Science.gov

Sample records for earthquakes occur frequently

  1. Loss of BAP1 Expression Occurs Frequently in Intrahepatic Cholangiocarcinoma.

    PubMed

    Andrici, Juliana; Goeppert, Benjamin; Sioson, Loretta; Clarkson, Adele; Renner, Marcus; Stenzinger, Albrecht; Tayao, Michael; Watson, Nicole; Farzin, Mahtab; Toon, Christopher W; Smith, Ross C; Mittal, Anubhav; Samra, Jaswinder S; Hugh, Thomas J; Chou, Angela; Lawlor, Rita T; Weichert, Wilko; Schirmacher, Peter; Sperandio, Nicola; Ruzzenente, Andrea; Scarpa, Aldo; Gill, Anthony J

    2016-01-01

    BRCA1-associated protein 1 (BAP1) is a deubiquitinating enzyme that functions as a tumor suppressor gene. Double hit BAP1 inactivation has been reported in a range of tumor types, including intrahepatic cholangiocarcinoma (ICC), sometimes in association with germline mutation.We performed immunohistochemistry for BAP1 on a well-characterized cohort of 211 ICC patients undergoing surgical resection with curative intent at 3 institutions based in 3 different countries. The median age at diagnosis was 65 years (range, 36.5-86) and 108 (51%) were men. Negative staining for BAP1 (defined as completely absent nuclear staining in the presence of positive internal controls in nonneoplastic cells) occurred in 55 ICCs (26%). BAP1 loss predicted a strong trend toward improved median survival of 40.80 months (95% CI, 28.14-53.46) versus 24.87 months (95% CI, 18.73-31.01), P?=?0.059). In a multivariate model including age, sex, BAP1 status, tumor stage, tumor grade, lymphovascular invasion, and tumor size, female sex was associated with improved survival (hazard ratio [HR] 0.54; 95% CI, 0.34-0.85), while advanced tumor stage and lymphovascular invasion (HR 1.89; 95% CI, 1.09-3.28) correlated with decreased survival. In a multivariate analysis, high grade tumors were associated with BAP1 loss (odds ratio [OR] 3.32; 95% CI, 1.29-8.55), while lymphatic invasion was inversely associated with BAP1 loss (OR 0.36; 95% CI, 0.13-0.99).In conclusion, we observed a trend toward improved prognosis in ICC associated with absent expression of BAP1 and an association of BAP1 loss with higher histological grade and absent lymphatic invasion. Female sex was associated with improved survival while advanced tumor stage and lymphatic invasion were associated with decreased survival. PMID:26765459

  2. Loss of BAP1 Expression Occurs Frequently in Intrahepatic Cholangiocarcinoma

    PubMed Central

    Andrici, Juliana; Goeppert, Benjamin; Sioson, Loretta; Clarkson, Adele; Renner, Marcus; Stenzinger, Albrecht; Tayao, Michael; Watson, Nicole; Farzin, Mahtab; Toon, Christopher W.; Smith, Ross C.; Mittal, Anubhav; Samra, Jaswinder S.; Hugh, Thomas J.; Chou, Angela; Lawlor, Rita T.; Weichert, Wilko; Schirmacher, Peter; Sperandio, Nicola; Ruzzenente, Andrea; Scarpa, Aldo; Gill, Anthony J.

    2016-01-01

    Abstract BRCA1-associated protein 1 (BAP1) is a deubiquitinating enzyme that functions as a tumor suppressor gene. Double hit BAP1 inactivation has been reported in a range of tumor types, including intrahepatic cholangiocarcinoma (ICC), sometimes in association with germline mutation. We performed immunohistochemistry for BAP1 on a well-characterized cohort of 211 ICC patients undergoing surgical resection with curative intent at 3 institutions based in 3 different countries. The median age at diagnosis was 65 years (range, 36.5–86) and 108 (51%) were men. Negative staining for BAP1 (defined as completely absent nuclear staining in the presence of positive internal controls in nonneoplastic cells) occurred in 55 ICCs (26%). BAP1 loss predicted a strong trend toward improved median survival of 40.80 months (95% CI, 28.14–53.46) versus 24.87 months (95% CI, 18.73–31.01), P = 0.059). In a multivariate model including age, sex, BAP1 status, tumor stage, tumor grade, lymphovascular invasion, and tumor size, female sex was associated with improved survival (hazard ratio [HR] 0.54; 95% CI, 0.34–0.85), while advanced tumor stage and lymphovascular invasion (HR 1.89; 95% CI, 1.09–3.28) correlated with decreased survival. In a multivariate analysis, high grade tumors were associated with BAP1 loss (odds ratio [OR] 3.32; 95% CI, 1.29–8.55), while lymphatic invasion was inversely associated with BAP1 loss (OR 0.36; 95% CI, 0.13–0.99). In conclusion, we observed a trend toward improved prognosis in ICC associated with absent expression of BAP1 and an association of BAP1 loss with higher histological grade and absent lymphatic invasion. Female sex was associated with improved survival while advanced tumor stage and lymphatic invasion were associated with decreased survival. PMID:26765459

  3. Why and Where do Large Shallow Slab Earthquakes Occur?

    NASA Astrophysics Data System (ADS)

    Seno, T.; Yoshida, M.

    2001-12-01

    Within a shallow portion (20-60 km depth) of subducting slabs, it has been believed that large earthquakes seldom occur because the differential stress is generally expected to be low between bending at the trench-outer rise and unbending at the intermediate-depth. However, there are several regions in which large ( M>=7.0 ) earthquakes, including three events early in this year, have occurred in this portion. Searching such events from published individual studies and Harvard University centroid moment tensor catalogue, we find nineteen events in eastern Hokkaido, Kyushu-SW Japan, Mariana, Manila, Sumatra, Vanuatu, Chile, Peru, El Salvador, Mexico, and Cascadia. Slab stresses revealed from the mechanism solutions of those large events and smaller events are tensional in a slab dip direction. However, ages of the subducting oceanic plates are generally young, which denies a possibility that the slab pull works as a cause. Except for Manila and Sumatra, the stresses in the overriding plates are characterized by the change in {? }Hmax direction from arc-parallel in the back-arc to arc-perpendicular in the fore-arc, which implies that a horizontal stress gradient exists in the across-arc direction. Peru and Chile, where the back-arc is compressional, can be categorized into this type, because a horizontal stress gradient exists over the continent from tension in east to compression in the west. In these regions, it is expected that mantle drag forces are operating beneath the upper plates, which drive the upper plates to the trenchward overriding the subducting oceanic plates. Assuming that the mantle drag forces beneath the upper plates originate from the mantle convection currents or upwelling plumes, we infer that the upper plates driven by the convection suck the oceanic plates, making the shallow portion of the slabs in extra-tension, thus resulting in the large shallow slab earthquakes in this tectonic regime.

  4. Major earthquakes occur regularly on an isolated plate boundary fault.

    PubMed

    Berryman, Kelvin R; Cochran, Ursula A; Clark, Kate J; Biasi, Glenn P; Langridge, Robert M; Villamor, Pilar

    2012-06-29

    The scarcity of long geological records of major earthquakes, on different types of faults, makes testing hypotheses of regular versus random or clustered earthquake recurrence behavior difficult. We provide a fault-proximal major earthquake record spanning 8000 years on the strike-slip Alpine Fault in New Zealand. Cyclic stratigraphy at Hokuri Creek suggests that the fault ruptured to the surface 24 times, and event ages yield a 0.33 coefficient of variation in recurrence interval. We associate this near-regular earthquake recurrence with a geometrically simple strike-slip fault, with high slip rate, accommodating a high proportion of plate boundary motion that works in isolation from other faults. We propose that it is valid to apply time-dependent earthquake recurrence models for seismic hazard estimation to similar faults worldwide. PMID:22745426

  5. An Analysis of the Most Frequently Occurring Words in Spoken American English.

    ERIC Educational Resources Information Center

    Plant, Geoff

    1999-01-01

    A study analyzed frequency of occurrence of consonants, vowels, and diphthongs, syllabic structure of the words, and segmental structure of the 311 monosyllabic words of 500 words that occur most frequently in English. Three mannerisms of articulation accounted for nearly 75 percent of all consonant occurrences: stops, semi-vowels, and nasals.

  6. Could a Sumatra-like megathrust earthquake occur in the south Ryukyu subduction zone?

    NASA Astrophysics Data System (ADS)

    Lin, Jing-Yi; Sibuet, Jean-Claude; Hsu, Shu-Kun; Wu, Wen-Nan

    2014-12-01

    A comparison of the geological and geophysical environments between the Himalaya-Sumatra and Taiwan-Ryukyu collision-subduction systems revealed close tectonic similarities. Both regions are characterized by strongly oblique convergent processes and dominated by similar tectonic stress regimes. In the two areas, the intersections of the oceanic fracture zones with the subduction systems are characterized by trench-parallel high free-air gravity anomaly features in the fore-arcs and the epicenters of large earthquakes were located at the boundary between the positive and negative gravity anomalies. These event distributions and high-gravity anomalies indicate a strong coupling degree of the intersection area, which was probably induced by a strong resistance of the fracture features during the subduction. Moreover, the seismicity distribution in the Ryukyu area was very similar to the pre-seismic activity pattern of the 2004 Sumatra event. That is, thrust-type earthquakes with a trench-normal P-axis occurred frequently along the oceanward side of the mainshock, whereas only a few thrust earthquakes occurred along the continentward side. Therefore, the aseismic area located west of 128E in the western Ryukyu subduction zone could have resulted from the strong plate locking effect beneath the high gravity anomaly zone. By analogy with the tectonic environment of the Sumatra subduction zone, the occurrence of a potential Sumatra-like earthquake in the south Ryukyu arc is highly likely and the rupture will mainly propagate continentward to fulfill the region of low seismicity (approximately 125 E to 129 E; 23 N to 26.5 N), which may generate a hazardous tsunami.

  7. Earthquakes

    MedlinePLUS

    An earthquake happens when two blocks of the earth suddenly slip past one another. Earthquakes strike suddenly, violently, and without warning at any time of the day or night. If an earthquake occurs in a populated area, it may cause ...

  8. Frequent excitations of T waves by earthquakes in the South Mariana Arc

    NASA Astrophysics Data System (ADS)

    Chen, Po-Fei; Chen, Kai-Xun; Cheng, Hui-Yun

    2015-02-01

    We used broadband stations in Taiwan and on the Ryukyu Arc islands to investigate T waves induced by earthquakes in the Izu-Bonin-Mariana subduction zone. Of the 48 earthquakes that took place in 2005, 17 earthquakes exhibited T-wave signals consistent with predicted arrival times at stations. Of theses T-excited events, 13 were located in the South Mariana Arc, where the isobaths exhibit strong concave curvature, and were predominantly of normal faulting type. The energies of observed T waves were used quantitatively to evaluate the relative efficiency of receiver-side acoustic-elastic conversions by Gamma calculations. Results show that the steep slopes of offshore bathymetry together with nearly perpendicular angles of back azimuth relative to local isobaths are suitable conditions for T waves observations. In 2010, two clusters of repeated moderate earthquakes in the north and south ends of the Mariana Arc displayed stark contrasts in terms of T-wave excitations despite their normal faulting type. Examining of this discrepancy indicate that a specific curvature together with a specific radiation pattern accounts for the frequent excitations of T waves from shallow earthquakes in the South Mariana Arc.

  9. Classification of magnitude 7 earthquakes which occurred after 1885 in Tokyo Metropolitan area

    NASA Astrophysics Data System (ADS)

    Ishibe, T.; Satake, K.; Shimazaki, K.; Nishiyama, A.

    2010-12-01

    Tokyo Metropolitan area is situated in tectonically complex region; both the Pacific (PAC) and Philippine Sea (PHS) plates are subducting from east and south, respectively, beneath the Kanto region. As a result, various types of earthquakes occur in this region; i.e., shallow crustal earthquakes, intraplate (slab) earthquakes within PHS, within PAC, and interplate earthquakes between continental plate and PHS, and between PHS and PAC. Among these, the largest earthquakes are Kanto earthquakes (M~8) occurring between the continental plate and PHS. The average recurrence interval is estimated to be 200 - 400 years (Earthq. Res. Comm., 2004), and hence, urgency of the next Kanto earthquake is thought to be low considering the lapse time (~87 yrs.) from the most recent Kanto earthquake in 1923. However, urgency of the other types of earthquakes with M~7 is high; Earthq. Res. Comm. (2004) calculated the probability of occurrence during the next 30 years as 70 %, based on the facts that five M~7 earthquakes (i.e., the 1894 Meiji-Tokyo, 1895 and 1921 Ibaraki-Ken-Nanbu, 1922 Uraga channel and 1987 Chiba-Ken Toho-Oki earthquakes) occurred since 1885. However, types of earthquakes are not well known especially for the 1894 Meiji-Tokyo and 1895 Ibaragi-Ken-Nanbu earthquakes due to low quality of data. Thus, it is important to classify these earthquakes into above-described intraplate or interplate earthquakes and to estimate their occurrence frequency. Ishibe et al. (2009a, 2009b) compiled previous studies and data for these five earthquakes. In this study, we report the preliminary result of focal depth and mechanism for the 1895 and 1921 Ibaraki-Ken-Nanbu earthquakes. The epicenter of the 1895 Ibaraki-Ken-Nanbu earthquake (M 7.2; Utsu, 1979) is discussed by various studies (e.g., Usami, 1973; Ishibashi, 1975; Katsumata, 1975; Utsu, 1979). However, few studies have discussed the hypocentral depth. The hypocentral depth is estimated to be 75 ~ 85 km using S-P time at Tokyo (11.3sec) reported from Omori (1899) and Japan Meteorological Agency (JMA) velocity structure (Ueno et al., 2002) assuming epicenter by Utsu (1979). It suggests that this earthquake occurred within the subducting PAC from the comparison of plate boundary estimated by Ishida (1992). More reliable classification would be possible using seismic intensity distribution though it is differently estimated among several studies. The 1921 Ibaraki-Ken-Nanbu earthquake (M 7.0; Utsu, 1979) caused damage such as fissures of road, tumble of gravestones especially in the northwestern Chiba and southwestern Ibaraki. The hypocentral depth is estimated to be around 55 km using S-P time from Ishibashi (1975) and JMA velocity structure, suggesting that this earthquake was not a slab earthquake within PAC. Seismic intensity map supports this result, i.e., anomalous seismic intensity distribution characterizing the slab earthquakes within PAC is not recognized. Estimated focal mechanism using HASH (Hardebeck and Shearer, 2002) is a strike-slip type, even if taking uncertainty of hypocentral location into consideration. This result is consistent with previous studies (e.g., Ishibashi, 1975; Katsumata, 2000; Umino et al. 2010). Thus, this earthquake probably occurred within the subducting PHS.

  10. Mortality-based Quantification of Injury Severity for Frequently Occurring Motor Vehicle Crash Injuries.

    PubMed

    Weaver, Ashley A; Barnard, Ryan T; Kilgo, Patrick D; Martin, R Shayn; Stitzel, Joel D

    2013-01-01

    The study purpose was to develop mortality-based metrics of injury severity for frequent motor vehicle crash (MVC) injuries. Injury severity was quantified with mortality-based metrics for 240 injuries comprising the top 95% most frequently occurring AIS 2+ injuries in the National Automotive Sampling System - Crashworthiness Data System (NASS-CDS) 2000-2011. Mortality risk ratios (MRRs) were computed by dividing the number of deaths by occurrences for each of the 240 injuries using National Trauma Data Bank Research Data System (NTDB-RDS) MVC cases. MRRMAIS was computed using only patients with a maximum AIS (MAIS) equal to the AIS severity of a given injury. Each injury had an associated MRR and MRRMAIS which ranged from zero (0% mortality representing low severity) to one (100% or universal mortality representing high severity). Injuries with higher MRR and MRRMAIS values are considered more severe because they resulted in a greater proportion of deaths among injured patients. The results illustrated an overall positive trend between AIS severity and the MRR and MRRMAIS values as expected, but showed large variations in MRR and MRRMAIS for some injuries of the same AIS severity. Mortality differences up to 83% (MRR) and 54% (MRRMAIS) were observed for injuries of the same AIS severity. The MRR-based measures of injury severity indicate that some lower AIS severity injuries may result in as many deaths as higher AIS severity injuries. This data-driven determination of injury severity using MRR and MRRMAIS provides a supplement or an alternative to AIS severity classification. PMID:24406961

  11. Mortality-based Quantification of Injury Severity for Frequently Occurring Motor Vehicle Crash Injuries

    PubMed Central

    Weaver, Ashley A.; Barnard, Ryan T.; Kilgo, Patrick D.; Martin, R. Shayn; Stitzel, Joel D.

    2013-01-01

    The study purpose was to develop mortality-based metrics of injury severity for frequent motor vehicle crash (MVC) injuries. Injury severity was quantified with mortality-based metrics for 240 injuries comprising the top 95% most frequently occurring AIS 2+ injuries in the National Automotive Sampling System Crashworthiness Data System (NASS-CDS) 20002011. Mortality risk ratios (MRRs) were computed by dividing the number of deaths by occurrences for each of the 240 injuries using National Trauma Data Bank Research Data System (NTDB-RDS) MVC cases. MRRMAIS was computed using only patients with a maximum AIS (MAIS) equal to the AIS severity of a given injury. Each injury had an associated MRR and MRRMAIS which ranged from zero (0% mortality representing low severity) to one (100% or universal mortality representing high severity). Injuries with higher MRR and MRRMAIS values are considered more severe because they resulted in a greater proportion of deaths among injured patients. The results illustrated an overall positive trend between AIS severity and the MRR and MRRMAIS values as expected, but showed large variations in MRR and MRRMAIS for some injuries of the same AIS severity. Mortality differences up to 83% (MRR) and 54% (MRRMAIS) were observed for injuries of the same AIS severity. The MRR-based measures of injury severity indicate that some lower AIS severity injuries may result in as many deaths as higher AIS severity injuries. This data-driven determination of injury severity using MRR and MRRMAIS provides a supplement or an alternative to AIS severity classification. PMID:24406961

  12. Assessment of infants with peripherally inserted central catheters: Part 1. Detecting the most frequently occurring complications.

    PubMed

    Pettit, Janet

    2002-12-01

    Inserting, maintaining, and monitoring vascular access are integral components of neonatal care. Advances in vascular access technology have led to the insertion of peripherally inserted central catheters (PICC) to provide stable venous access for early and aggressive parenteral nutrition. Medications that are irritating or damaging, or those with a high osmolality or a nonphysiologic pH, can also be safely administered into the central venous system. The need for repeated peripheral intravenous attempts, as well as the associated pain and physiologic instability, are virtually eliminated once a PICC line is placed. Complications related to PICCs may occur at any phase of therapy: during insertion, while indwelling, or after discontinuing the line. The risk factors associated with PICCs are distinctly different from peripheral intravenous lines because of their long dwell time, central placement, and potential to migrate. Part 1 of Focus on the Physical offers a review of the relevant anatomy of the vascular system and a discussion of the appropriate sites for catheter tip placement. Guidelines for a systematic physical assessment, along with recommendations for standardized PICC documentation, are provided. A review of the signs and symptoms of more frequently occurring complications, such as catheter occlusion and bloodstream infections, is presented to enhance awareness of PICC-specific complications in the neonate and to expedite early detection and treatment. Part 2 of this series will focus on systematic assessment for less common complications such as catheter migration, dislodgement, breakage, and thrombosis, as well as the life-threatening complications of pleural and pericardial effusion. PMID:12881943

  13. Do the great Himalayan earthquakes occur on the plane of detachment?

    NASA Astrophysics Data System (ADS)

    Kayal, J.; Mooney, W. D.

    2007-05-01

    The most accepted conceptual tectonic models of the Himalayan Seismic Belt (HSB) suggest that below the Main Central Thrust (MCT) lies the Basement Thrust Front (BTF), a 'ramp', the geometrical asperity that accumulates the tectonic stress due to collision tectonics, and the great earthquakes occur on the basement thrust/or on the plane of detachment that separates the Indian shield and the Himalayan sedimentary wedge. Some authors named it Main Himalayan Thrust (MHT). These models are based on the teleseismic data and geological/geophysical evidences. The microearthquake data and a relook into the source processes of the great earthquakes in the Himalaya do not support these models. The four known great (M~8.0) earthquakes in the Himalaya, from west to east, the 1905 Kangra, 1934 Bihar, 1897 Shillong and the 1950 Assam, occurred by different tectonic processes, and possibly none can be explained by the conceptual tectonic models of the HSB; each occurred in its own unique tectonic environment.

  14. Variations in Electron density and temperature prior to Chile Earthquake occurred on February 27, 2010 observed by DEMETER Satellite

    NASA Astrophysics Data System (ADS)

    Raghuwanshi, Shailesh Kumar; Gwal, Ashok Kumar

    Abstract: The statistical analysis of the variations of the electron density and electron temperature is performed in connection with the occurrence of Chile region earthquake (35.900S/72.730W) with magnitude M>8 occurred on February 27, 2014. For the study, data of ISL (Langmuir probe) experiments of DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite was used. It was noticed that the s electron density increases and the value of electron temperature was decrease few days before the earthquake. Study demonstrates that satellite data can play an important role for the study of precursory phenomena associated with earthquakes.

  15. Seismogenesis of the lower crustal intraplate earthquakes occurring in Kachchh, Gujarat, India

    NASA Astrophysics Data System (ADS)

    Mandal, Prantik; Pandey, O. P.

    2011-08-01

    Large intraplate continental earthquakes like the 1811-12 New Madrid (M w ? 8.0) and the 2001 Bhuj (Mw7.7) were highly destructive because they occurred in strong crust, but the mechanisms underlying their seismogenesis are not understood. Here we show, using local earthquake velocity tomography, and joint inversion of receiver functions and surface wave group velocity dispersion that the crust and uppermost mantle beneath the 2001 Bhuj earthquake region of western India is far more complex than hitherto known through previous studies. A new image of the crust and underlying mantle lithosphere indicates the presence of a 18-km thick high velocity (Vp: 7.15-8.11 km/s) differentiated crustal and mantle magmatic layer above a hot and thin lithosphere (only 70 km) in the epicentral region of 2001 Bhuj earthquake. This magmatic layer begins at the depth of 24 km and continues down to 42 km depth. Below this region, brittle-ductile transition reaches as deep as the Moho (34 km) due to the possible presence of olivine rich mafic magma. Our 1-D velocity structure envisages an initial phase of plume activity (Deccan plume at 65 m.y. ago) resulting in basaltic magma in the eclogitic layers at sub-lithospheric levels, wherein they were subjected to crystallization under ultra-high pressure conditions. Our study also delineates an updoming of Moho (4-7 km) as well as asthenosphere (6-10 km) below the Kachchh rift zone relative to surrounding areas, suggesting the presence of a confined body of partial melts below the lithosphere-asthenosphere boundary. Restructuring of this warm and thin lithosphere may have been caused due to rifting (at 184 and 88 m.y. ago) and tholeiitic and alkalic volcanism related to the Deccan Traps K/T boundary event (at 65 m.y. ago). Recent study of isotopic ratios proposed that the alkalic basalts found in Kachchh are generated from a CO 2 rich lherzolite partial melts in the asthenosphere that ascended along deep lithospheric rift faults into the lithosphere. It appears that such kind of crust-mantle structure, deepening of brittle-ductile transition and a high input of volatiles containing CO 2 emanating from mantle control the seismogenesis of lower crustal earthquakes in the Kachchh continental rift zone.

  16. Earthquakes

    USGS Publications Warehouse

    Shedlock, Kaye M.; Pakiser, Louis Charles

    1998-01-01

    One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible aftereffects. An earthquake is a sudden movement of the Earth, caused by the abrupt release of strain that has accumulated over a long time. For hundreds of millions of years, the forces of plate tectonics have shaped the Earth as the huge plates that form the Earth's surface slowly move over, under, and past each other. Sometimes the movement is gradual. At other times, the plates are locked together, unable to release the accumulating energy. When the accumulated energy grows strong enough, the plates break free. If the earthquake occurs in a populated area, it may cause many deaths and injuries and extensive property damage. Today we are challenging the assumption that earthquakes must present an uncontrollable and unpredictable hazard to life and property. Scientists have begun to estimate the locations and likelihoods of future damaging earthquakes. Sites of greatest hazard are being identified, and definite progress is being made in designing structures that will withstand the effects of earthquakes.

  17. Why Do Slow Earthquakes Occur Favorably in Hot Subduction Zones? : 2D Numerical Analysis

    NASA Astrophysics Data System (ADS)

    Yamashita, T.; Schubnel, A.

    2014-12-01

    It is puzzling why slow earthquakes occur in hot subduction zones only. We study numerically how antigorite dehydration coupled with slip-induced dilatancy and thermal pressurization affects rupture behavior to solve the above puzzle. Recent related studies actually suggest importance of antigorite dehydration. We assume faulting in a 2D thermoporoelastic medium. The mineral reaction is assumed using a first order Arrhenius law. Nondimensional parameters important in the modeling are Su, Su' and X' according to our former study; Su' and Su are proportional to permeability and increase rate of slip-induced porosity. X' denotes volume change induced by the reaction. Our calculation shows that moment release rate and fault tip growth rate are smaller for larger values of Su, smaller values of X' or smaller values of Su'. These two rates are found to be negligibly small compared with the solutions for the dynamic elasticity analysis when Su>1 and X'<0 are satisfied. Slow sustained fault growth occurs for such values of Su and X'. This suggests that Su>1 and X'<0 are satisfied at hot subduction zones; the condition X'<0 is consistent with the reaction expected at hot subduction zones. In cold subduction zones however, antigorite dehydration will occur at depth greater than 60km, with -0.1occurs because the slip velocity evolution is more pulse-like for larger values of |X'|. In such way, antigorite dehydration could also be the source of a non-negligible fraction of intermediate depth seismicity. The condition Su<1 will be due to the fact that slip-dilatancy is more prohibited at larger depth.

  18. T cell responses in early-stage melanoma patients occur frequently and are not associated with humoral response.

    PubMed

    Pfirschke, Christina; Gebhardt, Christoffer; Zrnig, Inka; Pritsch, Maria; Eichmller, Stefan B; Jger, Dirk; Enk, Alexander; Beckhove, Philipp

    2015-11-01

    Endogenous tumor-specific T cells are detectable in patients with different tumor types including malignant melanoma (MM). They can control tumor growth, have impact on patient survival and correlate with improved clinical response to immune checkpoint therapy. Thus, they may represent a potent biomarker for respective treatment decisions. So far, major target antigens of endogenous MM-reactive T cells have not been determined systematically. Instead, autoantibodies are discussed as surrogate parameter for MM-specific T cells. Throughout a period of more than 60 days after tumor resection, we therefore determined in 38 non-metastasized primary MM patients and in healthy individuals by IFN? ELISpot and bead-based fluorescent multiplex assay major target antigens of spontaneous T cell and humoral responses using a broad panel of MM antigens and assessed the presence and suppressive impact of MM-reactive regulatory T cells (Tregs). We show that MM-reactive T cells are frequent in MM patients, transiently increase after tumor removal and are mostly directed against Melan-A/MART-1, Tyrosinase, NA17-A and p53. MM-specific Tregs were only detected in few patients and inhibited MM-reactive T cells particularly early after tumor resection. Tumor-specific autoantibodies occurred in most patients, but did not correlate with T cell responses. Thus, endogenous antibodies may not be reliable surrogate parameters of MM-reactive T cells. PMID:26160687

  19. Specific suites of earthquakes occurring at shallow and intermediate depths - a signature of major lithospheric deformation episodes in Vrancea seismic zone

    NASA Astrophysics Data System (ADS)

    Chitea, F.; Mitrofan, H.; Marin, C.; Anghelache, M. A.; Tudorache, A.

    2009-04-01

    At the southeast Carpathians bend, in Vrancea seismic zone, strong and very strong earthquakes (Mw ? 6) frequently occur at intermediate (subcrustal) depths (70-160 km), in a highly confined (30 x 60 km) epicentral area. Investigations addressing regularities in those earthquakes recurrence periods have so far been concerned just with the actual subcrustal seismogenic volume: possibly existing relationships with the shallower (h < 60 km) and less strong (Mw < 5) crustal earthquakes which were recorded in an adjacent, broader area, have not been considered. A Na-K-Mg geothermometer anomaly, which we managed to monitor for more than 1 year prior to the occurrence of a strong intermediate-depth Vrancea earthquake, provided a first suggestion that such a major shock could be somehow related also to smaller magnitude crustal events. The present search for coherence patterns has taken into account main seismic events recorded since 1975 till now in three distinct domains: (i) in the very domain of intermediate-depth seismicity (all the events with Mw ? 6.0); (ii) in a previously outlined crustal lineament of seismic sensitivity, extending between the cities Marasesti and Galati (all the events with Mw ? 3.3); (iii) in another previously outlined crustal lineament of seismic sensitivity, designated as "Vrancioaia region" (events with Mw ? 2.6). The two indicated lineaments of crustal seismicity converge, to delineate an obtuse angle which closely bounds the narrow epicentral domain of the subcrustal earthquakes. Over the indicated time-period, the considered seismic events series developed as a succession of 4 distinct "episodes", each episode displaying a highly similar evolution pattern: it started with one of the main crustal events (2.6?Mw?4.5) recorded in Vrancioaia region; there followed, 9-23 months afterwards, one or two strong (6.0?Mw?7.4), intermediate-depth earthquakes; finally, 5-42 months after the intermediate-depth earthquakes, there was recorded one of the main crustal events (3.3?Mw?4.4) of the Marasesti-Galati lineament. The above-indicated time-lags provided obvious evidence that the considered crustal earthquakes were neither foreshocks, nor aftershocks of the strong intermediate-depth events. Instead, each succession of "Vrancioaia crustal - strong subcrustal - Marasesti-Galati crustal" events appeared to define a major lithospheric deformation episode. In the case of the last recorded episode ("centered" on the strong subcrustal earthquake of 27 October 2004), corroborating evidence that some kind of long-range lithospheric deformation indeed took place has been provided by Na-K-Mg geothermometry anomalies recorded at a deep-origin groundwater discharge (Slanic Moldova): while the corresponding "forerunning" crustal earthquake of Vrancioaia region had occurred on 10 February 2003, the hydrogeochemically anomalous behavior has been continuously manifest from April 2003 until October 2004. The previously-discussed results revealed that some kind of long-range interdependence seemed to exist between various phenomena (subcrustal and crustal seismicity, groundwater chemistry fluctuations) that occurred in a broad region associated to the Vrancea "nest" of strong earthquakes. Integrated monitoring of the indicated phenomena might further provide precursor signatures of impending catastrophic Vrancea earthquakes. At the same time, there can be assessed possible influences that major lithospheric deformation episodes, related to Vrancea zone, might exert on the seismicity of apparently remote areas (that of the major city of Galati, for instance).

  20. ANALYSIS OF LABOUR ACCIDENTS OCCURRING IN DISASTER RESTORATION WORK FOLLOWING THE NIIGATA CHUETSU EARTHQUAKE (2004) AND THE NIIGATA CHUETSU-OKI EARTHQUAKE (2007)

    NASA Astrophysics Data System (ADS)

    Itoh, Kazuya; Noda, Masashi; Kikkawa, Naotaka; Hori, Tomohito; Tamate, Satoshi; Toyosawa, Yasuo; Suemasa, Naoaki

    Labour accidents in disaster-relief and disaster restoration work following the Niigata Chuetsu Earthquake (2004) and the Niigata Chuetsu-oki Earthquake (2007) were analysed and characterised in order to raise awareness of the risks and hazards in such work. The Niigata Chuetsu-oki Earthquake affected houses and buildings rather than roads and railways, which are generally disrupted due to landslides or slope failures caused by earthquakes. In this scenario, the predominant type of accident is a "fall to lower level," which increases mainly due to the fact that labourers are working to repair houses and buildings. On the other hand, landslides and slope failures were much more prevalent in the Niigata Chuetsu Earthquake, resulting in more accidents occurring in geotechnical works rather than in construction works. Therefore, care should be taken in preventing "fall to lower level" accidents associated with repair work on the roofs of low-rise houses, "cut or abrasion" accidents due to the demolition of damaged houses and "caught in or compressed by equipment" accidents in road works and water and sewage works.

  1. Commensurability of earthquake occurrence

    NASA Astrophysics Data System (ADS)

    Hu, Hui; Han, Yanben; Su, Youjin; Wang, Rui

    2013-07-01

    During recent years huge earthquakes frequently occurred and caused surprise attack on many places of the globe. Frequent exceptional strong disasters of earthquakes remind that we must strengthen our research on cause of formation, mechanism, prediction and forecast of earthquakes, and achieve the goal of advancing the development of Earth science and mitigation of seismic disasters. The commensurability of earthquake occurrences has been studied by means of the commensurability revealed by the Titius-Bode law in the paper. The studied results show that the earthquakes basically all occur at the commensurable point of its time axis, respectively. It also shows that occurrence of the earthquakes is not accidental, showing certain patterns and inevitability, and the commensurable value is different for earthquakes occurring in different areas.

  2. Long-Term RST Analysis of Anomalous TIR Sequences in Relation with Earthquakes Occurred in Greece in the Period 2004-2013

    NASA Astrophysics Data System (ADS)

    Eleftheriou, Alexander; Filizzola, Carolina; Genzano, Nicola; Lacava, Teodosio; Lisi, Mariano; Paciello, Rossana; Pergola, Nicola; Vallianatos, Filippos; Tramutoli, Valerio

    2015-07-01

    Real-time integration of multi-parametric observations is expected to accelerate the process toward improved, and operationally more effective, systems for time-Dependent Assessment of Seismic Hazard (t-DASH) and earthquake short-term (from days to weeks) forecast. However, a very preliminary step in this direction is the identification of those parameters (chemical, physical, biological, etc.) whose anomalous variations can be, to some extent, associated with the complex process of preparation for major earthquakes. In this paper one of these parameters (the Earth's emitted radiation in the Thermal InfraRed spectral region) is considered for its possible correlation with M ? 4 earthquakes occurred in Greece in between 2004 and 2013. The Robust Satellite Technique (RST) data analysis approach and Robust Estimator of TIR Anomalies (RETIRA) index were used to preliminarily define, and then to identify, significant sequences of TIR anomalies (SSTAs) in 10 years (2004-2013) of daily TIR images acquired by the Spinning Enhanced Visible and Infrared Imager on board the Meteosat Second Generation satellite. Taking into account the physical models proposed for justifying the existence of a correlation among TIR anomalies and earthquake occurrences, specific validation rules (in line with the ones used by the Collaboratory for the Study of Earthquake PredictabilityCSEPProject) have been defined to drive a retrospective correlation analysis process. The analysis shows that more than 93 % of all identified SSTAs occur in the prefixed space-time window around (M ? 4) earthquake's time and location of occurrence with a false positive rate smaller than 7 %. Molchan error diagram analysis shows that such a correlation is far to be achievable by chance notwithstanding the huge amount of missed events due to frequent space/time data gaps produced by the presence of clouds over the scene. Achieved results, and particularly the very low rate of false positives registered on a so long testing period, seems already sufficient (at least) to qualify TIR anomalies (identified by RST approach and RETIRA index) among the parameters to be considered in the framework of a multi-parametric approach to t-DASH.

  3. Long-Term RST Analysis of Anomalous TIR Sequences in Relation with Earthquakes Occurred in Greece in the Period 2004-2013

    NASA Astrophysics Data System (ADS)

    Eleftheriou, Alexander; Filizzola, Carolina; Genzano, Nicola; Lacava, Teodosio; Lisi, Mariano; Paciello, Rossana; Pergola, Nicola; Vallianatos, Filippos; Tramutoli, Valerio

    2016-01-01

    Real-time integration of multi-parametric observations is expected to accelerate the process toward improved, and operationally more effective, systems for time-Dependent Assessment of Seismic Hazard (t-DASH) and earthquake short-term (from days to weeks) forecast. However, a very preliminary step in this direction is the identification of those parameters (chemical, physical, biological, etc.) whose anomalous variations can be, to some extent, associated with the complex process of preparation for major earthquakes. In this paper one of these parameters (the Earth's emitted radiation in the Thermal InfraRed spectral region) is considered for its possible correlation with M ≥ 4 earthquakes occurred in Greece in between 2004 and 2013. The Robust Satellite Technique (RST) data analysis approach and Robust Estimator of TIR Anomalies (RETIRA) index were used to preliminarily define, and then to identify, significant sequences of TIR anomalies (SSTAs) in 10 years (2004-2013) of daily TIR images acquired by the Spinning Enhanced Visible and Infrared Imager on board the Meteosat Second Generation satellite. Taking into account the physical models proposed for justifying the existence of a correlation among TIR anomalies and earthquake occurrences, specific validation rules (in line with the ones used by the Collaboratory for the Study of Earthquake Predictability—CSEP—Project) have been defined to drive a retrospective correlation analysis process. The analysis shows that more than 93 % of all identified SSTAs occur in the prefixed space-time window around ( M ≥ 4) earthquake's time and location of occurrence with a false positive rate smaller than 7 %. Molchan error diagram analysis shows that such a correlation is far to be achievable by chance notwithstanding the huge amount of missed events due to frequent space/time data gaps produced by the presence of clouds over the scene. Achieved results, and particularly the very low rate of false positives registered on a so long testing period, seems already sufficient (at least) to qualify TIR anomalies (identified by RST approach and RETIRA index) among the parameters to be considered in the framework of a multi-parametric approach to t-DASH.

  4. Source Mechanisms of Recent Earthquakes occurred in the Fethiye-Rhodes Basin and Anaximander Seamounts (SW Turkey)

    NASA Astrophysics Data System (ADS)

    Yolsal-Çevikbilen, Seda; Taymaz, Tuncay

    2015-04-01

    Understanding the active tectonics of southern Turkey involves integrating earthquake source parameters with the regional tectonics. In this respect, seismological studies have played important roles in deciphering tectonic deformations and existing stress accumulations in the region. This study is concerned with the source mechanism parameters and spatio-temporal finite-fault slip distributions of recent earthquakes occurred along the Pliny-Strabo Trench (PST), which constitutes the eastern part of the Hellenic subduction zone in the Eastern Mediterranean Sea Region, and along the Fethiye-Burdur Fault Zone (SW Turkey). The study area is located at the junction of the Hellenic and Cyprus arcs along which the African plate plunges northwards beneath the Aegean Sea and the Anatolian block. Bathymetry and topography including large-scale tectonic structures such as the Rhodes Basin, Anaximander Seamounts, the Florence Rise, the Isparta Angle, the Taurus Mountains, and Kyrenia Range also reflect the tectonic complexities in the region. In this study, we performed point-source inversions by using teleseismic long-period P- and SH- and broad-band P-waveforms recorded by the Federation of Digital Seismograph Networks (FDSN) and the Global Digital Seismograph Network (GDSN) stations. We obtained source mechanism parameters and finite-fault slip distributions of recent Fethiye-Rhodes earthquakes (Mw ≥ 5.0) by comparing the shapes and amplitudes of long period P- and SH-waveforms, recorded in the distance range of 30 - 90 degrees, with synthetic waveforms. We further obtained rupture histories of the earthquakes to determine the fault area (fault length and width), maximum displacement, rupture duration and stress drop. Inversion results exhibit that recent earthquakes show left-lateral strike-slip faulting mechanisms with relatively deeper focal depths (h > 40 km) consistent with tectonic characteristics of the region, for example, the June 10, 2012 Fethiye earthquake (Mw: 5.9) can clearly be correlated with the left-lateral Fethiye-Burdur Fault Zone in SW Turkey.

  5. Tension crack characteristics of surface ruptures of 2 strong earthquakes recently occurred along reverse faults in China

    NASA Astrophysics Data System (ADS)

    Liu, Mingjun; Dai, Aopeng; Zhang, Feng

    2014-05-01

    Field investigations show that there are some tension cracks in the surface ruptures of 2 strong earthquakes recently occurred along reverse faults with strike-slip component in China. Yushu Ms7.1 earthquake occurred on April 14, 2010 in Qinghai, China produced a ~65 km long co-seismic surface rupture with a strike of 310, which is distributed along Ganzi-Yushu fault that is a reverse fault with strike-slip component in the QinghaiTibetan Plateau. The surface rupture of Yushu Ms7.1 earthqake consists of shear, transtensional cracks, transpressional cracks, tension cracks and mole tracks. Some tension cracks occur on the top of small uplifts and the cracking course is from surface to undergound for some tension cracks are shallow. The small uplifts are actually anticlines produced by a regional and deep compressional stress field, but there is a local tensional stress field on the top of the anticlines. Lushan Ms7.0 earthquake on 20 April 20, 2013 in Sichuan, China occurred on the southern segment of the Longmenshan fault zone with a NE strike which is also a reverse fault zone with strike-slip component, but only a co-seismic surface rupture 80m long with a NW strike was found without any NE-striking surface rupture found. The surface rupture shows the form of tension cracks on a top of a small uplift. There are two sets of fresh striation on the surface rupture plane, the striation with larger plunge angles usually only remains above the range 10-20cm below the ground surface, which is covered by the striation with smaller plunging angles. The comprehensive analysis shows that the surface rupture during the Ms7.0 Lushan earthquake at first experienced thrusting, then sinistral strike-slip, and tension cracking at last. In general, some tension cracks of the surface ruptures from Yushu Ms7.1 earthquake on April 14, 2010 and Lushan Ms7.0 earthquake on 20 April 2013 may be produced by the local tensional stress field, but they also reflect the regional and deep compressional stress environment. The work is sponsored by National Natural Science Foundation of China (Grant No. 41174078) and China Spark Program of seismological science and technology (Grant No.XH12068).

  6. Earthquakes

    MedlinePLUS

    ... Weather Workplace Plans School Emergency Plans Main Content Earthquakes Earthquakes are sudden rolling or shaking events caused ... at any time of the year. Before An Earthquake Look around places where you spend time. Identify ...

  7. Earthquakes.

    ERIC Educational Resources Information Center

    Pakiser, Louis C.

    One of a series of general interest publications on science topics, the booklet provides those interested in earthquakes with an introduction to the subject. Following a section presenting an historical look at the world's major earthquakes, the booklet discusses earthquake-prone geographic areas, the nature and workings of earthquakes, earthquake…

  8. Earthquakes.

    ERIC Educational Resources Information Center

    Walter, Edward J.

    1977-01-01

    Presents an analysis of the causes of earthquakes. Topics discussed include (1) geological and seismological factors that determine the effect of a particular earthquake on a given structure; (2) description of some large earthquakes such as the San Francisco quake; and (3) prediction of earthquakes. (HM)

  9. Combining Seismic Arrays to Image Detailed Rupture Properties of Large Earthquakes: Evidence for Frequent Triggering of Multiple Faults

    NASA Astrophysics Data System (ADS)

    Ishii, M.; Kiser, E.

    2010-12-01

    Imaging detailed rupture characteristics using the back-projection method, which time-reverses waveforms to their source, has become feasible in recent years due to the availability of data from large aperture arrays with dense station coverage. In contrast to conventional techniques, this method can quickly and indiscriminately provide the spatio-temporal details of rupture propagation. Though many studies have utilized the back-projection method with a single regional array, the limited azimuthal coverage often leads to skewed resolution. In this study, we enhance the imaging power by combining data from two arrays, i.e., the Transportable Array (TA) in the United States and the High Sensitivity Seismographic Network (Hi-net) in Japan. This approach suppresses artifacts and achieves good lateral resolution by improving distance and azimuthal coverage while maintaining waveform coherence. We investigate four large events using this method: the August 15, 2007 Pisco, Peru earthquake, the September 12, 2007 Southern Sumatra earthquake, the September 29, 2009 Samoa Islands earthquake, and the February 27, 2010 Maule, Chile earthquake. In every case, except the Samoa Islands event, the distance of one of the arrays from the epicenter requires us to use the direct P wave and core phases in the back-projection. One of the common features of the rupture characteristics obtained from the back-projection analysis is spatio-temporal rupture discontinuities, or discrete subevents. Both the size of the gaps and the timing between subevents suggest that multiple segments are involved during giant earthquakes, and that they trigger slip on other faults. For example, the 2009 Samoa Islands event began with a rupture propagating north for about 15 seconds followed by a much larger rupture that originated 30 km northwest of the terminus of the first event and propagated back toward the southeast. The involvement of multiple rupture segments with different slip characteristics suggest that large earthquakes are more complex compared to smaller events.

