main

  16. Branching Fraction Limits for B0 Decays to eta' eta, eta' pi0 and eta pi0

    SciTech Connect

    Aubert, B.

    2006-03-10

    We describe searches for decays to two-body charmless final states {eta}'{eta}, {eta}'{pi}{sup 0} and {eta}{pi}{sup 0} of B{sup 0} mesons produced in e{sup +}e{sup -} annihilation. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 232 million produced B{bar B} pairs. The results for branching fractions are, in units of 10{sup -6} (upper limits at 90% C.L.): {Beta}(B{sup 0} {yields} {eta}'{eta}) = 0.2{sub -0.5}{sup +0.7} {+-} 0.4 (< 1.7), {Beta}(B{sup 0} {yields} {eta}{pi}{sup 0}) = 0.6{sub -0.4}{sup +0.5} {+-} 0.1 (< 1.3), and {Beta}(B{sup 0} {yields} {eta}'{pi}{sup 0}) = 0.8{sub -0.6}{sup +0.8} {+-} 0.1 (< 2.1). The first error quoted is statistical and the second systematic.

  17. Simultaneous estimation of b-values and detection rates of earthquakes for the application to aftershock probability forecasting

    NASA Astrophysics Data System (ADS)

    Katsura, K.; Ogata, Y.

    2004-12-01

    Reasenberg and Jones [Science, 1989, 1994] proposed the aftershock probability forecasting based on the joint distribution [Utsu, J. Fac. Sci. Hokkaido Univ., 1970] of the modified Omori formula of aftershock decay and Gutenberg-Richter law of magnitude frequency, where the respective parameters are estimated by the maximum likelihood method [Ogata, J. Phys. Earth, 1983; Utsu, Geophys Bull. Hokkaido Univ., 1965, Aki, Bull. Earthq. Res. Inst., 1965]. The public forecast has been implemented by the responsible agencies in California and Japan. However, a considerable difficulty in the above procedure is that, due to the contamination of arriving seismic waves, detection rate of aftershocks is extremely low during a period immediately after the main shock, say, during the first day, when the forecasting is most critical for public in the affected area. Therefore, for the forecasting of a probability during such a period, they adopt a generic model with a set of the standard parameter values in California or Japan. For an effective and realistic estimation, I propose to utilize the statistical model introduced by Ogata and Katsura [Geophys. J. Int., 1993] for the simultaneous estimation of the b-values of Gutenberg-Richter law together with detection-rate (probability) of earthquakes of each magnitude-band from the provided data of all detected events, where the both parameters are allowed for changing in time. Thus, by using all detected aftershocks from the beginning of the period, we can estimate the underlying modified Omori rate of both detected and undetected events and their b-value changes, taking the time-varying missing rates of events into account. The similar computation is applied to the ETAS model for complex aftershock activity or regional seismicity where substantial missing events are expected immediately after a large aftershock or another strong earthquake in the vicinity. Demonstrations of the present procedure will be shown for the recent examples

  18. Relation between aftershock parameters and geodetic slip models: Case study of the 2010 Mw8.8 Maule (Chile) and the 2011 Mw9.0 Tohoku-oki (Japan) earthquakes

    NASA Astrophysics Data System (ADS)

    Zakharova, Olga; Hainzl, Sebastian; Lange, Dietrich; Enescu, Bogdan

    2016-04-01

    The distribution of local stresses, which represents as well crustal heterogeneity, is the main factor for aftershock triggering. Though neither local stresses nor crustal heterogeneity are known in detail, some information of their distribution is implicitly represented by slip and coupling values on the mainshock fault interface. Taking these two concepts as the main assumptions, we perform a comprehensive analysis of the relation between aftershock characteristics and geodetic measurements on the mainshock fault interface. As a case study we select two megathrust events, the 2010 Mw8.8 Maule (Chile) and the 2011 Mw9.0 Tohoku-oki (Japan), due to the availability of rich aftershock data as well as of geodetic inversion models. To investigate the dependency between these data sets we firstly estimated the aftershock parameter distribution, using a modified ETAS model, which allows to take into account the mainshock rupture extension. Secondly we calculate the correlation between aftershock parameters and coseismic/postseismic slip and interseismic coupling. We find: (1) aftershocks tend to occur in the areas of high coseismic slip gradient, afterslip and interseismic coupling; (2) aftershock seismic moment is released preferentially in regions of large coseismic slip, coseismic slip gradient and interseismically locked areas; (3) anomalous aftershock parameters occur in the areas of reactivated fault systems. Moreover, we show that modified ETAS model outperforms the classical one in the cases when the mainshock rupture extension cannot be neglected and represented as a point source. One of the main restriction in the presented analysis is related to the large uncertainties of the inversion models, which limit the significance of our results.

  19. The Rule of Dynamic Strain to Near Source Aftershock Distribution of the 2014, Mw 6.0, Napa (California) Earthquake

    NASA Astrophysics Data System (ADS)

    Emolo, A.; De Matteis, R.; Convertito, V.

    2015-12-01

    The 2014 Napa was recognized as a right-lateral strike-slip fault. About 400 aftershocks occurred, mainly in the near-source range, in the two months after the earthquake. They mostly occurred between 8 and 11 km depth interesting an area of about 10 km2 north-northwest-trending with respect to the mainshock hypocenter. However, the aftershock distribution was not able to constrain the mainshock fault plane. Since Parsons et al. (2014) have shown that Coulomb static stress change does not completely explain near-source aftershock distribution, we explore whether dynamic strain transfer, enhanced by source directivity, contributed to trigger the aftershock sequence. Indeed, dynamic strain transfer triggering attributes enhanced failure probabilities to increased shear stresses or strains, to permeability changes and maybe to fault weakening. In this respect, we observe that a single inverse power law fits the decay of aftershock density as function of distance from the fault plane, suggesting that dynamic stress/strain might have played a role in the aftershocks triggering. To test this hypothesis, we used Peak-Ground Velocities (PGVs) as a proxy for peak-dynamic strain/stress field, accounting for both fault finiteness and source directivity. We first use a point source to retrieve the best parameters of the directivity function from the inversion of the PGVs. Next, the same PGVs are used to jointly infer the surface fault projection and the dominant horizontal rupture direction. Finally, we map the peak-dynamic strain/stress, modified by source geometry and directivity, to resolve the relationship between the aftershocks location and the areas of large dynamic strain values. Thus, we believe that dynamic strain/stress actually contributed to the Napa aftershock distribution. Our results may help to better constrain the Napa causative fault and complement Coulomb static stress change to identify areas that will be more likely affected by aftershocks.

  20. B-meson decays to eta' rho, eta' f0, and eta' K*

    SciTech Connect

    del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Palano, A.; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Battaglia, M.; Brown, D.N.; Hooberman, B.; Kerth, L.T.; Kolomensky, Yu.G.; Lynch, G.; Osipenkov, I.L.; Tanabe, T.; /UC, Berkeley /Birmingham U. /Ruhr U., Bochum /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UC, Riverside /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /INFN, Ferrara /Ferrara U. /INFN, Ferrara /INFN, Ferrara /Ferrara U. /INFN, Ferrara /Frascati /INFN, Genoa /Genoa U. /INFN, Genoa /INFN, Genoa /Genoa U. /INFN, Genoa /INFN, Genoa /Genoa U. /Indian Inst. Tech., Guwahati /Harvard U. /Heidelberg U. /Humboldt U., Berlin /Imperial Coll., London /Iowa State U. /Iowa State U. /Johns Hopkins U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Mainz U., Inst. Kernphys. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT /McGill U. /INFN, Milan /Milan U. /INFN, Milan /INFN, Milan /Milan U. /INFN, Milan /Mississippi U. /Montreal U. /INFN, Naples /Naples U. /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /INFN, Padua /Padua U. /INFN, Padua /INFN, Padua /Padua U. /Paris U., VI-VII /INFN, Perugia /Perugia U. /INFN, Pisa /Pisa U. /INFN, Pisa /Pisa, Scuola Normale Superiore /INFN, Pisa /Pisa U. /INFN, Pisa /Princeton U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /Rostock U. /Rutherford /DAPNIA, Saclay /SLAC /South Carolina U. /Southern Methodist U. /Stanford U., Phys. Dept. /SUNY, Albany /Tel Aviv U. /Tennessee U. /Texas U. /Texas U., Dallas /INFN, Turin /Turin U. /INFN, Trieste /Trieste U. /Valencia U. /Victoria U. /Warwick U. /Wisconsin U., Madison

    2010-08-25

    We present measurements of B-meson decays to the final states {eta}{prime} {rho}, {eta}{prime} f{sub 0}, and {eta}{prime} K*, where K* stands for a vector, scalar, or tensor strange meson. We observe a significant signal or evidence for {eta}{prime} {rho}{sup +} and all the {eta}{prime}K* channels. We also measure, where applicable, the charge asymmetries, finding results consistent with no direct CP violation in all cases. The measurements are performed on a data sample consisting of 467 x 10{sup 6} B{bar B} pairs, collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. Our results favor the theoretical predictions from perturbative QCD and QCD Factorization and we observe an enhancement of the tensor K*{sub 2} (1430) with respect to the vector K*(892) component.

  1. Aftershock triggering by postseismic stresses: A study based on Coulomb rate-and-state models

    NASA Astrophysics Data System (ADS)

    Cattania, Camilla; Hainzl, Sebastian; Wang, Lifeng; Enescu, Bogdan; Roth, Frank

    2015-04-01

    The spatiotemporal clustering of earthquakes is a feature of medium- and short-term seismicity, indicating that earthquakes interact. However, controversy exists about the physical mechanism behind aftershock triggering: static stress transfer and reloading by postseismic processes have been proposed as explanations. In this work, we use a Coulomb rate-and-state model to study the role of coseismic and postseismic stress changes on aftershocks and focus on two processes: creep on the main shock fault plane (afterslip) and secondary aftershock triggering by previous aftershocks. We model the seismic response to Coulomb stress changes using the Dieterich constitutive law and focus on two events: the Parkfield, Mw = 6.0, and the Tohoku, Mw = 9.0, earthquakes. We find that modeling secondary triggering systematically improves the maximum log likelihood fit of the sequences. The effect of afterslip is more subtle and difficult to assess for near-fault events, where model errors are largest. More robust conclusions can be drawn for off-fault aftershocks: following the Tohoku earthquake, afterslip promotes shallow crustal seismicity in the Fukushima region. Simple geometrical considerations indicate that afterslip-induced stress changes may have been significant on trench parallel crustal fault systems following several of the largest recorded subduction earthquakes. Moreover, the time dependence of afterslip strongly enhances its triggering potential: seismicity triggered by an instantaneous stress change decays more quickly than seismicity triggered by gradual loading, and as a result we find afterslip to be particularly important between few weeks and few months after the main shock.

  2. Modelling aftershock migration and afterslip of the San Juan Bautista, California, earthquake of October 3, 1972

    USGS Publications Warehouse

    Wesson, R.L.

    1987-01-01

    The San Juan Bautista earthquake of October 3, 1972 (ML = 4.8), located along the San Andreas fault in central California, initiated an aftershock sequence characterized by a subtle, but perceptible, tendency for aftershocks to spread to the northwest and southeast along the fault zone. The apparent dimension of the aftershock zone along strike increased from about 7-10 km within a few days of the earthquake, to about 20 km eight months later. In addition, the mainshock initiated a period of accelerated fault creep, which was observed at 2 creep meters situated astride the trace of the San Andreas fault within about 15 km of the epicenter of the mainshock. The creep rate gradually returned to the preearthquake rate after about 3 yrs. Both the spreading of the aftershocks and the rapid surface creep are interpreted as reflecting a period of rapid creep in the fault zone representing the readjustment of stress and displacement following the failure of a "stuck" patch or asperity during the San Juan Bautista earthquake. Numerical calculations suggest that the behavior of the fault zone is consistent with that of a material characterized by a viscosity of about 3.6??1014 P, although the real rheology is likely to be more complicated. In this model, the mainshock represents the failure of an asperity that slips only during earthquakes. Aftershocks represent the failure of second-order asperities which are dragged along by the creeping fault zone. ?? 1987.

  3. The seismology of eta Bootes

    NASA Technical Reports Server (NTRS)

    Demarque, Pierre; Guenther, D. B.

    1995-01-01

    Some p-mode frequencies and other observations were used to determine the mass, the age and the helium abundance of eta Bootes. It is shown how, by direct application, the p-mode frequencies and stellar seismological tools help in constraining the physical parameters of eta Boo. The existence of mode bumping is confirmed and it is discussed how it may be used to refine the estimate of the eta Boo's age. The effect of the OPAL equation of state on the p-mode frequencies is described.

  4. The Importance of Small Aftershocks for Earthquake Triggering

    NASA Astrophysics Data System (ADS)

    Woessner, Jochen; Meier, Men-Andrin; Werner, Max; Wiemer, Stefan

    2013-04-01

    Earthquakes occur in response to changes in the crust's stress state, however, the full picture of the causative process for earthquake triggering remains unclear. Many researchers have employed Coulomb stress change theory, which quantifies the changes in static Coulomb stress from nearby ruptures. This theory seems to at least partly explain the spatial patterns of triggered earthquakes, in particular during aftershock sequences and along faults. Several assumptions are needed to facilitate the calculation of stress changes. Here, we challenge the typical neglect of stress changes induced by the small but numerous and strongly clustered aftershocks during the evolution of the sequence. Both empirical observations and a simple scaling law suggest that this neglect may not be justified. We estimate the evolution of Coulomb stress changes during the 1992 Mw 7.3 Landers earthquake sequence by including the effect of the detected aftershocks using the focal mechanisms from the recently updated Southern California catalog. This estimation is hampered by that only 62% of located events from our study window have a focal mechanism, by the neglect of events that are too small to be detected and by the unreliability of near-field stress change estimations. As a consequence, we are limited to analyzing only a part of the full stress change signal imparted by small events. Despite these shortcomings, our calculations suggest that small to moderate events strongly dominate static stress redistribution in dense secondary aftershock clusters. However, their relative importance varies over space and is, on average, smaller than the main shock contribution. Furthermore, we find that aftershocks - with their reported relative orientations and positions - impose more often positive than negative stress changes, which is what would be expected if they were actively involved in triggering processes. However, this effect appears to be limited to event pairs with inter-event distances

  5. Tests of remote aftershock triggering by small mainshocks using Taiwan's earthquake catalog

    NASA Astrophysics Data System (ADS)

    Peng, W.; Toda, S.

    2014-12-01

    To understand earthquake interaction and forecast time-dependent seismic hazard, it is essential to evaluate which stress transfer, static or dynamic, plays a major role to trigger aftershocks and subsequent mainshocks. Felzer and Brodsky focused on small mainshocks (2≤M<3) and their aftershocks, and then argued that only dynamic stress change brings earthquake-to-earthquake triggering, whereas Richards-Dingers et al. (2010) claimed that those selected small mainshock-aftershock pairs were not earthquake-to-earthquake triggering but simultaneous occurrence of independent aftershocks following a larger earthquake or during a significant swarm sequence. We test those hypotheses using Taiwan's earthquake catalog by taking the advantage of lacking any larger event and the absence of significant seismic swarm typically seen with active volcano. Using Felzer and Brodsky's method and their standard parameters, we only found 14 mainshock-aftershock pairs occurred within 20 km distance in Taiwan's catalog from 1994 to 2010. Although Taiwan's catalog has similar number of earthquakes as California's, the number of pairs is about 10% of the California catalog. It may indicate the effect of no large earthquakes and no significant seismic swarm in the catalog. To fully understand the properties in the Taiwan's catalog, we loosened the screening parameters to earn more pairs and then found a linear aftershock density with a power law decay of -1.12±0.38 that is very similar to the one in Felzer and Brodsky. However, none of those mainshock-aftershock pairs were associated with a M7 rupture event or M6 events. To find what mechanism controlled the aftershock density triggered by small mainshocks in Taiwan, we randomized earthquake magnitude and location. We then found that those density decay in a short time period is more like a randomized behavior than mainshock-aftershock triggering. Moreover, 5 out of 6 pairs were found in a swarm-like temporal seismicity rate increase

  6. Aftershocks driven by a high-pressure CO2 source at depth.

    PubMed

    Miller, Stephen A; Collettini, Cristiano; Chiaraluce, Lauro; Cocco, Massimo; Barchi, Massimiliano; Kaus, Boris J P

    2004-02-19

    In northern Italy in 1997, two earthquakes of magnitudes 5.7 and 6 (separated by nine hours) marked the beginning of a sequence that lasted more than 30 days, with thousands of aftershocks including four additional events with magnitudes between 5 and 6. This normal-faulting sequence is not well explained with models of elastic stress transfer, particularly the persistence of hanging-wall seismicity that included two events with magnitudes greater than 5. Here we show that this sequence may have been driven by a fluid pressure pulse generated from the coseismic release of a known deep source of trapped high-pressure carbon dioxide (CO2). We find a strong correlation between the high-pressure front and the aftershock hypocentres over a two-week period, using precise hypocentre locations and a simple model of nonlinear diffusion. The triggering amplitude (10-20 MPa) of the pressure pulse overwhelms the typical (0.1-0.2 MPa) range from stress changes in the usual stress triggering models. We propose that aftershocks of large earthquakes in such geologic environments may be driven by the coseismic release of trapped, high-pressure fluids propagating through damaged zones created by the mainshock. This may provide a link between earthquakes, aftershocks, crust/mantle degassing and earthquake-triggered large-scale fluid flow.

  7. Scaling Relations Between Mainshock Source Parameters and Aftershock Distributions for Use in Aftershock Forecasting

    NASA Astrophysics Data System (ADS)

    Donovan, J.; Jordan, T. H.

    2010-12-01

    Aftershocks are often used to delineate the mainshock rupture zone retrospectively. In aftershock forecasting on the other hand, the problem is to use mainshock rupture area to determine the aftershock zone prospectively. The procedures for this type of prediction are not as well developed and have been restricted to simple parameterizations such as the Utsu-Seki (1955) scaling relation between mainshock energy and aftershock area (Ogata and Zhueng, 2006). With a focus on improving current forecasting methods, we investigate the relationship between spatial source parameters that can be rapidly computed (spatial centroid and characteristic dimensions) and corresponding spatial measures of the aftershock distribution. For a set of about 30 large events, we either extracted source parameters from the McGuire et al (2002) finite moment tensor (FMT) catalog, or computed them from the online SRCMOD database (Mai, 2004). We identified aftershocks with windowing and scale-free methods, and computed both L1 and L2 measures of their distributions. Our comparisons produce scaling relations among the characteristic dimensions that can be used to initiate aftershock forecasts. By using rapidly-determined source parameters, we can decrease the forecasting latency and thus improve the probability gain of the forecasting methods.

  8. Gluon content of the {eta} and {eta}{sup '} mesons and the {eta}{gamma} , {eta}{sup '}{gamma} electromagnetic transition form factors

    SciTech Connect

    Agaev, S.S.; Stefanis, N.G.

    2004-09-01

    We compute power-suppressed corrections to the {eta}{gamma} and {eta}{sup '}{gamma} transition form factors Q{sup 2}F{sub {eta}}{sub ({eta}}{sub {sup '}}{sub {gamma}}(Q{sup 2}) arising from the end point regions x{yields}0,1 by employing the infrared-renormalon approach. The contribution to the form factors from the quark and gluon content of the {eta},{eta}{sup '} mesons is taken into account using for the {eta}-{eta}{sup '} mixing the SU{sub f}(3) singlet {eta}{sub 1} and octet {eta}{sub 8} basis. The theoretical predictions obtained this way are compared with the corresponding CLEO data and restrictions on the input parameters (Gegenbauer coefficients) B{sub 2}{sup q}({eta}{sub 1}), B{sub 2}{sup g}({eta}{sub 1}), and B{sub 2}{sup q}({eta}{sub 8}) in the distribution amplitudes for the {eta}{sub 1},{eta}{sub 8} states with one nonasymptotic term are deduced. Comparison is made with the results from QCD perturbation theory.

  9. Aftershock production rate of driven viscoelastic interfaces.

    PubMed

    Jagla, E A

    2014-10-01

    We study analytically and by numerical simulations the statistics of the aftershocks generated after large avalanches in models of interface depinning that include viscoelastic relaxation effects. We find in all the analyzed cases that the decay law of aftershocks with time can be understood by considering the typical roughness of the interface and its evolution due to relaxation. In models where there is a single viscoelastic relaxation time there is an exponential decay of the number of aftershocks with time. In models in which viscoelastic relaxation is wave-vector dependent we typically find a power-law dependence of the decay rate that is compatible with the Omori law. The factors that determine the value of the decay exponent are analyzed.

  10. The earthquake and its aftershocks from May 2 through September 30, 1983

    SciTech Connect

    Eaton, J.P.

    1990-01-01

    Analysis of the Coalinga earthquake sequence, based on the Allen/Ellis real-time-processor (RTP) automatic P-phase-onset times and duration measurements, provides hypocentral and magnitude determinations for more than 6,000 events from May 2 through September 30, 1983. Focal mechanisms and local magnitudes of more than 140 of the larger aftershocks were calculated from more detailed observations obtained from magnetic-tape playbacks from both the temporary Coalinga seismic network and the permanent telemetered central California seismic network (Calnet). The combined catalog appears to be substantially complete for events of M {ge} 3 within about 3 hours, and for events of M {ge} 1.7 within about 1 day, after the main shock. The first-motion plot of the main shock offers two choices for the main-shock fault; a thrust fault striking N. 53{degree}W. and dipping 23{degree}SW. (the preferred fault plane), or a high-angle reverse fault striking N. 53{degree}W. and dipping 67{degree}NE. Focal mechanisms of the larger aftershocks also indicate predominantly thrust or reverse faulting. The long axis of the aftershock zone, which is 35 km long and 15 to 20 km wide, coincides with the axis of the Anticline Ridge-Guijarral Hills structure at the Coast Ranges-Great Valley boundary northeast of Coalinga. A transverse (southwest to northeast) quiet band with very few events crosses the aftershock zone where northwest-trending Anticline Ridge joins broader, east-west-trending Joaquin Ridge just northwest of the main shock. The smaller aftershocks occur mostly in the hanging-wall blocks above the faults outlined by the larger aftershocks.

  11. GIS-based 3D visualization of the Mw 7.7, 2007, Tocopilla aftershocks

    NASA Astrophysics Data System (ADS)

    Eggert, S.; Sobiesiak, M.; Altenbrunn, K.

    2009-12-01

    The November 14, 2007 Mw 7.7 earthquake nucleated on the west coast of northern Chile about 40 km east of the city of Tocopilla. It took place in the southern part of a large seismic gap, the Iquique subduction zone segment which is supposed to be at the end of its seismic cycle. The Tocopilla fault plane appears to be the northern continuation of the Mw 8.0, 1995 Antofagasta earthquake. We present a complex 3D model of the rupture area including first hypocenter localizations of aftershocks following the event. The data was recorded during a mission of the German Task Force for Earthquakes after the 2007 Tocopilla earthquake. The seismic stations were recording the aftershocks from November 2007 until May 2008. In general, subduction zones have a complex structure where most of the volumes examined are characterized by strong variations in physical and material parameters. Therefore, 3D representation of the geophysical and geological conditions to be found are of great importance to understand such a subduction environment. We start with a two-dimensional visualization of the geological and geophysical setting. In a second step, we use GIS as a three-dimensional modeling tool which gives us the possibility to visualize the complex geophysical processes. One can easily add and delete data and focus on the information one needs. This allows us to investigate the aftershock distribution along the subducting slab and identify clear structures and clusters within the data set. Furthermore we combine the 2007 Tocopilla data set with the 1995 Antofagasta aftershocks which provides a new, three-dimensional insight into the segment boundary of these two events. Analyzing the aftershock sequence with a GIS-based model will not only help to visualize the setting but also be the base for various calculations and further explorations of the complex structures. Aftershocks following the 1995 Antofagasta earthquake and the 2007 Tocopilla earthquake

  12. Seismological evidence of an active footwall shortcut thrust in the Northern Itoigawa-Shizuoka Tectonic Line derived by the aftershock sequence of the 2014 M 6.7 Northern Nagano earthquake

    NASA Astrophysics Data System (ADS)

    Panayotopoulos, Yannis; Hirata, Naoshi; Hashima, Akinori; Iwasaki, Takaya; Sakai, Shin'ichi; Sato, Hiroshi

    2016-06-01

    A destructive M 6.7 earthquake struck Northern Nagano prefecture on November 22, 2014. The main shock occurred on the Kamishiro fault segment of the northern Itoigawa-Shizuoka Tectonic Line (ISTL). We used data recorded at 41 stations of the local seismographic network in order to locate 2118 earthquakes that occurred between November 18 and November 30, 2014. To estimate hypocenters, we assigned low Vp models to stations within the Northern Fossa Magna (NFM) basin thus accounting for large lateral crustal heterogeneities across the Kamishiro fault. In order to further improve accuracy, the final hypocenter locations were recalculated inside a 3D velocity model using the double-difference method. We used the aftershock activity distribution and focal mechanism solutions of major events in order to estimate the source fault area of the main shock. Our analysis suggests that the shallow part of the source fault corresponds to the surface trace of the Kamishiro fault and dips 30°-45° SE, while the deeper part of the source fault corresponds to the downdip portion of the Otari-Nakayama fault, a high angle fault dipping 50°-65° SE that formed during the opening of the NFM basin in the Miocene. Along its surface trace the Otari-Nakayama fault has been inactive during the late Quaternary. We verified the validity of our model by calculating surface deformation using a simple homogeneous elastic half-space model and comparing it to observed surface deformation from satellite interferometry, assuming large coseismic slip in the areas of low seismicity and small coseismic slip in the areas of high seismicity. Shallowing of the source fault from 50°-65° to 30°-45° in the upper 4 km, in the areas where both surface fault traces are visible, is a result of footwall shortcut thrusting by the Kamishiro fault off the Otari-Nakayama fault.

  13. Spatial/Temporal interdependence of aftershocks following the 10/31/2001 M5.1 Anza Earthquake

    NASA Astrophysics Data System (ADS)

    Kilb, D.; Martynov, V.; Vernon, F. L.

    2004-12-01

    On 10/31/2001, a M5.1 earthquake occurred in the middle of the ANZA network (7 24-bit broadband stations were within 20 km of the epicenter) that spans the San Jacinto fault zone in southern California. A high pass filter (f > 1.0 Hz) was used to identify seismic arrival times of the aftershocks and in turn determine the aftershock locations. In this way, we cataloged 599 events (0< M < 2.5) in the initial 2 hours of this sequence and 4500 aftershocks within the first 2 months, complete to M ≈ 0.0. Here, we study three different temporal/spatial features found in these data. (1) Initially we suspected earthquakes within the region of the mainshock had a bimodal distribution of earthquake magnitudes (peaks at M=0.1 and M=1.5); however, we found this distribution was an artifact of the spatial recording capabilities of small magnitude aftershocks. (2) In the original aftershock locations we found two linear voids in seismicity (trends ˜N45W and ˜N45E) in the primary aftershock cluster forming an X pattern. This is not likely caused by the number of significant digits in the location algorithm because these voids do not follow individual latitude or longitude lines, nor is this likely due to recording inaccuracies because the network coverage of the region is more than optimal. We are investigating other causes of these voids. (3) In the broadband data, we found only one detectable aftershock in the first 2 minutes of the continuous waveforms; yet on the short period records at one of the closest stations, TRO, we can identify an additional event at 15 seconds into the sequence. To quantify our detection capabilities, we estimate when aftershocks of different magnitudes can be identified within the mainshock coda. We are fairly confident that \\> M 1.5 events 45 seconds or longer after the mainshock should be detectable, which suggests that the lack of seismicity in the 45 second-2.0 minute range is potentially real. This non-zero lag-time between the mainshock

  14. The Mw 5.8 Virginia Earthquake of August 23, 2011 and its Aftershocks: A Shallow High Stress Drop Event

    NASA Astrophysics Data System (ADS)

    Ellsworth, W. L.; Imanishi, K.; Luetgert, J. H.; Kruger, J.; Hamilton, J.

    2011-12-01

    We analyze the hypocentral distribution and source parameters of the aftershocks of the Virginia Earthquake of August 23, 2011 using a temporary array of telemetered instruments deployed within 20 km of the main shock. Our data come from four USGS NetQuakes accelerometers and seven IRIS/PASSCAL seismometers that were established within a few days of the earthquake. Aftershock seismograms at these near-source stations are characterized by impulsive, high-frequency P and S phases at most sites. In addition, we use the five closest permanent stations (60 - 310 km distance) to analyze the main shock. Hypocenters, crustal velocity model and station corrections were determined using the program VELEST (Kissling, et al, 1994). The aftershocks define a 10-km-long, N 30 degree E striking, 45 degree ESE dipping fault. This fault plane agrees well with the USGS moment tensor solutions for the main shock. Aftershock depths range from 2.5 to 8 km, placing the sequence in the Cambrian metamorphic rocks of the Eastern Piedmont thrust sheet. We relocated the main shock relative to a well-located Mw 3.5 aftershock using the P-wave arrival times at the five permanent stations. The main shock epicenter lies in the middle of the aftershock zone. Its focal depth, although not well constrained, is similar to the aftershocks. A crustal-scale seismic reflection profile was acquired by the USGS in 1981 along I-64 just 4 km southwest of the nearest aftershocks. This profile runs nearly parallel to the dip direction of the aftershock zone and has been interpreted to contain many ESE-dipping reverse faults in the allochthonous upper crust (Harris et al., 1986; Pratt, et al., 1988). When projected onto the reflection profile the aftershocks locate within a relatively non-reflective zone bounded above and below by prominent bands of more shallowly dipping reflectors reported by Pratt et al. (1988) raising the question whether or not the earthquake reactivated a pre-existing fault. Seismic

  15. B meson decays to charmless meson pairs containing eta or eta'

    SciTech Connect

    Aubert, : B.

    2009-12-14

    The authors present updated measurements of the branching fractions for B{sup 0} meson decays to {eta}K{sup 0}, {eta}{eta}, {eta}{phi}, {eta}{omega}, {eta}{prime}K{sup 0}, {eta}{prime}{eta}{prime}, {eta}{prime}, {phi}, and {eta}{prime}{omega} and branching fractions and CP-violating charge asymmetries for B{sup +} decays to {eta}{pi}{sup +}, {eta}K{sup +}, {eta}{prime}{pi}{sup +}, and {eta}{prime} K{sup +}. The data represent the full dataset of 467 x 10{sup 6} B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. Besides large signals for the four charged B decays modes and for B{sup 0} {yields} {eta}{prime}K{sup 0}, they find evidence for three B{sup 0} decays modes at greater than 3.0{sigma} significance. They find {Beta}(B{sup 0} {yields} {eta}K{sup 0}) = (1.15{sub -0.38}{sup +0.43} {+-} 0.09) x 10{sup -6}, {Beta}(B{sup 0} {yields} {eta}{omega}) = (0.94{sub -0.30}{sup +0.35} {+-} 0.09) x 10{sup -6}, and {Beta}(B{sup 0} {yields} {eta}{prime}{omega}) = (1.01{sub -0.38}{sup +0.46} {+-} 0.09) x 10{sup -6}, where the first (second) uncertainty is statistical (systematic). For the B{sup +} {yields} {eta}K{sup +} decay mode, they measure the charge asymmetry {Alpha}{sub ch} (B{sup +} {yields} {eta}K{sup +}) = -0.36 {+-} 0.11 {+-} 0.03.

  16. The aftershock signature of supershear earthquakes.

    PubMed

    Bouchon, Michel; Karabulut, Hayrullah

    2008-06-01

    Recent studies show that earthquake faults may rupture at speeds exceeding the shear wave velocity of rocks. This supershear rupture produces in the ground a seismic shock wave similar to the sonic boom produced by a supersonic airplane. This shock wave may increase the destruction caused by the earthquake. We report that supershear earthquakes are characterized by a specific pattern of aftershocks: The fault plane itself is remarkably quiet whereas aftershocks cluster off the fault, on secondary structures that are activated by the supershear rupture. The post-earthquake quiescence of the fault shows that friction is relatively uniform over supershear segments, whereas the activation of off-fault structures is explained by the shock wave radiation, which produces high stresses over a wide zone surrounding the fault. PMID:18535239

  17. The aftershock signature of supershear earthquakes.

    PubMed

    Bouchon, Michel; Karabulut, Hayrullah

    2008-06-01

    Recent studies show that earthquake faults may rupture at speeds exceeding the shear wave velocity of rocks. This supershear rupture produces in the ground a seismic shock wave similar to the sonic boom produced by a supersonic airplane. This shock wave may increase the destruction caused by the earthquake. We report that supershear earthquakes are characterized by a specific pattern of aftershocks: The fault plane itself is remarkably quiet whereas aftershocks cluster off the fault, on secondary structures that are activated by the supershear rupture. The post-earthquake quiescence of the fault shows that friction is relatively uniform over supershear segments, whereas the activation of off-fault structures is explained by the shock wave radiation, which produces high stresses over a wide zone surrounding the fault.

  18. All Pillars Point to Eta

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Eta Carinae Starforming RegionSimulated Infrared View of Comet Tempel 1 (artist's concept)

    These false-color image taken by NASA's Spitzer Space Telescope shows the 'South Pillar' region of the star-forming region called the Carina Nebula. Like cracking open a watermelon and finding its seeds, the infrared telescope 'busted open' this murky cloud to reveal star embryos (yellow or white) tucked inside finger-like pillars of thick dust (pink). Hot gases are green and foreground stars are blue. Not all of the newfound star embryos can be easily spotted.

    Though the nebula's most famous and massive star, Eta Carinae, is too bright to be observed by infrared telescopes, the downward-streaming rays hint at its presence above the picture frame. Ultraviolet radiation and stellar winds from Eta Carinae and its siblings have shredded the cloud to pieces, leaving a mess of tendrils and pillars. This shredding process triggered the birth of the new stars uncovered by Spitzer.

    The inset visible-light picture (figure 2) of the Carina Nebula shows quite a different view. Dust pillars are fewer and appear dark because the dust is soaking up visible light. Spitzer's infrared detectors cut through this dust, allowing it to see the heat from warm, embedded star embryos, as well as deeper, more buried pillars. The visible-light picture is from the National Optical Astronomy Observatory.

    Eta Carina is a behemoth of a star, with more than 100 times the mass of our Sun. It is so massive that it can barely hold itself together. Over the years, it has brightened and faded as material has shot away from its surface. Some astronomers think Eta Carinae might die in a supernova blast within our lifetime.

    Eta Carina's home, the Carina Nebula, is located in the southern portion of our Milky Way galaxy, 10,000 light-years from Earth. This colossal cloud of gas and dust

  19. Aftershocks in a frictional earthquake model.

    PubMed

    Braun, O M; Tosatti, Erio

    2014-09-01

    Inspired by spring-block models, we elaborate a "minimal" physical model of earthquakes which reproduces two main empirical seismological laws, the Gutenberg-Richter law and the Omori aftershock law. Our point is to demonstrate that the simultaneous incorporation of aging of contacts in the sliding interface and of elasticity of the sliding plates constitutes the minimal ingredients to account for both laws within the same frictional model. PMID:25314453

  20. Aftershocks in a frictional earthquake model.

    PubMed

    Braun, O M; Tosatti, Erio

    2014-09-01

    Inspired by spring-block models, we elaborate a "minimal" physical model of earthquakes which reproduces two main empirical seismological laws, the Gutenberg-Richter law and the Omori aftershock law. Our point is to demonstrate that the simultaneous incorporation of aging of contacts in the sliding interface and of elasticity of the sliding plates constitutes the minimal ingredients to account for both laws within the same frictional model.

  1. Forecasting large aftershocks within one day after the main shock.

    PubMed

    Omi, Takahiro; Ogata, Yosihiko; Hirata, Yoshito; Aihara, Kazuyuki

    2013-01-01

    Forecasting the aftershock probability has been performed by the authorities to mitigate hazards in the disaster area after a main shock. However, despite the fact that most of large aftershocks occur within a day from the main shock, the operational forecasting has been very difficult during this time-period due to incomplete recording of early aftershocks. Here we propose a real-time method for efficiently forecasting the occurrence rates of potential aftershocks using systematically incomplete observations that are available in a few hours after the main shocks. We demonstrate the method's utility by retrospective early forecasting of the aftershock activity of the 2011 Tohoku-Oki Earthquake of M9.0 in Japan. Furthermore, we compare the results by the real-time data with the compiled preliminary data to examine robustness of the present method for the aftershocks of a recent inland earthquake in Japan.

  2. Forecasting large aftershocks within one day after the main shock

    PubMed Central

    Omi, Takahiro; Ogata, Yosihiko; Hirata, Yoshito; Aihara, Kazuyuki

    2013-01-01

    Forecasting the aftershock probability has been performed by the authorities to mitigate hazards in the disaster area after a main shock. However, despite the fact that most of large aftershocks occur within a day from the main shock, the operational forecasting has been very difficult during this time-period due to incomplete recording of early aftershocks. Here we propose a real-time method for efficiently forecasting the occurrence rates of potential aftershocks using systematically incomplete observations that are available in a few hours after the main shocks. We demonstrate the method's utility by retrospective early forecasting of the aftershock activity of the 2011 Tohoku-Oki Earthquake of M9.0 in Japan. Furthermore, we compare the results by the real-time data with the compiled preliminary data to examine robustness of the present method for the aftershocks of a recent inland earthquake in Japan. PMID:23860594

  3. Triggering of earthquake aftershocks by dynamic stresses

    USGS Publications Warehouse

    Kilb, Debi; Gomberg, J.; Bodin, P.

    2000-01-01

    It is thought that small 'static' stress changes due to permanent fault displacement can alter the likelihood of, or trigger, earthquakes on nearby faults. Many studies of triggering in the nearfield, particularly of aftershocks, rely on these static changes as the triggering agent and consider them only in terms of equivalent changes in the applied load on the fault. Here we report a comparison of the aftershock pattern of the moment magnitude MW = 7.3 Landers earthquake, not only with static stress changes but also with transient, oscillatory stress changes transmitted as seismic waves (that is, 'dynamic' stresses). Dynamic stresses do not permanently change the applied load and thus can trigger earthquakes only by altering the mechanical state or properties of the fault zone. These dynamically weakened faults may fail after the seismic waves have passed by, and might even cause earthquakes that would not otherwise have occurred. We find similar asymmetries in the aftershock and dynamic stress patterns, the latter being due to rupture propagation, whereas the static stress changes lack this asymmetry. Previous studies have shown that dynamic stresses can promote failure at remote distances, but here we show that they can also do so nearby.

  4. Triggering of earthquake aftershocks by dynamic stresses.

    PubMed

    Kilb, D; Gomberg, J; Bodin, P

    2000-11-30

    It is thought that small 'static' stress changes due to permanent fault displacement can alter the likelihood of, or trigger, earthquakes on nearby faults. Many studies of triggering in the near-field, particularly of aftershocks, rely on these static changes as the triggering agent and consider them only in terms of equivalent changes in the applied load on the fault. Here we report a comparison of the aftershock pattern of the moment magnitude Mw = 7.3 Landers earthquake, not only with static stress changes but also with transient, oscillatory stress changes transmitted as seismic waves (that is, 'dynamic' stresses). Dynamic stresses do not permanently change the applied load and thus can trigger earthquakes only by altering the mechanical state or properties of the fault zone. These dynamically weakened faults may fail after the seismic waves have passed by, and might even cause earthquakes that would not otherwise have occurred. We find similar asymmetries in the aftershock and dynamic stress patterns, the latter being due to rupture propagation, whereas the static stress changes lack this asymmetry. Previous studies have shown that dynamic stresses can promote failure at remote distances, but here we show that they can also do so nearby.

  5. Do aftershock probabilities decay with time?

    USGS Publications Warehouse

    Michael, Andrew J.

    2012-01-01

    So, do aftershock probabilities decay with time? Consider a thought experiment in which we are at the time of the mainshock and ask how many aftershocks will occur a day, week, month, year, or even a century from now. First we must decide how large a window to use around each point in time. Let's assume that, as we go further into the future, we are asking a less precise question. Perhaps a day from now means 1 day 10% of a day, a week from now means 1 week 10% of a week, and so on. If we ignore c because it is a small fraction of a day (e.g., Reasenberg and Jones, 1989, hereafter RJ89), and set p = 1 because it is usually close to 1 (its value in the original Omori law), then the rate of earthquakes (K=t) decays at 1=t. If the length of the windows being considered increases proportionally to t, then the number of earthquakes at any time from now is the same because the rate decrease is canceled by the increase in the window duration. Under these conditions we should never think "It's a bit late for this to be an aftershock."

  6. Enantiocontrolled synthesis of highly functionalized tropanes via [5 + 2] cycloaddition to eta(3)-pyridinylmolybdenum pi-complexes.

    PubMed

    Malinakova, H C; Liebeskind, L S

    2000-11-30

    [reaction: see text] A chiral, nonracemic eta(3)-pyridinyl scaffold participates in [5 + 2] cycloaddition with electron-deficient alkenes, an allene, and an alkyne to give eta(3)-allylmolybdenum bicyclic adducts. The adducts can be demetalated, providing a convergent route to highly functionalized tropanes. High enantiocontrol can be achieved throughout the cycloaddition and demetalation sequence.

  7. Improved understanding of aftershock triggering by waveform detection of aftershocks with GPU computing

    NASA Astrophysics Data System (ADS)

    Peng, Z.; Meng, X.; Hong, B.; Yu, X.

    2012-12-01

    Large shallow earthquakes are generally followed by increased seismic activities around the mainshock rupture zone, known as "aftershocks". Whether static or dynamic triggering is responsible for triggering aftershocks is still in debate. However, aftershocks listed in standard earthquake catalogs are generally incomplete immediately after the mainshock, which may result in inaccurate estimation of seismic rate changes. Recent studies have used waveforms of existing earthquakes as templates to scan through continuous waveforms to detect potential missing aftershocks, which is termed 'matched filter technique'. However, this kind of data mining is computationally intensive, which raises new challenges when applying to large data sets with tens of thousands of templates, hundreds of seismic stations and years of continuous waveforms. The waveform matched filter technique exhibits parallelism at multiple levels, which allows us to use GPU-based computation to achieve significant acceleration. By dividing the procedure into several routines and processing them in parallel, we have achieved ~40 times speedup for one Nvidia GPU card compared to sequential CPU code, and further scaled the code to multiple GPUs. We apply this paralleled code to detect potential missing aftershocks around the 2003 Mw 6.5 San Simeon and 2004 Mw6.0 Parkfield earthquakes in Central California, and around the 2010 Mw 7.2 El Mayor-Cucapah earthquake in southern California. In all these cases, we can detect several tens of times more earthquakes immediately after the mainshocks as compared with those listed in the catalogs. These newly identified earthquakes are revealing new information about the physical mechanisms responsible for triggering aftershocks in the near field. We plan to improve our code so that it can be executed in large-scale GPU clusters. Our work has the long-term goal of developing scalable methods for seismic data analysis in the context of "Big Data" challenges.

  8. Increasing lengths of aftershock zones with depths of moderate-size earthquakes on the San Jacinto Fault suggests triggering of deep creep in the middle crust

    NASA Astrophysics Data System (ADS)

    Meng, Xiaofeng; Peng, Zhigang

    2016-01-01

    Recent geodetic studies along the San Jacinto Fault (SJF) in southern California revealed a shallower locking depth than the seismogenic depth outlined by microseismicity. This disagreement leads to speculations that creeping episodes drive seismicity in the lower part of the seismogenic zone. Whether deep creep occurs along the SJF holds key information on how fault slips during earthquake cycle and potential seismic hazard imposed to southern California. Here we apply a matched filter technique to 10 M > 4 earthquake sequences along the SJF since 2000 and obtain more complete earthquake catalogues. We then systematic investigate spatio-temporal evolutions of these aftershock sequences. We find anomalously large aftershock zones for earthquakes occurred below the geodetically inferred locking depth (i.e. 11-12 km), while aftershock zones of shallower main shocks are close to expectations from standard scaling relationships. Although we do not observe clear migration of aftershocks, most aftershock zones do expand systematically with logarithmic time since the main shock. All the evidences suggest that aftershocks near or below the locking depth are likely driven by deep creep following the main shock. The presence of a creeping zone below 11-12 km may have significant implications on the maximum sizes of events in this region.

  9. Rare semileptonic B{sub s} decays to {eta} and {eta}' mesons in QCD

    SciTech Connect

    Azizi, K.; Khosravi, R.; Falahati, F.

    2010-12-01

    We analyze the rare semileptonic B{sub s}{yields}({eta},{eta}{sup '})l{sup +}l{sup -}, (l=e,{mu},{tau}), and B{sub s}{yields}({eta},{eta}{sup '}){nu}{nu} transitions probing the ss content of the {eta} and {eta}{sup '} mesons via three-point QCD sum rules. We calculate responsible form factors for these transitions in full theory. Using the obtained form factors, we also estimate the related branching fractions and longitudinal lepton polarization asymmetries. Our results are in a good consistency with the predictions of the other existing nonperturbative approaches.

  10. Early aftershock decay rate of the M6 Parkfield earthquake

    NASA Astrophysics Data System (ADS)

    Peng, Z.; Vidale, J. E.

    2004-12-01

    Mainshock rupture is typically followed by its aftershocks that diminish in rate approximately as the reciprocal of the elapse time. However, it is notoriously difficult to observe aftershock activity in the noisy aftermath of larger earthquakes. Many aftershocks were missed in the existing seismicity catalogs in the initial few minutes (Kagan, 2004). Yet this period holds valuable information about the transition from mainshock rupture to sporadic aftershocks, and the friction laws that control earthquakes. The Parkfield section of the San Andreas fault is one of most densely seismometered places in the world. Many near-fault, non-clipped and continuous recordings of the M6 Parkfield earthquake and its aftermath have been recovered, providing an excellent opportunity for us to study the aftershock decay rates in the first few hundred seconds after the mainshock. We have so far analyzed recordings from station PKD and 13 stations in the Parkfield High Resolution Seismic Network. By scrutinizing the high-frequency signal, we are able to distinguish mainshock coda from early aftershocks. We find up to 10 times more aftershocks in the first 1000 s than in the USGS NCSN catalog. More than 30 events are detected in the first 200 s after the mainshock. None of these events are in the USGS NCSN catalog. Preliminary results suggest a strong deficit of aftershocks in the first 100 s after the mainshock relative to a 1/t aftershock rate decay. This pattern is consistent with a lack of seismicity in the first 120 s following the 10/31/2001 M5.1 Anza earthquake (Kilb et al., 2004), and our study of early aftershock rates using data from HiNet array in Japan (Vidale et al., 2004). Our observations will allow us to test the prediction of such an interval in rate-and-state friction models prior to the onset of the 1/t aftershock decay rate (Dieterich, 1994).

  11. A New Hybrid STEP/Coulomb model for Aftershock Forecasting

    NASA Astrophysics Data System (ADS)

    Steacy, S.; Jimenez, A.; Gerstenberger, M.

    2014-12-01

    Aftershock forecasting models tend to fall into two classes - purely statistical approaches based on clustering, b-value, and the Omori-Utsu law; and Coulomb rate-state models which relate the forecast increase in rate to the magnitude of the Coulomb stress change. Recently, hybrid models combining physical and statistical forecasts have begun to be developed, for example by Bach and Hainzl (2012) and Steacy et al. (2013). The latter approach combined Coulomb stress patterns with the STEP (short-term earthquake probability) model by redistributing expected rate from areas with decreased stress to regions where the stress had increased. The chosen 'Coulomb Redistribution Parameter' (CRP) was 0.93, based on California earthquakes, which meant that 93% of the total rate was expected to occur where the stress had increased. The model was tested against the Canterbury sequence and the main result was that the new model performed at least as well as, and often better than, STEP when tested against retrospective data but that STEP was generally better in pseudo-prospective tests that involved data actually available within the first 10 days of each event of interest. The authors suggested that the major reason for this discrepancy was uncertainty in the slip models and, particularly, in the geometries of the faults involved in each complex major event. Here we develop a variant of the STEP/Coulomb model in which the CRP varies based on the percentage of aftershocks that occur in the positively stressed areas during the forecast learning period. We find that this variant significantly outperforms both STEP and the previous hybrid model in almost all cases, even when the input Coulomb model is quite poor. Our results suggest that this approach might be more useful than Coulomb rate-state when the underlying slip model is not well constrained due to the dependence of that method on the magnitude of the Coulomb stress change.

  12. Statistical Discrimination of Induced and Tectonic Earthquake Sequences in Central and Eastern US Based on Waveform Detected Catalogs

    NASA Astrophysics Data System (ADS)

    Meng, X.; Peng, Z.

    2014-12-01

    It is now well established that extraction of fossil fuels and/or waste water disposal do cause earthquakes in Central and Eastern United States (CEUS). However, the physics underneath of the nucleation of induced earthquakes still remain elusive. In particular, do induced and tectonic earthquake sequences in CEUS share the same statistics, for example the Omori's law [Utsu et al., 1995] and the Gutenberg-Richter's law? Some studies have show that most naturally occurring earthquake sequences are driven by cascading-type triggering. Hence, they would follow the typical Gutenberg-Richter relation and Omori's aftershock decay and could be well described by multi-dimensional point-process models such as Epidemic Type Aftershock Sequence (ETAS) [Ogata, 1988; Zhuang et al., 2012]. However, induced earthquakes are likely driven by external forcing such as injected fluid pressure, and hence would not be well described by the ETAS model [Llenos and Michael, 2013]. Existing catalogs in CEUS (e.g. the ANSS catalog) have relatively high magnitude of completeness [e.g., Van Der Elst et al., 2013] and hence may not be ideal for a detailed ETAS modeling analysis. A waveform matched filter technique has been successfully applied to detect many missing earthquakes in CEUS with a sparse network in Illinois [Yang et al., 2009] and on single station in Texas, Oklahoma and Colorado [e.g., Van Der Elst et al., 2013]. In addition, the deployment of the USArray station in CEUS also helped to expand the station coverage. In this study, we systematically detect missing events during 14 moderate-size (M>=4) earthquake sequences since 2000 in CEUS and quantify their statistical parameters (e.g. b, a, K, and p values) and spatio-temporal evolutions. Then we compare the statistical parameters and the spatio-temporal evolution pattern between induced and naturally occurring earthquake sequences to see if one or more diagnostic parameters exist. Our comprehensive analysis of earthquake sequences

  13. Local near instantaneously dynamically triggered aftershocks of large earthquakes

    NASA Astrophysics Data System (ADS)

    Fan, Wenyuan; Shearer, Peter M.

    2016-09-01

    Aftershocks are often triggered by static- and/or dynamic-stress changes caused by mainshocks. The relative importance of the two triggering mechanisms is controversial at near-to-intermediate distances. We detected and located 48 previously unidentified large early aftershocks triggered by earthquakes with magnitudes between ≥7 and 8 within a few fault lengths (approximately 300 kilometers), during times that high-amplitude surface waves arrive from the mainshock (less than 200 seconds). The observations indicate that near-to-intermediate-field dynamic triggering commonly exists and fundamentally promotes aftershock occurrence. The mainshocks and their nearby early aftershocks are located at major subduction zones and continental boundaries, and mainshocks with all types of faulting-mechanisms (normal, reverse, and strike-slip) can trigger early aftershocks.

  14. Local near instantaneously dynamically triggered aftershocks of large earthquakes.

    PubMed

    Fan, Wenyuan; Shearer, Peter M

    2016-09-01

    Aftershocks are often triggered by static- and/or dynamic-stress changes caused by mainshocks. The relative importance of the two triggering mechanisms is controversial at near-to-intermediate distances. We detected and located 48 previously unidentified large early aftershocks triggered by earthquakes with magnitudes between ≥7 and 8 within a few fault lengths (approximately 300 kilometers), during times that high-amplitude surface waves arrive from the mainshock (less than 200 seconds). The observations indicate that near-to-intermediate-field dynamic triggering commonly exists and fundamentally promotes aftershock occurrence. The mainshocks and their nearby early aftershocks are located at major subduction zones and continental boundaries, and mainshocks with all types of faulting-mechanisms (normal, reverse, and strike-slip) can trigger early aftershocks.

  15. Local near instantaneously dynamically triggered aftershocks of large earthquakes.

    PubMed

    Fan, Wenyuan; Shearer, Peter M

    2016-09-01

    Aftershocks are often triggered by static- and/or dynamic-stress changes caused by mainshocks. The relative importance of the two triggering mechanisms is controversial at near-to-intermediate distances. We detected and located 48 previously unidentified large early aftershocks triggered by earthquakes with magnitudes between ≥7 and 8 within a few fault lengths (approximately 300 kilometers), during times that high-amplitude surface waves arrive from the mainshock (less than 200 seconds). The observations indicate that near-to-intermediate-field dynamic triggering commonly exists and fundamentally promotes aftershock occurrence. The mainshocks and their nearby early aftershocks are located at major subduction zones and continental boundaries, and mainshocks with all types of faulting-mechanisms (normal, reverse, and strike-slip) can trigger early aftershocks. PMID:27609887

  16. Measurement of branching fractions and charge asymmetries in B+ decays to eta pi+, eta K+, eta rho+, and eta' pi+, and search for B0 decays to eta K0 and eta omega.

    PubMed

    Aubert, B; Barate, R; Boutigny, D; Couderc, F; Karyotakis, Y; Lees, J P; Poireau, V; Tisserand, V; Zghiche, A; Grauges-Pous, E; Palano, A; Pappagallo, M; Pompili, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Borgland, A W; Breon, A B; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Day, C T; Gill, M S; Gritsan, A V; Groysman, Y; Jacobsen, R G; Kadel, R W; Kadyk, J; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lynch, G; Mir, L M; Oddone, P J; Orimoto, T J; Pripstein, M; Roe, N A; Ronan, M T; Wenzel, W A; Barrett, M; Ford, K E; Harrison, T J; Hart, A J; Hawkes, C M; Morg An, S E; Watson, A T; Fritsch, M; Goetzen, K; Held, T; Koch, H; Lewandowski, B; Pelizaeus, M; Peters, K; Schroeder, T; Steinke, M; Boyd, J T; Burke, J P; Chevalier, N; Cottingham, W N; Kelly, M P; Cuhadar-Donszelmann, T; Hearty, C; Knecht, N S; Mattison, T S; McKenna, J A; Thiessen, D; Khan, A; Kyberd, P; Teodorescu, L; Blinov, A E; Blinov, V E; Bukin, A D; Druzhinin, V P; Golubev, V B; Ivanchenko, V N; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Yushkov, A N; Best, D; Bondioli, M; Bruinsma, M; Chao, M; Eschrich, I; Kirkby, D; Lankford, A J; Mandelkern, M; Mommsen, R K; Roethel, W; Stoker, D P; Buchanan, C; Hartfiel, B L; Weinstein, A J R; Foulkes, S D; Gary, J W; Long, O; Shen, B C; Wang, K; Zhang, L; Del Re, D; Hadavand, H K; Hill, E J; Macfarlane, D B; Paar, H P; Rahatlou, Sh; Sharma, V; Berryhill, J W; Campagnari, C; Cunha, A; Dahmes, B; Hong, T M; Lu, A; Mazur, M A; Richman, J D; Verkerke, W; Beck, T W; Eisner, A M; Flacco, C J; Heusch, C A; Kroseberg, J; Lockman, W S; Nesom, G; Schalk, T; Schumm, B A; Seiden, A; Spradlin, P; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dubois-Felsmann, G P; Dvoretskii, A; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Ryd, A; Samuel, A; Yang, S; Jayatilleke, S; Mancinelli, G; Meadows, B T; Sokoloff, M D; Blanc, F; Bloom, P; Chen, S; Derrington, I M; Ford, W T; Nauenberg, U; Olivas, A; Rankin, P; Ruddick, W O; Smith, J G; Ulmer, K A; Zhang, J; Chen, A; Eckhart, E A; Harton, J L; Soffer, A; Toki, W H; Wilson, R J; Zeng, Q; Spaan, B; Altenburg, D; Brandt, T; Brose, J; Dickopp, M; Feltresi, E; Hauke, A; Lacker, H M; Maly, E; Nogowski, R; Otto, S; Petzold, A; Schott, G; Schubert, J; Schubert, K R; Schwierz, R; Sundermann, J E; Bernard, D; Bonneaud, G R; Grenier, P; Schrenk, S; Thiebaux, Ch; Vasileiadis, G; Verderi, M; Bard, D J; Clark, P J; Gradl, W; Muheim, F; Playfer, S; Xie, Y; Andreotti, M; Azzolini, V; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Piemontese, L; Sarti, A; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Zallo, A; Buzzo, A; Capra, R; Contri, R; Lo Vetere, M; Macri, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Bailey, S; Brandenburg, G; Chaisanguanthum, K S; Morii, M; Won, E; Dubitzky, R S; Langenegger, U; Marks, J; Uwer, U; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Gaillard, J R; Morton, G W; Nash, J A; Nikolich, M B; Taylor, G P; Charles, M J; Grenier, G J; Mallik, U; Cochran, J; Crawley, H B; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Yi, J; Arnaud, N; Davier, M; Giroux, X; Grosdidier, G; Höcker, A; Le Diberder, F; Lepeltier, V; Lutz, A M; Petersen, T C; Pierini, M; Plaszczynski, S; Rodier, S; Roudeau, P; Schune, M H; Stocchi, A; Wormser, G; Cheng, C H; Lange, D J; Simani, M C; Wright, D M; Bevan, A J; Chavez, C A; Coleman, J P; Forster, I J; Fry, J R; Gabathuler, E; Gamet, R; George, K A; Hutchcroft, D E; Parry, R J; Payne, D J; Touramanis, C; Cormack, C M; Di Lodovico, F; Brown, C L; Cowan, G; Flack, R L; Flaecher, H U; Green, M G; Jackson, P S; McMahon, T R; Ricciardi, S; Salvatore, F; Winter, M A; Brown, D; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Hodgkinson, M C; Lafferty, G D; Naisbit, M T; Williams, J C; Chen, C; Farbin, A; Hulsbergen, W D; Jawahery, A; Kovalskyi, D; Lae, C K; Lillard, V; Roberts, D A; Blaylock, G; Dallapiccola, C; Hertzbach, S S; Kofler, R; Koptchev, V B; Moore, T B; Saremi, S; Staengle, H; Willocq, S; Cowan, R; Koeneke, K; Sciolla, G; Sekula, S J; Taylor, F; Yamamoto, R K; Patel, P M; Robertson, S H; Lazzaro, A; Lombardo, V; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Reidy, J; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Taras, P; Nicholson, H; Cavallo, N; De Nardo, G; Fabozzi, F; Gatto, C; Lista, L; Monorchio, D; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M; Bulten, H; Raven, G; Snoek, H L; Wilden, L; Jessop, C P; Losecco, J M; Allmendinger, T; Benelli, G; Gan, K K; Honscheid, K; Hufnagel, D; Kagan, H; Kass, R; Pulliam, T; Rahimi, A M; Ter-Antonyan, R; Wong, Q K; Brau, J; Frey, R; Igonkina, O; Lu, M; Potter, C T; Sinev, N B; Strom, D; Torrence, E; Colecchia, F; Dorigo, A; Galeazzi, F; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Benayoun, M; Briand, H; Chauveau, J; David, P; Del Buono, L; de la Vaissière, Ch; Hamon, O; John, M J J; Leruste, Ph; Malclès, J; Ocariz, J; Roos, L; Therin, G; Behera, P K; Gladney, L; Guo, Q H; Panetta, J; Biasini, M; Covarelli, R; Pioppi, M; Angelini, C; Batignani, G; Bettarini, S; Bucci, F; Calderini, G; Carpinelli, M; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Morganti, M; Neri, N; Paoloni, E; Rama, M; Rizzo, G; Simi, G; Walsh, J; Haire, M; Judd, D; Paick, K; Wagoner, D E; Danielson, N; Elmer, P; Lau, Y P; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Bellini, F; Cavoto, G; D'Orazio, A; Di Marco, E; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Li Gioi, L; Mazzoni, M A; Morganti, S; Piredda, G; Polci, F; Tehrani, F Safai; Voena, C; Christ, S; Schröder, H; Wagner, G; Waldi, R; Adye, T; De Groot, N; Franek, B; Gopal, G P; Olaiya, E O; Wilson, F F; Aleksan, R; Emery, S; Gaidot, A; Ganzhur, S F; Giraud, P-F; Graziani, G; Hamel de Monchenault, G; Kozanecki, W; Legendre, M; London, G W; Mayer, B; Vasseur, G; Yèche, Ch; Zito, M; Purohit, M V; Weidemann, A W; Wilson, J R; Yumiceva, F X; Abe, T; Allen, M T; Aston, D; Bartoldus, R; Berger, N; Boyarski, A M; Buchmueller, O L; Claus, R; Convery, M R; Cristinziani, M; Dingfelder, J C; Dong, D; Dorfan, J; Dujmic, D; Dunwoodie, W; Fan, S; Field, R C; Glanzman, T; Gowdy, S J; Hadig, T; Halyo, V; Hast, C; Hryn'ova, T; Innes, W R; Kelsey, M H; Kim, P; Kocian, M L; Leith, D W G S; Libby, J; Luitz, S; Luth, V; Lynch, H L; Marsiske, H; Messner, R; Mohapatra, A K; Muller, D R; O'grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Snyder, A; Soha, A; Stelzer, J; Strube, J; Su, D; Sullivan, M K; Thompson, J M; Va'vra, J; Wagner, S R; Weaver, M; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Young, C C; Burchat, P R; Edwards, A J; Majewski, S A; Petersen, B A; Roat, C; Ahmed, M; Ahmed, S; Alam, M S; Ernst, J A; Saeed, M A; Saleem, M; Wappler, F R; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Kim, H; Ritchie, J L; Satpathy, A; Schwitters, R F; Izen, J M; Kitayama, I; Lou, X C; Ye, S; Bianchi, F; Bona, M; Gallo, F; Gamba, D; Bomben, M; Bosisio, L; Cartaro, C; Cossutti, F; Della Ricca, G; Dittongo, S; Grancagnolo, S; Lanceri, L; Poropat, P; Vitale, L; Vuagnin, G; Martinez-Vidal, F; Panvini, R S; Banerjee, Sw; Bhuyan, B; Brown, C M; Fortin, D; Hamano, K; Jackson, P D; Kowalewski, R; Roney, J M; Sobie, R J; Back, J J; Harrison, P F; Latham, T E; Mohanty, G B; Band, H R; Chen, X; Cheng, B; Dasu, S; Datta, M; Eichenbaum, A M; Flood, K T; Graham, M; Hollar, J J; Johnson, J R; Kutter, P E; Li, H; Liu, R; Mellado, B; Mihalyi, A; Pan, Y; Prepost, R; Tan, P; von Wimmersperg-Toeller, J H; Wu, J; Wu, S L; Yu, Z; Greene, M G; Neal, H

    2005-09-23

    We present measurements of branching fractions and charge asymmetries for six B-meson decay modes with an eta or eta(') meson in the final state. The data sample corresponds to 232 x 10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) B Factory at SLAC. We measure the branching fractions (in units of 10(-6)): B(B+ -->eta pi(+))=5.1+/-0.6+/-0.3, B(B+ etaK+)=3.3+/-0.6+/-0.3, B(B0-->etaK0)=1.5+/-0.7+/-0.1 (<2.5 at 90% C.L.), B(B+-->eta rho(+))=8.4+/-1.9+/-1.1, B(B0-->eta omiga)=1.0+/-0.5+/-0.2 (<1.9 at 90% C.L.), and B(B+-->eta(')pi(+))=4.0+/-0.8+/-0.4, where the first uncertainty is statistical and second systematic. For the charged modes we also determine the charge asymmetries, all found to be compatible with zero.

  17. Recent results on eta and eta-prime photoproduction on the proton

    SciTech Connect

    Barry Ritchie

    2004-06-01

    The experimental situation on eta and eta' photoproduction on the proton is reviewed, emphasizing progress made since 2001. New preliminary results for eta' photoproduction on the proton from Jefferson Lab are presented. Experimental results are compared with several theoretical approaches, with an emphasis on consequences for understanding baryon spectroscopy.

  18. Aftershocks halted by static stress shadows

    NASA Astrophysics Data System (ADS)

    Toda, Shinji; Stein, Ross S.; Beroza, Gregory C.; Marsan, David

    2012-06-01

    Earthquakes impart static and dynamic stress changes to the surrounding crust. Sudden fault slip causes small but permanent--static--stress changes, and passing seismic waves cause large, but brief and oscillatory--dynamic--stress changes. Because both static and dynamic stresses can trigger earthquakes within several rupture dimensions of a mainshock, it has proven difficult to disentangle their contributions to the triggering process. However, only dynamic stress can trigger earthquakes far from the source, and only static stress can create stress shadows, where the stress and thus the seismicity rate in the shadow area drops following an earthquake. Here we calculate the stress imparted by the magnitude 6.1 Joshua Tree and nearby magnitude 7.3 Landers earthquakes that occurred in California in April and June 1992, respectively, and measure seismicity through time. We show that, where the aftershock zone of the first earthquake was subjected to a static stress increase from the second, the seismicity rate jumped. In contrast, where the aftershock zone of the first earthquake fell under the stress shadow of the second and static stress dropped, seismicity shut down. The arrest of seismicity implies that static stress is a requisite element of spatial clustering of large earthquakes and should be a constituent of hazard assessment.

  19. 3D imaging of crustal structure under the Piedmont province in central Virginia, from reflection RVSP processing of aftershock recordings from the August 23, 2011 Virginia earthquake

    NASA Astrophysics Data System (ADS)

    Quiros, D. A.; Brown, L. D.; Cabolova, A.; Davenport, K. K.; Hole, J. A.; Mooney, W. D.

    2013-12-01

    Aftershocks from the magnitude Mw 5.8 August 23, 2011, central Virginia earthquake were recorded using an unusually dense array of seismometers in what has been termed an AIDA (Aftershock Imaging with Dense Arrays) deployment. Over 200 stations were deployed in the epicentral region of this event to a) more precisely determine hypocentral locations, b) more accurately define velocity structure in the aftershock zone, c) characterize propagation characteristics of the crust in the area, and d) image geologic structures in the hypocentral volume with reflection techniques using aftershocks as sources. The AIDA-Virginia experiment successfully recorded a large number of aftershocks from which local tomographic velocity estimates and accurate hypocentral locations were obtained. These results facilitated the use of aftershocks as sources for reflection imaging. In this study we demonstrate how earthquake sources recorded by surface arrays can be treated using the imaging techniques associated with Vertical Seismic Profiling (VSP), in particular a variant known as Reverse VSP (RVSP). The central VSP processing algorithms used for this study are VSP normal moveout (VSPnmo) and VSP-to-Common Reflection Point (CRP). Applying these techniques to individual aftershocks from the Virginia experiment results in 3D reflection images of structural complexity in the immediate vicinity of the aftershocks. The most prominent feature observed on these 3D images is a strong moderately east-dipping reflector at a depth of approximately 6 to 8 km that directly underlies, and is continuous beneath, the more steeply dipping aftershock zone. We interpret this reflector as part of a complex imbricate thrust sequence associated with Paleozoic convergence during the Appalachian orogeny. Its apparent continuity beneath the fault zone implied by the aftershock's hypocenters suggests that this inferred fault zone has little or no cumulative offset, supporting the speculation that this event

  20. Experimental test accelerator (ETA) II

    SciTech Connect

    Fessenden, T.J.; Atchison, W.L.; Birx, D.L.

    1981-03-06

    The Experimental Test Accelerator (ETA) is designed to produce a 10 kAmp electron beam at an energy of 4.5 MeV in 40 nsec pulses at an average rate of 2 pps. The accelerator also operates in bursts of 5 pulses spaced by as little as one millisec at an average rate of 5 pps. The machine is currently operating near 80% of its design values and has accumulated over 2.5 million pulses - mostly at a rate of one pps. The plasma cathode electron source, the remainder of the accelerator, and the operating characteristics of the machine are discussed.

  1. Delineating complex spatiotemporal distribution of earthquake aftershocks: an improved Source-Scanning Algorithm

    NASA Astrophysics Data System (ADS)

    Liao, Yen-Che; Kao, Honn; Rosenberger, Andreas; Hsu, Shu-Kun; Huang, Bor-Shouh

    2012-06-01

    Conventional earthquake location methods depend critically on the correct identification of seismic phases and their arrival times from seismograms. Accurate phase picking is particularly difficult for aftershocks that occur closely in time and space, mostly because of the ambiguity of correlating the same phase at different stations. In this study, we introduce an improved Source-Scanning Algorithm (ISSA) for the purpose of delineating the complex distribution of aftershocks without time-consuming and labour-intensive phase-picking procedures. The improvements include the application of a ground motion analyser to separate P and S waves, the automatic adjustment of time windows for 'brightness' calculation based on the scanning resolution and a modified brightness function to combine constraints from multiple phases. Synthetic experiments simulating a challenging scenario are conducted to demonstrate the robustness of the ISSA. The method is applied to a field data set selected from the ocean-bottom-seismograph records of an offshore aftershock sequence southwest of Taiwan. Although visual inspection of the seismograms is ambiguous, our ISSA analysis clearly delineates two events that can best explain the observed waveform pattern.

  2. Eta Carinae: an Astrophysical Laboratory

    NASA Astrophysics Data System (ADS)

    Nielsen, Krister E.; Gull, Theodore R.

    2009-05-01

    Eta Carinae provides a unique example to investigate a massive star in a late evolutionary phase and how CNO-processed material is ejected and mixed with the interstellar medium. The absorbing gas surrounding Eta Carinae (η Car) shows similar characteristics to the intervening gas in spectra of gamma ray burst progenitors. Consequently, the η Car spectrum may provide clues about the nature of other extreme objects such as hypernovae and supernova impostors. In the 1840s, η Car underwent a massive ejection, which was repeated to a lesser extent in the 1890s. Today we see the Homunculus, a bipolar expanding neutral shell, and the Little Homunculus, an interior, spectroscopically time-variable, ionized structure. The η Car system is ideal as a laboratory for absorption and emission line spectroscopy. In the line-of-sight towards η Car, multiple narrow absorption lines are observed from environments with densities around 107 cm- 3 and temperatures ranging from 60 to 7000 K. Thousands of neutral/singly ionized metal lines are identified, in addition to molecular lines in species such as H2, CH, OH and NH. The input from the laboratory spectroscopy community has furthered the analysis of η Car. Future observations of η Car in the infrared through radio wavelength region will enable new detections of atomic and molecular transitions, most notably of hydrides and nitrides. We will demonstrate how experimentally derived atomic data have improved our spectral analysis, and illuminate where future work is needed.

  3. Identification of a major segment boundary between two megathrust subduction zone earthquakes from aftershock seismicity

    NASA Astrophysics Data System (ADS)

    Sobiesiak, M.; Victor, P.; Eggert, S.

    2009-04-01

    Aftershock seismicity is commonly used to characterize the extent of rupture planes of megathrust earthquakes. From unique datasets, covering the two adjacent fault planes of the Mw 8.0, 1995, Antofagasta and the Mw 7.7, 2007, Tocopilla earthquakes, we were able to identify a segment boundary (SB), located beneath Mejillones Peninsula. This segment boundary hosted the onset of the Antofagasta rupture and constituted the end of the Tocopilla rupture plane. The data recorded during the mission of the German Task Force for Earthquakes after the 2007 Tocopilla earthquake is supporting our observations regarding the northern part of the SB. 34 seismological stations registered the aftershocks from November 2007 until May 2008. First hypocenter determinations show that the aftershock sequences of both events meet along this E-W oriented segment boundary. The segment boundary is furthermore conformed by the historic record of megathrust events. Evidence for long term persistency of this SB comes from geological observations as differential uplift rates across the boundary and different fault patterns. Geomorpholocical analysis defines a topographic anomaly ~ 20 km wide and oriented along strike the SB..The main shock hypocenter determinations (NEIC, local network, ISC) which are related to the start of the rupture are all located in this zone. The SB is further characterized by intermediate b-values derived from a spatial b-value study of the Antofagasta fault plane and hosts several elongated clusters of aftershock seismicity. A detailed study of the focal mechanism solutions in one of these clusters showed a number of aligned strike slip events with one E-W striking nodal plane having a strike angle which is similar to the angle of subduction obliquity of the oceanic Nazca plate in this area. In further investigations we will search for detailed information on the nature and dynamics of processes along such a segment boundary, their meaning for the initiation of large

  4. Correlation of foreshocks and aftershocks and asperities

    NASA Astrophysics Data System (ADS)

    Hsu, Vindell; Helsley, Charles E.; Berg, Eduard; Novelo-Casanova, David A.

    1984-11-01

    A close correlation in spatial distribution of local seismic activity and energy release patterns before and after the 1979 Petatlan, Mexico earthquake suggests heterogeneity within the fault plane of this major low-angle thrust event associated with subduction along the Middle America Trench. A simple two-asperity model is proposed to account for the complexity. Foreshocks and aftershocks of the neighboring 1981 Playa Azul earthquake showed a similar pattern. As both events occurred at the junction of the Orozco Fracture Zone and the Middle America Trench, we speculate that the observed complex fault plane is caused by subduction of the rugged ocean floor of the Orozco Fracture Zone. Short-term precursory seismicity prior to the Petatlan earthquake can be explained by using the asperity model and migration of a slip front from the south-east to the north-west across the main shock source region.

  5. Aftershock triggering by complete Coulomb stress changes

    USGS Publications Warehouse

    Kilb, Debi; Gomberg, J.; Bodin, P.

    2002-01-01

    We examine the correlation between seismicity rate change following the 1992, M7.3, Landers, California, earthquake and characteristics of the complete Coulomb failure stress (CFS) changes (??CFS(t)) that this earthquake generated. At close distances the time-varying "dynamic" portion of the stress change depends on how the rupture develops temporally and spatially and arises from radiated seismic waves and from permanent coseismic fault displacement. The permanent "static" portion (??CFS) depends only on the final coseismic displacement. ??CFS diminishes much more rapidly with distance than the transient, dynamic stress changes. A common interpretation of the strong correlation between ??CFS and aftershocks is that load changes can advance or delay failure. Stress changes may also promote failure by physically altering properties of the fault or its environs. Because it is transient, ??CFS(t) can alter the failure rate only by the latter means. We calculate both ??CFS and the maximum positive value of ??CFS(t) (peak ??CFS(t)) using a reflectivity program. Input parameters are constrained by modeling Landers displacement seismograms. We quantify the correlation between maps of seismicity rate changes and maps of modeled ??CFS and peak ??CFS(t) and find agreement for both models. However, rupture directivity, which does not affect ??CFS, creates larger peak ??CFS(t) values northwest of the main shock. This asymmetry is also observed in seismicity rate changes but not in ??CFS. This result implies that dynamic stress changes are as effective as static stress changes in triggering aftershocks and may trigger earthquakes long after the waves have passed.

  6. Pseudoscalar glueball and {eta}-{eta}{sup '} mixing

    SciTech Connect

    Mathieu, Vincent; Vento, Vicente

    2010-02-01

    We have performed a dynamical analysis of the mixing in the pseudoscalar channel with the goal of understanding the existence and behavior of the pseudoscalar glueball. Our philosophy has not been to predict precise values of the glueball mass but to exploit an adequate effective theory to the point of breaking and to analyze which kind of mechanisms restore compatibility with data. Our study has led to analytical solutions which allow a clear understanding of the phenomena. The outcome of our calculation leads to a large mass glueball M{sub {Theta}>}2000 MeV, to a large glue content of the {eta}{sup '}, and to mixing angles in agreement with previous numerical studies.

  7. The 3-D aftershock distribution of three recent M5~5.5 earthquakes in the Anza region,California

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Wdowinski, S.; Lin, G.

    2011-12-01

    The San Jacinto fault zone (SJFZ) exhibits the highest level of seismicity compared to other regions in southern California. On average, it produces four earthquakes per day, most of them at depth of 10-17 km. Over the past decade, an increasing seismic activity occurred in the Anza region, which included three M5~5.5 events and their aftershock sequences. These events occurred in 2001, 2005, and 2010. In this research we map the 3-D distribution of these three events to evaluate their rupture geometry and better understand the unusual deep seismic pattern along the SJFZ, which was termed "deep creep" (Wdowinski, 2009). We relocated 97,562 events from 1981 to 2011 in Anza region by applying the Source-Specific Station Term (SSST) method (Lin et al., 2006) and used an accurate 1-D velocity model derived from 3-D model of Lin et al (2007) and used In order to separate the aftershock sequence from background seismicity, we characterized each of the three aftershock sequences using Omori's law. Preliminary results show that all three sequences had a similar geometry of deep elongated aftershock distribution. Most aftershocks occurred at depth of 10-17 km and extended over a 70 km long segments of the SJFZ, centered at the mainshock hypocenters. A comparative study of other M5~5.5 mainshocks and their aftershock sequences in southern California reveals very different geometrical pattern, suggesting that the three Anza M5~5.5 events are unique and can be indicative of "deep creep" deformation processes. Reference 1.Lin, G.and Shearer,P.M.,2006, The COMPLOC earthquake location package,Seism. Res. Lett.77, pp.440-444. 2.Lin, G. and Shearer, P.M., Hauksson, E., and Thurber C.H.,2007, A three-dimensional crustal seismic velocity model for southern California from a composite event method,J. Geophys.Res.112, B12306, doi: 10.1029/ 2007JB004977. 3.Wdowinski, S. ,2009, Deep creep as a cause for the excess seismicity along the San Jacinto fault, Nat. Geosci.,doi:10.1038/NGEO684.

  8. Distribution of similar earthquakes in aftershocks of inland earthquakes

    NASA Astrophysics Data System (ADS)

    Hayashi, M.; Hiramatsu, Y.; Aftershock Observations Of 2007 Noto Hanto, G.

    2010-12-01

    Frictional properties control the slip behavior on a fault surface such as seismic slip and aseismic slip. Asperity, as a seismic slip area, is characterized by a strong coupling in the interseismic period and large coseismic slip. On the other hand, steady slip or afterslip occurs in an aseismic slip area around the asperity. If an afterslip area includes small asperities, a repeating rupture of single asperity can generate similar earthquakes due to the stress accumulation caused by the afterslip. We here investigate a detail distribution of similar earthquakes in the aftershocks of the 2007 Noto Hanto earthquake (Mjma 6.9) and the 2000 Western Tottori earthquake (Mjma 7.3), inland large earthquakes in Japan. We use the data obtained by the group for the aftershock observations of the 2007 Noto Hanto Earthquake and by the group for the aftershock observations of the 2000 Western Tottori earthquake. First, we select pairs of aftershocks whose cross correlation coefficients in 10 s time window of band-pass filtered waveforms of 1~4 Hz are greater than 0.95 at more than 5 stations and divide those into groups by a link of the cross correlation coefficients. Second, we reexamine the arrival times of P and S waves and the maximum amplitude for earthquakes of each group and apply the double-difference method (Waldhouser and Ellsworth, 2000) to relocate them. As a result of the analysis, we find 24 groups of similar earthquakes in the aftershocks on the source fault of the 2007 Noto Hanto Earthquake and 86 groups of similar earthquakes in the aftershocks on the source fault of the 2000 Western Tottori Earthquake. Most of them are distributed around or outside the asperity of the main shock. Geodetic studies reported that postseismic deformation was detected for the both earthquakes (Sagiya et al., 2002; Hashimoto et al., 2008). The source area of similar earthquakes seems to correspond to the afterslip area. These features suggest that the similar earthquakes observed

  9. A mechanism of aftershock generation based on progressive material softening

    NASA Astrophysics Data System (ADS)

    Dyskin, Arcady; Pasternak, Elena; Bunger, Andrew; Kear, James

    2015-04-01

    Observations of aftershocks after major seismic events show that the rate of aftershock generation reduces according to the generalised Omori's law. This law reproduces itself at a variety of scales starting from the scales of the earthquakes to the laboratory scale. Furthermore, the Omori's law holds for different types of fracture event from shear fracture propagation over the faults to failure in compression to failure in tension. In particular our tests show that the Omori's law describes the aftershocks in crystalline rocks in a laboratory model of hydraulic fracture and after bending failure of beams. We propose a new universal mechanism of aftershock generation that reproduces the Omori's law. We firstly note that it is not the residual stress, as conventionally assumed, but the residual strain that is created by the preceding fracture process. The aftershocks are created by the residual stress that is related to the residual strain through elastic moduli. The accumulation of the aftershock-related microcracks reduces the elastic moduli and thus reduces the residual stress. This overall reduction of the residual stress with the number of aftershocks is the reason for the rate reduction in aftershock generation. Naturally this process might be accompanied by the reduction in wave velocities, albeit, as we show, the reduction is rather low. The effect the accumulated microcracks have on the moduli considerably depends on the microcrack distribution over both positions and orientations. We found that (a) if the microcracks have isotropic distribution over orientations the classical Omori's law is reproduced; (b) if the microcracks are shear and parallel to each other but randomly situated in space the generalised Omori's law is reproduced with the exponent p<1; (c) if the microcracks are represented by sliding zones distributed over a fault, the generalised Omori's law is reproduced with the exponent p>1. The main feature of the latter case is the existence of

  10. Information theory approach to the Landers aftershock sequence

    NASA Astrophysics Data System (ADS)

    Jiménez, Abigail

    2015-07-01

    The study of seismicity is becoming increasingly important with recent disasters such as the Gorkha event in Nepal in 2015. Our models mostly depend on the information given by a seismic catalog, such as rates of events and magnitudes. It has also been shown that seismicity presents long-range correlations. Here, we think about how they should be introduced in our models. We divide the region into cells and represent their activity as a time series. We then calculate how much information one cell has about the others in a future time. We find that the higher information content is in each cell with itself. By representing the region as a complex network, we can see that the information between distant cells passes thorough hubs that correspond to the main events. So we conclude that long-range interactions should be introduced as the interaction with the mainshocks, not with other cells except, perhaps, in the nearest neighbourhood.

  11. Phenomenology of some rare and forbidden. eta. -decays

    SciTech Connect

    Herczeg, P.

    1990-01-01

    We discuss the contribution from possible new physics to the decays {eta} {yields} {mu}{sup +}{mu}{sup {minus}}, {eta} {yields} e{sup +}e{sup {minus}}, {eta} {yields} {mu}e and {eta} {pi}{mu}e, and assess the sensitivities required for experimental studies of these decays to extend our knowledge about the new interactions. 61 refs.

  12. Eta Carinae and Its Ejecta, the Homunculus

    NASA Technical Reports Server (NTRS)

    Gull, Theodore R.

    2014-01-01

    Eta Carinae (Eta Car), its interacting winds and historical ejecta provide an unique astrophysical laboratory that permits addressing a multitude of questions ranging from stellar evolution, colliding winds, chemical enrichment, nebular excitation to the formation of molecules and dust. Every 5.54 years, Eta Car changes from high excitation to several-months-long low excitation caused by modulation of the massive interacting winds due to a very eccentric binary orbit. The surrounding Homunculus (Figure 1) and Little Homunculus, thrown out in the 1840s Great Eruption and the 1890s Lesser Eruption, respond to the changing flux, providing clues to many physical phenomena of great interest to astrophysicists.

  13. Charmonium decays to {gamma}{pi}{sup 0}, {gamma}{eta}, and {gamma}{eta}{sup '}

    SciTech Connect

    Pedlar, T. K.; Xavier, J.; Cronin-Hennessy, D.; Gao, K. Y.; Hietala, J.; Klein, T.; Poling, R.; Zweber, P.; Dobbs, S.; Metreveli, Z.; Seth, K. K.; Tan, B. J. Y.; Tomaradze, A.; Libby, J.; Martin, L.; Powell, A.; Thomas, C.; Wilkinson, G.; Mendez, H.; Ge, J. Y.

    2009-06-01

    Using data acquired with the CLEO-c detector at the CESR e{sup +}e{sup -} collider, we measure branching fractions for J/{psi}, {psi}(2S), and {psi}(3770) decays to {gamma}{pi}{sup 0}, {gamma}{eta}, and {gamma}{eta}{sup '}. Defining R{sub n}{identical_to}B[{psi}(nS){yields}{gamma}{eta}]/B[{psi}(nS){yields}{gamma}{eta}{sup '}], we obtain R{sub 1}=(21.1{+-}0.9)% and, unexpectedly, an order of magnitude smaller limit, R{sub 2}<1.8% at 90% C.L. We also use J/{psi}{yields}{gamma}{eta}{sup '} events to determine branching fractions of improved precision for the five most copious {eta}{sup '} decay modes.

  14. Statistical discrimination of induced and tectonic earthquake sequences in Central and Eastern US based on waveform detected catalogs

    NASA Astrophysics Data System (ADS)

    Meng, X.; Daniels, C.; Smith, E.; Peng, Z.; Chen, X.; Wagner, L. S.; Fischer, K. M.; Hawman, R. B.

    2015-12-01

    Since 2001, the number of M>3 earthquakes increased significantly in Central and Eastern United States (CEUS), likely due to waste-water injection, also known as "induced earthquakes" [Ellsworth, 2013]. Because induced earthquakes are driven by short-term external forcing and hence may behave like earthquake swarms, which are not well characterized by branching point-process models, such as the Epidemic Type Aftershock Sequence (ETAS) model [Ogata, 1988]. In this study we focus on the 02/15/2014 M4.1 South Carolina and the 06/16/2014 M4.3 Oklahoma earthquakes, which likely represent intraplate tectonic and induced events, respectively. For the South Carolina event, only one M3.0 aftershock is identified by the ANSS catalog, which may be caused by a lack of low-magnitude events in this catalog. We apply a recently developed matched filter technique to detect earthquakes from 02/08/2014 to 02/22/2014 around the epicentral region. 15 seismic stations (both permanent and temporary USArray networks) within 100 km of the mainshock are used for detection. The mainshock and aftershock are used as templates for the initial detection. Newly detected events are employed as new templates, and the same detection procedure repeats until no new event can be added. Overall we have identified more than 10 events, including one foreshock occurred ~11 min before the M4.1 mainshock. However, the numbers of aftershocks are still much less than predicted with the modified Bath's law. For the Oklahoma event, we use 1270 events from the ANSS catalog and 182 events from a relocated catalog as templates to scan through continuous recordings 3 days before to 7 days after the mainshock. 12 seismic stations within the vicinity of the mainshock are included in the study. After obtaining more complete catalogs for both sequences, we plan to compare the statistical parameters (e.g., b, a, K, and p values) between the two sequences, as well as their spatial-temporal migration pattern, which may

  15. Study of {eta}' Decays in the VES Experiment

    SciTech Connect

    Nikolaenko, V.; Gavrilov, Yu.; Gouz, Yu.; Dzheliadin, R.; Fenyuk, A.; Ivashin, A.; Kachaev, I.; Kabachenko, V.; Karyukhin, A.; Khokhlov, Yu.; Konopliannikov, A.; Konstantinov, V.; Matveev, V.; Ostankov, A.; Polyakov, B.; Ryabchikov, D.; Solodkov, A. A.; Solodkov, A. V.; Solovianov, O.; Starchenko, E.

    2005-10-26

    Measurements of Dalitz plot parameters for {eta}' {yields} {eta}{pi}+{pi}- decay are presented. The data sample of {approx}15000 events originates from charge-exchange reaction {pi}-p {yields} {eta}'N* at beam momentum of 28 GeV/c. Comparison with results from diffractive-like reaction, {pi}-A {yields} {eta}'{pi}-A* and with theoretical expectations is given. Also a limit of Br({eta}' {yields} ({pi}+{pi}-{pi}0)) is estimated.

  16. Observation of the eta/sub c/(2980) produced in the radiative decay of the psi'(3684)

    SciTech Connect

    Himel, T.M.; Trilling, G.H.; Abrams, G.S.; Alam, M.S.; Blocker, C.A.; Blondel, A.P.; Boyarski, A.M.; Breidenbach, M.; Burke, D.L.; Carithers, W.C.; Chinowsky, W.; Coles, M.W.; Cooper, S.; Dieterle, W.E.; Dillon, J.B.; Dorenbosch, J.; Dorfan, J.M.; Eaton, M.W.; Feldman, G.J.; Franklin, M.E.B.; Gidal, G.; Goldhaber, G.; Hanson, G.; Hayes, K.G.; Hitlin, D.G.; Hollebeek, R.J.; Innes, W.R.; Jaros, J.A.; Jenni, P.; Johnson, A.D.; Kadyk, J.A.; Lankford, A.J.; Larsen, R.R.; Levi, M.E.; Lueth, V.; Millikan, R.E.; Nelson, M.E.; Pang, C.Y.; Patrick, J.F.; Perl, M.L.; Richter, B.; Roussarie, A.; Scharre, D.L.; Schindler, R.H.; Schwitters, R.F.; Siegrist, J.L.; Strait, J.; Taureg, H.; Tonutti, M.; Vella, E.N.; Vidal, R.A.; Videau, I.; Weiss, J.M.; Zaccone, H.

    1980-10-06

    In a study of psi'(3684) radiative decays with the Mark II detector at SPEAR, the decay sequence psi'..--> gamma..eta/sub c/(2980) is observed, with the eta/sub c/(2980) decaying into several completely reconstructed hadronic modes. A mass M=2980 +- 8 MeV/c/sup 2/ and a width GAMMA<40 MeV/c/sup 2/ (90% confidence level) are obtained, and estimates of some of the decay branching ratios are presented.

  17. Modeling of Kashmir Aftershock Decay Based on Static Coulomb Stress Changes and Laboratory-Derived Rate-and-State Dependent Friction Law

    NASA Astrophysics Data System (ADS)

    Javed, F.; Hainzl, S.; Aoudia, A.; Qaisar, M.

    2016-05-01

    We model the spatial and temporal evolution of October 8, 2005 Kashmir earthquake's aftershock activity using the rate-and-state dependent friction model incorporating uncertainties in computed coseismic stress perturbations. We estimated the best possible value for frictional resistance " Aσ n", background seismicity rate " r" and coefficient of stress variation "CV" using maximum log-likelihood method. For the whole Kashmir earthquake sequence, we measure a frictional resistance Aσ n ~ 0.0185 MPa, r ~ 20 M3.7+ events/year and CV = 0.94 ± 0.01. The spatial and temporal forecasted seismicity rate of modeled aftershocks fits well with the spatial and temporal distribution of observed aftershocks that occurred in the regions with positive static stress changes as well as in the apparent stress shadow region. To quantify the effect of secondary aftershock triggering, we have re-run the estimations for 100 stochastically declustered catalogs showing that the effect of aftershock-induced secondary stress changes is obviously minor compared to the overall uncertainties, and that the stress variability related to uncertain slip model inversions and receiver mechanisms remains the major factor to provide a reasonable data fit.

  18. Diversity of the 2014 Iquique's foreshocks and aftershocks: clues about the complex rupture process of a Mw 8.1 earthquake

    NASA Astrophysics Data System (ADS)

    León-Ríos, Sergio; Ruiz, Sergio; Maksymowicz, Andrei; Leyton, Felipe; Fuenzalida, Amaya; Madariaga, Raúl

    2016-03-01

    We study the foreshocks and aftershocks of the 1 April 2014 Iquique earthquake of Mw 8.1. Most of these events were recorded by a large digital seismic network that included the Northern Chile permanent network and up to 26 temporary broadband digital stations. We relocated and computed moment tensors for 151 events of magnitude Mw ≥ 4.5. Most of the foreshocks and aftershocks of the Iquique earthquake are distributed to the southwest of the rupture zone. These events are located in a band of about 50 km from the trench, an area where few earthquakes occur elsewhere in Chile. Another important group of aftershocks is located above the plate interface, similar to those observed during the foreshock sequence. The depths of these events were constrained by regional moment tensor (RMT) solutions obtained using the records of the dense broad band network. The majority of the foreshocks and aftershocks were associated to the interplate contact, with dip and strike angles in good agreement with the characteristics of horst and graben structures (>2000 m offset) typical of the oceanic Nazca Plate at the trench and in the outer rise region. We propose that the spatial distribution of foreshocks and aftershocks, and its seismological characteristics were strongly controlled by the rheological and tectonics conditions of the extreme erosive margin of Northern Chile.