  10. Earthquakes

    ERIC Educational Resources Information Center

    Roper, Paul J.; Roper, Jere Gerard

    1974-01-01

    Describes the causes and effects of earthquakes, defines the meaning of magnitude (measured on the Richter Magnitude Scale) and intensity (measured on a modified Mercalli Intensity Scale) and discusses earthquake prediction and control. (JR)

  11. Earthquakes

    MedlinePLUS

    ... Winter Weather Information on Specific Types of Emergencies Earthquakes Language: English Español (Spanish) Recommend on Facebook Tweet ... even building collapse) if you immediately: Before an Earthquake Being Prepared Emergency Supplies Home Hazards During an ...

  12. Rupture Pomess of Four Medium Size Earthquakes That Occurred in the Gulf of California

    NASA Astrophysics Data System (ADS)

    Rodriguez-Lozoya, H. E.; Rebollar, C. J.; Quintanar, L.

    2005-12-01

    Four earthquakes with magnitudes of 5.3, 5.6, 6.1 and 6.2 located in the Gulf of California Extensional Province were studied to obtain their rupture process. A network of broadband seismic stations located around the Gulf of California recorded the events (NARS-Baja and RESBAN). Body waveform modeling and the inversion of the seismic moment tensor were used to obtain the fault geometry. From forward body waveform modeling and from the time-domain moment tensor inversion we obtained source depths in the range from 4 to 6 km. We used Yagi et al. (1999) inversion code to invert near-source broadband and strong-ground-motion waveforms to get the spatial slip distribution over the fault. We found that the source rupture process of the magnitude 5.3 and 5,6 have simple moment-rate functions and source time duration of 10 and 17 seconds respectively. Magnitude 5.3 event was a normal event and magnitude 5.6 was a right lateral strike-slip event. Magnitude 6.1 and 6.3 were right lateral strike-slip events with a complex rupture process with three sources of seismic moment release. Time duration of these events were 30 and 35 seconds respectively. Time duration of the moment-rate functions are large compared with similar magnitude events calculated elsewhere, we think that this is because we are inverting a large window of the seismogram that contain energy that it is not seen at regional distances or teleseismic distances.

  13. Analysis in natural time domain of geoelectric time series monitored prior two strong earthquakes occurred in Mexico

    NASA Astrophysics Data System (ADS)

    Ramrez-Rojas, A.; Flores-Marquez, L. E.

    2009-12-01

    The short-time prediction of seismic phenomena is currently an important problem in the scientific community. In particular, the electromagnetic processes associated with seismic events take in great interest since the VAN method was implemented. The most important features of this methodology are the seismic electrical signals (SES) observed prior to strong earthquakes. SES has been observed in the electromagnetic series linked to EQs in Greece, Japan and Mexico. By mean of the so-called natural time domain, introduced by Varotsos et al. (2001), they could characterize signals of dichotomic nature observed in different systems, like SES and ionic current fluctuations in membrane channels. In this work we analyze SES observed in geoelectric time series monitored in Guerrero, Mxico. Our analysis concern with two strong earthquakes occurred, on October 24, 1993 (M=6.6) and September 14, 1995 (M=7.3). The time series of the first one displayed a seismic electric signal six days before the main shock and for the second case the time series displayed dichotomous-like fluctuations some months before the EQ. In this work we present the first results of the analysis in natural time domain for the two cases which seems to be agreeing with the results reported by Varotsos. P. Varotsos, N. Sarlis, and E. Skordas, Practica of the Athens Academy 76, 388 (2001).

  14. Earthquakes.

    PubMed

    Briggs, Susan M

    2006-06-01

    Major earthquakes have the potential to be one of the most catastrophic natural disasters affecting mankind. Earthquakes of significant size threaten lives and damage property by setting off a chain of events that disrupts all aspects of the environment and significantly impacts the public health and medical infrastructures of the affected region. This article provides an overview of basic earthquake facts and relief protocol for medical personnel. PMID:16781268

  15. Solar wind ion density variations that preceded the M6+ earthquakes occurring on a global scale between 3 and 15 September 2013

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2015-04-01

    Between 3 and 15 September 2013 on Earth were recorded nine M6+ earthquakes: Canada M6,1 earthquake occurred on 3 September at 20:19 UTC; Japan M6,5 earthquake occurred on 4 September at 00:18 UTC; Canada M6,0 earthquake occurred on 4 September at 00:23 UTC; Alaska M6,5 earthquake occurred on 4 September at 02:32 UTC; Alaska M6,0 earthquake occurred on 4 September at 06:27 UTC; Northern Mid-Atlantic Ridge M6,0 earthquake occurred on 5 September at 04:01 UTC; Guatemala M6,4 earthquake occurred on 7 September at 00:13 UTC; Central East Pacific Rise M6,1 earthquake occurred on 11 September at 12:44 UTC; Alaska M6,1 earthquake occurred on 15 September at 16:21 UTC. The authors analyzed the modulation of solar wind ion density during the period from 1 to 18 September 2013 to determine whether the nine earthquakes were preceded by a variations of the solar wind ion density and for testing a method to be applied in the future also for the prediction of tsunami. The data on ion density used to realize the correlation study are represented by: solar wind ion density variation detected by ACE (Advanced Composition Explorer) Satellite, in orbit near the L1 Lagrange point, at 1.5 million of km from Earth, in direction of the Sun. The instrument used to perform the measurement of the solar wind ion density is the Electron, Proton, and Alpha Monitor (EPAM) instrument, equipped on the ACE Satellite. To conduct the study, the authors have taken in consideration the variation of the solar wind protons density that have these characteristics: differential proton flux 1060-1900 keV (p/cm^2-sec-ster-MeV); differential proton flux 761-1220 keV (p/cm^2-sec-ster-MeV); differential proton flux 310-580 keV (p/cm^2-sec-ster-MeV) and differential proton flux 115-195 keV (p/cm^2-sec-ster-MeV). This data set has been marked with the times (time markers) of M6+ earthquakes occurred on a global scale (the data on M6+ seismic activity are provided in real time by USGS, INGV and the CSEM) between 3 and 15 September 2013. The result of the analysis showed that the nine M6+ earthquakes occurred on a global scale in the time period taken as a reference, were preceded by a significant variation of the solar wind proton density to which was superimposed on a coronal mass ejection (CME) that reached the Earth on September 1, 2013 at 09:19 UTC (± 6 hours, iSWA data). The CME event preceded the first earthquake taken in reference (Canada M6,1 earthquake occurred on September 3 at 20:19 UTC) of about 59 hours.

  16. Location and source properties for the earthquake sequence occurred in the Western Getic Depression (Romania), December 2011 - January 2012

    NASA Astrophysics Data System (ADS)

    Borleanu, Felix; Popescu, Emilia; Diaconescu, Mihai; Radulian, Mircea

    2013-04-01

    A crustal earthquake sequence (40 earthquakes detected and located between 30 December 2011and 10 January 2012) was recently reported in the weastern part of the Getic Depression (about 20 km east from the Tg-Jiu city). The main shock, occurred on January 1, 2012, 23:57 (45.04, 23.56, h=14 km, MD = 4.5) was preceded by 7 foreshocks (MD less than 3.6) within 65-hour interval. The largest aftershocks of magnitude 4.0 and 3.9 occurred within the first 30-minute interval. Seismic source properties are determined using multiple approaches: empirical Green's functions (EGF) deconvolution, spectral ratios technique and acceleration spectra analysis. For EGF and spectral ratios application, we selected co-located foreshocks and aftershocks (2.1 ? MD ? 4.0) in association to the main event (MD = 4.5). Two different methods were used to calculate the focal mechanism: a method using the polarities of Pg and Pn waves and the other one representing the waveform inversion of moment tensors. Our analysis reveals distinct features, such as the alignment of the foreshocks and aftershocks along a NW-SE direction. The focal mechanisms computed for the three largest events using both techniques are similar, showing a rupture plane in the same NW-SE direction. The relative location of the main shock indicates a unilateral rupture, from SE toward NW. In parallel, source parameters are retrieved from the analysis of the accelerometer spectra. The resulted source time functions are similar from one station to the other, suggesting negligible source directivity effects for the study events. The shape of the deconvolved source time function for the main shock of 1 January 2012 indicates a homogeneous rupture process in the focus.

  17. Large submarine earthquakes that occurred worldwide in a 1-year period (June 2013 to June 2014) - a contribution to the understanding of tsunamigenic potential

    NASA Astrophysics Data System (ADS)

    Omira, R.; Vales, D.; Marreiros, C.; Carrilho, F.

    2015-10-01

    This paper is a contribution to a better understanding of the tsunamigenic potential of large submarine earthquakes. Here, we analyze the tsunamigenic potential of large earthquakes which have occurred worldwide with magnitudes around Mw = 7.0 and greater during a period of 1 year, from June 2013 to June 2014. The analysis involves earthquake model evaluation, tsunami numerical modeling, and sensors' records analysis in order to confirm the generation of a tsunami (or lack thereof) following the occurrence of an earthquake. We also investigate and discuss the sensitivity of tsunami generation to the earthquake parameters recognized to control tsunami occurrence, including the earthquake location, magnitude, focal mechanism and fault rupture depth. Through this analysis, we attempt to understand why some earthquakes trigger tsunamis and others do not, and how the earthquake source parameters are related to the potential of tsunami generation. We further discuss the performance of tsunami warning systems in detecting tsunamis and disseminating the alerts. A total of 23 events, with magnitudes ranging from Mw = 6.7 to Mw = 8.1, have been analyzed. This study shows that about 39 % of the analyzed earthquakes caused tsunamis that were recorded by different sensors with wave amplitudes varying from a few centimeters to about 2 m. Tsunami numerical modeling shows good agreement between simulated waveforms and recorded waveforms, for some events. On the other hand, simulations of tsunami generation predict that some of the events, considered as non-tsunamigenic, caused small tsunamis. We find that most generated tsunamis were caused by shallow earthquakes (depth < 30 km) and thrust faults that took place on/near the subduction zones. The results of this study can help the development of modified and improved versions of tsunami decision matrixes for various oceanic domains.

  18. Earthquake!

    ERIC Educational Resources Information Center

    Hernandez, Hildo

    2000-01-01

    Examines the types of damage experienced by California State University at Northridge during the 1994 earthquake and what lessons were learned in handling this emergency are discussed. The problem of loose asbestos is addressed. (GR)

  19. The C228T mutation of TERT promoter frequently occurs in bladder cancer stem cells and contributes to tumorigenesis of bladder cancer

    PubMed Central

    Du, Ying; He, Luyun; Cai, Zhiming; Wang, Jiansong; Fan, Zusen

    2015-01-01

    Bladder cancer is one of the most common malignant tumors worldwide. Bladder cancer stem cells (BCSCs) have been isolated recently but have not been defined yet. Here we sorted BCSCs from bladder tumor tissues or normal bladder stem cells (NBBCs) from adjacent normal bladder tissues. We found that the C228T mutation (chr5, 1, 295, 228 C > T) of TERT promoter frequently occurs in BCSCs, but not exist in NBBCs. Importantly, introducing the C228T mutation in NBBCs causes TERT overexpression and transformation of bladder cancer. Restoration of the C228T mutation to T228C in BCSCs can recover the TERT expression to a basal level and abolish tumor formation. Additionally, the C228T mutation of TERT promoter triggers TERT expression leading to increased telomerase activity. TERT expression levels are consistent with clinical severity and prognosis of bladder cancer. PMID:26143634

  20. The First Results of Testing Methods and Algorithms for Automatic Real Time Identification of Waveforms Introduction from Local Earthquakes in Increased Level of Man-induced Noises for the Purposes of Ultra-short-term Warning about an Occurred Earthquake

    NASA Astrophysics Data System (ADS)

    Gravirov, V. V.; Kislov, K. V.

    2009-12-01

    The chief hazard posed by earthquakes consists in their suddenness. The number of earthquakes annually recorded is in excess of 100,000; of these, over 1000 are strong ones. Great human losses usually occur because no devices exist for advance warning of earthquakes. It is therefore high time that mobile information automatic systems should be developed for analysis of seismic information at high levels of manmade noise. The systems should be operated in real time with the minimum possible computational delays and be able to make fast decisions. The chief statement of the project is that sufficiently complete information about an earthquake can be obtained in real time by examining its first onset as recorded by a single seismic sensor or a local seismic array. The essential difference from the existing systems consists in the following: analysis of local seismic data at high levels of manmade noise (that is, when the noise level may be above the seismic signal level), as well as self-contained operation. The algorithms developed during the execution of the project will be capable to be used with success for individual personal protection kits and for warning the population in earthquake-prone areas over the world. The system being developed for this project uses P and S waves as well. The difference in the velocities of these seismic waves permits a technique to be developed for identifying a damaging earthquake. Real time analysis of first onsets yields the time that remains before surface waves arrive and the damage potential of these waves. Estimates show that, when the difference between the earthquake epicenter and the monitored site is of order 200 km, the time difference between the arrivals of P waves and surface waves will be about 30 seconds, which is quite sufficient to evacuate people from potentially hazardous space, insertion of moderators at nuclear power stations, pipeline interlocking, transportation stoppage, warnings issued to rescue services and to administration by automatic transmission of SMS messages, etc. This recognition technique can also be used to filter the noise, since the noise aggregate characteristic for megacities, since the noise aggregate characteristic for megacities has typical characteristics (traffic, industry-caused vibrations, free oscillations of buildings, and so on). Analysis of the data shows that earthquakes and noise can be dealt with using a finite set of scenarios that characterize a mixture of the data and noise. In this way it becomes possible to develop an automatic system for detection and identification of low-energy earthquake phases in a noise that may even be above the signal level. Comparison of different methods employed for early warning of an occurring earthquake shows that the attainable accuracy of earthquake identification is 97%.

  1. Solar wind proton density variations that preceded the M6+ earthquakes occurring on a global scale between 17 and 20 April 2014

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2015-04-01

    Between 17 and 20 April 2014 on Earth were recorded six M6+ earthquakes: Balleny Islands region M6,2 earthquake occurred on 17 April at 15:06 UTC; Solomon Islands M6,1 earthquake occurred on 18 April at 04:13 UTC; Mexico M7,2 earthquake occurred on 18 April at 14:27 UTC; Papua New Guinea M6,6 earthquake occurred on 19 April at 01:04 UTC; Papua New Guinea M7,5 earthquake occurred on 19 April at 13:28 UTC; Papua New Guinea M6,2 earthquake occurred on 20 April at 00:15 UTC. The authors analyzed the modulation of solar wind ion density during the period from 14 to 23 April 2014 to determine whether the six earthquakes were preceded by a variations of the solar wind ion density and for testing a method to be applied in the future also for the prediction of tsunami. The data on ion density used to realize the correlation study are represented by: solar wind ion density variation detected by ACE (Advanced Composition Explorer) Satellite, in orbit near the L1 Lagrange point, at 1.5 million of km from Earth, in direction of the Sun. The instrument used to perform the measurement of the solar wind ion density is the Electron, Proton, and Alpha Monitor (EPAM) instrument, equipped on the ACE Satellite. To conduct the study, the authors have taken in consideration the variation of the solar wind protons density that have these characteristics: differential proton flux 1060-1900 keV (p/cm^2-sec-ster-MeV); differential proton flux 761-1220 keV (p/cm^2-sec-ster-MeV); differential proton flux 310-580 keV (p/cm^2-sec-ster-MeV) and differential proton flux 115-195 keV (p/cm^2-sec-ster-MeV). This data set has been marked with the time data (time markers) of M6+ earthquakes occurred on a global scale between 17 and 20 April 2014 (the data on M6+ seismic activity are provided in real time by USGS, INGV and CSEM). The result of the analysis showed that the six M6+ earthquakes occurred on a global scale in the time period taken as a reference, were preceded by a significant variation of the solar wind proton density started on April 17, 2014, approximately at 01:00 UTC. The beginning of this increase preceded the first seismic event taken in reference (Balleny Islands region M6,2 earthquake occurred on April 17 at 15:06 UTC) of about 14 hours.

  2. The reasons why the M9 earthquake in the northeastern Japan subduction zone could not be anticipated and why it really occurred

    NASA Astrophysics Data System (ADS)

    Matsuzawa, T.; Iio, Y.

    2011-12-01

    The M9 Tohoku earthquake on 11 March 2011 had a great impact on the seismologists all over the world. This is because the northeastern Japan subduction zone was one of the most investigated subduction zones and the interplate coupling there was thought to be too weak to generate M9 earthquakes. The bases of the judgment of weak coupling are as follows: (1) The portion of the Pacific plate subducting beneath the subduction zone is older than 100 my, which is older than most of the other ocean floors in the world. Note that although some researchers have casted doubt on the relationship between the M9 potential and plate convergence rate and back-arc spreading proposed by Ruff and Kanamori (1980) after the 2004 M9 Sumatra-Andaman earthquake (e.g., McCaffrey, 2007, 2008; Stein and Okal, 2007), the dependency on the age of the oceanic plate had not been rejected. (2) Around 100 year geodetic survey shows dilatational areal strain is dominant in Tohoku (northeastern Honshu, Japan) (Hashimoto, 1990; Ishikawa and Hashimoto, 1999), indicating all the 'locked' areas on the plate boundary might be loosened by M7 earthquakes occurring with repeating intervals of several tens of years. (3) Although the analyses of GPS (e.g., Suwa et al., 2006) and small repeating earthquake data (Uchida and Matsuzawa, 2011) indicate a large 'locked' area off southern Tohoku, the data in the late 2000s show large portions of the locked area seemed to be released by large earthquakes of M6-7 and their afterslip. (4) The activity of moderate-sized earthquakes there is the highest in Japan. (5) Large interplate earthquakes with M6 or larger are usually followed by large afterslip whose scalar moment is sometimes as large as that of the seismic slip of the main shock. Moreover, Hasegawa et al. (2011) shows that the stress on the plate boundary was not large according to the stress rotation after the M9 earthquake. All of these observations indicate that the plate boundary was not strongly locked over 100 years. Then why did the M9 earthquake really occur there? The reason is still under the debate. One of the probable explanations is that the plate boundary had been weakly coupled but the slip of the M9 earthquake was exceptionally large releasing total stress on the boundary. The Pacific plate descending beneath Tohoku is old and cold but the inclination of the plate is less than around 30 degrees and interplate earthquakes can occur as deep as 60 km because the plate is very cold. The shallow subduction angle and deep sesimogenic limit causesd the seismogenic plate boundary as wide as more than 200 km, which was large enough to accumulate slip deficit of more than 20m without large stress increase (Iio et al., 2011). Most of the aftershocks occurring in the hanging plate are of normal fault type (Asano et al., 2011) indicating the seismic slip of the M9 earthquake was overshot (Ide et al., 2011), which might be caused by thermal pressurization of pore fluid (Mitsui and Iio, 2011).

  3. Moment tensor inversion for two micro-earthquakes occurring inside the Háje gas storage facilities, Czech Republic

    NASA Astrophysics Data System (ADS)

    Benetatos, Christoforos; Málek, Jiří; Verga, Francesca

    2013-04-01

    Broadband data from the Příbram seismological network was used to investigate the source of two earthquakes, with magnitudes M w = 0.2 and 0.4 respectively, occurring in the period of October-November 2009 in the Háje natural gas storage area (Czech Republic). Both events were located inside the limits of the storage area and at depths similar to those of the underground caverns where the gas is stored. We applied an inversion technique using the software ISOLA for moment tensor retrieval in order to assess the source process of both events and recognize whether a significant isotropic component existed that could be interpreted as a possible cavern collapse. We also performed an uncertainty analysis so as to confirm the reliability of the focal mechanism solutions and we controlled the consistency between the inverted focal mechanisms and those calculated using the P-waves first motions. Our results showed that the nodal plane orientation, the centroid depth, and the magnitude remained stable. Furthermore, we calculated synthetic waveforms for collapse-type ruptures and compared them with the original records. The match between the synthetic and the original data was very poor supporting the interpretation of the shear character of the events. The combination of the inversion results, which indicated significant double-couple components and of the synthetic tests, which supported the inexistence of an isotropic component at the source, led to the conclusion that the possibility of rocks falling from the ceiling of the caverns or a cavern collapse is highly unlikely.

  4. On the behavior of site effects in central Mexico (the Mexican volcanic belt - MVB), based on records of shallow earthquakes that occurred in the zone between 1998 and 2011

    NASA Astrophysics Data System (ADS)

    Clemente-Chavez, A.; Zúñiga, F. R.; Lermo, J.; Figueroa-Soto, A.; Valdés, C.; Montiel, M.; Chavez, O.; Arroyo, M.

    2014-06-01

    The Mexican volcanic belt (MVB) is a seismogenic zone that transects the central part of Mexico with an east-west orientation. The seismic risk and hazard of this seismogenic zone has not been studied in detail due to the scarcity of instrumental data as well as because seismicity in the continental regime of central Mexico is not too frequent. However, it is known that there are precedents of large earthquakes (Mw > 6.0) that have taken place in this zone. The valley of Mexico City (VM) is the sole zone, within the MVB, that has been studied in detail. Studies have mainly focused on the ground amplification during large events such as the 1985 subduction earthquake that occurred off coast of Michoacán. The purpose of this article is to analyze the behavior of site effects in the MVB zone based on records of shallow earthquakes (data not reported before) that occurred in the zone between 1998 and 2011. We present a general overview of site effects in the MVB, a classification of the stations in order to reduce the uncertainty in the data when obtaining attenuation parameters in future works, as well as some comparisons between the information presented here and that presented in previous studies. A regional evaluation of site effects and Fourier acceleration spectrum (FAS) shape was estimated based on 80 records of 22 shallow earthquakes within the MVB zone. Data of 25 stations were analyzed. Site effects were estimated by using the horizontal-to-vertical spectral ratio (HVSR) methodology. The results show that seismic waves are less amplified in the northeast sites of the MVB with respect to the rest of the zone and that it is possible to classify two groups of stations: (1) stations with negligible site amplification (NSA) and (2) stations with significant site amplification (SSA). Most of the sites in the first group showed small (<3) amplifications while the second group showed amplifications ranging from 4 to 6.5 at frequencies of about 0.35, 0.75, 15 and 23 Hz. With these groups of stations, average levels of amplification were contrasted for the first time with those caused by the subduction zone earthquakes. With respect to the FAS shapes, most of them showed similarities at similar epicentral distances. Finally, some variations of site effects were found when compared to those obtained in previous studies on different seismicity regions. These variations were attributed to the location of the source. These aspects help to advance the understanding about the amplification behavior and of the expected seismic risk on central Mexico due to large earthquakes within the MVB seismogenic zone.

  5. Possible variations of altitude observed on the occasion of the Tohoku earthquake (M=9.0) occurred on March 11, 2011

    NASA Astrophysics Data System (ADS)

    Milillo, P.; Vespe, F.; Maggipinto, T.; Schiavulli, L.; Ligonzo, T.; Biagi, P. F.

    2012-04-01

    Since 2009 a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers was put into operation in Europe in order to study the disturbances produced by the earthquakes on the propagation of these signals. In 2011 the network was formed by nine receivers located three in Italy and one in Austria, Greece, Portugal, Romania, Russia, Turkey. Disturbances in the radio signals were observed after the occurrence of the Tohoku earthquake. These disturbances appeared clearly in some site and for some frequency. These disturbances cannot be connected directly with the processes occurred in the epicentral zone of the earthquake but they indicate the spreading of the disturbances produced in the atmosphere/ionosphere of the previous zone. On the contrary the Pacific radio network revealed disturbances 5-10 days before the occurrence of the earthquake and these disturbances are connected directly with processes occurred in the epicentral area. Since October 2010 a GPS receiver is into operation at Tokai (Japan) in an experiment on Neutrino Physics (T2K). The distance between the GPS receiver and the epicenter of the earthquake is about 350 km. The data collected by the receiver show an evident decrease in the altitude from the beginning of March 2011. This variation could be one of the mentioned processes. In order to confirm the effect we have analyzed the GPS data of the GSI (Geospatial Information Authority of Japan) network in the period January-April 2011. The results of this analysis are here presented.

  6. Investigation of geomagnetic field and hydro-geochemical precursors of several earthquakes occurred in the territory of Armenia and Iran

    NASA Astrophysics Data System (ADS)

    Yenanov, M.; Vardanyan, G.; Adibekyan, M.

    The seismic regime observations in the territory of Armenia are performed permanently on the seven geomagnetic and seven geochemical observation stations. The full T-vector and the gases, macro-components, micro-components and some parameters are daily investigated. All the regime geomagnetic field and geo-chemical observations are accompanied with metrological works on all the stages. All observation stations and drills are located in the zones of active faults. Selected location of observation stations and drills allows observing the geomagnetic and geochemical reaction on the earthquakes not only in the territory of Armenia but also in the territory of Turkey, Georgia, Azerbaijan and Iran. The relation between the change of geomagnetic full T-vector time series field and micro- and macro-components in underground waters and the process of strong seismic events preparing is well studied. A large amount of pre-, co-, and post-seismic anomalies of physical and chemical parameters of underground waters are defined, also defined the geomagnetic field peculiarities in the investigating area. With the aim to current seismic hazard assessment in the territory of Armenia and adjacent regions the research of geomagnetic and geochemical data was carried out and earthquake precursors had been distinguished. In this paper the techniques of data processing and results of analysis of geomagnetic field peculiarities and hydro-geochemical earthquake precursors.

  7. Fault modeling of the Mw 7.0 shallow intra-slab strike-slip earthquake occurred on 2011 July 10th using near-field tsunami record

    NASA Astrophysics Data System (ADS)

    Kubota, T.; Hino, R.; Iinuma, T.

    2014-12-01

    On 2011 July 10th, an earthquake of Mw 7.0 occurred in the shallow part of the Pacific slab beneath the large coseismic slip area of the 2011 Tohoku-Oki earthquake. This event has a strike-slip focal mechanism with steep dipping nodal planes. Near the epicenter, aftershocks determined by OBS deployment formed clear two orthogonal lineaments with identical strikes of the focal mechanism solution, suggesting that the aftershock activity occurred along the two conjugate faults. The strikes of these faults were almost parallel to the direction of the magnetic lineations and the fracture zones of the incoming Pacific plate, suggesting that the earthquake was the re-rupture of congenital fractures under the extensional stress induced by the Tohoku-Oki earthquake. It is of great interest to know the down-dip size of the source fault not only to understand the mechanical nature of the slab but also the post-2011 stress state. Coseismic seafloor deformation and tsunami associated with the earthquake were observed by ocean bottom pressure gauges deployed within ~ 100 km from the epicenter. We estimated the finite fault model of this event to discuss the rupture properties of the earthquake. We sought the source model assuming a rectangular fault with a uniform slip assuming the strike of the fault to be one of those of two nodal planes of the focal mechanism. The two preferable source models corresponding to the two nodal planes explained the observed data equally well. For either model, the depth of the downdip end exceeds 40 km below the plate boundary, meaning the fault widths (down-dip size) were much larger than the depth extent of the aftershock distribution (~ 15 km). We sought another source model assuming the simultaneous rupture of the conjugate faults and found that the width of the fault model was more consistent with the aftershock distribution than the single rupture plane models. The 2011 intraslab strike-slip earthquake might be a compound rupture of the spreading-related fracture and the transform fault like fracture within the subducting Pacific slab.

  8. On the behavior of site effects in Central Mexico (the Mexican Volcanic Belt - MVB), based on records of shallow earthquakes that occurred in the zone between 1998 and 2011

    NASA Astrophysics Data System (ADS)

    Clemente-Chavez, A.; Zúñiga, F. R.; Lermo, J.; Figueroa-Soto, A.; Valdés, C.; Montiel, M.; Chavez, O.; Arroyo, M.

    2013-11-01

    The Mexican Volcanic Belt (MVB) is a seismogenic zone that transects the central part of Mexico with an east-west orientation. The risk and hazard seismic of this seismogenic zone has not been studied at detail due to the scarcity of instrumental data as well as because seismicity in the continental regimen of Central Mexico is not too frequent, however, it is known that there are precedents of large earthquakes (Mw > 6.0) that have taken place in this zone. The Valley of Mexico City (VM) is the sole zone, within the MVB, which has been studied in detail; mainly focusing on the ground amplification during large events such as the 1985 subduction earthquake that occurred in Michoacan. The purpose of this article is to analyze the behavior of site effects in the MVB zone based on records of shallow earthquakes (data not reported before) that occurred in the zone between 1998 and 2011. We present a general overview of site effects on the MVB, a classification of the stations in order to reduce the uncertainty in the data to obtain attenuation parameters in future works, and some comparisons between the information presented here and that presented in previous studies. A regional evaluation of site effects and Fourier Acceleration Spectrum (FAS) shape was estimated based on 80 records of 22 shallow earthquakes within the MVB zone. Data of 25 stations were analyzed. Site effects were estimated by using the Horizontal-to-Vertical Spectral Ratio (HVSR) methodology. The results show that seismic waves are less amplified in the northeast sites of the MVB with respect to the rest of the zone and that it is possible to classify two groups of stations: (1) stations with Negligible Site Amplification (NSA) and (2) stations with Significant Site Amplification (SSA). Most of the sites in the first group showed small (< 3) amplifications while the second group showed amplifications ranging from 4 to 6.5 at frequencies of about 0.35, 0.75, 15 and 23 Hz. With these groups of stations, average levels of amplification were contrasted for the first time with those caused by the subduction zone earthaquakes. With respect to the FAS shapes, most of them showed similarities at similar epicentral distances. Finally, some variations of site effects were found when compared to those obtained in previous studies on different seismicity regions. These variations were attributed to the location of the source. These aspects help to advance the understanding about the amplification behavior and of the expected seismic risk on the Central Mexico due to large earthquakes within the MVB seismogenic zone.

  9. Unexpectedly frequent occurrence of very small repeating earthquakes (-5.1 ≤ Mw ≤ -3.6) in a South African gold mine: Implications for monitoring intraplate faults

    NASA Astrophysics Data System (ADS)

    Naoi, Makoto; Nakatani, Masao; Igarashi, Toshihiro; Otsuki, Kenshiro; Yabe, Yasuo; Kgarume, Thabang; Murakami, Osamu; Masakale, Thabang; Ribeiro, Luiz; Ward, Anthony; Moriya, Hirokazu; Kawakata, Hironori; Nakao, Shigeru; Durrheim, Raymond; Ogasawara, Hiroshi

    2015-12-01

    We observed very small repeating earthquakes with -5.1 ≤ Mw ≤ -3.6 on a geological fault at 1 km depth in a gold mine in South Africa. Of the 851 acoustic emissions that occurred on the fault during the 2 month analysis period, 45% were identified as repeaters on the basis of waveform similarity and relative locations. They occurred steadily at the same location with similar magnitudes, analogous to repeaters at plate boundaries, suggesting that they are repeat ruptures of the same asperity loaded by the surrounding aseismic slip (background creep). Application of the Nadeau and Johnson (1998) empirical formula (NJ formula), which relates the amount of background creep and repeater activity and is well established for plate boundary faults, to the present case yielded an impossibly large estimate of the background creep. This means that the presently studied repeaters were produced more efficiently, for a given amount of background creep, than expected from the NJ formula. When combined with an independently estimated average stress drop of 16 MPa, which is not particularly high, it suggests that the small asperities of the presently studied repeaters had a high seismic coupling (almost unity), in contrast to one physical interpretation of the plate boundary repeaters. The productivity of such repeaters, per unit background creep, is expected to increase strongly as smaller repeaters are considered (∝ Mo -1/3 as opposed to Mo -1/6 of the NJ formula), which may be usable to estimate very slow creep that may occur on intraplate faults.

  10. Temporal and Spatial Evolution of Anisotropic Parameters before and after the Earthquake Occurred in the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    SHI, Y.; Liu, L.; Gao, Y.

    2013-12-01

    Shear-wave splitting (SWS) due to stress-aligned anisotropy have been widely observed and extensively used to determine the stress state or material property anisotropy in the shallow crust. It is generally accepted that the polarization of the fast shear-wave indicates the orientation of the aligned micro-cracks in the rock, and the time-delays of slow shear-wave splitting estimate the density of micro-cracks, and bring with information of stress accumulation and temporal variation in the crust. However, the temporal and spatial characteristic of crustal anisotropy is very constrained by the limited distributions of stations and seismicity. In addition, the strict requirement of shear-wave window and the availability of high-quality events literally restrict the crustal anisotropy research. The seismic wave's propagation, as an effective method, is used for geological structure research, but also for the analysis of rock properties. At present, the most widely used simulation approach for seismic anisotropy study is the adoption of transversely isotropic medium. Whereas the realistic complex crustal anisotropic structure of typical activated regions cannot be explained at first order by the transversely isotropic medium. The earth media, especially in certain active tectonic deformation zones, can be regarded as inhomogeneous with directivities under the action of local stress field. It is equivalent to take that anisotropy medium as directive heterogeneity. In this research, anisotropic medium be regarded as the directional arrangement of molecular scale heterogeneity and be described by heterogeneous medium in a large scale. We use the isotropic PSTD algorithm to conduct the simulation. Through numerical simulation with PSTD technique, we get the anisotropic characteristics in the equivalency of the inhomogeneous medium, which build by the correlation length and variation of radon velocity. The San Andreas Fault (SAF) is one of the most renowned faults in the world due to the 1906 San Francisco earthquake. The SWS research at the vicinity of the Parkfield of SAF show the orientations of fast shear-wave for stations on the main fault associated with the strike main fault. In addition, outside of the fault zone, the orientations of fast shear wave are preferentially oriented parallel to the orientation of regional principle compressive stress. In the study, based on the distribution of crustal anisotropy parameter by analyzing SWS from local earthquake data prior to and following the 28 September 2004 Parkfield M6.0 earthquakes as the priori information, arranging each isotropic media unit as a complex structure with the constraint of velocity structure and geometry of the faults, we construct a complex anisotropic model and simulate the characteristic of wave's propagation in this model. Finally, comparing the anisotropic characteristic of simulated seismic wave with the observed seismic wave, we get a more accurate and reasonable variety characteristics of anisotropic parameters, and then we will discuss the temporal and spatial evolution of anisotropic parameters before and after the before and after the big earthquake.

  11. Biased hypermutation occurred frequently in a gene inserted into the IC323 recombinant measles virus during its persistence in the brains of nude mice

    SciTech Connect

    Otani, Sanae; Ayata, Minoru; Takeuchi, Kaoru; Takeda, Makoto; Shintaku, Haruo; Ogura, Hisashi

    2014-08-15

    Measles virus (MV) is the causative agent of measles and its neurological complications, subacute sclerosing panencephalitis (SSPE) and measles inclusion body encephalitis (MIBE). Biased hypermutation in the M gene is a characteristic feature of SSPE and MIBE. To determine whether the M gene is the preferred target of hypermutation, an additional transcriptional unit containing a humanized Renilla reniformis green fluorescent protein (hrGFP) gene was introduced into the IC323 MV genome, and nude mice were inoculated intracerebrally with the virus. Biased hypermutation occurred in the M gene and also in the hrGFP gene when it was inserted between the leader and the N gene, but not between the H and L gene. These results indicate that biased hypermutation is usually found in a gene whose function is not essential for viral proliferation in the brain and that the location of a gene in the MV genome can affect its mutational frequency. - Highlights: • Wild-type MV can cause persistent infections in nude mice. • Biased hypermutation occurred in the M gene. • Biased hypermutation occurred in an inessential gene inserted between the leader and the N gene.

  12. Solar wind proton density variations that preceded the M6,1 earthquake occurred in New Caledonia on November 10, 2014

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2015-04-01

    This work analyzed the modulation of the solar wind proton density variation that preceded the M6,1 earthquake occurred in New Caledonia on November 10, 2014 at 10:04:21 UTC. The purpose of the study has been to verify the existence of a correlation between solar activity and the earthquake and for testing a method to be applied in the future also for the prediction of tsunami. The ionic data used to realize the correlation study are represented by: solar wind ion density variation detected by ACE (Advanced Composition Explorer) Satellite, in orbit near the L1 Lagrange point, at 1.5 million of km from Earth, in direction of the Sun. The instrument used to perform the measurement of the solar wind ion density is the Electron, Proton, and Alpha Monitor (EPAM) instrument, equipped on the ACE Satellite. To conduct the study, the authors have taken in consideration the variation of the solar wind protons density that have these characteristics: differential proton flux 1060-1900 keV (p/cm^2-sec-ster-MeV); differential proton flux 761-1220 keV (p/cm^2-sec-ster-MeV); differential proton flux 310-580 keV (p/cm^2-sec-ster-MeV) and differential proton flux 115-195 keV (p/cm^2-sec-ster-MeV). The sample data used to conduct the study refers the period going from 7 to 10 November 2014. The data on the M6,1 earthquake are provided in real time by the USGS (United States Geological Survey). The data analysis revealed that the M6,1 earthquake occurred in New Caledonia on November 10, 2014 at 10:04:21 UTC, was preceded by a solar coronal mass ejection (CME) that reached Earth at 19:31:04 UTC (± 6 hours, ISWA data) on November 9, 2014. The CME event produced an increase of solar wind ion density that preceded the earthquakes of about 14.5 hours.

  13. Earthquake prediction

    SciTech Connect

    Ma, Z.; Fu, Z.; Zhang, Y.; Wang, C.; Zhang, G.; Liu, D.

    1989-01-01

    Mainland China is situated at the eastern edge of the Eurasian seismic system and is the largest intra-continental region of shallow strong earthquakes in the world. Based on nine earthquakes with magnitudes ranging between 7.0 and 7.9, the book provides observational data and discusses successes and failures of earthquake prediction. Derived from individual earthquakes, observations of various phenomena and seismic activities occurring before and after earthquakes, led to the establishment of some general characteristics valid for earthquake prediction.

  14. Simulation of a step by step prediction of the M=4.7 earthquake occurred in central Italy on August 22, 2005

    NASA Astrophysics Data System (ADS)

    Biagi, P. F.; Maggipinto, T.; Castellana, L.; Ermini, A.

    2009-04-01

    From 2002, a VLF-LF radio receiver is into operation in Bari (southern Italy). The intensity of the signals transmitted by GB (f=16 kHz, United Kingdom), FR (f=20.9 kHz, France), GE (f=23.4 kHz, Germany), IC (f=37.5 kHz, Island) and IT (f=54 kHz, Sicily, Italy) has been monitored with a 5s sampling rate. On August 19, 2005 a clear drop in the intensity of the FR radio signal appeared. Here a possible seismic prediction based on this drop considered as a precursor is presented. At first the probability that the drop could be connected to the seismicity was evaluated on the basis of the previous data analysis. Then, the analysis for defining time occurrence, location and magnitude of the forthcoming earthquake was undergone. The results have indicated a good probability for the occurrence within 15 days of an earthquake with M in the range 4.5-5.5 in the Colli Albani (near Rome) seismogenetic area. A fundamental rule in the precise definition of the epicentral zone was the indication of anomalies in the Radon content in air revealed in this zone by a station for monitoring the environmental radioactivity. On August 22, 2005 an earthquake with M = 4.7 occurred in the Anzio (near Rome) offshore area. The epicenter is inside the 5Th Fresnel zone of the FR radio signal and it is located 5 miles from the Tor Caldara "Diffuse Degassing Structure" where the Radon content in air is sampled by researchers of the INGV (National Institute of Geophysics and Volcanology).

  15. Winter Weather Frequently Asked Questions

    MedlinePLUS

    ... Health Matters What's New Preparation & Planning Disasters & Severe Weather Earthquakes Extreme Heat Floods Hurricanes Landslides Tornadoes Tsunamis ... Weather Information on Specific Types of Emergencies Winter Weather Frequently Asked Questions Language: English Español (Spanish) Recommend ...

  16. Subionospheric VLF/LF radio waves propagation characteristics before, during and after the Sofia, Bulgaria Mw=5.6 earthquake occurred on 22 May 2012

    NASA Astrophysics Data System (ADS)

    Moldovan, Iren Adelina; Emilian Toader, Victorin; Nenovski, Petko; Biagi, Pier Francesco; Maggipinto, Tommaso; Septimiu Moldovan, Adrian; Ionescu, Constantin

    2013-04-01

    In 2009, INFREP, a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers, was put into operation in Europe having as principal goal, the study of disturbances produced by the earthquakes on the propagation properties of these signals. On May 22nd, 2012 an earthquake with Mw=567 occurred in Bulgaria, near Sofia, inside the "sensitive" area of the INFREP VLF/LF electromagnetic network. The data collected on different frequencies, during April-May 2012 were studied using different methods of analysis: daily correlation methods, spectral approaches and terminator time techniques, in order to find out possible connections between the seismic activity and the subionospheric propagation properties of radio waves. The studies were performed with the help of a specially designed LabVIEW application, which accesses the VLF/LF receiver through internet. This program opens the receiver's web-page and automatically retrieves the list of data files to synchronize the user-side data with the receiver's data. Missing zipped files are also automatically downloaded. The application performs primary, statistical correlation and spectral analysis, appends daily files into monthly and annual files and performs 3D colour-coded maps with graphic representations of VLF and LF signals' intensities versus the minute-of-the-day and the day-of-the-month, facilitating a near real-time observation of VLF and LF electromagnetic waves' propagation. Another feature of the software is the correlation of the daily recorded files for the studied frequencies by overlaying the 24 hours radio activity and taking into account the sunrise and sunset. Data are individually processed (spectral power, correlations, differentiation, filtered using bandpass, lowpass, highpass). JTFA spectrograms (Cone-Shaped Distribution CSD, Gabor, Wavelet, short-time Fourier transform STFT, Wigner-Ville Distribution WVD, Choi-Williams Distribution CWD) are used, too.

  17. Safety and survival in an earthquake

    USGS Publications Warehouse

    U.S. Geological Survey

    1969-01-01

    Many earth scientists in this country and abroad are focusing their studies on the search for means of predicting impending earthquakes, but, as yet, an accurate prediction of the time and place of such an event cannot be made. From past experience, however, one can assume that earthquakes will continue to harass mankind and that they will occur most frequently in the areas where they have been relatively common in the past. In the United States, earthquakes can be expected to occur most frequently in the western states, particularly in Alaska, California, Washington, Oregon, Nevada, Utah, and Montana. The danger, however, is not confined to any one part of the country; major earthquakes have occurred at widely scattered locations.

  18. Self-similar rupture implied by scaling properties of volcanic earthquakes occurring during the 2004-2008 eruption of Mount St. Helens, Washington

    NASA Astrophysics Data System (ADS)

    Harrington, Rebecca M.; Kwiatek, Grzegorz; Moran, Seth C.

    2015-07-01

    We analyze a group of 6073 low-frequency earthquakes recorded during a week-long temporary deployment of broadband seismometers at distances of less than 3 km from the crater at Mount St. Helens in September of 2006. We estimate the seismic moment (M0) and spectral corner frequency (f0) using a spectral ratio approach for events with a high signal-to-noise (SNR) ratio that have a cross-correlation coefficient of 0.8 or greater with at least five other events. A cluster analysis of cross-correlation values indicates that the group of 421 events meeting the SNR and cross-correlation criteria forms eight event families that exhibit largely self-similar scaling. We estimate the M0 and f0 values of the 421 events and calculate their static stress drop and scaled energy (ER/M0) values. The estimated values suggest self-similar scaling within families, as well as between five of eight families (i.e., M0∝f0-3 and ER/M0∝ constant). We speculate that differences in scaled energy values for the two families with variable scaling may result from a lack of resolution in the velocity model. The observation of self-similar scaling is the first of its kind for such a large group of low-frequency volcanic tectonic events occurring during a single active dome extrusion eruption.

  19. Non-double-couple mechanism of moderate earthquakes occurred in Lower Siang region of Arunachal Himalaya: Evidence of factors affecting non-DC

    NASA Astrophysics Data System (ADS)

    Kumar, Rohtash; Gupta, S. C.; Kumar, Arjun

    2015-02-01

    Moment Tensor solutions of 104 earthquakes which were observed at local distances in Lower Siang region of Arunachal Himalaya have been estimated using ISOLA code. The magnitude range of analyzed earthquakes lies between 1.8 (Mw) and 5.3 (Mw). Out of 104 earthquakes, only 32 events are having good data. The signal noise ratio of these 32 events is greater than 6 with magnitude greater than 2.5. All possible sources of non-DC such as, noise present in the data, depth of the source, low azimuthal coverage of the event and non-DC as a part of real earthquake source process are examined. The study reveals that non-DC is highly dependent on the source depth as comparatively shallow events shows high CLVD%. The CLVD is also highly affected by the noise present in the data. Another factor is the magnitude of the event. The high magnitude event shows quite high DC%. So the source mechanisms of high magnitude events are double couple (DC).

  20. Threat of an earthquake right under the capital in Japan

    USGS Publications Warehouse

    Rikitake, T.