  19. Measurement of charmless B decays to {eta}K* and {eta}{rho}

    SciTech Connect

    Wang, C. H.; Schuemann, J.; Abe, K.; Adachi, I.; Gershon, T.; Haba, J.; Hazumi, M.; Itoh, R.; Iwasaki, Y.; Katayama, N.; Kichimi, H.; Nakao, M.; Nishida, S.; Ozaki, H.; Sakai, Y.; Suzuki, S. Y.; Tamai, K.; Tanaka, M.; Tsuboyama, T.; Tsukamoto, T.

    2007-05-01

    We report measurements of branching fractions and CP asymmetries for B{yields}{eta}K* and B{yields}{eta}{rho} decays. These results are obtained from a 414 fb{sup -1} data sample collected at the {upsilon}(4S) resonance with the Belle detector at the KEKB asymmetric-energy e{sup +}e{sup -} collider. We measure the following branching fractions: B(B{sup 0}{yields}{eta}K*{sup 0})=(15.2{+-}1.2{+-}1.0)x10{sup -6} and B(B{sup +}{yields}{eta}K*{sup +})=(19.3{sub -1.9}{sup +2.0}{+-}1.5)x10{sup -6}, where the first error is statistical and the second systematic. We also find a 2.7{sigma} excess in the B{sup +}{yields}{eta}{rho}{sup +} mode and measure B(B{sup +}{yields}{eta}{rho}{sup +})=(4.1{sub -1.3}{sup +1.4}{+-}0.4)x10{sup -6}<6.5x10{sup -6} at 90% confidence level. For B{sup 0}{yields}{eta}{rho}{sup 0} decays, we determine the upper limit B(B{sup 0}{yields}{eta}{rho}{sup 0})<1.9x10{sup -6} at 90% confidence level. The partial rate asymmetries are A{sub CP}({eta}K*{sup 0})=0.17{+-}0.08{+-}0.01, A{sub CP}({eta}K*{sup +})=0.03{+-}0.10{+-}0.01, and A{sub CP}({eta}{rho}{sup +})=-0.04{sub -0.32}{sup +0.34}{+-}0.01.

  20. Eta Carinae: An Astrophysical Laboratory

    NASA Technical Reports Server (NTRS)

    Gull, T.

    2008-01-01

    In the 1840s, Eta Carinae, a massive binary near the end of its hydrogen burning cycle, ejected at least ten solar masses of material rich in nitrogen at the expense of carbon and oxygen. The resultant chemistry has led to a most peculiar mix of metals, molecules and dust. We identify thousands of nebular absorption lines of ions including Fe, Ni, V, Sr, Sc and molecules including H2, CH, OH, but no CO. Today we see a wind-enshrouded massive binary in the center of an expanding neutral hourglass and skirt. A similar ionized internal structure is associated with a lesser ejection of the 1890s. Both systems respond to the 5.54-year modulation of X-ray and ultraviolet radiation as the less massive, hotter companion plunges through the extended wind of the more massive, cooler primary. Observations and models are being brought together to understand the properties of the wind-enshrouded central binary. In turn we are learning much atomic spectroscopy, what molecules form in oxygen-and carbon-deprived environments and potentially about a dust that is quite different from the interstellar dust. As the next periastron occurs in January 2009, a number of observing teams are preparing to test these models with new observations.

  1. Aftershocks Following the 9 April 2013 Bushehr Earthquake, Iran

    PubMed Central

    Ardalan, Ali; Hajiuni, Alireza; Zare, Mehdi

    2013-01-01

    On 9 April 2013 at 11:52 UTC (16:22 local time), a Mw 6.2 earthquake occurred at the depth of 20 Km in Dashti district in south-west Iran’s Bushehr province. The macroseismic epicenter was located nearby the city of Shonbeh. During one month after the earthquake, a total of 282 aftershocks hit the epicentral region, mostly at the east and north sides. They ranged from 2.5 to 5.7 on the Richter scale. Seventy aftershocks (24.9%) were M4.0-4.9 and eight (2.8%) were M5.0-5.7. Aftershocks are potentially able to do additional damage. In Bushehr earthquake, a M5.4 aftershock on 10 April in Chahgah village caused at least four injuries and destruction of several buildings that had been already damaged by the main shock. Knowledge about the aftershock induced damages provides opportunities for timely risk communication with the affected people and for long term community education. This will hopefully increase the community awareness and minimize the risk of further loss of lives. PMID:24042232

  2. Aftershocks following the 9 april 2013 bushehr earthquake, iran.

    PubMed

    Ardalan, Ali; Hajiuni, Alireza; Zare, Mehdi

    2013-08-28

    On 9 April 2013 at 11:52 UTC (16:22 local time), a Mw 6.2 earthquake occurred at the depth of 20 Km in Dashti district in south-west Iran's Bushehr province. The macroseismic epicenter was located nearby the city of Shonbeh. During one month after the earthquake, a total of 282 aftershocks hit the epicentral region, mostly at the east and north sides. They ranged from 2.5 to 5.7 on the Richter scale. Seventy aftershocks (24.9%) were M4.0-4.9 and eight (2.8%) were M5.0-5.7. Aftershocks are potentially able to do additional damage. In Bushehr earthquake, a M5.4 aftershock on 10 April in Chahgah village caused at least four injuries and destruction of several buildings that had been already damaged by the main shock. Knowledge about the aftershock induced damages provides opportunities for timely risk communication with the affected people and for long term community education. This will hopefully increase the community awareness and minimize the risk of further loss of lives.

  3. Chiral corrections to the anomalous 2. gamma. decays of. pi. sup 0 ,. eta. and. eta. prime

    SciTech Connect

    Issler, D.

    1990-11-01

    To any order in chiral perturbation theory, the anomalous Wess-Zumino term is shown to generate only chirally invariant counterterms. Explicit examples of 0(p{sub 6}) terms generated by one-loop graphs are given, some of which are relevant to the two-photon decays of {pi}{sup o}, {eta} and {eta}{prime}.

  4. Eta Squared and Partial Eta Squared as Measures of Effect Size in Educational Research

    ERIC Educational Resources Information Center

    Richardson, John T. E.

    2011-01-01

    Eta squared measures the proportion of the total variance in a dependent variable that is associated with the membership of different groups defined by an independent variable. Partial eta squared is a similar measure in which the effects of other independent variables and interactions are partialled out. The development of these measures is…

  5. Effect of {eta}-{eta}{sup '} mixing on D{yields}PV decays

    SciTech Connect

    Bhattacharya, Bhubanjyoti; Rosner, Jonathan L.

    2010-08-01

    Charmed meson decays to a light pseudoscalar (P) and light vector (V) meson are analyzed taking account of {eta}-{eta}{sup '} mixing. A frequently-used octet-singlet mixing angle of 19.5 degree sign is compared with a value of 11.7 degree sign favored by a recent analysis of D{yields}PP decays.

  6. Aftershock activity of the 2015 Gorkha, Nepal, earthquake determined using the Kathmandu strong motion seismographic array

    NASA Astrophysics Data System (ADS)

    Ichiyanagi, Masayoshi; Takai, Nobuo; Shigefuji, Michiko; Bijukchhen, Subeg; Sasatani, Tsutomu; Rajaure, Sudhir; Dhital, Megh Raj; Takahashi, Hiroaki

    2016-02-01

    The characteristics of aftershock activity of the 2015 Gorkha, Nepal, earthquake (Mw 7.8) were evaluated. The mainshock and aftershocks were recorded continuously by the international Kathmandu strong motion seismographic array operated by Hokkaido University and Tribhuvan University. Full waveform data without saturation for all events enabled us to clarify aftershock locations and decay characteristics. The aftershock distribution was determined using the estimated local velocity structure. The hypocenter distribution in the Kathmandu metropolitan region was well determined and indicated earthquakes located shallower than 12 km depth, suggesting that aftershocks occurred at depths shallower than the Himalayan main thrust fault. Although numerical investigation suggested less resolution for the depth component, the regional aftershock epicentral distribution of the entire focal region clearly indicated earthquakes concentrated in the eastern margin of the major slip region of the mainshock. The calculated modified Omori law's p value of 1.35 suggests rapid aftershock decay and a possible high temperature structure in the aftershock region.

  7. Stress Triggering of Conjugate Normal Faulting: Late Aftershocks of the 1983 M 7.3 Borah Peak, Idaho Earthquake

    SciTech Connect

    Suzette J. Payne; James Zollweg; David Rodgers

    2004-06-01

    The 1984 Devil Canyon sequence was a late aftershock sequence of the 28 October 1983 Ms 7.3 Borah Peak, Idaho, earthquake. The sequence began on 22 August 1984 with the ML 5.8 Devil Canyon earthquake, which nucleated at a depth of 12.8 ± 0.7 km between the surface traces of two normal faults, the Challis segment of the Lost River fault and the Lone Pine fault. Two hundred thirty-seven aftershocks were recorded by a temporary array during a 3-week period. Their focal mechanisms and hypocenter distribution define a cross-sectional "V" pattern whose base corresponds to the ML 5.8 event, whose tips correspond to the exposed fault traces, and whose sides define two planar fault zones oriented N25°W, 75°SW (Challis fault segment) and N39°W, 58°NE (Lone Pine fault). This pattern describes a graben bounded by conjugate normal faults. Temporal aspects of the Devil Canyon sequence provide strong evidence that slip on conjugate normal faults occurs sequentially. Aftershocks occurred primarily along the Challis segment until the occurrence of the 8 September 1984 ML 5.0 earthquake along the Lone Pine fault, after which aftershocks primarily occurred along this fault. These observations are consistent with worldwide seismologic and geologic observations and with physical and numerical models of conjugate normal faulting. Aftershocks of the Devil Canyon sequence occurred immediately northwest of the ML 5.8 Devils Canyon earthquake, which itself was immediately northwest of the Thousand Springs segment of the Lost River fault (the fault that slipped in association with the Ms 7.3 Borah Peak earthquake). Coulomb failure stress analysis indicates that stress increases resulting from both the Borah Peak mainshock and Devil Canyon ML 5.8 earthquake were sufficient to induce failure on the Lone Pine fault. These space–time patterns suggest that conjugate normal faults may transfer stress or accommodate stress changes at the terminations of major normal faults in the Basin and

  8. Eta Carinae: Orientation of The Orbital Plane

    NASA Technical Reports Server (NTRS)

    Gull, T. R.; Nielsen, K. E.; Ivarsson, S.; Corcoran, M. F.; Verner, E.; Hillier, J. D.

    2006-01-01

    Evidence continues to build that Eta Carinae is a massive binary system with a hidden hot companion in a highly elliptical orbit. We present imaging and spectroscopic evidence that provide clues to the orientation of the orbital plane. The circumstellar ejecta, known as the Homunculus and Little Homunculus, are hourglass-shaped structures, one encapsulated within the other, tilted at about 45 degrees from the sky plane. A disk region lies between the bipolar lobes. Based upon their velocities and proper motions, Weigelt blobs B, C and D, very bright emission clumps 0.1 to 0.3" Northwest from Eta Carinae, lie in the disk. UV flux from the hot companion, Eta Car B, photoexcites the Weigelt blobs. Other clumps form a complete chain around the star, but are not significantly photoexcited. The strontium filament, a 'neutral' emission structure, lies in the same general direction as the Weigelt blobs and exhibits peculiar properties indicative that much mid-UV, but no hydrogen-ionizing radiation impinges on this structure. It is shielded by singly-ionized iron. P Cygni absorptions in Fe I I lines, seen directly in line of sight from Eta Carinae, are absent in the stellar light scattered by the Weigelt blobs. Rather than a strong absorption extending to -600 km/s, a low velocity absorption feature extends from -40 to -150 km/s. No absorbing Fe II exists between Eta Carinae and Weigelt D, but the outer reaches of the wind are intercepted in line of sight from Weigelt D to the observer. This indicates that the UV radiation is constrained by the dominating wind of Eta Car A to a small cavity carved out by the weaker wind of Eta Car B. Since the high excitation nebular lines are seen in the Weigelt blobs at most phases, the cavity, and hence the major axis of the highly elliptical orbit, must lie in the general direction of the Weigelt blobs. The evidence is compelling that the orbital major axis of Eta Carinae is projected at -45 degrees position angle on the sky. Moreover

  9. Source Characteristics of Aftershocks of the India Republic Day Earthquake

    NASA Astrophysics Data System (ADS)

    Horton, S.; Bodin, P.; Johnston, A.; Withers, M.; Chiu, C.; Raphael, A.; Rabak, I.; Maio, Q.; Smalley, R.; Chiu, J.; Langston, C.

    2001-05-01

    We present a preliminary analysis of aftershocks of the Mw=7.7 Republic Day (26 January) 2001 earthquake in Gujarat, India, recorded on a network of portable digital event recorders (the MAEC/ISTAR network). During the 18 day deployment, this network recorded ground motion from nearly 2000 earthquakes; almost exclusively M<5 events within about 100 km of all stations. In this talk we will discuss the results of an analysis of approximately 400 earthquakes that were recorded at 6 or more sites. Because of its history of infrequent moderate-to-large earthquakes and its setting within a continental plate interior (albeit rather close to a rather diffuse continental boundary), studies of the Kachchh region may provide important insights for other high-consequence-but-low-occurrence-rate regions, such as the central US. A series of unfortunate circumstances has cast an obscuring veil of ignorance over the mainshock: we know of no strong-motion recordings of the mainshock, regional broad-band and seismic network data is notoriously difficult to obtain for scientific evaluation, evidence of surface rupture or deformation is fragmentary and complex or obscured by massive liquefaction, pre-existing geodetic networks are non-existent, and satellite-based radar interferometry studies have been hobbled by poor pre-earthquake images. Aftershock occurrence may provide critical evidence to determine which fault ruptured in January, 2001, and aftershock studies may provide important observational constraints on source processes and wave propagation in the region. We focus on trying to discern the mainshock fault plane, which appears to dip to the south, and whether the aftershocks are unusually deep (down to 35 km, which might help to explain the lack of obvious surface rupture). In addition to determining first-motion focal mechanisms we will examine whether stress drops of the aftershocks are, on the whole, high. We compare the seismic sources and regional propagation of

  10. Simulating Aftershocks for an On Site Inspection (OSI) Exercise

    SciTech Connect

    Sweeney, J. J.; Ford, S. R.

    2015-10-05

    The experience of IFE14 emphasizes the need for a better way to simulate aftershocks during an OSI exercise. The obvious approach is to develop a digital model of aftershocks that can be used either for a real field exercise or for a computer simulation that can be done in an office, for training for example. However, this approach involves consideration of several aspects, such as how and when to introduce waveforms in a way that maximizes the realism of the data and that will be convincing to a savvy, experienced seismic analyst. The purpose of this report is to outline a plan for how this approach can be implemented.

  11. Foreshocks and aftershocks of Pisagua 2014 earthquake: time and space evolution of megathrust event.

    NASA Astrophysics Data System (ADS)

    Fuenzalida Velasco, Amaya; Rietbrock, Andreas; Wollam, Jack; Thomas, Reece; de Lima Neto, Oscar; Tavera, Hernando; Garth, Thomas; Ruiz, Sergio

    2016-04-01

    The 2014 Pisagua earthquake of magnitude 8.2 is the first case in Chile where a foreshock sequence was clearly recorded by a local network, as well all the complete sequence including the mainshock and its aftershocks. The seismicity of the last year before the mainshock include numerous clusters close to the epicentral zone (Ruiz et al; 2014) but it was on 16th March that this activity became stronger with the Mw 6.7 precursory event taking place in front of Iquique coast at 12 km depth. The Pisagua earthquake arrived on 1st April 2015 breaking almost 120 km N-S and two days after a 7.6 aftershock occurred in the south of the rupture, enlarging the zone affected by this sequence. In this work, we analyse the foreshocks and aftershock sequence of Pisagua earthquake, from the spatial and time evolution for a total of 15.764 events that were recorded from the 1st March to 31th May 2015. This event catalogue was obtained from the automatic analyse of seismic raw data of more than 50 stations installed in the north of Chile and the south of Peru. We used the STA/LTA algorithm for the detection of P and S arrival times on the vertical components and then a method of back propagation in a 1D velocity model for the event association and preliminary location of its hypocenters following the algorithm outlined by Rietbrock et al. (2012). These results were then improved by locating with NonLinLoc software using a regional velocity model. We selected the larger events to analyse its moment tensor solution by a full waveform inversion using ISOLA software. In order to understand the process of nucleation and propagation of the Pisagua earthquake, we also analysed the evolution in time of the seismicity of the three months of data. The zone where the precursory events took place was strongly activated two weeks before the mainshock and remained very active until the end of the analysed period with an important quantity of the seismicity located in the upper plate and having

  12. Endothelin ETA receptor antagonism in cardiovascular disease.

    PubMed

    Nasser, Suzanne A; El-Mas, Mahmoud M

    2014-08-15

    Since the discovery of the endothelin system in 1988, it has been implicated in numerous physiological and pathological phenomena. In the cardiovascular system, endothelin-1 (ET-1) acts through intracellular pathways of two endothelin receptors (ETA and ETB) located mainly on smooth muscle and endothelial cells to regulate vascular tone and provoke mitogenic and proinflammatory reactions. The endothelin ETA receptor is believed to play a pivotal role in the pathogenesis of several cardiovascular disease including systemic hypertension, pulmonary arterial hypertension (PAH), dilated cardiomyopathy, and diabetic microvascular dysfunction. Growing evidence from recent experimental and clinical studies indicates that the blockade of endothelin receptors, particularly the ETA subtype, grasps promise in the treatment of major cardiovascular pathologies. The simultaneous blockade of endothelin ETB receptors might not be advantageous, leading possibly to vasoconstriction and salt and water retentions. This review summarizes the role of ET-1 in cardiovascular modulation and the therapeutic potential of endothelin receptor antagonism.

  13. The electroproduction of etas and kaons

    SciTech Connect

    O.K. Baker

    2001-12-01

    Experimental results for the electromagnetic production of eta and K mesons are compared with QCD-inspired models. The eta mesons from the decay of S_11 resonance were used to study the momentum transfer dependence of the relevant helicity amplitude and cross section in the reaction ^1H(e,e'p)eta. The ^1H(e,e'K+)Lambda reaction was studied as a function of squared four-momentum transfer, Q^2, and of the virtual photon polarization parameter, epsilon. Both of these experiments were performed at Jefferson Lab during the early years of operation. The new precision data serve to constrain model calculations and provide new insights into the physical processes.

  14. Preparation phase and consequences of a large earthquake: insights from foreshocks and aftershocks of the 2014 Mw 8.1 Iquique earthquake, Chile

    NASA Astrophysics Data System (ADS)

    Cesca, Simone; Grigoli, Francesco; Heimann, Sebastian; Dahm, Torsten

    2015-04-01

    The April 1, 2014, Mw 8.1 Iquique earthquake in Northern Chile, was preceded by an anomalous, extensive preparation phase. The precursor seismicity at the ruptured slab segment was observed sporadically several months before the main shock, with a significant increment in seismicity rates and observed magnitudes in the last three weeks before the main shock. The large dataset of regional recordings helped us to investigate the role of such precursor activity, comparing foreshock and aftershock seismicity to test models of rupture preparation and models of strain and stress rotation during an earthquake. We used full waveforms techniques to locate events, map the seismicity rate, derive source parameters, and assess spatiotemporal stress changes. Results indicate that the spatial distributions of foreshocks delineated the shallower part of the rupture areas of the main shock and its largest aftershock, and is well matching the spatial extension of the aftershocks. During the foreshock sequence, seismicity spatially is mainly localized in two clusters, separated by a region of high locking. The ruptures of mainshock and largest aftershock nucleate within these clusters and propagate to the locked region; the aftershocks are again localized in correspondence to the original spatial clusters, and the central region is locked again. More than 300 moment tensor inversions were performed, down to Mw 4.0, most of them corresponding to almost pure double couple thrust mechanisms, with a geometry consistent with the slab orientation. No significant differences are observed among thrust mechanisms in different areas, nor among thrust foreshocks and aftershocks. However, a new family of normal fault mechanisms appears after the main shock, likely affecting the shallow wedge structure in consequence of the increased extensional stress in this region. We infer a stress rotation after the main shock, as proposed for recent larger thrust earthquakes, which suggests that the April

  15. Observation of B^+\\to\\eta\\rho^+ and Search for B^0 Decays to\\eta^\\prime\\eta, \\eta\\pi^0, \\eta^\\prime\\pi^0, and \\omega\\pi^0

    SciTech Connect

    Aubert, Bernard; Bona, Marcella; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Lopez, L.; Palano, Antimo; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Abrams, G.S.; Battaglia, Marco; Brown, D.N.; Button-Shafer, Janice; Cahn, Robert N.; /LBL, Berkeley /Birmingham U. /Ruhr U., Bochum /Bristol U. /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UCLA /UC, Riverside /UC, San Diego /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /INFN, Ferrara /Frascati /Genoa U. /INFN, Genoa /Harvard U. /Heidelberg U. /Imperial Coll., London /Iowa U. /Iowa State U. /Johns Hopkins U. /Karlsruhe U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT /McGill U. /INFN, Milan /Mississippi U. /Montreal U. /Mt. Holyoke Coll. /INFN, Naples /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /INFN, Padua /Paris U., VI-VII /Pennsylvania U. /INFN, Perugia /INFN, Pisa /Princeton U. /INFN, Rome /Rostock U. /Rutherford /DSM, DAPNIA, Saclay /South Carolina U. /SLAC /Stanford U., Phys. Dept. /SUNY, Albany /Tennessee U. /Texas U. /Texas U., Dallas /INFN, Turin /INFN, Trieste /Valencia U., IFIC /Victoria U. /Warwick U. /Wisconsin U., Madison

    2008-04-22

    The authors present measurements of branching fractions for five B-meson decays to two-body charmless final states. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 459 million B{bar B} pairs. The results for branching fractions are, in units of 10{sup -6} (upper limits at 90% C.L.): {Beta}(B{sup +} {yields} {eta}{rho}{sup +}) = 9.9 {+-} 1.2 {+-} 0.8, {Beta}(B{sup 0} {yields} {eta}{prime}{eta}) = 0.5 {+-} 0.4 {+-} 0.1 (< 1.2), {Beta}(B{sup 0} {yields} {eta}{pi}{sup 0}) = 0.9 {+-} 0.4 {+-} 0.1 (< 1.5), {Beta}(B{sup 0} {yields} {eta}{prime}{pi}{sup 0}) = 0.9 {+-} 0.4 {+-} 0.1 (< 1.5), and {Beta}(B{sup 0}{sup 0} {yields} {omega}{pi}{sup 0}) = {eta}{rho}{sup +} mode, they measure the charge asymmetry {Alpha}{sub ch} (B{sup +} {yields} {eta}{rho}{sup +}) = 0.13 {+-} 0.11 {+-} 0.02.

  16. 31 CFR 208.5 - Availability of the ETA SM.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 2 2010-07-01 2010-07-01 false Availability of the ETA SM. 208.5... DISBURSEMENTS § 208.5 Availability of the ETA SM. An individual who receives a Federal benefit, wage, salary, or retirement payment shall be eligible to open an ETA SM at any Federally-insured financial institution...

  17. 31 CFR 208.5 - Availability of the ETA SM.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 31 Money and Finance:Treasury 2 2013-07-01 2013-07-01 false Availability of the ETA SM. 208.5... DISBURSEMENTS § 208.5 Availability of the ETA SM. An individual who receives a Federal benefit, wage, salary, or retirement payment shall be eligible to open an ETA SM at any Federally-insured financial institution...

  18. 31 CFR 208.5 - Availability of the ETA SM.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 31 Money and Finance:Treasury 2 2012-07-01 2012-07-01 false Availability of the ETA SM. 208.5... DISBURSEMENTS § 208.5 Availability of the ETA SM. An individual who receives a Federal benefit, wage, salary, or retirement payment shall be eligible to open an ETA SM at any Federally-insured financial institution...

  19. 31 CFR 208.5 - Availability of the ETA SM.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 31 Money and Finance: Treasury 2 2014-07-01 2014-07-01 false Availability of the ETA SM. 208.5... DISBURSEMENTS § 208.5 Availability of the ETA SM. An individual who receives a Federal benefit, wage, salary, or retirement payment shall be eligible to open an ETA SM at any Federally-insured financial institution...

  20. Study of B Meson Decays with Excited eta and eta-prime Mesons

    SciTech Connect

    Aubert, B.; Bona, M.; Boutigny, D.; Karyotakis, Y.; Lees, J.P.; Poireau, V.; Prudent, X.; Tisserand, V.; Zghiche, A.; Garra Tico, J.; Grauges, E.; Lopez, L.; Palano, A.; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Abrams, G.S.; Battaglia, M.; Brown, D.N.; Button-Shafer, J.; /Energy Sci. Network /Birmingham U. /Ruhr U., Bochum /Bristol U. /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UCLA /UC, Riverside /UC, San Diego /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /Ferrara U. /Frascati /Genoa U. /Harvard U. /Heidelberg U. /Imperial Coll., London /Iowa U. /Iowa State U. /Johns Hopkins U. /Karlsruhe U. /Orsay, LAL /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Louisville U. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT, LNS /McGill U. /Milan U. /INFN, Milan /Mississippi U. /Montreal U. /Mt. Holyoke Coll. /Naples U. /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /Padua U. /Paris U., VI-VII /Pennsylvania U. /Perugia U. /Pisa U. /Prairie View A-M /Princeton U. /INFN, Rome /Rostock U. /Rutherford /DSM, DAPNIA, Saclay /South Carolina U. /SLAC /Stanford U., Phys. Dept. /SUNY, Albany /Tennessee U. /Texas U. /Texas U., Dallas /Turin U. /INFN, Turin /Trieste U. /Valencia U., IFIC /Victoria U. /Warwick U. /Wisconsin U., Madison /Yale U.

    2008-04-18

    Using 383 million B{bar B} pairs from the BABAR data sample, they report results for branching fractions of six charged B-meson decay modes, where a charged kaon recoils against a charmless resonance decaying to K{bar K}* or {eta}{pi}{pi} final states with mass in the range (1.2-1.8) GeV/c{sup 2}. They observe a significant enhancement at the low K{bar K}* invariant mass which is interpreted as B{sup +} {yields} {eta}(1475)K{sup +}, find evidence for the decay B{sup +} {yields} {eta}(1295)K{sup +}, and place upper limits on the decays B{sup +} {yields} {eta}(1405)K{sup +}, B{sup +} {yields} f{sub 1}(1285)K{sup +}, B{sup +} {yields} f{sub 1}(1420)K{sup +}, and B{sup +} {yields} {phi}(1680)K{sup +}.

  1. A SEA CHANGE IN ETA CARINAE

    SciTech Connect

    Mehner, Andrea; Davidson, Kris; Humphreys, Roberta M.; Martin, John C.; Ishibashi, Kazunori; Ferland, Gary J.; Walborn, Nolan R.

    2010-07-01

    Major stellar-wind emission features in the spectrum of {eta} Car have recently decreased by factors of order 2 relative to the continuum. This is unprecedented in the modern observational record. The simplest, but unproven, explanation is a rapid decrease in the wind density.

  2. THE ENVIRONMENTAL TECHNOLOGIES ACCEPTANCE (ETA) PROGRAM

    SciTech Connect

    Christina B. Behr-Andres

    2001-10-01

    The objective of the Environmental Technologies Acceptance (ETA) Program at the Energy & Environmental Research Center (EERC) is to advance the development, commercial acceptance, and timely deployment of selected private sector technologies for the cleanup of sites in the nuclear defense complex as well as the greater market. As a result of contract changes approved by National Energy Technology Laboratory (NETL) representatives to incorporate activities previously conducted under another NETL agreement, there are now an additional task and an expansion of activities within the stated scope of work of the ETA program. As shown in Table 1, this cooperative agreement, funded by NETL (No. DE-FC26-00NT40840), consists of four tasks: Technology Selection, Technology Development, Technology Verification, and System Engineering. As currently conceived, ETA will address the needs of as many technologies as appropriate under its current 3-year term. There are currently four technical subtasks: Long-Term Stewardship Initiative at the Mound Plant Site; Photocatalysis of Mercury-Contaminated Water; Subcritical Water Treatment of PCB and Metal-Contaminated Paint Waste; and Vegetative Covers for Low-Level Waste Repositories. This report covers activities during the second six months of the three-year ETA program.

  3. Exponential decline of aftershocks of the M7.9 1868 great Kau earthquake, Hawaii, through the 20th century

    USGS Publications Warehouse

    Klein, F.W.; Wright, Tim

    2008-01-01

    The remarkable catalog of Hawaiian earthquakes going back to the 1820s is based on missionary diaries, newspaper accounts, and instrumental records and spans the great M7.9 Kau earthquake of April 1868 and its aftershock sequence. The earthquake record since 1868 defines a smooth curve complete to M5.2 of the declining rate into the 21st century, after five short volcanic swarms are removed. A single aftershock curve fits the earthquake record, even with numerous M6 and 7 main shocks and eruptions. The timing of some moderate earthquakes may be controlled by magmatic stresses, but their overall long-term rate reflects one of aftershocks of the Kau earthquake. The 1868 earthquake is, therefore, the largest and most controlling stress event in the 19th and 20th centuries. We fit both the modified Omori (power law) and stretched exponential (SE) functions to the earthquakes. We found that the modified Omori law is a good fit to the M ??? 5.2 earthquake rate for the first 10 years or so and the more rapidly declining SE function fits better thereafter, as supported by three statistical tests. The switch to exponential decay suggests that a possible change in aftershock physics may occur from rate and state fault friction, with no change in the stress rate, to viscoelastic stress relaxation. The 61-year exponential decay constant is at the upper end of the range of geodetic relaxation times seen after other global earthquakes. Modeling deformation in Hawaii is beyond the scope of this paper, but a simple interpretation of the decay suggests an effective viscosity of 1019 to 1020 Pa s pertains in the volcanic spreading of Hawaii's flanks. The rapid decline in earthquake rate poses questions for seismic hazard estimates in an area that is cited as one of the most hazardous in the United States.

  4. A preliminary analysis of {eta}'{yields}{eta}{pi}{pi} in chiral theories

    SciTech Connect

    Escribano, R.

    2010-08-05

    Preliminary results for the Dalitz plot distribution of {eta}'{yields}{eta}{pi}{pi} decays in the frameworks of Large-N{sub c} Chiral Perturbation Theory and Resonance Chiral Theory are given. We hope our results to be of some relevance for the present and forthcoming analysis of these decays at GAMS, CLEO, VES, KLOE-2, Crystal Ball, Crystal Barrel, WASA, and BES-III.

  5. Constraints on recent earthquake source parameters, fault geometry and aftershock characteristics in Oklahoma

    NASA Astrophysics Data System (ADS)

    McNamara, D. E.; Benz, H.; Herrmann, R. B.; Bergman, E. A.; McMahon, N. D.; Aster, R. C.

    2014-12-01

    In late 2009, the seismicity of Oklahoma increased dramatically. The largest of these earthquakes was a series of three damaging events (Mw 4.8, 5.6, 4.8) that occurred over a span of four days in November 2011 near the town of Prague in central Oklahoma. Studies suggest that these earthquakes were induced by reactivation of the Wilzetta fault due to the disposal of waste water from hydraulic fracturing ("fracking") and other oil and gas activities. The Wilzetta fault is a northeast trending vertical strike-slip fault that is a well known structural trap for oil and gas. Since the November 2011 Prague sequence, thousands of small to moderate (M2-M4) earthquakes have occurred throughout central Oklahoma. The most active regions are located near the towns of Stillwater and Medford in north-central Oklahoma, and Guthrie, Langston and Jones near Oklahoma City. The USGS, in collaboration with the Oklahoma Geological Survey and the University of Oklahoma, has responded by deploying numerous temporary seismic stations in the region in order to record the vigorous aftershock sequences. In this study we use data from the temporary seismic stations to re-locate all Oklahoma earthquakes in the USGS National Earthquake Information Center catalog using a multiple-event approach known as hypo-centroidal decomposition that locates earthquakes with decreased uncertainty relative to one another. Modeling from this study allows us to constrain the detailed geometry of the reactivated faults, as well as source parameters (focal mechanisms, stress drop, rupture length) for the larger earthquakes. Preliminary results from the November 2011 Prague sequence suggest that subsurface rupture lengths of the largest earthquakes are anomalously long with very low stress drop. We also observe very high Q (~1000 at 1 Hz) that explains the large felt areas and we find relatively low b-value and a rapid decay of aftershocks.

  6. Formation and characterization of the oxygen-rich hafnium dioxygen complexes: OHf(eta2-O2)(eta2-O3), Hf(eta2-O2)3, and Hf(eta2-O2)4.

    PubMed

    Gong, Yu; Zhou, Mingfei

    2007-09-20

    Hafnium atom oxidation by dioxygen molecules has been investigated using matrix isolation infrared absorption spectroscopy. The ground-state hafnium atom inserts into dioxygen to form primarily the previously characterized HfO(2) molecule in solid argon. Annealing allows the dioxygen molecules to diffuse and react with HfO(2) to form OHf(eta(2)-O(2))(eta(2)-O(3)), which is characterized as a side-on bonded oxo-superoxo hafnium ozonide complex. Under visible light (532 nm) irradiation, the OHf(eta(2)-O(2))(eta(2)-O(3)) complex either photochemically rearranges to a more stable Hf(eta(2)-O(2))(3) isomer, a side-on bonded di-superoxo hafnium peroxide complex, or reacts with dioxygen to form an unprecedented homoleptic tetra-superoxo hafnium complex: Hf(eta(2)-O(2))(4). The Hf(eta(2)-O(2))(4) complex is determined to possess a D(2d) geometry with a tetrahedral arrangement of four side-on bonded O(2) ligands around the hafnium atom, which thus presents an 8-fold coordination. These oxygen-rich complexes are photoreversible; that is, formation of Hf(eta(2)-O(2))(3) and Hf(eta(2)-O(2))(4) is accompanied by demise of OHf(eta(2)-O(2))(eta(2)-O(3)) under visible (532 nm) light irradiation and vice versa with UV (266 nm) light irradiation.

  7. Some Comments on the Decays of eta (550)

    DOE R&D Accomplishments Database

    Veltman, M.; Yellin, J.

    1966-07-01

    Various decay modes of the {eta}(500) are discussed. The relations, through SU{sub 3} and the Gell-Mann, Sharp, Wagner model, between the {eta}-decay modes and the modes {eta} {yields} {pi}{pi}{gamma), {pi}{sup 0} {yields} {gamma}{gamma} are investigated taking into account {eta}-{eta}{sup *} mixing. The present experimental values for the neutral branching ratios plus the shape of the {eta} {yields} {pi}{sup +}{pi}{sup {minus}}{pi}{sup 0} Dalitz plot are shown to require a 25% {vert_bar}{Delta}{rvec I}{vert_bar} = 3 contribution to the {eta} {yields} 3{pi} amplitude. The connection between a possible charge asymmetry in {eta} {yields} {pi}{sup +}{pi}{sup {minus}}{pi}{sup 0} and the branching ratio {Gamma}{sub {eta} {yields} {pi}{sup 0}e{sup +}e{sup {minus}}}/{Gamma}{sub {eta}}{sup all} is investigated in the framework of a model proposed earlier by several authors. It is shown that there is no conflict between the existing data and this model. The Dalitz plot distribution of {eta} {yields} {pi}{sup +}{pi}{sup {minus}}{pi}{sup 0} is discussed under various assumptions about the properties of the interaction responsible for the decay. (auth)

  8. Shape of the plate interface near the Mejillones Peninsula in Northern Chile inferred from high resolution relocation of Tocopilla aftershocks

    NASA Astrophysics Data System (ADS)

    Fuenzalida, A.; Schurr, B.; Lancieri, M.; Madariaga, R. I.

    2011-12-01

    The 14 November, Mw 7.8 2007 Tocopilla earthquake broke the southern part of seismic gap of northern Chile. The earthquake broke a rupture area 130 km by 30km along the deep plate interface between the Nazca and South American plates.The aftershock of this event were very well recorded by the IPOC (GFZ-IPGP-DGF) and Task Force networks (GFZ). Since the IPOC network was installed before the main Tocopilla earthquake we could locate the first two weeks of aftershocks with low accuracy.The first two weeks of aftershocks were characterised by a strong seismicity in the southern area starting with two big events of Mw 6.8 and 6.3 one day after the Tocopilla earthquake. On 29 November 2007 a Task Force (TF) Network of 20 short period instruments was installed by the GFZ team in the area of the Mejillones Peninsula. On 16 December a large Mw 6.8 slab push event took place at the center of this network. This event broke the oceanic crust of the subducted Nazca plate.(see Ruiz and Madariaga, this meeting). We have analysed in detail the TF data from its installation to 20 December. Hypocentral locations of the sequence were computed by automatic identification of the aftershocks and careful hand made readings of the arrival times of P and S phases for each seismogram. In a first study, we used the the nonlinear location software,NonLinLoc of Anthony Lomax using both a 1D model proposed by Husen from the study of earlier events in the region and the 2D model proposed by Patzwall et al from seismic profiles across the Mejillones Peninsula. We find that aftershocks were located along a thin, clearly defined zone that we interpret as the plate interface. As expected events situated off-shore of the Mejillones peninsula are less well located by Nonlinloc although our results suggest that several of these events occurred above the plate interface in the South American wedge. In a second step we relocated 850 events using the HypoDD method of Waldhauser et al with time delays

  9. Spatial correlation of aftershock locations and on-fault main shock properties

    NASA Astrophysics Data System (ADS)

    Woessner, J.; Schorlemmer, D.; Wiemer, S.; Mai, P. M.

    2006-08-01

    We quantify the correlation between spatial patterns of aftershock hypocenter locations and the distribution of coseismic slip and stress drop on a main shock fault plane using two nonstandard statistical tests. Test T1 evaluates if aftershock hypocenters are located in low-slip regions (hypothesis H1), test T2 evaluates if aftershock hypocenters occur in regions of increased shear stress (hypothesis H2). In the tests, we seek to reject the null hypotheses H0: Aftershock hypocenters are not correlated with (1) low-slip regions or (2) regions of increased shear stress, respectively. We tested the hypotheses on four strike-slip events for which multiple earthquake catalogs and multiple finite fault source models of varying accuracy exist. Because we want to retain earthquake clustering as the fundamental feature of aftershock seismicity, we generate slip distributions using a random spatial field model and derive the stress drop distributions instead of generating seismicity catalogs. We account for uncertainties in the aftershock locations by simulating them within their location error bounds. Our findings imply that aftershocks are preferentially located in regions of low-slip (u ≤ ?umax) and of increased shear stress (Δσ < 0). In particular, the correlation is more significant for relocated than for general network aftershock catalogs. However, the results show that stress drop patterns provide less information content on aftershock locations. This implies that static shear stress change of the main shock may not be the governing process for aftershock genesis.

  10. Decay of aftershock density with distance indicates triggering by dynamic stress.

    PubMed

    Felzer, K R; Brodsky, E E

    2006-06-01

    The majority of earthquakes are aftershocks, yet aftershock physics is not well understood. Many studies suggest that static stress changes trigger aftershocks, but recent work suggests that shaking (dynamic stresses) may also play a role. Here we measure the decay of aftershocks as a function of distance from magnitude 2-6 mainshocks in order to clarify the aftershock triggering process. We find that for short times after the mainshock, when low background seismicity rates allow for good aftershock detection, the decay is well fitted by a single inverse power law over distances of 0.2-50 km. The consistency of the trend indicates that the same triggering mechanism is working over the entire range. As static stress changes at the more distant aftershocks are negligible, this suggests that dynamic stresses may be triggering all of these aftershocks. We infer that the observed aftershock density is consistent with the probability of triggering aftershocks being nearly proportional to seismic wave amplitude. The data are not fitted well by models that combine static stress change with the evolution of frictionally locked faults.

  11. Decay of aftershock density with distance indicates triggering by dynamic stress

    USGS Publications Warehouse

    Felzer, K.R.; Brodsky, E.E.

    2006-01-01

    The majority of earthquakes are aftershocks, yet aftershock physics is not well understood. Many studies suggest that static stress changes trigger aftershocks, but recent work suggests that shaking (dynamic stresses) may also play a role. Here we measure the decay of aftershocks as a function of distance from magnitude 2-6 mainshocks in order to clarify the aftershock triggering process. We find that for short times after the mainshock, when low background seismicity rates allow for good aftershock detection, the decay is well fitted by a single inverse power law over distances of 0.2-50 km. The consistency of the trend indicates that the same triggering mechanism is working over the entire range. As static stress changes at the more distant aftershocks are negligible, this suggests that dynamic stresses may be triggering all of these aftershocks. We infer that the observed aftershock density is consistent with the probability of triggering aftershocks being nearly proportional to seismic wave amplitude. The data are not fitted well by models that combine static stress change with the evolution of frictionally locked faults. ?? 2006 Nature Publishing Group.

  12. Aftershocks Prediction In Italy: Estimation of Time-magnitude Distribution Model Parameters and Computation of Probabilities of Occurrence.

    NASA Astrophysics Data System (ADS)

    Lolli, B.; Gasperini, P.

    We analyzed the available instrumental catalogs of Italian earthquakes from 1960 to 1996 to compute the parameters of the time-magnitude distribution model proposed by Reasenberg e Jones (1989, 1994) and currently used to make aftershock predictions in California. We found that empirical corrections ranging from 0.3 (before 1976) to 0.5 magnitude units (between 1976 and 1980) are necessary to make the dataset ho- mogeneous over the entire period. The estimated model parameters result quite stable with respect to mainshock magnitude and sequence detection algorithm, while their spatial variations suggest that regional estimates might predict the behavior of future sequences better than ones computed by the whole Italian dataset. In order to improve the goodness of fit for sequences including multiple mainshocks (like the one occurred in Central Italy from September 1997 to May 1998) we developed a quasi epidemic model (QETAS) consisting of the superposition of a small number of Omori's pro- cesses originated by strong aftershocks. We found that the inclusion in the QETAS model of the shocks with magnitude larger than mainshock magnitude minus one (that are usually located and sized in near real-time by the observatories) improves significantly the ability of the algorithm to predict the sequence behaviors.

  13. High Frequency Monitoring Reveals Aftershocks in Subcritical Crack Growth

    NASA Astrophysics Data System (ADS)

    Stojanova, M.; Santucci, S.; Vanel, L.; Ramos, O.

    2014-03-01

    By combining direct imaging and acoustic emission measurements, the subcritical propagation of a crack in a heterogeneous material is analyzed. Both methods show that the fracture proceeds through a succession of discrete events. However, the macroscopic opening of the fracture captured by the images results from the accumulation of more-elementary events detected by the acoustics. When the acoustic energy is cumulated over large time scales corresponding to the image acquisition rate, a similar statistics is recovered. High frequency acoustic monitoring reveals aftershocks responsible for a time scale dependent exponent of the power law energy distributions. On the contrary, direct imaging, which is unable to resolve these aftershocks, delivers a misleading exponent value.

  14. The detection of companion stars to the Cepheid variables ETA Aquilae and T Monocerotis

    NASA Technical Reports Server (NTRS)

    Mariska, J. T.; Doschek, G. A.; Feldman, U.

    1981-01-01

    Ultraviolet spectra of the classical Cepheid variables eta Aq1 and T Mon at several phases in their periods were obtained with IUE. For eta Aq1 significant ultraviolet emission is detected at wavelengths less than 1600 A, where little flux is expected from classical Cepheids. Furthermore, the emission at wavelengths less than about 1600 A does not vary with phase. Comparison with model atmosphere flux distributions shows that the nonvariable emission is consistent with the flux expected from a main sequence companion star with an effective temperature of about 9500 K (AO V - A1 V). For T Mon a nonvarying component to the ultraviolet emission is observed for wavelengths less than 2600 A. Comparison with model atmosphere flux distributions suggests that the companion has an effective temperature of around 10,000 K (AO) and is near the main sequence.

  15. Physics and Outlook for Rare, All-neutral Eta Decays

    SciTech Connect

    Mack, David J.

    2014-06-01

    The $\\eta$ meson provides a laboratory to study isospin violation and search for new flavor-conserving sources of C and CP violation with a sensitivity approaching $10^{-6}$ of the isospin-conserving strong amplitude. Some of the most interesting rare $\\eta$ decays are the neutral modes, yet the effective loss of photons from the relatively common decay $\\eta \\rightarrow 3\\pi^0 \\rightarrow 6\\gamma$ (33$\\%$) has largely limited the sensitivity for decays producing 3-5$\\gamma$'s. Particularly important relevant branches include the highly suppressed $\\eta \\rightarrow \\pi^0 2\\gamma \\rightarrow 4\\gamma$, which provides a rare window on testing models of $O(p^6)$ contributions in ChPTh, and $\\eta \\rightarrow 3\\gamma$ and $\\eta \\rightarrow 2\\pi^0 \\gamma \\rightarrow 5\\gamma$ which provide direct constraints on C violation in flavor-conserving processes. The substitution of lead tungstate in the forward calorimeter of the GluEx setup in Jefferson Lab's new Hall D would allow dramatically improved measurements. The main niche of this facility, which we call the JLab Eta Factory (JEF), would be $\\eta$ decay neutral modes. However, this could likely be expanded to rare $\\eta'(958)$ decays for low energy QCD studies as well as $\\eta$ decays involving muons for new physics searches.

  16. Eta-mesic nuclei: Past, present, future

    DOE PAGES

    Haider, Q.; Liu, Lon -Chang

    2015-09-23

    Eta-mesic nucleus or the quasibound nuclear state of an eta (η) meson in a nucleus is caused by strong interaction force alone. This new type of nuclear species, which extends the landscape of nuclear physics, has been extensively studied since its prediction in 1986. We review and analyze in great detail the models of the fundamental η–nucleon interaction leading to the formation of an η–mesic nucleus, the methods used in calculating the properties of a bound η, and the approaches employed in the interpretation of the pertinent experimental data. In view of the successful observation of the η–mesic nucleus 25Mgηmore » and other promising experimental results, future direction in searching for more η–mesic nuclei is suggested.« less

  17. Eta-mesic nuclei: Past, present, future

    SciTech Connect

    Haider, Q.; Liu, Lon -Chang

    2015-09-23

    Eta-mesic nucleus or the quasibound nuclear state of an eta (η) meson in a nucleus is caused by strong interaction force alone. This new type of nuclear species, which extends the landscape of nuclear physics, has been extensively studied since its prediction in 1986. We review and analyze in great detail the models of the fundamental η–nucleon interaction leading to the formation of an η–mesic nucleus, the methods used in calculating the properties of a bound η, and the approaches employed in the interpretation of the pertinent experimental data. In view of the successful observation of the η–mesic nucleus 25Mgη and other promising experimental results, future direction in searching for more η–mesic nuclei is suggested.

  18. Disease aftershocks - The health effects of natural disasters

    USGS Publications Warehouse

    Guptill, S.C.

    2001-01-01

    While the initial activity of a natural disaster event may directly injure or kill a number of people, it is possible that a significant number of individuals will be affected by disease outbreaks that occur after the first effects of the disaster have passed. Coupling the epidemiologist's knowledge of disease outbreaks with geographic information systems and remote sensing technology could help natural disaster relief workers to prevent additional victims from disease aftershocks.

  19. Direct test of static stress versus dynamic stress triggering of aftershocks

    USGS Publications Warehouse

    Pollitz, F.F.; Johnston, M.J.S.

    2006-01-01

    Aftershocks observed over time scales of minutes to months following a main shock are plausibly triggered by the static stress change imparted by the main shock, dynamic shaking effects associated with passage of seismic waves from the main shock, or a combination of the two. We design a direct test of static versus dynamic triggering of aftershocks by comparing the near-field temporal aftershock patterns generated by aseismic and impulsive events occurring in the same source area. The San Juan Bautista, California, area is ideally suited for this purpose because several events of both types of M???5 have occurred since 1974. We find that aftershock rates observed after impulsive events are much higher than those observed after aseismic events, and this pattern persists for several weeks after the event. This suggests that, at least in the near field, dynamic triggering is the dominant cause of aftershocks, and that it generates both immediate and delayed aftershock activity.

  20. RETAS Stochastic Model to Study Aftershock Rate Decay of the Denali Fault M7.9 Earthquake, November 3, 2002

    SciTech Connect

    Gospodinov, D. K.; Marekova, E. G.; Marinov, A. T.

    2007-04-23

    A RETAS model is used to analyze aftershock rate decay after the Denaly Fault earthquake with a main shock magnitude MS=7.9. We verify different variants of the RETAS model ranging from the limit case Mth = Mmain (main shock) to the case when Mth=Mo (lower magnitude cut-off). We first test the model on simulated data following the MOF (modified Omori formula) model. The results for the Denali Fault sequence reveal the best fit model to be RETAS with a triggering threshold Mth =3.2.

  1. Eta Carinae and Other Luminous Blue Variables

    NASA Technical Reports Server (NTRS)

    Corcoran, M. F.

    2006-01-01

    Luminous Blue Variables (LBVs) are believed to be evolved, extremely massive stars close to the Eddington Limit and hence prone to bouts of large-scale, unstable mass loss. I discuss current understanding of the evolutionary state of these objects, the role duplicity may play and known physical characteristics of these stars using the X-ray luminous LBVs Eta Carinae and HD 5980 as test cases.

  2. High-Resolution Low Power, Intergrated Aftershock and Microzonation System

    NASA Astrophysics Data System (ADS)

    Zimakov, L.; Passmore, P.

    2012-04-01

    Refraction Technology, Inc. has developed a self-contained, fully integrated Aftershock System, model 160-03, providing the customer simple and quick deployment during aftershock emergency mobilization and microzonation studies. The 160-03 has no external cables or peripheral equipment for command/control and operation in the field. The 160-03 contains three major components integrated in one case: a) 24-bit resolution state-of-the art low power ADC with CPU and Lid interconnect boards; b) power source; and c) three component 2 Hz sensors (two horizontals and one vertical), and built-in ±4g accelerometer. Optionally, the 1 Hz sensors can be built-in the 160-03 system at the customer's request. The self-contained rechargeable battery pack provides power autonomy up to 7 days during data acquisition at 200 sps on continuous three weak motion and triggered three strong motion recording channels. For longer power autonomy, the 160-03 Aftershock System battery pack can be charged from an external source (solar power system). The data in the field is recorded to a built-in swappable USB flash drive. The 160-03 configuration is fixed based on a configuration file stored on the system. The detailed specifications and performance are presented and discussed

  3. GHRS Observations of LISM towards eta UMa

    NASA Astrophysics Data System (ADS)

    Frisch, P. C.

    1998-01-01

    The star eta UMa (l=101(deg) , b=+65(deg) , d=31 pc) samples local interstellar matter (LISM) in a high latitude region. The Sun is ``above'' most of the mass of the Local Fluff cloud complex, yielding low total interstellar column densities towards eta UMa. Thus cloud properties can be determined with minimal confusion caused by velocity component blending in this sightline. The physical properties of the cloud surrounding the solar system become the boundary conditions of the solar system. A key property of the surrounding cloud is the proton density, since the Alfven velocity regulates the formation of a bow shock around the heliosphere, and since charge exchange between interstellar p(+) and H(deg) yields a pile-up of H(deg) at the heliopause. As a result, the interstellar electron density in the surrounding cloud is an important parameter in understanding the configuration of the outer heliosphere regions. We present GHRS Echelle A and Echelle B data on C({deg) *}, C(deg) , Mg(deg) and Mg(+) . These data allow us to compare electron densities as estimated from the ratios N(C({deg) *})/N(C(deg) ) versus N(Mg(deg) )/N(Mg(+) ) for a relatively simple sightline. These electron densities are also compared to electron densities determined from optical Ca(+) observations towards eta UMa by Frisch and Welty (in preparation).

  4. Aftershock distribution of a M 2.1 earthquake near a geologic structure boundary in a deep South African gold mine

    NASA Astrophysics Data System (ADS)

    Naoi, M.; Kwiatek, G.; Yabe, Y.; Philipp, J.; Nakatani, M.; Igarashi, T.

    2008-12-01

    We are operating a high-frequency (up to 200 kHz) seismic network at a depth of 3550 m in a deep South African gold mine (Nakatani et al. 2007). An earthquake of M 2.1 occurred within our network on December 27, 2007 (Yabe et al. 2008). In 150 hours following the event, our AE network detected approx. 20,000 events within 100 m from the center of the our network. This aftershock sequence obeys Omori"fs Law. In mines, the number of aftershocks is usually small, but this seems to be simply because vast majority of aftershocks are smaller than detection limit. During the same period, the seismic network of the mine (detection threshold approx. Mw -0.5) detected only nine earthquakes at most. If we assume GR law, comparison of the numbers of aftershocks detected by the both networks suggests that the detection threshold of our AE network is about M - 4. In the area, there is a vertically intruded rock structure made of solidified magma (PG dyke). Thickness is 20 ~ 30 m. This earthquake was expected to be induced by mining around this dyke in 2007 ~ 2008. The boundary position between the dyke and the host rock has been surveyed by the mine, using cores from many boreholes. In addition, our ultrasonic transmission tests have indicated that this contact is generally sharp and there is significant velocity contrast. Velocities within dyke and host rock were fairly uniform (Dyke Vp, Vs are 6.90 km/s, 3.92 km/s respectively, Host Rock Vp Vs are 6.00 km/s, 3.65 km/s respectively). The hypocenter of the M 2.1 earthquake is located within the dyke, not on the contact. The aftershocks lined up on a plane, 30 degrees off vertical; They do not seem to be on the boundary because the dip of the boundary is almost vertical. The distance between them and the closest station of our network was about 6 m. The upper end of aftershock distribution is not clear because of detection limit of our AE network. On the other hand, the downward distribution of the aftershocks seems to be

  5. Study of B meson decays with excited eta and eta' mesons.

    PubMed

    Aubert, B; Bona, M; Boutigny, D; Karyotakis, Y; Lees, J P; Poireau, V; Prudent, X; Tisserand, V; Zghiche, A; Tico, J Garra; Grauges, E; Lopez, L; Palano, A; Pappagallo, M; Eigen, G; Stugu, B; Sun, L; Abrams, G S; Battaglia, M; Brown, D N; Button-Shafer, J; Cahn, R N; Groysman, Y; Jacobsen, R G; Kadyk, J A; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lopes Pegna, D; Lynch, G; Mir, L M; Orimoto, T J; Osipenkov, I L; Ronan, M T; Tackmann, K; Tanabe, T; Wenzel, W A; del Amo Sanchez, P; Hawkes, C M; Watson, A T; Held, T; Koch, H; Pelizaeus, M; Schroeder, T; Steinke, M; Walker, D; Asgeirsson, D J; Cuhadar-Donszelmann, T; Fulsom, B G; Hearty, C; Mattison, T S; McKenna, J A; Barrett, M; Khan, A; Saleem, M; Teodorescu, L; Blinov, V E; Bukin, A D; Druzhinin, V P; Golubev, V B; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Todyshev, K Yu; Bondioli, M; Curry, S; Eschrich, I; Kirkby, D; Lankford, A J; Lund, P; Mandelkern, M; Martin, E C; Stoker, D P; Abachi, S; Buchanan, C; Foulkes, S D; Gary, J W; Liu, F; Long, O; Shen, B C; Zhang, L; Paar, H P; Rahatlou, S; Sharma, V; Berryhill, J W; Campagnari, C; Cunha, A; Dahmes, B; Hong, T M; Kovalskyi, D; Richman, J D; Beck, T W; Eisner, A M; Flacco, C J; Heusch, C A; Kroseberg, J; Lockman, W S; Schalk, T; Schumm, B A; Seiden, A; Wilson, M G; Winstrom, L O; Chen, E; Cheng, C H; Fang, F; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Andreassen, R; Mancinelli, G; Meadows, B T; Mishra, K; Sokoloff, M D; Blanc, F; Bloom, P C; Chen, S; Ford, W T; Hirschauer, J F; Kreisel, A; Nagel, M; Nauenberg, U; Olivas, A; Smith, J G; Ulmer, K A; Wagner, S R; Zhang, J; Gabareen, A M; Soffer, A; Toki, W H; Wilson, R J; Winklmeier, F; Altenburg, D D; Feltresi, E; Hauke, A; Jasper, H; Merkel, J; Petzold, A; Spaan, B; Wacker, K; Klose, V; Kobel, M J; Lacker, H M; Mader, W F; Nogowski, R; Schubert, J; Schubert, K R; Schwierz, R; Sundermann, J E; Volk, A; Bernard, D; Bonneaud, G R; Latour, E; Lombardo, V; Thiebaux, Ch; Verderi, M; Clark, P J; Gradl, W; Muheim, F; Playfer, S; Robertson, A I; Watson, J E; Xie, Y; Andreotti, M; Bettoni, D; Bozzi, C; Calabrese, R; Cecchi, A; Cibinetto, G; Franchini, P; Luppi, E; Negrini, M; Petrella, A; Piemontese, L; Prencipe, E; Santoro, V; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Pacetti, S; Patteri, P; Peruzzi, I M; Piccolo, M; Rama, M; Zallo, A; Buzzo, A; Contri, R; Lo Vetere, M; Macri, M M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Chaisanguanthum, K S; Morii, M; Wu, J; Dubitzky, R S; Marks, J; Schenk, S; Uwer, U; Bard, D J; Dauncey, P D; Flack, R L; Nash, J A; Panduro Vazquez, W; Tibbetts, M; Behera, P K; Chai, X; Charles, M J; Mallik, U; Ziegler, V; Cochran, J; Crawley, H B; Dong, L; Eyges, V; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Gao, Y Y; Gritsan, A V; Guo, Z J; Lae, C K; Denig, A G; Fritsch, M; Schott, G; Arnaud, N; Béquilleux, J; D'Orazio, A; Davier, M; Grosdidier, G; Höcker, A; Lepeltier, V; Le Diberder, F; Lutz, A M; Pruvot, S; Rodier, S; Roudeau, P; Schune, M H; Serrano, J; Sordini, V; Stocchi, A; Wang, W F; Wormser, G; Lange, D J; Wright, D M; Bingham, I; Burke, J P; Chavez, C A; Forster, I J; Fry, J R; Gabathuler, E; Gamet, R; Hutchcroft, D E; Payne, D J; Schofield, K C; Touramanis, C; Bevan, A J; George, K A; Di Lodovico, F; Menges, W; Sacco, R; Cowan, G; Flaecher, H U; Hopkins, D A; Paramesvaran, S; Salvatore, F; Wren, A C; Brown, D N; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Chia, Y M; Edgar, C L; Lafferty, G D; West, T J; Yi, J I; Anderson, J; Chen, C; Jawahery, A; Roberts, D A; Simi, G; Tuggle, J M; Blaylock, G; Dallapiccola, C; Hertzbach, S S; Li, X; Moore, T B; Salvati, E; Saremi, S; Cowan, R; Dujmic, D; Fisher, P H; Koeneke, K; Sciolla, G; Sekula, S J; Spitznagel, M; Taylor, F; Yamamoto, R K; Zhao, M; Zheng, Y; Mclachlin, S E; Patel, P M; Robertson, S H; Lazzaro, A; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Simard, M; Taras, P; Viaud, F B; Nicholson, H; De Nardo, G; Fabozzi, F; Lista, L; Monorchio, D; Sciacca, C; Baak, M A; Raven, G; Snoek, H L; Jessop, C P; Knoepfel, K J; LoSecco, J M; Benelli, G; Corwin, L A; Honscheid, K; Kagan, H; Kass, R; Morris, J P; Rahimi, A M; Regensburger, J J; Wong, Q K; Blount, N L; Brau, J; Frey, R; Igonkina, O; Kolb, J A; Lu, M; Rahmat, R; Sinev, N B; Strom, D; Strube, J; Torrence, E; Gagliardi, N; Gaz, A; Margoni, M; Morandin, M; Pompili, A; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Ben-Haim, E; Briand, H; Calderini, G; Chauveau, J; David, P; Del Buono, L; de la Vaissière, Ch; Hamon, O; Leruste, Ph; Malclès, J; Ocariz, J; Perez, A; Prendki, J; Gladney, L; Biasini, M; Covarelli, R; Manoni, E; Angelini, C; Batignani, G; Bettarini, S; Carpinelli, M; Cenci, R; Cervelli, A; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Mazur, M A; Morganti, M; Neri, N; Paoloni, E; Rizzo, G; Walsh, J J; Haire, M; Biesiada, J; Elmer, P; Lau, Y P; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Baracchini, E; Bellini, F; Cavoto, G; del Re, D; Di Marco, E; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Jackson, P D; Li Gioi, L; Mazzoni, M A; Morganti, S; Piredda, G; Polci, F; Renga, F; Voena, C; Ebert, M; Hartmann, T; Schröder, H; Waldi, R; Adye, T; Castelli, G; Franek, B; Olaiya, E O; Ricciardi, S; Roethel, W; Wilson, F F; Emery, S; Escalier, M; Gaidot, A; Ganzhur, S F; Hamel de Monchenault, G; Kozanecki, W; Vasseur, G; Yèche, Ch; Zito, M; Chen, X R; Liu, H; Park, W; Purohit, M V; Wilson, J R; Allen, M T; Aston, D; Bartoldus, R; Bechtle, P; Berger, N; Claus, R; Coleman, J P; Convery, M R; Dingfelder, J C; Dorfan, J; Dubois-Felsmann, G P; Dunwoodie, W; Field, R C; Glanzman, T; Gowdy, S J; Graham, M T; Grenier, P; Hast, C; Hryn'ova, T; Innes, W R; Kaminski, J; Kelsey, M H; Kim, H; Kim, P; Kocian, M L; Leith, D W G S; Li, S; Luitz, S; Luth, V; Lynch, H L; MacFarlane, D B; Marsiske, H; Messner, R; Muller, D R; O'Grady, C P; Ofte, I; Perazzo, A; Perl, M; Pulliam, T; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Snyder, A; Stelzer, J; Su, D; Sullivan, M K; Suzuki, K; Swain, S K; Thompson, J M; Va'vra, J; van Bakel, N; Wagner, A P; Weaver, M; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Yi, K; Young, C C; Burchat, P R; Edwards, A J; Majewski, S A; Petersen, B A; Wilden, L; Ahmed, S; Alam, M S; Bula, R; Ernst, J A; Jain, V; Pan, B; Saeed, M A; Wappler, F R; Zain, S B; Krishnamurthy, M; Spanier, S M; Eckmann, R; Ritchie, J L; Ruland, A M; Schilling, C J; Schwitters, R F; Izen, J M; Lou, X C; Ye, S; Bianchi, F; Gallo, F; Gamba, D; Pelliccioni, M; Bomben, M; Bosisio, L; Cartaro, C; Cossutti, F; Della Ricca, G; Lanceri, L; Vitale, L; Azzolini, V; Lopez-March, N; Martinez-Vidal, F; Milanes, D A; Oyanguren, A; Albert, J; Banerjee, Sw; Bhuyan, B; Hamano, K; Kowalewski, R; Nugent, I M; Roney, J M; Sobie, R J; Harrison, P F; Ilic, J; Latham, T E; Mohanty, G B; Band, H R; Chen, X; Dasu, S; Flood, K T; Hollar, J J; Kutter, P E; Pan, Y; Pierini, M; Prepost, R; Wu, S L; Neal, H

    2008-08-29

    Using 383 x 10(6) BBover pairs from the BABAR data sample, we report results for branching fractions of six charged B-meson decay modes, where a charged kaon recoils against a charmless resonance decaying to KKover* or etapipi final states with mass in the range (1.2-1.8) GeV/c2. We observe a significant enhancement at the low KKover* invariant mass which is interpreted as B+-->eta(1475)K+, find evidence for the decay B+-->eta(1295)K+, and place upper limits on the decays B+-->eta(1405)K+, B+-->f1(1285)K+, B+-->f1(1420)K+, and B+-->phi(1680)K+. PMID:18851601

  6. Interaction of eta mesons with nuclei.

    PubMed

    Kelkar, N G; Khemchandani, K P; Upadhyay, N J; Jain, B K

    2013-06-01

    Back in the mid-1980s, a new branch of investigation related to the interaction of eta mesons with nuclei came into existence. It started with the theoretical prediction of possible exotic states of eta mesons and nuclei bound by the strong interaction and later developed into an extensive experimental program to search for such unstable states as well as understand the underlying interaction via eta-meson producing reactions. The vast literature of experimental as well as theoretical works that studied various aspects of eta-producing reactions such as the π(+)n → ηp, pd → (3)Heη, p (6)Li → (7)Be η and γ (3)He → η X, to name a few, had but one objective in mind: to understand the eta-nucleon (ηN) and hence the η-nucleus interaction which could explain the production data and confirm the existence of some η-mesic nuclei. In spite of these efforts, there remain uncertainties in the knowledge of the ηN and hence the η-nucleus interaction. Therefore, this review is an attempt to bind together the findings in these works and draw some global and specific conclusions which can be useful for future explorations.The ηN scattering length (which represents the strength of the η-nucleon interaction) using different theoretical models and analyzing the data on η production in pion, photon and proton induced reactions was found to be spread out in a wide range, namely, 0.18 ≤ Re aηN ≤ 1.03 fm and 0.16 ≤ Rm aηN ≤ 0.49 fm. Theoretical searches of heavy η-mesic nuclei based on η-nucleus optical potentials and lighter ones based on Faddeev type few-body approaches predict the existence of several quasibound and resonant states. Although some hints of η-mesic states such as (3)(η)He and (25)(η)Mg do exist from previous experiments, the promise of clearer signals for the existence of η-mesic nuclei lies in the experiments to be performed at the J-PARC, MAMI and COSY facilities in the near future. This review is aimed at giving an overall status

  7. DNA polymerase eta undergoes alternative splicing, protects against UV sensitivity and apoptosis, and suppresses Mre11-dependent recombination.

    PubMed

    Thakur, M; Wernick, M; Collins, C; Limoli, C L; Crowley, E; Cleaver, J E

    2001-11-01

    Polymerase eta (pol eta) is a low-fidelity DNA polymerase that is the product of the gene, POLH, associated with the human XP variant disorder in which there is an extremely high level of solar-induced skin carcinogenesis. The complete human genomic sequence spans about 40 kb containing 10 coding exons and a cDNA of 2.14 kb; exon I is untranslated and is 6 kb upstream from the first coding exon. Using bacterial artificial chromosomes (BACs), the gene was mapped to human chromosome band 6p21 and mouse band 17D. The gene is expressed in most tissues, except for very low or undetectable levels in peripheral lymphocytes, fetal spleen, and adult muscle; exon II, however, is frequently spliced out in normal cells and in almost half the transcripts in the testis and fetal liver. Expression of POLH in a multicopy episomal vector proved nonviable, suggesting that overexpression is toxic. Expression from chromosomally integrated linear copies using either an EF1-alpha or CMV promoter was functional, resulting in cell lines with low or high levels of pol eta protein, respectively. Point mutations in the center of the gene and in a C-terminal cysteine and deletion of exon II resulted in inactivation, but addition of a terminal 3 amino acid C-terminal tag, or an N- or C-terminal green fluorescent protein, had no effect on function. A low level of expression of pol eta eliminated hMre11 recombination and partially restored UV survival, but did not prevent UV-induced apoptosis, which required higher levels of expression. Polymerase eta is therefore involved in S-phase checkpoint and signal transduction pathways that lead to arrest in S, apoptosis, and recombination. In normal cells, the predominant mechanism of replication of UV damage involves pol eta-dependent bypass, and Mre11-dependent recombination that acts is a secondary, backup mechanism when cells are severely depleted of pol eta.

  8. April 7, 2009, Mw 5.5 aftershock of the L'Aquila earthquake: seismogenic fault geometry and its implication for the central Apennines active extensional tectonics (Italy).

    NASA Astrophysics Data System (ADS)

    Adinolfi, Guido Maria; Lavecchia, Giusy; De Matteis, Raffaella; Nardis Rita, De; Francesco, Brozzetti; Federica, Ferrarini; Zollo, Aldo

    2015-04-01

    On April 6, 2009 (at 01:32 UTC) a Mw 6.3 earthquake hit the town of L'Aquila (central Italy) and surrounding villages causing fatalities and severe damage in the area. After few days, a nearly 40-km-long extensional fault system was activated generating both northward and southward seismicity migration along the NW-SE trending sector of central Apennines. During the intense aftershocks sequence, different sesmogenic sources with a distinct geometry, size and the degree of involvement were reactivated. Among the relevant aftershocks with Mw 5.0 to 5.5, the largest one occurred on April 7 (at 17:47 UTC), 9 km SE-ward of the mainshock involving a source seated at much greater depths (~14 km). Despite the enormous number of studies of the 2009 L'Aquila earthquake, mainly focused on the various geological and seismological aspects of the main Paganica source, the April 7 strongest aftershock (Mw 5.5) has not yet been deeply investigated. Consistent geometric and kinematic correlations between the geological and seismological data about this seismogenic source are missing. There are still open questions concerning its unresolved geometry and the unknown style of the central Apennines structure activated at greater depths during the 2009 L'Aquila seismic sequence. Furthermore, some authors (Lavecchia et al., 2012) have supposed that the April 7, 2009 aftershock (Mw 5.5) occurred onto an high dip segment (~50°) of an east-dipping extensional basal detachment with a potential surface expression outcropping in the area of the eastern Sabina-Simbruini Mts. In this work we propose a seismological analysis of the April 7, 2009 aftershock (Mw 5.5) rupture process. In order to define the unresolved source geometry, we computed the focal mechanism through the time domain, moment tensor full waveform inversion (Dreger and Helmberger, 1993). Also, we estimated the apparent source time functions (ASTFs) by deconvolution of the impulse response of the medium from the recorded data

  9. Measurement of the gamma gamma* --> eta and gamma gamma* --> eta' transition form factors

    SciTech Connect

    del Amo Sanchez et al, P.

    2011-02-07

    We study the reactions e{sup +}e{sup -} {yields} e{sup +}e{sup -} {eta}{sup (/)} in the single-tag mode and measure the {gamma}{gamma}* {yields} {eta}{sup (/)} transition form factors in the momentum transfer range from 4 to 40 GeV{sup 2}. The analysis is based on 469 fb{sup -1} of integrated luminosity collected at PEP-II with the BABAR detector at e{sup +}e{sup -} center-of-mass energies near 10.6 GeV.

  10. Complex faulting associated with the 22 December 2003 Mw 6.5 San Simeon California, earthquake, aftershocks and postseismic surface deformation

    USGS Publications Warehouse

    McLaren, M.K.; Hardebeck, J.L.; van der Elst, N.; Unruh, J.R.; Bawden, G.W.; Blair, J.L.

    2008-01-01

    We use data from two seismic networks and satellite interferometric synthetic aperture radar (InSAR) imagery to characterize the 22 December 2003 Mw 6.5 San Simeon earthquake sequence. Absolute locations for the mainshock and nearly 10,000 aftershocks were determined using a new three-dimensional (3D) seismic velocity model; relative locations were obtained using double difference. The mainshock location found using the 3D velocity model is 35.704?? N, 121.096?? W at a depth of 9.7 ?? 0.7 km. The aftershocks concentrate at the northwest and southeast parts of the aftershock zone, between the mapped traces of the Oceanic and Nacimiento fault zones. The northwest end of the mainshock rupture, as defined by the aftershocks, projects from the mainshock hypocenter to the surface a few kilometers west of the mapped trace of the Oceanic fault, near the Santa Lucia Range front and the > 5 mm postseismic InSAR imagery contour. The Oceanic fault in this area, as mapped by Hall (1991), is therefore probably a second-order synthetic thrust or reverse fault that splays upward from the main seismogenic fault at depth. The southeast end of the rupture projects closer to the mapped Oceanic fault trace, suggesting much of the slip was along this fault, or at a minimum is accommodating much of the postseismic deformation. InSAR imagery shows ???72 mm of postseismic uplift in the vicinity of maximum coseismic slip in the central section of the rupture, and ???48 and ???45 mm at the northwest and southeast end of the aftershock zone, respectively. From these observations, we model a ???30-km-long northwest-trending northeast-dipping mainshock rupture surface - called the mainthrust - which is likely the Oceanic fault at depth, a ???10-km-long southwest-dipping backthrust parallel to the mainthrust near the hypocenter, several smaller southwest-dipping structures in the southeast, and perhaps additional northeast-dipping or subvertical structures southeast of the mainshock plane

  11. Statistical analysis of the induced Basel 2006 earthquake sequence: introducing a probability-based monitoring approach for Enhanced Geothermal Systems

    NASA Astrophysics Data System (ADS)

    Bachmann, C. E.; Wiemer, S.; Woessner, J.; Hainzl, S.

    2011-08-01

    reduced and then stopped after another ML 2.5 event. A few hours later, an earthquake with ML 3.4, felt within the city, occurred, which led to bleed-off of the well. A risk study was later issued with the outcome that the experiment could not be resumed. We analyse the statistical features of the sequence and show that the sequence is well modelled with the Omori-Utsu law following the termination of water injection. Based on this model, the sequence will last 31+29/-14 years to reach the background level. We introduce statistical models based on Reasenberg and Jones and Epidemic Type Aftershock Sequence (ETAS) models, commonly used to model aftershock sequences. We compare and test different model setups to simulate the sequences, varying the number of fixed and free parameters. For one class of the ETAS models, we account for the flow rate at the injection borehole. We test the models against the observed data with standard likelihood tests and find the ETAS model accounting for the on flow rate to perform best. Such a model may in future serve as a valuable tool for designing probabilistic alarm systems for EGS experiments.

  12. Using aftershocks to Image the Subducting Pacific Plate in a Region of Deep Slow Slip, Hikurangi Margin, New Zealand

    NASA Astrophysics Data System (ADS)

    Jacobs, K. M.; Hirschberg, H.; Louie, J. N.; Savage, M. K.; Bannister, S. C.

    2014-12-01

    We present seismic migrations using aftershocks of two M>6 earthquakes as sources. The Southern Cook Strait earthquake sequence, beginning on 19 July 2013, included the 21 July M=6.5 and 16 August M=6.6 2013 earthquakes, which were the largest shallow earthquakes to strike the Wellington region since 1942. Following the two largest earthquakes we began the Seddon Earthquake Aftershock Structural Investigation (SEASI) and deployed a line of 21 seismometers stretching approximately 400 km along the strike of the Hikurangi subduction zone in order to use aftershocks to illuminate the structure of the subducted Pacific slab. The SEASI line ties into the SAHKE line, which was an array of up to 900 seismometers that recorded air gun and explosion shots in deployments from 2009-2011. The SAHKE project characterized the structures perpendicular to the strike of the subduction zone. Our results use the SAHKE line as a starting point and look for strike-parallel variations in the depth of the Moho and other structures. Previous studies have suggested potential changes along strike in this region, and deep slow slip events (> 35 km) are also observed north of Wellington, further indicating that variation in properties exists along slab strike. We have used 246 M > 3 earthquakes that occurred from September 2013 through January 2014 to create common receiver gathers. Multicomponent prestack depth migration of these receiver gathers, with operator antialiasing control and prestack coherency filtering, produces reflectivity sections using a 1-D velocity model derived from the SAHKE project. Relocation of aftershocks of the Seddon earthquakes using the deployment of a temporary array by New Zealand GeoNet facilitates the migration. An initial P-P migration shows a north-dipping reflector at 15-25 km depth under the earthquake sequence, and suggests the Moho at 20-25 km depth. From Wellington, a reflector dips very gently south from 25-35 km depth, which is probably the slab

  13. Does Turbulence in the Iron Convection Zone Cause the Massive Outbursts of Eta Carinae?

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1999-01-01

    Taken at face value, the observed properties of the central object in Eta-Car suggest a very massive, hot main-sequence star, only slightly evolved. If this is so, the star's extraordinarily high steady rate of mass loss must dynamically perturb its outer envelope down to the iron convection zone, where the kinetic energy associated with turbulent convection can be directly fed into mass ejection. Runaway mass loss, triggered by either internal (pulsational, rotational) or external (tidal) forcing, would produce a secular oscillation of the outer envelope. In either case, the oscillation is potentially able to account for the observed approximately 5 yr cycles of visual outbursts in Eta-Car, including the giant eruption of 1843.

  14. Software Users Manual (SUM): Extended Testability Analysis (ETA) Tool

    NASA Technical Reports Server (NTRS)

    Maul, William A.; Fulton, Christopher E.

    2011-01-01

    This software user manual describes the implementation and use the Extended Testability Analysis (ETA) Tool. The ETA Tool is a software program that augments the analysis and reporting capabilities of a commercial-off-the-shelf (COTS) testability analysis software package called the Testability Engineering And Maintenance System (TEAMS) Designer. An initial diagnostic assessment is performed by the TEAMS Designer software using a qualitative, directed-graph model of the system being analyzed. The ETA Tool utilizes system design information captured within the diagnostic model and testability analysis output from the TEAMS Designer software to create a series of six reports for various system engineering needs. The ETA Tool allows the user to perform additional studies on the testability analysis results by determining the detection sensitivity to the loss of certain sensors or tests. The ETA Tool was developed to support design and development of the NASA Ares I Crew Launch Vehicle. The diagnostic analysis provided by the ETA Tool was proven to be valuable system engineering output that provided consistency in the verification of system engineering requirements. This software user manual provides a description of each output report generated by the ETA Tool. The manual also describes the example diagnostic model and supporting documentation - also provided with the ETA Tool software release package - that were used to generate the reports presented in the manual

  15. Role of static stress diffusion in the spatiotemporal organization of aftershocks.

    PubMed

    Lippiello, E; de Arcangelis, L; Godano, C

    2009-07-17

    We investigate the spatial distribution of aftershocks, and we find that aftershock linear density exhibits a maximum that depends on the main shock magnitude, followed by a power law decay. The exponent controlling the asymptotic decay and the fractal dimensionality of epicenters clearly indicate triggering by static stress. The nonmonotonic behavior of the linear density and its dependence on the main shock magnitude can be interpreted in terms of diffusion of static stress. This is supported by the power law growth with exponent H approximately 0.5 of the average main-aftershock distance. Implementing static stress diffusion within a stochastic model for aftershock occurrence, we are able to reproduce aftershock linear density spatial decay, its dependence on the main shock magnitude, and its evolution in time.

  16. A LIGHTHOUSE EFFECT IN ETA CARINAE

    SciTech Connect

    Madura, Thomas I.; Groh, Jose H.

    2012-02-20

    We present a new model for the behavior of scattered time-dependent, asymmetric near-UV emission from the nearby ejecta of {eta} Car. Using a three-dimensional (3D) hydrodynamical simulation of {eta} Car's binary colliding winds, we show that the 3D binary orientation derived by Madura et al. in 2012 is capable of explaining the asymmetric near-UV variability observed in the Hubble Space Telescope Advanced Camera for Surveys/High Resolution Camera F220W images of Smith et al.. Models assuming a binary orientation with i Almost-Equal-To 130 Degree-Sign -145 Degree-Sign , {omega} Almost-Equal-To 230 Degree-Sign -315 Degree-Sign , P.A.{sub z} Almost-Equal-To 302 Degree-Sign -327 Degree-Sign are consistent with the observed F220W near-UV images. We find that the hot binary companion does not significantly contribute to the near-UV excess observed in the F220W images. Rather, we suggest that a bore-hole effect and the reduction of Fe II optical depths inside the wind-wind collision cavity carved in the extended photosphere of the primary star lead to the time-dependent directional illumination of circumbinary material as the companion moves about in its highly elliptical orbit.

  17. eta Carinae: physical information from photometry

    NASA Astrophysics Data System (ADS)

    van Genderen, A. M.; de Groot, M.; Sterken, C.

    2001-06-01

    The very first physical information one can get from optical photometry is that eta Car is variable. Figure 1 shows the light curve from 1600 to 2000. Most reseachers agree with the main interpretations of the various features as shown by the light curve. The eruptive phases are called S Dor- (SD-) eruptions as opposed to the S Dor- (SD-) phases, which are responsible for the oscillating light variations (due to slow pulsations) with a time-scale of years (van Genderen 2001). The rising trend after 1935 is called the 'secular rise' and is mainly due to a decrease of circumstellar extinction, i.e. a decrease of self-extinction by the expanding Homunculus. A model for the trend of the decrease fits the time interval 1935-2000 satisfactorily (van Genderen et al. 1994, and see dotted curve in Figure 1 presented here). The optical (and near-IR) photometry of eta Car is hampered by the fact that only integrated photometry of the whole bipolar nebula is possible. However, we have luck: the nebula is mainly a reflection nebula. Thus, in analogy with a Chinese lantern: if the flame flickers, the integrated light flickers as well. Therefore, it is still possible to extract from the integrated photometry, important physical characteristics of the variable star, although heavily veiled by dust and gas. The effect of smearing out by reflections in the homunculus is presumably small, see discussion in van Genderen et al. (1999).

  18. Hubble Space Telescope imaging of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Hester, J. J.; Westphal, James A.; Light, Robert M.; Currie, Douglas G.; Groth, Edward J.

    1991-01-01

    New high spatial resolution observations of the material around Eta Carinae, obtained with the Hubble Space Telescope Wide Field/Planetary Camera, are presented. The star Eta Carinae is one of the most massive and luminous stars in the Galaxy, and has been episodically expelling significant quantities of gas over the last few centuries. The morphology of the bright central nebulosity (the homunculus) indicates that it is a thin shell with very well defined edges, and is clumpy on 0.2 arcsec (about 10 to the 16th cm) scales. An extension to the northeast of the star (NN/NS using Walborn's 1976 nomenclature) appears to be a stellar jet and its associated bow shock. The bow shock is notable for an intriguing series of parallel linear features across its face. The S ridge and the W arc appear to be part of a 'cap' of emission located to the SW and behind the star. Together, the NE jet and the SW cap suggest that the symmetry axis for the system runs NE-SW rather than SE-NW, as previously supposed. Overall, the data indicate that the material around the star may represent an oblate shell with polar blowouts, rather than a bipolar flow.

  19. Branching Fraction and P-violation Charge Asymmetry Measurements for B-meson Decays to eta K+-, eta pi+-, eta'K, eta' pi+-, omega K, and omega pi+-

    SciTech Connect

    Aubert, B.

    2007-06-28

    The authors present measurements of the branching fractions for B{sup 0} meson decays to {eta}{prime}K{sup 0} and {omega}K{sup 0}, and of the branching fractions and CP-violation charge asymmetries for B{sup +} meson decays to {eta}{pi}{sup +}, {eta}K{sup +}, {eta}{prime}{pi}{sup +}, {eta}{prime}K{sup +}, {omega}{pi}{sup +}, and {omega}K{sup +}. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 383 million B{bar B} pairs produced in e{sup +}e{sup -} annihilation. The measurements agree with previous results; they find no evidence for direct CP violation.

  20. Chiral corrections to the anomalous 2{gamma} decays of {pi}{sup 0}, {eta} and {eta}{prime}

    SciTech Connect

    Issler, D.

    1990-11-01

    To any order in chiral perturbation theory, the anomalous Wess-Zumino term is shown to generate only chirally invariant counterterms. Explicit examples of 0(p{sub 6}) terms generated by one-loop graphs are given, some of which are relevant to the two-photon decays of {pi}{sup o}, {eta} and {eta}{prime}.

  1. Measurement of Branching Fractions in Radiative BDecays to eta K gamma and Search for B Decays to eta' K gamma

    SciTech Connect

    Aubert, B.

    2006-03-31

    The authors present measurements of the B {yields} {eta}K{gamma} branching fractions and upper limits for the B {yields} {eta}'K{gamma} branching fractions. For B{sup +} {yields} {eta}K{sup +}{gamma} they also measure the time-integrated charge asymmetry. The data sample, collected with the BABAR detector at the Stanford Linear Accelerator Center, represents 232 x 10{sup 6} produced B{bar B} pairs. The results for branching fractions and upper limits at 90% C.L. in units of 10{sup -6} are: {Beta}(B{sup 0} {yields} {eta}K{sup 0}{gamma}) = 11.3{sub -2.6}{sup +2.8} {+-} 0.6, {Beta}(B{sup +} {yields} {eta}K{sup +}{gamma}) = 10.0 {+-} 1.3 {+-} 0.5, {Beta}(B{sup 0} {yields} {eta}'K{sup 0}{gamma}) < 6.6, {Beta}(B{sup +} {yields} {eta}'K{sup +}{gamma}) < 4.2. The charge asymmetry in the decay B{sup +} {yields} {eta}K{sup +}{gamma} is {Alpha}{sub ch} = -0.09 {+-} 0.12 {+-} 0.01. The first errors are statistical and the second systematic.

  2. Static stress triggering explains the empirical aftershock distance decay

    NASA Astrophysics Data System (ADS)

    Hainzl, Sebastian; Moradpour, Javad; Davidsen, Jörn

    2014-12-01

    The shape of the spatial aftershock decay is sensitive to the triggering mechanism and thus particularly useful for discriminating between static and dynamic stress triggering. For California seismicity, it has been recently recognized that its form is more complicated than typically assumed consisting of three different regimes with transitions at the scale of the rupture length and the thickness of the crust. The intermediate distance range is characterized by a relative small decay exponent of 1.35 previously declared to relate to dynamic stress triggering. We perform comprehensive simulations of a simple clock-advance model, in which the number of aftershocks is just proportional to the Coulomb-stress change, to test whether the empirical result can be explained by static stress triggering. Similarly to the observations, the results show three scaling regimes. For simulations adapted to the depths and focal mechanisms observed in California, we find a remarkable agreement with the observation over the whole distance range for a fault distribution with fractal dimension of 1.8, which is shown to be in good agreement with an independent analysis of California seismicity.

  3. Aftershock activity of a M2 earthquake in a deep South African gold mine - spatial distribution and magnitude-frequency relation

    NASA Astrophysics Data System (ADS)

    Naoi, M. M.; Nakatani, M.; Kwiatek, G.; Plenkers, K.; Yabe, Y.

    2009-12-01

    An earthquake of M 2.1 occurred on December 27, 2007 in a deep South African gold mine (Yabe et al., 2008). It occurred within a sensitive high frequency seismic network consisting of eight high frequency AE sensors (up to 200 kHz) and a tri-axial accelerometer (up to 25 kHz). Within 150 hours following the earthquake, our AE network detected more than 20,000 events within 250 m of the center of the network. We have located aftershocks assuming homogeneous medium (Fig. a), based on their manually-picked arrival times of P and S waves. This aftershock seismicity can be clearly separated into five clusters. Each sequence obeyed Omori ‘s law and had the similar p-value (p ~ 1.3). The cluster A in Fig. a is very planar. More than 90 % aftershocks of the cluster are within a 3 m thickness while the cluster has a lateral dimension of ~100m x 100m. The density of aftershocks normal to the planar cluster follows an exponential distribution with about 0.6 m characteristic length. The distribution of the cluster A coincides with one of the nodal planes of the main shock estimated by the waveform inversion. Hence, cluster A is thought to delineate the main rupture. Clusters B to E coincide with the edge of mining cavity or background seismicity recognized before the mainshock. Remarkable off-fault aftershock activities occurred only in these four areas. We have determined moment magnitude (Mw) of 17,350 earthquakes using AE waveforms (Mw > -5.4). As AE sensors have complex frequency characteristics, we use the amplitude in a narrow frequency band (2 - 4 kHz). Directivity of the AE sensor (~20 db) is corrected by comparison with the accelerometer record. Absolute magnitude has been given by an empirical relationship between AE amplitude and Mw determined by the spectral level of the accelerometer record. Mw determination from accelerometer record was done for ~ 0.5 % of aftershocks detected by AE sensors. Moment magnitudes of these selected earthquakes resulted in values

  4. Differential cross sections for the reactions {gamma}p{yields}p{eta} and {gamma}p{yields}p{eta}{sup '}

    SciTech Connect

    Williams, M.; Krahn, Z.; Applegate, D.; Bellis, M.; Meyer, C. A.; Dey, B.; Dickson, R.; McCracken, M. E.; Moriya, K.; Schumacher, R. A.; Adhikari, K. P.; Careccia, S. L.; Dodge, G. E.; Guler, N.; Klein, A.; Mayer, M.; Nepali, C. S.; Niroula, M. R.; Seraydaryan, H.; Tkachenko, S.

    2009-10-15

    High-statistics differential cross sections for the reactions {gamma}p{yields}p{eta} and {gamma}p{yields}p{eta}{sup '} have been measured using the CEBAF large acceptance spectrometer (CLAS) at Jefferson Lab for center-of-mass energies from near threshold up to 2.84 GeV. The {eta}{sup '} results are the most precise to date and provide the largest energy and angular coverage. The {eta} measurements extend the energy range of the world's large-angle results by approximately 300 MeV. These new data, in particular the {eta}{sup '} measurements, are likely to help constrain the analyses being performed to search for new baryon resonance states.

  5. Molecular cloning of the CD3 eta subunit identifies a CD3 zeta-related product in thymus-derived cells.

    PubMed Central

    Jin, Y J; Clayton, L K; Howard, F D; Koyasu, S; Sieh, M; Steinbrich, R; Tarr, G E; Reinherz, E L

    1990-01-01

    The CD3 eta subunit of the T-cell antigen receptor forms a heterodimeric structure with the CD3 zeta subunit in thymus-derived lymphoid cells and is apparently involved in signal transduction through the receptor. Here we report the primary structure of murine CD3 eta as deduced from protein microsequencing and cDNA cloning. The mature protein is divided into three domains: a 9-amino acid extracellular segment, a 21-amino acid transmembrane segment including a negatively charged residue characteristic of CD3 subunits, and a 155-amino acid cytoplasmic tail. The NH2-terminal sequences of CD3 eta and CD3 zeta are identical through amino acid 122 of each mature protein but then diverge in the remainder of their respective COOH-terminal regions, consistent with alternatively spliced products of a common gene. The cytoplasmic domain of CD3 eta is 42 amino acids larger than that of CD3 zeta but lacks one of six potential tyrosine phosphorylation sites as well as a putative nucleotide binding site previously identified in CD3 zeta. These structural features presumably account for the difference between CD3 eta and CD3 zeta function and are consistent with the notion that CD3 eta may be an important component of a T-cell receptor isoform(s) during thymic development. Images PMID:2139725

  6. Detection of a Hot Binary Companion of eta Carinae

    NASA Technical Reports Server (NTRS)

    Sonneborn, G.; Iping, R. C.; Gull, T. R.; Massa, D.; Hillier, D. J.

    2006-01-01

    A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1 180 Angsroms) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Observations were obtained at two epochs of the 2024-day orbit: 2003 June during ingress to the 2003.5 X-ray eclipse and 2004 April several months after egress. These data show that essentially all the far-UV flux from eta Car shortward of Lyman alpha disappeared at least two days before the start of the X-ray eclipse (2003 June 29), implying that the hot companion, eta Car By was also eclipsed by the dense wind or extended atmosphere of eta Car A. Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. N II 1084-1086 emission disappears at the same time as the far-UV continuum, indicating that this feature originates from eta Car B itself or in close proximity to it. The strong N II emission also raises the possibility that the companion star is nitrogen rich. The observed FUV flux levels and spectral features, combined with the timing of their disappearance, are consistent with eta Carinae being a massive binary system.

  7. Detection of a Hot Binary Companion of eta Carinae

    NASA Technical Reports Server (NTRS)

    Sonnebom, G.; Iping, R. C.; Gull, T. R.; Massa, D. L.; Hillier, D. J.