    1990-01-01

    Tokyo, Japan's capital, has been enjoying a seismically quiet period following the 1923 Kanto earthquake of magnitude 7.9 that killed more than 140,000 people. Such a quiet period seems likely to be a repetition of the 80-year quiescence after the great 1703 Genroku earthquake of magntidue 8.2 that occurred in an epicentral area adjacent to that of the 1923 Kanto earthquake. In 1784, seismic activity immediately under the capital area revived with occasional occurrence of magnitude 6 to 7 shocks. Earthquakes of this class tended to occur more frequently as time went on and they eventually culminated in the 1923 Kanto earthquake. As more than 60 years have passed since the Kanto earthquake, we may well expect another revival of activity immediately under the capital area.

  1. Seismic ACROSS Transmitter Installed at Morimachi above the Subducting Philippine Sea Plate for the Test Monitoring of the Seismogenic Zone of Tokai Earthquake not yet to Occur

    NASA Astrophysics Data System (ADS)

    Kunitomo, T.; Kumazawa, M.; Masuda, T.; Morita, N.; Torii, T.; Ishikawa, Y.; Yoshikawa, S.; Katsumata, A.; Yoshida, Y.

    2008-12-01

    Here we report the first seismic monitoring system in active and constant operation for the wave propagation characteristics in tectonic region just above the subducting plate driving the coming catastrophic earthquakes. Developmental works of such a system (ACROSS; acronym for Accurately Controlled, Routinely Operated, Signal System) have been started in 1994 at Nagoya University and since 1996 also at TGC (Tono Geoscience Center) of JAEA promoted by Hyogoken Nanbu Earthquakes (1995 Jan.17, Mj=7.3). The ACROSS is a technology system including theory of signal and data processing based on the brand new concept of measurement methodology of Green function between a signal source and observation site. The works done for first generation system are reported at IWAM04 and in JAEA report (Kumazawa et al.,2007). The Meteorological Research Institute of JMA has started a project of test monitoring of Tokai area in 2004 in corporation with Shizuoka University to realize the practical use of the seismic ACROSS for earthquake prediction researches. The first target was set to Tokai Earthquake not yet to take place. The seismic ACROSS transmitter was designed so as to be appropriate for the sensitive monitoring of the deep active fault zone on the basis of the previous technology elements accumulated so far. The ground coupler (antenna) is a large steel-reinforced concrete block (over 20m3) installed in the basement rocks in order to preserve the stability. Eccentric moment of the rotary transmitter is 82 kgm at maximum, 10 times larger than that of the first generation. Carrier frequency of FM signal for practical use can be from 3.5 to 15 Hz, and the signal phase is accurately controlled by a motor with vector inverter synchronized with GPS clock with a precision of 10-4 radian or better. By referring to the existing structure model in this area (Iidaka et al., 2003), the site of the transmitting station was chosen at Morimachi so as to be appropriate for detecting the reflected wave from an anticipated fault plane of Tokai Earthquake, the boundary between Eurasian lithosphere and the subducting Philippine Sea Plate. Further several trials of new transmission protocol and also remote control are being made for the transmitter network of the next generation. The whole system appears working well as reported by Yoshida et al. (2008, This meeting).

  2. Earthquake clusters in Corinth Rift

    NASA Astrophysics Data System (ADS)

    Mesimeri, Maria; Papadimitriou, Eleftheria; Karakostas, Vasilios; Tsaklidis, George

    2013-04-01

    Clusters commonly occur as main shock-aftershock (MS-AS) sequences but also as earthquake swarms, which are empirically defined as an increase in seismicity rate above the background rate without a clear triggering main shock earthquake. Earthquake swarms occur in a variety of different environments and might have a diversity of origins, characterized by a high b-value in their magnitude distribution. The Corinth Rift, which was selected as our target area, appears to be the most recent extensional structure, with a likely rate of fault slip of about 1cm/yr and opening of 7mm/yr. High seismic activity accommodates the active deformation with frequent strong (M≥6.0) events and several seismic excitations without a main shock with clearly discriminative magnitude. Identification of earthquake clusters that occurred in this area in last years and investigation of their spatio-temporal distribution is attempted, with the application of known declustering algorithms, aiming to associate their occurrence with certain patterns in seismicity behavior. The earthquake catalog of the National Hellenic Seismological Network is used, and a certain number of clusters were extracted from the dataset, with the MS-AS sequences being distinguished from earthquake swarms. Spatio-temporal properties of each subset were analyzed in detail, after determining the respective completeness magnitude. 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 statistical physics - Application to the geodynamic system of the Hellenic Arc, SEISMO FEAR HELLARC".

  3. Real Earthquakes, Real Learning

    ERIC Educational Resources Information Center

    Schomburg, Aaron

    2003-01-01

    One teacher took her class on a year long earthquake expedition. The goal was to monitor the occurrences of real earthquakes during the year and mark their locations with push pins on a wall-sized world map in the hallway outside the science room. The purpose of the project was to create a detailed picture of the earthquakes that occurred

  4. How fault geometric constraints and structural complexity effect earthquake frequency-size relations and maximum earthquake size

    NASA Astrophysics Data System (ADS)

    Zielke, O.; Arrowsmith, R.

    2009-12-01

    Assessing the potential size and recurrence statistics of future earthquakes along an active (strike-slip) fault is required for seismic hazard analysis, formulation of building codes, and emergency response planning. It also addresses the basic scientific question of how faults behave seismically i.e., how well fault behavior is currently understood. The first step in this assessment is an analysis of seismic and paleoseismic records to determine size and frequency of past earthquakes along a fault. However, for most tectonically active faults, these records are only partially helpful. Spanning not even a single seismic cycle, they contain little information about recurrence probability of the largest earthquakes. Additional means to assess potential size and probability of future (large) earthquakes are necessary. Empirical relationships, derived from historic earthquakes, revealed that earthquake size is proportional to rupture area. Therefore, the size of the largest earthquakes that may occur along a fault is constraint by its size (fault length and width). Geologic data show that faults evolve over time, growing laterally and becoming straighter as more and more slip is accumulated along them. Maximum earthquake size and seismic behavior thus change at geologic time scales as fault geometry and structural maturity evolve. Based on numerical earthquake simulations (FIMozFric -a quasi-static simulator implementing non-planar fault surfaces and depth-dependent coseismic stress drop), we show how fault geometric constraints (e.g., fault size and aspect ratio of fault length to width) and structural maturity of strike-slip faults(e.g., fault roughness and curvature) effect a) earthquake frequency-size relation and maximum earthquake size i.e., the recurrence probability of future earthquakes, b) fault segmentation, and c) along-fault slip accumulation: Bimodality in frequency-size relation (small earthquakes following Gutenberg-Richter relation, large i.e., characteristic earthquakes more frequent then anticipated from GR), respective threshold magnitude (change from small to large earthquakes), characteristic earthquake size, and fault segment size increase with increasing structural maturity. Geometrical constraints (i.e., aspect ratio), further affected by structural maturity, put a limit on fault segment size and therefore on characteristic earthquake size. Slip accumulation patterns also change with geometric constraints and structural maturity. Based on our simulation results we suggest that the current earthquake models (variable slip model, uniform slip model, characteristic earthquake model) are all valid -each referring to faults in different stages of their structural evolution. These findings may help to improve assessments of potential size and recurrence statistics of future earthquakes.

  5. Tracking Earthquake Cascades

    NASA Astrophysics Data System (ADS)

    Jordan, T. H.

    2011-12-01

    In assessing their risk to society, earthquakes are best characterized as cascades that can propagate from the natural environment into the socio-economic (built) environment. Strong earthquakes rarely occur as isolated events; they usually cluster in foreshock-mainshock-aftershock sequences, seismic swarms, and extended sequences of large earthquakes that propagate along major fault systems. These cascades are regulated by stress-mediated interactions among faults driven by tectonic loading. Within these cascades, each large event can itself cause a chain reaction in which the primary effects of faulting and ground shaking induce secondary effects, including tsunami, landslides, liquefaction, and set off destructive processes within the built environment, such as fires and radiation leakage from nuclear plants. Recent earthquakes have demonstrated how the socio-economic effects of large earthquakes can reverberate for many years. To reduce earthquake risk and improve the resiliency of communities to earthquake damage, society depends on five geotechnologies for tracking earthquake cascades: long-term probabilistic seismic hazard analysis (PSHA), short-term (operational) earthquake forecasting, earthquake early warning, tsunami warning, and the rapid production of post-event information for response and recovery (see figure). In this presentation, I describe how recent advances in earthquake system science are leading to improvements in this geotechnology pipeline. In particular, I will highlight the role of earthquake simulations in predicting strong ground motions and their secondary effects before and during earthquake cascades

  6. Deep earthquakes

    SciTech Connect

    Frohlich, C.

    1989-01-01

    Earthquakes are often recorded at depths as great as 650 kilometers or more. These deep events mark regions where plates of the earth's surface are consumed in the mantle. But the earthquakes themselves present a conundrum: the high pressures and temperatures at such depths should keep rock from fracturing suddenly and generating a tremor. This paper reviews the research on this problem. Almost all deep earthquakes conform to the pattern described by Wadati, namely, they generally occur at the edge of a deep ocean and define an inclined zone extending from near the surface to a depth of 600 kilometers of more, known as the Wadati-Benioff zone. Several scenarios are described that were proposed to explain the fracturing and slipping of rocks at this depth.

  7. A 2000-year record of migrating earthquakes in North China: Implications for earthquake hazards in continental interiors

    NASA Astrophysics Data System (ADS)

    Liu, Mian; Stein, Seth; Wang, Hui

    2010-05-01

    Plate tectonic theory provides a good sense of where to expect future large earthquakes on plate boundaries, and of the average time between them. However, no comparable model applies in continental interiors, where damaging earthquakes often pop up in unexpected places. This is well illustrated by the 2000-year record of earthquakes in North China, where large earthquakes are frequent and have migrated between fault systems. No large (M>7) events repeated on the same fault segment during this period. Paleoseismic records show episodic large earthquakes with long gaps in between, as have been reported in other mid-continents. We propose that the spatial migration is intrinsic to mid-continental earthquakes. Using a simple conceptual model, we show that in continental interiors slow tectonic loading is accommodated collectively by a complex system of interacting faults. Failure of one fault affects the entire system, and large earthquakes may shut off one fault and activate another. These processes are fundamentally different from those at plate boundaries where earthquakes are concentrated along the plate boundary faults, and steady-state relative plate motion loads the boundary faults rapidly at constant rates so earthquakes are quasi-periodic. The spatial migration and episodic occurrence of mid-continental earthquakes, and their long aftershock sequences that can extend for hundreds of years, explain why in continental interiors past seismicity can be poor indicators of the sites of future large earthquakes. Consequently, seismic hazard assessment based on the assumption of quasi-periodic earthquakes may fail, as illustrated by the unexpected 2008 Wenchuan earthquake that occurred on a fault that showed little seismicity in the past millennium.

  8. Upper-Plate Earthquake Swarms Remotely Triggered by the 2012 Mw-7.6 Nicoya Earthquake, Costa Rica

    NASA Astrophysics Data System (ADS)

    Linkimer, L.; Arroyo, I. G.; Montero Pohly, W. K.; Rojas, W.

    2013-05-01

    Remotely triggered seismicity that takes place at distances greater than 1-2 fault lengths appears to be a frequent phenomenon after large earthquakes, including damaging upper-plate 5.0-to-6.0 magnitude earthquakes in Costa Rica after the large (Mw > 7.0) inter-plate earthquakes in 1983, 1990, and 1991. On September 5, 2012, an inter-plate 7.6-Mw earthquake struck the Nicoya Peninsula, triggering upper-plate seismicity in the interior of Costa Rica. In this study, we analyze the largest earthquake swarms that took place during the first five months after the Nicoya earthquake. These swarms occurred at distances of 200 to 300 km from the Nicoya source region in three different tectonic settings: the Calero Island near the Costa Rica-Nicaragua border in the backarc Caribbean region, the Cartago area in the central part of Costa Rica near the active volcanic arc, and the San Vito area in the Costa Rica-Panama border region, at the southern flank of the Talamanca Cordillera, an inactive portion of the magmatic arc. The Calero swarm with 64 2.0-to-4.2 Mw earthquakes took place from September 22 to October 9, 2012. The earthquake pattern suggests a smaller-scale fault as a possible source even though this swarm is located along the inland projection of the Hess Escarpment. The Cartago swarm with 284 2.0-to-3.7 Mw earthquakes occurred from September 5 to October 5, 2012. The location and left-lateral solution of the largest event focal mechanism suggest that the Aguacaliente fault, which caused the deadliest earthquake in Costa Rican history on May 4, 1910 (Ms 6.4), is the source of some of this triggered seismicity. The San Vito earthquake swarm with 30 2.0-to-4.5 Mw earthquakes occurred between December 9, 2012 and January 28, 2013. These earthquakes occurred in the vicinity of the San Vito and Agua Buena faults, which are located along the inland projection of the Panama Fracture Zone. Documenting remotely triggered earthquakes may provide us with insight into the physics of the earthquake cycle, and may greatly improve seismic hazards assessment by illuminating active structures within the interior of Costa Rica and by pointing to where the next earthquake might be located.

  9. Earthquake Prediction and Forecasting

    NASA Astrophysics Data System (ADS)

    Jackson, David D.

    Prospects for earthquake prediction and forecasting, and even their definitions, are actively debated. Here, "forecasting" means estimating the future earthquake rate as a function of location, time, and magnitude. Forecasting becomes "prediction" when we identify special conditions that make the immediate probability much higher than usual and high enough to justify exceptional action. Proposed precursors run from aeronomy to zoology, but no identified phenomenon consistently precedes earthquakes. The reported prediction of the 1975 Haicheng, China earthquake is often proclaimed as the most successful, but the success is questionable. An earthquake predicted to occur near Parkfield, California in 19885 years has not happened. Why is prediction so hard? Earthquakes start in a tiny volume deep within an opaque medium; we do not know their boundary conditions, initial conditions, or material properties well; and earthquake precursors, if any, hide amongst unrelated anomalies. Earthquakes cluster in space and time, and following a quake earthquake probability spikes. Aftershocks illustrate this clustering, and later earthquakes may even surpass earlier ones in size. However, the main shock in a cluster usually comes first and causes the most damage. Specific models help reveal the physics and allow intelligent disaster response. Modeling stresses from past earthquakes may improve forecasts, but this approach has not yet been validated prospectively. Reliable prediction of individual quakes is not realistic in the foreseeable future, but probabilistic forecasting provides valuable information for reducing risk. Recent studies are also leading to exciting discoveries about earthquakes.

  10. 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. PMID:25756707

  11. Research on Evaluation Models and Empirical Analysis of Earthquake Disaster Losses in China

    NASA Astrophysics Data System (ADS)

    Men, Kepei; Cui, Lei

    2012-11-01

    Earthquake disasters occurred very frequently in China. As a result, to evaluate the losses has important social value and economic effect. This paper focuses on the assessment of economic losses of earthquake disasters which is divided into two parts: direct economic loss and indirect economic loss. First, the Kolmogorov-Smirnov (KS) test is used to determine the distribution of the earthquake losses per year in China, fitting the frequency of earthquake that happened per month in China. Second, the grey clustering method and principal component analysis (PCA) are applied, respectively, for direct economic loss rating and indirect economic loss rating. Finally, the economic loss generated by the earthquakes which happened from 2006 to 2009 in China is evaluated, and eight earthquakes are rated based on the comprehensive economic loss.

  12. Radiated Seismic Energy for Rapid Determinations of Large Earthquake Size, Duration, and Tsunami Earthquake Potential, and long-term Tsunami Earthquake Hazard Assessment

    NASA Astrophysics Data System (ADS)

    Convers, J. A.; Newman, A. V.

    2009-12-01

    Rapid tsunamigenic parameters from a large earthquake are paramount immediately after an event has occurred in order to adequately assess the impending tsunami danger. While location, and depth are straight-forward, other important parameters including magnitude, mechanism, rupture extent, and identification of a slow- tsunami earthquake component are non-trivial. Motivated by the massive Sumatran Earthquake of 2004, we developed algorithms to characterize the components of earthquake growth throughout the event rupture. These new and continually improved algorithms are now successful at calculating the growth in radiated energy, approximating rupture duration, and determining non-saturating energy magnitudes rapidly for large and great earthquakes. Because we utilize P-wave energy from stations as near as 25 (2500 km) from the event, we can obtain sufficient data for analysis within 10 minutes of rupture initiation for most events. Using the locally determined ratio of energy to duration we can also robustly identify slow-source tsunami earthquakes, including the 2006 Java event, that frequently trouble tsunami warning systems because of underestimated initial magnitudes. Because especially dangerous tsunami earthquakes are rare, little is known about their regional potential along individual subduction zones, and hence these events are essentially unconstrained in tsunami hazard assessments. To improve the global identification for such events we exploit the above methodology to identify smaller slow-source events globally. We explore the utility of identifying such events occurring down to 2 orders of magnitude (>Mw 5.5) smaller than previously identified tsunami-generating slow-source earthquakes in regions including Central America and Java. By including smaller events between 2000 and 2009, we describe the spatial likelihood of larger slow-source tsunami earthquakes occurring assuming a standard power-law magnitude relationship.

  13. Toxic Peptides Occur Frequently in Pergid and Argid Sawfly Larvae

    PubMed Central

    Boevé, Jean-Luc; Rozenberg, Raoul; Shinohara, Akihiko; Schmidt, Stefan

    2014-01-01

    Toxic peptides containing D-amino acids are reported from the larvae of sawfly species. The compounds are suspected to constitute environmental contaminants, as they have killed livestock grazing in areas with congregations of such larvae, and related larval extracts are deleterious to ants. Previously, two octapeptides (both called lophyrotomin) and three heptapeptides (pergidin, 4-valinepergidin and dephosphorylated pergidin) were identified from three species in the family Pergidae and one in Argidae. Here, the hypothesis of widespread occurrence of these peptides among sawflies was tested by LC-MS analyses of single larvae from eight pergid and 28 argid species, plus nine outgroup species. At least two of the five peptides were detected in most sawfly species, whereas none in any outgroup taxon. Wherever peptides were detected, they were present in each examined specimen of the respective species. Some species show high peptide concentrations, reaching up to 0.6% fresh weight of 4-valinepergidin (1.75 mg/larva) in the pergid Pterygophorus nr turneri. All analyzed pergids in the subfamily Pterygophorinae contained pergidin and 4-valinepergidin, all argids in Arginae contained pergidin and one of the two lophyrotomins, whereas none of the peptides was detected in any Perginae pergid or Sterictiphorinae argid (except in Schizocerella pilicornis, which contained pergidin). Three of the four sawfly species that were previously known to contain toxins were reanalyzed here, resulting in several, often strong, quantitative and qualitative differences in the chemical profiles. The most probable ecological role of the peptides is defense against natural enemies; the poisoning of livestock is an epiphenomenon. PMID:25121515

  14. Maximum Earthquake Magnitude Assessments by Japanese Government Committees (Invited)

    NASA Astrophysics Data System (ADS)

    Satake, K.

    2013-12-01

    The 2011 Tohoku earthquake (M 9.0) was the largest earthquake in Japanese history and such a gigantic earthquake was not foreseen around Japan. After the 2011 disaster, various government committees in Japan have discussed and assessed the maximum credible earthquake size around Japan, but their values vary without definite consensus. I will review them with earthquakes along the Nankai Trough as an example. The Central Disaster Management Council, under Cabinet Office, set up a policy for the future tsunami disaster mitigation. The possible future tsunamis are classified into two levels: L1 and L2. The L2 tsunamis are the largest possible tsunamis with low frequency of occurrence, for which saving people's lives is the first priority with soft measures such as tsunami hazard maps, evacuation facilities or disaster education. The L1 tsunamis are expected to occur more frequently, typically once in a few decades, for which hard countermeasures such as breakwater must be prepared. The assessments of L1 and L2 events are left to local governments. The CDMC also assigned M 9.1 as the maximum size of earthquake along the Nankai trough, then computed the ground shaking and tsunami inundation for several scenario earthquakes. The estimated loss is about ten times the 2011 disaster, with maximum casualties of 320,000 and economic loss of 2 trillion dollars. The Headquarters of Earthquake Research Promotion, under MEXT, was set up after the 1995 Kobe earthquake and has made long-term forecast of large earthquakes and published national seismic hazard maps. The future probability of earthquake occurrence, for example in the next 30 years, was calculated from the past data of large earthquakes, on the basis of characteristic earthquake model. The HERP recently revised the long-term forecast of Naknai trough earthquake; while the 30 year probability (60 - 70 %) is similar to the previous estimate, they noted the size can be M 8 to 9, considering the variability of past earthquakes. The Nuclear Regulation Authority, established in 2012, makes independent decisions based on the latest scientific knowledge. They assigned maximum credible earthquake magnitude of 9.6 for Nankai an Ryukyu troughs, 9.6 for Kuirl-Japan trench, and 9.2 for Izu-Bonin trench.

  15. Earthquakes and Schools

    ERIC Educational Resources Information Center

    National Clearinghouse for Educational Facilities, 2008

    2008-01-01

    Earthquakes are low-probability, high-consequence events. Though they may occur only once in the life of a school, they can have devastating, irreversible consequences. Moderate earthquakes can cause serious damage to building contents and non-structural building systems, serious injury to students and staff, and disruption of building operations.…

  16. Disaster triggers disaster: Earthquake triggering by tropical cyclones

    NASA Astrophysics Data System (ADS)

    Wdowinski, S.; Tsukanov, I.

    2011-12-01

    Three recent devastating earthquakes, the 1999 M=7.6 Chi-Chi (Taiwan), 2010 M=7.0 Leogane (Haiti), 2010 M=6.4 Kaohsiung (Taiwan), and additional three moderate size earthquakes (6occurred in tropical mountainous areas shortly after very wet tropical cyclones (hurricane or typhoon) hit the very same area. The most familiar example is Haiti, which was hit during the late summer of 2008 by two hurricanes and two tropical storms (Fay, Gustav, Hanna and Ike) within 25 days. A year an a half after this very wet hurricane season, the 2010 Leogane earthquake occurred in the mountainous Haiti's southern peninsula and caused the death of more than 300,000 people. The other cases are from Taiwan, which is characterized by a high seismicity level and frequent typhoon landfall. The three wettest typhoons in Taiwan's past 50 years were Morakot (in 2009, with 2885 mm or rain), Flossie (1969, 2162 mm) and Herb (1996, 1987 mm)[Lin et al., 2010]. Each of this three very wet storms was followed by one or two main-shock M>6 earthquake that occurred in the central mountainous area of Taiwan within three years after the typhoon. The 2009 Morakot typhoon was followed by 2009 M=6.2 Nantou and 2010 M=6.4 Kaohsiung earthquakes; the 1969 Flossie typhoon was followed by an M=6.3 earthquake in 1972; and the 1996 Herb typhoon by the 1998 M=6.2 Rueyli and 1999 M=7.6 Chi-Chi earthquakes. The earthquake catalog of Taiwan lists only two other M>6 main-shocks that occurred in Taiwan's central mountainous belt, one of them was in 1964 only four months after the wet Typhoon Gloria poured heavy rain in the same area. We suggest that the close proximity in time and space between wet tropical cyclones and earthquakes reflects a physical link between the two hazard types in which these earthquakes were triggered by rapid erosion induced by tropical cyclone's heavy rain. Based on remote sensing observations, meshfree finite element modeling, and Coulomb failure stress analysis, we show that the erosion induced by very wet cyclones increased the failure stresses at the hypocenters' depth by 300-1500 Pa, which ultimately triggered these earthquakes. Our findings are supported by a statistical analysis indicating a very low probability (1-5%) for a random earthquake occurrence process to form the observed typhoon-earthquake temporal distribution.

  17. Earthquake Facts

    MedlinePLUS

    ... most people lived in caves carved from soft rock. These dwellings collapsed during the earthquake, killing an ... Aristotle that soft ground shakes more than hard rock in an earthquake. The cause of earthquakes was ...

  18. Earthquake-related versus non-earthquake-related injuries in spinal injury patients: differentiation with multidetector computed tomography

    PubMed Central

    2010-01-01

    Introduction In recent years, several massive earthquakes have occurred across the globe. Multidetector computed tomography (MDCT) is reliable in detecting spinal injuries. The purpose of this study was to compare the features of spinal injuries resulting from the Sichuan earthquake with those of non-earthquake-related spinal trauma using MDCT. Methods Features of spinal injuries of 223 Sichuan earthquake-exposed patients and 223 non-earthquake-related spinal injury patients were retrospectively compared using MDCT. The date of non-earthquake-related spinal injury patients was collected from 1 May 2009 to 22 July 2009 to avoid the confounding effects of seasonal activity and clothing. We focused on anatomic sites, injury types and neurologic deficits related to spinal injuries. Major injuries were classified according to the grid 3-3-3 scheme of the Magerl (AO) classification system. Results A total of 185 patients (82.96%) in the earthquake-exposed cohort experienced crush injuries. In the earthquake and control groups, 65 and 92 patients, respectively, had neurologic deficits. The anatomic distribution of these two cohorts was significantly different (P < 0.001). Cervical spinal injuries were more common in the control group (risk ratio (RR) = 2.12, P < 0.001), whereas lumbar spinal injuries were more common in the earthquake-related spinal injuries group (277 of 501 injured vertebrae; 55.29%). The major types of injuries were significantly different between these cohorts (P = 0.002). Magerl AO type A lesions composed most of the lesions seen in both of these cohorts. Type B lesions were more frequently seen in earthquake-related spinal injuries (RR = 1.27), while we observed type C lesions more frequently in subjects with non-earthquake-related spinal injuries (RR = 1.98, P = 0.0029). Conclusions Spinal injuries sustained in the Sichuan earthquake were located mainly in the lumbar spine, with a peak prevalence of type A lesions and a high occurrence of neurologic deficits. The anatomic distribution and type of spinal injuries that varied between earthquake-related and non-earthquake-related spinal injury groups were perhaps due to the different mechanism of injury. PMID:21190568

  19. Earthquake activity in Oklahoma

    SciTech Connect

    Luza, K.V.; Lawson, J.E. Jr. )

    1989-08-01

    Oklahoma is one of the most seismically active areas in the southern Mid-Continent. From 1897 to 1988, over 700 earthquakes are known to have occurred in Oklahoma. The earliest documented Oklahoma earthquake took place on December 2, 1897, near Jefferson, in Grant County. The largest known Oklahoma earthquake happened near El Reno on April 9, 1952. This magnitude 5.5 (mb) earthquake was felt from Austin, Texas, to Des Moines, Iowa, and covered a felt area of approximately 362,000 km{sup 2}. Prior to 1962, all earthquakes in Oklahoma (59) were either known from historical accounts or from seismograph stations outside the state. Over half of these events were located in Canadian County. In late 1961, the first seismographs were installed in Oklahoma. From 1962 through 1976, 70 additional earthquakes were added to the earthquake database. In 1977, a statewide network of seven semipermanent and three radio-telemetry seismograph stations were installed. The additional stations have improved earthquake detection and location in the state of Oklahoma. From 1977 to 1988, over 570 additional earthquakes were located in Oklahoma, mostly of magnitudes less than 2.5. Most of these events occurred on the eastern margin of the Anadarko basin along a zone 135 km long by 40 km wide that extends from Canadian County to the southern edge of Garvin County. Another general area of earthquake activity lies along and north of the Ouachita Mountains in the Arkoma basin. A few earthquakes have occurred in the shelves that border the Arkoma and Anadarko basins.

  20. Earthquake swarms on Mount Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Kaminuma, Katsutada; Baba, Megumi; Ueki, Sadato

    1986-12-01

    Mount Erebus (3794 m), located on Ross Island in McMurdo Sound, is one of the few active volcanoes in Antartica. A high-sensitivity seismic network has been operated by Japanese and US parties on and around the Volcano since December, 1980. The results of these observations show two kinds of seismic activity on Ross Island: activity concentrated near the summit of Mount Erebus associated with Strombolian eruptions, and micro-earthquake activity spread through Mount Erebus and the surrounding area. Seismicity on Mount Erebus has been quite high, usually exceeding 20 volcanic earthquakes per day. They frequently occur in swarms with daily counts exceeding 100 events. Sixteen earthquake swarms with more than 250 events per day were recorded by the seismic network during the three year period 1982-1984, and three notable earthquake swarms out of the sixteen were recognized, in October, 1982 (named 82-C), March-April, 1984 (84-B) and July, 1984 (84-F). Swarms 84-B and 84-F have a large total number of earthquakes and large Ishimoto-Iida's "m"; hence these two swarms are presumed to constitute on one of the precursor phenomena to the new eruption, which took place on 13 September, 1984, and lasted a few months.

  1. Defeating Earthquakes

    NASA Astrophysics Data System (ADS)

    Stein, R. S.

    2012-12-01

    The 2004 M=9.2 Sumatra earthquake claimed what seemed an unfathomable 228,000 lives, although because of its size, we could at least assure ourselves that it was an extremely rare event. But in the short space of 8 years, the Sumatra quake no longer looks like an anomaly, and it is no longer even the worst disaster of the Century: 80,000 deaths in the 2005 M=7.6 Pakistan quake; 88,000 deaths in the 2008 M=7.9 Wenchuan, China quake; 316,000 deaths in the M=7.0 Haiti, quake. In each case, poor design and construction were unable to withstand the ferocity of the shaken earth. And this was compounded by inadequate rescue, medical care, and shelter. How could the toll continue to mount despite the advances in our understanding of quake risk? The world's population is flowing into megacities, and many of these migration magnets lie astride the plate boundaries. Caught between these opposing demographic and seismic forces are 50 cities of at least 3 million people threatened by large earthquakes, the targets of chance. What we know for certain is that no one will take protective measures unless they are convinced they are at risk. Furnishing that knowledge is the animating principle of the Global Earthquake Model, launched in 2009. At the very least, everyone should be able to learn what his or her risk is. At the very least, our community owes the world an estimate of that risk. So, first and foremost, GEM seeks to raise quake risk awareness. We have no illusions that maps or models raise awareness; instead, earthquakes do. But when a quake strikes, people need a credible place to go to answer the question, how vulnerable am I, and what can I do about it? The Global Earthquake Model is being built with GEM's new open source engine, OpenQuake. GEM is also assembling the global data sets without which we will never improve our understanding of where, how large, and how frequently earthquakes will strike, what impacts they will have, and how those impacts can be lessened by our actions. Using these global datasets will help to make the model as uniform as possible. The model must be built by scientists in the affected countries with GEM's support, augmented by their insights and data. The model will launch in 2014; to succeed it must be open, international, independent, and continuously tested. But the mission of GEM is not just the likelihood of ground shaking, but also gaging the economic and social consequences of earthquakes, which greatly amplify the losses. For example, should the municipality of Istanbul retrofit schools, or increase its insurance reserves and recovery capacity? Should a homeowner in a high-risk area move or strengthen her building? This is why GEM is a public-private partnership. GEM's fourteen public sponsors and eight non-governmental organization members are standing for the developing world. To extend GEM into the financial world, we draw upon the expertise of companies. GEM's ten private sponsors have endorsed the acquisition of public knowledge over private gain. In a competitive world, this is a courageous act. GEM is but one link in a chain of preparedness: from earth science and engineering research, through groups like GEM, to mitigation, retrofit or relocate decisions, building codes and insurance, and finally to prepared hospitals, schools, and homes. But it is a link that our community can make strong.

  2. Pliocene to Recent Tectonic Activity of the Reşadiye Peninsula and the Relationship Between the Recent Earthquakes Occurred in the Gulf of Gökova: Preliminary Results.

    NASA Astrophysics Data System (ADS)

    Kahraman, Burcu; Özsayın, Erman; Üner, Serkan; Dirik, Kadir

    2013-04-01

    The E-W trending Reşadiye peninsula located at the southwestern part of the Anatolian Plate is an important horst developed between Gökova and Hisarönü Grabens. NW-trending the Datça Graben is the prominent structure comprising on the Reşadiye peninsula and records the significant fingerprints of palaeogeographical and kinematical characteristics from Pliocene to recent. The Datça Graben is controlled by NW-trending the Karaköy fault in the south and E-W trending the Kızlan fault in the north. Basement rocks of the graben are composed of ophiolitic rocks of the Lycian Nappes and Jurassic marine carbonates. The basinfill initiates with Early Pliocene Kızılaǧaç formation consisting conglomerates and continues with transgressive sequence (Yıldırımlı formation) composed of conglomerates, sandstones and marls with ignimbrite intercalations. Late Pliocene age was attributed to this formation based on the gastropoda and pelecypoda fauna according to previous studies. These units are unconformably overlain by Quaternary Karaköy formation consisting red blocky conglomerates. Pyroclastics of Quaternary age (161 ka) cover the older units. Alluvium, alluvial fan deposits and terrace deposits are the youngest units of the study area. To state the tectonic evolution of the Datça Graben, bedding planes and palaeostress analysis of the fault-slip data were used. The palaeostress analyses of the Kızlan fault clearly represent N-S tensional stress regime with pure normal fault characteristics. Due to the thick colluvium and alluvial fans, any fault-slip data were collected from the Karaköy fault. Considering the same stress regime is viable for the southwestern margin of the graben, fault planes ought to have normal fault characteristics with minor strike-slip component. SW-dipping bedding planes and SW-bearing palaeocurrent measurements show that Karaköy fault occurred before the Kızlan fault and the basin was first formed as a half-graben during Early Pliocene and continued till Late Pliocene. As the Kızlan fault juxtaposes the Kızılaǧaç and Yıldırımlı formations, Late Pliocene age is attributed to the fault. Focal mechanism solutions of recent earthquakes occurred in the Gökova Bay show N-S extension which is compatible with the palaeostress analyses of the Kızlan fault. This situation represents the ongoing activity along the northern margin of the Datça Graben.

  3. Millenary Mw > 9.0 earthquakes required by geodetic strain in the Himalaya

    NASA Astrophysics Data System (ADS)

    Stevens, V. L.; Avouac, J.-P.

    2016-02-01

    The Himalayan arc produced the largest known continental earthquake, the Mw ≈ 8.7 Assam earthquake of 1950, but how frequently and where else in the Himalaya such large-magnitude earthquakes occur is not known. Paleoseismic evidence for coseismic ruptures at the front of the Himalaya with 15 to 30 m of slip suggests even larger events in medieval times, but this inference is debated. Here we estimate the frequency and magnitude of the largest earthquake in the Himalaya needed so that the moment released by seismicity balances the deficit of moment derived from measurements of geodetic strain. Assuming one third of the moment buildup is released aseismically and the earthquakes roughly follow a Gutenberg-Richter distribution, we find that Mw > 9.0 events are needed with a confidence level of at least 60% and must return approximately once per 800 years on average.

  4. WGCEP Historical California Earthquake Catalog

    USGS Publications Warehouse

    Felzer, Karen R.; Cao, Tianqing

    2008-01-01

    This appendix provides an earthquake catalog for California and the surrounding area. Our goal is to provide a listing for all known M > 5.5 earthquakes that occurred from 1850-1932 and all known M > 4.0 earthquakes that occurred from 1932-2006 within the region of 31.0 to 43.0 degrees North and -126.0 to -114.0 degrees West. Some pre-1932 earthquakes 4 5, before the Northern California network was online. Some earthquakes from 1900-1932, and particularly from 1910-1932 are also based on instrumental readings, but the quality of the instrumental record and the resulting analysis are much less precise than for later listings. A partial exception is for some of the largest earthquakes, such as the San Francisco earthquake of April 18, 1906, for which global teleseismic records (Wald et al. 1993) and geodetic measurements (Thatcher et al. 1906) have been used to help determine magnitudes.

  5. Historical earthquakes in Libya

    NASA Astrophysics Data System (ADS)

    Suleiman, A. S.

    2003-04-01

    As a result of the relative motion of the African and European plates, Libya, located at the north central margin of the African continent, has experienced a considerable intraplate tectonism particularly at its northern coastal regions. In this study I present a reevaluation of the seismicity of Libya with special focus on the historical seismicity. Data on historical seismicity is of crucial importance for seismic hazard assessment in Libya. The earliest records of earthquakes in Libya is documented back from the Roman period when two large earthquakes (262 A.D. and 365 A.D) destroyed most of the temples and public buildings of Cyrene. A number of earthquakes that affected Libya in the Middle ages includes the 704 A.D. earthquake of Sabha (southern Libya) which reportedly destroyed several towns and village. In 1183 A.D., a powerful earthquake destroyed Tripoli, killing 20,000 people. Mild tremors were felt in Tripoli in 1803, 1811 and 1903 A.D. The Hun Graben area was the site of several earthquakes through history, in April 19 -1935 a great earthquake (mb=7.1) hit this area, followed by a very large number of aftershocks including two of magnitudes 6.0 and 6.5 on the Richter scale. In 1941 a major earthquake of magnitude 5.6 hit the Hun Graben area. In 1939 an earthquake of magnitude 5.6 occurred in the Gulf of Sirt area, followed by a number of aftershocks. Reinterpretation and improvement of the source quality for selected earthquakes will be presented. The present study aims to focus on investigating the original sources of information and in developing historical earthquake database.

  6. 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 here are caused by the stress accumulation due to aseismic slip outside asperity. We consider that a spatial complementary distribution between similar earthquakes in aftershocks and asperity is a characteristic of inland earthquakes. Acknowledgements: We thank the group for the aftershock observations of the 2007 Noto Hanto Earthquake, ERI, Univ. of Tokyo, DPRI, Kyoto Univ., JMA, and NIED for providing the waveform data of aftershocks of the 2007 Noto Hanto Earthquake. We thank the group for the dense aftershock observations of the 2000 Western Tottori Earthquake for providing the waveform data of aftershocks of the 2000 Western Tottori Earthquake. We are grateful to Takashi Iwata, Haruko Sekiguchi, Haruo Horikawa and Manabu Hashimoto for providing their result.

  7. Pertussis Frequently Asked Questions

    MedlinePLUS

    ... Treatment Prevention Adults Parents-to-be Babies & Children Preteens & Teens Travelers Healthcare Personnel Frequently Asked Questions Photos ... Pregnant Women For Parents of Young Children For Preteens & Teens For Adults For Spanish Speakers Publications Related ...

  8. Upper-Plate Earthquake Swarms Remotely Triggered by the 2012 Mw-7.6 Nicoya Earthquake, Costa Rica

    NASA Astrophysics Data System (ADS)

    Linkimer, L.; Arroyo, I. G.; Montero Pohly, W. K.; Lcke, O. H.

    2013-12-01

    Remotely triggered seismicity that takes place at distances greater than 1-2 fault lengths appears to be a frequent phenomenon after large earthquakes, including damaging upper-plate 5.0-to-6.0 magnitude earthquakes in Costa Rica after the large (Mw greater than 7.0) inter-plate earthquakes in 1941, 1950, 1983, 1990, and 1991. On 5 of September 2012, an inter-plate 7.6-Mw earthquake struck the Nicoya Peninsula, triggering upper-plate seismicity in the interior of Costa Rica again. The number of upper plate-earthquakes outside the Nicoya source region that were recorded by the National Seismological Network (RSN: UCR-ICE) for the six-month period after the Nicoya event was two times higher than that number of upper plate-earthquakes during the six months before it happened. We analyze the three largest upper-plate earthquake swarms that took place during the first six months after the Nicoya event. We relocate the epicenters using a double difference algorithm with a 1D velocity model (HypoDD) and using a probabilistic method with a 3D velocity model (NonLinLoc). Additionally we compute first motion focal mechanisms for the largest events. The three swarms analyzed occurred at distances of 170 to 350 km from the Nicoya source region in three different tectonic settings: the Cartago area in the central part of Costa Rica near the active volcanic arc (approximately 170 km from the source region), the Calero Island near the Costa Rica-Nicaragua border in the backarc Caribbean region (approximately 220 km), and the San Vito area in the Costa Rica-Panama border region, at the southern flank of the Talamanca Cordillera, an inactive portion of the magmatic arc (approximately 300 km). The Cartago swarm with 95 1.8-to-4.1 Mw earthquakes occurred from September 5 to October 31, 2012. The location and left-lateral solution of the largest event suggest that the Aguacaliente fault, which caused the deadliest earthquake in Costa Rican history on May 4, 1910 (Ms 6.4), is the source of some of this triggered seismicity. Moreover, seismicity patterns suggest activity on the Navarro, Queveri, Rio Macho, and Ochomogo Faults. The Calero swarm with 70 2.5-to-4.2 Mw earthquakes took place from September 22 to October 2, 2012. The earthquake pattern suggests a possible extension of the Hess Escarpment inland. The San Vito earthquake swarm with 21 2.3-to-4.5 Mw earthquakes occurred between October 14, 2012 and January 28, 2013. These earthquakes occurred mainly in the region between the North-South oriented San Vito and Sereno-Alturas Faults, which are located along the inland projection of the Panama Fracture Zone. Documenting remotely triggered earthquakes may provide us with insights into the physics of the earthquake cycle, and may greatly improve seismic hazards assessment by illuminating active structures within the interior of Costa Rica and by pointing to where the next upper-plate earthquakes might be located.

  9. Lightning activities associated with 308 M? 5.0 earthquakes in Taiwan during 1994-2003

    NASA Astrophysics Data System (ADS)

    Liu, J. Y. G.; Chen, Y. I.; Ho, Y. Y.

    2014-12-01

    Earthquake lights and luminous phenomena are spectacular features, which have been often observed and reported. It has been known that the crust deformation activates and releases gases/charges which generate the atmospheric electric field and currents possibly resulting in luminous phenomena before and during large earthquakes. The lightning activity has been known to be one of key parameters understanding the atmospheric electric field near the Earth's surface. However, lightning activities during large earthquakes have not yet been studied and reported. It is found that lightning activities significantly increase 3-8 and 20-30 days before the 21 September 1999 Mw7.6 earthquake. A statistical analysis has been conducted to study lightning activities over the epicenter 30 days before and after 78 land and 230 sea M?5.0 earthquakes in Taiwan during 1994-2003. We find that lightning activities over the epicenter occur more frequently few days before the land earthquakes which is termed pre-earthquake lightning anomaly (PELA). For earthquakes with larger magnitudes, the PELA appears more frequent and expands a larger area from the epicenter. Our results confirm that the PELA associated with the M?6.5 land earthquakes with the depth less than 20 km and 18 cumulative days meet the significant level 0.05. These suggest that for the PELA, the Earth's surface deformation plays an important role during the earthquake preparation period. We anticipate our study to be a starting point for developing lithosphere-atmosphere coupling model of earth system sciences.

  10. Phase Transformations and Earthquakes

    NASA Astrophysics Data System (ADS)

    Green, H. W.

    2011-12-01

    Phase transformations have been cited as responsible for, or at least involved in, "deep" earthquakes for many decades (although the concept of "deep" has varied). In 1945, PW Bridgman laid out in detail the string of events/conditions that would have to be achieved for a solid/solid transformation to lead to a faulting instability, although he expressed pessimism that the full set of requirements would be simultaneously achieved in nature. Raleigh and Paterson (1965) demonstrated faulting during dehydration of serpentine under stress and suggested dehydration embrittlement as the cause of intermediate depth earthquakes. Griggs and Baker (1969) produced a thermal runaway model of a shear zone under constant stress, culminating in melting, and proposed such a runaway as the origin of deep earthquakes. The discovery of Plate Tectonics in the late 1960s established the conditions (subduction) under which Bridgman's requirements for earthquake runaway in a polymorphic transformation could be possible in nature and Green and Burnley (1989) found that instability during the transformation of metastable olivine to spinel. Recent seismic correlation of intermediate-depth-earthquake hypocenters with predicted conditions of dehydration of antigorite serpentine and discovery of metastable olivine in 4 subduction zones, suggests strongly that dehydration embrittlement and transformation-induced faulting are the underlying mechanisms of intermediate and deep earthquakes, respectively. The results of recent high-speed friction experiments and analysis of natural fault zones suggest that it is likely that similar processes occur commonly during many shallow earthquakes after initiation by frictional failure.

  11. Earthquake precursory events around epicenters and local active faults

    NASA Astrophysics Data System (ADS)

    Valizadeh Alvan, H.; Mansor, S. B.; Haydari Azad, F.

    2013-05-01

    The chain of underground events which are triggered by seismic activities and physical/chemical interactions prior to a shake in the earth's crust may produce surface and above surface phenomena. During the past decades many researchers have been carried away to seek the possibility of short term earthquake prediction using remote sensing data. Currently, there are several theories about the preparation stages of earthquakes most of which stress on raises in heat and seismic waves as the main signs of an impending earthquakes. Their differences only lie in the secondary phenomena which are triggered by these events. In any case, with the recent advances in remote sensing sensors and techniques now we are able to provide wider, more accurate monitoring of land, ocean and atmosphere. Among all theoretical factors, changes in Surface Latent Heat Flux (SLHF), Sea & Land Surface Temperature (SST & LST) and surface chlorophyll-a are easier to record from earth observing satellites. SLHF is the amount of energy exchange in the form of water vapor between the earth's surface and atmosphere. Abnormal variations in this factor have been frequently reported as an earthquake precursor during the past years. The accumulated stress in the earth's crust during the preparation phase of earthquakes is said to be the main cause of temperature anomalies weeks to days before the main event and subsequent shakes. Chemical and physical interactions in the presence of underground water lead to higher water evaporation prior to inland earthquakes. In case of oceanic earthquakes, higher temperature at the ocean beds may lead to higher amount of Chl-a on the sea surface. On the other hand, it has been also said that the leak of Radon gas which occurs as rocks break during earthquake preparation causes the formation of airborne ions and higher Air Temperature (AT). We have chosen to perform a statistical, long-term, and short-term approach by considering the reoccurrence intervals of past shakes, mapping foreshocks and aftershocks, and following changes in the above-mentioned precursors prior to past earthquake instances all over the globe. Our analyses also encompass the geographical location and extents of local and regional faults which are considered as important factors during earthquakes. The co-analysis of direct and indirect observation for precursory events is considered as a promising method for possible future successful earthquake predictions. With proper and thorough knowledge about the geological setting, atmospheric factors and geodynamics of the earthquake-prone regions we will be able to identify anomalies due to seismic activity in the earth's crust.

  12. Rapid Estimates of Rupture Extent for Large Earthquakes Using Aftershocks

    NASA Astrophysics Data System (ADS)

    Polet, J.; Thio, H. K.; Kremer, M.

    2009-12-01

    The spatial distribution of aftershocks is closely linked to the rupture extent of the mainshock that preceded them and a rapid analysis of aftershock patterns therefore has potential for use in near real-time estimates of earthquake impact. The correlation between aftershocks and slip distribution has frequently been used to estimate the fault dimensions of large historic earthquakes for which no, or insufficient, waveform data is available. With the advent of earthquake inversions that use seismic waveforms and geodetic data to constrain the slip distribution, the study of aftershocks has recently been largely focused on enhancing our understanding of the underlying mechanisms in a broader earthquake mechanics/dynamics framework. However, in a near real-time earthquake monitoring environment, in which aftershocks of large earthquakes are routinely detected and located, these data may also be effective in determining a fast estimate of the mainshock rupture area, which would aid in the rapid assessment of the impact of the earthquake. We have analyzed a considerable number of large recent earthquakes and their aftershock sequences and have developed an effective algorithm that determines the rupture extent of a mainshock from its aftershock distribution, in a fully automatic manner. The algorithm automatically removes outliers by spatial binning, and subsequently determines the best fitting strike of the rupture and its length by projecting the aftershock epicenters onto a set of lines that cross the mainshock epicenter with incremental azimuths. For strike-slip or large dip-slip events, for which the surface projection of the rupture is recti-linear, the calculated strike correlates well with the strike of the fault and the corresponding length, determined from the distribution of aftershocks projected onto the line, agrees well with the rupture length. In the case of a smaller dip-slip rupture with an aspect ratio closer to 1, the procedure gives a measure of the rupture extent and dimensions, but not necessarily the strike. We found that using standard earthquake catalogs, such as the National Earthquake Information Center catalog, we can constrain the rupture extent, rupture direction, and in many cases the type of faulting, of the mainshock with the aftershocks that occur within the first hour after the mainshock. However, this data may not be currently available in near real-time. Since our results show that these early aftershock locations may be used to estimate first order rupture parameters for large global earthquakes, the near real-time availability of these data would be useful for fast earthquake damage assessment.

  13. Retrospective Cohort Analysis of Chest Injury Characteristics and Concurrent Injuries in Patients Admitted to Hospital in the Wenchuan and Lushan Earthquakes in Sichuan, China

    PubMed Central

    Yuan, Yong; Zhao, Yong-Fan

    2014-01-01

    Background The aim of this study was to compare retrospectively the characteristics of chest injuries and frequencies of other, concurrent injuries in patients after earthquakes of different seismic intensity. Methods We compared the cause, type, and body location of chest injuries as well as the frequencies of other, concurrent injuries in patients admitted to our hospital after the Wenchuan and Lushan earthquakes in Sichuan, China. We explored possible relationships between seismic intensity and the causes and types of injuries, and we assessed the ability of the Injury Severity Score, New Injury Severity Score, and Chest Injury Index to predict respiratory failure in chest injury patients. Results The incidence of chest injuries was 9.9% in the stronger Wenchuan earthquake and 22.2% in the less intensive Lushan earthquake. The most frequent cause of chest injuries in both earthquakes was being accidentally struck. Injuries due to falls were less prevalent in the stronger Wenchuan earthquake, while injuries due to burial were more prevalent. The distribution of types of chest injury did not vary significantly between the two earthquakes, with rib fractures and pulmonary contusions the most frequent types. Spinal and head injuries concurrent with chest injuries were more prevalent in the less violent Lushan earthquake. All three trauma scoring systems showed poor ability to predict respiratory failure in patients with earthquake-related chest injuries. Conclusions Previous studies may have underestimated the incidence of chest injury in violent earthquakes. The distributions of types of chest injury did not differ between these two earthquakes of different seismic intensity. Earthquake severity and interval between rescue and treatment may influence the prevalence and types of injuries that co-occur with the chest injury. Trauma evaluation scores on their own are inadequate predictors of respiratory failure in patients with earthquake-related chest injuries. PMID:24816485

  14. The 1868 Hayward Earthquake Alliance: A Case Study - Using an Earthquake Anniversary to Promote Earthquake Preparedness

    NASA Astrophysics Data System (ADS)

    Brocher, T. M.; Garcia, S.; Aagaard, B. T.; Boatwright, J. J.; Dawson, T.; Hellweg, M.; Knudsen, K. L.; Perkins, J.; Schwartz, D. P.; Stoffer, P. W.; Zoback, M.

    2008-12-01

    Last October 21st marked the 140th anniversary of the M6.8 1868 Hayward Earthquake, the last damaging earthquake on the southern Hayward Fault. This anniversary was used to help publicize the seismic hazards associated with the fault because: (1) the past five such earthquakes on the Hayward Fault occurred about 140 years apart on average, and (2) the Hayward-Rodgers Creek Fault system is the most likely (with a 31 percent probability) fault in the Bay Area to produce a M6.7 or greater earthquake in the next 30 years. To promote earthquake awareness and preparedness, over 140 public and private agencies and companies and many individual joined the public-private nonprofit 1868 Hayward Earthquake Alliance (1868alliance.org). The Alliance sponsored many activities including a public commemoration at Mission San Jose in Fremont, which survived the 1868 earthquake. This event was followed by an earthquake drill at Bay Area schools involving more than 70,000 students. The anniversary prompted the Silver Sentinel, an earthquake response exercise based on the scenario of an earthquake on the Hayward Fault conducted by Bay Area County Offices of Emergency Services. 60 other public and private agencies also participated in this exercise. The California Seismic Safety Commission and KPIX (CBS affiliate) produced professional videos designed forschool classrooms promoting Drop, Cover, and Hold On. Starting in October 2007, the Alliance and the U.S. Geological Survey held a sequence of press conferences to announce the release of new research on the Hayward Fault as well as new loss estimates for a Hayward Fault earthquake. These included: (1) a ShakeMap for the 1868 Hayward earthquake, (2) a report by the U. S. Bureau of Labor Statistics forecasting the number of employees, employers, and wages predicted to be within areas most strongly shaken by a Hayward Fault earthquake, (3) new estimates of the losses associated with a Hayward Fault earthquake, (4) new ground motion simulations of a Hayward Fault earthquake, (5) a new USGS Fact Sheet about the earthquake and the Hayward Fault, (6) a virtual tour of the 1868 earthquake, and (7) a new online field trip guide to the Hayward Fault using locations accessible by car and public transit. Finally, the California Geological Survey and many other Alliance members sponsored the Third Conference on Earthquake Hazards in the East Bay at CSU East Bay in Hayward for the three days following the 140th anniversary. The 1868 Alliance hopes to commemorate the anniversary of the 1868 Hayward Earthquake every year to maintain and increase public awareness of this fault, the hazards it and other East Bay Faults pose, and the ongoing need for earthquake preparedness and mitigation.

  15. Living with earthquakes - development and usage of earthquake-resistant construction methods in European and Asian Antiquity

    NASA Astrophysics Data System (ADS)

    Kzmr, Mikls; Major, Balzs; Hariyadi, Agus; Pramumijoyo, Subagyo; Ditto Haryana, Yohanes

    2010-05-01

    Earthquakes are among the most horrible events of nature due to unexpected occurrence, for which no spiritual means are available for protection. The only way of preserving life and property is applying earthquake-resistant construction methods. Ancient Greek architects of public buildings applied steel clamps embedded in lead casing to hold together columns and masonry walls during frequent earthquakes in the Aegean region. Elastic steel provided strength, while plastic lead casing absorbed minor shifts of blocks without fracturing rigid stone. Romans invented concrete and built all sizes of buildings as a single, unflexible unit. Masonry surrounding and decorating concrete core of the wall did not bear load. Concrete resisted minor shaking, yielding only to forces higher than fracture limits. Roman building traditions survived the Dark Ages and 12th century Crusader castles erected in earthquake-prone Syria survive until today in reasonably good condition. Concrete and steel clamping persisted side-by-side in the Roman Empire. Concrete was used for cheap construction as compared to building of masonry. Applying lead-encased steel increased costs, and was avoided whenever possible. Columns of the various forums in Italian Pompeii mostly lack steel fittings despite situated in well-known earthquake-prone area. Whether frequent recurrence of earthquakes in the Naples region was known to inhabitants of Pompeii might be a matter of debate. Seemingly the shock of the AD 62 earthquake was not enough to apply well-known protective engineering methods throughout the reconstruction of the city before the AD 79 volcanic catastrophe. An independent engineering tradition developed on the island of Java (Indonesia). The mortar-less construction technique of 8-9th century Hindu masonry shrines around Yogyakarta would allow scattering of blocks during earthquakes. To prevent dilapidation an intricate mortise-and-tenon system was carved into adjacent faces of blocks. Only the outermost layer was treated this way, the core of the shrines was made of simple rectangular blocks. The system resisted both in-plane and out-of-plane shaking quite well, as proven by survival of many shrines for more than a millennium, and by fracturing of blocks instead of displacement during the 2006 Yogyakarta earthquake. Systematic use or disuse of known earthquake-resistant techniques in any one society depends on the perception of earthquake risk and on available financial resources. Earthquake-resistant construction practice is significantly more expensive than regular construction. Perception is influenced mostly by short individual and longer social memory. If earthquake recurrence time is longer than the preservation of social memory, if damaging quakes fade into the past, societies commit the same construction mistakes again and again. Length of the memory is possibly about a generation's lifetime. Events occurring less frequently than 25-30 years can be readily forgotten, and the risk of recurrence considered as negligible, not worth the costs of safe construction practices. (Example of recurring flash floods in Hungary.) Frequent earthquakes maintain safe construction practices, like the Java masonry technique throughout at least two centuries, and like the Fachwerk tradition on Modern Aegean Samos throughout 500 years of political and technological development. (OTKA K67583)

  16. Statistical similarity between high energy charged particle fluxes in near-earth space and earthquakes

    NASA Astrophysics Data System (ADS)

    Wang, P.; Chang, Z.; Wang, H.; Lu, H.

    2014-05-01

    It has long been noticed that rapid short-term variations of high energy charged particle fluxes in near-Earth space occur more frequently several hours before the main shock of earthquakes. Physicists wish that this observation supply a possible precursor of strong earthquakes. Based on DEMETER data, we investigate statistical behaviors of flux fluctuations for high energy charged particles in near-Earth space. Long-term clustering, scaling, and universality in the temporal occurrence are found. There is high degree statistical similarity between high energy charged particle fluxes in near-Earth space and earthquakes. Thus, the observations of the high energy particle fluxes in near-Earth space may supply a useful tool in the study of earthquakes.

  17. Education for Earthquake Disaster Prevention in the Tokyo Metropolitan Area

    NASA Astrophysics Data System (ADS)

    Oki, S.; Tsuji, H.; Koketsu, K.; Yazaki, Y.

    2008-12-01

    Japan frequently suffers from all types of disasters such as earthquakes, typhoons, floods, volcanic eruptions, and landslides. In the first half of this year, we already had three big earthquakes and heavy rainfall, which killed more than 30 people. This is not just for Japan but Asia is the most disaster-afflicted region in the world, accounting for about 90% of all those affected by disasters, and more than 50% of the total fatalities and economic losses. One of the most essential ways to reduce the damage of natural disasters is to educate the general public to let them understand what is going on during those desasters. This leads individual to make the sound decision on what to do to prevent or reduce the damage. The Ministry of Education, Culture, Sports, Science and Technology (MEXT), therefore, offered for public subscription to choose several model areas to adopt scientific education to the local elementary schools, and ERI, the Earthquake Research Institute, is qualified to develop education for earthquake disaster prevention in the Tokyo metropolitan area. The tectonic setting of this area is very complicated; there are the Pacific and Philippine Sea plates subducting beneath the North America and the Eurasia plates. The subduction of the Philippine Sea plate causes mega-thrust earthquakes such as the 1703 Genroku earthquake (M 8.0) and the 1923 Kanto earthquake (M 7.9) which had 105,000 fatalities. A magnitude 7 or greater earthquake beneath this area is recently evaluated to occur with a probability of 70 % in 30 years. This is of immediate concern for the devastating loss of life and property because the Tokyo urban region now has a population of 42 million and is the center of approximately 40 % of the nation's activities, which may cause great global economic repercussion. To better understand earthquakes in this region, "Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area" has been conducted mainly by ERI. It is a 4-year project to develop a high-density network with 400 sites at local elementary schools. We start our education project by using the real seismograms observed at their own schoolyards, putting emphasis on the reality and causality of earthquake disasters. In this presentation, we report some of the educational demonstrations and science experiments for the school kids and their parents.

  18. Frequently Asked Questions and Answers on Smallpox

    MedlinePLUS

    ... Biorisk reduction Frequently asked questions and answers on smallpox What is smallpox? Does it occur naturally? How ... protected? What is WHO doing now? What is smallpox? Smallpox is an ancient disease caused by the ...

  19. Upper-Plate Seismicity Remotely Triggered by the 2012 Mw-7.6 Nicoya Earthquake, Costa Rica

    NASA Astrophysics Data System (ADS)

    Linkimer, L.; Arroyo, I. G.; Montero Pohly, W. K.; Lcke, O. H.

    2014-12-01

    Remotely triggered seismicity that takes place at distances greater than 1-2 fault lengths appears to be a frequent phenomenon after large earthquakes, including examples in Costa Rica after the large (Mw > 7.0) inter-plate earthquakes in 1941, 1950, 1983, 1990, and 1991. On September 5, 2012, an inter-plate 7.6-Mw earthquake struck the Nicoya Peninsula, triggering upper-plate seismicity in the interior of Costa Rica. In this study, we analyze the largest earthquakes and earthquake swarms that took place during the first nine months after the Nicoya earthquake. These swarms occurred at distances of 150 to 450 km from the Nicoya source region in different tectonic settings: the Calero Island near the Costa Rica-Nicaragua border in the backarc Caribbean region, the Sixaola region near the Costa Rica-Panama border in the backarc Caribbean region, the Cartago area in the central part of Costa Rica near the active volcanic arc, and the San Vito area in the Costa Rica-Panama border region, at the southern flank of the Talamanca Cordillera in an inactive portion of the magmatic arc. The Calero swarm with 70 2.0-to-4.2 Mw earthquakes took place from September 22 to October 9, 2012. The earthquake pattern suggests a smaller-scale fault as a possible source, which is located along the inland projection of the Hess Escarpment. The Cartago swarm with 284 1.8-to-4.1 Mw earthquakes occurred from September 5 to October 31, 2012. The focal mechanism solutions suggest that strike-slip faulting predominates in this region, consistent with neotectonic observations. The San Vito earthquake swarm with 30 2.3-to-4.5 Mw earthquakes occurred between October 14, 2012 and January 28, 2013. These earthquakes occurred in the vicinity of north-south striking faults, which are located along the inland projection of the Panama Fracture Zone. The largest earthquake (5.6 Mw) occurred on the Sixaola region on 27 of May, 2013. The focal mechanism solution suggests a thrust fault that correlates with the North Panama Deformed Belt. Documenting remotely triggered earthquakes may greatly improve seismic hazards assessment by illuminating active structures within the interior of Costa Rica.

  20. Earthquake Hazards.

    ERIC Educational Resources Information Center

    Donovan, Neville

    1979-01-01

    Provides a survey and a review of earthquake activity and global tectonics from the advancement of the theory of continental drift to the present. Topics include: an identification of the major seismic regions of the earth, seismic measurement techniques, seismic design criteria for buildings, and the prediction of earthquakes. (BT)

  1. Earthquake prediction

    NASA Technical Reports Server (NTRS)

    Turcotte, Donald L.

    1991-01-01

    The state of the art in earthquake prediction is discussed. Short-term prediction based on seismic precursors, changes in the ratio of compressional velocity to shear velocity, tilt and strain precursors, electromagnetic precursors, hydrologic phenomena, chemical monitors, and animal behavior is examined. Seismic hazard assessment is addressed, and the applications of dynamical systems to earthquake prediction are discussed.

  2. Analog earthquakes

    SciTech Connect

    Hofmann, R.B.

    1995-09-01

    Analogs are used to understand complex or poorly understood phenomena for which little data may be available at the actual repository site. Earthquakes are complex phenomena, and they can have a large number of effects on the natural system, as well as on engineered structures. Instrumental data close to the source of large earthquakes are rarely obtained. The rare events for which measurements are available may be used, with modfications, as analogs for potential large earthquakes at sites where no earthquake data are available. In the following, several examples of nuclear reactor and liquified natural gas facility siting are discussed. A potential use of analog earthquakes is proposed for a high-level nuclear waste (HLW) repository.

  3. Earthquakes in Stable Continental Crust.

    ERIC Educational Resources Information Center

    Johnston, Arch C.; Kanter, Lisa R.

    1990-01-01

    Discussed are some of the reasons for earthquakes which occur in stable crust away from familiar zones at the ends of tectonic plates. Crust stability and the reactivation of old faults are described using examples from India and Australia. (CW)

  4. Earthquake precursory events around epicenters and local active faults; the cases of two inland earthquakes in Iran

    NASA Astrophysics Data System (ADS)

    Valizadeh Alvan, H.; Mansor, S.; Haydari Azad, F.

    2012-12-01

    The possibility of earthquake prediction in the frame of several days to few minutes before its occurrence has stirred interest among researchers, recently. Scientists believe that the new theories and explanations of the mechanism of this natural phenomenon are trustable and can be the basis of future prediction efforts. During the last thirty years experimental researches resulted in some pre-earthquake events which are now recognized as confirmed warning signs (precursors) of past known earthquakes. With the advances in in-situ measurement devices and data analysis capabilities and the emergence of satellite-based data collectors, monitoring the earth's surface is now a regular work. Data providers are supplying researchers from all over the world with high quality and validated imagery and non-imagery data. Surface Latent Heat Flux (SLHF) or the amount of energy exchange in the form of water vapor between the earth's surface and atmosphere has been frequently reported as an earthquake precursor during the past years. The accumulated stress in the earth's crust during the preparation phase of earthquakes is said to be the main cause of temperature anomalies weeks to days before the main event and subsequent shakes. Chemical and physical interactions in the presence of underground water lead to higher water evaporation prior to inland earthquakes. On the other hand, the leak of Radon gas occurred as rocks break during earthquake preparation causes the formation of airborne ions and higher Air Temperature (AT) prior to main event. Although co-analysis of direct and indirect observation for precursory events is considered as a promising method for future successful earthquake prediction, without proper and thorough knowledge about the geological setting, atmospheric factors and geodynamics of the earthquake-prone regions we will not be able to identify anomalies due to seismic activity in the earth's crust. Active faulting is a key factor in identification of the source and propagation of seismic waves. In many cases, active faults are capable of buildup and sudden release of tectonic stress. Hence, monitoring the active fault systems near epicentral regions of past earthquakes would be a necessity. In this paper, we try to detect possible anomalies in SLHF and AT during two moderate earthquakes of 6 - 6.5 M in Iran and explain the relationships between the seismic activities prior to these earthquake and active faulting in the area. Our analysis shows abnormal SLHF 5~10 days before these earthquakes. Meaningful anomalous concentrations usually occurred in the epicentral area. On the other hand, spatial distributions of these variations were in accordance with the local active faults. It is concluded that the anomalous increase in SLHF shows great potential in providing early warning of a disastrous earthquake, provided that there is a better understanding of the background noise due to the seasonal effects and climatic factors involved. Changes in near surface air temperature along nearby active faults, one or two weeks before the earthquakes, although not as significant as SLHF changes, can be considered as another earthquake indicator.

  5. Earthquake damage to schools

    USGS Publications Warehouse

    McCullough, Heather

    1994-01-01

    These unusual slides show earthquake damage to school and university buildings around the world. They graphically illustrate the potential danger to our schools, and to the welfare of our children, that results from major earthquakes. The slides range from Algeria, where a collapsed school roof is held up only by students' desks; to Anchorage, Alaska, where an elementary school structure has split in half; to California and other areas, where school buildings have sustained damage to walls, roofs, and chimneys. Interestingly, all the United States earthquakes depicted in this set of slides occurred either on a holiday or before or after school hours, except the 1935 tremor in Helena, Montana, which occurred at 11:35 am. It undoubtedly would have caused casualties had the schools not been closed days earlier by Helena city officials because of a damaging foreshock. Students in Algeria, the People's Republic of China, Armenia, and other stricken countries were not so fortunate. This set of slides represents 17 destructive earthquakes that occurred in 9 countries, and covers more than a century--from 1886 to 1988. Two of the tremors, both of which occurred in the United States, were magnitude 8+ on the Richter Scale, and four were magnitude 7-7.9. The events represented by the slides (see table below) claimed more than a quarter of a million lives.

  6. Road Damage from 2008 Great Sichuan Earthquake in China

    USGS Multimedia Gallery

    The May 12, 2008, Great Sichuan Earthquake, also called the Wenchuan Earthquake, occurred at 14:28 local time, in Sichuan Province, China. The earthquake magnitudes were Mw = 7.9 (USGS), Ms = 8.0 (Chinese Earthquake Administration). The epicenter was 80 km west-northwest of Chengdu, the capital city...

  7. Damage from 2008 Great Sichuan Earthquake in China

    USGS Multimedia Gallery

    The May 12, 2008, Great Sichuan Earthquake, also called the Wenchuan Earthquake, occurred at 14:28 local time, in Sichuan Province, China. The earthquake magnitudes were Mw = 7.9 (USGS), Ms = 8.0 (Chinese Earthquake Administration). The epicenter was 80 km west-northwest of Chengdu, the capital city...

  8. Boulder from 2008 Great Sichuan Earthquake in China

    USGS Multimedia Gallery

    The May 12, 2008, Great Sichuan Earthquake, also called the Wenchuan Earthquake, occurred at 14:28 local time, in Sichuan Province, China. The earthquake magnitudes were Mw = 7.9 (USGS), Ms = 8.0 (Chinese Earthquake Administration). The epicenter was 80 km west-northwest of Chengdu, the capital city...

  9. Earthquake Drill using the Earthquake Early Warning System at an Elementary School

    NASA Astrophysics Data System (ADS)

    Oki, Satoko; Yazaki, Yoshiaki; Koketsu, Kazuki

    2010-05-01

    Japan frequently suffers from many kinds of disasters such as earthquakes, typhoons, floods, volcanic eruptions, and landslides. On average, we lose about 120 people a year due to natural hazards in this decade. Above all, earthquakes are noteworthy, since it may kill thousands of people in a moment like in Kobe in 1995. People know that we may have "a big one" some day as long as we live on this land and that what to do; retrofit houses, appliance heavy furniture to walls, add latches to kitchen cabinets, and prepare emergency packs. Yet most of them do not take the action, and result in the loss of many lives. It is only the victims that learn something from the earthquake, and it has never become the lore of the nations. One of the most essential ways to reduce the damage is to educate the general public to be able to make the sound decision on what to do at the moment when an earthquake hits. This will require the knowledge of the backgrounds of the on-going phenomenon. The Ministry of Education, Culture, Sports, Science and Technology (MEXT), therefore, offered for public subscription to choose several model areas to adopt scientific education to the local elementary schools. This presentation is the report of a year and half courses that we had at the model elementary school in Tokyo Metropolitan Area. The tectonic setting of this area is very complicated; there are the Pacific and Philippine Sea plates subducting beneath the North America and the Eurasia plates. The subduction of the Philippine Sea plate causes mega-thrust earthquakes such as the 1923 Kanto earthquake (M 7.9) making 105,000 fatalities. A magnitude 7 or greater earthquake beneath this area is recently evaluated to occur with a probability of 70 % in 30 years. This is of immediate concern for the devastating loss of life and property because the Tokyo urban region now has a population of 42 million and is the center of approximately 40 % of the nation's activities, which may cause great global economic repercussion. We provide the school kids with the "World Seismicity Map" to let them realize that earthquake disasters take place unequally. Then we let the kids jump in front of the seismometer with projecting the real-time data to the wall. Grouped kids contest the largest amplitude by carefully considering how to jump high but nail the landing with their teammates. Their jumps are printed out via portable printer and compared with the real earthquake which occurred even 600km away but still huge when printed out in the same scale. Actually, a magnitude 7 earthquake recorded 600km away needs an A0 paper when scaled with a jump of 10 kids printed in an A4 paper. They've got to understand what to do not to be killed with the great big energy. We also offer earthquake drills using the Earthquake Early Warning System (EEW System). An EEW System is officially introduced in 2007 by JMA (Japan Meteorological Agency) to issue prompt alerts to provide several to several ten seconds before S-wave arrives. When hearing the alarm, school kids think fast to find a place to protect themselves. It is not always when they are in their classrooms but in the chemical lab, music room which does not have any desks to protect them, or in the PE class. Then in the science class, we demonstrate how the EEW System works. A 8m long wave propagation device made with spindles connected with springs is used to visualize the P- and S-waves. In the presentation, we would like to show the paper materials and sufficient movies.

  10. Modeling earthquake activity using a memristor-based cellular grid

    NASA Astrophysics Data System (ADS)

    Vourkas, Ioannis; Sirakoulis, Georgios Ch.

    2013-04-01

    Earthquakes are absolutely among the most devastating natural phenomena because of their immediate and long-term severe consequences. Earthquake activity modeling, especially in areas known to experience frequent large earthquakes, could lead to improvements in infrastructure development that will prevent possible loss of lives and property damage. An earthquake process is inherently a nonlinear complex system and lately scientists have become interested in finding possible analogues of earthquake dynamics. The majority of the models developed so far were based on a mass-spring model of either one or two dimensions. An early approach towards the reordering and the improvement of existing models presenting the capacitor-inductor (LC) analogue, where the LC circuit resembles a mass-spring system and simulates earthquake activity, was also published recently. Electromagnetic oscillation occurs when energy is transferred between the capacitor and the inductor. This energy transformation is similar to the mechanical oscillation that takes place in the mass-spring system. A few years ago memristor-based oscillators were used as learning circuits exposed to a train of voltage pulses that mimic environment changes. The mathematical foundation of the memristor (memory resistor), as the fourth fundamental passive element, has been expounded by Leon Chua and later extended to a more broad class of memristors, known as memristive devices and systems. This class of two-terminal passive circuit elements with memory performs both information processing and storing of computational data on the same physical platform. Importantly, the states of these devices adjust to input signals and provide analog capabilities unavailable in standard circuit elements, resulting in adaptive circuitry and providing analog parallel computation. In this work, a memristor-based cellular grid is used to model earthquake activity. An LC contour along with a memristor is used to model seismic activity based on scalar values of potentials that characterize each grid site. The simulation results prove that memristor-based circuits are an interesting non conventional approach to the modeling of complex environmental processes.

  11. Complex earthquake rupture and local tsunamis

    USGS Publications Warehouse

    Geist, E.L.

    2002-01-01

    In contrast to far-field tsunami amplitudes that are fairly well predicted by the seismic moment of subduction zone earthquakes, there exists significant variation in the scaling of local tsunami amplitude with respect to seismic moment. From a global catalog of tsunami runup observations this variability is greatest for the most frequently occuring tsunamigenic subduction zone earthquakes in the magnitude range of 7 < Mw < 8.5. Variability in local tsunami runup scaling can be ascribed to tsunami source parameters that are independent of seismic moment: variations in the water depth in the source region, the combination of higher slip and lower shear modulus at shallow depth, and rupture complexity in the form of heterogeneous slip distribution patterns. The focus of this study is on the effect that rupture complexity has on the local tsunami wave field. A wide range of slip distribution patterns are generated using a stochastic, self-affine source model that is consistent with the falloff of far-field seismic displacement spectra at high frequencies. The synthetic slip distributions generated by the stochastic source model are discretized and the vertical displacement fields from point source elastic dislocation expressions are superimposed to compute the coseismic vertical displacement field. For shallow subduction zone earthquakes it is demonstrated that self-affine irregularities of the slip distribution result in significant variations in local tsunami amplitude. The effects of rupture complexity are less pronounced for earthquakes at greater depth or along faults with steep dip angles. For a test region along the Pacific coast of central Mexico, peak nearshore tsunami amplitude is calculated for a large number (N = 100) of synthetic slip distribution patterns, all with identical seismic moment (Mw = 8.1). Analysis of the results indicates that for earthquakes of a fixed location, geometry, and seismic moment, peak nearshore tsunami amplitude can vary by a factor of 3 or more. These results indicate that there is substantially more variation in the local tsunami wave field derived from the inherent complexity subduction zone earthquakes than predicted by a simple elastic dislocation model. Probabilistic methods that take into account variability in earthquake rupture processes are likely to yield more accurate assessments of tsunami hazards.

  12. Anthropogenic triggering of large earthquakes.

    PubMed

    Mulargia, Francesco; Bizzarri, Andrea

    2014-01-01

    The physical mechanism of the anthropogenic triggering of large earthquakes on active faults is studied on the basis of experimental phenomenology, i.e., that earthquakes occur on active tectonic faults, that crustal stress values are those measured in situ and, on active faults, comply to the values of the stress drop measured for real earthquakes, that the static friction coefficients are those inferred on faults, and that the effective triggering stresses are those inferred for real earthquakes. Deriving the conditions for earthquake nucleation as a time-dependent solution of the Tresca-Von Mises criterion applied in the framework of poroelasticity yields that active faults can be triggered by fluid overpressures < 0.1?MPa. Comparing this with the deviatoric stresses at the depth of crustal hypocenters, which are of the order of 1-10?MPa, we find that injecting in the subsoil fluids at the pressures typical of oil and gas production and storage may trigger destructive earthquakes on active faults at a few tens of kilometers. Fluid pressure propagates as slow stress waves along geometric paths operating in a drained condition and can advance the natural occurrence of earthquakes by a substantial amount of time. Furthermore, it is illusory to control earthquake triggering by close monitoring of minor "foreshocks", since the induction may occur with a delay up to several years. PMID:25156190

  13. Anthropogenic Triggering of Large Earthquakes

    NASA Astrophysics Data System (ADS)

    Mulargia, Francesco; Bizzarri, Andrea

    2014-08-01

    The physical mechanism of the anthropogenic triggering of large earthquakes on active faults is studied on the basis of experimental phenomenology, i.e., that earthquakes occur on active tectonic faults, that crustal stress values are those measured in situ and, on active faults, comply to the values of the stress drop measured for real earthquakes, that the static friction coefficients are those inferred on faults, and that the effective triggering stresses are those inferred for real earthquakes. Deriving the conditions for earthquake nucleation as a time-dependent solution of the Tresca-Von Mises criterion applied in the framework of poroelasticity yields that active faults can be triggered by fluid overpressures < 0.1 MPa. Comparing this with the deviatoric stresses at the depth of crustal hypocenters, which are of the order of 1-10 MPa, we find that injecting in the subsoil fluids at the pressures typical of oil and gas production and storage may trigger destructive earthquakes on active faults at a few tens of kilometers. Fluid pressure propagates as slow stress waves along geometric paths operating in a drained condition and can advance the natural occurrence of earthquakes by a substantial amount of time. Furthermore, it is illusory to control earthquake triggering by close monitoring of minor ``foreshocks'', since the induction may occur with a delay up to several years.

  14. Anthropogenic Triggering of Large Earthquakes

    PubMed Central

    Mulargia, Francesco; Bizzarri, Andrea

    2014-01-01

    The physical mechanism of the anthropogenic triggering of large earthquakes on active faults is studied on the basis of experimental phenomenology, i.e., that earthquakes occur on active tectonic faults, that crustal stress values are those measured in situ and, on active faults, comply to the values of the stress drop measured for real earthquakes, that the static friction coefficients are those inferred on faults, and that the effective triggering stresses are those inferred for real earthquakes. Deriving the conditions for earthquake nucleation as a time-dependent solution of the Tresca-Von Mises criterion applied in the framework of poroelasticity yields that active faults can be triggered by fluid overpressures < 0.1 MPa. Comparing this with the deviatoric stresses at the depth of crustal hypocenters, which are of the order of 1–10 MPa, we find that injecting in the subsoil fluids at the pressures typical of oil and gas production and storage may trigger destructive earthquakes on active faults at a few tens of kilometers. Fluid pressure propagates as slow stress waves along geometric paths operating in a drained condition and can advance the natural occurrence of earthquakes by a substantial amount of time. Furthermore, it is illusory to control earthquake triggering by close monitoring of minor “foreshocks”, since the induction may occur with a delay up to several years. PMID:25156190

  15. Charles Darwin's earthquake reports

    NASA Astrophysics Data System (ADS)

    Galiev, Shamil

    2010-05-01

    As it is the 200th anniversary of Darwin's birth, 2009 has also been marked as 170 years since the publication of his book Journal of Researches. During the voyage Darwin landed at Valdivia and Concepcion, Chile, just before, during, and after a great earthquake, which demolished hundreds of buildings, killing and injuring many people. Land was waved, lifted, and cracked, volcanoes awoke and giant ocean waves attacked the coast. Darwin was the first geologist to observe and describe the effects of the great earthquake during and immediately after. These effects sometimes repeated during severe earthquakes; but great earthquakes, like Chile 1835, and giant earthquakes, like Chile 1960, are rare and remain completely unpredictable. This is one of the few areas of science, where experts remain largely in the dark. Darwin suggested that the effects were a result of ‘ …the rending of strata, at a point not very deep below the surface of the earth…' and ‘…when the crust yields to the tension, caused by its gradual elevation, there is a jar at the moment of rupture, and a greater movement...'. Darwin formulated big ideas about the earth evolution and its dynamics. These ideas set the tone for the tectonic plate theory to come. However, the plate tectonics does not completely explain why earthquakes occur within plates. Darwin emphasised that there are different kinds of earthquakes ‘...I confine the foregoing observations to the earthquakes on the coast of South America, or to similar ones, which seem generally to have been accompanied by elevation of the land. But, as we know that subsidence has gone on in other quarters of the world, fissures must there have been formed, and therefore earthquakes...' (we cite the Darwin's sentences following researchspace. auckland. ac. nz/handle/2292/4474). These thoughts agree with results of the last publications (see Nature 461, 870-872; 636-639 and 462, 42-43; 87-89). About 200 years ago Darwin gave oneself airs by the problems which began to discuss only during the last time. Earthquakes often precede volcanic eruptions. According to Darwin, the earthquake-induced shock may be a common mechanism of the simultaneous eruptions of the volcanoes separated by long distances. In particular, Darwin wrote that ‘… the elevation of many hundred square miles of territory near Concepcion is part of the same phenomenon, with that splashing up, if I may so call it, of volcanic matter through the orifices in the Cordillera at the moment of the shock;…'. According to Darwin the crust is a system where fractured zones, and zones of seismic and volcanic activities interact. Darwin formulated the task of considering together the processes studied now as seismology and volcanology. However the difficulties are such that the study of interactions between earthquakes and volcanoes began only recently and his works on this had relatively little impact on the development of geosciences. In this report, we discuss how the latest data on seismic and volcanic events support the Darwin's observations and ideas about the 1835 Chilean earthquake. The material from researchspace. auckland. ac. nz/handle/2292/4474 is used. We show how modern mechanical tests from impact engineering and simple experiments with weakly-cohesive materials also support his observations and ideas. On the other hand, we developed the mathematical theory of the earthquake-induced catastrophic wave phenomena. This theory allow to explain the most important aspects the Darwin's earthquake reports. This is achieved through the simplification of fundamental governing equations of considering problems to strongly-nonlinear wave equations. Solutions of these equations are constructed with the help of analytic and numerical techniques. The solutions can model different strongly-nonlinear wave phenomena which generate in a variety of physical context. A comparison with relevant experimental observations is also presented.

  16. Nisqually, Washington Intraplate Earthquake

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Hofmeister, R.

    2001-05-01

    On February 28, 2001, the M6.8 Nisqually earthquake shook the Pacific Northwest. This intraplate event occurred within the subducting Juan de Fuca plate along the Cascadia margin. Although the damage was less than observed at most large urban earthquakes, serious damage was found in Olympia, Seattle, and Tacoma. To better serve Oregon public safety needs, DOGAMI and others surveyed the Puget Sound damage to expand our technical understanding of seismic ground response, building and lifeline behavior, and secondary hazards (landslides and liquefaction). Damage was observed in structures and areas that, for the most part, would be predicted to be vulnerable. These included: old buildings (URMs), old lifelines (4th Ave bridge in Olympia), areas with poor soil conditions (Harbor Island, Seattle; Sunset Lake, Tumwater), and steep slopes (Salmon Beach; Burien). Damage types included: structural, nonstructural, contents, lifelines, landslides, liquefaction, lateral spreading, sand boils, and settlement. In several notable places, seismic-induced ground failures significantly increased the damage. Estimated costs developed from HAZUS evaluations ranged from \\2 billion to \\3.9 billion. Historic intraplate earthquakes in the Puget Sound region, including the 1949 M7.1, 1965 M6.5, and 1999 M5.9, were not accompanied by significant aftershock events or associated with earthquake sequences. However, a recent El Salvador earthquake sequence suggests there may be particular cases of increased seismicity following large intraplate events, with implications for post-earthquake response and mitigation. The January 13, 2001 M7.6 El Salvador intraplate earthquake was followed by a M6.6 crustal event February 13, 2001 and a M5.4 intraplate event February 28, 2001.

  17. Are the earthquakes of Central Virginia influenced by underground water fed by precipitation?

    NASA Astrophysics Data System (ADS)

    Muco, B.

    2012-12-01

    Even though Central Virginia is far from the nearest plate boundaries, the zone is well-known for frequent small-to-moderate shocks that have occurred since at least 18th century. People in central Virginia have felt small earthquakes and suffered damage from infrequent larger ones. The largest damaging earthquake (magnitude 5.8) in this seismic zone occurred in August 2011. Smaller earthquakes that cause little or no damage are felt each year or two. It is difficult to link the earthquakes of this zone to known small faults which are numerous, deeply buried and which don't show up at the surface. The mean earthquake depth since 1960 is 6.7 km. On the other hand, Central Virginia is a big collector and transporter of the precipitation water which run for the Atlantic Ocean through James River and its tributaries. There are about 2,000 abandoned mine lands sites in Virginia which with their underground opening can facilitate the interception and conveying of surface water. Looking for a correlation between earthquake time series for Central Virginia and monthly precipitation series for some hydrometeorological stations of the zone, we got that the best cross-correlation is obtained for a time log of three months. This time period approximately three months, has been observed also in the case of some historical earthquakes which have occurred preceded by large amount of precipitation. A good cross-correlations results also matching earthquake time series with levels of James River and Rivanna River. These results support the hydroseismicity hypothesis which suggests the role of water in the generation of intraplate seismicity

  18. The CATDAT damaging earthquakes database

    NASA Astrophysics Data System (ADS)

    Daniell, J. E.; Khazai, B.; Wenzel, F.; Vervaeck, A.

    2011-08-01

    The global CATDAT damaging earthquakes and secondary effects (tsunami, fire, landslides, liquefaction and fault rupture) database was developed to validate, remove discrepancies, and expand greatly upon existing global databases; and to better understand the trends in vulnerability, exposure, and possible future impacts of such historic earthquakes. Lack of consistency and errors in other earthquake loss databases frequently cited and used in analyses was a major shortcoming in the view of the authors which needed to be improved upon. Over 17 000 sources of information have been utilised, primarily in the last few years, to present data from over 12 200 damaging earthquakes historically, with over 7000 earthquakes since 1900 examined and validated before insertion into the database. Each validated earthquake includes seismological information, building damage, ranges of social losses to account for varying sources (deaths, injuries, homeless, and affected), and economic losses (direct, indirect, aid, and insured). Globally, a slightly increasing trend in economic damage due to earthquakes is not consistent with the greatly increasing exposure. The 1923 Great Kanto (214 billion USD damage; 2011 HNDECI-adjusted dollars) compared to the 2011 Tohoku (>300 billion USD at time of writing), 2008 Sichuan and 1995 Kobe earthquakes show the increasing concern for economic loss in urban areas as the trend should be expected to increase. Many economic and social loss values not reported in existing databases have been collected. Historical GDP (Gross Domestic Product), exchange rate, wage information, population, HDI (Human Development Index), and insurance information have been collected globally to form comparisons. This catalogue is the largest known cross-checked global historic damaging earthquake database and should have far-reaching consequences for earthquake loss estimation, socio-economic analysis, and the global reinsurance field.

  19. How Frequently Are Elementary Students Writing?

    ERIC Educational Resources Information Center

    Sunflower, Cherlyn; Crawford, Leslie W.

    A study examined elementary school writing instruction to determine (1) how frequently students are writing, (2) when in the curriculum writing occurs, and (3) in what forms the writing occurs. Data were collected in 75 elementary classrooms in 25 midwestern schools during a 15-day period. The data deviated little from what D. Graves reported in…

  20. Earthquake Analysis.

    ERIC Educational Resources Information Center

    Espinoza, Fernando

    2000-01-01

    Indicates the importance of the development of students' measurement and estimation skills. Analyzes earthquake data recorded at seismograph stations and explains how to read and modify the graphs. Presents an activity for student evaluation. (YDS)

  1. Cutaneous Leishmaniasis in Bam: A Comparative Evaluation of Pre- and Post-Earthquake Years (19992008)

    PubMed Central

    Sharifi, I; Nakhaei, N; Aflatoonian, MR; Parizi, M Hakimi; Fekri, AR; Safizadeh, H; Shirzadi, MR; Gooya, MM; Khamesipour, A; Nadim, A

    2011-01-01

    Background: The recent devastating earthquake of December 26 in Bam, 2003 created various risk factors; caused a sharp increase in incidence of anthroponotic cutaneous leishmaniasis (ACL) cases and reached to an epidemic proportion. The objective of this study was to evaluate the status of ACL cases five years before the earthquake compared to the cases occurred five years after the earthquake (19992008). Methods: Status of disease was assessed retrospectively for the five years before the earthquake and prospectively for the five years after the earthquake. Identification was confirmed by smear and polymerase chain reaction (PCR). Results: The mean annual incidence of ACL for the period from 1999 to 2003 was 1.9 per 1000 comparing to post earthquake period, which was 7.6 per 1000. Most of the infection was in individuals of <20 years, more frequently in females before the earthquake, whilst in contrast, there was a progressive rise in the number of cases, significantly in male individuals of >20 years (P< 0.0001) in post earthquake era. The anatomical distribution of lesions considerably changed during the two periods. Most of the cases were limited to three zones within the city prior to the earthquake, whereas it was spread throughout different zones after the earthquake. PCR indicated that the CL was due to Leishmania tropica in the city. Conclusion: The results strongly suggest that in natural disasters such as earthquakes various precipitating factors in favor of disease will be created, which in turn provide a suitable condition for propagation of the vector and the transmission of the parasite. PMID:23113072

  2. Testing an earthquake prediction algorithm

    USGS Publications Warehouse

    Kossobokov, V.G.; Healy, J.H.; Dewey, J.W.