    2006-01-01

    A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1180 A) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. Observations were obtained at two epochs of the 2024-day orbit: 2003 June during ingress to the 2003.5 X-ray eclipse and 2004 April several months after egress. These data show that essentially all the far-UV flux from eta Car shortward of Lyman alpha disappeared at least two days before the start of the X-ray eclipse (2003 June 29), implying that the hot companion, eta Car B, was also eclipsed by the dense wind or extended atmosphere of eta Car A. Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. N II 1084-1086 emission disappears at the same time as the far-UV continuum, indicating that this feature originates from eta Car B itself or in close proximity to it. The strong N II emission also raises the possibility that the companion star is nitrogen rich. The observed FUV flux levels and spectral features, combined with the timing of their disappearance, is consistent with eta Carinae being a massive binary system

  8. Structure and mechanism of human DNA polymerase [eta

    SciTech Connect

    Biertümpfel, Christian; Zhao, Ye; Kondo, Yuji; Ramón-Maiques, Santiago; Gregory, Mark; Lee, Jae Young; Masutani, Chikahide; Lehmann, Alan R.; Hanaoka, Fumio; Yang, Wei

    2010-11-03

    The variant form of the human syndrome xeroderma pigmentosum (XPV) is caused by a deficiency in DNA polymerase {eta} (Pol{eta}), a DNA polymerase that enables replication through ultraviolet-induced pyrimidine dimers. Here we report high-resolution crystal structures of human Pol{eta} at four consecutive steps during DNA synthesis through cis-syn cyclobutane thymine dimers. Pol{eta} acts like a 'molecular splint' to stabilize damaged DNA in a normal B-form conformation. An enlarged active site accommodates the thymine dimer with excellent stereochemistry for two-metal ion catalysis. Two residues conserved among Pol{eta} orthologues form specific hydrogen bonds with the lesion and the incoming nucleotide to assist translesion synthesis. On the basis of the structures, eight Pol{eta} missense mutations causing XPV can be rationalized as undermining the molecular splint or perturbing the active-site alignment. The structures also provide an insight into the role of Pol{eta} in replicating through D loop and DNA fragile sites.

  9. The Rapid Brightening of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Martin, John C.; Davidson, Kris; Mehner, Andrea; Humphreys, Roberta M.

    2016-01-01

    Eta Carinae is one of the most dynamic and well-observed massive stars. Its bipolar Homunculus Nebula and other observations imply it has a strong latitude dependent stellar wind. The significant brightening of the star itself over the last two decades has been commonly explained as an evolution of the latitude structure of the wind , change in mass-loss rate, and/or clearing of circumstellar material in our direct line sight. Hubble Space Telescope images (with a much higher spatial resolution than ground-based images) document an increase in contrast between the brightness of the star and the Homunculus reflection nebula. We present measurements of the nebula's brightness, sampling the changing brightness of the star viewed from angles differing from our own direct line of sight. We also present ultraviolet photometry of the star synthesized from recent HST/STIS observations.

  10. The Use of Explosion Aftershock Probabilities for Planning and Deployment of Seismic Aftershock Monitoring System for an On-site Inspection

    NASA Astrophysics Data System (ADS)

    Labak, P.; Ford, S. R.; Sweeney, J. J.; Smith, A. T.; Spivak, A.

    2011-12-01

    One of four elements of CTBT verification regime is On-site inspection (OSI). Since the sole purpose of an OSI shall be to clarify whether a nuclear weapon test explosion or any other nuclear explosion has been carried out, inspection activities can be conducted and techniques used in order to collect facts to support findings provided in inspection reports. Passive seismological monitoring, realized by the seismic aftershock monitoring (SAMS) is one of the treaty allowed techniques during an OSI. Effective planning and deployment of SAMS during the early stages of an OSI is required due to the nature of possible events recorded and due to the treaty related constrains on size of inspection area, size of inspection team and length of an inspection. A method, which may help in planning the SAMS deployment is presented. An estimate of aftershock activity due to a theoretical underground nuclear explosion is produced using a simple aftershock rate model (Ford and Walter, 2010). The model is developed with data from the Nevada Test Site and Semipalatinsk Test Site, which we take to represent soft- and hard-rock testing environments, respectively. Estimates of expected magnitude and number of aftershocks are calculated using the models for different testing and inspection scenarios. These estimates can help to plan the SAMS deployment for an OSI by giving a probabilistic assessment of potential aftershocks in the Inspection Area (IA). The aftershock assessment combined with an estimate of the background seismicity in the IA and an empirically-derived map of threshold magnitude for the SAMS network could aid the OSI team in reporting. We tested the hard-rock model to a scenario similar to the 2008 Integrated Field Exercise 2008 deployment in Kazakhstan and produce an estimate of possible recorded aftershock activity.

  11. High-resolution relocation of aftershocks of the Mw 7.1 Darfield, New Zealand, earthquake and implications for fault activity

    NASA Astrophysics Data System (ADS)

    Syracuse, E. M.; Thurber, C. H.; Rawles, C. J.; Savage, M. K.; Bannister, S.

    2013-08-01

    Low-slip-rate regions often represent under-recognized hazards, and understanding the progression of seismicity when faults in such areas rupture will help us to better understand earthquake rupture patterns. The 3 September 2010 (UTC) Mw 7.1 Darfield earthquake revealed a formerly unrecognized set of faults in the Canterbury region of New Zealand, an area that had previously been mapped as one of the lower-hazard areas in the country. In this study, we analyze the first four months of its aftershock sequence to identify active faults and temporal changes in seismicity along them. We jointly invert for three-dimensional P wave and S wave velocities and hypocentral locations, using data for 2840 aftershocks recorded at 36 temporary and permanent seismic stations within 70 km of the main shock epicenter. These relocations delineate eight individual faults active prior to the 22 February 2011 Mw 6.3 Christchurch earthquake, the largest aftershock of the Darfield earthquake. Two of these faults are in the Christchurch region, one of which corresponds to geodetically determined rupture planes of the Christchurch earthquake. Using focal mechanisms calculated from first-motion polarities, we find mainly strike-slip faulting events, with some reverse and normal faulting events as well. We compare the orientations of these faults to the prevailing regional stress directions to identify which faults may have been active prior to the Darfield earthquake and which may be newly developed.

  12. A Quantitative Test for the Spatial Relationship Between Aftershock Distributions and Mainshock Rupture Properties

    NASA Astrophysics Data System (ADS)

    Woessner, J.; Ripperger, J.; Mai, M. P.; Wiemer, S.

    2004-12-01

    Correlating the properties of the mainshock rupture with the location of corresponding aftershocks may provide insight into the relationship between mainshock-induced static stress changes and aftershock occurrence. In this study, we develop a rigorous statistical test to quantify the spatial pattern of aftershock locations with the corresponding distributions of coseismic slip and stress-drop. Well-located aftershock hypocenters are projected onto the mainshock fault plane and coseismic slip and stress drop values are interpolated to their respective location. The null hypothesis H0 for the applied test statistic is: Aftershock hypocenters are randomly distributed on the mainshock fault plane and are not correlated with mainshock properties. Because we want to maintain spatial earthquake clustering as one of the important observed features of seismicity, we synthesize slip distributions using a random spatial field model from which we then compute the respective stress-drop distributions. For each simulation of earthquake slip, we compute the test statistic for the slip and stress-drop distribution, testing whether or not an apparent correlation between mainshock properties and aftershock locations exists. Uncertainties in the aftershock locations are accounted for by simulating a thousand catalogues for which we randomize the location of the aftershocks within their given location error bounds. We then determine the number of aftershocks in low-slip or negative stress-drop regions for simulated slip distributions, and compare those to the measurements obtained for finite-source slip inversions. We apply the test to crustal earthquakes in California and Japan. If possible, we use different source models and earthquake catalogues with varying accuracy to investigate the dependence of the test results on, for example, the location uncertainties of aftershocks. Contrary to the visual impression, we find that for some strike-slip earthquakes or segments of the

  13. Maximal radius of the aftershock zone in earthquake networks

    NASA Astrophysics Data System (ADS)

    Mezentsev, A. Yu.; Hayakawa, M.

    2009-09-01

    In this paper, several seismoactive regions were investigated (Japan, Southern California and two tectonically distinct Japanese subregions) and structural seismic constants were estimated for each region. Using the method for seismic clustering detection proposed by Baiesi and Paczuski [M. Baiesi, M. Paczuski, Phys. Rev. E 69 (2004) 066106; M. Baiesi, M. Paczuski, Nonlin. Proc. Geophys. (2005) 1607-7946], we obtained the equation of the aftershock zone (AZ). It was shown that the consideration of a finite velocity of seismic signal leads to the natural appearance of maximal possible radius of the AZ. We obtained the equation of maximal radius of the AZ as a function of the magnitude of the main event and estimated its values for each region.

  14. Cataloging the 1811-1812 New Madrid, central U.S., earthquake sequence

    USGS Publications Warehouse

    Hough, S.E.

    2009-01-01

    The three principal New Madrid, central U.S., mainshocks of 1811-1812 were followed by extensive aftershock sequences that included numerous felt events. Although no instrumental data are available for the sequence, historical accounts provide information that can be used to estimate magnitudes and locations for the large aftershocks as well as the mainshocks. Several detailed eyewitness accounts of the sequence provide sufficient information to identify times and rough magnitude estimates for a number of aftershocks that have not been analyzed previously. I also use three extended compilations of felt events to explore the overall sequence productivity. Although one generally cannot estimate magnitudes or locations for individual events, the intensity distributions of recent, instrumentally recorded earthquakes in the region provide a basis for estimation of the magnitude distribution of 1811-1812 aftershocks. The distribution is consistent with a b-value distribution. I estimate Mw 6-6.3 for the three largest identifiable aftershocks, apart from the so-called dawn aftershock on 16 December 1811.

  15. Investigation of the high-frequency attenuation parameter, κ (kappa), from aftershocks of the 2010 Mw 8.8 Maule, Chile earthquake

    USGS Publications Warehouse

    Neighbors, Corrie; Liao, E. J.; Cochran, Elizabeth S.; Funning, G. J.; Chung, A. I.; Lawrence, J. F.; Christensen, C. M.; Miller, M.; Belmonte, A.; Sepulveda, H. H. Andrés

    2014-01-01

    The Bío Bío region of Chile experienced a vigorous aftershock sequence following the 2010 February 27 Mw 8.8 Maule earthquake. The immediate aftershock sequence was captured by two temporary seismic deployments: the Quake Catcher Network Rapid Aftershock Mobilization Program (QCN RAMP) and the Incorporated Research Institutions for Seismology CHile Aftershock Mobilization Program (IRIS CHAMP). Here, we use moderate to large aftershocks (ML ≥ 4.0) occurring between 2010 March 1 and June 30 recorded by QCN RAMP and IRIS CHAMP stations to determine the spectral decay parameter, kappa (κ). First, we compare waveforms and κ estimates from the lower-resolution QCN stations to the IRIS CHAMP stations to ensure the QCN data are of sufficient quality. We find that QCN stations provide reasonable estimates of κ in comparison to traditional seismic sensors and provide valuable additional observations of local ground motion variation. Using data from both deployments, we investigate the variation in κ for the region to determine if κ is influenced primarily by local geological structure, path attenuation, or source properties (e.g. magnitude, mechanism and depth). Estimates of κ for the Bío Bío region range from 0.0022 to 0.0704 s with a mean of 0.0295 s and are in good agreement with κ values previously reported for similar tectonic environments. κ correlates with epicentral distance and, to a lesser degree, with source magnitude. We find little to no correlation between the site kappa, κ0, and mapped geology, although we were only able to compare the data to a low-resolution map of surficial geology. These results support an increasing number of studies that suggest κobservations can be attributed to a combination of source, path and site properties; additionally, measured κ are often highly scattered making it difficult to separate the contribution from each of these factors. Thus, our results suggest that contributions from the site

  16. Minute Temperature Fluctuations Detected in Eta Bootis

    NASA Astrophysics Data System (ADS)

    1994-11-01

    A group of astronomers from the Aarhus University (Denmark) and the European Southern Observatory (2) have for the first time succeeded in detecting solar-type oscillations in another star. They observed the temperature of the bright northern star Eta Bootis during six nights with the 2.5-metre Nordic Optical Telescope at the Roque de los Muchachos observatory on the island of La Palma (Canary Islands) and were able to show that it varies periodically by a few hundredths of a degree. These changes are caused by pressure waves in the star and are directly dependent on its inner structure. A detailed analysis by the astronomers has shown that the observed effects are in good agreement with current stellar models. This is a most important, independent test of stellar theory. The Sun is an Oscillating Star About twenty years ago, it was discovered that the nearest star, our Sun, oscillates like the ringing of a bell with a period of about 5 minutes. The same phenomenon is known in the Earth, which begins to vibrate after earthquakes; in this way seismologists have been able to discern a layered structure in the Earth's interior. The recent impacts of a comet on Jupiter most likely had a similar effect on that planet. The observed solar oscillations concern the entire gaseous body of the Sun, but we can of course only observe them on its surface. It has been found that each mode moves the surface up and down by less than 25 metres; the combined motion is very complicated, because there are many different, simultaneous modes, each of which has a slightly different period. The exact values of these periods are sensitive to the speed of sound in the Sun's interior, which in turn depends on the density of the material there. Thus, by measuring the periods of solar oscillations, we may probe the internal structure of the Sun, that is otherwise inaccessible to observations. Why does the Sun oscillate and what is the cause of these oscillations ? We do not know yet, but it is

  17. Seismotectonic framework of the 2010 February 27 Mw 8.8 Maule, Chile earthquake sequence

    USGS Publications Warehouse

    Hayes, Gavin P.; Bergman, Eric; Johnson, Kendra J.; Benz, Harley M.; Brown, Lucy; Meltzer, Anne S.

    2013-01-01

    After the 2010 Mw 8.8 Maule earthquake, an international collaboration involving teams and instruments from Chile, the US, the UK, France and Germany established the International Maule Aftershock Deployment temporary network over the source region of the event to facilitate detailed, open-access studies of the aftershock sequence. Using data from the first 9-months of this deployment, we have analyzed the detailed spatial distribution of over 2500 well-recorded aftershocks. All earthquakes have been relocated using a hypocentral decomposition algorithm to study the details of and uncertainties in both their relative and absolute locations. We have computed regional moment tensor solutions for the largest of these events to produce a catalogue of 465 mechanisms, and have used all of these data to study the spatial distribution of the aftershock sequence with respect to the Chilean megathrust. We refine models of co-seismic slip distribution of the Maule earthquake, and show how small changes in fault geometries assumed in teleseismic finite fault modelling significantly improve fits to regional GPS data, implying that the accuracy of rapid teleseismic fault models can be substantially improved by consideration of existing fault geometry model databases. We interpret all of these data in an integrated seismotectonic framework for the Maule earthquake rupture and its aftershock sequence, and discuss the relationships between co-seismic rupture and aftershock distributions. While the majority of aftershocks are interplate thrust events located away from regions of maximum co-seismic slip, interesting clusters of aftershocks are identified in the lower plate at both ends of the main shock rupture, implying internal deformation of the slab in response to large slip on the plate boundary interface. We also perform Coulomb stress transfer calculations to compare aftershock locations and mechanisms to static stress changes following the Maule rupture. Without the

  18. Eta Meson Production in Proton-Proton and Nuclear Collisions

    NASA Technical Reports Server (NTRS)

    Norbury, John W.; Dick, Frank

    2008-01-01

    Total cross sections for eta meson production in proton - proton collisions are calculated. The eta meson is mainly produced via decay of the excited nucleon resonance at 1535 MeV. A scalar quantum field theory is used to calculate cross sections, which also include resonance decay. Comparison between theory and experiment is problematic near threshold when resonance decay is not included. When the decay is included, the comparison between theory and experiment is much better.

  19. Analysis of Mw 7.2 2014 Molucca Sea earthquake and its aftershocks

    NASA Astrophysics Data System (ADS)

    Shiddiqi, Hasbi Ash; Widiyantoro, Sri; Nugraha, Andri Dian; Ramdhan, Mohamad; Wiyono, Samsul Hadi; Wandono, Wandono

    2016-05-01

    A Mw 7.2 earthquake struck an area in the Molucca Sea region on November 15, 2014, and was followed by more than 300 aftershocks until the end of December 2014. This earthquake was the second largest event in the Molucca Sea during the last decade and was well recorded by local networks. Although the seismicity rate of the aftershocks was declining at the end of 2014, several significant earthquakes with magnitude (Mw) larger than five still occurred from January to May 2015 within the vicinity of the mainshock location. In this study, we investigated the earthquake process and its relation to the increasing seismicity in the Molucca Sea within six months after the earthquake. We utilized teleseismic double-difference hypocenter relocation method using local, regional, and teleseismic direct body-wave arrival times of 514 earthquakes from the time of mainshock occurrence to May 2015. Furthermore, we analyzed the focal mechanism solutions from the National Research Institute for Earth Science and Disaster Prevention (NIED), Japan. From our results, we observed that aftershocks propagated along the NNE-SSW direction within a 100 km fault segment length of the Mayu Ridge. The highest number of the aftershocks was located in the SSW direction of the main event. The aftershocks were terminated at around 60 km depth, which may represent the location of the top of the Molucca Sea Plate (MSP). Between January and May 2015, several significant earthquakes propagated westward and were extended to the Molucca Sea slab. From focal mechanism catalog, we found that the mainshock mechanism was reverse with strike 192o and dip 55o. While most of the large aftershock mechanisms were consistent with the main event, several aftershocks had reverse, oblique mechanisms. Stress inversion result from focal mechanism data revealed that the maximum stress direction was SE and was not perpendicular with fault direction. We suggest that the non-perpendicular maximum stress caused several

  20. Correlating Aftershock Hypocenters With On-fault Main Shock Properties: Introducing Non-standard Statistical Tests

    NASA Astrophysics Data System (ADS)

    Woessner, J.; Schorlemmer, D.; Wiemer, S.; Mai, P. M.

    2005-12-01

    Quantitatively correlating properties of finite-fault source models with hypocenters of aftershocks may provide new insight in the relationship between either slip or static stress change distributions and aftershock occurrence. We present advanced non-standard statistical test approaches to evaluate the test hypotheses (1) if aftershocks are preferentially located in areas of low slip and (2) if aftershocks are located in increased shear stress against the null hypothesis: aftershocks are located randomly on the fault plane. By using multiple test approaches, we investigate possible pitfalls and the information content of statistical testing. To perform the tests, we use earthquakes for which multiple finite-fault source models and earthquake catalogs of varying accuracy exist. The aftershock hypocenters are projected onto the main-shock rupture plane and uncertainties are accounted for by simulating hypocenter locations in the given error bounds. For the statistical tests, we retain the spatial clustering of earthquakes as the most important observed features of seismicity and synthesize random slip distributions with different approaches: first, using standard statistical methods that randomize the obtained finite-fault source model values and second, using a random spatial field model. We then determine the number of aftershocks in low-slip or increased shear-stress regions for simulated slip distributions, and compare those to the measurements obtained for finite-source slip inversions. We apply the tests to prominent earthquakes in California and Japan and find statistical significant evidence that aftershocks are preferentially located in low-slip regions. The tests, however, show a lower significance for the correlation with the shear-stress distribution, but are in general agreement with the expectations of the asperity model. Tests using the hypocenters of relocated catalogs show higher significances.

  1. An Explosion Aftershock Model with Application to On-Site Inspection

    NASA Astrophysics Data System (ADS)

    Ford, Sean R.; Labak, Peter

    2016-01-01

    An estimate of aftershock activity due to a theoretical underground nuclear explosion is produced using an aftershock rate model. The model is developed with data from the Nevada National Security Site, formerly known as the Nevada Test Site, and the Semipalatinsk Test Site, which we take to represent soft-rock and hard-rock testing environments, respectively. Estimates of expected magnitude and number of aftershocks are calculated using the models for different testing and inspection scenarios. These estimates can help inform the Seismic Aftershock Monitoring System (SAMS) deployment in a potential Comprehensive Test Ban Treaty On-Site Inspection (OSI), by giving the OSI team a probabilistic assessment of potential aftershocks in the Inspection Area (IA). The aftershock assessment, combined with an estimate of the background seismicity in the IA and an empirically derived map of threshold magnitude for the SAMS network, could aid the OSI team in reporting. We apply the hard-rock model to a M5 event and combine it with the very sensitive detection threshold for OSI sensors to show that tens of events per day are expected up to a month after an explosion measured several kilometers away.

  2. Analysis of UV-induced mutation spectra in Escherichia coli by DNA polymerase eta from Arabidopsis thaliana.

    PubMed

    Santiago, María Jesús; Alejandre-Durán, Encarna; Ruiz-Rubio, Manuel

    2006-10-10

    DNA polymerase eta belongs to the Y-family of DNA polymerases, enzymes that are able to synthesize past template lesions that block replication fork progression. This polymerase accurately bypasses UV-associated cis-syn cyclobutane thymine dimers in vitro and therefore may contributes to resistance against sunlight in vivo, both ameliorating survival and decreasing the level of mutagenesis. We cloned and sequenced a cDNA from Arabidopsis thaliana which encodes a protein containing several sequence motifs characteristics of Pol eta homologues, including a highly conserved sequence reported to be present in the active site of the Y-family DNA polymerases. The gene, named AtPOLH, contains 14 exons and 13 introns and is expressed in different plant tissues. A strain from Saccharomyces cerevisiae, deficient in Pol eta activity, was transformed with a yeast expression plasmid containing the AtPOLH cDNA. The rate of survival to UV irradiation in the transformed mutant increased to similar values of the wild type yeast strain, showing that AtPOLH encodes a functional protein. In addition, when AtPOLH is expressed in Escherichia coli, a change in the mutational spectra is detected when bacteria are irradiated with UV light. This observation might indicate that AtPOLH could compete with DNA polymerase V and then bypass cyclobutane pyrimidine dimers incorporating two adenylates.

  3. Aftershock and induced seismic activity of the 2011 off the Pacific coast of Tohoku Earthquake in the northern part of Tohoku district, NE Japan

    NASA Astrophysics Data System (ADS)

    Kosuga, M.; Watanabe, K.

    2011-12-01

    We investigated the seismic activity around the northern neighbor of the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0) with special attention to a potential large aftershock in the area. We obtained a combined data set by adding our manually-picked locations to the catalog locations by the Japan Meteorological Agency. The hypocenter distribution delineates active and inactive bands of seismicity. The band of low seismicity corresponds to a zone of a large seismic slip, indicating that aftershocks occurred in peripheral neighbors of the mainshock asperity. The broad band of active seismicity along the coast corresponds to the zone of a large postseismic slip, suggesting the enhancement of the aftershock activity by the slip. Although the northern neighbor of the mainshock fault is a favored region of increased seismicity, as shown from a Coulomb stress calculation, no significant seismic activity is observed within the potential source area except along the Japan Trench and the SW corner. This implies that the zone of interplate moment release by previous large earthquakes and the subsequent slow slip acted as a barrier to the migration of both the mainshock rupture and aftershock activity. However, an aftershock area in the zone may reflect inhomogeneous moment release by past seismic and aseismic sequences. Induced inland seismicity is quite high in the Akita Prefecture on the Japan Sea side apart more than 100 km from the mainshock fault. There are some active clusters including moderate earthquakes with magnitude greater than 5. They are newly formed clusters after the mainshock, while the seismicity of previously active areas decreased significantly. Focal mechanism solutions of earthquakes in the new clusters show the types of strike-slip with consistently NW-SE trending T-axes. The predominant type of focal mechanisms in the Akita area before the mainshock was E-W compressional reverse faulting. Thus the stress field in the area has changed

  4. A detailed study of the Pernik (Bulgaria) seismic sequence of 2012

    NASA Astrophysics Data System (ADS)

    Raykova, Plamena; Solakov, Dimcho; Simeonova, Stela; Dimitrova, Liliya

    2014-05-01

    A detailed study of the Pernik (Bulgaria) seismic sequence of 2012 D.Solakov, S.Simeonova ,I. Georgiev, P.Raykova, L.Dimitrova and V.Protopopova National Institute of Geophysics, Geodesy and Geography-BAS, Sofia, Bulgaria The spatial and temporal clustering of aftershocks is the dominant non-random element of seismicity, so that when aftershocks are removed, the remaining activity can be modelled (as first approximation) as a Poisson process. The properties of aftershock sequences (distinct cluster, for example; even aftershocks can have aftershocks) allow time-dependent prediction of aftershock probabilities. Consideration of recent earthquake sequences suggests that aftershocks to large earthquakes although they are still, by definition, smaller events, can be very damaging and should be addressed in emergence planning scenarios. Because of the factors such as location and radiation pattern and the cumulative nature of building damage, aftershocks can cause more damage than the main shock. An earthquake of moment magnitude 5.6 hit Sofia seismic zone, on May 22nd, 2012. The earthquake occurred in the vicinity of Pernik city, at about 25 km south west of the city of Sofia (the capital of Bulgaria). The event was followed by intensive activity. The active area is situated in the central part of western Bulgaria. That is the most populated (more than 1.2 mil. inhabitants), industrial and cultural region of Bulgaria. Seismicity in the zone is related to the marginal neotectonic faults of Sofia graben. The boundaries of the graben are represented by SE-NW fault system with expressive neotectonic activity. This zone is characterized by shallow earthquakes. The strongest known event in the region is the 1858 quake with intensity I0=9-10 MSK. The 1858 earthquake caused heavy destruction in the city of Sofia and the appearance of thermal spring. It is worth mentioning that the seismic sequence of May 2912 occurred in an area characterized by a long quiescence (of 95 years

  5. Aftershock Records in the Kathmandu Valley of the 2015 Gorkha, Nepal, Earthquake

    NASA Astrophysics Data System (ADS)

    Shigefuji, M.; Takai, N.; Sasatani, T.; Bijukchhen, S.; Ichiyanagi, M.; Rajaure, S.; Dhital, M. R.

    2015-12-01

    The devastating earthquake, named the Gorkha Earthquake, was followed by a series of aftershocks: more than 350 of them greater than M 4 and four aftershock greater than M 6. The rupture of main shock originating 80 km NW of capital Kathmandu propagated towards east. The ensuing aftershock activities are concentrated in the eastern part of the rupture area. The aftershock of Mw 6.6 occurred about half an hour later at epicentre near to that of the main shock. The other three large aftershocks however, were originated in the eastern extreme of the rupture zone. The aftershock of Mw 7.3 that occurred on 12th May 2015 brought about more damages to infrastructures already vulnerable due to the main shock. To understand the site effect of the Kathmandu valley structure, we installed continuous recording accelerometers in four different parts of the valley. Four stations were installed along a west-to-east profile of the valley at KTP (Kirtipur; hill top), TVU (Kirtipur; hill side), PTN (Patan) and THM (Thimi). The surface S-wave velocity of the KTP site was over 700 cm s-1, but for each of the other three sites it was less than 200 cm s-1. These velocities are consistent with the geological formations; KTP is above hard rock, and TVU, PTN and THM are over the lake sediment of the valley. It is normal for the amplitude of earthquake motion to be larger in areas lying above sedimentary soil than in areas above hard rock, and these motions can be amplified further by certain deep underground structures. To know deep underground structure using with aftershock records, we installed more four instruments in the Kathmandu basin after main shock. We analysed the strong-motion data of these five aftershocks recorded in the eight strong-motion accelerometers. The station of KTP is considered as reference site to compare the effect of sediments on the earthquake waves. The large aftershocks all have highest Peak Ground Velocity (PGV) at TVU and the station of KTP showed the least

  6. Propagation of Coulomb stress uncertainties in physics-based aftershock models

    NASA Astrophysics Data System (ADS)

    Cattania, Camilla; Hainzl, Sebastian; Wang, Lifeng; Roth, Frank; Enescu, Bogdan

    2014-10-01

    Stress transfer between earthquakes is recognized as a fundamental mechanism governing aftershock sequences. A common approach to relate stress changes to seismicity rate changes is the rate-and-state constitutive law developed by Dieterich: these elements are the foundation of Coulomb-rate-and-state (CRS) models. Despite the successes of Coulomb hypothesis and of the rate-and-state formulation, such models perform worse than statistical models in an operational forecasting context: one reason is that Coulomb stress is subject to large uncertainties and intrinsic spatial heterogeneity. In this study, we characterize the uncertainties in Coulomb stress inherited from different physical quantities and assess their effect on CRS models. We use a Monte Carlo method and focus on the following aspects: the existence of multiple receiver faults; the stress heterogeneity within grid cells, due to their finite size; and errors inherited from the coseismic slip model. We study two well-recorded sequences from different tectonic settings: the Mw = 6.0 Parkfield and the Mw= 9.0 Tohoku earthquakes. We find that the existence of multiple receiver faults is the most important source of intrinsic stress heterogeneity, and CRS models perform significantly better when this variability is taken into account. The choice of slip model also generates large uncertainties. We construct an ensemble model based on published slip models and find that it outperforms individual models. Our findings highlight the importance of identifying sources of errors and quantifying confidence boundaries in the forecasts; moreover, we demonstrate that consideration of stress heterogeneity and epistemic uncertainty has the potential to improve the performance of operational forecasting models.

  7. Seismotectonics of the April-May 2015 Nepal earthquakes: An assessment based on the aftershock patterns, surface effects and deformational characteristics

    NASA Astrophysics Data System (ADS)

    Parameswaran, Revathy M.; Natarajan, Thulasiraman; Rajendran, Kusala; Rajendran, C. P.; Mallick, Rishav; Wood, Matthew; Lekhak, Harish C.

    2015-11-01

    Occurrence of the April 25, 2015 (Mw 7.8) earthquake near Gorkha, central Nepal, and another one that followed on May 12 (Mw 7.3), located ∼140 km to its east, provides an exceptional opportunity to understand some new facets of Himalayan earthquakes. Here we attempt to assess the seismotectonics of these earthquakes based on the deformational field generated by these events, along with the spatial and temporal characteristics of their aftershocks. When integrated with some of the post-earthquake field observations, including the localization of damage and surface deformation, it became obvious that although the mainshock slip was mostly limited to the Main Himalayan Thrust (MHT), the rupture did not propagate to the Main Frontal Thrust (MFT). Field evidence, supported by the available InSAR imagery of the deformation field, suggests that a component of slip could have emerged through a previously identified out-of-sequence thrust/active thrust in the region that parallels the Main Central Thrust (MCT), known in the literature as a co-linear physiographic transitional zone called PT2. Termination of the first rupture, triggering of the second large earthquake, and distribution of aftershocks are also spatially constrained by the eastern extremity of PT2. Mechanism of the 2015 sequence demonstrates that the out-of-sequence thrusts may accommodate part of the slip, an aspect that needs to be considered in the current understanding of the mechanism of earthquakes originating on the MHT.

  8. Indications for the decays D/sub s//sup +-/. -->. eta. pi. /sup +-/ and D/sub s//sup +-/. -->. eta'. pi. /sup +-/

    SciTech Connect

    Wormser, G.

    1987-11-01

    A search for D/sub s//sup +-/ decays into eta ..pi../sup +-/ and eta' ..pi../sup +-/ has been performed by the MarkII collaboration at the PEP e/sup +/e/sup -/ storage ring. Eta particles are reconstructed by their ..gamma gamma.. decay mode. The eta fragmentation has been measured and found to be in good agreement with the Lund model prediction. Eta' production has been measured for the first time in e/sup +/e/sup -/ high energy annihilation. Good indications are found for both decay modes D/sub s//sup +-/ ..-->.. eta ..pi../sup +-/ and D/sub s//sup +-/ ..-->.. eta' ..pi../sup +-/.

  9. Spectral scaling of the aftershocks of the Tocopilla 2007 earthquake in northern Chile

    NASA Astrophysics Data System (ADS)

    Lancieri, M.; Madariaga, R.; Bonilla, F.

    2012-04-01

    We study the scaling of spectral properties of a set of 68 aftershocks of the 2007 November 14 Tocopilla (M 7.8) earthquake in northern Chile. These are all subduction events with similar reverse faulting focal mechanism that were recorded by a homogenous network of continuously recording strong motion instruments. The seismic moment and the corner frequency are obtained assuming that the aftershocks satisfy an inverse omega-square spectral decay; radiated energy is computed integrating the square velocity spectrum corrected for attenuation at high frequencies and for the finite bandwidth effect. Using a graphical approach, we test the scaling of seismic spectrum, and the scale invariance of the apparent stress drop with the earthquake size. To test whether the Tocopilla aftershocks scale with a single parameter, we introduce a non-dimensional number, ?, that should be constant if earthquakes are self-similar. For the Tocopilla aftershocks, Cr varies by a factor of 2. More interestingly, Cr for the aftershocks is close to 2, the value that is expected for events that are approximately modelled by a circular crack. Thus, in spite of obvious differences in waveforms, the aftershocks of the Tocopilla earthquake are self-similar. The main shock is different because its records contain large near-field waves. Finally, we investigate the scaling of energy release rate, Gc, with the slip. We estimated Gc from our previous estimates of the source parameters, assuming a simple circular crack model. We find that Gc values scale with the slip, and are in good agreement with those found by Abercrombie and Rice for the Northridge aftershocks.

  10. Searching for Radial Velocity Variations in eta Carinae

    NASA Technical Reports Server (NTRS)

    Iping, R. C.; Sonneborn, G.; Gull, T. R.; Ivarsson, S.; Nielsen, K.

    2006-01-01

    A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1180 A) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite (see poster by Sonneborn et al.). Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. The N II 1084-86 emission feature indicates that the star may be nitrogen rich. The FUV continuum and the S IV 1073 P-Cygni wind line suggest that the effective temperature of eta Car B is at least 25,000 K. FUV spectra of eta Carinae were obtained with the FUSE satellite at 9 epochs between 2000 February and 2005 July. The data consists of 12 observations taken with the LWRS aperture (30x30 arcsec), three with the HIRS aperture (1.25x20 arcsec), and one MRDS aperture (4x20 arcsec). In this paper we discuss the analysis of these spectra to search for radial velocity variations associated with the 5.54-year binary orbit of Eta Car AB.

  11. Foreshocks and aftershocks locations of the 2014 Pisagua, N. Chile earthquake: history of a megathrust earthquake nucleation

    NASA Astrophysics Data System (ADS)

    Fuenzalida Velasco, Amaya; Rietbrock, Andreas; Tavera, Hernando; Ryder, Isabelle; Ruiz, Sergio; Thomas, Reece; De Angelis, Silvio; Bondoux, Francis

    2015-04-01

    The April 2014 Mw 8.1 Pisagua earthquake occurred in the Northern Chile seismic gap: a region of the South American subduction zone lying between Arica city and the Mejillones Peninsula. It is believed that this part of the subduction zone has not experienced a large earthquake since 1877. Thanks to the identification of this seismic gap, the north of Chile was well instrumented before the Pisagua earthquake, including the Integrated Plate boundary Observatory Chile (IPOC) network and the Chilean local network installed by the Centro Sismologico Nacional (CSN). These instruments were able to record the full foreshock and aftershock sequences, allowing a unique opportunity to study the nucleation process of large megathrust earthquakes. To improve azimuthal coverage of the Pisagua seismic sequence, after the earthquake, in collaboration with the Instituto Geofisico del Peru (IGP) we installed a temporary seismic network in south of Peru. The network comprised 12 short-period stations located in the coastal area between Moquegua and Tacna and they were operative from 1st May 2014. We also installed three stations on the slopes of the Ticsiani volcano to monitor any possible change in volcanic activity following the Pisagua earthquake. In this work we analysed the continuous seismic data recorded by CSN and IPOC networks from 1 March to 30 June to obtain the catalogue of the sequence, including foreshocks and aftershocks. Using an automatic algorithm based in STA/LTA we obtained the picks for P and S waves. Association in time and space defined the events and computed an initial location using Hypo71 and the 1D local velocity model. More than 11,000 events were identified with this method for the whole period, but we selected the best resolved events that include more than 7 observed arrivals with at least 2 S picks of them, to relocate these events using NonLinLoc software. For the main events of the sequence we carefully estimate event locations and we obtained

  12. On the origin of diverse aftershock mechanisms following the 1989 Loma Prieta earthquake

    USGS Publications Warehouse

    Kilb, Debi; Ellis, M.; Gomberg, J.; Davis, S.

    1997-01-01

    We test the hypothesis that the origin of the diverse suite of aftershock mechanisms following the 1989 M 7.1 Loma Prieta, California, earthquake is related to the post-main-shock static stress field. We use a 3-D boundary-element algorithm to calculate static stresses, combined with a Coulomb failure criterion to calculate conjugate failure planes at aftershock locations. The post-main-shock static stress field is taken as the sum of a pre-existing stress field and changes in stress due to the heterogeneous slip across the Loma Prieta rupture plane. The background stress field is assumed to be either a simple shear parallel to the regional trend of the San Andreas fault or approximately fault-normal compression. A suite of synthetic aftershock mechanisms from the conjugate failure planes is generated and quantitatively compared (allowing for uncertainties in both mechanism parameters and earthquake locations) to well-constrained mechanisms reported in the US Geological Survey Northern California Seismic Network catalogue. We also compare calculated rakes with those observed by resolving the calculated stress tensor onto observed focal mechanism nodal planes, assuming either plane to be a likely rupture plane. Various permutations of the assumed background stress field, frictional coefficients of aftershock fault planes, methods of comparisons, etc. explain between 52 and 92 per cent of the aftershock mechanisms. We can explain a similar proportion of mechanisms however by comparing a randomly reordered catalogue with the various suites of synthetic aftershocks. The inability to duplicate aftershock mechanisms reliably on a one-to-one basis is probably a function of the combined uncertainties in models of main-shock slip distribution, the background stress field, and aftershock locations. In particular we show theoretically that any specific main-shock slip distribution and a reasonable background stress field are able to generate a highly variable suite of failure

  13. Is the Ejecta of ETA Carinae Overabundant or Overexcited

    NASA Technical Reports Server (NTRS)

    Gull, Theodore; Davidson, Kris; Johansson, Sveneric; Damineli, Augusto; Ishibashi, Kaxunori; Corcoran, Michael; Hartman, Henrick; Viera, Gladys; Nielsen, Krister

    2003-01-01

    The ejecta of Eta Carinae, revealed by HST/STIS, are in a large range of physical conditions. As Eta Carinae undergoes a 5.52 period, changes occur in nebular emission and nebular absorption. "Warm" neutral regions, partially ionized regions, and fully ionized regions undergo significant changes. Over 2000 emission lines, most of Fe-like elements, have been indentified in the Weigelt blobs B and D. Over 500 emission lines have been indentified in the Strontium Filament. An ionized Little Homunculus is nestled within the neutral-shelled Homunculus. In line of sight, over 500 nebular absorption lines have been identified with up to twenty velocity components. STIS is following changes in many nebular emission and absorption lines as Eta Carinae approaches the minimum, predicted to be in June/July 2003, during the General Assembly. Coordinated observations with HST, CHANDRA, RXTE, FUSE, UVES/VLT, Gemini and other observatories are following this minimum.

  14. Excited Ejecta in Light of Sight from Eta Car

    NASA Technical Reports Server (NTRS)

    Vieira, G.; Gull, T. R.; Danks, A.

    2003-01-01

    In the NUV spectrum of Eta Car, we have resolved many narrow absorption lines of neutral and singly-ionized elements with the Space Telescope Imaging Spectrograph. We report for the first time the detection of interstellar vanadium in absorption, and many highly-excited absorption lines of Fe, Cr, Ti, Ni, Co, Mn, and Mg. These elements, normally tied up in dust grains in the ISM, are located within wall of the Homunculus within 20,000 A.U. of Eta Car. Stellar radiation and stellar wind are interacting with the wall. Dust is likely being modified and/or destroyed. Previous Homunculus studies have demonstrated that nitrogen is overabundant and that carbon and oxygen emission lines are weak, or non-existent. Are the large column densities of these heavy elements due to abundance effects, excitation mechanisms, or modified grains? We may gain insight as Eta Car goes through its spectroscopic minimum in the summer of 2003.

  15. The southeastern Illinois earthquake of 10 June 1987: the later aftershocks

    USGS Publications Warehouse

    Langer, C.J.; Bollinger, G.A.

    1991-01-01

    The 10 June 1987 southeastern Illinois earthquake (mbLg=5.2) was located about 200 km east of St Louis, Missouri, caused minor damage in the epicentral area, had a contiguous felt area of about 433 000 km2, and had a total felt area over 1 million km2. Within 47 hours after the main shock, a 15-station aftershock monitoring network (later expanded to 21 instruments) was installed that recorded more than 100 aftershocks in the folllowing 4-day period. Results from the 56 aftershocks that were well located indicate a compact, cylindrically shaped aftershock volume about 1.7 km long, 0.8 km wide, and with a vertical distribution between about 9 and 12 km in depth. Composite focal mechanism solutions of the aftershocks suggest that the predominant mode of faulting is reverse slip, but some strike-slip type motion occurred similar to the mechanism for the main shock as determined from teleseismic data. The maximum principal compressive stress (P axes) is oriented E-ESE and is subhorizontal in plunge. -from Authors

  16. Thrust-faulting earthquake induced many normal-faulting aftershocks, in northeastern Chiba Prefecture, Japan

    NASA Astrophysics Data System (ADS)

    Sakai, S.; Kato, A.; Hirata, N.; Nakagawa, S.; Kasahara, K.; Sato, H.; Kurashimo, E.; Nanjo, K.; Panayotopoulos, Y.; Obara, K.; Aketagawa, T.; Kimura, H.

    2010-12-01

    A thrust faulting type earthquake of a local body wave magnitude (MJMA) of 4.9 occurred near the upper interface of the subducting Philippine Sea Plate (PHS) in northeastern Chiba Prefecture on July 22, 2010. We have been developing a dense seismic net work call the MeSO-net in the Tokyo Metropolitan area. So far, 249 stations are available for the study of a large felt earthquakes and small event as low as M=1.5. We also deployed a temporary seismic array 24 of which were used for the analysis of the aftershocks. We locate the July 22 earthquake(MJMA=4.9) and its 19 aftershocks (M>1.5) by the double difference location algorithm. We also determine focal mechanisms for the main- and after-shocks. The locations of the main shock and three aftershocks are closely distributed near the upper interface of PHS, which is consistent with the idea that the event occurred on the plate interface. However, most aftershocks whose focal mechanism is normal-fault type with a T-axis directing NE-SW are located off the upper interface indicating that intra-slab events are also generated by the event. Acknowledgement: The present study is supported by Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.

  17. Decay of aftershock density with distance does not indicate triggering by dynamic stress

    USGS Publications Warehouse

    Richards-Dinger, K.; Stein, R.S.; Toda, S.

    2010-01-01

    Resolving whether static or dynamic stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard. Felzer and Brodsky examined the distance distribution of earthquakes occurring in the first five minutes after 2 ≤ M  M  M ≥ 2 aftershocks showed a uniform power-law decay with slope −1.35 out to 50 km from the mainshocks. From this they argued that the distance decay could be explained only by dynamic triggering. Here we propose an alternative explanation for the decay, and subject their hypothesis to a series of tests, none of which it passes. At distances more than 300 m from the 2 ≤  M< 3 mainshocks, the seismicity decay 5 min before the mainshocks is indistinguishable from the decay five minutes afterwards, indicating that the mainshocks have no effect at distances outside their static triggering range. Omori temporal decay, the fundamental signature of aftershocks, is absent at distances exceeding 10 km from the mainshocks. Finally, the distance decay is found among aftershocks that occur before the arrival of the seismic wave front from the mainshock, which violates causality. We argue that Felzer and Brodsky implicitly assume that the first of two independent aftershocks along a fault rupture triggers the second, and that the first of two shocks in a creep- or intrusion-driven swarm triggers the second, when this need not be the case.

  18. 76 FR 12760 - Comment Request for Information Collection for Report ETA 902, Disaster Unemployment Assistance...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-08

    ..., Disaster Unemployment Assistance Activities (OMB Control No. 1205- 0051): Extension Without Change AGENCY... ETA 902, Disaster Unemployment Assistance Activities under the Robert T. Stafford Disaster Relief and.... Background The ETA 902 Report, Disaster Unemployment Assistance (DUA) Activities, is a monthly...

  19. Start of Eta Car's X-ray Minimum

    NASA Technical Reports Server (NTRS)

    Corcoran, Michael F.; Liburd, Jamar; Hamaguchi, Kenji; Gull, Theodore; Madura, Thomas; Teodoro, Mairan; Moffat, Anthony; Richardson, Noel; Russell, Chris; Pollock, Andrew; Owocki, Stan

    2014-01-01

    Analysis of Eta Car's X-ray spectrum in the 2-10 keV band using quicklook data from the XRay Telescope on Swift shows that the flux on July 30, 2014 was 4.9 plus or minus 2.0×10(exp-12) ergs s(exp-1)cm(exp-2). This flux is nearly equal to the X-ray minimum flux seen by RXTE in 2009, 2003.5, and 1998, and indicates that Eta Car has reached its X-ray minimum, as expected based on the 2024-day period derived from previous 2-10 keV observations with RXTE.

  20. Observation of the radiative decay J/psi. -->. gamma. eta. pi pi

    SciTech Connect

    Newman-Holmes, C.

    1982-09-01

    The radiative decay J/psi ..-->.. ..gamma.. eta ..pi pi.. has been observed in data taken with the Crystal Ball detector at the SPEAR e/sup +/e/sup -/ storage ring. In addition to the well-known eta', the eta ..pi pi.. mass spectrum shows a broad enhancement centered at approx. 1700 MeV. There is no explicit evidence for the l(1440) in the eta ..pi pi.. mass spectrum.

  1. 77 FR 48174 - Comment Request for Information Collection for the ETA 203, Characteristics of the Insured...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-13

    ... Employment and Training Administration Comment Request for Information Collection for the ETA 203.... Gibbons. SUPPLEMENTARY INFORMATION: I. Background The ETA 203, Characteristics of the Insured Unemployed...-0009. Affected Public: State Workforce Agencies. Form(s): ETA 203. Total Annual Respondents: 53....

  2. 75 FR 3927 - Proposed Information Collection Request for the ETA 218, Benefit Rights and Experience Report...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-25

    ... Information Collection Request for the ETA 218, Benefit Rights and Experience Report; Comment Request on... unemployment compensation programs. The data in the ETA 218, Benefit Rights and Experience Report, includes... extension for the collection of the ETA 218, Benefit Rights and Experience report. Comments are...