    1997-01-01

    A test to evaluate earthquake prediction algorithms is being applied to a Russian algorithm known as M8. The M8 algorithm makes intermediate term predictions for earthquakes to occur in a large circle, based on integral counts of transient seismicity in the circle. In a retroactive prediction for the period January 1, 1985 to July 1, 1991 the algorithm as configured for the forward test would have predicted eight of ten strong earthquakes in the test area. A null hypothesis, based on random assignment of predictions, predicts eight earthquakes in 2.87% of the trials. The forward test began July 1, 1991 and will run through December 31, 1997. As of July 1, 1995, the algorithm had forward predicted five out of nine earthquakes in the test area, which success ratio would have been achieved in 53% of random trials with the null hypothesis.

  3. Earthquake hazards: a national threat

    USGS Publications Warehouse

    U.S. Geological Survey

    2006-01-01

    Earthquakes are one of the most costly natural hazards faced by the Nation, posing a significant risk to 75 million Americans in 39 States. The risks that earthquakes pose to society, including death, injury, and economic loss, can be greatly reduced by (1) better planning, construction, and mitigation practices before earthquakes happen, and (2) providing critical and timely information to improve response after they occur. As part of the multi-agency National Earthquake Hazards Reduction Program, the U.S. Geological Survey (USGS) has the lead Federal responsibility to provide notification of earthquakes in order to enhance public safety and to reduce losses through effective forecasts based on the best possible scientific information.

  4. Earthquake Simulator Finds Tremor Triggers

    SciTech Connect

    Johnson, Paul

    2015-03-27

    Using a novel device that simulates earthquakes in a laboratory setting, a Los Alamos researcher has found that seismic waves-the sounds radiated from earthquakes-can induce earthquake aftershocks, often long after a quake has subsided. The research provides insight into how earthquakes may be triggered and how they recur. Los Alamos researcher Paul Johnson and colleague Chris Marone at Penn State have discovered how wave energy can be stored in certain types of granular materials-like the type found along certain fault lines across the globe-and how this stored energy can suddenly be released as an earthquake when hit by relatively small seismic waves far beyond the traditional “aftershock zone” of a main quake. Perhaps most surprising, researchers have found that the release of energy can occur minutes, hours, or even days after the sound waves pass; the cause of the delay remains a tantalizing mystery.

  5. Groundwater Ion Content Precursors of Strong Earthquakes in Kamchatka (Russia)

    NASA Astrophysics Data System (ADS)

    Biagi, P. F.; Ermini, A.; Kingsley, S. P.; Khatkevich, Y. M.; Gordeev, E. I.

    The Kamchatka peninsula, located in the far east of Russia, is a geologically active margin where the Pacific plate subducts beneath the North American and Eurasia plates. This area is characterised by frequent and strong seismic activity (magnitudes reaching 8.6) and epicentres are generally distributed offshore along the eastern coast of the peninsula. For many years, hydrogeochemicals have been sampled with a mean interval of three days to measure the most common ions in the groundwater of five deep wells in the southern area of the Kamchatka peninsula. In the last decade, five earthquakes with M > 6.5 have occurred at distances less than 250 km from these wells. These earthquakes were powerful enough for them to be considered as potential originators of precursors. In order to reveal possible precursors of these earthquakes, we analysed the groundwater ion contents. The quasi-periodic annual variation was filtered out, together with other slow trends, and then we smoothed out the high frequency fluctuations that arise from errors in a single measurement. When examining the data, we labelled each signal with an amplitude greater than three times the standard deviation as an irregularity and we made a first attempt at defining an anomaly as an irregularity occurring simultaneously in more than one parameter at each well. In a second definition we used the existence of an irregularity occurring simultaneously in each ion at more than one well. Then, on the basis of past results worldwide and the time interval between the earthquakes observed, we chose 158 days as the maximum temporal window between a possible anomaly and the subsequent earthquake. With the first anomaly definition we identified 6 anomalies with 4 possible successes and 2 failures. For the five earthquakes considered capable of producing precursors we obtained precursors in three cases. With the second anomaly definition we identified 10 anomalies with 7 possible successes and 3 failures and we obtained precursors in four of the five earthquakes. A schematic model explaining aspects of the complex relationship linking earthquakes and ion content anomalies is also presented.

  6. California earthquake history

    USGS Publications Warehouse

    Toppozada, T.; Branum, D.

    2004-01-01

    This paper presents an overview of the advancement in our knowledge of California's earthquake history since ??? 1800, and especially during the last 30 years. We first review the basic statewide research on earthquake occurrences that was published from 1928 through 2002, to show how the current catalogs and their levels of completeness have evolved with time. Then we review some of the significant new results in specific regions of California, and some of what remains to be done. Since 1850, 167 potentially damaging earthquakes of M ??? 6 or larger have been identified in California and its border regions, indicating an average rate of 1.1 such events per year. Table I lists the earthquakes of M ??? 6 to 6.5 that were also destructive since 1812 in California and its border regions, indicating an average rate of one such event every ??? 5 years. Many of these occurred before 1932 when epicenters and magnitudes started to be determined routinely using seismographs in California. The number of these early earthquakes is probably incomplete in sparsely populated remote parts of California before ??? 1870. For example, 6 of the 7 pre-1873 events in table I are of M ??? 7, suggesting that other earthquakes of M 6.5 to 6.9 occurred but were not properly identified, or were not destructive. The epicenters and magnitudes (M) of the pre-instrumental earthquakes were determined from isoseismal maps that were based on the Modified Mercalli Intensity of shaking (MMI) at the communities that reported feeling the earthquakes. The epicenters were estimated to be in the regions of most intense shaking, and values of M were estimated from the extent of the areas shaken at various MMI levels. MMI VII or greater shaking is the threshold of damage to weak buildings. Certain areas in the regions of Los Angeles, San Francisco, and Eureka were each shaken repeatedly at MMI VII or greater at least six times since ??? 1812, as depicted by Toppozada and Branum (2002, fig. 19).

  7. Predicted Surface Displacements for Scenario Earthquakes in the San Francisco Bay Region

    USGS Publications Warehouse

    Murray-Moraleda, Jessica R.

    2008-01-01

    In the immediate aftermath of a major earthquake, the U.S. Geological Survey (USGS) will be called upon to provide information on the characteristics of the event to emergency responders and the media. One such piece of information is the expected surface displacement due to the earthquake. In conducting probabilistic hazard analyses for the San Francisco Bay Region, the Working Group on California Earthquake Probabilities (WGCEP) identified a series of scenario earthquakes involving the major faults of the region, and these were used in their 2003 report (hereafter referred to as WG03) and the recently released 2008 Uniform California Earthquake Rupture Forecast (UCERF). Here I present a collection of maps depicting the expected surface displacement resulting from those scenario earthquakes. The USGS has conducted frequent Global Positioning System (GPS) surveys throughout northern California for nearly two decades, generating a solid baseline of interseismic measurements. Following an earthquake, temporary GPS deployments at these sites will be important to augment the spatial coverage provided by continuous GPS sites for recording postseismic deformation, as will the acquisition of Interferometric Synthetic Aperture Radar (InSAR) scenes. The information provided in this report allows one to anticipate, for a given event, where the largest displacements are likely to occur. This information is valuable both for assessing the need for further spatial densification of GPS coverage before an event and prioritizing sites to resurvey and InSAR data to acquire in the immediate aftermath of the earthquake. In addition, these maps are envisioned to be a resource for scientists in communicating with emergency responders and members of the press, particularly during the time immediately after a major earthquake before displacements recorded by continuous GPS stations are available.

  8. Effects of acoustic waves on stick-slip in granular media and implications for earthquakes.

    PubMed

    Johnson, Paul A; Savage, Heather; Knuth, Matt; Gomberg, Joan; Marone, Chris

    2008-01-01

    It remains unknown how the small strains induced by seismic waves can trigger earthquakes at large distances, in some cases thousands of kilometres from the triggering earthquake, with failure often occurring long after the waves have passed. Earthquake nucleation is usually observed to take place at depths of 10-20 km, and so static overburden should be large enough to inhibit triggering by seismic-wave stress perturbations. To understand the physics of dynamic triggering better, as well as the influence of dynamic stressing on earthquake recurrence, we have conducted laboratory studies of stick-slip in granular media with and without applied acoustic vibration. Glass beads were used to simulate granular fault zone material, sheared under constant normal stress, and subject to transient or continuous perturbation by acoustic waves. Here we show that small-magnitude failure events, corresponding to triggered aftershocks, occur when applied sound-wave amplitudes exceed several microstrain. These events are frequently delayed or occur as part of a cascade of small events. Vibrations also cause large slip events to be disrupted in time relative to those without wave perturbation. The effects are observed for many large-event cycles after vibrations cease, indicating a strain memory in the granular material. Dynamic stressing of tectonic faults may play a similar role in determining the complexity of earthquake recurrence. PMID:18172496

  9. Effects of acoustic waves on stick-slip in granular media and implications for earthquakes

    USGS Publications Warehouse

    Johnson, P.A.; Savage, H.; Knuth, M.; Gomberg, J.; Marone, C.

    2008-01-01

    It remains unknown how the small strains induced by seismic waves can trigger earthquakes at large distances, in some cases thousands of kilometres from the triggering earthquake, with failure often occurring long after the waves have passed. Earthquake nucleation is usually observed to take place at depths of 10-20 km, and so static overburden should be large enough to inhibit triggering by seismic-wave stress perturbations. To understand the physics of dynamic triggering better, as well as the influence of dynamic stressing on earthquake recurrence, we have conducted laboratory studies of stick-slip in granular media with and without applied acoustic vibration. Glass beads were used to simulate granular fault zone material, sheared under constant normal stress, and subject to transient or continuous perturbation by acoustic waves. Here we show that small-magnitude failure events, corresponding to triggered aftershocks, occur when applied sound-wave amplitudes exceed several microstrain. These events are frequently delayed or occur as part of a cascade of small events. Vibrations also cause large slip events to be disrupted in time relative to those without wave perturbation. The effects are observed for many large-event cycles after vibrations cease, indicating a strain memory in the granular material. Dynamic stressing of tectonic faults may play a similar role in determining the complexity of earthquake recurrence. ??2007 Nature Publishing Group.

  10. The threat of silent earthquakes

    USGS Publications Warehouse

    Cervelli, Peter

    2004-01-01

    Not all earthquakes shake the ground. The so-called silent types are forcing scientists to rethink their understanding of the way quake-prone faults behave. In rare instances, silent earthquakes that occur along the flakes of seaside volcanoes may cascade into monstrous landslides that crash into the sea and trigger towering tsunamis. Silent earthquakes that take place within fault zones created by one tectonic plate diving under another may increase the chance of ground-shaking shocks. In other locations, however, silent slip may decrease the likelihood of destructive quakes, because they release stress along faults that might otherwise seem ready to snap.

  11. Major Existence of Very Low Frequency Earthquakes in Background Seismicity Along Subduction Zone of South-western Japan

    NASA Astrophysics Data System (ADS)

    Ishihara, Y.

    2003-12-01

    The condense, high quality and equalized broadband seismic network provided us to recognize the variety of seismic sources. The active volcanoes excite seismic waves with various frequency characteristics. Some cases show the long period seismic waves greater than 10 sec associates with volcanic activities. The tectonic seismic events originated at the close to trench zone are frequently lack of high frequency, greater than 1 Hz, seismic wave component. Meanwhile, the many low frequency earthquakes and tremors whose sources are not explicated are occurred in lower crust and subcrustal region. The subduction zone of Philippine Sea plate in south-western Japan is actively genetic area of low frequency earthquake group. The broadband seismic array of Japan region observed unknown long period ground motions. The seismograms are higher amplitude between 10 and 30 sec period than ground noise level. The earthquake JMA and USGS catalogues don_ft list about these long period seismograms. The arrival order of wave packet means that these events locate subduction zone around Japan. The hypocenters of unknown events are estimated by arrival times of vertical peak amplitude using the assumption that the ground motion dominates Rayleigh wave. The more detailed determination of major events is performed by combined technique for moment tensor inversion and grid search. The moment magnitude of uncatalogued event is greater than 3.5 because of the detection limitation. The largest event is distributed to about 4.5 Mw level and special event is greater than 5.0. The frequency characteristics show that source time is 7 to 20 sec by comparison with synthetic seismograms. We call these uncatalogued events _gvery low frequency earthquake_h. The hypocenters are located to two kinds of zones along the Philippine Sea subducting plate in south-western Japan. The one zone is very close to the trough. The seismicity listed by earthquake catalogues is low level in the zone and hypocenters are distributed in island arc side. The very low frequency earthquakes occur in outer area of seismic generation zone. The other zone is coincided with extended zone generating low frequency seismic events. Very low frequency earthquake occurs intermittently in limited area. Frequently, activity increases for some days and swarm type activity generates occasionally. To evaluate integrated seismicity for anomalous events, same class magnitude, greater than 3.0, events occurred in same and surrounding area are picked up from JMA earthquake catalogue. The analysis shows that seismicity of very low frequency earthquakes is comparative with one of normal earthquakes in background activity. We concluded that very low frequency earthquake is one of factors playing seismically important role.

  12. Frequent Itemset Hiding Algorithm Using Frequent Pattern Tree Approach

    ERIC Educational Resources Information Center

    Alnatsheh, Rami

    2012-01-01

    A problem that has been the focus of much recent research in privacy preserving data-mining is the frequent itemset hiding (FIH) problem. Identifying itemsets that appear together frequently in customer transactions is a common task in association rule mining. Organizations that share data with business partners may consider some of the frequent

  13. Large historical earthquakes and tsunamis in a very active tectonic rift: the Gulf of Corinth, Greece

    NASA Astrophysics Data System (ADS)

    Triantafyllou, Ioanna; Papadopoulos, Gerassimos

    2014-05-01

    The Gulf of Corinth is an active tectonic rift controlled by E-W trending normal faults with an uplifted footwall in the south and a subsiding hangingwall with antithetic faulting in the north. Regional geodetic extension rates up to about 1.5 cm/yr have been measured, which is one of the highest for tectonic rifts in the entire Earth, while seismic slip rates up to about 1 cm/yr were estimated. Large earthquakes with magnitudes, M, up to about 7 were historically documented and instrumentally recorded. In this paper we have compiled historical documentation of earthquake and tsunami events occurring in the Corinth Gulf from the antiquity up to the present. The completeness of the events reported improves with time particularly after the 15th century. The majority of tsunamis were caused by earthquake activity although the aseismic landsliding is a relatively frequent agent for tsunami generation in Corinth Gulf. We focus to better understand the process of tsunami generation from earthquakes. To this aim we have considered the elliptical rupture zones of all the strong (M≥ 6.0) historical and instrumental earthquakes known in the Corinth Gulf. We have taken into account rupture zones determined by previous authors. However, magnitudes, M, of historical earthquakes were recalculated from a set of empirical relationships between M and seismic intensity established for earthquakes occurring in Greece during the instrumental era of seismicity. For this application the macroseismic field of each one of the earthquakes was identified and seismic intensities were assigned. Another set of empirical relationships M/L and M/W for instrumentally recorded earthquakes in the Mediterranean region was applied to calculate rupture zone dimensions; where L=rupture zone length, W=rupture zone width. The rupture zones positions were decided on the basis of the localities of the highest seismic intensities and co-seismic ground failures, if any, while the orientation of the maximum axis of the ellipse was determined by following the local fault trends. The tsunami size was calculated in terms of tsunami intensity in the 12-point scale of Papadopoulos-Imamura. We investigated empirical correlations between (i) the tsunami intensity and earthquake magnitude, (ii) the frequency of earthquakes and the frequency of tsunamis, as well as (iii) between the maximum tsunami inundation and the position of the earthquake rupture zone. We discuss our results as for their importance for the development of a tsunami decision matrix in the particular area of Corinth Gulf, an issue which is of interest from the point of view of tsunami early warning.

  14. What caused a large number of fatalities in the Tohoku earthquake?

    NASA Astrophysics Data System (ADS)

    Ando, M.; Ishida, M.; Nishikawa, Y.; Mizuki, C.; Hayashi, Y.

    2012-04-01

    The Mw9.0 earthquake caused 20,000 deaths and missing persons in northeastern Japan. 115 years prior to this event, there were three historical tsunamis that struck the region, one of which is a "tsunami earthquake" resulted with a death toll of 22,000. Since then, numerous breakwaters were constructed along the entire northeastern coasts and tsunami evacuation drills were carried out and hazard maps were distributed to local residents on numerous communities. However, despite the constructions and preparedness efforts, the March 11 Tohoku earthquake caused numerous fatalities. The strong shaking lasted three minutes or longer, thus all residents recognized that this is the strongest and longest earthquake that they had been ever experienced in their lives. The tsunami inundated an enormous area at about 560km2 over 35 cities along the coast of northeast Japan. To find out the reasons behind the high number of fatalities due to the March 11 tsunami, we interviewed 150 tsunami survivors at public evacuation shelters in 7 cities mainly in Iwate prefecture in mid-April and early June 2011. Interviews were done for about 30min or longer focused on their evacuation behaviors and those that they had observed. On the basis of the interviews, we found that residents' decisions not to evacuate immediately were partly due to or influenced by earthquake science results. Below are some of the factors that affected residents' decisions. 1. Earthquake hazard assessments turned out to be incorrect. Expected earthquake magnitudes and resultant hazards in northeastern Japan assessed and publicized by the government were significantly smaller than the actual Tohoku earthquake. 2. Many residents did not receive accurate tsunami warnings. The first tsunami warning were too small compared with the actual tsunami heights. 3. The previous frequent warnings with overestimated tsunami height influenced the behavior of the residents. 4. Many local residents above 55 years old experienced the 1960 Chile tsunami, which was significantly smaller than that of the 11 March tsunami. This sense of "knowing" put their lives at high risk. 5. Some local residents believed that with the presence of a breakwater, only slight flooding would occur. 6. Many people did not understand why tsunami is created under the sea. Therefore, relation of earthquake and tsunami is not quite linked to many people. These interviews made it clear that many deaths resulted because current technology and earthquake science underestimated tsunami heights, warning systems failed, and breakwaters were not strong or high enough. However, even if these problems occur in future earthquakes, better knowledge regarding earthquakes and tsunami hazards could save more lives. In an elementary school when children have fresh brain, it is necessary for them to learn the basic mechanism of tsunami generation.

  15. Deep Tremor as a Focus of Earthquake Forecasting Research

    NASA Astrophysics Data System (ADS)

    Beroza, G. C.

    2007-12-01

    The discovery of deep tremor has opened a new window into fault-zone processes and offers new possibilities for earthquake forecasting research. Locales where deep tremor has been extensively documented to date include the Nankai Trough, Cascadia, and Central California, which are all areas with considerable seismic potential. Deep tremor is observed to accompany slow slip, such that the combined phenomena have come to be known as episodic tremor and slip (ETS). The emerging view is that deep tremor is the seismic signature of slow slip that occurs episodically on the down-dip extension of seismogenic faults. The amount of slip in these slow slip episodes is approximately equal to the amount of slip that would have been accumulated during the time since the last ETS episode. This suggests that the tremor source may outline the down-dip edge of the locked, seismogenic zone, with the down-dip transition zone locked between ETS episodes, and relaxed during them. Thus, on faults on which tremor occurs, it should be possible to map precisely the down-dip extent of the locked zone, which is often a major source of uncertainty in assessing earthquake potential. Tremor may also prove useful for time-dependent earthquake forecasting. Due to it's strategic location, and episodic nature, deep episodic transients will accelerate stress accumulation on adjacent, shallower, locked portions of faults, which should in turn increase the likelihood of a large earthquake. Thus, tremor is a potentially important forecasting tool, though it might lead to only modest probability gains. With frequent tremor episodes, and infrequent large earthquakes, it will be difficult to test this hypothesis. A more fruitful approach may be to monitor the variation of micro-earthquake activity with respect to deep tremor, and perhaps to examine historical seismic data retrospectively for seismic tremor near the time of large earthquakes. The potential promise of this newly discovered phenomenon argues for enhanced monitoring in areas where tremor is known to occur, and in places where it is likely to occur, based on our understanding of the factors that control tremor occurrence.

  16. Hazard Assessment and Early Warning of Tsunamis: Lessons from the 2011 Tohoku earthquake

    NASA Astrophysics Data System (ADS)

    Satake, K.

    2012-12-01

    The March 11, 2011 Tohoku earthquake (M 9.0) was the largest earthquake in Japanese history, and was the best recorded subduction-zone earthquakes in the world. In particular, various offshore geophysical observations revealed large horizontal and vertical seafloor movements, and the tsunami was recorded on high-quality, high-sampling gauges. Analysis of such tsunami waveforms shows a temporal and spatial slip distribution during the 2011 Tohoku earthquake. The fault rupture started near the hypocenter and propagated into both deep and shallow parts of the plate interface. Very large, ~25 m, slip off Miyagi on the deep part of plate interface corresponds to an interplate earthquake of M 8.8, the location and size similar to 869 Jogan earthquake model, and was responsible for the large tsunami inundation in Sendai and Ishinomaki plains. Huge slip, more than 50 m, occurred on the shallow part near the trench axis ~3 min after the earthquake origin time. This delayed shallow rupture (M 8.8) was similar to the 1896 "tsunami earthquake," and was responsible for the large tsunami on the northern Sanriku coast, measured at ~100 km north of the largest slip. Thus the Tohoku earthquake can be decomposed into an interplate earthquake and the triggered "tsunami earthquake." The Japan Meteorological Agency issued tsunami warning 3 minutes after the earthquake, and saved many lives. However, their initial estimation of tsunami height was underestimated, because the earthquake magnitude was initially estimated as M 7.9, hence the computed tsunami heights were lower. The JMA attempts to improve the tsunami warning system, including technical developments to estimate the earthquake size in a few minutes by using various and redundant information, to deploy and utilize the offshore tsunami observations, and to issue a warning based on the worst case scenario if a possibility of giant earthquake exists. Predicting a trigger of another large earthquake would still be a challenge. Tsunami hazard assessments or long-term forecast of earthquakes have not considered such a triggering or simultaneous occurrence of different types of earthquakes. The large tsunami at the Fukushima nuclear power station was due to the combination of the deep and shallow slip. Disaster prevention for low-frequency but large-scale hazard must be considered. The Japanese government established a general policy to for two levels: L1 and L2. The L2 tsunamis are the largest possible tsunamis with low frequency of occurrence, but cause devastating disaster once they occur. For such events, saving people's lives is the first priority and soft measures such as tsunami hazard maps, evacuation facilities or disaster education will be prepared. The L1 tsunamis are expected to occur more frequently, typically once in a few decades, for which hard countermeasures such as breakwater must be prepared to protect lives and properties of residents as well as economic and industrial activities.

  17. The parkfield, california, earthquake prediction experiment.

    PubMed

    Bakun, W H; Lindh, A G

    1985-08-16

    Five moderate (magnitude 6) earthquakes with similar features have occurred on the Parkfield section of the San Andreas fault in central California since 1857. The next moderate Parkfield earthquake is expected to occur before 1993. The Parkfield prediction experiment is designed to monitor the details of the final stages of the earthquake preparation process; observations and reports of seismicity and aseismic slip associated with the last moderate Parkfield earthquake in 1966 constitute much of the basis of the design of the experiment. PMID:17739363

  18. ERTS-1, earthquakes, and tectonic evolution in Alaska

    NASA Technical Reports Server (NTRS)

    Gedney, L.; Vanwormer, J.

    1974-01-01

    In comparing seismicity patterns in Alaska with ERTS-1 imagery, it is striking to see the frequency with which earthquake epicenters fall on, or near, lineaments visible on the imagery. Often these lineaments prove to be tectonics faults which have been mapped in the field. But equally as often, existing geologic and tectonic maps show no evidence of these features. The remoteness and inaccessibility of most of Alaska is responsible, in large part, for the inadequacy of the mapping. ERTS-1 imagery is filling a vital need in providing much of the missing information, and is pointing out many areas of potential earthquake hazard. Earthquakes in central and south-central Alaska result when the northeastern corner of the north Pacific lithospheric plate underthrusts the continent. North of Mt. McKinley, the seismicity is continental in nature and of shallow origin, with earthquakes occurring on lineaments, and frequently at intersections of lineaments. The shallower events tend to align themselves with lineaments visible on the imagery.

  19. What Can Sounds Tell Us About Earthquake Interactions?

    NASA Astrophysics Data System (ADS)

    Aiken, C.; Peng, Z.

    2012-12-01

    It is important not only for seismologists but also for educators to effectively convey information about earthquakes and the influences earthquakes can have on each other. Recent studies using auditory display [e.g. Kilb et al., 2012; Peng et al. 2012] have depicted catastrophic earthquakes and the effects large earthquakes can have on other parts of the world. Auditory display of earthquakes, which combines static images with time-compressed sound of recorded seismic data, is a new approach to disseminating information to a general audience about earthquakes and earthquake interactions. Earthquake interactions are influential to understanding the underlying physics of earthquakes and other seismic phenomena such as tremors in addition to their source characteristics (e.g. frequency contents, amplitudes). Earthquake interactions can include, for example, a large, shallow earthquake followed by increased seismicity around the mainshock rupture (i.e. aftershocks) or even a large earthquake triggering earthquakes or tremors several hundreds to thousands of kilometers away [Hill and Prejean, 2007; Peng and Gomberg, 2010]. We use standard tools like MATLAB, QuickTime Pro, and Python to produce animations that illustrate earthquake interactions. Our efforts are focused on producing animations that depict cross-section (side) views of tremors triggered along the San Andreas Fault by distant earthquakes, as well as map (bird's eye) views of mainshock-aftershock sequences such as the 2011/08/23 Mw5.8 Virginia earthquake sequence. These examples of earthquake interactions include sonifying earthquake and tremor catalogs as musical notes (e.g. piano keys) as well as audifying seismic data using time-compression. Our overall goal is to use auditory display to invigorate a general interest in earthquake seismology that leads to the understanding of how earthquakes occur, how earthquakes influence one another as well as tremors, and what the musical properties of these interactions can tell us about the source characteristics of earthquakes and tremors.

  20. The Skovorodino, 2011, earthquake

    NASA Astrophysics Data System (ADS)

    Bykova, V. V.; Tatevossian, R. E.; Nikolaev, L. D.; Mikhin, A. G.; Mokrushina, N. G.

    2015-01-01

    On October 14, 2011, an earthquake with the magnitude Mw = 6.0 occurred 15 km northwest of the town of Skovorodino in East Siberia. This earthquake aroused interest among geophysicists. In this paper, we present some results on the prior seismicity in the region, which are based on the macroseismic and instrumental data. The assessment of the seismic regime immediately before the main shock and the analysis of the aftershock sequence rely on the data provided by the field network of the Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences. The network was in operation from the end of July 2011 to January 2012. The analysis of the entire dataset suggests that the Skovorodino earthquake was outstanding in a vast region: only seismic events with low magnitudes (at most 4) occurred in the epicentral zone of this earthquake and its nearest neighborhood. The positions of the source of the main shock and the hypocenters of the after-shocks (more than 1300 events) are determined. The aftershock sequence is anomalousit lacks sufficiently strong seismic events ( M ? 3.5). The spatiotemporal distribution of the aftershocks shows two clusters of the epicenters to the west and east of the epicentral zone. These clusters drastically differ in their parameters, indicating that the source has a complex structure. Generally, the source can be understood as a shear displacement on the subvertical fault plane trending approximately along the latitude. The size of the source is 17 17 km; the average slip is 63 cm, which is at least 30% larger than the characteristic values for the earthquakes with M = 6.0.

  1. Frequently Asked Questions about Immunizations

    MedlinePLUS

    ... All About Food Allergies Frequently Asked Questions About Immunizations KidsHealth > For Parents > Frequently Asked Questions About Immunizations ... for answers to some common questions. What do immunizations do? Vaccines work by preparing the body to ...

  2. Revised seismic history of the El Pilar fault, Northeastern Venezuela, from the Cariaco 1997 earthquake and recent preliminary paleoseismic results

    NASA Astrophysics Data System (ADS)

    Audemard, Franck A.

    2007-07-01

    In light of the July 9, 1997, Cariaco earthquake, it is clearly understood now that damage in the city of Cuman located in northeastern Venezuela and frequently destroyed by the largest earthquakes since the first recorded event in 1530 is strongly enhanced by poor soil conditions that, in turn, are responsible for site amplification and widespread earthquake-induced effects. Therefore, most previous macroseismic studies of historical earthquakes must be revaluated because those localized high-intensity values at Cuman surely led to the misestimation of past epicenters. Preliminary paleoseismic results, gathered at three exploratory trenches dug across the surface break of the Cariaco 1997 earthquake in 1998, allow us to associate the 1684 earthquake with this recently ruptured fault segment that extends between the towns of San Antonio del Golfo and Ro Casanay (roughly between the two gulfs of Cariaco and Paria, state of Sucre). Other major results from the reassessment of the seismic history of this fault are: (a) the 1766 event seems to have generated in a different source to the El Pilar fault because the size of the felt area suggests that it is an intermediate-depth earthquake; (b) damage to Cuman produced by the 1797 event suggests that this was a local earthquake, perhaps equivalent to the 1929 earthquake, which ruptured for some 30 km just east of Cuman into the Gulf of Cariaco; and (c) seismogenic association of the 1530 and 1853 earthquakes still remains unclear but it is very likely that these ruptures occurred offshore, as suggested by the rather large tsunami waves that both events have generated, placing their hypocenters west of Cuman in the Cariaco Trough. This reassessment also sheds light into the El Pilar fault segmentation and the behavior of its seismogenic barriers through time.

  3. Earthquake and tsunami forecasts: Relation of slow slip events to subsequent earthquake rupture

    PubMed Central

    Dixon, Timothy H.; Jiang, Yan; Malservisi, Rocco; McCaffrey, Robert; Voss, Nicholas; Protti, Marino; Gonzalez, Victor

    2014-01-01

    The 5 September 2012 Mw 7.6 earthquake on the Costa Rica subduction plate boundary followed a 62-y interseismic period. High-precision GPS recorded numerous slow slip events (SSEs) in the decade leading up to the earthquake, both up-dip and down-dip of seismic rupture. Deeper SSEs were larger than shallower ones and, if characteristic of the interseismic period, release most locking down-dip of the earthquake, limiting down-dip rupture and earthquake magnitude. Shallower SSEs were smaller, accounting for some but not all interseismic locking. One SSE occurred several months before the earthquake, but changes in Mohr–Coulomb failure stress were probably too small to trigger the earthquake. Because many SSEs have occurred without subsequent rupture, their individual predictive value is limited, but taken together they released a significant amount of accumulated interseismic strain before the earthquake, effectively defining the area of subsequent seismic rupture (rupture did not occur where slow slip was common). Because earthquake magnitude depends on rupture area, this has important implications for earthquake hazard assessment. Specifically, if this behavior is representative of future earthquake cycles and other subduction zones, it implies that monitoring SSEs, including shallow up-dip events that lie offshore, could lead to accurate forecasts of earthquake magnitude and tsunami potential. PMID:25404327

  4. Results of the Regional Earthquake Likelihood Models (RELM) test of earthquake forecasts in California

    PubMed Central

    Lee, Ya-Ting; Turcotte, Donald L.; Holliday, James R.; Sachs, Michael K.; Rundle, John B.; Chen, Chien-Chih; Tiampo, Kristy F.

    2011-01-01

    The Regional Earthquake Likelihood Models (RELM) test of earthquake forecasts in California was the first competitive evaluation of forecasts of future earthquake occurrence. Participants submitted expected probabilities of occurrence of M?4.95 earthquakes in 0.1נ0.1 cells for the period 1 January 1, 2006, to December 31, 2010. Probabilities were submitted for 7,682 cells in California and adjacent regions. During this period, 31 M?4.95 earthquakes occurred in the test region. These earthquakes occurred in 22 test cells. This seismic activity was dominated by earthquakes associated with the M=7.2, April 4, 2010, El MayorCucapah earthquake in northern Mexico. This earthquake occurred in the test region, and 16 of the other 30 earthquakes in the test region could be associated with it. Nine complete forecasts were submitted by six participants. In this paper, we present the forecasts in a way that allows the reader to evaluate which forecast is the most successful in terms of the locations of future earthquakes. We conclude that the RELM test was a success and suggest ways in which the results can be used to improve future forecasts. PMID:21949355

  5. Results of the Regional Earthquake Likelihood Models (RELM) test of earthquake forecasts in California.

    PubMed

    Lee, Ya-Ting; Turcotte, Donald L; Holliday, James R; Sachs, Michael K; Rundle, John B; Chen, Chien-Chih; Tiampo, Kristy F

    2011-10-01

    The Regional Earthquake Likelihood Models (RELM) test of earthquake forecasts in California was the first competitive evaluation of forecasts of future earthquake occurrence. Participants submitted expected probabilities of occurrence of M ? 4.95 earthquakes in 0.1 0.1 cells for the period 1 January 1, 2006, to December 31, 2010. Probabilities were submitted for 7,682 cells in California and adjacent regions. During this period, 31 M ? 4.95 earthquakes occurred in the test region. These earthquakes occurred in 22 test cells. This seismic activity was dominated by earthquakes associated with the M = 7.2, April 4, 2010, El Mayor-Cucapah earthquake in northern Mexico. This earthquake occurred in the test region, and 16 of the other 30 earthquakes in the test region could be associated with it. Nine complete forecasts were submitted by six participants. In this paper, we present the forecasts in a way that allows the reader to evaluate which forecast is the most "successful" in terms of the locations of future earthquakes. We conclude that the RELM test was a success and suggest ways in which the results can be used to improve future forecasts. PMID:21949355

  6. Earthquake and tsunami forecasts: relation of slow slip events to subsequent earthquake rupture.

    PubMed

    Dixon, Timothy H; Jiang, Yan; Malservisi, Rocco; McCaffrey, Robert; Voss, Nicholas; Protti, Marino; Gonzalez, Victor

    2014-12-01

    The 5 September 2012 M(w) 7.6 earthquake on the Costa Rica subduction plate boundary followed a 62-y interseismic period. High-precision GPS recorded numerous slow slip events (SSEs) in the decade leading up to the earthquake, both up-dip and down-dip of seismic rupture. Deeper SSEs were larger than shallower ones and, if characteristic of the interseismic period, release most locking down-dip of the earthquake, limiting down-dip rupture and earthquake magnitude. Shallower SSEs were smaller, accounting for some but not all interseismic locking. One SSE occurred several months before the earthquake, but changes in Mohr-Coulomb failure stress were probably too small to trigger the earthquake. Because many SSEs have occurred without subsequent rupture, their individual predictive value is limited, but taken together they released a significant amount of accumulated interseismic strain before the earthquake, effectively defining the area of subsequent seismic rupture (rupture did not occur where slow slip was common). Because earthquake magnitude depends on rupture area, this has important implications for earthquake hazard assessment. Specifically, if this behavior is representative of future earthquake cycles and other subduction zones, it implies that monitoring SSEs, including shallow up-dip events that lie offshore, could lead to accurate forecasts of earthquake magnitude and tsunami potential. PMID:25404327

  7. Localization of intermediate-term earthquake prediction

    SciTech Connect

    Kossobokov, V.G.; Keilis-Borok, V.I. ); Smith, S.W. )

    1990-11-10

    Relative seismic quiescence within a region which has already been diagnosed as having entered a Time of Increased Probability (TIP) for the occurrence of a strong earthquake can be used to refine the locality in which the earthquake may be expected to occur. A simple algorithm with parameters fitted from the data in Northern California preceding the 1980 magnitude 7.0 earthquake offshore from Eureka depicts relative quiescence within the region of a TIP. The procedure was tested, without readaptation of parameter, on 17 other strong earthquake occurrences in North America, Japan, and Eurasia, most of which were in regions for which a TIP had been previously diagnosed. The localizing algorithm successfully outlined a region within which the subsequent earthquake occurred for 16 of these 17 strong earthquakes. The area of prediction in each case was reduced significantly, ranging between 7% and 25% of the total area covered by the TIP.

  8. Earthquakes and plate tectonics.

    USGS Publications Warehouse

    Spall, H.

    1982-01-01

    Earthquakes occur at the following three kinds of plate boundary: ocean ridges where the plates are pulled apart, margins where the plates scrape past one another, and margins where one plate is thrust under the other. Thus, we can predict the general regions on the earth's surface where we can expect large earthquakes in the future. We know that each year about 140 earthquakes of magnitude 6 or greater will occur within this area which is 10% of the earth's surface. But on a worldwide basis we cannot say with much accuracy when these events will occur. The reason is that the processes in plate tectonics have been going on for millions of years. Averaged over this interval, plate motions amount to several mm per year. But at any instant in geologic time, for example the year 1982, we do not know, exactly where we are in the worldwide cycle of strain build-up and strain release. Only by monitoring the stress and strain in small areas, for instance, the San Andreas fault, in great detail can we hope to predict when renewed activity in that part of the plate tectonics arena is likely to take place. -from Author

  9. Earthquake Testing

    NASA Technical Reports Server (NTRS)

    1979-01-01

    During NASA's Apollo program, it was necessary to subject the mammoth Saturn V launch vehicle to extremely forceful vibrations to assure the moonbooster's structural integrity in flight. Marshall Space Flight Center assigned vibration testing to a contractor, the Scientific Services and Systems Group of Wyle Laboratories, Norco, California. Wyle-3S, as the group is known, built a large facility at Huntsville, Alabama, and equipped it with an enormously forceful shock and vibration system to simulate the liftoff stresses the Saturn V would encounter. Saturn V is no longer in service, but Wyle-3S has found spinoff utility for its vibration facility. It is now being used to simulate earthquake effects on various kinds of equipment, principally equipment intended for use in nuclear power generation. Government regulations require that such equipment demonstrate its ability to survive earthquake conditions. In upper left photo, Wyle3S is preparing to conduct an earthquake test on a 25ton diesel generator built by Atlas Polar Company, Ltd., Toronto, Canada, for emergency use in a Canadian nuclear power plant. Being readied for test in the lower left photo is a large circuit breaker to be used by Duke Power Company, Charlotte, North Carolina. Electro-hydraulic and electro-dynamic shakers in and around the pit simulate earthquake forces.

  10. Predecessors of the giant 1960 Chile earthquake.

    PubMed

    Cisternas, Marco; Atwater, Brian F; Torrejón, Fernando; Sawai, Yuki; Machuca, Gonzalo; Lagos, Marcelo; Eipert, Annaliese; Youlton, Cristián; Salgado, Ignacio; Kamataki, Takanobu; Shishikura, Masanobu; Rajendran, C P; Malik, Javed K; Rizal, Yan; Husni, Muhammad

    2005-09-15

    It is commonly thought that the longer the time since last earthquake, the larger the next earthquake's slip will be. But this logical predictor of earthquake size, unsuccessful for large earthquakes on a strike-slip fault, fails also with the giant 1960 Chile earthquake of magnitude 9.5 (ref. 3). Although the time since the preceding earthquake spanned 123 years (refs 4, 5), the estimated slip in 1960, which occurred on a fault between the Nazca and South American tectonic plates, equalled 250-350 years' worth of the plate motion. Thus the average interval between such giant earthquakes on this fault should span several centuries. Here we present evidence that such long intervals were indeed typical of the last two millennia. We use buried soils and sand layers as records of tectonic subsidence and tsunami inundation at an estuary midway along the 1960 rupture. In these records, the 1960 earthquake ended a recurrence interval that had begun almost four centuries before, with an earthquake documented by Spanish conquistadors in 1575. Two later earthquakes, in 1737 and 1837, produced little if any subsidence or tsunami at the estuary and they therefore probably left the fault partly loaded with accumulated plate motion that the 1960 earthquake then expended. PMID:16163355

  11. Predecessors of the giant 1960 Chile earthquake

    USGS Publications Warehouse

    Cisternas, M.; Atwater, B.F.; Torrejon, F.; Sawai, Y.; Machuca, G.; Lagos, M.; Eipert, A.; Youlton, C.; Salgado, I.; Kamataki, T.; Shishikura, M.; Rajendran, C.P.; Malik, J.K.; Rizal, Y.; Husni, M.

    2005-01-01

    It is commonly thought that the longer the time since last earthquake, the larger the next earthquake's slip will be. But this logical predictor of earthquake size, unsuccessful for large earthquakes on a strike-slip fault, fails also with the giant 1960 Chile earthquake of magnitude 9.5 (ref. 3). Although the time since the preceding earthquake spanned 123 years (refs 4, 5), the estimated slip in 1960, which occurred on a fault between the Nazca and South American tectonic plates, equalled 250-350 years' worth of the plate motion. Thus the average interval between such giant earthquakes on this fault should span several centuries. Here we present evidence that such long intervals were indeed typical of the last two millennia. We use buried soils and sand layers as records of tectonic subsidence and tsunami inundation at an estuary midway along the 1960 rupture. In these records, the 1960 earthquake ended a recurrence interval that had begun almost four centuries before, with an earthquake documented by Spanish conquistadors in 1575. Two later earthquakes, in 1737 and 1837, produced little if any subsidence or tsunami at the estuary and they therefore probably left the fault partly loaded with accumulated plate motion that the 1960 earthquake then expended. ?? 2005 Nature Publishing Group.

  12. The physics of an earthquake

    NASA Astrophysics Data System (ADS)

    McCloskey, John

    2008-03-01

    The Sumatra-Andaman earthquake of 26 December 2004 (Boxing Day 2004) and its tsunami will endure in our memories as one of the worst natural disasters of our time. For geophysicists, the scale of the devastation and the likelihood of another equally destructive earthquake set out a series of challenges of how we might use science not only to understand the earthquake and its aftermath but also to help in planning for future earthquakes in the region. In this article a brief account of these efforts is presented. Earthquake prediction is probably impossible, but earth scientists are now able to identify particularly dangerous places for future events by developing an understanding of the physics of stress interaction. Having identified such a dangerous area, a series of numerical Monte Carlo simulations is described which allow us to get an idea of what the most likely consequences of a future earthquake are by modelling the tsunami generated by lots of possible, individually unpredictable, future events. As this article was being written, another earthquake occurred in the region, which had many expected characteristics but was enigmatic in other ways. This has spawned a series of further theories which will contribute to our understanding of this extremely complex problem.

  13. Two Different Earthquake Source Faults Caused Great Kanto Earthquake Disaster of 1923

    NASA Astrophysics Data System (ADS)

    Ishikawa, M.

    2005-12-01

    The Kanto earthquake of 1 September 1923 in Japan is one of the most destructive earthquakes in the world, and over 100,000 people were sacrificed in the disaster. The source of the 1923 Kanto earthquake is a megathrust between Philippine Sea plate and Honshu plate. In this research, the geometry of the Philippine Sea slab at Izu collision zone was identified using GIS analysis for earthquake catalogue of the Japan Meteorological Agency, and a new hypothesis for the seismogenesis of the Kanto earthquake in Greater Tokyo Area is proposed. The GIS analysis for hypocenter database indicates the existence of an N-S trending slab tear beneath the Tanzawa Mountain. The Philippine Sea slab beneath western half of the Tanzawa Mountain is much deeper than the slab depth beneath eastern half of the Tanzawa Mountain. In the 1923 Kanto earthquake, some M7 class aftershocks occurred immediately after the M7.9 main shock. The M7.3 earthquake of 1 September in eastern region of Yamanashi Prefecture has been considered to be one of biggest aftershocks of the 1923 Kanto earthquake (Takemura, 2003). Although the M7.9 earthquake at 11:58 (Tokyo local time) and the M7.3 earthquake at 12:03 occurred near to each other within five minutes, the two earthquakes were generated on two different earthquake source faults in the slab tear model that I proposed to explain hypocenter distribution. The M7.9 earthquake occurred on the megathrust fault beneath eastern half of Tanzawa Mountain to Tokyo-Yokohama metropolitan region, and the M7.3 earthquake occurred on another earthquake source fault beneath western half of the Tanzawa Mountain. Therefore, the M7.3 earthquake should be considered to be another main shock. The 1923 Kanto earthquake generated slope failures extensively in western region of Greater Tokyo Area e.g. Hakone volcano and Tanzawa Mountain. The GIS-based spatial analysis for slope failures in Kanagawa Prefecture shows that slope failures took place at about 20,000 locations, and the total area reached about 58.5 square kilometer. This disaster resulted in about 800 victims, which is the maximum as slope failure disaster in Japan in the last100 years. Takemura (2003) indicates that this disaster was triggered by the ground motion of the M7.3 earthquake. Because two main shocks attacked within five minutes in the Greater Tokyo Area and results in the Great Kanto Earthquake Disaster, seismic hazard in the Greater Tokyo Area should be evaluated by consideration of the two different earthquake source faults.

  14. Earthquake tectonics

    SciTech Connect

    Steward, R.F. )

    1991-02-01

    Earthquakes release a tremendous amount of energy into the subsurface in the form of seismic waves. The seismic wave energy of the San Francisco 1906 (M = 8.2) earthquake was equivalent to over 8 billion tons of TNT (3.3 {times} 10{sup 19} joules). Four basic wave types are propagated form seismic sources, two non-rotational and two rotational. As opposed to the non-rotational R and SH waves, the rotational compressional (RC) and rotational shear (RS) waves carry the bulk of the energy from a seismic source. RC wavefronts propagate in the subsurface and refract similarly to P waves, but are considerably slower. RC waves are critically refracted beneath the air surface interface at velocities less than the velocity of sound in air because they refract at the velocity of sound in air minus the retrograde particle velocity at the top of the wave. They propagate at tsunami waves in the open ocean, and produce loud sounds on land that are heard by humans and animals during earthquakes. The energy of the RS wave dwarfs that of the P, SH, and even the RC wave. The RS wave is the same as what is currently called the S wave in earthquake seismology, and produces both folding and strike-slip faulting at considerable distances from the epicenter. RC and RS waves, propagated during earthquakes from the Santa Ynez fault and a right-slip fault on trend with the Red Mountain fault, produced the Santa Ynez Mountains in California beginning in the middle Pliocene and continuing until the present.

  15. Earthquakes: Recurrence and Interoccurrence Times

    NASA Astrophysics Data System (ADS)

    Abaimov, S. G.; Turcotte, D. L.; Shcherbakov, R.; Rundle, J. B.

    2006-12-01

    There is accumulating evidence that the Weibull (stretched exponential) distribution has universal applicability to complex self-organizing phenomena. In this paper we discuss the statistical distributions of recurrence and interoccurrence times of earthquakes. Interoccurrence times are the time intervals between successive earthquakes in a specified region with magnitudes greater than a specified value. We argue that these earthquakes occur randomly although they may have a time dependent driver such as Omori's law. Recurrence times are the time intervals between successive earthquakes at a specified location on a specified fault. We argue that the statistical distribution of recurrence times is Weibull. The reason for this is that the Weibull distribution is the only distribution that has a scale invariant hazard function. The hazard function h(t_0) is the probability that an earthquake will occur at a time t0 after the last earthquake. For a Weibull distribution h(t)~ t_0^{?-1} we consider two sets of characteristic earthquakes on the San Andreas fault: 1) the Parkfield earthquakes and 2) the sequence of earthquakes identified by paleoseismic studies at the Wrightwood site. In each case we make comparison with the applicable Weibull distribution. The numbers of earthquakes in each of these sequences are too small to make definitive conclusions. To overcome this difficulty we consider a sequence of earthquakes obtained from a one million year "Virtual California" simulation of San Andreas earthquakes. Very good agreement with a Weibull distribution is found. We also simulate this behavior using a slider-block model. The behavior of this model is sensitive to the stiffness ? of the system, ?=k_c/k_L, where k_c is the spring constant of the connector springs and k_L is the spring constant of loader springs. For a soft system (small ? ) there are no system wide events and the interoccurrence time statistics of large events is Poissonian. For a stiff system (large ? ) system wide events dominate the energy dissipation and the statistics of the recurrence times between the system wide events satisfy the Weibull distribution to a good approximation.

  16. The Road to Total Earthquake Safety

    NASA Astrophysics Data System (ADS)

    Frohlich, Cliff

    Cinna Lomnitz is possibly the most distinguished earthquake seismologist in all of Central and South America. Among many other credentials, Lomnitz has personally experienced the shaking and devastation that accompanied no fewer than five major earthquakesChile, 1939; Kern County, California, 1952; Chile, 1960; Caracas,Venezuela, 1967; and Mexico City, 1985. Thus he clearly has much to teach someone like myself, who has never even actually felt a real earthquake.What is this slim book? The Road to Total Earthquake Safety summarizes Lomnitz's May 1999 presentation at the Seventh Mallet-Milne Lecture, sponsored by the Society for Earthquake and Civil Engineering Dynamics. His arguments are motivated by the damage that occurred in three earthquakesMexico City, 1985; Loma Prieta, California, 1989; and Kobe, Japan, 1995. All three quakes occurred in regions where earthquakes are common. Yet in all three some of the worst damage occurred in structures located a significant distance from the epicenter and engineered specifically to resist earthquakes. Some of the damage also indicated that the structures failed because they had experienced considerable rotational or twisting motion. Clearly, Lomnitz argues, there must be fundamental flaws in the usually accepted models explaining how earthquakes generate strong motions, and how we should design resistant structures.

  17. Utilizing Changes in Repeating Earthquakes to Monitor Evolving Processes and Structure Before and During Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Hotovec-Ellis, Alicia

    Repeating earthquakes are two or more earthquakes that share the same source location and source mechanism, which results in the earthquakes having highly similar waveforms when recorded at a seismic instrument. Repeating earthquakes have been observed in a wide variety of environments: from fault systems (such as the San Andreas and Cascadia subduction zone), to hydrothermal areas and volcanoes. Volcano seismologists are particularly concerned with repeating earthquakes, as they have been observed at volcanoes along the entire range of eruptive style and are often a prominent feature of eruption seismicity. The behavior of repeating earthquakes sometimes changes with time, which possibly reflects subtle changes in the mechanism creating the earthquakes. In Chapter 1, we document an example of repeating earthquakes during the 2009 eruption of Redoubt volcano that became increasingly frequent with time, until they blended into harmonic tremor prior to several explosions. We interpreted the source of the earthquakes as stick-slip on a fault near the conduit that slipped increasingly often as the explosion neared in response to the build-up of pressure in the system. The waveforms of repeating earthquakes may also change, even if the behavior does not. We can quantify changes in waveform using the technique of coda wave interferometry to differentiate between changes in source and medium. In Chapters 2 and 3, we document subtle changes in the coda of repeating earthquakes related to small changes in the near-surface velocity structure at Mount St. Helens before and during its eruption in 2004. Velocity changes have been observed prior to several volcanic eruptions, are thought to occur in response to volumetric strain and the opening or closing of cracks in the subsurface. We compared continuous records of velocity change against other geophysical data, and found that velocities at Mount St. Helens change in response to snow loading, fluid saturation, shaking from large distant earthquakes, shallow pressurization, and possibly lava extrusion. Velocity changes at Mount St. Helens are a complex mix of many different effects, and other complementary data are required to interpret the signal.

  18. Advances in Earthquake Prediction Research and the June 2000 Earthquakes in Iceland

    NASA Astrophysics Data System (ADS)

    Stefansson, R.

    2006-12-01

    In June 2000, two earthquakes with magnitude 6.6 (Ms) occurred in the central part of the South Iceland seismic zone (SISZ). Earthquakes in this region have, according to historical information, in some cases caused collapse of the majority of houses in areas encompassing 1,000 square kilometers in this relatively densely populated farming region. Because large earthquakes were expected to occur soon, much attention was given to preparedness in the region and for the last two decades it has been the subject of multi- national, mainly European, co-operation in earthquake prediction research and in the development of a high- level micro-earthquake system: the SIL system. Despite intensive surface fissuring caused by the earthquakes and measured accelerations reaching 0.8 g, the earthquakes in 2000 caused no serious injuries and no structural collapse. The relatively minor destruction led to more optimism regarding the safety of living in the area. But it also lead to some optimism about the significance of earthquake prediction research. Both earthquakes had a long-term prediction and the second of the two earthquakes had a short- term warning about place, size and immediacy. In this presentation, I will describe the warnings that were given ahead of the earthquakes. Also, I will reconsider these warnings in light of new results from multi-national earthquake prediction research in Iceland. This modeling work explains several observable patterns caused by crustal process ahead of large earthquakes. Micro-seismic observations and modeling show that, in conditions prevailing in the Icelandic crust, fluids can be carried upward from the brittle-ductile boundary in response to strain, bringing high, near- lithostatic pore pressures into the brittle crust, preparing a region for the release of a large earthquake; monitoring this process will enable long- and short- term earthquakes warnings.

  19. Frequent Itemset Hiding Algorithm Using Frequent Pattern Tree Approach

    ERIC Educational Resources Information Center

    Alnatsheh, Rami

    2012-01-01

    A problem that has been the focus of much recent research in privacy preserving data-mining is the frequent itemset hiding (FIH) problem. Identifying itemsets that appear together frequently in customer transactions is a common task in association rule mining. Organizations that share data with business partners may consider some of the frequent…

  20. Focal mechanisms of earthquakes in Mongolia

    NASA Astrophysics Data System (ADS)

    Sodnomsambuu, D.; Natalia, R.; Gangaadorj, B.; Munkhuu, U.; Davaasuren, G.; Danzansan, E.; Yan, R.; Valentina, M.; Battsetseg, B.

    2011-12-01

    Focal mechanism data provide information on the relative magnitudes of the principal stresses, so that a tectonic regime can be assigned. Especially such information is useful for the study of intraplate seismic active regions. A study of earthquake focal mechanisms in the territory of Mongolia as landlocked and intraplate region was conducted. We present map of focal mechanisms of earthquakes with M4.5 which occurred in Mongolia and neighboring regions. Focal mechanisms solutions were constrained by the first motion solutions, as well as by waveform modeling, particularly CMT solutions. Four earthquakes have been recorded in Mongolia in XX century with magnitude more than 8, the 1905 M7.9 Tsetserleg and M8.4 Bolnai earthquakes, the 1931 M8.0 Fu Yun earthquake, the 1957 M8.1 Gobi-Altai earthquake. However the map of focal mechanisms of earthquakes in Mongolia allows seeing all seismic active structures: Gobi Altay, Mongolian Altay, active fringe of Hangay dome, Hentii range etc. Earthquakes in the most of Mongolian territory and neighboring China regions are characterized by strike-slip and reverse movements. Strike-slip movements also are typical for earthquakes in Altay Range in Russia. The north of Mongolia and south part of the Baikal area is a region where have been occurred earthquakes with different focal mechanisms. This region is a zone of the transition between compressive regime associated to India-Eurasian collision and extensive structures localized in north of the country as Huvsgul area and Baykal rift. Earthquakes in the Baikal basin itself are characterized by normal movements. Earthquakes in Trans-Baikal zone and NW of Mongolia are characterized dominantly by strike-slip movements. Analysis of stress-axis orientations, the tectonic stress tensor is presented. The map of focal mechanisms of earthquakes in Mongolia could be useful tool for researchers in their study on Geodynamics of Central Asia, particularly of Mongolian and Baikal regions.

  1. Long Period Earthquakes Beneath California's Young and Restless Volcanoes

    NASA Astrophysics Data System (ADS)

    Pitt, A. M.; Dawson, P. B.; Shelly, D. R.; Hill, D. P.; Mangan, M.

    2013-12-01

    The newly established USGS California Volcano Observatory has the broad responsibility of monitoring and assessing hazards at California's potentially threatening volcanoes, most notably Mount Shasta, Medicine Lake, Clear Lake Volcanic Field, and Lassen Volcanic Center in northern California; and Long Valley Caldera, Mammoth Mountain, and Mono-Inyo Craters in east-central California. Volcanic eruptions occur in California about as frequently as the largest San Andreas Fault Zone earthquakes-more than ten eruptions have occurred in the last 1,000 years, most recently at Lassen Peak (1666 C.E. and 1914-1917 C.E.) and Mono-Inyo Craters (c. 1700 C.E.). The Long Valley region (Long Valley caldera and Mammoth Mountain) underwent several episodes of heightened unrest over the last three decades, including intense swarms of volcano-tectonic (VT) earthquakes, rapid caldera uplift, and hazardous CO2 emissions. Both Medicine Lake and Lassen are subsiding at appreciable rates, and along with Clear Lake, Long Valley Caldera, and Mammoth Mountain, sporadically experience long period (LP) earthquakes related to migration of magmatic or hydrothermal fluids. Worldwide, the last two decades have shown the importance of tracking LP earthquakes beneath young volcanic systems, as they often provide indication of impending unrest or eruption. Herein we document the occurrence of LP earthquakes at several of California's young volcanoes, updating a previous study published in Pitt et al., 2002, SRL. All events were detected and located using data from stations within the Northern California Seismic Network (NCSN). Event detection was spatially and temporally uneven across the NCSN in the 1980s and 1990s, but additional stations, adoption of the Earthworm processing system, and heightened vigilance by seismologists have improved the catalog over the last decade. LP earthquakes are now relatively well-recorded under Lassen (~150 events since 2000), Clear Lake (~60 events), Mammoth Mountain (~320 events), and Long Valley Caldera (~40 events). LP earthquakes are notably absent under Mount Shasta. With the exception of Long Valley Caldera where LP earthquakes occur at depths of ?5 km, hypocenters are generally between 15-25 km. The rates of LP occurrence over the last decade have been relatively steady within the study areas, except at Mammoth Mountain, where years of gradually declining LP activity abruptly increased after a swarm of unusually deep (20 km) VT earthquakes in October 2012. Epicenter locations relative to the sites of most recent volcanism vary across volcanic centers, but most LP earthquakes fall within 10 km of young vents. Source models for LP earthquakes often involve the resonance of fluid-filled cracks or nonlinear flow of fluids along irregular cracks (reviewed in Chouet and Matoza, 2013, JVGR). At mid-crustal depths the relevant fluids are likely to be low-viscosity basaltic melt and/or exsolved CO2-rich volatiles (Lassen, Clear Lake, Mammoth Mountain). In the shallow crust, however, hydrothermal waters/gases are likely involved in the generation of LP seismicity (Long Valley Caldera).

  2. Darwin's earthquake.

    PubMed

    Lee, Richard V

    2010-07-01

    Charles Darwin experienced a major earthquake in the Concepcin-Valdivia region of Chile 175 years ago, in February 1835. His observations dramatically illustrated the geologic principles of James Hutton and Charles Lyell which maintained that the surface of the earth was subject to alterations by natural events, such as earthquakes, volcanoes, and the erosive action of wind and water, operating over very long periods of time. Changes in the land created new environments and fostered adaptations in life forms that could lead to the formation of new species. Without the demonstration of the accumulation of multiple crustal events over time in Chile, the biologic implications of the specific species of birds and tortoises found in the Galapagos Islands and the formulation of the concept of natural selection might have remained dormant. PMID:21038753

  3. Earthquakes triggered by fluid extraction

    NASA Astrophysics Data System (ADS)

    Segall, P.

    1989-10-01

    Seismicity is correlated in space and time with production from some oil and gas fields where pore pressures have declined by several tens of megapascals. Reverse faulting has occurred both above and below petroleum reservoirs, and normal faulting has occurred on the flanks of at least one reservoir. The theory of poroelasticity requires that fluid extraction locally alter the state of stress. Calculations with simple geometries predict stress perturbations that are consistent with observed earthquake locations and focal mechanisms. Measurements of surface displacement and strain, pore pressure, stress, and poroelastic rock properties in such areas could be used to test theoretical predictions and improve our understanding of earthquake mechanics.

  4. Earthquakes triggered by fluid extraction

    USGS Publications Warehouse

    Segall, P.

    1989-01-01

    Seismicity is correlated in space and time with production from some oil and gas fields where pore pressures have declined by several tens of megapascals. Reverse faulting has occurred both above and below petroleum reservoirs, and normal faulting has occurred on the flanks of at least one reservoir. The theory of poroelasticity requires that fluid extraction locally alter the state of stress. Calculations with simple geometries predict stress perturbations that are consistent with observed earthquake locations and focal mechanisms. Measurements of surface displacement and strain, pore pressure, stress, and poroelastic rock properties in such areas could be used to test theoretical predictions and improve our understanding of earthquake mechanics. -Author

  5. Pain after earthquake

    PubMed Central

    2012-01-01

    Introduction On 6 April 2009, at 03:32 local time, an Mw 6.3 earthquake hit the Abruzzi region of central Italy causing widespread damage in the City of L Aquila and its nearby villages. The earthquake caused 308 casualties and over 1,500 injuries, displaced more than 25,000 people and induced significant damage to more than 10,000 buildings in the L'Aquila region. Objectives This observational retrospective study evaluated the prevalence and drug treatment of pain in the five weeks following the L'Aquila earthquake (April 6, 2009). Methods 958 triage documents were analysed for patients pain severity, pain type, and treatment efficacy. Results A third of pain patients reported pain with a prevalence of 34.6%. More than half of pain patients reported severe pain (58.8%). Analgesic agents were limited to available drugs: anti-inflammatory agents, paracetamol, and weak opioids. Reduction in verbal numerical pain scores within the first 24 hours after treatment was achieved with the medications at hand. Pain prevalence and characterization exhibited a biphasic pattern with acute pain syndromes owing to trauma occurring in the first 15 days after the earthquake; traumatic pain then decreased and re-surged at around week five, owing to rebuilding efforts. In the second through fourth week, reports of pain occurred mainly owing to relapses of chronic conditions. Conclusions This study indicates that pain is prevalent during natural disasters, may exhibit a discernible pattern over the weeks following the event, and current drug treatments in this region may be adequate for emergency situations. PMID:22747796

  6. Putting down roots in earthquake country-Your handbook for earthquakes in the Central United States

    USGS Publications Warehouse

    Contributors: Dart, Richard; McCarthy, Jill; McCallister, Natasha; Williams, Robert A.

    2011-01-01

    This handbook provides information to residents of the Central United States about the threat of earthquakes in that area, particularly along the New Madrid seismic zone, and explains how to prepare for, survive, and recover from such events. It explains the need for concern about earthquakes for those residents and describes what one can expect during and after an earthquake. Much is known about the threat of earthquakes in the Central United States, including where they are likely to occur and what can be done to reduce losses from future earthquakes, but not enough has been done to prepare for future earthquakes. The handbook describes such preparations that can be taken by individual residents before an earthquake to be safe and protect property.

  7. Causes of earthquakes and lithospheric plates movement

    NASA Astrophysics Data System (ADS)

    Ost?ihansk, L.

    2012-11-01

    The goal of the paper was to verify triggering of earthquakes by the length of day variations, i.e. the sidereal 13.66 days Earth's rotation variations, in contrast with tidal biweekly 14.76 days variations (full and new Moon), which for hundred years of investigation give negative results. Earthquake triggering governed by sidereal variations caused by variable Moon's declination accelerates and decelerates the Earth's rotation. Profound Schuster's test proved that earthquakes are triggered both in Earth's deceleration and acceleration. For this investigation the most prominent earthquakes from 2010-2011 were used from Mid-Atlantic Ridge, Southeast Indian Ridge, Sumatra and Andaman Sea, Chile trench, Haiti and Honshu region including important older earthquakes of Sumatra 26 December 2004 and Denali Fault 3 November 2002. Dominant number of earthquake occurring in extremes of length of day variations initiated the calculation of forces acting in these time intervals. Calculated forces of tidal force acting on Earth's flattening and the westward drift are strong enough to trigger earthquakes and the movement of plates follows from GPS performed immediately after earthquakes on continents and from increased number of earthquakes of the side of the mid-ocean ridge belonging to the moving plate. Generally the Northern Hemisphere moves quicker westward than the Southern one. Earthquakes are repeated in 19 yr Metonic cycle. Repetitions caused by tidal force acting on Earth's fattening are exact in date. Repetitions caused by westward drift are delayed for several months.

  8. Earthquakes at North Atlantic passive margins

    SciTech Connect

    Gregersen, S. ); Basham, P.W. )

    1989-01-01

    The main focus of this volume is the earthquakes that occur at and near the continental margins on both sides of the North Atlantic. The book, which contains the proceedings of the NATO workshop on Causes and Effects of Earthquakes at Passive Margins and in Areas of Postglacial Rebound on Both Sides of the North Atlantic, draws together the fields of geophysics, geology and geodesy to address the stress and strain in the Earth's crust. The resulting earthquakes produced on ancient geological fault zones and the associated seismic hazards these pose to man are also addressed. Postglacial rebound in North America and Fennoscandia is a minor source of earthquakes today, during the interglacial period, but evidence is presented to suggest that the ice sheets suppressed earthquake strain while they were in place, and released this strain as a pulse of significant earthquakes after the ice melted about 9000 years ago.

  9. Evidence for Ancient Mesoamerican Earthquakes

    NASA Astrophysics Data System (ADS)

    Kovach, R. L.; Garcia, B.

    2001-12-01

    Evidence for past earthquake damage at Mesoamerican ruins is often overlooked because of the invasive effects of tropical vegetation and is usually not considered as a casual factor when restoration and reconstruction of many archaeological sites are undertaken. Yet the proximity of many ruins to zones of seismic activity would argue otherwise. Clues as to the types of damage which should be soughtwere offered in September 1999 when the M = 7.5 Oaxaca earthquake struck the ruins of Monte Alban, Mexico, where archaeological renovations were underway. More than 20 structures were damaged, 5 of them seriously. Damage features noted were walls out of plumb, fractures in walls, floors, basal platforms and tableros, toppling of columns, and deformation, settling and tumbling of walls. A Modified Mercalli Intensity of VII (ground accelerations 18-34 %b) occurred at the site. Within the diffuse landward extension of the Caribbean plate boundary zone M = 7+ earthquakes occur with repeat times of hundreds of years arguing that many Maya sites were subjected to earthquakes. Damage to re-erected and reinforced stelae, walls, and buildings were witnessed at Quirigua, Guatemala, during an expedition underway when then 1976 M = 7.5 Guatemala earthquake on the Motagua fault struck. Excavations also revealed evidence (domestic pttery vessels and skeleton of a child crushed under fallen walls) of an ancient earthquake occurring about the teim of the demise and abandonment of Quirigua in the late 9th century. Striking evidence for sudden earthquake building collapse at the end of the Mayan Classic Period ~A.D. 889 was found at Benque Viejo (Xunantunich), Belize, located 210 north of Quirigua. It is argued that a M = 7.5 to 7.9 earthquake at the end of the Maya Classic period centered in the vicinity of the Chixoy-Polochic and Motagua fault zones cound have produced the contemporaneous earthquake damage to the above sites. As a consequences this earthquake may have accelerated the collapse of the hiearchical authority at these locations and may have contributed to the end of the Classic culture at other nearby sites in proximity to the Caribbean plate boundary zone.

  10. Twitter earthquake detection: Earthquake monitoring in a social world

    USGS Publications Warehouse

    Earle, Paul; Bowden, Daniel C.; Guy, Michelle R.

    2011-01-01

    The U.S. Geological Survey (USGS) is investigating how the social networking site Twitter, a popular service for sending and receiving short, public text messages, can augment USGS earthquake response products and the delivery of hazard information. Rapid detection and qualitative assessment of shaking events are possible because people begin sending public Twitter messages (tweets) with in tens of seconds after feeling shaking. Here we present and evaluate an earthquake detection procedure that relies solely on Twitter data. A tweet-frequency time series constructed from tweets containing the word "earthquake" clearly shows large peaks correlated with the origin times of widely felt events. To identify possible earthquakes, we use a short-term-average, long-term-average algorithm. When tuned to a moderate sensitivity, the detector finds 48 globally-distributed earthquakes with only two false triggers in five months of data. The number of detections is small compared to the 5,175 earthquakes in the USGS global earthquake catalog for the same five-month time period, and no accurate location or magnitude can be assigned based on tweet data alone. However, Twitter earthquake detections are not without merit. The detections are generally caused by widely felt events that are of more immediate interest than those with no human impact. The detections are also fast; about 75% occur within two minutes of the origin time. This is considerably faster than seismographic detections in poorly instrumented regions of the world. The tweets triggering the detections also provided very short first-impression narratives from people who experienced the shaking.

  11. Crustal rheology control on earthquake activity across the eastern margin of the Tibetan Plateau: Insights from numerical modelling

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Zhu, Bo-Jing; Yang, Xiao-Lin; Shi, Yao-Lin

    2015-03-01

    The devastating 2008 Mw7.9 Wenchuan and 2013 Mw6.6 Lushan earthquakes occurred in the Longmen Shan (LMS) fault zone, the eastern margin of the Tibetan Plateau. Seismology investigation reveals that earthquakes of Ms > 5.0 are frequently recorded in the eastern Tibetan Plateau, however rare earthquake of Ms > 5.0 and only a few earthquakes of 3.0 < Ms < 5.0 have been recorded in the Sichuan Basin. This study investigates the relation between the crustal rheology and the earthquake activity across the eastern margin of the Tibetan Plateau through 3D numerical experiments assuming visco-elasticity rheology. We setup several finite element lithospheric models based on different rheological structure. The interseismic stress accumulation processes in the models are simulated with boundary conditions of steady compressional deformation rate constrained by GPS observations. The results show that the crustal stress accumulation process across the eastern margin of the Tibetan Plateau is significantly controlled by the regional crustal rheology, which presents large horizontal viscosity variation in the lower crusts between the Tibetan Plateau and the Sichuan Basin. The stress accumulation rate in the upper crust of the eastern Tibetan Plateau is much higher than the Sichuan Basin. This stress spatial distribution explains the seismology observation that earthquakes are densely recorded in the eastern Tibetan Plateau, whereas rarely in the Sichuan Basin. The stress concentration nearly at the bottom of the entire LMS fault zone is thought to be responsible for the generation of the 2008 Mw7.9 Wenchuan and 2013 Mw6.6 Lushan earthquakes. There is a high possibility of future earthquakes in the seismic gaps at the southwest segment of the LMS fault zone, where it was stress accumulated but did not rupture during the last two events of the 2008 Wenchuan and 2013 Lushan earthquakes.

  12. Geological and historical evidence of irregular recurrent earthquakes in Japan.

    PubMed

    Satake, Kenji

    2015-10-28

    Great (M∼8) earthquakes repeatedly occur along the subduction zones around Japan and cause fault slip of a few to several metres releasing strains accumulated from decades to centuries of plate motions. Assuming a simple 'characteristic earthquake' model that similar earthquakes repeat at regular intervals, probabilities of future earthquake occurrence have been calculated by a government committee. However, recent studies on past earthquakes including geological traces from giant (M∼9) earthquakes indicate a variety of size and recurrence interval of interplate earthquakes. Along the Kuril Trench off Hokkaido, limited historical records indicate that average recurrence interval of great earthquakes is approximately 100 years, but the tsunami deposits show that giant earthquakes occurred at a much longer interval of approximately 400 years. Along the Japan Trench off northern Honshu, recurrence of giant earthquakes similar to the 2011 Tohoku earthquake with an interval of approximately 600 years is inferred from historical records and tsunami deposits. Along the Sagami Trough near Tokyo, two types of Kanto earthquakes with recurrence interval of a few hundred years and a few thousand years had been recognized, but studies show that the recent three Kanto earthquakes had different source extents. Along the Nankai Trough off western Japan, recurrence of great earthquakes with an interval of approximately 100 years has been identified from historical literature, but tsunami deposits indicate that the sizes of the recurrent earthquakes are variable. Such variability makes it difficult to apply a simple 'characteristic earthquake' model for the long-term forecast, and several attempts such as use of geological data for the evaluation of future earthquake probabilities or the estimation of maximum earthquake size in each subduction zone are being conducted by government committees. PMID:26392616

  13. Earthquake Swarms Near the Northern End of the Calaveras Fault

    NASA Astrophysics Data System (ADS)

    Walter, S.; Schwartz, D.

    2008-12-01

    The Calaveras fault splays off the San Andreas fault near the Pinnacles National Monument in central California and extends northward over 160 km into the San Francisco Bay area where it apparently ends near the town of Danville. While the southern and central Calaveras creep at a high rate of about 14 mm/yr and produce frequent small and moderate earthquakes, the northern Calaveras fault is basically locked with only minor creep and little or no seismicity. The northern Calaveras has not produced a large earthquake in over 300 years. Earthquake probability estimates for the Calaveras fault are 10-11% for a M6.7 or larger within the next 30 years, with the highest probability on the northern Calaveras. The San Ramon Valley adjacent to the northern Calaveras fault is the locus of earthquake swarm activity in the Bay Area. Five notable swarms have occurred there during the past 35 years. These swarms: 1) are primarily located to the east and northeast of the Calaveras in a section of crust bounded on the east by the Mt. Diablo blind thrust and the Concord-Green Valley fault ; 2) do not exhibit a mainshock-aftershock pattern as the largest event may occur later in the sequence; 3) have depths limited to about 8 km, and 4) are not aligned with the dominant NW-SE trend of most faults in the Bay Area and in at least two cases trend orthogonally to the Calaveras fault. The most well developed of these swarms was the Alamo swarm that began in April, 1990 and produced 351 earthquakes over 42 days. It included four M4 events, two of which occurred later in the sequence. The swarm defined a linear fault patch nearly 6 km long extending east-northeast from the northern end of the Calaveras fault, with seismicity between depths of 5-9 km. Left-lateral, strike-slip focal mechanisms for the larger events aligned well with the trend of the swarm. The earthquake swarm activity in the San Ramon Valley reflects deformation of a structurally complex block responding to the transfer of slip from the Calaveras to the Concord-Green Valley fault.

  14. Carcinoid Tumor: Frequently Asked Questions

    MedlinePLUS

    ... unlikely. More likely a carcinoid originates in the terminal ileum (which is so close to the appendix ... far as the liver while carcinoids of the terminal ileum much more frequently do so. But if ...

  15. Identified EM Earthquake Precursors

    NASA Astrophysics Data System (ADS)

    Jones, Kenneth, II; Saxton, Patrick

    2014-05-01

    Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After a number of custom rock experiments, two hypotheses were formed which could answer the EM wave model. The first hypothesis concerned a sufficient and continuous electron movement either by surface or penetrative flow, and the second regarded a novel approach to radio transmission. Electron flow along fracture surfaces was determined to be inadequate in creating strong EM fields, because rock has a very high electrical resistance making it a high quality insulator. Penetrative flow could not be corroborated as well, because it was discovered that rock was absorbing and confining electrons to a very thin skin depth. Radio wave transmission and detection worked with every single test administered. This hypothesis was reviewed for propagating, long-wave generation with sufficient amplitude, and the capability of penetrating solid rock. Additionally, fracture spaces, either air or ion-filled, can facilitate this concept from great depths and allow for surficial detection. A few propagating precursor signals have been detected in the field occurring with associated phases using custom-built loop antennae. Field testing was conducted in Southern California from 2006-2011, and outside the NE Texas town of Timpson in February, 2013. The antennae have mobility and observations were noted for recurrence, duration, and frequency response. At the Southern California field sites, one loop antenna was positioned for omni-directional reception and also detected a strong First Schumann Resonance; however, additional Schumann Resonances were absent. At the Timpson, TX field sites, loop antennae were positioned for directional reception, due to earthquake-induced, hydraulic fracturing activity currently conducted by the oil and gas industry. Two strong signals, one moderately strong signal, and approximately 6-8 weaker signals were detected in the immediate vicinity. The three stronger signals were mapped by a biangulation technique, followed by a triangulation technique for confirmation. This was the first antenna mapping technique ever performed for determining possible earthquake epicenters. Six and a half months later, Timpson experienced two M4 (M4.1 and M4.3) earthquakes on September 2, 2013 followed by a M2.4 earthquake three days later, all occurring at a depth of five kilometers. The Timpson earthquake activity now has a cyclical rate and a forecast was given to the proper authorities. As a result, the Southern California and Timpson, TX field results led to an improved design and construction of a third prototype antenna. With a loop antenna array, a viable communication system, and continuous monitoring, a full fracture cycle can be established and observed in real-time. In addition, field data could be reviewed quickly for assessment and lead to a much more improved earthquake forecasting capability. The EM precursors determined by this method appear to surpass all prior precursor claims, and the general public will finally receive long overdue forecasting.

  16. The occurrence of earthquake-triggered landslides

    NASA Astrophysics Data System (ADS)

    Ghahramani, M.; Evans, S. G.; Natural Disaster Systems Research Group

    2011-12-01

    A database containing 136 landslide-triggering earthquakes worldwide, with magnitudes greater than the minimum observed threshold for causing landslides (M4.5), has been compiled for the period of 1998 -2009. Our data sources include a comprehensive review of the existing literature on earthquake-triggered landslides, and also a USGS-based earthquake catalog (PAGER-CAT) which contains information on earthquake-induced secondary events. Only 14 earthquakes out of 136 seismic events induced significant numbers of landslides (>250). We compared the number of landslide-triggering earthquakes with the total number of earthquakes with M ? 4.5 (n=68,734) during the same period of time. The result shows only 0.2 percent of earthquakes triggered landslides and only 4.5% of earthquakes of M > 6 resulted in the occurrence of earthquake-triggered landslides. In addition, we compiled a database of 37 large-scale landslides, involving initial failure volumes of greater than 20 Mm3 that occurred worldwide in the period of 1900 to 2010. The database contains large-scale earthquake-triggered (n=18) and non-earthquake-triggered landslides (n=19) (ETL and NETL respectively), i.e., ca. 50% of large-scale landslides were induced by seismic activity. Surprisingly, the volume-temporal frequency curves of ETL and NETL show almost identical slope and intercept. Thus for a given volume, the annual frequency of ETL is almost identical to NETL in the 110 year period. We found that, in contrast to previous studies, the volume of the largest landslide triggered by a given landslide-triggering earthquake is not found to be a function of earthquake magnitude. We calculated peak ground acceleration (PGA) for the 18 large-scale ETLs at the site of each occurrence. PGA values in the range of 0.02 g to 0.35 g were obtained. We show that PGA values are well-correlated with the volume of landslides below a threshold of ca. 100 Mm3. Above this threshold, the relationship between PGA and ETL volume shows complex and nonlinear behaviour. The results suggest that 1) other special conditions are required for significant earthquake-triggered landslides to occur, and 2) that very large earthquake-triggered landslides (volume greater than 100 Mm3) result from complex progressive failure mechanisms initiated by seismic shaking (i.e., above this threshold volume, landslide volume is independent of PGA).

  17. Why so few? Landslides triggered by the 2002 Denali earthquake, Alaska

    NASA Astrophysics Data System (ADS)

    Gorum, Tolga; Korup, Oliver; van Westen, Cees J.; van der Meijde, Mark; Xu, Chong; van der Meer, Freek D.

    2014-07-01

    The 2002 Mw 7.9 Denali Fault earthquake, Alaska, provides an unparalleled opportunity to investigate in quantitative detail the regional hillslope mass-wasting response to strong seismic shaking in glacierized terrain. We present the first detailed inventory of ?1580 coseismic slope failures, out of which some 20% occurred above large valley glaciers, based on mapping from multi-temporal remote sensing data. We find that the Denali earthquake produced at least one order of magnitude fewer landslides in a much narrower corridor along the fault ruptures than empirical predictions for an M ?8 earthquake would suggest, despite the availability of sufficiently steep and dissected mountainous topography prone to frequent slope failure. In order to explore potential controls on the reduced extent of regional coseismic landsliding we compare our data with inventories that we compiled for two recent earthquakes in periglacial and formerly glaciated terrain, i.e. at Yushu, Tibet (Mw 6.9, 2010), and Aysn Fjord, Chile (2007 Mw 6.2). Fault movement during these events was, similarly to that of the Denali earthquake, dominated by strike-slip offsets along near-vertical faults. Our comparison returns very similar coseismic landslide patterns that are consistent with the idea that fault type, geometry, and dynamic rupture process rather than widespread glacier cover were among the first-order controls on regional hillslope erosional response in these earthquakes. We conclude that estimating the amount of coseismic hillslope sediment input to the sediment cascade from earthquake magnitude alone remains highly problematic, particularly if glacierized terrain is involved.

  18. Relationships Between Earthquakes and Mapped Faults

    NASA Astrophysics Data System (ADS)

    Weiser, D. A.

    2011-12-01

    A fundamental question that needs to be addressed by natural hazards studies asks, "Can one use an existing fault map to accurately determine maximum magnitude for earthquakes in a region?" Currently, fault maps are used to assess local and regional hazards, thus making them an important tool in determining potential magnitude and shaking for an area. Regressions between magnitude and rupture dimensions are based on post-earthquake observations. But, these regressions are employed to estimate magnitude, using observations taken before an earthquake has occurred. Since future magnitude estimates are based on rupture length of a fault, and not the previously mapped fault trace, it is important to understand the relationship between mapped faults and earthquakes. Mapped faults are the foundation of many seismic hazard studies. It is generally assumed that fault traces constrain the location, orientation, and size of future earthquakes. Yet many earthquakes, like the 1992 Landers, CA and 1999 Denali, AK earthquakes, rupture beyond previously mapped traces. Other events, like the 1994 Northridge, CA and the 2010 Christchurch, New Zealand earthquakes, serve as additional evidence that large earthquakes can and do occur off of mapped faults. My study examines the relationship between earthquakes and pre-existing faults, extends Wesnousky's recent fault compilation [2006], and expands Black's [2008] fault-jumping probability models. I update Wesnousky's [2006] data set to include additional earthquakes, for which surface rupture maps have recently been published. I add additional parameters and use this new data set to estimate fault-jumping probability. I distinguish between three types of faults; those already mapped at a scale appropriate to hazard studies such as Uniform California Earthquake Rupture Forecasts of 2007 and 2011; those that could be mapped from available surface imaging like LIDAR and high resolution optical pictures; and those that have no surface evidence detectable with present technology. I also distinguish between several types of earthquake ruptures; those that stay inside the limits of mapped faults; those that push the limits; those that violate the limits; and those that occur off of mapped faults. I match the fault types with the earthquake types, and make quantitative models of the probability that earthquakes will extend beyond mapped fault traces.

  19. Earthquake swarms reveal submarine magma unrest induced by distant mega-earthquakes: Andaman Sea region

    NASA Astrophysics Data System (ADS)

    Špičák, Aleš; Vaněk, Jiří

    2016-02-01

    Little is known about earthquake-triggered magma intrusions or eruptions of submarine volcanoes. The analysis of teleseismic earthquake occurrence performed in this study offers a tool to address such enigmatic and inaccessible processes. In the past ten years, the Andaman Sea region repeatedly became a site of shallow earthquake swarms that followed distant mega-earthquakes by days to weeks. The MW 9.1 December 26, 2004 Sumatra-Andaman earthquake was followed by two earthquake swarms about 600 km northward in the Andaman Sea region, delayed by 30 and 35 days, respectively. Earthquakes of one of these seismic episodes, the extensive January 2005 earthquake swarm, migrated laterally at a rate of about 0.25 km per hour during the swarm evolution. The strong Indian Ocean MW 8.6 and 8.2 April 11, 2012 earthquake doublet west of Northern Sumatra was followed by an earthquake swarm approximately 800 km northward in the Andaman Sea region, delayed by 13 days. All the three swarms that followed the 2004 and 2012 mega-earthquakes occurred beneath distinct seamounts and seafloor ridges. Based on the observations of migration of earthquakes during the swarm and swarm occurrence beneath distinct highs at the seafloor, we conclude that these earthquake swarms probably resulted as a consequence of magma unrest induced by static and/or dynamic stress changes following the distant mega-earthquakes. Repeated occurrence of such a phenomenon suggests that the arc magma reservoirs beneath the Andaman Sea have recently reached some form of criticality and are vulnerable to even small stress changes. The Andaman seafloor could thus become a site of submarine volcanic eruptions in near future and deserves close attention of Earth scientists.

  20. Characteristics of Andean earthquakes felt at long distances in Brazil

    NASA Astrophysics Data System (ADS)

    Frana, G. S.; Assumpo, M.; Santiago, P. S.

    2007-05-01

    In the past several decades, more than 40 Andean earthquakes have been felt in Brazilian cities, thousands of kilometers away from the epicenter, especially by oscillations of high-rise buildings. Because of the increase in population and skyscrapers in large cities, such long-distance effects are becoming more frequent. In So Paulo, for example, such macroseismic effects have been observed every 3-5 years on average. We present a study of the characteristics of the earthquakes and cities more susceptible to cause high-rise buildings to oscillate. Most earthquakes occur at intermediate or large depths, such as in the Jujuy and Santiago del Estero regions of northern Argentina. Magnitudes as low as 5.0 mb have caused long distance macroseismic effects. Most affected cities lie in sedimentary basins, such as So Paulo and Manaus, which can amplify the ground motions through basin resonance. In some cases, buildings with the longest axis oriented perpendicular to the largest S amplitudes (SH component) seem to be more susceptible to oscillations. An analysis of the ground motion amplitudes, as recorded by nearby broadband stations, will be presented.

  1. Earthquake hazards on the cascadia subduction zone.

    PubMed

    Heaton, T H; Hartzell, S H

    1987-04-10

    Large subduction earthquakes on the Cascadia subduction zone pose a potential seismic hazard. Very young oceanic lithosphere (10 million years old) is being subducted beneath North America at a rate of approximately 4 centimeters per year. The Cascadia subduction zone shares many characteristics with subduction zones in southern Chile, southwestern Japan, and Colombia, where comparably young oceanic lithosphere is also subducting. Very large subduction earthquakes, ranging in energy magnitude (M(w)) between 8 and 9.5, have occurred along these other subduction zones. If the Cascadia subduction zone is also storing elastic energy, a sequence of several great earthquakes (M(w) 8) or a giant earthquake (M(w) 9) would be necessary to fill this 1200-kilometer gap. The nature of strong ground motions recorded during subduction earthquakes of M(w) less than 8.2 is discussed. Strong ground motions from even larger earthquakes (M(w) up to 9.5) are estimated by simple simulations. If large subduction earthquakes occur in the Pacific Northwest, relatively strong shaking can be expected over a large region. Such earthquakes may also be accompanied by large local tsunamis. PMID:17789780

  2. Meeting focuses on catastrophic Asian earthquakes

    NASA Astrophysics Data System (ADS)

    Gupta, Harsh K.

    The International Association of Seismology and Physics of the Earth's Interior (IAS-PEI) and the Asian Seismological Commission met August 1-3, 1996, in Tangshan, China. Twenty years ago, Tangshan was destroyed by the century's worst earthquake, which killed an estimated 243,000 people.It was the first meeting of the Asian Seismological Commission (ASC), a group formed in 1995 by the IASPEI umbrella, to improve understanding of geological processes in Asia and to mitigate earthquake disasters. Because of its widespread seismic activity, the vast, populated territory of Asia has more catastrophic earthquakes than other regions of the world (see Figure 1). During the period from 1892 to 1992, 50 percent of the world's major earthquakes (magnitude greater than 8) occurred in Asia and the Southern Pacific region. Economic losses of more than $100 billion from the most recent major Asian earthquake that occurred in Kobe, Japan, in early 1995, make Kobe the most expensive earthquake in the world. In September 1993, the Latur earthquake in the stable shield region of southern India claimed 10,000 lives, and although of only 6.1 magnitude, was the deadliest stable continental region earthquake.

  3. Earthquake source fault beneath Tokyo.

    PubMed

    Sato, Hiroshi; Hirata, Naoshi; Koketsu, Kazuki; Okaya, David; Abe, Susumu; Kobayashi, Reiji; Matsubara, Makoto; Iwasaki, Takaya; Ito, Tanio; Ikawa, Takeshi; Kawanaka, Taku; Kasahara, Keiji; Harder, Steven

    2005-07-15

    Devastating earthquakes occur on a megathrust fault that underlies the Tokyo metropolitan region. We identify this fault with use of deep seismic reflection profiling to be the upper surface of the Philippine Sea plate. The depth to the top of this plate, 4 to 26 kilometers, is much shallower than previous estimates based on the distribution of seismicity. This shallower plate geometry changes the location of maximum finite slip of the 1923 Kanto earthquake and will affect estimations of strong ground motion for seismic hazards analysis within the Tokyo region. PMID:16020734

  4. Earthquake occurrence and effects.

    PubMed

    Adams, R D

    1990-01-01

    Although earthquakes are mainly concentrated in zones close to boundaries of tectonic plates of the Earth's lithosphere, infrequent events away from the main seismic regions can cause major disasters. The major cause of damage and injury following earthquakes is elastic vibration, rather than fault displacement. This vibration at a particular site will depend not only on the size and distance of the earthquake but also on the local soil conditions. Earthquake prediction is not yet generally fruitful in avoiding earthquake disasters, but much useful planning to reduce earthquake effects can be done by studying the general earthquake hazard in an area, and taking some simple precautions. PMID:2347628

  5. Observed Weather Satellite Thermal IR Responses Prior to Earthquakes

    NASA Astrophysics Data System (ADS)

    Bryant, N. A.; Zobrist, A. L.; Logan, L. L.; Freund, F.; Nishenko, S.