  3. Search for eta '(958)-nucleus Bound States by (p,d) Reaction at GSI and FAIR

    NASA Astrophysics Data System (ADS)

    Fujioka, H.; Ayyad, Y.; Benlliure, J.; Brinkmann, K.-T.; Friedrich, S.; Geissel, H.; Gellanki, J.; Guo, C.; Gutz, E.; Haettner, E.; Harakeh, M. N.; Hayano, R. S.; Higashi, Y.; Hirenzaki, S.; Hornung, C.; Igarashi, Y.; Ikeno, N.; Itahashi, K.; Iwasaki, M.; Jido, D.; Kalantar-Nayestanaki, N.; Kanungo, R.; Knoebel, R.; Kurz, N.; Metag, V.; Mukha, I.; Nagae, T.; Nagahiro, H.; Nanova, M.; Nishi, T.; Ong, H. J.; Pietri, S.; Prochazka, A.; Rappold, C.; Reiter, M. P.; Rodríguez-Sánchez, J. L.; Scheidenberger, C.; Simon, H.; Sitar, B.; Strmen, P.; Sun, B.; Suzuki, K.; Szarka, I.; Takechi, M.; Tanaka, Y. K.; Tanihata, I.; Terashima, S.; Watanabe, Y. N.; Weick, H.; Widmann, E.; Winfield, J. S.; Xu, X.; Yamakami, H.; Zhao, J.

    The mass of the {\\eta}' meson is theoretically expected to be reduced at finite density, which indicates the existence of {\\eta}'-nucleus bound states. To investigate these states, we perform missing-mass spectroscopy for the (p, d) reaction near the {\\eta}' production threshold. The overview of the experimental situation is given and the current status is discussed.

  4. 31 CFR Appendix B to Part 208 - Model Disclosure for Use After ETA SM Becomes Available

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 2 2010-07-01 2010-07-01 false Model Disclosure for Use After ETA SM... FEDERAL AGENCY DISBURSEMENTS Pt. 208, App. B Appendix B to Part 208—Model Disclosure for Use After ETA SM... through a basic, low-cost account called an ETA SM. If you receive a Federal benefit, wage, salary,...

  5. Strong aftershocks in the northern segment of the Wenchuan earthquake rupture zone and their seismotectonic implications

    NASA Astrophysics Data System (ADS)

    Zheng, Yong; Ni, Sidao; Xie, Zujun; Lv, Jian; Ma, Hongsheng; Sommerville, Paul

    2010-11-01

    More than 28, 000 aftershocks have occurred since the 05/12/2008 Wenchuan earthquake, with dozens of them stronger than M 5. Since July, 2008, all the M > 5 earthquakes have occurred only in the northern segment of the rupture zone, suggesting obvious seismicity segmentation. We applied the double difference method to relocate all of the M > 3 aftershocks. After relocation, the aftershocks show a compact zone of seismicity, with a length of about 300 km and average width of 30 km, supporting that the hypothesis that the Beichuan-Yingxiu and Chaping-Linjiaan faults are the faults that ruptured in the earthquake. With the Cut and Paste (CAP) waveform inversion algorithm, we determined the source mechanism and focal depth of all the > M 5 aftershocks in the northern segments. The number of thrust events is close to the number of strike-slip events, but almost all of the events with thrust mechanism are distributed over the northern segment, while the aftershocks with strike-slip mechanism only occurred at the north-easternmost end, contrasting with field observations of a substantial strike-slip component of surface rupture over the northern segment. The events with strike-slip mechanism occurred at depths up to 18 km, consistent with the lack of surface rupture in the north-easternmost section. However, since early August, very shallow events (2 km) with thrust mechanism have occurred, probably releasing the strain energy of the unruptured fault in the north-easternmost section. It seems that the seismic hazard potential of the northern segment is still quite high, and more studies are needed to resolve some of the discrepancy suggested by aftershock patterns and other observations.

  6. An exploration of reported cognitions during an earthquake and its aftershocks: differences across affected communities and associations with psychological distress.

    PubMed

    Kannis-Dymand, Lee; Dorahy, Martin J; Crake, Rosemary; Gibbon, Peter; Luckey, Rhys

    2015-04-01

    Cognitive themes in two communities differentially affected by the September 2010 Christchurch earthquake and aftershocks were investigated. Participants (N = 124) completed questions about their thoughts during the earthquake and aftershocks as well as measures of acute stress, anxiety, and depression. Cognitions were qualitatively analyzed into themes for the earthquake and aftershocks. Themes were examined for differences across the two suburbs and associations with psychological distress. Nine cognitive themes were identified within three superordinate domains. The cognitive theme of worry and concern was the most frequently occurring for the earthquake and aftershocks across the whole sample and for the more affected suburb. Current threat was the most frequent theme for the earthquake in the less affected suburb, whereas worry and concern was the most evident in this group for aftershocks. The superordinate theme of threat was significantly related to higher acute stress disorder scores in the more affected suburb for earthquake-reported cognitions.

  7. Joint inversion of teleseismic body-waves and geodetic data for the Mw6.8 aftershock of the Balochistan earthquake with refined epicenter location

    NASA Astrophysics Data System (ADS)

    Wei, S.; Wang, T.; Jonsson, S.; Avouac, J. P.; Helmberger, D. V.

    2014-12-01

    Aftershocks of the 2013 Balochistan earthquake are mainly concentrated along the northeastern end of the mainshock rupture despite of much larger coseismic slip to the southwest. The largest event among them is an Mw6.8 earthquake which occurred three days after the mainshock. A kinematic slip model of the mainshock was obtained by joint inversion of the teleseismic body-waves and horizontal static deformation field derived from remote sensing optical and SAR data, which is composed of seven fault segments with gradually changing strikes and dips [Avouac et al., 2014]. The remote sensing data provide well constraints on the fault geometry and spatial distribution of slip but no timing information. Meanwhile, the initiation of the teleseismic waveform is very sensitive to fault geometry of the epicenter segment (strike and dip) and spatial slip distribution but much less sensitive to the absolute location of the epicenter. The combination of the two data sets allows a much better determination of the absolute epicenter location, which is about 25km to the southwest of the NEIC epicenter location. The well located mainshock epicenter is used to establish path calibrations for teleseismic P-waves, which are essential for relocating the Mw6.8 aftershock. Our grid search shows that the refined epicenter is located right at the northeastern end of the mainshock rupture. This is confirmed by the SAR offsets calculated from images acquired after the mainshock. The azimuth and range offsets display a discontinuity across the rupture trace of the mainshock. Teleseismic only and static only, as well as joint inversions all indicate that the aftershock ruptured an asperity with 25km along strike and range from 8km to 20km in depth. The earthquake was originated in a positive Coulomb stress change regime due to the mainshock and has complementary slip distribution to the mainshock rupture at the northeastern end, suggesting that the entire seismic generic zone in the crust was

  8. Eta Sigma Gamma: Preparing Leaders Today for Tomorrow's Challenges

    ERIC Educational Resources Information Center

    Brown, Kelli McCormack

    2007-01-01

    There is no one definition for a leader or for leadership, but most people can identify a leader and can provide qualities of a good leader or good leadership. The founders of Eta Gamma Gamma--William Bock, Warren Schaller, and Robert Synovitz--all displayed a critical characteristic of leadership by having and acting on a vision. Leadership has…

  9. Targeting Inaccurate Atomic Data in the Eta Car Ejecta Absorption

    NASA Technical Reports Server (NTRS)

    Nielsen, K. E.; Kober, G. Vieira; Gull, T. R.; Blackwell-Whitehead, R.; Nilsson, H.

    2006-01-01

    The input from the laboratory spectroscopist community has on many occasions helped the analysis of the eta Car spectrum. Our analysis has targeted spectra where improved wavelengths and oscillator strengths are needed. We will demonstrate how experimentally derived atomic data have improved our spectral analysis, and illuminate where more work still is needed.

  10. Spectra of Eta Carina from Objective Prism Photographic Plates

    NASA Astrophysics Data System (ADS)

    Cline, J. Donald; Castelaz, M.; Barker, T.

    2008-05-01

    Brightness and spectral variations of Eta Carina occur over a 5.5 year cycle. Emission lines were observed to fade in 1948, 1962, 1981, 1987, and 1992 (Damineli 1996, ApJ, 460, L49), and 1997 (Eta Carinae at the Millennium, ASP Conf. Ser. 179, ed. J.A. Morse, R.M. Humphreys, and A. Damineli). Gaps in the observation of spectra occur in 1970 and 1975 when two other such occurrences of the 5.5 year cycle were expected. Objective prism photographic plates of Eta Carina were found in the Astronomical Photographic Data Archive located at Pisgah Astronomical Research Institute. The plates belong to the University of Michigan survey (Houk 1978, Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars). One plate, IN emulsion + RG1 filter, was taken on 1968 July 4 UT. The other plate, IIaO emulsion, was taken on 1972 March 12 UT. These plates were taken between the 5.5 year cyclic events of 1970 and 1975 and therefore represent the usual emission line spectra. The spectrum of Eta Car was extracted from each of the objective prism plates and will be presented.

  11. Detection of the Compressed Primary Stellar Wind in eta Carinae

    NASA Technical Reports Server (NTRS)

    Teodoro, Mairan Macedo; Madura, Thomas I.; Gull, Theodore R.; Corcoran, Michael F.; Hamaguchi, K.

    2014-01-01

    A series of three HST/STIS spectroscopic mappings, spaced approximately one year apart, reveal three partial arcs in [Fe II] and [Ni II] emissions moving outward from eta Carinae. We identify these arcs with the shell-like structures, seen in the 3D hydrodynamical simulations, formed by compression of the primary wind by the secondary wind during periastron passages.

  12. Insights into the pi- p --> eta n reaction mechanism

    SciTech Connect

    Durand, Johan; Julia Diaz, Bruno; Lee, Tsung-Shung; Sato, Toru

    2009-01-01

    A dynamical coupled-channels formalism is used to investigate the $\\eta-$meson production mechanism on the proton induced by pions, in the total center-of-mass energy region from threshold up to 2 GeV. We show how and why studying exclusively total cross section data might turn out to be misleading in pinning down the reaction mechanism.

  13. EMISSIONS PROCESSING FOR THE ETA/ CMAQ AIR QUALITY FORECAST SYSTEM

    EPA Science Inventory

    NOAA and EPA have created an Air Quality Forecast (AQF) system. This AQF system links an adaptation of the EPA's Community Multiscale Air Quality Model with the 12 kilometer ETA model running operationally at NOAA's National Center for Environmental Predication (NCEP). One of the...

  14. The Eight-meter-wavelength Transient Array (ETA)

    NASA Astrophysics Data System (ADS)

    Simonetti, J. H.; Ellingson, S. W.; Patterson, C. D.; Taylor, W.; Venugopal, V.; Cutchin, S.; Boor, Z.

    2005-12-01

    The Eight-meter-wavelength Transient Array (ETA) is a radio telescope utilizing a low-cost backend, which implements flexible, reconfigurable computing techniques. It is designed to continuously monitor nearly the entire northern sky at 29-47MHz in a search for low-frequency radio transients (short pulses) from high-energy astrophysical phenomena. This antenna array, which is currently under construction, is located in a relatively radio-quiet area in the Blue Ridge Mountains southwest of Asheville, NC, at the Pisgah Astronomical Research Institute (PARI). The array consists of 12 dual-polarization dipole antennas. The core of the array is 10 antenna stations arranged in a 16-m diameter circle with one antenna station at the center. In addition, one antenna station is situated about 50m to the north of the core and another is about 50m to the east of the core. A 26-m dish on the PARI site (about 1km from the ETA core) will be used for follow-up, added aperture, longer baselines, and additional radio frequency interference (RFI) mitigation. Preliminary observations with one test antenna station have detected the expected Galactic emission in this frequency range; ETA will be Galactic-noise limited. The ETA backend will utilize off-the-shelf components and a cluster of Field Programmable Gate Arrays (FPGAs) for detecting pulses of various lengths, dispersion measures, and directions (synthesized delay beams), while incorporating various RFI countermeasures. Potential sources of radio transients that might be observed by ETA include gamma-ray bursts (prompt emission), supernovae (prompt emission), coalescing compact-object binaries (e.g., neutron star -- neutron star, neutron star -- black hole), and exploding primordial black holes. This array should detect giant pulses from the Crab Pulsar, and possibly other pulsars. ETA is a collaboration of the Electrical and Computer Engineering Department and Physics Department at Virginia Tech, and PARI. ETA work at Virginia

  15. Okubo-Zweig-Iizuka-rule violation and B{yields}{eta}{sup (')}K branching ratios

    SciTech Connect

    Hsu, J.-F.; Charng, Y.-Y.; Li, Hsiang-nan

    2008-07-01

    We show that the few-percent Okubo-Zweig-Iizuka-rule violating effects in the quark-flavor basis for the {eta}-{eta}{sup '} mixing can enhance the chiral scale associated with the {eta}{sub q} meson a few times. This enhancement is sufficient for accommodating the dramatically different data of the B{yields}{eta}{sup '}K and B{yields}{eta}K branching ratios. We comment on other proposals for resolving this problem, including flavor-singlet contributions, axial U(1) anomaly, and nonperturbative charming penguins. Discrimination of the above proposals by means of the B{yields}{eta}{sup (')}l{nu} and B{sub s}{yields}{eta}{sup (')}ll data is suggested.

  16. Does dinitrogen hydrogenation follow different mechanisms for [(eta5-C5Me4H)2Zr]2(mu2,eta2,eta2-N2) and {[PhP(CH2SiMe2NSiMe2CH2)PPh]Zr}2(mu2,eta2,eta2-N2) complexes? A computational study.

    PubMed

    Bobadova-Parvanova, Petia; Wang, Qingfang; Quinonero-Santiago, David; Morokuma, Keiji; Musaev, Djamaladdin G

    2006-09-01

    The mechanisms of dinitrogen hydrogenation by two different complexes--[(eta(5)-C(5)Me(4)H)(2)Zr](2)(mu(2),eta(2),eta(2)-N(2)), synthesized by Chirik and co-workers [Nature 2004, 427, 527], and {[P(2)N(2)]Zr}(2)(mu(2),eta(2),eta(2)-N(2)), where P(2)N(2) = PhP(CH(2)SiMe(2)NSiMe(2)CH(2))(2)PPh, synthesized by Fryzuk and co-workers [Science 1997, 275, 1445]--are compared with density functional theory calculations. The former complex is experimentally known to be capable of adding more than one H(2) molecule to the side-on coordinated N(2) molecule, while the latter does not add more than one H(2). We have shown that the observed difference in the reactivity of these dizirconium complexes is caused by the fact that the former ligand environment is more rigid than the latter. As a result, the addition of the first H(2) molecule leads to two different products: a non-H-bridged intermediate for the Chirik-type complex and a H-bridged intermediate for the Fryzuk-type complex. The non-H-bridged intermediate requires a smaller energy barrier for the second H(2) addition than the H-bridged intermediate. We have also examined the effect of different numbers of methyl substituents in [(eta(5)-C(5)Me(n)H(5)(-)(n))(2)Zr](2)(mu(2),eta(2),eta(2)-N(2)) for n = 0, 4, and 5 (n = 5 is hypothetical) and [(eta(5)-C(5)H(2)-1,2,4-Me(3))(eta(5)-C(5)Me(5))(2)Zr](2)(mu(2),eta(2),eta(2)-N(2)) and have shown that all complexes of this type would follow a similar H(2) addition mechanism. We have also performed an extensive analysis on the factors (side-on coordination of N(2) to two Zr centers, availability of the frontier orbitals with appropriate symmetry, and inflexibility of the catalyst ligand environment) that are required for successful hydrogenation of the coordinated dinitrogen.

  17. Aftershock source mechanisms from the June 9, 1994, Deep Bolivian Earthquake

    NASA Astrophysics Data System (ADS)

    Tinker, Mark Andrew; Wallace, Terry C.; Beck, Susan L.; Silver, Paul G.; Zandt, George

    The Mw 8.3 Bolivia earthquake occurred on June 9, 1994, at a depth of 636 km. This is the largest deep event in recorded history and ruptured a portion of the down-going Nazca slab unknown to have ruptured previously. We recorded the main shock and aftershocks on the BANJO and SEDA portable, broadband seismic arrays deployed in Bolivia during this event. Myers et al. (this issue) identified and located 36 aftershocks (M>2) for the 10-day period following the main shock. We use a grid search technique to determine focal mechanisms for 12 of these aftershocks ranging in magnitude from 2.7 to 5.3. We compare the observed P to SV and SH ratios to a series of synthetics that represent different fault plane orientations. We find consistent focal mechanisms with the T-axis roughly horizontal and oriented approximately east-west, and the P-axis predominantly vertical. The aftershock focal mechanisms indicate a rotation of the P-axis within the slab from down-dip compression prior to the main shock to a near-vertical direction afterwards. This observation is consistent with the release of shear stress on the near-horizontal rupture plane and the subsequent rotation of the maximum compressive stress to a fault -normal orientation.

  18. Aftershock seismicity and Tectonic Setting of the 16 September 2015 Mw 8.3 Illapel earthquake

    NASA Astrophysics Data System (ADS)

    Lange, Dietrich; Geersen, Jacob; Barrientos, Sergio; Moreno, Marcos; Grevemeyer, Ingo; Contreras-Reyes, Eduardo; Kopp, Heidrun

    2016-04-01

    Powerful subduction zone earthquakes rupture thousands of square kilometers along continental margins but at certain locations earthquake rupture terminates. On 16 September 2015 the Mw. 8.3 Illapel earthquake ruptured a 200 km long stretch of the Central Chilean subduction zone, triggering a tsunami and causing significant damage. Here we analyze the spatial pattern of coseismic rupture and the temporal and spatial pattern of local seismicity for aftershocks and foreshocks in relation to the tectonic setting in the earthquake area. Aftershock seismicity surrounds the rupture area in lateral and downdip direction. For the first 24 hours following the mainshock we observe aftershock migration to both lateral directions with velocities of approximately 2.5 and 5 km/h. At the southern earthquake boundary aftershocks cluster around individual subducted seamounts located on the prolongation of the downthrusting Juan Fernández Ridge indicating stress transfer from the main rupture area. In the northern part of the rupture area a deeper band of local seismicity is observed indicating an alternation of seismic to aseismic behavior of the plate interface in downdip direction. This aseismic region at ~30 km depth that is also observed before the Illapel 2015 earthquake is likely controlled by the intersection of the continental Moho with the subducting slab.

  19. The enigma of the Arthur's Pass, New Zealand, earthquake 1. Reconciling a variety of data for an unusual earthquake sequence

    USGS Publications Warehouse

    Abercrombie, R.E.; Webb, T.H.; Robinson, R.; McGinty, P.J.; Mori, J.J.; Beavan, R.J.

    2000-01-01

    The 1994 Arthur's Pass earthquake (Mw6.7) is the largest in a recent sequence of earthquakes in the central South Island, New Zealand. No surface rupture was observed the aftershock distribution was complex, and routine methods of obtaining the faulting orientation of this earthquake proved contradictory. We use a range of data and techniques to obtain our preferred solution, which has a centroid depth of 5 km, Mo=1.3??1019 N m, and a strike, dip, and rake of 221??, 47??, 112??, respectively. Discrepancies between this solution and the Harvard centroid moment tensor, together with the Global Positioning System (GPS) observations and unusual aftershock distribution, suggest that the rupture may not have occurred on a planar fault. A second, strike slip, subevent on a more northerly striking plane is suggested by these data but neither the body wave modeling nor regional broadband recordings show any complexity or late subevents. We relocate the aftershocks using both one-dimensional and three-dimensional velocity inversions. The depth range of the aftershocks (1-10 km) agrees well with the preferred mainshock centroid depth. The aftershocks near the hypocenter suggest a structure dipping toward the NW, which we interpret to be the mainshock fault plane. This structure and the Harper fault, ???15 km to the south appear to have acted as boundaries to the extensive aftershock zone trending NNW-SSE Most of the ML???5 aftershocks, including the two largest (ML6.1 and ML5.7), clustered near the Harper fault and have strike slip mechanisms consistent with motion on this fault and its conjugates. Forward modeling of the GPS data suggests that a reverse slip mainshock, combined with strike slip aftershock faulting in the south, is able to match the observed displacements. The occurrence of this earthquake sequence implies that the level of seismic hazard in the central South Island is greater than previous estimates. Copyright 2000 by the American Geophysical Union.

  20. Estimates of velocity structure and source depth using multiple P waves from aftershocks of the 1987 Elmore Ranch and Superstition Hills, California, earthquakes

    USGS Publications Warehouse

    Mori, J.

    1991-01-01

    Event record sections, which are constructed by plotting seismograms from many closely spaced earthquakes recorded on a few stations, show multiple free-surface reflections (PP, PPP, PPPP) of the P wave in the Imperial Valley. The relative timing of these arrivals is used to estimate the strength of the P-wave velocity gradient within the upper 5 km of the sediment layer. Consistent with previous studies, a velocity model with a value of 1.8 km/sec at the surface increasing linearly to 5.8 km/sec at a depth of 5.5 km fits the data well. The relative amplitudes of the P and PP arrivals are used to estimate the source depth for the aftershock distributions of the Elmore Ranch and Superstition Hills main shocks. Although the depth determination has large uncertainties, both the Elmore Ranch and Superstition Hills aftershock sequencs appear to have similar depth distribution in the range of 4 to 10 km. -Author

  1. The detection of a companion star to the Cepheid variable Eta Aquilae

    NASA Technical Reports Server (NTRS)

    Mariska, J. T.; Doschek, G. A.; Feldman, U.

    1980-01-01

    Ultraviolet spectra have been obtained with IUE of the classical Cepheid Eta Aquilae at several phases in the 7.18 day period. Significant ultraviolet emission is detected at wavelengths less than 1600 A, where little flux is expected from classical Cepheids. Furthermore, the emission at wavelengths less than about 1600 A does not vary with phase. Comparison with model atmosphere flux distributions shows that the nonvariable emission is consistent with the flux expected from a main-sequence companion star with an effective temperature of about 9500 K (A0 V). The observed ultraviolet flux and spectral type are used to compute a distance of 300 pc to the system, in agreement with the distance predicted using the period luminosity relation.

  2. Decay of aftershock density with distance does not indicate triggering by dynamic stress.

    PubMed

    Richards-Dinger, Keith; Stein, Ross S; Toda, Shinji

    2010-09-30

    Resolving whether static or dynamic stress triggers most aftershocks and subsequent mainshocks is essential to understand earthquake interaction and to forecast seismic hazard. Felzer and Brodsky examined the distance distribution of earthquakes occurring in the first five minutes after 2 ≤ M < 3 and 3 ≤ M < 4 mainshocks and found that their magnitude M ≥ 2 aftershocks showed a uniform power-law decay with slope -1.35 out to 50 km from the mainshocks. From this they argued that the distance decay could be explained only by dynamic triggering. Here we propose an alternative explanation for the decay, and subject their hypothesis to a series of tests, none of which it passes. At distances more than 300 m from the 2 ≤ M < 3 mainshocks, the seismicity decay 5 min before the mainshocks is indistinguishable from the decay five minutes afterwards, indicating that the mainshocks have no effect at distances outside their static triggering range. Omori temporal decay, the fundamental signature of aftershocks, is absent at distances exceeding 10 km from the mainshocks. Finally, the distance decay is found among aftershocks that occur before the arrival of the seismic wave front from the mainshock, which violates causality. We argue that Felzer and Brodsky implicitly assume that the first of two independent aftershocks along a fault rupture triggers the second, and that the first of two shocks in a creep- or intrusion-driven swarm triggers the second, when this need not be the case.

  3. Revisit the radiative decays of J/{psi} and {psi}{sup '}{yields}{gamma}{eta}{sub c}({gamma}{eta}{sub c}{sup '})

    SciTech Connect

    Li Gang; Zhao Qiang

    2011-10-01

    With the new measurements of J/{psi} and {psi}{sup '}{yields}{gamma}{eta}{sub c}({gamma}{eta}{sub c}{sup '}) from the CLEO and BES-III collaboration, we reinvestigate the intermediate meson loop (IML) contributions to these radiative decays in association with the quark model M1 transitions in an effective Lagrangian approach. It shows that the ''unquenched'' effects due to the intermediate hadron loops can be better quantified by the new data for J/{psi}{yields}{gamma}{eta}{sub c}. Although the IML contributions are relatively small in J/{psi}{yields}{gamma}{eta}{sub c}, they play a crucial role in {psi}{sup '}{yields}{gamma}{eta}{sub c}({gamma}{eta}{sub c}{sup '}). A prediction for the IML contributions to {psi}(3770){yields}{gamma}{eta}{sub c}({gamma}{eta}{sub c}{sup '}) is made. Such unquenched effects allow us to reach a coherent description of those three radiative transitions, and gain some insights into the underlying dynamics.

  4. Isolation of Omnipotent Suppressors in an [Eta(+)] Yeast Strain

    PubMed Central

    All-Robyn, J. A.; Kelley-Geraghty, D.; Griffin, E.; Brown, N.; Liebman, S. W.

    1990-01-01

    Omnipotent suppressors decrease translational fidelity and cause misreading of nonsense codons. In the presence of the non-Mendelian factor [eta(+)], some alleles of previously isolated omnipotent suppressors are lethal. Thus the current search was conducted in an [eta(+)] strain in an effort to identify new suppressor loci. A new omnipotent suppressor, SUP39, and alleles of sup35, sup45, SUP44 and SUP46 were identified. Efficiencies of the dominant suppressors were dramatically reduced in strains that were cured of non-Mendelian factors by growth on guanidine hydrochloride. Wild-type alleles of SUP44 and SUP46 were cloned and these clones were used to facilitate the genetic analyses. SUP44 was shown to be on chromosome VII linked to cyh2, and SUP46 was clearly identified as distinct from the linked sup45. PMID:2311916

  5. Turbidity of a binary fluid mixture: Determining eta

    NASA Technical Reports Server (NTRS)

    Jacobs, Donald T.

    1994-01-01

    A ground based (1-g) experiment is in progress that will measure the turbidity of a density-matched, binary fluid mixture extremely close to the critical point. By covering the range of reduced temperatures t is equivalent to (T-T(sub c))/T(sub c) from 10(exp -8) to 10(exp -2), the turbidity measurements will allow the critical exponent eta to be determined. No experiment has determined a value of the critical exponent eta, yet its value is significant to theorists in critical phenomena. Interpreting the turbidity correctly is important if future NASA flight experiments use turbidity as an indirect measurement of relative temperature in shuttle experiments on critical phenomena in fluids.

  6. Turbidity of a Binary Fluid Mixture: Determining Eta

    NASA Technical Reports Server (NTRS)

    Jacobs, Donald T.

    1996-01-01

    A ground based (1-g) experiment is in progress that will measure the turbidity of a density-matched, binary fluid mixture extremely close to its liquid-liquid critical point. By covering the range of reduced temperatures t equivalent to (T-T(sub c)) / T(sub c) from 10(exp -8) to 10(exp -2), the turbidity measurements will allow the critical exponent eta to be determined. No experiment has precisely determined a value of the critical exponent eta, yet its value is significant to theorists in critical phenomena. Relatively simple critical phenomena, as in the liquid-liquid system studied here, serve as model systems for more complex systems near a critical point.

  7. Preliminary Focal Mechanism Analysis of the 6 November 2011 M 5.7 Oklahoma sequence

    NASA Astrophysics Data System (ADS)

    Wei, M.; Sumy, D. F.; Cochran, E. S.; Keranen, K. M.; Abers, G. A.; Savage, H. M.

    2012-12-01

    A M5.7 strike-slip earthquake occurred on 6 November 2011 near Prague, Oklahoma and was followed by hundreds of aftershocks in the subsequent months. While earthquakes are not unknown to Oklahoma, seismicity rates in the region have risen steadily since 2008, with increases in both the frequency and intensity of the earthquakes observed. The M5.7 earthquake is the largest quake recorded during this recent period of increased seismicity. Prior to the mainshock, 19 seismometers were located within approximately 100 km of the event. An additional 28 seismometers were temporarily deployed after the mainshock to record the aftershock sequence. We use data collected from these seismometers to calculate the focal mechanisms for a subset of the aftershocks. Here, we examine the 80 largest aftershocks that occur prior to 31 December 2011. P-wave arrivals and polarities are manually identified on the vertical component of each station. Polarities are marked as impulsive or emergent and the pick is given a quality rating (0-4). We then use HASH (Hardebeck and Shearer, 2002) and a 1-D velocity model to calculate the focal mechanisms. For each event, HASH outputs a set of acceptable mechanisms and, based on how clustered the set of acceptable mechanisms is, a quality and uncertainty is assigned. The early aftershock locations suggest that the 5 November 2011 M5.0 foreshock, 6 November 2011 M5.7 mainshock, and the largest (8 November 2011 M5.0) aftershock may have occurred on faults with strikes of 34°, 55°, and 90°, respectively. Given this change in fault strike for the largest events in the sequence, we will investigate whether there is also a systematic variation in the aftershock focal mechanisms with time. We will also investigate spatial variation in focal mechanism type (e.g. strike-slip, normal, or thrust) and inferred fault strike.

  8. DETECTION OF THE COMPRESSED PRIMARY STELLAR WIND IN {eta} CARINAE

    SciTech Connect

    Teodoro, M.; Madura, T. I.; Gull, T. R.; Corcoran, M. F.; Hamaguchi, K.

    2013-08-10

    A series of three Hubble Space Telescope/Space Telescope Imaging Spectrograph spectroscopic mappings, spaced approximately one year apart, reveal three partial arcs in [Fe II] and [Ni II] emissions moving outward from {eta} Carinae. We identify these arcs with the shell-like structures, seen in the three-dimensional hydrodynamical simulations, formed by compression of the primary wind by the secondary wind during periastron passages.

  9. The {eta}{sub 6} at LEP and TRISTAN

    SciTech Connect

    Kang, K.; Knowles, I.G.; White, A.R.

    1993-01-20

    The {eta}{sub 6} is a {open_quotes}heavy axion{close_quotes} remnant of dynamical electroweak symmetry breaking by a color sextet quark condensate. Electroweak scale color instanton interactions allow it to be both very massive and yet be responsible for Strong CP conservation in the color triplet quark sector. It may have been seen at LEP via its two-photon decay mode and at TRISTAN via its hadronic decay modes.

  10. Revealing the Chamaeleon: Young, low-mass stars surrounding eta and epsilon Chamaeleontis

    NASA Astrophysics Data System (ADS)

    Murphy, S. J.

    2012-01-01

    The deep southern sky surrounding the Chamaeleon dark clouds is abundant with pre-main sequence stars of various ages. Because of their youth (5-10 Myr) and proximity (d~100 pc), members of the open cluster eta Chamaeleontis and the nearby epsilon Chamaeleontis Association are ideal laboratories to study the formation and evolution of extrasolar planetary systems. To better understand their role as potential planet hosts, this thesis explores the formation, dynamical evolution, accretion and disk properties of both groups' low-mass members. The notable lack of low-mass stars in the young open cluster eta Cha has long been puzzling. Two possible explanations have been suggested; a top-heavy initial mass function or dynamical evolution, which preferentially ejected the low-mass members. Previous efforts to find these stars several degrees from the cluster core have been unsuccessful. By undertaking a wider (95 sq deg) photometric and proper motion survey with extensive follow-up spectroscopy, we have identified eight low-mass stars that were ejected from eta Cha over the past 5-10 Myr. Comparison with recent simulations shows our results are consistent with a dynamical origin for the current configuration of the cluster, without the need to invoke an initial mass function deficient in low-mass objects. Two of the dispersed members exhibited strong, variable H-alpha emission during our observations, including a star which had an event suggestive of accretion from a circumstellar disk. New infrared photometry confirms the presence of the disk. This star demonstrates that infrequent, episodic accretion can continue at low levels long after most disks around `old' pre-main sequence stars have dissipated. Another two confirmed non-members are slightly older than the cluster, but are only 42 arcseconds apart and share similar kinematics and distances. We show that they almost certainly form a wide (4000-6000 AU) ~10 Myr-old binary at 100-150 pc. The system is one of the

  11. Chandra X-Ray Observatory Image of Eta Carinae

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This Chandra X-Ray Observatory image of the mysterious superstar Eta Carinae reveals a surprising hot irner core, creating more questions than answers for astronomers. The image shows three distinct structures: An outer, horseshoe shaped ring about 2 light-years in diameter, a hot inner core about 3 light-months in diameter, and a hot central source less than a light-month in diameter which may contain the superstar. In 1 month, light travels a distance of approximately 489 billion miles (about 788 billion kilometers). All three structures are thought to represent shock waves produced by matter rushing away from the superstar at supersonic speeds. The temperature of the shock-heated gas ranges from 60 million degrees Kelvin in the central regions to 7 million degrees Kelvin on the outer structure. Eta Carinae is one of the most enigmatic and intriguing objects in our galaxy. Between 1837 and 1856, it increased dramatically in brightness to become the most prominent star in the sky except for Sirius, even through it is 7,500 light-years away, more than 80 times the distance to Sirius. This 'Great Eruption,' as it is called, had an energy comparable to a supernova, yet did not destroy the star, which faded to become a dim star, invisible to the naked eye. Since 1940, Eta Carinae has begun to brighten again, becoming visible to the naked eye. Photo credit: NASA/CXC/SAO

  12. High Velocity Absorption during Eta Car B's Periastron Passage

    NASA Technical Reports Server (NTRS)

    Nielsen, Krister E.; Groh, J. H.; Hillier, J.; Gull, Theodore R.; Owocki, S. P.; Okazaki, A. T.; Damineli, A.; Teodoro, M.; Weigelt, G.; Hartman, H.

    2010-01-01

    Eta Car is one of the most luminous massive stars in the Galaxy, with repeated eruptions with a 5.5 year periodicity. These events are caused by the periastron passage of a massive companion in an eccentric orbit. We report the VLT/CRIRES detection of a strong high-velocity, (<1900 km/s) , broad absorption wing in He I at 10833 A during the 2009.0 periastron passage. Previous observations during the 2003.5 event have shown evidence of such high-velocity absorption in the He I 10833 transition, allowing us to conclude that the high-velocity gas is crossing the line-of-sight toward Eta Car over a time period of approximately 2 months. Our analysis of HST/STlS archival data with observations of high velocity absorption in the ultraviolet Si IV and C IV resonance lines, confirm the presence of a high-velocity material during the spectroscopic low state. The observations provide direct detection of high-velocity material flowing from the wind-wind collision zone around the binary system, and we discuss the implications of the presence of high-velocity gas in Eta Car during periastron

  13. 2{eta} or not 2{eta}? Insights into the Cu CVD process using a Cu(I) precursor

    SciTech Connect

    Kumar, R.; Maverick, A.W.; Fronczek, F.R.; Kim, A.J.; Butler, L.G.

    1993-12-31

    One of the first successful Cu(I) CVD precursors is (hfac)Cu{sup I}(COD), and this species continues to served as a model system. In the CVD process, a significant step is dissociation of the COD ligand. The energetics of this process have been estimated previously. However, it now appears that, in the solid state, (hfac)Cu{sup I}(COD) undergoes an exchange process that allows additional insight into the potential energy surface governing the Cu-COD interaction. The solid-state structure of (hfac)Cu{sup I}(COD) has been difficult to establish, but a combination of variable temperature X-ray and solid-state {sup 13}C NMR studies leads to the following picture. Cu{sup I} is three-coordinate, bound to the hfac ligand and bound preferentially to one olefin of the COD ligand. There is a small energy barrier associated with motion of the Cu into position for {eta}{sup 2}-binding to the other olefin; the COD and hfac ligands remain approximately stationary. Thus, there are two sites for Cu, now labeled {eta}{sup 2} and {eta}{sup 2}. This new interpretation of the solid-state structure differs from that of our 300 K data set and a previous report. In addition, the exchange process is intimately connected with the Cu-COD dissociation step in the CVD process.

  14. Directional topographic site response at Tarzana observed in aftershocks of the 1994 Northridge, California, earthquake: Implications for mainshock motions

    USGS Publications Warehouse

    Spudich, P.; Hellweg, M.; Lee, W.H.K.

    1996-01-01

    The Northridge earthquake caused 1.78 g acceleration in the east-west direction at a site in Tarzana, California, located about 6 km south of the mainshock epicenter. The accelerograph was located atop a hill about 15-m high, 500-m long, and 130-m wide, striking about N78??E. During the aftershock sequence, a temporary array of 21 three-component geophones was deployed in six radial lines centered on the accelerograph, with an average sensor spacing of 35 m. Station COO was located about 2 m from the accelerograph. We inverted aftershock spectra to obtain average relative site response at each station as a function of direction of ground motion. We identified a 3.2-Hz resonance that is a transverse oscillation of the hill (a directional topographic effect). The top/base amplification ratio at 3.2 Hz is about 4.5 for horizontal ground motions oriented approximately perpendicular to the long axis of the hill and about 2 for motions parallel to the hill. This resonance is seen most strongly within 50 m of COO. Other resonant frequencies were also observed. A strong lateral variation in attenuation, probably associated with a fault, caused substantially lower motion at frequencies above 6 Hz at the east end of the hill. There may be some additional scattered waves associated with the fault zone and seen at both the base and top of the hill, causing particle motions (not spectral ratios) at the top of the hill to be rotated about 20?? away from the direction transverse to the hill. The resonant frequency, but not the amplitude, of our observed topographic resonance agrees well with theory, even for such a low hill. Comparisons of our observations with theoretical results indicate that the 3D shape of the hill and its internal structure are important factors affecting its response. The strong transverse resonance of the hill does not account for the large east-west mainshock motions. Assuming linear soil response, mainshock east-west motions at the Tarzana accelerograph

  15. Rare decay {eta}{r_arrow}{pi}{pi}{gamma}{gamma} in chiral perturbation theory

    SciTech Connect

    Knoechlein, G.; Scherer, S.; Drechsel, D.

    1996-04-01

    We investigate the rare radiative {eta} decay modes {eta}{r_arrow}{pi}{sup +}{pi}{sup {minus}}{gamma}{gamma} and {eta}{r_arrow}{pi}{sup 0}{pi}{sup 0}{gamma}{gamma} within the framework of chiral perturbation theory at {ital O}({ital p}{sup 4}). We present photon spectra and partial decay rates for both processes as well as a Dalitz contour plot for the charged decay. {copyright} {ital 1996 The American Physical Society.}

  16. The adaptive CCCG({eta}) method for efficient solution of time dependent partial differential equations

    SciTech Connect

    Campos, F.F.; Birkett, N.R.C.

    1996-12-31

    The Controlled Cholesky factorisation has been shown to be a robust preconditioner for the Conjugate Gradient method. In this scheme the amount of fill-in is defined in terms of a parameter {eta}, the number of extra elements allowed per column. It is demonstrated how an optimum value of {eta} can be automatically determined when solving time dependent p.d.e.`s using an implicit time step method. A comparison between CCCG({eta}) and the standard ICCG solving parabolic problems on general grids shows CCCG({eta}) to be an efficient general purpose solver.

  17. 77 FR 70833 - Comment Request for Information Collection on the ETA 9048, Worker Profiling and Reemployment...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-27

    ... information technology, e.g., permitting electronic submissions of responses. III. Current Actions Type of... Outcomes, Extension Without Revisions AGENCY: Employment and Training Administration (ETA), Labor....

  18. The Mechanisms and Spatiotemporal Behavior of the 2011 Mw7.1 Van, Eastern Turkey Earthquake Aftershocks

    NASA Astrophysics Data System (ADS)

    Ezgi Guvercin Isik, Sezim; Ozgun Konca, A.; Karabulut, Hayrullah

    2016-04-01

    We studied the mechanisms and spatiotemporal distribution of the aftershocks of the Mw7.1 Van Earthquake, in Eastern Turkey. The 2011 Van Earthquake occurred on a E-W trending blind thrust fault in Eastern Turkey which is under N-S compression due to convergence of the Arabian plate toward the Eurasia. In this study, we relocated and studied the mechanisms of the M3.5-5.5 aftershocks from regional Pnl and surface waves using the "Cut and Paste" algorithm of Zhu and Helmberger (1996). Our results reveal that the aftershocks in the first day following the mainshock are in the vicinity of the co-seismic slip and have mostly thrust mechanism consistent with the mainshock. In the following day, a second cluster of activity at the northeast termination of the fault ( North of Lake Erçek) has started. These aftershocks have approximately N-S lineation and left lateral source mechanisms. The aftershocks surrounding the mainshock rupture are deeper (>20 km) than the aftershocks triggered on the north (<15km). We also observe strike slip earthquakes on the south of the mainshock. Both of delayed activities (north of the mainshock and south of the mainshock) are consistent with the Coulomb stress increase due to slip on the mainshock. We propose that the Van Fault is truncated by two strike-slip faults at each end, which has determined the along-strike rupture extent of the 2011 mainshock.

  19. Aftershock seismicity and tectonic setting of the 16 September 2015 Mw 8.3 Illapel earthquake, Central Chile

    NASA Astrophysics Data System (ADS)

    Lange, Dietrich; Geersen, Jacob; Barrientos, Sergio; Moreno, Marcos; Grevemeyer, Ingo; Contreras-Reyes, Eduardo; Kopp, Heidrun

    2016-06-01

    Powerful subduction zone earthquakes rupture thousands of square kilometers along continental margins but at certain locations earthquake rupture terminates. To date detailed knowledge of the parameters that govern seismic rupture and aftershocks is still incomplete. On 16 September 2015 the Mw. 8.3 Illapel earthquake ruptured a 200 km long stretch of the Central Chilean subduction zone, triggering a tsunami and causing significant damage. Here we analyze the temporal and spatial pattern of the co-seismic rupture and aftershocks in relation to the tectonic setting in the earthquake area. Aftershocks cluster around the area of maximum coseismic slip, in particular in lateral and downdip direction. During the first 24 hours after the mainshock, aftershocks migrated in both lateral directions with velocities of approximately 2.5 and 5 km/h. At the southern rupture boundary aftershocks cluster around individual subducted seamounts that are related to the downthrusting Juan Fernández Ridge. In the northern part of the rupture area aftershocks separate into an upper cluster (above 25 km depth) and a lower cluster (below 35 km depth). This dual seismic-aseismic transition in downdip direction is also observed in the interseismic period suggesting that it may represent a persistent feature for the Central Chilean subduction zone.

  20. Aftershocks of the 2010 Mw 7.2 El Mayor-Cucapah earthquake revealcomplex faulting in the Yuha Desert, California

    USGS Publications Warehouse

    Kroll, K.; Cochran, Elizabeth S.; Richards-Dinger, K.; Sumy, Danielle

    2013-01-01

    We detect and precisely locate over 9500 aftershocks that occurred in the Yuha Desert region during a 2 month period following the 4 April 2010 Mw 7.2 El Mayor-Cucapah (EMC) earthquake. Events are relocated using a series of absolute and relative relocation procedures that include Hypoinverse, Velest, and hypoDD. Location errors are reduced to ~40 m horizontally and ~120 m vertically.Aftershock locations reveal a complex pattern of faulting with en echelon fault segments trending toward the northwest, approximately parallel to the North American-Pacific plate boundary and en echelon, conjugate features trending to the northeast. The relocated seismicity is highly correlated with published surface mapping of faults that experienced triggered surface slip in response to the EMC main shock. Aftershocks occurred between 2 km and 11 km depths, consistent with previous studies of seismogenic thickness in the region. Three-dimensional analysis reveals individual and intersecting fault planes that are limited in their along-strike length. These fault planes remain distinct structures at depth, indicative of conjugate faulting, and do not appear to coalesce onto a throughgoing fault segment. We observe a complex spatiotemporal migration of aftershocks, with seismicity that jumps between individual fault segments that are active for only a few days to weeks. Aftershock rates are roughly consistent with the expected earthquake production rates of Dieterich (1994). The conjugate pattern of faulting and nonuniform aftershock migration patterns suggest that strain in the Yuha Desert is being accommodated in a complex manner.

  1. Aftershock seismicity and tectonic setting of the 2015 September 16 Mw 8.3 Illapel earthquake, Central Chile

    NASA Astrophysics Data System (ADS)

    Lange, Dietrich; Geersen, Jacob; Barrientos, Sergio; Moreno, Marcos; Grevemeyer, Ingo; Contreras-Reyes, Eduardo; Kopp, Heidrun

    2016-08-01

    Powerful subduction zone earthquakes rupture thousands of square kilometres along continental margins but at certain locations earthquake rupture terminates. To date, detailed knowledge of the parameters that govern seismic rupture and aftershocks is still incomplete. On 2015 September 16, the Mw 8.3 Illapel earthquake ruptured a 200 km long stretch of the Central Chilean subduction zone, triggering a tsunami and causing significant damage. Here, we analyse the temporal and spatial pattern of the coseismic rupture and aftershocks in relation to the tectonic setting in the earthquake area. Aftershocks cluster around the area of maximum coseismic slip, in particular in lateral and downdip direction. During the first 24 hr after the main shock, aftershocks migrated in both lateral directions with velocities of approximately 2.5 and 5 km hr-1. At the southern rupture boundary, aftershocks cluster around individual subducted seamounts that are related to the downthrusting Juan Fernández Ridge. In the northern part of the rupture area, aftershocks separate into an upper cluster (above 25 km depth) and a lower cluster (below 35 km depth). This dual seismic-aseismic transition in downdip direction is also observed in the interseismic period suggesting that it may represent a persistent feature for the Central Chilean subduction zone.

  2. The 2008 Mw 6.0 Wells, Nevada Earthquake Sequence

    NASA Astrophysics Data System (ADS)

    Smith, K.; Depolo, D.; Torrisi, J.; Edwards, N.; Biasi, G.; Slater, D.