    2002-12-01

    A number of observers claim to have seen thermal anomalies prior to earthquakes, but subsequent analysis by others have failed to produce similar findings. It was the purpose of this study to determine if thermal anomalies could be found in association with known earthquakes by systematically co-registering weather satellite images at the sub-pixel level and then determining if statistically significant responses had occurred prior to an event. Earthquakes associated with plate movement (strike-slip and thrust faulting), rather than volcanism, were to be considered. A new set of automatic co-registration procedures were developed for this task to accommodate all properties particular to weather satellite observations taken at night. Spacecraft and sensor ephemeris and the horizontal displacement due to elevation were all factored in, and final adjustment for minor satellite deviations (related to roll, pitch, and yaw) were made by using image-to-image tiepoint correlations. Reliance upon visual clues in an image (frequently the subject of debate in the past) is not required. The technique relies on the general condition where ground cools after sunset. The technique applies best to the use of the geosynchronous weather satellites (GOES, Meteosat, and GMS), where images are taken every thirty minutes. Use of the geosynchronous satellites also reduces the potential for miscalculation of trends due to weather front movement or local cloud/fog formation. The polar orbiting satellites have better resolution (1km vs 5km) and better signal-to-noise, but only acquire images twice during an evening, thereby making trend analysis difficult. Case studies investigated to date include the Hector Mine California and Ikrit Turkey earthquakes of 1999, and the Bhuj India quake of 2001. The result of the new analytic procedures has been the observance of apparent heating trends close to epicenters in satellite data acquisitions a few hours prior to an earthquake. When observations along known fault-lines showed a much-reduced `temperature' decline through the evening, or in some cases an actual `temperature' increase, an earthquake occurred. This result may indicate mid-infrared luminescence associated with crustal deformation(Freund, 2002), rather than heat emission. Other events are currently under investigation using the methods developed.

  6. Tilt precursors before earthquakes on the San Andreas fault, California

    USGS Publications Warehouse

    Johnston, M.J.S.; Mortensen, C.E.

    1974-01-01

    An array of 14 biaxial shallow-borehole tiltmeters (at 10-7 radian sensitivity) has been installed along 85 kilometers of the San Andreas fault during the past year. Earthquake-related changes in tilt have been simultaneously observed on up to four independent instruments. At earthquake distances greater than 10 earthquake source dimensions, there are few clear indications of tilt change. For the four instruments with the longest records (>10 months), 26 earthquakes have occurred since July 1973 with at least one instrument closer than 10 source dimensions and 8 earthquakes with more than one instrument within that distance. Precursors in tilt direction have been observed before more than 10 earthquakes or groups of earthquakes, and no similar effect has yet been seen without the occurrence of an earthquake.

  7. Earthquake and Tsunami booklet based on two Indonesia earthquakes

    NASA Astrophysics Data System (ADS)

    Hayashi, Y.; Aci, M.

    2014-12-01

    Many destructive earthquakes occurred during the last decade in Indonesia. These experiences are very important precepts for the world people who live in earthquake and tsunami countries. We are collecting the testimonies of tsunami survivors to clarify successful evacuation process and to make clear the characteristic physical behaviors of tsunami near coast. We research 2 tsunami events, 2004 Indian Ocean tsunami and 2010 Mentawai slow earthquake tsunami. Many video and photographs were taken by people at some places in 2004 Indian ocean tsunami disaster; nevertheless these were few restricted points. We didn't know the tsunami behavior in another place. In this study, we tried to collect extensive information about tsunami behavior not only in many places but also wide time range after the strong shake. In Mentawai case, the earthquake occurred in night, so there are no impressive photos. To collect detail information about evacuation process from tsunamis, we contrived the interview method. This method contains making pictures of tsunami experience from the scene of victims' stories. In 2004 Aceh case, all survivors didn't know tsunami phenomena. Because there were no big earthquakes with tsunami for one hundred years in Sumatra region, public people had no knowledge about tsunami. This situation was highly improved in 2010 Mentawai case. TV programs and NGO or governmental public education programs about tsunami evacuation are widespread in Indonesia. Many people know about fundamental knowledge of earthquake and tsunami disasters. We made drill book based on victim's stories and painted impressive scene of 2 events. We used the drill book in disaster education event in school committee of west Java. About 80 % students and teachers evaluated that the contents of the drill book are useful for correct understanding.

  8. Earthquake research needed in California

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    According to an analysis by a group of seismologists and tectonophysicists from the Lamont-Doherty Geological Observatory of Columbia University and the Seismological Laboratory of the California Institute of Technology, there is an imperative need for extensive studies of the San Andreas fault system throughout its extent within the state of California. Although there is considerable controversy surrounding the question of which segment of the San Andreas system may produce the next earthquake, C.B. Raleigh, K. Sieh, L.R. Sykes, and D.L. Anderson report that it is conceivable that the entire fault in southern California could rupture at once. (Science, Sept. 17, 1982).The fears that a major earthquake may occur at anytime in southern California are based on numerous statistical factors underlying the idea that The longer it's been since the last big one, the sooner the next one will be. The timing of earthquakes along active seismic zones, particularly those that coincide with plate boundaries, seems to be directly related to the amount of displacement generated since the last such earthquake at the same location. For example, the recurrence rate of about 150 years for great earthquakes along the San Andreas fault in southern California and the displacement rate of about 3 cm per year for the segment of the last earthquake from Cholame Valley to Cajon Pass in 1857 suggest that the next such large event may occur in the near future. On this basis Raleigh et al. (Science, sup.) conclude that Both observations mark the San Andreas fault north and east of Los Angeles as a mature seismic gap and the prime candidate for producing southern California's next great earthquake. The expected consequences are described as appalling and as having a potential for severe losses of life and property from such a great earthquake The worst case, cited in a report issued by the National Security Council through the Federal Emergency Management Administration in 1980 for an earthquake magnitude of M=7.5 in southern California near Long Beach, could cause the loss of 20,000 lives and $69 billion in property damages.

  9. Estimating Casualties for Large Earthquakes Worldwide Using an Empirical Approach

    USGS Publications Warehouse

    Jaiswal, Kishor; Wald, David J.; Hearne, Mike

    2009-01-01

    We developed an empirical country- and region-specific earthquake vulnerability model to be used as a candidate for post-earthquake fatality estimation by the U.S. Geological Survey's Prompt Assessment of Global Earthquakes for Response (PAGER) system. The earthquake fatality rate is based on past fatal earthquakes (earthquakes causing one or more deaths) in individual countries where at least four fatal earthquakes occurred during the catalog period (since 1973). Because only a few dozen countries have experienced four or more fatal earthquakes since 1973, we propose a new global regionalization scheme based on idealization of countries that are expected to have similar susceptibility to future earthquake losses given the existing building stock, its vulnerability, and other socioeconomic characteristics. The fatality estimates obtained using an empirical country- or region-specific model will be used along with other selected engineering risk-based loss models for generation of automated earthquake alerts. These alerts could potentially benefit the rapid-earthquake-response agencies and governments for better response to reduce earthquake fatalities. Fatality estimates are also useful to stimulate earthquake preparedness planning and disaster mitigation. The proposed model has several advantages as compared with other candidate methods, and the country- or region-specific fatality rates can be readily updated when new data become available.

  10. Development of Tools for the Rapid Assessment of Landslide Potential in Areas Exposed to Intense Storms, Earthquakes, and Other Triggering Mechanisms

    NASA Astrophysics Data System (ADS)

    Highland, Lynn

    2014-05-01

    Landslides frequently occur in connection with other types of hazardous phenomena such as earthquake or volcanic activity and intense rainstorms. Strong shaking, for example, often triggers extensive landslides in mountainous areas, which can then complicate response and compound socio-economic impacts over shaking losses alone. The U.S. Geological Survey (USGS) is exploring different ways to add secondary hazards to its Prompt Assessment of Global Earthquakes for Response (PAGER) system, which has been developed to deliver rapid earthquake impact and loss assessments following significant global earthquakes. The PAGER team found that about 22 percent of earthquakes with fatalities have deaths due to secondary causes, and the percentage of economic losses they incur has not been widely studied, but is probably significant. The current approach for rapid assessment and reporting of the potential and distribution of secondary earthquake-induced landslides involves empirical models that consider ground acceleration, slope, and rock-strength. A complementary situational awareness tool being developed is a region-specific landslide database for the U.S. The latter will be able to define, in a narrative form, the landslide types (debris flows, rock avalanches, shallow versus deep) that generally occur in each area, along with the type of soils, geology and meteorological effects that could have a bearing on soil saturation, and thus susceptibility. When a seismic event occurs in the U.S. and the PAGER system generates web-based earthquake information, these landslide narratives will simultaneously be made available, which will help in the assessment of the nature of landslides in that particular region. This landslide profile database could also be applied to landslide events that are not triggered by earthquake shaking, in conjunction with National Weather Service Alerts and other landslide/debris-flow alerting systems. Currently, prototypes are being developed for both the slope-based and the narrative assessment of landslide susceptibility and hazard.

  11. Earthquake catalog for estimation of maximum earthquake magnitude, Central and Eastern United States: Part B, historical earthquakes

    USGS Publications Warehouse

    Wheeler, Russell L.

    2014-01-01

    Computation of probabilistic earthquake hazard requires an estimate of Mmax: the moment magnitude of the largest earthquake that is thought to be possible within a specified geographic region. The region specified in this report is the Central and Eastern United States and adjacent Canada. Parts A and B of this report describe the construction of a global catalog of moderate to large earthquakes that occurred worldwide in tectonic analogs of the Central and Eastern United States. Examination of histograms of the magnitudes of these earthquakes allows estimation of Central and Eastern United States Mmax. The catalog and Mmax estimates derived from it are used in the 2014 edition of the U.S. Geological Survey national seismic-hazard maps. Part A deals with prehistoric earthquakes, and this part deals with historical events.

  12. Earthquake history of the United States

    USGS Publications Warehouse

    Coffman, Jerry L., (Edited By); Von Hake, Carl A.; Stover, Carl W.

    1982-01-01

    This publication is a history of the prominent earthquakes in the United States from historical times through 1970. It supersedes all previous editions with the same or similar titles (see page ii) and, in addition to updating earthquake listings through 1970, contains several additions and corrections to previous issues. It also brings together under a common cover earthquake data previously listed in two separate reports: Earthquake History of the United States, Part I, Stronger Earthquakes of the United States (Exclusive of California and Western Nevada) and Earthquake History of the United States, Part II, Stronger Earthquakes of California and Western Nevada. Another addition to this publication is the inclusion of a section describing earthquakes in the Puerto Rico region. For the purpose of listing and describing earthquakes, the United States has been divided into nine regions: (1) Northeastern Region, which includes New England and New York activity and observations of the principal earthquakes of eastern Canada; (2) Eastern Region, including the central Appalachian seismic region activity and the area near Charleston, S.C.; (3) Central Region, which consists of the area between the region just described and the Rocky Mountains; (4) Western Mountain Region, which includes all remaining states except those on the Pacific coast; (5) Washington and Oregon; (6) Alaska; (7) Hawaii; (8) Puerto Rico; and (9) California and Western Nevada. This arrangement has been made chiefly with reference to the natural seismic divisions. It also is a convenient arrangement because there are only three states where there is an important division of earthquake activity: In Tennessee, there are quite distinct areas at opposite ends of the state that fall into different regions. Only central and eastern Nevada are included in the Western Mountain Region, as the activity of the western part is closely associated with that of California. Some earthquake activity has occurred in the part of Texas located in the Western Mountain Region. The map facing page 1 shows locations of all earthquakes in the regions that follow. A small map showing the area covered by each region immediately precedes the rsum of each chapter (except for the Alaska, Puerto Rico, and Hawaii regions). The seismic risk map below was developed in January 1969 for the conterminous United States by Dr. S. T. Algermissen of NOAA's Environmental Research Laboratories. Subject to revision as continuing research warrants, it is an updated edition of a map divides the United States into four zones: Zone 0, areas with no reasonable expectancy of earthquake damage; Zone 1, expected minor damage; Zone 2, expected moderate damage; and Zone 3, major destructive earthquakes may occur.

  13. Major earthquake shakes northern Pakistan

    NASA Astrophysics Data System (ADS)

    Kumar, Mohi

    A magnitude 7.6 earthquake that shook the western Himalayas on 8 October killed at least 23,000 in Pakistan and 1,400 in India, injured more than 50,000 people, and left more 2.5 million people homeless across the Kashmir region. The official death toll could exceed 30,000, placing this among most deadly earthquakes to have ever occurred on the Indian subcontinent.Scientists warn that, given the lack of development and poor construction in the area, future earthquakes in more densely populated areas could be devastating. David Simpson, president of the Incorporated Research Institutes for Seismology, said the 8 October quake ‘was a terrible disaster, but not to the level of what could happen in the future. This is yet again another warning message of things to come.”

  14. Precise earthquake locations show evidence of internal structures at intermediate-depth earthquake nests

    NASA Astrophysics Data System (ADS)

    Prieto, G.; Florez, M.; Dionicio, V.; Barrett, S. A.; Beroza, G. C.

    2012-12-01

    The mechanism for intermediate depth and deep earthquakes is still under debate. The temperatures and pressures are above the point where ordinary fractures ought to occur. Earthquake nests are regions of highly concentrated seismicity within subducting lithosphere that are isolated from nearby activity and may be key in revealing the mechanics of intermediate-depth earthquakes. We present precise earthquake locations of intermediate-depth earthquakes in the Bucaramanga nest, Colombia using double-difference algorithms combined with depth phases recorded at regional and teleseismic distances. Our results show an alignment of seismicity along subhorizontal and/or subvertical regions within the nest and a preferential location of larger earthquakes at the bottom of the cluster. These observed features might suggest preexisting structures within the subducting slab or some process that allows concentration of deformation and repeating ruptures along fractures.

  15. Earthquake Strong Ground Motion Scenario at the 2008 Olympic Games Sites, Beijing, China

    NASA Astrophysics Data System (ADS)

    Liu, L.; Rohrbach, E. A.; Chen, Q.; Chen, Y.

    2006-12-01

    Historic earthquake record indicates mediate to strong earthquakes have been frequently hit greater Beijing metropolitan area where is going to host the 2008 summer Olympic Games. For the readiness preparation of emergency response to the earthquake shaking for a mega event in a mega city like Beijing in summer 2008, this paper tries to construct the strong ground motion scenario at a number of gymnasium sites for the 2008 Olympic Games. During the last 500 years (the Ming and Qing Dynasties) in which the historic earthquake record are thorough and complete, there are at least 12 earthquake events with the maximum intensity of VI or greater occurred within 100 km radius centered at the Tiananmen Square, the center of Beijing City. Numerical simulation of the seismic wave propagation and surface strong ground motion is carried out by the pseudospectral time domain methods with viscoelastic material properties. To improve the modeling efficiency and accuracy, a multi-scale approach is adapted: the seismic wave propagation originated from an earthquake rupture source is first simulated by a model with larger physical domain with coarser grids. Then the wavefield at a given plane is taken as the source input for the small-scale, fine grid model for the strong ground motion study at the sites. The earthquake source rupture scenario is based on two particular historic earthquake events: One is the Great 1679 Sanhe-Pinggu Earthquake (M~8, Maximum Intensity XI at the epicenter and Intensity VIII in city center)) whose epicenter is about 60 km ENE of the city center. The other one is the 1730 Haidian Earthquake (M~6, Maximum Intensity IX at the epicenter and Intensity VIII in city center) with the epicentral distance less than 20 km away from the city center in the NW Haidian District. The exist of the thick Tertiary-Quaternary sediments (maximum thickness ~ 2 km) in Beijing area plays a critical role on estimating the surface ground motion at the Olympic Games sites, which are most located north of the city center.

  16. Assessing the risk of earthquakes in the eastern United States

    SciTech Connect

    Not Available

    1981-09-01

    Although earthquakes in the U.S. are generally considered California's problem, a number of major earthquakes have struck the central and eastern United States. The last damaging earthquake in the eastern U.S. occurred in 1886, near Charleston, SC, killing 60 people and causing extensive damage in Charleston. During the winter of 1811-12, three major earthquakes occurred near New Madrid in southeastern Missouri. Because the area, at that time, was sparsely populated, casualties were not extensive, but the quakes caused damage and ground shaking over an area 20 times larger than that for the 1906 San Francisco earthquake. Because of these earthquakes and others, the potential for damaging earthquakes in the eastern U.S. is real, and this was the subject of a recent meeting of geologists, seismologists, and engineers in Knoxville, TN, in September 1981. The highlights of their discussions are presented in this article.

  17. Material contrast does not predict earthquake rupture propagation direction

    USGS Publications Warehouse

    Harris, R.A.; Day, S.M.

    2005-01-01

    Earthquakes often occur on faults that juxtapose different rocks. The result is rupture behavior that differs from that of an earthquake occurring on a fault in a homogeneous material. Previous 2D numerical simulations have studied simple cases of earthquake rupture propagation where there is a material contrast across a fault and have come to two different conclusions: 1) earthquake rupture propagation direction can be predicted from the material contrast, and 2) earthquake rupture propagation direction cannot be predicted from the material contrast. In this paper we provide observational evidence from 70 years of earthquakes at Parkfield, CA, and new 3D numerical simulations. Both the observations and the numerical simulations demonstrate that earthquake rupture propagation direction is unlikely to be predictable on the basis of a material contrast. Copyright 2005 by the American Geophysical Union.

  18. Naturally occurring chemical carcinogens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Natural products are chemicals found in nature which have unique pharmacological effects. Humans are exposed to many of these bioactive naturally occurring chemicals via the air breathed, the water drunk and the food eaten. Exposure also occurs in clinical settings. Naturally occurring chemicals ...

  19. Fault failure with moderate earthquakes

    USGS Publications Warehouse

    Johnston, M.J.S.; Linde, A.T.; Gladwin, M.T.; Borcherdt, R.D.

    1987-01-01

    High resolution strain and tilt recordings were made in the near-field of, and prior to, the May 1983 Coalinga earthquake (ML = 6.7, ?? = 51 km), the August 4, 1985, Kettleman Hills earthquake (ML = 5.5, ?? = 34 km), the April 1984 Morgan Hill earthquake (ML = 6.1, ?? = 55 km), the November 1984 Round Valley earthquake (ML = 5.8, ?? = 54 km), the January 14, 1978, Izu, Japan earthquake (ML = 7.0, ?? = 28 km), and several other smaller magnitude earthquakes. These recordings were made with near-surface instruments (resolution 10-8), with borehole dilatometers (resolution 10-10) and a 3-component borehole strainmeter (resolution 10-9). While observed coseismic offsets are generally in good agreement with expectations from elastic dislocation theory, and while post-seismic deformation continued, in some cases, with a moment comparable to that of the main shock, preseismic strain or tilt perturbations from hours to seconds (or less) before the main shock are not apparent above the present resolution. Precursory slip for these events, if any occurred, must have had a moment less than a few percent of that of the main event. To the extent that these records reflect general fault behavior, the strong constraint on the size and amount of slip triggering major rupture makes prediction of the onset times and final magnitudes of the rupture zones a difficult task unless the instruments are fortuitously installed near the rupture initiation point. These data are best explained by an inhomogeneous failure model for which various areas of the fault plane have either different stress-slip constitutive laws or spatially varying constitutive parameters. Other work on seismic waveform analysis and synthetic waveforms indicates that the rupturing process is inhomogeneous and controlled by points of higher strength. These models indicate that rupture initiation occurs at smaller regions of higher strength which, when broken, allow runaway catastrophic failure. ?? 1987.

  20. Izmit, Turkey 1999 Earthquake Interferogram

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This image is an interferogram that was created using pairs of images taken by Synthetic Aperture Radar (SAR). The images, acquired at two different times, have been combined to measure surface deformation or changes that may have occurred during the time between data acquisition. The images were collected by the European Space Agency's Remote Sensing satellite (ERS-2) on 13 August 1999 and 17 September 1999 and were combined to produce these image maps of the apparent surface deformation, or changes, during and after the 17 August 1999 Izmit, Turkey earthquake. This magnitude 7.6 earthquake was the largest in 60 years in Turkey and caused extensive damage and loss of life. Each of the color contours of the interferogram represents 28 mm (1.1 inches) of motion towards the satellite, or about 70 mm (2.8 inches) of horizontal motion. White areas are outside the SAR image or water of seas and lakes. The North Anatolian Fault that broke during the Izmit earthquake moved more than 2.5 meters (8.1 feet) to produce the pattern measured by the interferogram. Thin red lines show the locations of fault breaks mapped on the surface. The SAR interferogram shows that the deformation and fault slip extended west of the surface faults, underneath the Gulf of Izmit. Thick black lines mark the fault rupture inferred from the SAR data. Scientists are using the SAR interferometry along with other data collected on the ground to estimate the pattern of slip that occurred during the Izmit earthquake. This then used to improve computer models that predict how this deformation transferred stress to other faults and to the continuation of the North Anatolian Fault, which extends to the west past the large city of Istanbul. These models show that the Izmit earthquake further increased the already high probability of a major earthquake near Istanbul.

  1. Pore-fluid migration and the timing of the 2005 M8.7 Nias earthquake

    USGS Publications Warehouse

    Hughes, K.L.H.; Masterlark, Timothy; Mooney, W.D.

    2011-01-01

    Two great earthquakes have occurred recently along the Sunda Trench, the 2004 M9.2 Sumatra-Andaman earthquake and the 2005 M8.7 Nias earthquake. These earthquakes ruptured over 1600 km of adjacent crust within 3 mo of each other. We quantitatively present poroelastic deformation analyses suggesting that postseismic fluid flow and recovery induced by the Sumatra-Andaman earthquake advanced the timing of the Nias earthquake. Simple back-slip simulations indicate that the megapascal (MPa)-scale pore-pressure recovery is equivalent to 7 yr of interseismic Coulomb stress accumulation near the Nias earthquake hypocenter, implying that pore-pressure recovery of the Sumatra-Andaman earthquake advanced the timing of the Nias earthquake by ~7 yr. That is, in the absence of postseismic pore-pressure recovery, we predict that the Nias earthquake would have occurred in 2011 instead of 2005. ?? 2011 Geological Society of America.

  2. Oklahoma's recent earthquakes and saltwater disposal.

    PubMed

    Walsh, F Rall; Zoback, Mark D

    2015-06-01

    Over the past 5 years, parts of Oklahoma have experienced marked increases in the number of small- to moderate-sized earthquakes. In three study areas that encompass the vast majority of the recent seismicity, we show that the increases in seismicity follow 5- to 10-fold increases in the rates of saltwater disposal. Adjacent areas where there has been relatively little saltwater disposal have had comparatively few recent earthquakes. In the areas of seismic activity, the saltwater disposal principally comes from "produced" water, saline pore water that is coproduced with oil and then injected into deeper sedimentary formations. These formations appear to be in hydraulic communication with potentially active faults in crystalline basement, where nearly all the earthquakes are occurring. Although most of the recent earthquakes have posed little danger to the public, the possibility of triggering damaging earthquakes on potentially active basement faults cannot be discounted. PMID:26601200

  3. Parallelization of the Coupled Earthquake Model

    NASA Technical Reports Server (NTRS)

    Block, Gary; Li, P. Peggy; Song, Yuhe T.

    2007-01-01

    This Web-based tsunami simulation system allows users to remotely run a model on JPL s supercomputers for a given undersea earthquake. At the time of this reporting, predicting tsunamis on the Internet has never happened before. This new code directly couples the earthquake model and the ocean model on parallel computers and improves simulation speed. Seismometers can only detect information from earthquakes; they cannot detect whether or not a tsunami may occur as a result of the earthquake. When earthquake-tsunami models are coupled with the improved computational speed of modern, high-performance computers and constrained by remotely sensed data, they are able to provide early warnings for those coastal regions at risk. The software is capable of testing NASA s satellite observations of tsunamis. It has been successfully tested for several historical tsunamis, has passed all alpha and beta testing, and is well documented for users.

  4. Numerical Simulation of Earthquake Generation Cycles before and after the 2011 Tohoku-Oki Earthquake in Northeast Japan

    NASA Astrophysics Data System (ADS)

    Nakata, R.; Ariyoshi, K.; Hyodo, M.; Hori, T.

    2014-12-01

    Along the Japan Trench, M7 class earthquakes have occurred in the past. Among them, earthquakes off the coast of Miyagi prefecture have occurred with recurrence intervals of approximately 30-40 years. The M 7.2 earthquake in 2005 is the latest before 2011. On 11 March 2011, the M 9.0 great interplate earthquake occurred off the coast of the Tohoku district (including Miyagi). Currently, it has been passed for more than three years since the M 9.0 earthquake. Post-seismic deformation has continued today, and Off-Miyagi earthquake has not occurred yet. We numerically simulated cycles for occurrences of seismic and aseismic events along the Japan Trench with the 3D geometry of the Pacific plate using the aging law, which is a type of rate- and state-dependent friction law. We evaluated simulation results achieved using different values of frictional parameters with respect to characteristics such as the slip history and crustal deformation before the Tohoku-Oki earthquake. Before the Tohoku-Oki earthquake, two slow slip events (SSEs) were observed on 2008 and 2011. The M=7.3 largest foreshock occurred on March 9 [Ito et al., 2013]. Source areas of the mainshock, the foreshock, and the SSEs are in the updip area of the Off-Miyagi earthquakes and post-seismic slip of the M9 earthquake. By now, we have approximately reproduced some characteristics of observed slips by using several sets of frictional parameter values. In our simulations, M=7.0-7.6 foreshock occurred 0.4~7 days before the mainshock (M=8.6-9.0). And the foreshock occurred within 10 years after the M=7.2-7.3 earthquake at Off-Miyagi. In these models, time interval between the mainshock and the first Off-Miyagi earthquake after the great earthquake tend to be shorter than the average recurrence interval of the past. This tendency was observed at Indonesia. Two M7 class earthquakes occurred before (2002) and after (2008) the 2004 Sumatra earthquake (M9.1). The source regions were at the south end of the rupture zone of the 2004 earthquake and the north end of the rupture zone of the 2005 Nias Island earthquake (M8.6) [Shearer & Burgmann, 2010]. We are now improving our model to reproduce other characteristics. Based on some of the reasonable results achieved, we will discuss possible scenarios for spatial-temporal evolution of slip after M9 class earthquakes.

  5. Unusual low-angle normal fault earthquakes after the 2011 Tohoku-oki megathrust earthquake

    NASA Astrophysics Data System (ADS)

    Yagi, Yuji; Okuwaki, Ryo; Enescu, Bogdan; Fukahata, Yukitoshi

    2015-12-01

    A few low-angle normal fault earthquakes at approximately the depth of the plate interface, with a strike nearly parallel to the trench axis, were detected immediately after the 2011 Tohoku-oki earthquake. After that, however, no such normal fault events have been observed until the occurrence of the 2014 M W 6.6 Fukushima-oki earthquake. Here we analyze the teleseismic body waveforms of the 2014 Fukushima-oki earthquake. We first compare the observed teleseismic body waves of the 2014 Fukushima-oki earthquake with those of the largest previous low-angle normal fault aftershock ( M W 6.6), which occurred on 12 March 2011, and then estimate the centroid depth and moment tensor solution of the 2014 Fukushima-oki earthquake. The teleseismic body waves and moment tensor solution of the 2014 Fukushima-oki earthquake are similar to those of the 2011 normal fault aftershock, which suggests that the 2014 Fukushima-oki earthquake occurred at a similar depth and had a similar mechanism to that of the 2011 aftershock. We detected five low-angle normal fault aftershocks at approximately the depth of the plate interface, with a strike nearly parallel to the trench axis, and confirmed that all of them except for the 2014 Fukushima-oki earthquake occurred within 17 days after the mainshock. The occurrence of these low-angle normal fault events is likely to reflect the reversal of shear stress due to overshooting of slip during the 2011 Tohoku-oki earthquake. We speculate that a fast but heterogeneous recovery of stress state at the plate interface may explain why these events preferentially occurred immediately after the megathrust event, while one of them occurred with a significant delay. In order to better understand the characteristics of stress state in the crust, we have to carefully observe the ongoing seismic activity around this region.

  6. The 2011 Yingjiang, China, earthquake: A volcano-related fluid-driven earthquake?

    NASA Astrophysics Data System (ADS)

    Lei, J.; Xie, F.; Mishra, O. P.; Lu, Y.; Zhang, G.; Li, Y.

    2011-12-01

    A high-resolution tomographic model inferred from local and teleseismic arrival-time data under Yunnan, southwest China shows that the 2011 Yingjiang earthquake (M 5.8) occurred around a low-velocity (low-V) anomaly that extends down to the upper part of the mantle transition zone and is attributable to upwelling flow of the active Tengchong volcano. Fluids in the flow may mainly originate from the dehydration of the eastward subduction of the Indian plate in the mantle transition zone and have reached the fault zone. Our results suggest that the occurrence of the Yingjiang earthquake could be closely related to fluids that might enhance the stress concentration on the seismogenic layer, as well as decrease the effective normal stress across the fault planes of the Da Yingjiang fault. We conclude that the Yingjiang earthquake might be a volcano-related fluid-driven earthquake. The successive occurrence of small earthquakes (M>4.0) and the Yingjiang aftershocks may imply the recent magmatism of Tengchong volcano. The 4 February 2011 Indo-Burma earthquake (M 6.4) occurred at ~90 km depth, suggesting that the Indian plate is still active and currently subducting eastward, which may explain why several moderate-large earthquakes, such as the 24 March 2011 Burma earthquake (M 7.2), have occurred recently in the region.

  7. Continuing megathrust earthquake potential in Chile after the 2014 Iquique earthquake

    NASA Astrophysics Data System (ADS)

    Hayes, Gavin P.; Herman, Matthew W.; Barnhart, William D.; Furlong, Kevin P.; Riquelme, Sebstian; Benz, Harley M.; Bergman, Eric; Barrientos, Sergio; Earle, Paul S.; Samsonov, Sergey

    2014-08-01

    The seismic gap theory identifies regions of elevated hazard based on a lack of recent seismicity in comparison with other portions of a fault. It has successfully explained past earthquakes (see, for example, ref. 2) and is useful for qualitatively describing where large earthquakes might occur. A large earthquake had been expected in the subduction zone adjacent to northern Chile, which had not ruptured in a megathrust earthquake since a M ~8.8 event in 1877. On 1 April 2014 a M 8.2 earthquake occurred within this seismic gap. Here we present an assessment of the seismotectonics of the March-April 2014 Iquique sequence, including analyses of earthquake relocations, moment tensors, finite fault models, moment deficit calculations and cumulative Coulomb stress transfer. This ensemble of information allows us to place the sequence within the context of regional seismicity and to identify areas of remaining and/or elevated hazard. Our results constrain the size and spatial extent of rupture, and indicate that this was not the earthquake that had been anticipated. Significant sections of the northern Chile subduction zone have not ruptured in almost 150 years, so it is likely that future megathrust earthquakes will occur to the south and potentially to the north of the 2014 Iquique sequence.

  8. Continuing megathrust earthquake potential in Chile after the 2014 Iquique earthquake.

    PubMed

    Hayes, Gavin P; Herman, Matthew W; Barnhart, William D; Furlong, Kevin P; Riquelme, Sebstian; Benz, Harley M; Bergman, Eric; Barrientos, Sergio; Earle, Paul S; Samsonov, Sergey

    2014-08-21

    The seismic gap theory identifies regions of elevated hazard based on a lack of recent seismicity in comparison with other portions of a fault. It has successfully explained past earthquakes (see, for example, ref.2) and is useful for qualitatively describing where large earthquakes might occur. A large earthquake had been expected in the subduction zone adjacent to northern Chile, which had not ruptured in a megathrust earthquake since a M?8.8 event in 1877. On 1 April 2014 a M8.2 earthquake occurred within this seismic gap. Here we present an assessment of the seismotectonics of the March-April 2014 Iquique sequence, including analyses of earthquake relocations, moment tensors, finite fault models, moment deficit calculations and cumulative Coulomb stress transfer. This ensemble of information allows us to place the sequence within the context of regional seismicity and to identify areas of remaining and/or elevated hazard. Our results constrain the size and spatial extent of rupture, and indicate that this was not the earthquake that had been anticipated. Significant sections of the northern Chile subduction zone have not ruptured in almost 150 years, so it is likely that future megathrust earthquakes will occur to the south and potentially to the north of the 2014 Iquique sequence. PMID:25119028

  9. Continuing megathrust earthquake potential in Chile after the 2014 Iquique earthquake

    USGS Publications Warehouse

    Hayes, Gavin P.; Herman, Matthew W.; Barnhart, William D.; Furlong, Kevin P.; Riquelme, Sebástian; Benz, Harley M.; Bergman, Eric; Barrientos, Sergio; Earle, Paul; Samsonov, Sergey

    2014-01-01

    The seismic gap theory identifies regions of elevated hazard based on a lack of recent seismicity in comparison with other portions of a fault. It has successfully explained past earthquakes (see, for example, ref. 2) and is useful for qualitatively describing where large earthquakes might occur. A large earthquake had been expected in the subduction zone adjacent to northern Chile which had not ruptured in a megathrust earthquake since a M ~8.8 event in 1877. On 1 April 2014 a M 8.2 earthquake occurred within this seismic gap. Here we present an assessment of the seismotectonics of the March–April 2014 Iquique sequence, including analyses of earthquake relocations, moment tensors, finite fault models, moment deficit calculations and cumulative Coulomb stress transfer. This ensemble of information allows us to place the sequence within the context of regional seismicity and to identify areas of remaining and/or elevated hazard. Our results constrain the size and spatial extent of rupture, and indicate that this was not the earthquake that had been anticipated. Significant sections of the northern Chile subduction zone have not ruptured in almost 150 years, so it is likely that future megathrust earthquakes will occur to the south and potentially to the north of the 2014 Iquique sequence.

  10. Issues on the Japanese Earthquake Hazard Evaluation

    NASA Astrophysics Data System (ADS)

    Hashimoto, M.; Fukushima, Y.; Sagiya, T.

    2013-12-01

    The 2011 Great East Japan Earthquake forced the policy of counter-measurements to earthquake disasters, including earthquake hazard evaluations, to be changed in Japan. Before the March 11, Japanese earthquake hazard evaluation was based on the history of earthquakes that repeatedly occurs and the characteristic earthquake model. The source region of an earthquake was identified and its occurrence history was revealed. Then the conditional probability was estimated using the renewal model. However, the Japanese authorities changed the policy after the megathrust earthquake in 2011 such that the largest earthquake in a specific seismic zone should be assumed on the basis of available scientific knowledge. According to this policy, three important reports were issued during these two years. First, the Central Disaster Management Council issued a new estimate of damages by a hypothetical Mw9 earthquake along the Nankai trough during 2011 and 2012. The model predicts a 34 m high tsunami on the southern Shikoku coast and intensity 6 or higher on the JMA scale in most area of Southwest Japan as the maximum. Next, the Earthquake Research Council revised the long-term earthquake hazard evaluation of earthquakes along the Nankai trough in May 2013, which discarded the characteristic earthquake model and put much emphasis on the diversity of earthquakes. The so-called 'Tokai' earthquake was negated in this evaluation. Finally, another report by the CDMC concluded that, with the current knowledge, it is hard to predict the occurrence of large earthquakes along the Nankai trough using the present techniques, based on the diversity of earthquake phenomena. These reports created sensations throughout the country and local governments are struggling to prepare counter-measurements. These reports commented on large uncertainty in their evaluation near their ends, but are these messages transmitted properly to the public? Earthquake scientists, including authors, are involved in the discussion of these issues as committee members. However, we are wondering if the basis of these reports is scientifically appropriate. For example, there is no established method to evaluate the maximum size of earthquake, whose record is not known, in a specific area, but the committee made an estimate for the Nankai trough by extrapolating available knowledge. The Japanese policy makers further requested the probability of occurrence of such an event, which the committee had to decline because of the lack of knowledge. This example shows that Japanese earthquake scientists sometimes are involved in an important decision-making and are urged to go beyond the limit of earthquake science. We consider this difficult situation is formed on the basis of the history of the Japanese earthquake science and the 'myth of flawless of science' in the government and society, who often ask for a simple answer. Open discussion with people from other fields of science, such as social and human sciences, and the public would be an effective solution for the public to understand the complexity of the problems and to encourage appropriate counter-measures.

  11. Effect of 2008 and 2014 Yutian earthquake on earthquake probabilities to other faults

    NASA Astrophysics Data System (ADS)

    Liu, Boyan

    2015-04-01

    Static stress changes have been proposed to explain variations of seismicity rates, off-fault aftershocks and probability changes for the occurrence of impending earthquakes. Based on the rate-and-state dependent frictional law[1], combined with the seismicity analysis before and after 2008 Yutian earthquake, we have quantitatively calculated the probability of earthquake occurrences nearby, and explained the probable causes of 2014 Yutian earthquake. The probabilities of occurrence a M7.0 earthquake on the eastern segments of Kengxiwar fault, which is the Seismogenic fault of 2014 Yutian earthquake, increases from 3.3% in 2008 to 5.83% in 2014. The probabilities of occurrence a M6.5 and a M6.0 earthquake increase from 23.9% to 38.6% and from 42% to 62.3%, respectively. In addition, we have also computed the earthquake probabilities of southwest and central segments of Gonggacuo fault, and the central segments of Kengxiwar fault, where the Coulomb stress also changed after 2008 Yutian earthquake. The earthquake probabilities of central segments of Gonggacuo and Kengxiwar fault decreased after the 2008 Yutian earthquake, while the earthquake probabilities of southwest segments of Gonggacuo fault increased. After the 2014 Yutian earthquake, the earthquake probabilities of southwest and central segments of Gonggacuo fault increased, but the central segments of Kengxiwar fault decreased. This result indicates that slight variations in Coulomb stress changes can cause the seismic risk changes of the faults nearby. It needs about 500 years that the probabilities of occurrence a M7.0 earthquake exceed to 95% of the three faults we mentioned above. The destructive earthquakes are likely to occur in the southwest segments of Gonggacuo fault, with 26 years and 0.8 years the probabilities of occurrence a M6.5 and a M6.0 earthquake exceed to 95%, respectively. While the seismicity of the central segments of Kengxiwar fault is low; it needs about 87 years and 54 years that the probabilities of occurrence a M6.5 and a M6.0 earthquake exceed to 95% respectively.

  12. Megathrust earthquakes in Central Chile: What is next after the Maule 2010 earthquake?

    NASA Astrophysics Data System (ADS)

    Madariaga, R.

    2013-05-01

    The 27 February 2010 Maule earthquake occurred in a well identified gap in the Chilean subduction zone. The event has now been studied in detail using both far-field, near field seismic and geodetic data, we will review this information gathered so far. The event broke a region that was much longer along strike than the gap left over from the 1835 Concepcion earthquake, sometimes called the Darwin earthquake because he was in the area when the earthquake occurred and made many observations. Recent studies of contemporary documents by Udias et al indicate that the area broken by the Maule earthquake in 2010 had previously broken by a similar earthquake in 1751, but several events in the magnitude 8 range occurred in the area principally in 1835 already mentioned and, more recently on 1 December 1928 to the North and on 21 May 1960 (1 1/2 days before the big Chilean earthquake of 1960). Currently the area of the 2010 earthquake and the region immediately to the North is undergoing a very large increase in seismicity with numerous clusters of seismicity that move along the plate interface. Examination of the seismicity of Chile of the 18th and 19th century show that the region immediately to the North of the 2010 earthquake broke in a very large megathrust event in July 1730. this is the largest known earthquake in central Chile. The region where this event occurred has broken in many occasions with M 8 range earthquakes in 1822, 1880, 1906, 1971 and 1985. Is it preparing for a new very large megathrust event? The 1906 earthquake of Mw 8.3 filled the central part of the gap but it has broken again on several occasions in 1971, 1973 and 1985. The main question is whether the 1906 earthquake relieved enough stresses from the 1730 rupture zone. Geodetic data shows that most of the region that broke in 1730 is currently almost fully locked from the northern end of the Maule earthquake at 34.5S to 30S, near the southern end of the of the Mw 8.5 Atacama earthquake of 11 November 1922. This regions needs special surveillance.

  13. High Precision Relocations of Deep Hawaiian Earthquakes

    NASA Astrophysics Data System (ADS)

    Wolfe, C. J.; Okubo, P. G.; Shearer, P. M.

    2001-12-01

    The abundant earthquakes in Hawaii provide key information on the nature of magmatic and tectonic processes at this oceanic hotspot. Here, we present the results of a project to relocate deep earthquakes (> 14 km) recorded on the United States Geological Survey (USGS) Hawaiian Volcano Observatory (HVO) Network. While many deep earthquakes are believed to reflect pathways of magma movement, the hypocenter distributions suggest additional processes may play a role. We are pursuing two lines of research to obtain a more accurate picture of deep seismicity characteristics. First, both the source specific station term method of Richards-Dinger and Shearer (2000) as well as the double difference method of Waldhauser and Ellsworth (2000) are being applied to relocate earthquakes dating back to 1974 using HVO catalog travel time picks. These methods help remove the biasing effects of velocity heterogeneity and thus improve the relative locations between nearby earthquakes. Second, for specific target areas in space and time, we are measuring accurate differential arrival times using waveform cross-correlation, which can be used to further refine hypocenter locations. At present, we have applied cross-correlation analysis to two areas: 1) a 1994 mb 5.3 30-km deep earthquake and its aftershocks, which occurred slightly south of Kilauea, and 2) all deep earthquakes recorded at HVO in 1997. We find that a significant percentage of aftershocks following the 1994 earthquake are strongly correlated multiplets and that a double difference solution using catalog and cross correlation data yields a horizontal line of seismicity, consistent with a horizontal fault plane. This region has also experienced several previous mL ~4.5 earthquakes, suggesting that a mantle fault has been active over the past few decades. In contrast, only a small percentage of deep earthquakes recorded in 1997 are multiplets that provide correlated waveforms, and we find these multiplets occur in areas scattered beneath the island of Hawaii.

  14. Frog Swarms: Earthquake Precursors or False Alarms?

    PubMed Central

    Grant, Rachel A.; Conlan, Hilary

    2013-01-01

    Simple Summary Media reports linking unusual animal behaviour with earthquakes can potentially create false alarms and unnecessary anxiety among people that live in earthquake risk zones. Recently large frog swarms in China and elsewhere have been reported as earthquake precursors in the media. By examining international media reports of frog swarms since 1850 in comparison to earthquake data, it was concluded that frog swarms are naturally occurring dispersal behaviour of juveniles and are not associated with earthquakes. However, the media in seismic risk areas may be more likely to report frog swarms, and more likely to disseminate reports on frog swarms after earthquakes have occurred, leading to an apparent link between frog swarms and earthquakes. Abstract In short-term earthquake risk forecasting, the avoidance of false alarms is of utmost importance to preclude the possibility of unnecessary panic among populations in seismic hazard areas. Unusual animal behaviour prior to earthquakes has been reported for millennia but has rarely been scientifically documented. Recently large migrations or unusual behaviour of amphibians have been linked to large earthquakes, and media reports of large frog and toad migrations in areas of high seismic risk such as Greece and China have led to fears of a subsequent large earthquake. However, at certain times of year large migrations are part of the normal behavioural repertoire of amphibians. News reports of “frog swarms” from 1850 to the present day were examined for evidence that this behaviour is a precursor to large earthquakes. It was found that only two of 28 reported frog swarms preceded large earthquakes (Sichuan province, China in 2008 and 2010). All of the reported mass migrations of amphibians occurred in late spring, summer and autumn and appeared to relate to small juvenile anurans (frogs and toads). It was concluded that most reported “frog swarms” are actually normal behaviour, probably caused by juvenile animals migrating away from their breeding pond, after a fruitful reproductive season. As amphibian populations undergo large fluctuations in numbers from year to year, this phenomenon will not occur on a yearly basis but will depend on successful reproduction, which is related to numerous climatic and geophysical factors. Hence, most large swarms of amphibians, particularly those involving very small frogs and occurring in late spring or summer, are not unusual and should not be considered earthquake precursors. In addition, it is likely that reports of several mass migration of small toads prior to the Great Sichuan Earthquake in 2008 were not linked to the subsequent M = 7.9 event (some occurred at a great distance from the epicentre), and were probably co-incidence. Statistical analysis of the data indicated frog swarms are unlikely to be connected with earthquakes. Reports of unusual behaviour giving rise to earthquake fears should be interpreted with caution, and consultation with experts in the field of earthquake biology is advised. PMID:26479746

  15. Surface displacements in the 1906 san francisco and 1989 loma prieta earthquakes.

    PubMed

    Segall, P; Lisowski, M

    1990-11-30

    The horizontal displacements accompanying the 1906 San Francisco earthquake and the 1989 Loma Prieta earthquake are computed from geodetic survey measurements. The 1906 earthquake displacement field is entirely consistent with right-lateral strike slip on the San Andreas fault. In contrast, the 1989 Loma Prieta earthquake exhibited subequal components of strike slip and reverse faulting. This result, together with other seismic and geologic data, may indicate that the two earthquakes occurred on two different fault planes. PMID:17829210

  16. Surface displacements in the 1906 San Francisco and 1989 Loma Prieta Earthquakes

    SciTech Connect

    Segall, P. Geological Survey, Menlo Park, CA ); Lisowski, M. )

    1990-11-30

    The horizontal displacements accompanying the 1906 San Francisco earthquake and the 1989 Loma Prieta earthquake are computed from geodetic survey measurements. The 1906 earthquake displacement field is entirely consistent with right-lateral strike slip on the San Andreas fault. In contrast, the 1989 Loma Prieta earthquake exhibited subequal components of strike slip and reverse faulting. This result, together with other seismic and geologic data, may indicate that the two earthquakes occurred on two different fault planes.