    2008-12-01

    The Mw 6.0 February 21, 2008 (06:16 AM PDT) Wells, Nevada normal faulting earthquake occurred in Town Creek Flat about 8 km northeast of the small community of Wells. A preliminary set of about 1000 aftershock relocations clearly defines a 55-60 degree southeast dipping fault plane. The structure projects to the surface along the southern end of the Snake Range, although no surface offsets have been identified. The earthquake occurred east of the Ruby Mountains and Snake Range west dipping range front faults, possibly on a northern extension of an east dipping normal fault system on the eastern side of the East Humbolt Range. The depth of the mainshock is estimated to be 10.5 km with the aftershock sequence extending to about 15 km. Typical of moderate sized Basin and Range earthquakes, the early aftershock period included several earthquakes of M > 4 and these were felt strongly by the residents of Wells. From the preliminary relocations, the source radius of the mainshock is estimated to be about 4 km, resulting in an estimated displacement of 55 to 83 cm and static stress drop of 72 to 86 bars, depending on the seismic moment estimate used. Aftershock relocations suggest a radial rupture mechanism. Fortunately, the EarthScope USArray network was operating in Nevada at the time of the event and provided unique controls on the mainshock and early aftershock locations. The earthquake occurred in an area of relatively low seismic hazard and the only permanent seismograph in the region was the U.S. National Network broadband station east of the Ruby Mountains south of Wells. The University of Utah and University of Nevada deployed locally recorded strong motion instruments in the Wells area. Also, an 8 station IP telemetered strong motion network, jointly deployed by the U.S. Geological Survey and University of Nevada Reno, provided real-time data for quick high-quality aftershock relocations and ground motion estimates. In addition, the University of Utah

  3. Comparison between Utsu's and Vere-Jones' aftershocks model by means of a computer simulation based on the acceptance-rejection sampling of von Neumann

    NASA Astrophysics Data System (ADS)

    Reyes, J.; Morales-Esteban, A.; González, E.; Martínez-Álvarez, F.

    2016-07-01

    In this research, a new algorithm for generating a stochastic earthquake catalog is presented. The algorithm is based on the acceptance-rejection sampling of von Neumann. The result is a computer simulation of earthquakes based on the calculated statistical properties of each zone. Vere-Jones states that an earthquake sequence can be modeled as a series of random events. This is the model used in the proposed simulation. Contrariwise, Utsu indicates that the mainshocks are special geophysical events. The algorithm has been applied to zones of Chile, China, Spain, Japan, and the USA. This allows classifying the zones according to Vere-Jones' or Utsu's model. The results have been quantified relating the mainshock with the largest aftershock within the next 5 days (which has been named as Bath event). The results show that some zones fit Utsu's model and others Vere-Jones'. Finally, the fraction of seismic events that satisfy certain properties of magnitude and occurrence is analyzed.

  4. [Ti II] and [Ni II] Emission from the Strontium Filament of eta Carinae

    NASA Technical Reports Server (NTRS)

    Bautista, M. A.; Hartman, H.; Gull, T. R.; Smith, N.; Lodders, K.

    2005-01-01

    We study the nature of the [Ti II] and [Ni II] emission from the so-called strontium filament found in the ejecta of eta Carinae. To this purpose we employ multilevel models of the Ti II and Ni II systems which are used to investigate the physical condition of the filament and the excitation mechanisms of the observed lines. For the Ti II ion, for which no atomic data was previously available, we carry out ab initio calculations of radiative transition rates and electron impact excitation rate coefficients. It is found that the observed spectrum is consistent with the lines being excited in a mostly neutral region with electron density of the order of 10(exp 7) cm(exp -3) and a temperature around 6000 K. In analyzing three observations with different slit orientations recorded between March 2000 and November 2001 we find line ratios that change among various observations, in a way consistent with changes of up to an order of magnitude in the strength of the continuum radiation field. These changes result from different samplings of the extended filament, due to the different slit orientations used for each observation, and yield clues on the spatial extent and optical depth of the filament. The observed emission indicates a large Ti/Ni abundance ratio relative to solar abundances. It is suggested that the observed high Ti/Ni ratio in gas is caused dust-gas fractionation processes and does not reflect the absolute Ti/Ni ratio in the ejecta of eta Carinae. The condensation chemistry shows that if dust condensed in a sequence of layers according to decreasing temperature and increasing distance from the central star, the most refractory dust could be selectively affected by photoevaporation. Thus, Ti would be released back to the gas and the Ti/Ni ratio in the gas would increase to the observed super-solar ratio.

  5. Measurements of the mass and width of the eta(c) meson and of an eta(c)(2S) candidate.

    PubMed

    Aubert, B; Barate, R; Boutigny, D; Gaillard, J-M; Hicheur, A; Karyotakis, Y; Lees, J P; Robbe, P; Tisserand, V; Zghiche, A; Palano, A; Pompili, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Borgland, A W; Breon, A B; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Day, C T; Gill, M S; Gritsan, A V; Groysman, Y; Jacobsen, R G; Kadel, R W; Kadyk, J; Kerth, L T; Kolomensky, Yu G; Kral, J F; Kukartsev, G; LeClerc, C; Levi, M E; Lynch, G; Mir, L M; Oddone, P J; Orimoto, T J; Pripstein, M; Roe, N A; Romosan, A; Ronan, M T; Shelkov, V G; Telnov, A V; Wenzel, W A; Ford, K; Harrison, T J; Hawkes, C M; Knowles, D J; Morgan, S E; Penny, R C; Watson, A T; Watson, N K; Deppermann, T; Goetzen, K; Koch, H; Lewandowski, B; Pelizaeus, M; Peters, K; Schmuecker, H; Steinke, M; Barlow, N R; Boyd, J T; Chevalier, N; Cottingham, W N; Kelly, M P; Latham, T E; Mackay, C; Wilson, F F; Abe, K; Cuhadar-Donszelmann, T; Hearty, C; Mattison, T S; McKenna, J A; Thiessen, D; Kyberd, P; McKemey, A K; Blinov, V E; Bukin, A D; Golubev, V B; Ivanchenko, V N; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Yushkov, A N; Best, D; Bruinsma, M; Chao, M; Kirkby, D; Lankford, A J; Mandelkern, M; Mommsen, R K; Roethel, W; Stoker, D P; Buchanan, C; Hartfiel, B L; Shen, B C; Del Re, D; Hadavand, H K; Hill, E J; MacFarlane, D B; Paar, H P; Rahatlou, Sh; Schwanke, U; Sharma, V; Berryhill, J W; Campagnari, C; Dahmes, B; Kuznetsova, N; Levy, S L; Long, O; Lu, A; Mazur, M A; Richman, J D; Verkerke, W; Beck, T W; Beringer, J; Eisner, A M; Heusch, C A; Lockman, W S; Schalk, T; Schmitz, R E; Schumm, B A; Seiden, A; Turri, M; Walkowiak, W; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dubois-Felsmann, G P; Dvoretskii, A; Hitlin, D G; Narsky, I; Porter, F C; Ryd, A; Samuel, A; Yang, S; Jayatilleke, S; Mancinelli, G; Meadows, B T; Sokoloff, M D; Abe, T; Blanc, F; Bloom, P; Chen, S; Clark, P J; Ford, W T; Nauenberg, U; Olivas, A; Rankin, P; Roy, J; Smith, J G; Van Hoek, W C; Zhang, L; Harton, J L; Hu, T; Soffer, A; Toki, W H; Wilson, R J; Zhang, J; Altenburg, D; Brandt, T; Brose, J; Colberg, T; Dickopp, M; Dubitzky, R S; Hauke, A; Lacker, H M; Maly, E; Müller-Pfefferkorn, R; Nogowski, R; Otto, S; Schubert, J; Schubert, K R; Schwierz, R; Spaan, B; Wilden, L; Bernard, D; Bonneaud, G R; Brochard, F; Cohen-Tanugi, J; Grenier, P; Thiebaux, Ch; Vasileiadis, G; Verderi, M; Khan, A; Lavin, D; Muheim, F; Playfer, S; Swain, J E; Tinslay, J; Andreotti, M; Azzolini, V; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Piemontese, L; Sarti, A; Treadwell, E; Anulli, F; Baldini-Ferroli, R; Biasini, M; Calcaterra, A; De Sangro, R; Falciai, D; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Pioppi, M; Zallo, A; Buzzo, A; Capra, R; Contri, R; Crosetti, G; Lo Vetere, M; Macri, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Bailey, S; Morii, M; Won, E; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Eschrich, I; Gaillard, J R; Morton, G W; Nash, J A; Sanders, P; Taylor, G P; Grenier, G J; Lee, S-J; Mallik, U; Cochran, J; Crawley, H B; Lamsa, J; Meyer, W T; Prell, S; Rosenberg, E I; Yi, J; Davier, M; Grosdidier, G; Höcker, A; Laplace, S; Le Diberder, F; Lepeltier, V; Lutz, A M; Petersen, T C; Plaszczynski, S; Schune, M H; Tantot, L; Wormser, G; Brigljević, V; Cheng, C H; Lange, D J; Wright, D M; Bevan, A J; Coleman, J P; Fry, J R; Gabathuler, E; Gamet, R; Kay, M; Parry, R J; Payne, D J; Sloane, R J; Touramanis, C; Back, J J; Harrison, P F; Shorthouse, H W; Strother, P; Vidal, P B; Brown, C L; Cowan, G; Flack, R L; Flaecher, H U; George, S; Green, M G; Kurup, A; Marker, C E; McMahon, T R; Ricciardi, S; Salvatore, F; Vaitsas, G; Winter, M A; Brown, D; Davis, C L; Allison, J; Barlow, R J; Forti, A C; Hart, P A; Jackson, F; Lafferty, G D; Lyon, A J; Weatherall, J H; Williams, J C; Farbin, A; Jawahery, A; Kovalskyi, D; Lae, C K; Lillard, V; Roberts, D A; Blaylock, G; Dallapiccola, C; Flood, K T; Hertzbach, S S; Kofler, R; Koptchev, V B; Moore, T B; Saremi, S; Staengle, H; Willocq, S; Cowan, R; Sciolla, G; Taylor, F; Yamamoto, R K; Mangeol, D J J; Milek, M; Patel, P M; Lazzaro, A; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Reidy, J; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Cote-Ahern, D; Hast, C; Taras, P; Nicholson, H; Cartaro, C; Cavallo, N; De Nardo, G; Fabozzi, F; Gatto, C; Lista, L; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M A; Raven, G; LoSecco, J M; Gabriel, T A; Brau, B; Gan, K K; Honscheid, K; Hufnagel, D; Kagan, H; Kass, R; Pulliam, T; Wong, Q K; Brau, J; Frey, R; Potter, C T; Sinev, N B; Strom, D; Torrence, E; Colecchia, F; Dorigo, A; Galeazzi, F; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Tiozzo, G; Voci, C; Benayoun, M; Briand, H; Chauveau, J; David, P; de la Vaissière, Ch; Del Buono, L; Hamon, O; John, M J J; Leruste, Ph; Ocariz, J; Pivk, M; Roos, L; Stark, J; T'Jampens, S; Therin, G; Manfredi, P F; Re, V; Behera, P K; Gladney, L; Guo, Q H; Panetta, J; Angelini, C; Batignani, G; Bettarini, S; Bondioli, M; Bucci, F; Calderini, G; Carpinelli, M; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Martinez-Vidal, F; Morganti, M; Neri, N; Paoloni, E; Rama, M; Rizzo, G; Sandrelli, F; Walsh, J; Haire, M; Judd, D; Paick, K; Wagoner, D E; Danielson, N; Elmer, P; Lu, C; Miftakov, V; Olsen, J; Smith, A J S; Tanaka, H A; Varnes, E W; Bellini, F; Cavoto, G; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Mazzoni, M A; Morganti, S; Pierini, M; Piredda, G; Safai Tehrani, F; Voena, C; Christ, S; Wagner, G; Waldi, R; Adye, T; De Groot, N; Franek, B; Geddes, N I; Gopal, G P; Olaiya, E O; Xella, S M; Aleksan, R; Emery, S; Gaidot, A; Ganzhur, S F; Giraud, P-F; Hamel de Monchenault, G; Kozanecki, W; Langer, M; Legendre, M; London, G W; Mayer, B; Schott, G; Vasseur, G; Yeche, Ch; Zito, M; Purohit, M V; Weidemann, A W; Yumiceva, F X; Aston, D; Bartoldus, R; Berger, N; Boyarski, A M; Buchmueller, O L; Convery, M R; Coupal, D P; Dong, D; Dorfan, J; Dujmic, D; Dunwoodie, W; Field, R C; Glanzman, T; Gowdy, S J; Grauges-Pous, E; Hadig, T; Halyo, V; Hryn'ova, T; Innes, W R; Jessop, C P; Kelsey, M H; Kim, P; Kocian, M L; Langenegger, U; Leith, D W G S; Luitz, S; Luth, V; Lynch, H L; Marsiske, H; Messner, R; Muller, D R; O'Grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Petrak, S; Ratcliff, B N; Robertson, S H; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Simi, G; Snyder, A; Soha, A; Stelzer, J; Su, D; Sullivan, M K; Va'vra, J; Wagner, S R; Weaver, M; Weinstein, A J R; Wisniewski, W J; Wright, D H; Young, C C; Burchat, P R; Edwards, A J; Meyer, T I; Petersen, B A; Roat, C; Ahmed, S; Alam, M S; Ernst, J A; Saleem, M; Wappler, F R; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Kim, H; Ritchie, J L; Schwitters, R F; Izen, J M; Kitayama, I; Lou, X C; Ye, S; Bianchi, F; Bona, M; Gallo, F; Gamba, D; Borean, C; Bosisio, L; Della Ricca, G; Dittongo, S; Grancagnolo, S; Lanceri, L; Poropat, P; Vitale, L; Vuagnin, G; Panvini, R S; Banerjee, Sw; Brown, C M; Fortin, D; Jackson, P D; Kowalewski, R; Roney, J M; Band, H R; Dasu, S; Datta, M; Eichenbaum, A M; Johnson, J R; Kutter, P E; Li, H; Liu, R; Di Lodovico, F; Mihalyi, A; Mohapatra, A K; Pan, Y; Prepost, R; Sekula, S J; von Wimmersperg-Toeller, J H; Wu, J; Wu, S L; Yu, Z; Neal, H

    2004-04-01

    The mass m(eta(c)) and total width Gamma(eta(c))(tot) of the eta(c) meson have been measured in two-photon interactions at the SLAC e(+)e(-) asymmetric B Factory with the BABAR detector. With a sample of approximately 2500 reconstructed eta(c)-->K(0)(S)K+/-pi(-/+) decays in 88 fb(-1) of data, the results are m(eta(c))=2982.5+/-1.1(stat)+/-0.9(syst) MeV/c(2) and Gamma(eta(c))(tot)=34.3+/-2.3(stat)+/-0.9(syst) MeV/c(2). Using the same decay mode, a second resonance with 112+/-24 events is observed with a mass of 3630.8+/-3.4(stat)+/-1.0(syst) MeV/c(2) and width of 17.0+/-8.3(stat)+/-2.5(syst) MeV/c(2). This observation is consistent with expectations for the eta(c)(2S) state.

  6. Real-time forecast of aftershocks from a single seismic station signal

    NASA Astrophysics Data System (ADS)

    Lippiello, E.; Cirillo, A.; Godano, G.; Papadimitriou, E.; Karakostas, V.

    2016-06-01

    The evaluation of seismic hazard in the hours following large earthquakes is strongly affected by biases due to difficulties in determining earthquake location. This leads to the huge incompleteness of instrumental catalogs. Here we show that if, on the one hand, the overlap of aftershock coda waves hides many small events, on the other hand, it leads to a well-determined empirical law controlling the decay of the amplitude of the seismic signal at a given site. The fitting parameters of this law can be related to those controlling the temporal decay of the aftershock number, and it is then possible to obtain short-term postseismic occurrence probability from a single recorded seismic signal. We therefore present a novel procedure which, without requiring earthquake location, produces more accurate and almost real-time forecast, in a site of interest, directly from the signal of a seismic station installed at that site.

  7. Urban seismology - Northridge aftershocks recorded by multi-scale arrays of portable digital seismographs

    USGS Publications Warehouse

    Meremonte, M.; Frankel, A.; Cranswick, E.; Carver, D.; Worley, D.

    1996-01-01

    We deployed portable digital seismographs in the San Fernando Valley (SFV), the Los Angeles basin (LAB), and surrounding hills to record aftershocks of the 17 January 1994 Northridge California earthquake. The purpose of the deployment was to investigate factors relevant to seismic zonation in urban areas, such as site amplification, sedimentary basin effects, and the variability of ground motion over short baselines. We placed seismographs at 47 sites (not all concurrently) and recorded about 290 earthquakes with magnitudes up to 5.1 at five stations or more. We deployed widely spaced stations for profiles across the San Fernando Valley, as well as five dense arrays (apertures of 200 to 500 m) in areas of high damage, such as the collapsed Interstate 10 overpass, Sherman Oaks, and the collapsed parking garage at CalState Northridge. Aftershock data analysis indicates a correlation of site amplification with mainshock damage. We found several cases where the site amplification depended on the azimuth of the aftershock, possibly indicating focusing from basin structures. For the parking garage array, we found large ground-motion variabilities (a factor of 2) over 200-m distances for sites on the same mapped soil unit. Array analysis of the aftershock seismograms demonstrates that sizable arrivals after the direct 5 waves consist of surface waves traveling from the same azimuth as that of the epicenter. These surface waves increase the duration of motions and can have frequencies as high as about 4 Hz. For the events studied here, we do not observe large arrivals reflected from the southern edge of the San Fernando Valley.

  8. Search for {psi}(2S){yields}{gamma}{eta}{sub c}(2S) via fully reconstructed {eta}{sub c}(2S) decays

    SciTech Connect

    Cronin-Hennessy, D.; Gao, K. Y.; Gong, D. T.; Hietala, J.; Kubota, Y.; Klein, T.; Poling, R.; Zweber, P.; Dobbs, S.; Metreveli, Z.; Seth, K. K.; Tan, B. J. Y.; Tomaradze, A.; Libby, J.; Martin, L.; Powell, A.; Thomas, C.; Wilkinson, G.; Mendez, H.; Ge, J. Y.

    2010-03-01

    We report a search for the decay {psi}(2S){yields}{gamma}{eta}{sub c}(2S) in a sample of 25.9x10{sup 6} {psi}(2S) events collected with the CLEO-c detector. No signals are observed in any of the 11 exclusive {eta}{sub c}(2S) decay modes studied, or in their sum. Product branching fraction upper limits are determined as a function of {Gamma}[{eta}{sub c}(2S)] for the 11 individual modes.

  9. Aftershocks of the western Argentina (Caucete) earthquake of 23 November 1977: some tectonic implications

    USGS Publications Warehouse

    Langer, C.J.; Bollinger, G.A.

    1988-01-01

    An aftershock survey, using a network of eight portable and two permanent seismographs, was conducted for the western Argentina (Caucete) earthquake (MS 7.3) of November 23, 1977. Monitoring began December 6, almost 2 weeks after the main shock and continued for 11 days. The data set includes 185 aftershock hypocenters that range in the depth from near surface to more than 30 km. The spatial distribution of those events occupied a volume of about 100 km long ??50 km wide ??30 km thick. The volumnar nature of the aftershock distribution is interpreted to be a result of a bimodal distribution of foci that define east- and west-dipping planar zones. Efforts to select which of those zones was associated with the causal faulting include special attention to the determination of the mainshock focal depth and dislocation theory modeling of the coseismic surface deformation in the epicentral region. Our focal depth (25-35 km) and modeling studies lead us to prefer an east-dipping plane as causal. A previous interpretation by other investigators used a shallower focal depth (17 km) and similar modeling calculations in choosing a west-dipping plane. Our selection of the east-dipping plane is physically more appealing because it places fault initiation at the base of the crustal seismogenic layer (rather than in the middle of that layer) which requires fault propagation to be updip (rather than downdip). ?? 1988.

  10. Applying Error Diagram for Evaluating Spatial Forecasting Model of Large Aftershocks

    NASA Astrophysics Data System (ADS)

    Shebalin, Peter; Sergey, Baranov

    2016-04-01

    Difficulty of use in practice the forecasting result formulated in probability terms is well known in statistical seismology. Small values of probability of earthquake occurrence cannot be directly used for decision making to reduce losses due to seismic hazard. In this research we suggest a technique for applying Molchan's error diagram to evaluate a model of seismic hazard forecasting and make practical recommendation, applied specifically to the hazard after large earthquakes. We illustrate the suggested technique by example of evaluating retrospective forecast of an area where one can expect strong aftershock (M6+). The forecast model is based on data for 12 hours after the mainshock. We found an optimal variant among many tested by minimizing the rate of missed targets (strong aftershock) and the rate of alarm space as a loss function. Analyzing the error diagram, we suggest these three forecast strategies: "soft", "neutral", and 'hard", giving different size of the alarm area, where one may expect strong aftershocks. The suggested technique can be used for making decision at various conditions to reduce losses due to seismic hazard after a strong earthquake. This research was carried out at the expense of the Russian Science Foundation (Project Nu 16-17-00093).

  11. Main shock and aftershock records of the 1999 Izmit and Duzce, Turkey earthquakes

    USGS Publications Warehouse

    Celebi, M.; Akkar, Sinan; Gulerce, U.; Sanli, A.; Bundock, H.; Salkin, A.

    2001-01-01

    The August 17, 1999 Izmit (Turkey) earthquake (Mw=7.4) will be remembered as one of the largest earthquakes of recent times that affected a large urban environment (U.S. Geological Survey, 1999). This significant event was followed by many significant aftershocks and another main event (Mw=7.2) that occurred on November 12, 1999 near Duzce (Turkey). The shaking that caused the widespread damage and destruction was recorded by a handful of accelerographs (~30) in the earthquake area operated by different networks. The characteristics of these records show that the recorded peak accelerations, shown in Figure 1, even those from near field stations, are smaller than expected (Çelebi, 1999, 2000). Following this main event, several organizations from Turkey, Japan, France and the USA deployed temporary accelerographs and other aftershock recording hardware. Thus, the number of recording stations in the earthquake affected area was quadrupled (~130). As a result, as seen in Figure 2, smaller magnitude aftershocks yielded larger peak accelerations, indicating that because of the sparse networks, recording of larger motions during the main shock of August 17, 1999 were possibly missed.

  12. Eta Carinae, the Integral Nebula and the Homunculus Observations

    NASA Astrophysics Data System (ADS)

    Gull, Theodore

    2000-07-01

    In the past two years, observations of Eta Carina have revealed much new and very exciting information. Augusto Damineli noted a 5.5 year period in the visible and near infrared spectroscopy. Michael Corcoran and Bish Ishibashi noticed modulation of the x-ray fluxes with various periodicities around 90 days before and after the xray and radio minimum in December 1997. Observations, done in March 1998 under proposal 7302 {Davidson et al} from 1640A to 10400A using STIS in GXXXM mode and the 50x0.1 arcsecond slit, revealed much new information in the immediate regions of Eta Carina. The slit orientation was slightly off the major axis of the Homunculus, but passed through Weigelt components B and D. Bish Ishibashi and Ted Gull have reduced the data and provided it to various team members. Torgil Zethson has identified well over 90 percent of the emission lines in the March 1998 spectrum and finds most to be FeII emission lines. Based upon the past ground-based history of Eta Carina, we expected that FeIII and other high ionization states would return within the year. STIS GTO observations {Ted Gull, PI program 8036} characterized a bright internal emission nebula by turning the slit 90 degrees for visit 1 and studying the changes in spectrum as the FeIII lines appear by using visit 2 with the identical slit orientation from March 19, 1998. Data from the four visits of STIS to Eta Carinae between December 1997 and February 1999 demonstrate that the star has brightened by a factor of two during that interval and that the immediate nebulosity has tripled in surface brightness. Moreover a small circular nebular shell, seen in multiple [Fe II] lines has disappeared and the opacity in the 2000 to 3000A region obscuring the star has lifted considerable as the Fe II is converting to Fe III. Given the strong changes in the spectrum, we have chosen to use the six orbits in two visits. Visit 1 will be a precise repeat of the March 1998 and February 1999 observations, adjusted

  13. Nebular Hydrogen Absorption in the Ejecta of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Gull, Theodore R.; Ishibashi, K.; Davidson, K.; Fisher, Richard R. (Technical Monitor)

    2000-01-01

    Space Telescope Imaging Spectrograph (STIS) observations of Eta Carinae and immediate ejecta reveal narrow Balmer absorption lines in addition to the nebular-scattered broad P-Cygni absorptions. The narrow absorption correlates with apparent disk structure that separates the two Homunculus lobes. We trace these features about half way up the Northern lobe until the scattered stellar Balmer line doppler-shifts redward beyond the nebular absorption feature. Three-dimensional data cubes, made by mapping the Homunculus at Balmer alpha and Balmer beta with the 52 x 0.1 arcsecond aperture and about 5000 spectral resolving power, demonstrate that the absorption feature changes slowly in velocity with nebular position. We have monitored the stellar Balmer alpha line profile of the central source over the past four years. The equivalent width of the nebular absorption feature changes considerably between observations. The changes do not correlate with measured brightness of Eta Carinae. Likely clumps of neutral hydrogen with a scale size comparable to the stellar disk diameter are passing through the intervening light path on the timescales less than several months. The excitation mechanism involves Lyman alpha radiation (possibly the Lyman series plus Lyman continuum) and collisions leading to populating the 2S metastable state. Before the electron can jump to the ground state by two photon emission (lifetime about 1/8 second), a stellar Balmer photon is absorbed and the electron shifts to an NP level. We see the absorption feature in higher Balmer lines, and but not in Paschen lines. Indeed we see narrow nebular Paschen emission lines. At present, we do not completely understand the details of the absorption. Better understanding should lead to improved insight of the unique conditions around Eta Carinae that leads to these absorptions.

  14. UV nebular absorption in Eta Car and Weigelt D

    NASA Astrophysics Data System (ADS)

    Nielsen, K. E.; Vieira, G. L.; Gull, T. R.; Lindler, D. J.; Eta Car HST Treasury Team

    2003-12-01

    The high angular and high spectral resolution of the HST/STIS MAMA echelle mode, provide an unique means to distinguish the physical structures surrounding Eta Car. Observations are parts of the HST treasury program (K. Davidson P.I.) for monitoring variations over Eta Car's spectroscopic minimum. Nebular emission is present above and below the stellar spectrum which is about 0.03'' wide. We have extracted the nebular part of the central source spectrum and compared it with the spectrum of Weigelt D, located approximately 0.2'' Northwest of the central source. The spectra show significant similarities and our conclusions are two-fold. First, the radiation from the Wiegelt blobs give an unwanted contribution to the spectrum of the central source, which emphasizes the importance of using an extracted spectrum in a spectral analysis. Second, the Weigelt blobs have so far been assumed to produce a pure emission line spectrum. However, this comparison shows the presence of similar absorption structures previously observed in the spectrum of the central star (Gull et al., 2003, submitted ApJL). Two velocity structures at approximately -50 and -500 km/s, respectively, have been observed in the Weigelt D spectrum. We present identifications of the absorption structures to supplement the emission line work performed by T. Zethson (2000, PhD Thesis) and provide additional information regarding the geometry of the inner parts of the Eta Car nebula. The -50 km/s velocity component is similar to the absorption structure at -146 km/s observed in the spectrum of the central object. If these velocity systems are related, this implies that the absorption component is located close to the central parts of the nebular system.

  15. THE LONG-LIVED DISKS IN THE {eta} CHAMAELEONTIS CLUSTER

    SciTech Connect

    Sicilia-Aguilar, Aurora; Bouwman, Jeroen; Juhasz, Attila; Henning, Thomas; Roccatagliata, Veronica; Lawson, Warrick A.; Acke, Bram; Decin, Leen; Feigelson, Eric D.; Tielens, A. G. G. M.; Meeus, Gwendolyn

    2009-08-20

    We present Infrared Spectrograph spectra and revised Multiband Imaging Photometer photometry for the 18 members of the {eta} Chamaeleontis cluster. Aged 8 Myr, the {eta} Cha cluster is one of the few nearby regions within the 5-10 Myr age range, during which the disk fraction decreases dramatically and giant planet formation must come to an end. For the 15 low-mass members, we measure a disk fraction {approx}50%, high for their 8 Myr age, and four of the eight disks lack near-IR excesses, consistent with the empirical definition of 'transition' disks. Most of the disks are comparable to geometrically flat disks. The comparison with regions of different ages suggests that at least some of the 'transition' disks may represent the normal type of disk around low-mass stars. Therefore, their flattened structure and inner holes may be related to other factors (initial masses of the disk and the star, environment, binarity), rather than to pure time evolution. We analyze the silicate dust in the disk atmosphere, finding moderate crystalline fractions ({approx}10%-30%) and typical grain sizes {approx}1-3 {mu}m, without any characteristic trend in the composition. These results are common to other regions of different ages, suggesting that the initial grain processing occurs very early in the disk lifetime (<1 Myr). Large grain sizes in the disk atmosphere cannot be used as a proxy for age, but are likely related to higher disk turbulence. The dust mineralogy varies between the 8-12 {mu}m and the 20-30 {mu}m features, suggesting high temperature dust processing and little radial mixing. Finally, the analysis of IR and optical data on the B9 star {eta} Cha reveals that it is probably surrounded by a young debris disk with a large inner hole, instead of being a classical Be star.

  16. Implementation of an Eta Belt Domain on Parallel Systems

    NASA Technical Reports Server (NTRS)

    Kouatchou, Jules; Rancic, Miodrag; Norris, Peter; Geiger, Jim

    2001-01-01

    We extend the Eta weather model from a regional domain into a belt domain that does not require meridional boundary conditions. We describe how the extension is achieved and the parallel implementation of the code on the Cray T3E and the SGI Origin 2000. We validate the forecast results on the two platforms and examine how the removal of the meridional boundary conditions affects these forecasts. In addition, using several domains of different sizes and resolutions, we present the scaling performance of the code on both systems.

  17. Eta Carinae in the Context of the Most Massive Stars

    NASA Technical Reports Server (NTRS)

    Gull, Theodore R.; Damineli, Augusto

    2009-01-01

    Eta Car, with its historical outbursts, visible ejecta and massive, variable winds, continues to challenge both observers and modelers. In just the past five years over 100 papers have been published on this fascinating object. We now know it to be a massive binary system with a 5.54-year period. In January 2009, Car underwent one of its periodic low-states, associated with periastron passage of the two massive stars. This event was monitored by an intensive multi-wavelength campaign ranging from -rays to radio. A large amount of data was collected to test a number of evolving models including 3-D models of the massive interacting winds. August 2009 was an excellent time for observers and theorists to come together and review the accumulated studies, as have occurred in four meetings since 1998 devoted to Eta Car. Indeed, Car behaved both predictably and unpredictably during this most recent periastron, spurring timely discussions. Coincidently, WR140 also passed through periastron in early 2009. It, too, is a intensively studied massive interacting binary. Comparison of its properties, as well as the properties of other massive stars, with those of Eta Car is very instructive. These well-known examples of evolved massive binary systems provide many clues as to the fate of the most massive stars. What are the effects of the interacting winds, of individual stellar rotation, and of the circumstellar material on what we see as hypernovae/supernovae? We hope to learn. Topics discussed in this 1.5 day Joint Discussion were: Car: the 2009.0 event: Monitoring campaigns in X-rays, optical, radio, interferometry WR140 and HD5980: similarities and differences to Car LBVs and Eta Carinae: What is the relationship? Massive binary systems, wind interactions and 3-D modeling Shapes of the Homunculus & Little Homunculus: what do we learn about mass ejection? Massive stars: the connection to supernovae, hypernovae and gamma ray bursters Where do we go from here? (future

  18. Eta Carinae and the Homunculus: A Physics Laboratory

    NASA Technical Reports Server (NTRS)

    Gull, Theodore R.; Fisher, Richard R. (Technical Monitor)

    2002-01-01

    The Luminous Blue Variable, Eta Carinae, and its ejecta, thrown out since the 1840s, are proving to be a very challenging system to explain. The > 100 solar mass central source (which is likely a binary system) is very complex with P-Cygni lines throughout the spectrum. Superimposed upon the stellar spectrum are many thousands of narrow absorption lines. Indeed we have found twenty different velocities between -140km/s and -580km/s with many lower levels well elevated above the ground states of numerous ions.

  19. Identification of a novel Baeyer‐Villiger monooxygenase from Acinetobacter radioresistens: close relationship to the Mycobacterium tuberculosis prodrug activator EtaA

    PubMed Central

    Minerdi, Daniela; Zgrablic, Ivan; Sadeghi, Sheila J.; Gilardi, Gianfranco

    2012-01-01

    Summary This work demonstrates that Acinetobacter radioresistens strain S13 during the growth on medium supplemented with long‐chain alkanes as the sole energy source expresses almA gene coding for a Baeyer‐Villiger monooxygenase (BVMO) involved in alkanes subterminal oxidation. Phylogenetic analysis placed the sequence of this novel BVMO in the same clade of the prodrug activator ethionamide monooxygenase (EtaA) and it bears only a distant relation to the other known class I BVMO proteins. In silico analysis of the 3D model of the S13 BVMO generated by homology modelling also supports the similarities with EtaA by binding ethionamide to the active site. In vitro experiments carried out with the purified enzyme confirm that this novel BVMO is indeed capable of typical Baeyer‐Villiger reactions as well as oxidation of the prodrug ethionamide. PMID:22862894

  20. High-Resolution Uitra Low Power, Intergrated Aftershock and Microzonation System

    NASA Astrophysics Data System (ADS)

    Passmore, P.; Zimakov, L. G.

    2012-12-01

    Rapid Aftershock Mobilization plays an essential role in the understanding of both focal mechanism and rupture propagation caused by strong earthquakes. A quick assessment of the data provides a unique opportunity to study the dynamics of the entire earthquake process in-situ. Aftershock study also provides practical information for local authorities regarding the post earthquake activity, which is very important in order to conduct the necessary actions for public safety in the area affected by the strong earthquake. Refraction Technology, Inc. has developed a self-contained, fully integrated Aftershock System, model 160-03, providing the customer simple and quick deployment during aftershock emergency mobilization and microzonation studies. The 160-03 has no external cables or peripheral equipment for command/control and operation in the field. The 160-03 contains three major components integrated in one case: a) 24-bit resolution state-of-the art low power ADC with CPU and Lid interconnect boards; b) power source; and c) three component 2 Hz sensors (two horizontals and one vertical), and built-in ±4g accelerometer. Optionally, the 1 Hz sensors can be built-in the 160-03 system at the customer's request. The self-contained rechargeable battery pack provides power autonomy up to 7 days during data acquisition at 200 sps on continuous three weak motion and triggered three strong motion recording channels. For longer power autonomy, the 160-03 Aftershock System battery pack can be charged from an external source (solar power system). The data in the field is recorded to a built-in swappable USB flash drive. The 160-03 configuration is fixed based on a configuration file stored on the system, so no external command/control interface is required for parameter setup in the field. For visual control of the system performance in the field, the 160-03 has a built-in LED display which indicates the systems recording status as well as a hot swappable USB drive and battery

  1. Aftershock Seismicity of the 27 February 2010 Mw 8.8 Maule Earthquake Rupture Zone

    NASA Astrophysics Data System (ADS)

    Lange, D.; Tilmann, F. J.; Barrientos, S. E.; Bataille, K.; Beck, S. L.; Bernard, P.; Campos, J. A.; Comte, D.; Haberland, C. A.; Heit, B.; Methe, P.; Peyrat, S.; Rietbrock, A.; Roecker, S.; Schurr, B.; Vilotte, J.

    2010-12-01

    On 27 February 2010 the Mw 8.8 Maule earthquake in Central Chile ruptured a well known seismic gap, which last broke in 1835. Shortly after the mainshock Chilean agencies (UC Santiago, UC Concepción) and the international seismological community (USA (IRIS), France (IPGP), UK (University of Liverpool), Germany (GFZ)) installed a total of 142 portable seismic stations along the whole rupture zone in order to capture the aftershock activity. Here, we present the aftershock distribution based on automatic detection algorithms and picking engines (MPX; STA/LTA) which will be calibrated with a subset of manually picked events. Initial processing of 70 days of continuous data (20 March until 29 May 2010) from IRIS and GFZ stations resulted in the detection of well over 30,000 events. Of these, we consider a higher quality subset of 12,824 hypocentres based on more than 12 automatically picked P arrivals. Because picking errors can be large for the smaller arrivals, the depths of located events are not always reliable, particularly far from the coast. Nevertheless, a few first order features can be identified: 1.) A pronounced cluster of seismicity is apparent at 25-35 km depth and 50-120 km perpendicular distance from the trench (with some NS variation). 2.) A secondary band of seismicity can be identified at 40-50 km depth and ~150-160 km perpendicular trench distance and between 34° and 37°S. Although the secondary band lies along the continuation of the primary one, it is clearly separated from it by a gap with sparse seismicity. It is not yet possible to state whether these events occurred on the plate interface or in the downgoing plate. 3.) Intense crustal seismicity is found in the region of Pichilemu. This region hosted the strongest aftershock (Mw=6.9), a normal faulting event with NW strike. The aftershocks extend from the plate interface to the surface and are aligned on a NNW-SSE oriented band in map view. 4.) An isolated shallow cluster of crustal

  2. The Aftershock Analyses of 27 February 2010 Chile M=8.8 Mega Earthquake

    NASA Astrophysics Data System (ADS)

    Lee, C.-S.; Klingelhoefer, F.; Gutscher, M.; Miller, M.; Gallardo, V.

    2012-04-01

    In 1960, the biggest earthquake (M=9.5), the human ever recorded event, occurred in south Chile. Subsequently several mega earthquake (M >8) occurred, including the M=8.8 earthquake in 2010. This reflects that an incomplete release of tectonic energy exists in the Chile subduction system. The west coast of Chile is a long convergence plate boundary between the Nazca and the South American plate. The Nazca Plate subducts beneath the South American Plate toward the northeast with a convergence rate of about 6.5 cm/year, accumulating the stress in the lower part of the subducted plate to some extent resulting in destructive ruptures. On 27 February 2010, the Maule mega earthquake (M=8.8) occurred offshore central Chile. The epicenter (35.9° S, 72.73° W) is located at 115 km, NE of Concepción, the second biggest city in Chile. The main shock was a thrust-type subduction earthquake where the Nazca Plate subducted into the South America Plate (the Chile subduction system). The focal depth of main shock is 35 km which caused more than 500-km long rupture in the accretionary prism and produced a destructive tsunami of more than 20 m. It killed several hundreds of people and damaged countless buildings. Even up to today, aftershocks and volcanic activities continue to occur in this region. During May-August of last year, we shipped 20 OBSs to Chile and conducted two aftershock surveys in the tsunami-affected area. The OBSs recorded more than 4,000 aftershock events, magnitude from M=6.0 to 1.0. Results show that the aftershock data were concentrated into two masses: the landward side of the paleo-accretionary prism and the seaward side of the subducting plate, leaving a "white zone" in the frontal accretionary prisms. Both data sets consistently indicate the same result. The angle between the paleo-accretionary prism and the subduction plate seems to be greater than that of the frontal-accretionary prism. We suggest that the greater of the splay fault angle the higher

  3. Focal Depth of the WenChuan Earthquake Aftershocks from modeling of Seismic Depth Phases

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Zeng, X.; Chong, J.; Ni, S.; Chen, Y.

    2008-12-01

    After the 05/12/2008 great WenChuan earthquake in Sichuan Province of China, tens of thousands earthquakes occurred with hundreds of them stronger than M4. Those aftershocks provide valuable information about seismotectonics and rupture processes for the mainshock, particularly accurate spatial distribution of aftershocks is very informational for determining rupture fault planes. However focal depth can not be well resolved just with first arrivals recorded by relatively sparse network in Sichuan Province, therefore 3D seismicity distribution is difficult to obtain though horizontal location can be located with accuracy of 5km. Instead local/regional depth phases such as sPmP, sPn, sPL and teleseismic pP,sP are very sensitive to depth, and be readily modeled to determine depth with accuracy of 2km. With reference 1D velocity structure resolved from receiver functions and seismic refraction studies, local/regional depth phases such as sPmP, sPn and sPL are identified by comparing observed waveform with synthetic seismograms by generalized ray theory and reflectivity methods. For teleseismic depth phases well observed for M5.5 and stronger events, we developed an algorithm in inverting both depth and focal mechanism from P and SH waveforms. Also we employed the Cut and Paste (CAP) method developed by Zhao and Helmberger in modeling mechanism and depth with local waveforms, which constrains depth by fitting Pnl waveforms and the relative weight between surface wave and Pnl. After modeling all the depth phases for hundreds of events , we find that most of the M4 earthquakes occur between 2-18km depth, with aftershocks depth ranging 4-12km in the southern half of Longmenshan fault while aftershocks in the northern half featuring large depth range up to 18km. Therefore seismogenic zone in the northern segment is deeper as compared to the southern segment. All the aftershocks occur in upper crust, given that the Moho is deeper than 40km, or even 60km west of the

  4. Scalar-meson nonet dominance predictions for eta' decays and the quark content of the 0/sup + +/ states

    SciTech Connect

    Intemann, G.W.; Greenhut, G.K.

    1980-10-01

    Assuming that the amplitude for eta'..-->..eta..pi pi.. is dominated by scalar resonances and that the 0/sup + +/ nonet is composed of conventional p-wave qq-bar states with singlet-octet mixing, we obtain predictions for the decay width and Dalitz slope parameter for the decays eta'..-->..eta..pi pi.. and eta'..--> pi pi pi.. which are in excellent agreement with the latest experimental data. The ..pi pi.. and eta..pi.. mass spectra for eta'..-->..eta..pi pi.. are also determined and fit the experimental data quite well. Similar calculations for these decays using a qq-barqq-bar description of the 0/sup + +/ mesons yield results which disagree with experiment.

  5. Scalar mesons in the decays {eta}' {sup {yields}}3{pi}{sup 0} and {eta}' {sup {yields} {pi}0{pi}+{pi}-}

    SciTech Connect

    Likhoded, A. K. Luchinsky, A. V. Samoylenko, V. D.

    2010-10-15

    The decays {eta} {sup {yields}}3{pi}{sup 0} and {eta} {sup {yields} {pi}0{pi}+{pi}-} are considered within the isobar model. It is shown that, in order to explain the branching ratio and the shape of the Dalitz plot for the decay {eta}' {sup {yields}}3{pi}{sup 0}, it is sufficient to take into account the contributions of the {sigma} and a{sub 0} mesons. The inclusion of the {sigma} meson is necessary for reproducing the shape of the distribution over the Dalitz plot. The branching ratio for the decay {eta}' {sup {yields} {pi}0{pi}+{pi}-} is obtained. The predictions for the distributions over the Dalitz plot for this decay are presented. These predictions depend strongly on model parameters.

  6. Scientific overview and historical context of the 1811-1812 new Madrid earthquake sequence

    USGS Publications Warehouse

    Hough, S.E.

    2004-01-01

    aftershock». These values are consistent with other lines of evidence, including scaling relationships. Finally, I show that accounts from the New Madrid sequence reveal evidence for remotely triggered earthquakes well outside the NMSZ. Remotely triggered earthquakes represent a potentially important new wrinkle in historic earthquake research, as their ground motions can sometimes be confused with mainshock ground motions.

  7. Constraints on Dynamic Triggering from very Short term Microearthquake Aftershocks at Parkfield

    NASA Astrophysics Data System (ADS)

    Ampuero, J.; Rubin, A.

    2004-12-01

    The study of microearthquakes helps bridge the gap between laboratory experiments and data from large earthquakes, the two disparate scales that have contributed so far to our understanding of earthquake physics. Although they are frequent, microearthquakes are difficult to analyse. Applying high precision relocation techniques, Rubin and Gillard (2000) observed a pronounced asymmetry in the spatial distribution of the earliest and nearest aftershocks of microearthquakes along the San Andreas fault (they occur more often to the NW of the mainshock). It was suggested that this could be related to the velocity contrast across the fault. Preferred directivity of dynamic rupture pulses running along a bimaterial interface (to the SE in the case of the SAF) is expected on theoretical grounds. Our numerical simulations of crack-like rupture on such interfaces show a pronounced asymmetry of the stress histories beyond the rupture ends, and suggest two possible mechanisms for the observed asymmetry: First, that it results from an asymmmetry in the static stress field following arrest of the mainshock (closer to failure to the NW), or second, that it is due to a short-duration tensile pulse that propagates to the SE, which could reduce the number of aftershocks to the SE by dynamic triggering of any nucleation site close enough to failure to have otherwise produced an aftershock. To distinguish betwen these mechanisms we need observations of dynamic triggering in microseismicity. For small events triggered at a distance of some mainshock radii, triggering time scales are so short that seismograms of both events overlap. To detect the occurrence of compound events and very short term aftershocks in the HRSN Parkfield archived waveforms we have developed an automated search algorithm based on empirical Green's function (EGF) deconvolution. Optimal EGFs are first selected by the coherency of the cross-component convolution with respect to the target event. Then Landweber

  8. 76 FR 58540 - Proposed Information Collection Request of the ETA 581, Contribution Operations Report; Extension...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-21

    ... Information Collection Request of the ETA 581, Contribution Operations Report; Extension Without Change AGENCY... the impact of collection requirements on respondents can be properly assessed. A copy of the proposed... Contribution Operations report (Form ETA 581) is a comprehensive report of each state's UI tax operations...

  9. USING MM5V3 WITH ETA ANALYSES FOR AIR-QUALITY MODELING AT THE EPA

    EPA Science Inventory

    Efforts have been underway since MM5v3 was released in July 1999 to set up air-quality simulations using Eta analyses as background fields. Our previous simulations used a one-way quadruple-nested set of domains with horizontal grid spacing of 108, 36, 12 and 4 km. With Eta a...

  10. 78 FR 30336 - Comment Request for Information Collection: ETA-5130 Benefit Appeals Report; Extension Without...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-22

    ... Employment and Training Administration Comment Request for Information Collection: ETA-5130 Benefit Appeals... INFORMATION: I. Background The ETA-5130, Benefit Appeals Report, contains information on the number of unemployment insurance appeals and the resultant decisions classified by program, appeals level, cases...

  11. Observation of eta'c production in gammagamma fusion at CLEO.

    PubMed

    Asner, D M; Dytman, S A; Mehrabyan, S; Mueller, J A; Nam, S; Savinov, V; Huang, G S; Miller, D H; Pavlunin, V; Sanghi, B; Shibata, E I; Shipsey, I P J; Adams, G S; Chasse, M; Cummings, J P; Danko, I; Napolitano, J; Cronin-Hennessy, D; Park, C S; Park, W; Thayer, J B; Thorndike, E H; Coan, T E; Gao, Y S; Liu, F; Stroynowski, R; Artuso, M; Boulahouache, C; Blusk, S; Butt, J; Dambasuren, E; Dorjkhaidav, O; Haynes, J; Menaa, N; Mountain, R; Muramatsu, H; Nandakumar, R; Redjimi, R; Sia, R; Skwarnicki, T; Stone, S; Wang, J C; Zhang, Kevin; Mahmood, A H; Csorna, S E; Bonvicini, G; Cinabro, D; Dubrovin, M; Bornheim, A; Lipeles, E; Pappas, S P; Shapiro, A; Weinstein, A J; Mahapatra, R; Nelson, H N; Briere, R A; Chen, G P; Ferguson, T; Tatishvili, G; Vogel, H; Watkins, M E; Adam, N E; Alexander, J P; Berkelman, K; Boisvert, V; Cassel, D G; Duboscq, J E; Ecklund, K M; Ehrlich, R; Galik, R S; Gibbons, L; Gittelman, B; Gray, S W; Hartill, D L; Heltsley, B K; Hsu, L; Jones, C D; Kandaswamy, J; Kreinick, D L; Kuznetsov, V E; Magerkurth, A; Mahlke-Krüger, H; Meyer, T O; Patterson, J R; Pedlar, T K; Peterson, D; Pivarski, J; Riley, D; Sadoff, A J; Schwarthoff, H; Shepherd, M R; Sun, W M; Thayer, J G; Urner, D; Wilksen, T; Weinberger, M; Athar, S B; Avery, P; Breva-Newell, L; Potlia, V; Stoeck, H; Yelton, J; Eisenstein, B I; Gollin, G D; Karliner, I; Lowrey, N; Naik, P; Sedlack, C; Selen, M; Thaler, J J; Williams, J; Edwards, K W; Besson, D; Gao, K Y; Gong, D T; Kubota, Y; Li, S Z; Poling, R; Scott, A W; Smith, A; Stepaniak, C J; Urheim, J; Metreveli, Z; Seth, K K; Tomaradze, A; Zweber, P; Arms, K; Eckhart, E; Gan, K K; Gwon, C; Severini, H; Skubic, P

    2004-04-01

    We report on the observation of the eta(')(c)(2(1)S0), the radial excitation of the eta(c)(1(1)S0) ground state of charmonium, in the two-photon fusion reaction gammagamma-->eta(')(c)-->K(0)(S)K+/-pi(-/+) in 13.6 fb(-1) of CLEO II/II.V data and 13.1 fb(-1) of CLEO III data. We obtain M(eta(')(c))=3642.9+/-3.1(stat)+/-1.5(syst) MeV and M(eta(c))=2981.8+/-1.3(stat)+/-1.5(syst) MeV. The corresponding values of hyperfine splittings between 1S0 and 3S1 states are DeltaM(hf)(1S)=115.1+/-2.0 MeV and DeltaM(hf)(2S)=43.1+/-3.4 MeV. Assuming that the eta(c) and eta(')(c) have equal branching fractions to K(S)Kpi, we obtain Gamma(gammagamma)(eta(')(c))=1.3+/-0.6 keV. PMID:15089529

  12. 77 FR 2089 - Proposed Information Collection Request of the ETA 204, Experience Rating Report; Comment Request...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-13

    ... Information Collection Request of the ETA 204, Experience Rating Report; Comment Request on Extension Without... different experience rating systems. Used in conjunction with other data, the ETA-204 assists in determining... employment, etc.) on the unemployment experience of various groups of employers. The data also provide...

  13. Cautionary Note on Reporting Eta-Squared Values from Multifactor ANOVA Designs

    ERIC Educational Resources Information Center

    Pierce, Charles A.; Block, Richard A.; Aguinis, Herman

    2004-01-01

    The authors provide a cautionary note on reporting accurate eta-squared values from multifactor analysis of variance (ANOVA) designs. They reinforce the distinction between classical and partial eta-squared as measures of strength of association. They provide examples from articles published in premier psychology journals in which the authors…

  14. 76 FR 27090 - Comment Request for Extension of Information Collection (Without Revisions): Form ETA 9033-A...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-10

    ... Revisions): Form ETA 9033-A, Attestation by Employers Using Alien Crewmembers for Longshore Activities in... collection by Form ETA 9033-A, OMB Control Number 1205-0352, Attestation by Employers Using Alien Crewmembers.... The INA generally prohibits the performance of longshore work by alien crewmembers, however the...

  15. 77 FR 35060 - Employment and Training Administration; Proposed Information Collection Request for the ETA 538...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-12

    ... addresses section below on or before August 13, 2012. ADDRESSES: Submit written comments to Scott Gibbons... toll-free Federal Information Relay Service at 1-877-889-5627 (TTY/TDD). Email: gibbons.scott@dol.gov.... Gibbons. SUPPLEMENTARY INFORMATION: I. Background The ETA 538 and ETA 539 reports are weekly reports...

  16. The Ejecta of Eta Carinae: Just what is the Mass?

    NASA Astrophysics Data System (ADS)

    Gull, T. R.

    2006-08-01

    Estimates of the Homunculus and the Little Homunculus suggest that at least 12 solar masses were ejected in the two events of the 1840s and the 1890s (Smith et al 2003 AJ 125, 1458). We have begun a systematic analysis of the metal lines seen in the warm Homunculus and hot Little Homunculus in an attempt to characterize the properties of the gas. Analysis of these structures and the Strontium Filament suggest that Ti/Ni (and likewise Ti/Fe) is overabundant. Likely this is due to oxygen and carbon underabundances which prevent metal oxides forming. As a result, much Ti, V, Sr, Sc, Ni and Fe is left in gaseous phase. The dust associated with Eta Carinae is known to have peculiar properties. Given that many metals normally depleted in the ISM are overabundant in the ejecta of Eta Carinae, we are led to suspect that the gas/dust ratio is underestimated. Observational examples of these hundreds of lines will be shown along with model estimates of temperature, density and abundances.

  17. SECULAR CHANGES IN ETA CARINAE'S WIND 1998-2011

    SciTech Connect

    Mehner, Andrea; Davidson, Kris; Humphreys, Roberta M.; Ishibashi, Kazunori; Martin, John C.; Ruiz, Maria Teresa; Walter, Frederick M.

    2012-05-20

    Stellar wind-emission features in the spectrum of eta Carinae have decreased by factors of 1.5-3 relative to the continuum within the last 10 years. We investigate a large data set from several instruments (STIS, GMOS, UVES) obtained between 1998 and 2011 and analyze the progression of spectral changes in direct view of the star, in the reflected polar-on spectra at FOS4, and at the Weigelt knots. We find that the spectral changes occurred gradually on a timescale of about 10 years and that they are dependent on the viewing angle. The line strengths declined most in our direct view of the star. About a decade ago, broad stellar wind-emission features were much stronger in our line-of-sight view of the star than at FOS4. After the 2009 event, the wind-emission line strengths are now very similar at both locations. High-excitation He I and N II absorption lines in direct view of the star strengthened gradually. The terminal velocity of Balmer P Cyg absorption lines now appears to be less latitude dependent, and the absorption strength may have weakened at FOS4. Latitude-dependent alterations in the mass-loss rate and the ionization structure of eta Carinae's wind are likely explanations for the observed spectral changes.

  18. Recurrent X-ray Emission Variations of Eta Carinae and the Binary Hypothesis

    NASA Technical Reports Server (NTRS)

    Ishibashi, K.; Corcoran, M. F.; Davidson, K.; Swank, J. H.; Petre, R.; Drake, S. A.; Damineki, A.; White, S.

    1998-01-01

    Recent studies suggest that, the super-massive star eta Carinae may have a massive stellar companion (Damineli, Conti, and Lopes 1997), although the dense ejecta surrounding the star make this claim hard to test using conventional methods. Settling this question is critical for determining the current evolutionary state and future evolution of the star. We address this problem by an unconventional method: If eta Carinae is a binary, X-ray emission should be produced in shock waves generated by wind-wind collisions in the region between eta Carinae and its companion. Detailed X-ray monitoring of eta Carinae for more that) 2 years shows that the observed emission generally resembles colliding-wind X-ray emission, but with some significant discrepancies. Furthermore, periodic X-ray "flaring" may provide an additional clue to determine the presence of a companion star and for atmospheric pulsation in eta Carinae.

  19. Evidence for {psi}' Decays into {gamma}{pi}{sup 0} and {gamma}{eta}

    SciTech Connect

    Ablikim, M.; An, Z. H.; Bai, J. Z.; Berger, N.; Bian, J. M.; Cai, X.; Cao, G. F.; Cao, X. X.; Chang, J. F.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, Y.; Chen, Y. B.; Chu, Y. P.; Dai, H. L.; Dai, J. P.; Deng, Z. Y.; Dong, L. Y.

    2010-12-31

    The decays {psi}{sup '}{yields}{gamma}{pi}{sup 0}, {gamma}{eta} and {gamma}{eta}{sup '} are studied using data collected with the BESIII detector at the BEPCII e{sup +}e{sup -} collider. The processes {psi}{sup '}{yields}{gamma}{pi}{sup 0} and {psi}{sup '}{yields}{gamma}{eta} are observed for the first time with signal significances of 4.6{sigma} and 4.3{sigma}, respectively. The branching fractions are determined to be B({psi}{sup '}{yields}{gamma}{pi}{sup 0})=(1.58{+-}0.40{+-}0.13)x10{sup -6}, B({psi}{sup '}{yields}{gamma}{eta})=(1.38{+-}0.48{+-}0.09)x10{sup -6}, and B({psi}{sup '}{yields}{gamma}{eta}{sup '})=(126{+-}3{+-}8)x10{sup -6}, where the first errors are statistical and the second ones systematic.

  20. Investigation of near-threshold eta-meson production in the reaction {pi}{sup -}p{yields} {eta}n

    SciTech Connect

    Bayadilov, D. E.; Beloglazov, Yu. A.; Gridnev, A. B.; Kozlenko, N. G.; Kruglov, S. P.; Kulbardis, A. A.; Lopatin, I. V.; Novinskiy, D. V.; Radkov, A. K.; Sumachev, V. V.; Filimonov, E. A.; Shvedchikov, A. V.

    2012-08-15

    Differential and total cross sections for eta-meson production in the reaction {pi}{sup -}p {yields} {eta}n were measured within the experimental program eta-meson physics implemented in the pion channel of the synchrocyclotron of the Petersburg Nuclear Physics Institute (PNPI, Gatchina). These measurements were performed at incident-pion momenta (700, 710, 720, and 730 MeV/c) in the vicinity of the threshold for the process under study by using the neutral-meson spectrometer designed and created at the Meson Physics Laboratory of PNPI. It is shown that, in the immediate vicinity of the threshold (685 MeV/c), the process of eta-meson production proceeds predominantly via S{sub 11}(1535)-resonance formation followed by the decay S{sub 11}(1535) {yields} {eta}n (the respective branching fraction is Br Almost-Equal-To 60%), but that, as the momentum of incident pions increases, the role of the D wave becomes ever more important. A detailed analysis of this effect indicates that it is due to the increasing contribution of the D{sub 13}(1520) resonance. Although the branching fraction of the decay of this resonance through the {eta}n channel is assumed to be very small (BR Almost-Equal-To 0.24%), the effect is enhanced owing to the interference between the D wave and the dominant resonance S{sub 11}(1535).

  1. Seismic and Aseismic Slip on the San-Jacinto Fault Near Anza, CA, from Joint Analysis of Strain and Aftershock Data

    NASA Astrophysics Data System (ADS)

    Inbal, A.; Avouac, J. P.; Ampuero, J. P.

    2014-12-01

    The San-Jacinto Fault (SJF) is the most active fault in southern California, which together with the southern San-Andreas Fault accommodates a large fraction of the motion across the plate boundary. Seismicity along the SJF is distributed over several fault segments with distinct spatio-temporal characteristics. One of these segments, known as the Anza seismic gap, is a 25 km long strand almost devoid of seismicity. In recent years, four M4-5 events occurred SE of the gap. Despite their moderate magnitudes, these earthquakes triggered rich aftershock sequences and pronounced afterslip that lasted for several weeks, and was well captured by nearby PBO borehole strain meters. A similar transient was remotely triggered by the 2010 El Mayor-Cucapah earthquake. Geodetic and seismic observations following a local M5.4 mainshock indicate that afterslip propagated unilaterally towards the NW at speed of about 5 km/day. We infer the distribution of slip via a joint inversion of the aftershock and strain data. Our approach is based on Dieterich's (1994) model relating the evolution of seismicity rate to applied stresses, within the framework of rate-and-state friction. This approach provides resolution power at depths inaccessible to the surface geodetic network. Moreover, it allows us to gain important insights onto the fault mechanical properties. We apply this inversion scheme to episodes that occurred during 2010. Remarkably, we find that the cumulative moment released post-seismically during the locally triggered transient is 5-10 times larger than the moment of the mainshock. We show that the data favour a model in which deep slip transients, which may develop due to local or remote earthquakes, occur on a weak, close-to-velocity-neutral fault. The transients increase the stress along the Anza gap, and trigger earthquakes outside it through static stress transfer.

  2. Constraints on Decreases in Eta Carinae's Mass-loss from 3D Hydrodynamic Simulations of Its Binary Colliding Winds

    NASA Technical Reports Server (NTRS)

    Madura, T. I.; Gull, T. R.; Okazaki, A. T.; Russell, C. M. P.; Owocki, S. P.; Groh, J. H.; Corcoran, M. F.; Hamaguchi, K.; Teodoro, M.

    2013-01-01

    Recent work suggests that the mass-loss rate of the primary star Eta-A in the massive colliding wind binary Eta Carinae dropped by a factor of 2-3 between 1999 and 2010. We present result from large- (+/- 1545 au) and small- (+/- 155 au) domain, 3D smoothed particle hydrodynamics (SPH) simulations of Eta Car's colliding winds for three Eta-A mass-loss rates ( (dot-M(sub Eta-A) = 2.4, 4.8 and 8.5 × 10(exp -4) M(solar)/ yr), investigating the effects on the dynamics of the binary wind-wind collision (WWC). These simulations include orbital motion, optically thin radiative cooling and radiative forces. We find that dot-M Eta-A greatly affects the time-dependent hydrodynamics at all spatial scales investigated. The simulations also show that the post-shock wind of the companion star Eta-B switches from the adiabatic to the radiative-cooling regime during periastron passage (Phi approx.= 0.985-1.02). This switchover starts later and ends earlier the lower the value of dot-M Eta-A and is caused by the encroachment of the wind of Eta-A into the acceleration zone of Eta-B's wind, plus radiative inhibition of Eta-B's wind by Eta-A. The SPH simulations together with 1D radiative transfer models of Eta-A's spectra reveal that a factor of 2 or more drop in dot-M EtaA should lead to substantial changes in numerous multiwavelength observables. Recent observations are not fully consistent with the model predictions, indicating that any drop in dot- M Eta-A was likely by a factor of approx. < 2 and occurred after 2004. We speculate that most of the recent observed changes in Eta Car are due to a small increase in the WWC opening angle that produces significant effects because our line of sight to the system lies close to the dense walls of the WWC zone. A modest decrease in dot-M Eta-A may be responsible, but changes in the wind/stellar parameter of Eta-B, while less likely, cannot yet be fully ruled out. We suggest observations during Eta-Car's next periastron in 2014 to further

  3. DISTANCE AND THE INITIAL MASS FUNCTION OF YOUNG OPEN CLUSTERS IN THE {eta} CARINA NEBULA: Tr 14 AND Tr 16

    SciTech Connect

    Hur, Hyeonoh; Sung, Hwankyung; Bessell, Michael S. E-mail: sungh@sejong.ac.kr

    2012-02-15

    We present new UBVI{sub c} CCD photometry of the young open clusters Trumpler 14 (Tr 14) and Trumpler 16 (Tr 16) in the {eta} Carina Nebula. We also identify the optical counterpart of Chandra X-ray sources and Two Micron All Sky Survey point sources. The members of the clusters were selected from the proper-motion study, spectral types, reddening characteristics, and X-ray or near-IR excess emission. An abnormal reddening law R{sub V,cl} = 4.4 {+-} 0.2 was obtained for the stars in the {eta} Carina Nebula using the 141 early-type stars with high proper-motion membership probability (P{sub {mu}} gE 70%). We determined the distance to each cluster and conclude that Tr 14 and Tr 16 have practically the same distance modulus of V{sub 0} - M{sub V} = 12.3 {+-} 0.2 mag (d = 2.9 {+-} 0.3 kpc). The slope of the initial mass function was determined to be {Gamma} = -1.3 {+-} 0.1 for Tr 14, {Gamma} = -1.3 {+-} 0.1 for Tr 16, and {Gamma} = -1.4 {+-} 0.1 for all members in the observed region for the stars with log mgE0.2. We also estimated the age of the clusters to be about 1-3 Myr from the evolutionary stage of evolved stars and low-mass pre-main-sequence stars.

  4. Full waveform modelling using the VERCE platform - application to aftershock seismicity in the Chile subduction zone

    NASA Astrophysics Data System (ADS)

    Garth, Thomas; Rietbrock, Andreas; Hicks, Steve; Fuenzalida Velasco, Amaya; Casarotti, Emanuele; Spinuso, Alessandro

    2015-04-01

    The VERCE platform is an online portal that allows full waveform simulations to be run for any region where a suitable velocity model exists. We use this facility to simulate the waveforms from aftershock earthquakes from the 2014 Pisagua earthquake, and 2010 Maule earthquake that occurred at the subduction zone mega thrust in Northern and Central Chile respectively. Simulations are performed using focal mechanisms from both global earthquake catalogues, and regional earthquake catalogues. The VERCE platform supports specFEM Cartesian, and simulations are run using meshes produced by CUBIT. The full waveform modelling techniques supported on the VERCE platform are used to test the validity of a number of subduction zone velocity models from the Chilean subduction zone. For the Maule earthquake we use a 2D and 3D travel time tomography model of the rupture area (Hicks et al. 2011; 2014). For the Pisagua earthquake we test a 2D/3D composite velocity model based on tomographic studies of the region (e.g. Husen et al. 2000, Contreyes-Reyes et al. 2012) and slab1.0 (Hayes et al. 2012). Focal mechanisms from the cGMT catalogue and local focal mechanisms calculated using ISOLA (e.g. Agurto et al. 2012) are used in the simulations. The waveforms produced are directly compared to waveforms recorded on the temporary deployment for the Maule earthquake aftershocks, and waveforms recorded on the IPOC network for the Pisagua earthquake aftershocks. This work demonstrates how the VERCE platform allows waveforms from the full 3D simulations to be easily produced, allowing us to quantify the validity of both the velocity model and the source mechanisms. These simulations therefore provide an independent test of the velocity models produced synthetically and by travel time tomography studies. Initial results show that the waveform is reasonably well reproduced in the 0.05 - 0.25 frequency band using a refined 3D travel time tomography, and locally calculated focal mechanisms.

  5. Estimating seismic site response in Christchurch City (New Zealand) from dense low-cost aftershock arrays

    USGS Publications Warehouse

    Kaiser, Anna E.; Benites, Rafael A.; Chung, Angela I.; Haines, A. John; Cochran, Elizabeth S.; Fry, Bill

    2011-01-01

    The Mw 7.1 September 2010 Darfield earthquake, New Zealand, produced widespread damage and liquefaction ~40 km from the epicentre in Christchurch city. It was followed by the even more destructive Mw 6.2 February 2011 Christchurch aftershock directly beneath the city’s southern suburbs. Seismic data recorded during the two large events suggest that site effects contributed to the variations in ground motion observed throughout Christchurch city. We use densely-spaced aftershock recordings of the Darfield earthquake to investigate variations in local seismic site response within the Christchurch urban area. Following the Darfield main shock we deployed a temporary array of ~180 low-cost 14-bit MEMS accelerometers linked to the global Quake-Catcher Network (QCN). These instruments provided dense station coverage (spacing ~2 km) to complement existing New Zealand national network strong motion stations (GeoNet) within Christchurch city. Well-constrained standard spectral ratios were derived for GeoNet stations using a reference station on Miocene basalt rock in the south of the city. For noisier QCN stations, the method was adapted to find a maximum likelihood estimate of spectral ratio amplitude taking into account the variance of noise at the respective stations. Spectral ratios for QCN stations are similar to nearby GeoNet stations when the maximum likelihood method is used. Our study suggests dense low-cost accelerometer aftershock arrays can provide useful information on local-scale ground motion properties for use in microzonation. Preliminary results indicate higher amplifications north of the city centre and strong high-frequency amplification in the small, shallower basin of Heathcote Valley.

  6. Precise aftershock distribution of the 2011 off the Pacific coast of Tohoku Earthquake revealed by an ocean-bottom seismometer network

    NASA Astrophysics Data System (ADS)

    Shinohara, Masanao; Machida, Yuya; Yamada, Tomoaki; Nakahigashi, Kazuo; Shinbo, Takashi; Mochizuki, Kimihiro; Murai, Yoshio; Hino, Ryota; Ito, Yoshihiro; Sato, Toshinori; Shiobara, Hajime; Uehira, Kenji; Yakiwara, Hiroshi; Obana, Koichiro; Takahashi, Narumi; Kodaira, Shuichi; Hirata, Kenji; Tsushima, Hiroaki; Iwasaki, Takaya

    2012-12-01

    The 2011 off the Pacific coast of Tohoku Earthquake occurred at the plate boundary between the Pacific plate and the landward plate on March 11, 2011, and had a magnitude of 9. Many aftershocks occurred following the mainshock. Obtaining a precise aftershock distribution is important for understanding the mechanism of earthquake generation. In order to study the aftershock activity of this event, we carried out extensive sea-floor aftershock observations using more than 100 ocean-bottom seismometers just after the mainshock. A precise aftershock distribution for approximately three months over the whole source area was obtained from the observations. The aftershocks form a plane dipping landward over the whole area, nevertheless the epicenter distribution is not uniform. Comparing seismic velocity structures, there is no aftershock along the plate boundary where a large slip during the mainshock is estimated. Activity of aftershocks in the landward plate in the source region was high and normal fault-type, and strike-slip-type, mechanisms are dominant. Within the subducting oceanic plate, most earthquakes have also a normal fault-type, or strike-slip-type, mechanism. The stress fields in and around the source region change as a result of the mainshock.

  7. Distribution and migration of aftershocks of the 2010 Mw 7.4 Ogasawara Islands intraplate normal-faulting earthquake related to a fracture zone in the Pacific plate

    NASA Astrophysics Data System (ADS)

    Obana, Koichiro; Takahashi, Tsutomu; No, Tetsuo; Kaiho, Yuka; Kodaira, Shuichi; Yamashita, Mikiya; Sato, Takeshi; Nakamura, Takeshi

    2014-04-01

    describe the aftershocks of a Mw 7.4 intraplate normal-faulting earthquake that occurred 150 km east Ogasawara (Bonin) Islands, Japan, on 21 December 2010. It occurred beneath the outer trench slope of the Izu-Ogasawara trench, where the Pacific plate subducts beneath the Philippine Sea plate. Aftershock observations using ocean bottom seismographs (OBSs) began soon after the earthquake and multichannel seismic reflection surveys were conducted across the aftershock area. Aftershocks were distributed in a NW-SE belt 140 km long, oblique to the N-S trench axis. They formed three subparallel lineations along a fracture zone in the Pacific plate. The OBS observations combined with data from stations on Chichi-jima and Haha-jima Islands revealed a migration of the aftershock activity. The first hour, which likely outlines the main shock rupture, was limited to an 80 km long area in the central part of the subsequent aftershock area. The first hour activity occurred mainly around, and appears to have been influenced by, nearby large seamounts and oceanic plateau, such as the Ogasawara Plateau and the Uyeda Ridge. Over the following days, the aftershocks expanded beyond or into these seamounts and plateau. The aftershock distribution and migration suggest that crustal heterogeneities related to a fracture zone and large seamounts and oceanic plateau in the incoming Pacific plate affected the rupture of the main shock. Such preexisting structures may influence intraplate normal-faulting earthquakes in other regions of plate flexure prior to subduction.

  8. A Measurement of the B ---> Eta/C K Branching Fraction Using the BaBar Detector

    SciTech Connect

    Jackson, Frank; /Manchester U.

    2006-04-26

    The branching fraction is measured for the decay channels B{sup 0} {yields} {eta}{sub c}K{sub S}{sup 0} and B{sup +} {yields} {eta}{sub c}K{sup +} where {eta}{sub c} {yields} K{bar K}{pi}, using the BABAR detector. The {eta}{sub c} {yields} K{sub S}{sup 0}K{sup +}{pi}{sup -} and {eta}{sub c} {yields} K{sup +}K{sup -}{pi}{sup 0} decay channels are used, including non-resonant decays and possibly those through intermediate resonances.

  9. Source and Aftershock Analysis of a Large Deep Earthquake in the Tonga Flat Slab

    NASA Astrophysics Data System (ADS)

    Cai, C.; Wiens, D. A.; Warren, L. M.

    2013-12-01

    The 9 November 2009 (Mw 7.3) deep focus earthquake (depth = 591 km) occurred in the Tonga flat slab region, which is characterized by limited seismicity but has been imaged as a flat slab in tomographic imaging studies. In addition, this earthquake occurred immediately beneath the largest of the Fiji Islands and was well recorded by a temporary array of 16 broadband seismographs installed in Fiji and Tonga, providing an excellent opportunity to study the source mechanism of a deep earthquake in a partially aseismic flat slab region. We determine the positions of main shock hypocenter, its aftershocks and moment release subevents relative to the background seismicity using a hypocentroidal decomposition relative relocation method. We also investigate the rupture directivity by measuring the variation of rupture durations at different azimuth [e.g., Warren and Silver, 2006]. Arrival times picked from the local seismic stations together with teleseismic arrival times from the International Seismological Centre (ISC) are used for the relocation. Teleseismic waveforms are used for directivity study. Preliminary results show this entire region is relatively aseismic, with diffuse background seismicity distributed between 550-670 km. The main shock happened in a previously aseismic region, with only 1 small earthquake within 50 km during 1980-2012. 11 aftershocks large enough for good locations all occurred within the first 24 hours following the earthquake. The aftershock zone extends about 80 km from NW to SE, covering a much larger area than the mainshock rupture. The aftershock distribution does not correspond to the main shock fault plane, unlike the 1994 March 9 (Mw 7.6) Fiji-Tonga earthquake in the steeply dipping, highly seismic part of the Tonga slab. Mainshock subevent locations suggest a sub-horizontal SE-NW rupture direction. However, the directivity study shows a complicated rupture process which could not be solved with simple rupture assumption. We will

  10. Using the USGS Seismic Risk Web Application to estimate aftershock damage

    USGS Publications Warehouse

    McGowan, Sean M.; Luco, Nicolas

    2014-01-01

    The U.S. Geological Survey (USGS) Engineering Risk Assessment Project has developed the Seismic Risk Web Application to combine earthquake hazard and structural fragility information in order to calculate the risk of earthquake damage to structures. Enabling users to incorporate their own hazard and fragility information into the calculations will make it possible to quantify (in near real-time) the risk of additional damage to structures caused by aftershocks following significant earthquakes. Results can quickly be shared with stakeholders to illustrate the impact of elevated ground motion hazard and earthquake-compromised structural integrity on the risk of damage during a short-term, post-earthquake time horizon.

  11. Geotechnical effects of the 2015 magnitude 7.8 Gorkha, Nepal, earthquake and aftershocks

    USGS Publications Warehouse

    Moss, Robb E S; Thompson, Eric; Kieffer, D Scott; Tiwari, Binod; Hashash, Youssef M A; Acharya, Indra; Adhikari, Basanta; Asimaki, Domniki; Clahan, Kevin B.; Collins, Brian D.; Dahal, Sachindra; Jibson, Randall W.; Khadka, Diwakar; Macdonald, Amy; Madugo, Chris L M; Mason, H Benjamin; Pehlivan, Menzer; Rayamajhi, Deepak; Uprety, Sital

    2015-01-01

    This article summarizes the geotechnical effects of the 25 April 2015 M 7.8 Gorkha, Nepal, earthquake and aftershocks, as documented by a reconnaissance team that undertook a broad engineering and scientific assessment of the damage and collected perishable data for future analysis. Brief descriptions are provided of ground shaking, surface fault rupture, landsliding, soil failure, and infrastructure performance. The goal of this reconnaissance effort, led by Geotechnical Extreme Events Reconnaissance, is to learn from earthquakes and mitigate hazards in future earthquakes.

  12. Measurement of the branching fraction for $\\tau\\to\\eta K\

    SciTech Connect

    del Amo Sanchez, P.; Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Palano, A.; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Battaglia, M.; Brown, D.N.; Hooberman, B.; Kerth, L.T.; Kolomensky, Yu.G.; Lynch, G.; Osipenkov, I.L.; Tanabe, T.; /UC, Berkeley /Birmingham U. /Ruhr U., Bochum /British Columbia U. /Brunel U. /Novosibirsk, IYF /UC, Irvine /UC, Riverside /UC, Santa Barbara /UC, Santa Cruz /Caltech /Cincinnati U. /Colorado U. /Colorado State U. /Dortmund U. /Dresden, Tech. U. /Ecole Polytechnique /Edinburgh U. /INFN, Ferrara /Ferrara U. /INFN, Ferrara /INFN, Ferrara /Ferrara U. /INFN, Ferrara /Frascati /INFN, Genoa /Genoa U. /INFN, Genoa /INFN, Genoa /Genoa U. /INFN, Genoa /INFN, Genoa /Genoa U. /Indian Inst. Tech., Guwahati /Harvard U. /Heidelberg U. /Humboldt U., Berlin /Imperial Coll., London /Iowa State U. /Iowa State U. /Johns Hopkins U. /Paris U., VI-VII /LLNL, Livermore /Liverpool U. /Queen Mary, U. of London /Royal Holloway, U. of London /Royal Holloway, U. of London /Louisville U. /Mainz U., Inst. Kernphys. /Manchester U. /Maryland U. /Massachusetts U., Amherst /MIT /McGill U. /INFN, Milan /Milan U. /INFN, Milan /INFN, Milan /Milan U. /Mississippi U. /Montreal U. /INFN, Naples /Naples U. /NIKHEF, Amsterdam /NIKHEF, Amsterdam /Notre Dame U. /Ohio State U. /Oregon U. /INFN, Padua /Padua U. /INFN, Padua /INFN, Padua /Padua U. /Paris U., VI-VII /INFN, Perugia /Perugia U. /INFN, Pisa /Pisa U. /INFN, Pisa /Pisa, Scuola Normale Superiore /INFN, Pisa /Pisa U. /INFN, Pisa /Princeton U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /INFN, Rome /INFN, Rome /Rome U. /Rostock U. /Rutherford /DAPNIA, Saclay /SLAC /South Carolina U. /Southern Methodist U. /Stanford U., Phys. Dept. /SUNY, Albany /Tel Aviv U. /Tennessee U. /Texas U. /Texas U., Dallas /INFN, Turin /Turin U. /INFN, Trieste /Trieste U. /Valencia U. /Victoria U. /Warwick U. /Wisconsin U., Madison

    2011-08-12

    The authors report on analyses of tau lepton decays {tau}{sup -} {yields} {eta}K{sup -}{nu}{sub {tau}} and {tau}{sup -} {yields} {eta}{pi}{sup -}{nu}{sub {tau}}, with {eta} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}, using 470 fb{sup -1} of data from the BABAR experiment at PEP-II, collected at center-of-mass energies at and near the {Upsilon}(4S) resonance. They measure the branching fraction for the {tau}{sup -} {yields} {eta}K{sup -}{nu}{sub {tau}} decay mode, {Beta}({tau}{sup -} {yields} {eta}K{sup -}{nu}{sub {tau}}) = (1.42 {+-} 0.11(stat) {+-} 0.07(syst)) x 10{sup -4}, and report a 95% confidence level upper limit for the second-class current process {tau}{sup -} {yields} {eta}{pi}{sup -}{nu}{sub {tau}}, {Beta}({tau}{sup -} {yields} {eta}{pi}{sup -}{nu}{sub {tau}}) < 9.9 x 10{sup -5}.

  13. Model Error Estimation for the CPTEC Eta Model

    NASA Technical Reports Server (NTRS)

    Tippett, Michael K.; daSilva, Arlindo

    1999-01-01

    Statistical data assimilation systems require the specification of forecast and observation error statistics. Forecast error is due to model imperfections and differences between the initial condition and the actual state of the atmosphere. Practical four-dimensional variational (4D-Var) methods try to fit the forecast state to the observations and assume that the model error is negligible. Here with a number of simplifying assumption, a framework is developed for isolating the model error given the forecast error at two lead-times. Two definitions are proposed for the Talagrand ratio tau, the fraction of the forecast error due to model error rather than initial condition error. Data from the CPTEC Eta Model running operationally over South America are used to calculate forecast error statistics and lower bounds for tau.

  14. UNEXPECTED IONIZATION STRUCTURE IN ETA CARINAE'S ''WEIGELT KNOTS''

    SciTech Connect

    Remmen, Grant N.; Davidson, Kris; Mehner, Andrea

    2013-08-10

    The Weigelt knots, dense slow-moving ejecta near {eta} Carinae, are mysterious in structure as well as in origin. Using spatially dithered spectrograms obtained with the Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS), we have partially resolved the ionization zones of one knot. Contrary to simple models, higher ionization levels occur on the outer side, i.e., farther from the star. They cannot represent a bow shock, and no satisfying explanation is yet available-though we sketch one qualitative possibility. STIS spectrograms provide far more reliable spatial measurements of the Weigelt knots than HST images do, and this technique can also be applied to the knots' proper motion problem. Our spatial measurement accuracy is about 10 mas, corresponding to a projected linear scale of the order of 30 AU, which is appreciably smaller than the size of each Weigelt knot.

  15. The -145 km/S Absorption System of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Vieira, G.; Gull, T. R.; Danks, A.; Johansson, S.

    2002-01-01

    With the STIS E230H mode (R-118,000) , we have identified about twenty absorption components in line of sight from Eta Carinae. Two components, one at -513 km/s and another at -145 W s , are quite different in character from the others, mostly at intermediate velocities. The -145 km/s component is significantly wider in fwhm, is seen in many more species, and the lower level can be above 20,000/cm, well above the 2000/cm noted in the -513 km/s component. In the spectral region from 2400 to 3160A, approximately 500 absorption lines have been identified. In this poster, we will present line identifications and atomic parameters of the measured lines, hopefully providing insight as to what levels are being excited and by what processes.

  16. The -145 km/s Absorption System of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Vieira, G.; Gull, Theodore R.; Danks, A.; Johansson, S.

    2002-01-01

    With the STIS E230H mode (R approx. 118,000), we have identified about twenty absorption components in line of sight from Eta Carinae. Two components, one at -513 km/s and another at -145 km/s, are quite different in character from the others, mostly at intermediate velocities. The -145 km/s component is significantly wider in fwhm, is seen in many more species, and the lower level can be above 20,000/cm, well above the 2000/cm noted in the -513 km/s component. In the spectral region from 2400 to 3160A, approximately 500 absorption lines have been identified. In this poster, we will present line identifications and atomic parameters of the measured lines, hopefully providing insight as to what levels are being excited and by what processes. Observations were accomplished through STScI under proposal 9242. Funding is through the STIS GTO resources.

  17. Recovery from a Giant Eruption: The Case of Eta Car

    NASA Astrophysics Data System (ADS)

    Davidson, Kris; Mehner, Andrea; Martin, John C.; Humphreys, Roberta M.

    2016-01-01

    Giant eruptions or SN Impostors are far more mysterious than "real" supernovae, because they are scarcer and because they have received far less theoretical effort. One rather special problem is the disequilibrium state of the post-eruption object. It may be partially observable by watching the star's gradual recovery; which, in principle, may offer clues to the basic instability mechanisms. So far, the only example that can be observed well enough is eta Carinae. This object's history offers tantalizing clues and counter-clues. For instance: (1) Before 2000, the recovery timescale seemed to be of order 150 years; but (2) around 2000, many attributes began to change much more rapidly; and (3) the 150-year recovery process has been punctuated by about three abrupt changes of state. This strange combination of facts has received almost no theoretical attention.

  18. Understanding the X-ray Flaring from Eta Carinae

    NASA Technical Reports Server (NTRS)

    Moffat, A.F.J.; Corcoran, Michael F.

    2009-01-01

    We quantify the rapid variations in X-ray brightness ("flares") from the extremely massive colliding wind binary Eta Carinae seen during the past three orbital cycles by RXTE. The observed flares tend to be shorter in duration and more frequent as periastron is approached, although the largest ones tend to be roughly constant in strength at all phases. Plausible scenarios include (1) the largest of multi-scale stochastic wind clumps from the LBV component entering and compressing the hard X-ray emitting wind-wind collision (WWC) zone, (2) large-scale corotating interacting regions in the LBV wind sweeping across the WWC zone, or (3) instabilities intrinsic to the WWC zone. The first one appears to be most consistent with the observations, requiring homologously expanding clumps as they propagate outward in the LBV wind and a turbulence-like powerlaw distribution of clumps, decreasing in number towards larger sizes, as seen in Wolf-Rayet winds.

  19. Little Homunculus with in the Homunculus of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Ishibashi, Kazunori; Gull, Theodore R.; Davidson, Kris; Fisher, Richard R. (Technical Monitor)

    2000-01-01

    The famous HST/WFPC2 images of Eta Carinae provide a two-dimensional projection of the bipolar nebula that is really a three-dimensional structure. Much is hidden in subtle, projected details that a velocity-tuned instrument can pull apart. We have used the HST/STIS with a 52" x 0.1" aperture and with about 5000 spectral resolving power to examine the kinetic information contained within emission/absorption features. By velocity tuning, we can translate this information into spatial structures. The spectroscopic datasets have been transformed to a set of images, spaced at half instrumental line width steps, 15 - 20 km/s , and with a spatial resolution of 0.1 x 0.1 arcsec near Balmer beta and 0.25 x 0.1 arcsec near Balmer alpha. We examined these narrow-band images and individual spectra to characterize the nature of an internal nebula (formerly known as the Integral nebula). The shape of this nebulosity is an bipolar nebula, deeply embedded within the Homunculus, the well-known bipolar nebula surrounding Eta Carinae. The internal nebula is shaped nearly identically to the Homunculus. It is best described as a "little Homunculus within the Homunculus". Indeed, it is reminiscent of the Russian dolls, known as Matryoshka dolls, that successively nest within each larger doll. For that reason, we call this internal nebula the Matryoshka nebula. This was performed as one of the STIS GTO key projects and was funded by the HST project. Observations were done through the STScI.

  20. The Time Evolution of Eta Carinae's Colliding Winds

    NASA Technical Reports Server (NTRS)

    Gull, Theodore R.; Madura, T. I.; Grobe, J. H.; Corcoran, M. F.

    2011-01-01

    We report new HST/STIS observations that map the high-ionization forbidden line emission in the inner arc second of Eta Car, the first that fully image the extended wind-wind interaction region of the massive colliding wind binary. These observations were obtained after the 2009.0 periastron at orbital phases 0.084, 0.163, and 0.323 of the 5.54-year spectroscopic cycle. We analyze the variations in brightness and morphology of the emission, and find that blue-shifted emission (-400 to -200 km/s is symmetric and elongated along the northeast-southwest axis, while the red-shifted emission (+ 100 to +200 km/s) is asymmetric and extends to the north-northwest. Comparison to synthetic images generated from a 3-D dynamical model strengthens the 3-D orbital orientation found by Madura et al. (2011), with an inclination i = 138 deg, argument of periapsis w = 270 deg, and an orbital axis that is aligned at the same P A on the sky as the symmetry axis of the Homunculus, 312 deg. We discuss the potential that these and future mappings have for constraining the stellar parameters of the companion star and the long-term variability of the system. Plain-Language Abstract: With HST, we resolved the interacting winds of the binary, Eta Carinae. With a 3-D model, we find the binary orbit axis is aligned to the Homunculus axis. This suggests a connection between the binary and Homunculus ejection mechanism.

  1. Stress evolution following the 1999 Chi-Chi, Taiwan, earthquake: Consequences for afterslip, relaxation, aftershocks and departures from Omori decay

    USGS Publications Warehouse

    Chan, C.-H.; Stein, R.S.

    2009-01-01

    We explore how Coulomb stress transfer and viscoelastic relaxation control afterslip and aftershocks in a continental thrust fault system. The 1999 September 21 Mw = 7.6 Chi-Chi shock is typical of continental ramp-d??collement systems throughout the world, and so inferences drawn from this uniquely well-recorded event may be widely applicable. First, we find that the spatial and depth distribution of aftershocks and their focal mechanisms are consistent with the calculated Coulomb stress changes imparted by the coseismic rupture. Some 61 per cent of the M ??? 2 aftershocks and 83 per cent of the M ??? 4 aftershocks lie in regions for which the Coulomb stress increased by ???0.1 bars, and there is a 11-12 per cent gain in the percentage of aftershocks nodal planes on which the shear stress increased over the pre-Chi Chi control period. Second, we find that afterslip occurred where the calculated coseismic stress increased on the fault ramp and d??collement, subject to the condition that friction is high on the ramp and low on the d??collement. Third, viscoelastic relaxation is evident from the fit of the post-seismic GPS data on the footwall. Fourth, we find that the rate of seismicity began to increase during the post-seismic period in an annulus extending east of the main rupture. The spatial extent of the seismicity annulus resembles the calculated ???0.05-bar Coulomb stress increase caused by viscoelastic relaxation and afterslip, and we find a 9-12 per cent gain in the percentage of focal mechanisms with >0.01-bar shear stress increases imparted by the post-seismic afterslip and relaxation in comparison to the control period. Thus, we argue that post-seismic stress changes can for the first time be shown to alter the production of aftershocks, as judged by their rate, spatial distribution, and focal mechanisms. ?? Journal compilation ?? 2009 RAS.

  2. Stress loading from viscous flow in the lower crust and triggering of aftershocks following the 1994 Northridge, California, earthquake

    USGS Publications Warehouse

    Deng, J.; Hudnut, K.; Gurnis, M.; Hauksson, E.

    1999-01-01

    Following the M(w) 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.Following the Mw 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.

  3. Including foreshocks and aftershocks in time-independent probabilistic seismic hazard analyses

    USGS Publications Warehouse

    Boyd, Oliver S.

    2012-01-01

    Time‐independent probabilistic seismic‐hazard analysis treats each source as being temporally and spatially independent; hence foreshocks and aftershocks, which are both spatially and temporally dependent on the mainshock, are removed from earthquake catalogs. Yet, intuitively, these earthquakes should be considered part of the seismic hazard, capable of producing damaging ground motions. In this study, I consider the mainshock and its dependents as a time‐independent cluster, each cluster being temporally and spatially independent from any other. The cluster has a recurrence time of the mainshock; and, by considering the earthquakes in the cluster as a union of events, dependent events have an opportunity to contribute to seismic ground motions and hazard. Based on the methods of the U.S. Geological Survey for a high‐hazard site, the inclusion of dependent events causes ground motions that are exceeded at probability levels of engineering interest to increase by about 10% but could be as high as 20% if variations in aftershock productivity can be accounted for reliably.

  4. Dynamical instability as the cause of the massive outbursts in Eta Carinae and other luminous blue variables

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.; Chin, Chao-Wen

    1993-01-01

    A new type of stellar envelope structure has been computationally discovered at very high stellar masses. The outer part of the envelope resembles a nearly detached, diffusely filled shell overlying an ultrahot surface of small radius. This structural anomaly is caused by a large iron bump occurring in the new opacities of Iglesias et al. (1992). The new stellar models with normal metallicity encounter a strong ionization-induced dynamical instability in the outer envelope as they rapidly transit the H-R diagram after the end of central hydrogen burning. Preliminary evolutionary and hydrodynamical calculations successfully mimic the most basic observed properties of Eta Carinae and other very luminous blue variables. The Humphreys-Davidson sloped line in the H-R diagram, however, seems to be unrelated to these variables, and is instead the observed terminus of the main-sequence phase of evolution if convective core overshooting is insignificant.

  5. ETA receptor blockade potentiates the bronchoconstrictor response to ET-1 in the guinea pig airway.

    PubMed

    Polakowski, J S; Opgenorth, T J; Pollock, D M

    1996-08-01

    The effect of ETA receptor blockade on the bronchopulmonary response to endothelin-1 was determined in the airway of the anesthetized, spontaneously breathing guinea pig. Endothelin-1 administered as an aerosol increased lung resistance and decreased dynamic lung compliance. Delivery of the ETA receptor antagonist, FR139317, 5 min prior to giving endothelin-1 greatly potentiated these changes. A lower dose of endothelin-1 that had no effect on resistance or compliance produced large and significant changes when pretreated with FR139317. In contrast, aerosolized FR139317 had no effect on the bronchopulmonary response to intravenously administered endothelin-1. These data suggest a non-contractile function of ETA receptors accessible from the airways that serve to buffer the constrictor effects of non-ETA receptors.

  6. A PERFORMANCE EVALUATION OF THE ETA- CMAQ AIR QUALITY FORECAST SYSTEM FOR THE SUMMER OF 2005

    EPA Science Inventory

    This poster presents an evaluation of the Eta-CMAQ Air Quality Forecast System's experimental domain using O3 observations obtained from EPA's AIRNOW program and a suite of statistical metrics examining both discrete and categorical forecasts.

  7. PKC{eta} is a negative regulator of AKT inhibiting the IGF-I induced proliferation

    SciTech Connect

    Shahaf, Galit; Rotem-Dai, Noa; Koifman, Gabriela; Raveh-Amit, Hadas; Frost, Sigal A.; Livneh, Etta

    2012-04-15

    The PI3K-AKT pathway is frequently activated in human cancers, including breast