  17. Surface displacements in the 1906 San Francisco and 1989 Loma Prieta earthquakes

    USGS Publications Warehouse

    Segall, P.; Lisowski, M.

    1990-01-01

    The horizontal displacements accompanying the 1906 San Francisco earthquake and the 1989 Loma Prieta earthquake are computed from geodetic survey measurements. The 1906 earthquake displacement field is entirely consistent with right-lateral strike slip on the San Andreas fault. In contrast, the 1989 Loma Prieta earthquake exhibited subequal components of strike slip and reverse faulting. This result, together with other seismic and geologic data, may indicate that the two earthquakes occurred on two different fault planes.

  18. Napa Earthquake impact on water systems

    NASA Astrophysics Data System (ADS)

    Wang, J.

    2014-12-01

    South Napa earthquake occurred in Napa, California on August 24 at 3am, local time, and the magnitude is 6.0. The earthquake was the largest in SF Bay Area since the 1989 Loma Prieta earthquake. Economic loss topped $ 1 billion. Wine makers cleaning up and estimated the damage on tourism. Around 15,000 cases of lovely cabernet were pouring into the garden at the Hess Collection. Earthquake potentially raise water pollution risks, could cause water crisis. CA suffered water shortage recent years, and it could be helpful on how to prevent underground/surface water pollution from earthquake. This research gives a clear view on drinking water system in CA, pollution on river systems, as well as estimation on earthquake impact on water supply. The Sacramento-San Joaquin River delta (close to Napa), is the center of the state's water distribution system, delivering fresh water to more than 25 million residents and 3 million acres of farmland. Delta water conveyed through a network of levees is crucial to Southern California. The drought has significantly curtailed water export, and salt water intrusion reduced fresh water outflows. Strong shaking from a nearby earthquake can cause saturated, loose, sandy soils liquefaction, and could potentially damage major delta levee systems near Napa. Napa earthquake is a wake-up call for Southern California. It could potentially damage freshwater supply system.

  19. Predicting the endpoints of earthquake ruptures.

    PubMed

    Wesnousky, Steven G

    2006-11-16

    The active fault traces on which earthquakes occur are generally not continuous, and are commonly composed of segments that are separated by discontinuities that appear as steps in map-view. Stress concentrations resulting from slip at such discontinuities may slow or stop rupture propagation and hence play a controlling role in limiting the length of earthquake rupture. Here I examine the mapped surface rupture traces of 22 historical strike-slip earthquakes with rupture lengths ranging between 10 and 420 km. I show that about two-thirds of the endpoints of strike-slip earthquake ruptures are associated with fault steps or the termini of active fault traces, and that there exists a limiting dimension of fault step (3-4 km) above which earthquake ruptures do not propagate and below which rupture propagation ceases only about 40 per cent of the time. The results are of practical importance to seismic hazard analysis where effort is spent attempting to place limits on the probable length of future earthquakes on mapped active faults. Physical insight to the dynamics of the earthquake rupture process is further gained with the observation that the limiting dimension appears to be largely independent of the earthquake rupture length. It follows that the magnitude of stress changes and the volume affected by those stress changes at the driving edge of laterally propagating ruptures are largely similar and invariable during the rupture process regardless of the distance an event has propagated or will propagate. PMID:17108963

  20. Catalog of significant historical earthquakes in the Central United States

    USGS Publications Warehouse

    Bakun, W.H.; Hopper, M.G.

    2004-01-01

    We use Modified Mercalli intensity assignments to estimate source locations and moment magnitude M for eighteen 19th-century and twenty early- 20th-century earthquakes in the central United States (CUS) for which estimates of M are otherwise not available. We use these estimates, and locations and M estimated elsewhere, to compile a catelog of significant historical earthquakes in the CUS. The 1811-1812 New Madrid earthquakes apparently dominated CUS seismicity in the first two decades of the 19th century. M5-6 earthquakes occurred in the New Madrid Seismic Zone in 1843 and 1878, but none have occurred since 1878. There has been persistent seismic activity in the Illinois Basin in southern Illinois and Indiana, with M > 5.0 earthquakes in 1895, 1909, 1917, 1968, and 1987. Four other M > 5.0 CUS historical earthquakes have occurred: in Kansas in 1867, in Nebraska in 1877, in Oklahoma in 1882, and in Kentucky in 1980.

  1. Stress triggering and the Canterbury earthquake sequence

    NASA Astrophysics Data System (ADS)

    Steacy, Sandy; Jimnez, Abigail; Holden, Caroline

    2014-01-01

    The Canterbury earthquake sequence, which includes the devastating Christchurch event of 2011 February, has to date led to losses of around 40 billion NZ dollars. The location and severity of the earthquakes was a surprise to most inhabitants as the seismic hazard model was dominated by an expected Mw > 8 earthquake on the Alpine fault and an Mw 7.5 earthquake on the Porters Pass fault, 150 and 80 km to the west of Christchurch. The sequence to date has included an Mw = 7.1 earthquake and 3 Mw ? 5.9 events which migrated from west to east. Here we investigate whether the later events are consistent with stress triggering and whether a simple stress map produced shortly after the first earthquake would have accurately indicated the regions where the subsequent activity occurred. We find that 100 per cent of M > 5.5 earthquakes occurred in positive stress areas computed using a slip model for the first event that was available within 10 d of its occurrence. We further find that the stress changes at the starting points of major slip patches of post-Darfield main events are consistent with triggering although this is not always true at the hypocentral locations. Our results suggest that Coulomb stress changes contributed to the evolution of the Canterbury sequence and we note additional areas of increased stress in the Christchurch region and on the Porters Pass fault.

  2. Stress triggering and the Canterbury earthquake sequence

    NASA Astrophysics Data System (ADS)

    Steacy, S.; Jimenez, A.; Francois-Holden, C.

    2013-12-01

    The Canterbury earthquake sequence, which includes the devastating Christchurch event of February 2011, has to date led to losses of around 30 billion NZ dollars. The location and severity of the earthquakes was a surprise to most inhabitants as the seismic hazard model was dominated by an expected M > 8 earthquake on the Alpine fault and an M 7.2-7.3 earthquake on the Porters Pass fault, 150 & 80 km to the west. The sequence to date has included an M = 7.1 earthquake and 3 M ? 6 events which migrated from west to east. Here we investigate whether the later events are consistent with stress triggering and whether a simple stress map produced shortly after the first earthquake would have accurately indicated the regions where the subsequent activity occurred. We find that 100% of M > 5.5 earthquakes occurred in positive stress areas that could have been computed using a slip model for the first event which was available within 10 days of its occurrence. We further find that the stress changes at the starting points of major slip patches of post-Darfield main events are consistent with triggering although this is not always true at the hypocentral locations. Our results suggest that Coulomb stress changes contributed to the evolution of the Canterbury sequence and we note additional areas of increased stress in the Christchurch region and on the Porters Pass fault.

  3. Recurrence Times of Earthquakes in Oaxaca, Mxico

    NASA Astrophysics Data System (ADS)

    Nunez-Cornu, F. J.

    2012-12-01

    Oaxaca is the most seismic active region in Mexico with 68 larger events, (mb > 6.5; Ms> 7.0) from 1542 to 1989, which implies roughly a large earthquake every 6.5 years; including an earthquake with M=8.5 which generate the most important historical tsunami in Mexico. It is also the most studied from a seismic point of view. Three types of earthquakes take place in the region: low angle thrust fault (associated to the subduction process) with a depth between 15 to 25 km; normal fault with a depth between 65 and 120 km with epicenters north of Oaxaca City (17N); normal fault with a depth between 25 to 40 km with epicenters between the coast and Oaxaca City. A seismogenic zoning based in seismic, tectonic and historical seismicity studies zones was proposed in 1989; eight zones were defined, two zone along the coast, one for the isthmus and rest inland. For most of them a characteristic earthquake (from the earthquakes occurred in the previous 61 years) was assigned and several models of recurrence times for the different zones were proposed, in some cases this values ( 94, 80, 68 and 13 years) have a standard deviation error of 20%. 23 Years later, 4 larger earthquake have occurred in the region that seems agreed with the recurrence models proposed. Here the models are revised using the information from the recent earthquakes and new studies in the region

  4. Lawrence Livermore National Laboratory earthquake safety program

    SciTech Connect

    Freeland, G.E.

    1984-08-21

    Within three minutes on the morning of January 24, 1980, an earthquake and three aftershocks, with Richter magnitudes of 5.8, 5.1, 4.0, and 4.2, respectively, struck the Livermore Valley. Two days later, a Richter magnitude 5.4 earthquake occurred, which had its epicenter about 4 miles northwest of the Lawrence Livermore National Laboratory (LLNL). Although no one at the Laboratory was seriously injured, these earthquakes caused considerable damage and disruption. Masonry and concrete structures cracked and broke, trailers shifted and fell off their pedestals, office ceilings and overhead lighting fell, and bookcases overturned. We suddenly found ourselves immersed in a site-wide program of repairing earthquake-damaged facilities, and protecting our many employees and the surrounding community from future earthquakes. Over the past four years, LLNL has spent approximately $10 million on its earthquake restoration effort for repairs and upgrades. The discussion in this paper centers upon the earthquake damage that occurred, our clean-up and restoration efforts, the seismic review of LLNL facilities, our site-specific seismic design criteria, computer-floor upgrades, ceiling-system upgrades, unique building seismic upgrades, geologic and seismologic studies, and seismic instrumentation. 9 references, 37 figures, 2 tables.

  5. THE PERIOD OF LIFE AT WHICH INFECTION FROM TUBERCULOSIS OCCURS MOST FREQUENTLY

    PubMed Central

    Knopf, S. Adolphus

    1916-01-01

    This paper not only contains Doctor Knopf's own valuable conclusions upon the subject presented, but it is also a compendium of the opinions which Doctor Knopf has secured from a number of other eminent physicians. PMID:18009535

  6. Androgen Receptor Variants Occur Frequently in Castration Resistant Prostate Cancer Metastases

    PubMed Central

    Zhang, Xiaotun; Morrissey, Colm; Sun, Shihua; Ketchandji, Melanie; Nelson, Peter S.; True, Lawrence D.; Vakar-Lopez, Funda; Vessella, Robert L.; Plymate, Stephen R.

    2011-01-01

    Background Although androgens are depleted in castration resistant prostate cancer (CRPC), metastases still express nuclear androgen receptor (AR) and androgen regulated genes. We recently reported that C-terminal truncated constitutively active AR splice variants contribute to CRPC development. Since specific antibodies detecting all C-terminal truncated AR variants are not available, our aim was to develop an approach to assess the prevalence and function of AR variants in prostate cancer (PCa). Methodology/Principal Findings Using 2 antibodies against different regions of AR protein (N- or C-terminus), we successfully showed the existence of AR variant in the LuCaP 86.2 xenograft. To evaluate the prevalence of AR variants in human PCa tissue, we used this method on tissue microarrays including 50 primary PCa and 162 metastatic CRPC tissues. RT-PCR was used to confirm AR variants. We observed a significant decrease in nuclear C-terminal AR staining in CRPC but no difference between N- and C-terminal AR nuclear staining in primary PCa. The expression of the AR regulated proteins PSA and PSMA were marginally affected by the decrease in C-terminal staining in CRPC samples. These data suggest that there is an increase in the prevalence of AR variants in CRPC based on our ability to differentiate nuclear AR expression using N- and C-terminal AR antibodies. These findings were validated using RT-PCR. Importantly, the loss of C-terminal immunoreactivity and the identification of AR variants were different depending on the site of metastasis in the same patient. Conclusions We successfully developed a novel immunohistochemical approach which was used to ascertain the prevalence of AR variants in a large number of primary PCa and metastatic CRPC. Our results showed a snapshot of overall high frequency of C-terminal truncated AR splice variants and site specific AR loss in CRPC, which could have utility in stratifying patients for AR targeted therapeutics. PMID:22114732

  7. [Supplementary instrumental examinations in the most frequently occurring peripheral vascular diseases in general practice].

    PubMed

    Partsch, H

    1985-04-01

    Noninvasive investigative methods are valuable for the practical diagnosis of several peripheral vascular disorders. Doppler ultrasound is very useful for the detection of incompetent saphenous and perforating veins and for the measurement of systolic ankle pressure, which today is the best screening method for arterial stenoses or occlusions. Acral oscillography, photoplethysmography and thermography, combined with vasodilator (nitroglycerin) or vasoconstrictor (cold) stress tests, may disclose small vessel disease and vasospastic disorders (Raynaud phenomenon). To answer the question of whether varicosities should be eliminated by surgery or sclerotherapy in patients with severe stages of chronic venous insufficiency (e.g. crural ulcers), investigations of the venous pump by venous pressure measurement or (photo-)plethysmography with and without digital occlusion of the suspected leakage points are recommended. Doppler probe, plethysmography and thermography are valuable screening methods for deep vein thrombosis and help to restrict phlebography to patients on whom fibrinolysis or thrombectomy is carried out. For the majority of patients undergoing conservative treatment, these noninvasive diagnostic procedures are usually sufficient. PMID:3888924

  8. [Evidence-based medicine: a discussion of the most frequently occurring criticisms].

    PubMed

    Hannes, K; Aertgeerts, B; Schepers, R; Goedhuys, J; Buntinx, F

    2005-09-01

    Since the introduction of evidence-based medicine (EBM) into the field of health care in the early nineties some major criticisms have appeared in scientific literature. One of the most commonly heard objections to EBM is loss of therapeutic freedom. However even with the advent of EBM the physician continues to look for solutions that are tailored to the patient. The available evidence is often inadequate, there are many inconsistencies and contradictions in the research material and the published outcomes are distorted by publication bias. There is resistance to the opinion that randomized clinical trials (RCTs) provide the best foundations on which to build clinical policies. There must always be room for views expressed in other types of study. EBM is primarily for academics and does not take clinical expertise into account. However as the results of scientific research are becoming increasingly available to a wider public, patients are able to challenge the decisions made by their health-care practitioners and push them to provide the motivation for their decisions. Many health-care practitioners have commented that they always have to take the results of scientific research into account. One strength of EBM in this is the transparent manner in which the overview of the literature develops and the systematic approach to results from scientific study. After all, there is insufficient evidence that the EBM process works effectively and that it therefore improves patient care. It is true to say that patients who receive treatment of which the efficacy has been proven experience better treatment results than other patients. Setting up a definitive randomized study to answer this question would be difficult if not impossible. EBM is an aid to support clinical decision making. The development of principles on which to base this way of thinking and acting and the quest for suitable research designs and the most objective research results in order to be able to answer all the questions posed by caregivers, is not yet complete. EBM is just one of the weapons in the armoury of the caregiver in the battle for the optimal provision. PMID:16171109

  9. EARTHQUAKES - VOLCANOES (Causes - Forecast - Counteraction)

    NASA Astrophysics Data System (ADS)

    Tsiapas, Elias

    2014-05-01

    Earthquakes and volcanoes are caused by: 1)Various liquid elements (e.g. H20, H2S, S02) which emerge from the pyrosphere and are trapped in the space between the solid crust and the pyrosphere (Moho discontinuity). 2)Protrusions of the solid crust at the Moho discontinuity (mountain range roots, sinking of the lithosphere's plates). 3)The differential movement of crust and pyrosphere. The crust misses one full rotation for approximately every 100 pyrosphere rotations, mostly because of the lunar pull. The above mentioned elements can be found in small quantities all over the Moho discontinuity, and they are constantly causing minor earthquakes and small volcanic eruptions. When large quantities of these elements (H20, H2S, SO2, etc) concentrate, they are carried away by the pyrosphere, moving from west to east under the crust. When this movement takes place under flat surfaces of the solid crust, it does not cause earthquakes. But when these elements come along a protrusion (a mountain root) they concentrate on its western side, displacing the pyrosphere until they fill the space created. Due to the differential movement of pyrosphere and solid crust, a vacuum is created on the eastern side of these protrusions and when the aforementioned liquids overfill this space, they explode, escaping to the east. At the point of their escape, these liquids are vaporized and compressed, their flow accelerates, their temperature rises due to fluid friction and they are ionized. On the Earth's surface, a powerful rumbling sound and electrical discharges in the atmosphere, caused by the movement of the gasses, are noticeable. When these elements escape, the space on the west side of the protrusion is violently taken up by the pyrosphere, which collides with the protrusion, causing a major earthquake, attenuation of the protrusions, cracks on the solid crust and damages to structures on the Earth's surface. It is easy to foresee when an earthquake will occur and how big it is going to be, when we know the record of specific earthquakes and the routes they have followed towards the East. For example, to foresee an earthquake in the Mediterranean region, we take starting point earthquakes to Latin America (0-40).The aforementioned elements will reach Italy in an average time period of 49 days and Greece in 53 days. The most reliable preceding phenomenon to determine the epicenter of an earthquake is the rise of the crust's temperature at the area where a large quantity of elements is concentrated, among other phenomena that can be detected either by instruments or by our senses. When there is an active volcano along the route between the area where the "starting-point" earthquake occurred and the area where we expect the same elements to cause a new earthquake, it is possible these elements will escape through the volcano's crater, carrying lava with them. We could contribute to that end, nullifying earthquakes that might be triggered by these elements further to the east, by using manmade resources, like adequate quantities of explosives at the right moment.

  10. Earthquakes - Volcanoes (Causes - Forecast - Counteraction)

    NASA Astrophysics Data System (ADS)

    Tsiapas, Elias

    2013-04-01

    Earthquakes and volcanoes are caused by: 1)Various liquid elements (e.g. H20, H2S, S02) which emerge from the pyrosphere and are trapped in the space between the solid crust and the pyrosphere (Moho discontinuity). 2)Protrusions of the solid crust at the Moho discontinuity (mountain range roots, sinking of the lithosphere's plates). 3)The differential movement of crust and pyrosphere. The crust misses one full rotation for approximately every 100 pyrosphere rotations, mostly because of the lunar pull. The above mentioned elements can be found in small quantities all over the Moho discontinuity, and they are constantly causing minor earthquakes and small volcanic eruptions. When large quantities of these elements (H20, H2S, SO2, etc) concentrate, they are carried away by the pyrosphere, moving from west to east under the crust. When this movement takes place under flat surfaces of the solid crust, it does not cause earthquakes. But when these elements come along a protrusion (a mountain root) they concentrate on its western side, displacing the pyrosphere until they fill the space created. Due to the differential movement of pyrosphere and solid crust, a vacuum is created on the eastern side of these protrusions and when the aforementioned liquids overfill this space, they explode, escaping to the east. At the point of their escape, these liquids are vaporized and compressed, their flow accelerates, their temperature rises due to fluid friction and they are ionized. On the Earth's surface, a powerful rumbling sound and electrical discharges in the atmosphere, caused by the movement of the gasses, are noticeable. When these elements escape, the space on the west side of the protrusion is violently taken up by the pyrosphere, which collides with the protrusion, causing a major earthquake, attenuation of the protrusions, cracks on the solid crust and damages to structures on the Earth's surface. It is easy to foresee when an earthquake will occur and how big it is going to be, when we know the record of specific earthquakes and the routes they have followed towards the East. For example, to foresee an earthquake in the Mediterranean region, we take starting point earthquakes to Latin America (0-40).The aforementioned elements will reach Italy in an average time period of 49 days and Greece in 53 days. The most reliable preceding phenomenon to determine the epicenter of an earthquake is the rise of the crust's temperature at the area where a large quantity of elements is concentrated, among other phenomena that can be detected either by instruments or by our senses. When there is an active volcano along the route between the area where the "starting-point" earthquake occurred and the area where we expect the same elements to cause a new earthquake, it is possible these elements will escape through the volcano's crater, carrying lava with them. We could contribute to that end, nullifying earthquakes that might be triggered by these elements further to the east, by using manmade resources, like adequate quantities of explosives at the right moment.

  11. Earthquakes - Volcanoes (Causes - Forecast - Counteraction)

    NASA Astrophysics Data System (ADS)

    Tsiapas, Elias

    2015-04-01

    Earthquakes and volcanoes are caused by: 1) Various liquid elements (e.g. H20, H2S, S02) which emerge from the pyrosphere and are trapped in the space between the solid crust and the pyrosphere (Moho discontinuity). 2) Protrusions of the solid crust at the Moho discontinuity (mountain range roots, sinking of the lithosphere's plates). 3) The differential movement of crust and pyrosphere. The crust misses one full rotation for approximately every 100 pyrosphere rotations, mostly because of the lunar pull. The above mentioned elements can be found in small quantities all over the Moho discontinuity, and they are constantly causing minor earthquakes and small volcanic eruptions. When large quantities of these elements (H20, H2S, SO2, etc) concentrate, they are carried away by the pyrosphere, moving from west to east under the crust. When this movement takes place under flat surfaces of the solid crust, it does not cause earthquakes. But when these elements come along a protrusion (a mountain root) they concentrate on its western side, displacing the pyrosphere until they fill the space created. Due to the differential movement of pyrosphere and solid crust, a vacuum is created on the eastern side of these protrusions and when the aforementioned liquids overfill this space, they explode, escaping to the east. At the point of their escape, these liquids are vaporized and compressed, their flow accelerates, their temperature rises due to fluid friction and they are ionized. On the Earth's surface, a powerful rumbling sound and electrical discharges in the atmosphere, caused by the movement of the gasses, are noticeable. When these elements escape, the space on the west side of the protrusion is violently taken up by the pyrosphere, which collides with the protrusion, causing a major earthquake, attenuation of the protrusions, cracks on the solid crust and damages to structures on the Earth's surface. It is easy to foresee when an earthquake will occur and how big it is going to be, when we know the record of specific earthquakes and the routes they have followed towards the East. For example, to foresee an earthquake in the Mediterranean region, we take starting point earthquakes to Latin America (0-40).The aforementioned elements will reach Italy in an average time period of 49 days and Greece in 53 days. The most reliable preceding phenomenon to determine the epicenter of an earthquake is the rise of the crust's temperature at the area where a large quantity of elements is concentrated, among other phenomena that can be detected either by instruments or by our senses. When there is an active volcano along the route between the area where the "starting-point" earthquake occurred and the area where we expect the same elements to cause a new earthquake, it is possible these elements will escape through the volcano's crater, carrying lava with them. We could contribute to that end, nullifying earthquakes that might be triggered by these elements further to the east, by using manmade resources, like adequate quantities of explosives at the right moment.

  12. Multiple asperity model for earthquake prediction

    USGS Publications Warehouse

    Wyss, M.; Johnston, A.C.; Klein, F.W.

    1981-01-01

    Large earthquakes often occur as multiple ruptures reflecting strong variations of stress level along faults. Dense instrument networks with which the volcano Kilauea is monitored provided detailed data on changes of seismic velocity, strain accumulation and earthquake occurrence rate before the 1975 Hawaii 7.2-mag earthquake. During the ???4 yr of preparation time the mainshock source volume had separated into crustal volumes of high stress levels embedded in a larger low-stress volume, showing respectively high- and low-stress precursory anomalies. ?? 1981 Nature Publishing Group.

  13. Streamflow and water well responses to earthquakes.

    PubMed

    Montgomery, David R; Manga, Michael

    2003-06-27

    Earthquake-induced crustal deformation and ground shaking can alter stream flow and water levels in wells through consolidation of surficial deposits, fracturing of solid rocks, aquifer deformation, and the clearing of fracture-filling material. Although local conditions affect the type and amplitude of response, a compilation of reported observations of hydrological response to earthquakes indicates that the maximum distance to which changes in stream flow and water levels in wells have been reported is related to earthquake magnitude. Detectable streamflow changes occur in areas within tens to hundreds of kilometers of the epicenter, whereas changes in groundwater levels in wells can occur hundreds to thousands of kilometers from earthquake epicenters. PMID:12829774

  14. Earthquake source scaling, stress drops and radiated seismic energies of intermediate depth earthquakes

    NASA Astrophysics Data System (ADS)

    Prieto, G.; Lopez, G. A.; Barrett, S. A.; Beroza, G. C.

    2011-12-01

    The physical mechanism for intermediate and deep focus earthquakes is still under debate. The temperatures and pressures are above the point where ordinary fractures ought to occur. Nevertheless these earthquakes represent a significant portion of global catalogs and various mechanisms have been proposed to explain their presence, including dehydration embrittlement and runaway shear instabilities. In order to better understand the rupture mechanism it is important to study earthquake source parameters for these events and their scaling behavior with earthquake size as measured by the seismic moment. In this study we analyze rupture area, stress drop and radiated seismic energy for a range of magnitudes and a large number of earthquakes in the Bucaramanga Nest - a concentrated pocket of seismic activity with median depth of 160 km, with more than 15 earthquakes per day - and compare our results with typical values observed for shallow earthquakes. We study the effect of seismic attenuation and SNR to minimize bias in our estimated source parameters, because the effects of noise and attenuation can lead to lower radiated energy estimates for smaller earthquakes. Preliminary results suggest that the Bucaramanga Nest earthquakes present typical stress drop and apparent stress values, but contrary to their shallow counterparts, they show systematically higher stress drop for larger events.

  15. Earthquake swarms in South America

    NASA Astrophysics Data System (ADS)

    Holtkamp, S. G.; Pritchard, M. E.; Lohman, R. B.

    2011-10-01

    We searched for earthquake swarms in South America between 1973 and 2009 using the global Preliminary Determination of Epicenters (PDE) catalogue. Seismicity rates vary greatly over the South American continent, so we employ a manual search approach that aims to be insensitive to spatial and temporal scales or to the number of earthquakes in a potential swarm. We identify 29 possible swarms involving 5-180 earthquakes each (with total swarm moment magnitudes between 4.7 and 6.9) within a range of tectonic and volcanic locations. Some of the earthquake swarms on the subduction megathrust occur as foreshocks and delineate the limits of main shock rupture propagation for large earthquakes, including the 2010 Mw 8.8 Maule, Chile and 2007 Mw 8.1 Pisco, Peru earthquakes. Also, subduction megathrust swarms commonly occur at the location of subduction of aseismic ridges, including areas of long-standing seismic gaps in Peru and Ecuador. The magnitude-frequency relationship of swarms we observe appears to agree with previously determined magnitude-frequency scaling for swarms in Japan. We examine geodetic data covering five of the swarms to search for an aseismic component. Only two of these swarms (at Copiapó, Chile, in 2006 and near Ticsani Volcano, Peru, in 2005) have suitable satellite-based Interferometric Synthetic Aperture Radar (InSAR) observations. We invert the InSAR geodetic signal and find that the ground deformation associated with these swarms does not require a significant component of aseismic fault slip or magmatic intrusion. Three swarms in the vicinity of the volcanic arc in southern Peru appear to be triggered by the Mw= 8.5 2001 Peru earthquake, but predicted static Coulomb stress changes due to the main shock were very small at the swarm locations, suggesting that dynamic triggering processes may have had a role in their occurrence. Although we identified few swarms in volcanic regions, we suggest that particularly large volcanic swarms (those that could be detected using the PDE catalogue) occur in areas of infrequent eruption and may be related to large regional fault zones.

  16. Recommendations on frequently encountered relief requests

    SciTech Connect

    Hartley, R.S.; Ransom, C.B.

    1992-09-01

    This paper is based on the review of a large database of requests for relief from enservice testing (1ST) requirements for pumps and valves. From the review, the paper identifies areas where enhancements to either the relief request process or the applicable test codes can improve IST of pumps and valves. Certain types of requests occur frequently. The paper examines some frequent requests and considers possible changes to the requirements to determine if the frequent requests can be eliminated. Recommended changes and their bases will be discussed. IST of safety-related pumps and valves at commercial nuclear power plants is done according to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (the Code), Section XI. Because of the design and function of some safety systems in nuclear plants, performing Code testing of certain pumps and valves is impractical or a hardship without a compensating increase in the level of safety. Deviations from the Code are allowed by law, as reviewed and approved by the United States Nuclear Regulatory Commission (NRC), through the relief request process. Because of similarities in plant design and system function, many problems encountered in testing components are similar from plant to plant. Likewise, there are often common problems associated with test methods or equipment. Therefore, many relief requests received by the NRC from various plants are similar. Identifying and addressing the root causes for these common requests will greatly improve IST.

  17. Recommendations on frequently encountered relief requests

    SciTech Connect

    Hartley, R.S.; Ransom, C.B.

    1992-01-01

    This paper is based on the review of a large database of requests for relief from enservice testing (1ST) requirements for pumps and valves. From the review, the paper identifies areas where enhancements to either the relief request process or the applicable test codes can improve IST of pumps and valves. Certain types of requests occur frequently. The paper examines some frequent requests and considers possible changes to the requirements to determine if the frequent requests can be eliminated. Recommended changes and their bases will be discussed. IST of safety-related pumps and valves at commercial nuclear power plants is done according to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (the Code), Section XI. Because of the design and function of some safety systems in nuclear plants, performing Code testing of certain pumps and valves is impractical or a hardship without a compensating increase in the level of safety. Deviations from the Code are allowed by law, as reviewed and approved by the United States Nuclear Regulatory Commission (NRC), through the relief request process. Because of similarities in plant design and system function, many problems encountered in testing components are similar from plant to plant. Likewise, there are often common problems associated with test methods or equipment. Therefore, many relief requests received by the NRC from various plants are similar. Identifying and addressing the root causes for these common requests will greatly improve IST.

  18. Research on earthquake prediction from infrared cloud images

    NASA Astrophysics Data System (ADS)

    Fan, Jing; Chen, Zhong; Yan, Liang; Gong, Jing; Wang, Dong

    2015-12-01

    In recent years, the occurrence of large earthquakes is frequent all over the word. In the face of the inevitable natural disasters, the prediction of the earthquake is particularly important to avoid more loss of life and property. Many achievements in the field of predict earthquake from remote sensing images have been obtained in the last few decades. But the traditional prediction methods presented do have the limitations of can't forecast epicenter location accurately and automatically. In order to solve the problem, a new predicting earthquakes method based on extract the texture and emergence frequency of the earthquake cloud is proposed in this paper. First, strengthen the infrared cloud images. Second, extract the texture feature vector of each pixel. Then, classified those pixels and converted to several small suspected area. Finally, tracking the suspected area and estimate the possible location. The inversion experiment of Ludian earthquake show that this approach can forecast the seismic center feasible and accurately.

  19. In search of earthquake-related hydrologic and chemical changes along Hayward Fault

    USGS Publications Warehouse

    King, C.-Y.; Basler, D.; Presser, T.S.; Evans, William C.; White, L.D.; Minissale, A.

    1994-01-01

    Flow and chemical measurements have been made about once a month, and more frequently when required, since 1976 at two springs in Alum Rock Park in eastern San Jose, California, and since 1980 at two shallow wells in eastern Oakland in search of earthquake-related changes. All sites are on or near the Hayward Fault and are about 55 km apart. Temperature, electric conductivity, and water level or flow rate were measured in situ with portable instruments. Water samples were collected for later chemical and isotopic analyses in the laboratory. The measured flow rate at one of the springs showed a long-term decrease of about 40% since 1987, when a multi-year drought began in California. It also showed several increases that lasted a few days to a few months with amplitudes of 2.4 to 8.6 times the standard deviations above the background rate. Five of these increases were recorded shortly after nearby earthquakes of magnitude 5.0 or larger, and may have resulted from unclogging of the flow path and increase of permeability caused by strong seismic shaking. Two other flow increases were possibly induced by exceptionally heavy rainfalls. The water in both wells showed seasonal temperature and chemical variations, largely in response to rainfall. In 1980 the water also showed some clear chemical changes unrelated to rainfall that lasted a few months; these changes were followed by a magnitude 4 earthquake 37 km away. The chemical composition at one of the wells and at the springs also showed some longer-term variations that were not correlated with rainfall but possibly correlated with the five earthquakes mentioned above. These correlations suggest a common tectonic origin for the earthquakes and the anomalies. The last variation at the affected well occurred abruptly in 1989, shortly before a magnitude 5.0 earthquake 54 km away. ?? 1993.

  20. The Cascadia Subduction Zone and related subduction systems: seismic structure, intraslab earthquakes and processes, and earthquake hazards

    USGS Publications Warehouse

    Kirby, Stephen H.; Wang, Kelin; Dunlop, Susan

    2002-01-01

    The following report is the principal product of an international workshop titled “Intraslab Earthquakes in the Cascadia Subduction System: Science and Hazards” and was sponsored by the U.S. Geological Survey, the Geological Survey of Canada and the University of Victoria. This meeting was held at the University of Victoria’s Dunsmuir Lodge, Vancouver Island, British Columbia, Canada on September 18–21, 2000 and brought 46 participants from the U.S., Canada, Latin America and Japan. This gathering was organized to bring together active research investigators in the science of subduction and intraslab earthquake hazards. Special emphasis was given to “warm-slab” subduction systems, i.e., those systems involving young oceanic lithosphere subducting at moderate to slow rates, such as the Cascadia system in the U.S. and Canada, and the Nankai system in Japan. All the speakers and poster presenters provided abstracts of their presentations that were a made available in an abstract volume at the workshop. Most of the authors subsequently provided full articles or extended abstracts for this volume on the topics that they discussed at the workshop. Where updated versions were not provided, the original workshop abstracts have been included. By organizing this workshop and assembling this volume, our aim is to provide a global perspective on the science of warm-slab subduction, to thereby advance our understanding of internal slab processes and to use this understanding to improve appraisals of the hazards associated with large intraslab earthquakes in the Cascadia system. These events have been the most frequent and damaging earthquakes in western Washington State over the last century. As if to underscore this fact, just six months after this workshop was held, the magnitude 6.8 Nisqually earthquake occurred on February 28th, 2001 at a depth of about 55 km in the Juan de Fuca slab beneath the southern Puget Sound region of western Washington. The Governor’s Office of the State of Washington estimated damage at more than US$2 billion, making it among the costliest earthquakes in U.S. history.

  1. Evidence of cumulative offset along the inland Itozawa fault possibly triggered by the past M9 Tohoku, Japan, megathrust earthquakes revealed from a borehole survey

    NASA Astrophysics Data System (ADS)

    Niwa, Y.; Toda, S.; Omata, M.; Mori, Y.

    2013-12-01

    The gigantic Mw 9.0 11 March 2011 Tohoku earthquake suddenly changed the overriding inland area from a compressional stress to an extensional stress regime and then triggered massive seismic swarms in the coastal Fukushima region. The Fukushima-ken-hamadori earthquake on 11 April 2011 (hereinafter, Iwaki earthquake), which was the largest inland off-fault aftershock of the Tohoku earthquake, ruptured the two previously mapped normal faults, the Yunodake fault and the Itozawa fault (Toda and Tsutsumi, BSSA, 2013). The Iwaki earthquake implies that the past gigantic megathrust earthquakes, if they exist, might have frequently triggered slip on similar normal faults including the Itozawa and Yunodake faults themselves. Ideally, collecting all the paleoseismic records from all the normal faults would give us the history of the past M9 class megathrust events and an average inter-event time. Among the series of surveys including paleoseismic trenches (e.g., Toda and Tsutsumi, 2013), we conducted a borehole survey across the central part of the Itozawa fault (Shionohira, Iwaki City), where the maximum vertical displacement 2.1 m was measured. In both upthrown and downthrown sides, extracted core samples expose bedrock conglomerate, fluvial sand and gravel deposits, and artificial fill, from lower to upper, in ascending order. Only in downthrown side, an organic-rich fine layer overlays fluvial deposit, indicating environmental changes from river channel to marsh or pond. We found evidence for cumulative vertical displacement on the top of pre-2011 artificial fill (1.7 m), river channel gravel layer (2.5 m), and bedrock (3.4 m). On the basis of sudden environmental changes from river to pond observed after the Iwaki earthquake due to subsided upstream area (Toda and Tsutsumi, 2013), we interpret that change in sedimentary facies from fluvial gravel to marsh or pond organic layer in the downthrown side corresponds to one of the past surface-rupturing earthquakes. Radiocarbon age yielded from the organic-rich unit suggests that one of the pre-2011 surface rupturing earthquakes occurred about 50,000 years ago. The amount of vertical displacement at one of the pre-2011 earthquakes (ca. 0.8 m) is significantly smaller than displacement at the Iwaki earthquake. Together with large coseismic slip at the 2011 event, it implies that the characteristic earthquake model cannot be simply applied to the faults largely influenced or directly triggered by huge megathrust earthquakes nearby.

  2. Assessing Earthquake Risks in the Pacific Northwest

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2014-10-01

    Megaquakes, which are subduction earthquakes with magnitudes of 8 or greater, occur about every 500 years on average along the Cascadia Subduction Zone in the Pacific Northwest. The earthquakes and related tsunamis can cause enormous damage. However, they may not be the most urgent seismic threat in the region, according to John Clague, a professor and expert on natural hazards at Simon Fraser University (SFU) in British Columbia.

  3. Earthquakes for Kids

    MedlinePLUS

    ... Education FAQ Earthquake Glossary For Kids Prepare Google Earth/KML Files Earthquake Summary Posters Photos Publications Share ... for Education FAQ EQ Glossary For Kids Google Earth/KML Files EQ Summary Posters Photos Publications Monitoring ...

  4. Earthquakes: hydrogeochemical precursors

    USGS Publications Warehouse

    Ingebritsen, Steven E.; Manga, Michael

    2014-01-01

    Earthquake prediction is a long-sought goal. Changes in groundwater chemistry before earthquakes in Iceland highlight a potential hydrogeochemical precursor, but such signals must be evaluated in the context of long-term, multiparametric data sets.

  5. Speeding earthquake disaster relief

    USGS Publications Warehouse

    Mortensen, Carl; Donlin, Carolyn; Page, Robert A.; Ward, Peter

    1995-01-01

    In coping with recent multibillion-dollar earthquake disasters, scientists and emergency managers have found new ways to speed and improve relief efforts. This progress is founded on the rapid availability of earthquake information from seismograph networks.

  6. Source processes of the 1949 Olympia, Washington and other Cascadia intraslab earthquakes

    NASA Astrophysics Data System (ADS)

    Ichinose, G. A.; Somerville, P. G.; Thio, H.

    2004-12-01

    Cascadia intraslab earthquakes have occurred frequently including in 1949 (M 7), 1965 (M 6.9), and 2001 (Mw 6.8) and the hazard they pose is equal to other seismic sources for time scales relevant to retrofitting (50%PE in 75 yrs). Reexamination of historical earthquakes and analysis of broadband seismograms from new earthquakes improves strong motion prediction more than stochastic scenarios and provides a better understanding in how stress is released in the subducting slab relative to external tectonic forces and local dehydration. Reanalysis of the 1949 Olympia earthquake using digitized seismograms collected by Barker and Langston [1987], Wiest et al. [2004], long-period WWSSN data from College, Alaska, Bogot, Columbia, and Pasadena, California, has yielded a normal-slip mechanism that fits all the available data with E-W extensional-axis. This mechanism better resembles those from previous Puget Sound intraslab earthquakes. The earthquake ruptured southward along a plane with 170\\deg strike and 70\\deg dip. The hypocenter depth is 60 km with a total Mo of 1.9\\times1026 dyne-cm (Mw 6.78). We inverted teleseismic body waves to determine the mechanism and rupture pattern in space and time using a time-domain iterative inversion process. We limited the number of unknowns by assuming only 2 subevents and performed a grid search on the remaining variables including hypocenter depth, rupture direction, subevent rise time and rupture velocity. A rise time of 3 s best fits the frequency content of the waveforms but there is no resolution of rupture velocity with this dataset so we assume 3.5 km/s. The total moment is typically lower because of stricter model assumptions and the use of band limited data. The amplitudes from the Pasadena 1-90 s Benioff records indicate a higher Mw 6.8 when compared to those from the 2001 Nisqually earthquake convolved with a similar response. We show from similar analyses of this and other intraslab earthquakes that they have significantly smaller asperity areas relative to other types of earthquakes with the same seismic moment originally identified by Asano et al. [2003] and Ichinose et al. [2004].

  7. Combined GPS and InSAR models of postseismic deformation from the Northridge Earthquake

    NASA Technical Reports Server (NTRS)

    Donnellan, A.; Parker, J. W.; Peltzer, G.

    2002-01-01

    Models of combined Global Positioning System and Interferometric Synthetic Aperture Radar data collected in the region of the Northridge earthquake indicate that significant afterslip on the main fault occurred following the earthquake.

  8. Possible seasonality in large deep-focus earthquakes

    NASA Astrophysics Data System (ADS)

    Zhan, Zhongwen; Shearer, Peter M.

    2015-09-01

    Large deep-focus earthquakes (magnitude > 7.0, depth > 500 km) have exhibited strong seasonality in their occurrence times since the beginning of global earthquake catalogs. Of 60 such events from 1900 to the present, 42 have occurred in the middle half of each year. The seasonality appears strongest in the northwest Pacific subduction zones and weakest in the Tonga region. Taken at face value, the surplus of northern hemisphere summer events is statistically significant, but due to the ex post facto hypothesis testing, the absence of seasonality in smaller deep earthquakes, and the lack of a known physical triggering mechanism, we cannot rule out that the observed seasonality is just random chance. However, we can make a testable prediction of seasonality in future large deep-focus earthquakes, which, given likely earthquake occurrence rates, should be verified or falsified within a few decades. If confirmed, deep earthquake seasonality would challenge our current understanding of deep earthquakes.

  9. Remote monitoring of the earthquake cycle using satellite radar interferometry

    NASA Astrophysics Data System (ADS)

    Wright, Tim J.

    2002-12-01

    The earthquake cycle is poorly understood. Earthquakes continue to occur on previously unrecognized faults. Earthquake prediction seems impossible. These remain the facts despite nearly 100 years of intensive study since the earthquake cycle was first conceptualized. Using data acquired from satellites in orbit 800 km above the Earth, a new technique, radar interferometry (InSAR), has the potential to solve these problems. For the first time, detailed maps of the warping of the Earth's surface during the earthquake cycle can be obtained with a spatial resolution of a few tens of metres and a precision of a few millimetres. InSAR does not need equipment on the ground or expensive field campaigns, so it can gather crucial data on earthquakes and the seismic cycle from some of the remotest areas of the planet. In this article, I review some of the remarkable observations of the earthquake cycle already made using radar interferometry and speculate on breakthroughs that are tantalizingly close.

  10. Real-time earthquake monitoring using a search engine method

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Zhang, Haijiang; Chen, Enhong; Zheng, Yi; Kuang, Wenhuan; Zhang, Xiong

    2014-12-01

    When an earthquake occurs, seismologists want to use recorded seismograms to infer its location, magnitude and source-focal mechanism as quickly as possible. If such information could be determined immediately, timely evacuations and emergency actions could be undertaken to mitigate earthquake damage. Current advanced methods can report the initial location and magnitude of an earthquake within a few seconds, but estimating the source-focal mechanism may require minutes to hours. Here we present an earthquake search engine, similar to a web search engine, that we developed by applying a computer fast search method to a large seismogram database to find waveforms that best fit the input data. Our method is several thousand times faster than an exact search. For an Mw 5.9 earthquake on 8 March 2012 in Xinjiang, China, the search engine can infer the earthquakes parameters in <1?s after receiving the long-period surface wave data.

  11. Oceanic earthquakes and the tectonic evolution of oceanic lithosphere

    NASA Technical Reports Server (NTRS)

    Solomon, Sean C.

    1988-01-01

    The body waveform inversion method of Nabelek (1984) is used to study the centroid depths and source properties of oceanic earthquakes. The source parameters for 50 earthquakes which occurred along slowly spreading midocean ridges between 1962 and 1983 are used to examine the mechanical characteristics of the median valley, including the water depth in the epicentral region, the depth range of seismic faulting, the centroid depth and seismic moment versus spreading rate, and the seismic moment budget. The locations and source characteristics of oceanic intraplate earthquakes are discussed, including near-ridge earthquakes, lithospheric stress, and earthquakes in older oceanic lithosphere. The results suggest that the median valley form by the necking of a strong layer. The properties of near-ridge earthquakes support the hypothesis that thermal stress generated by diferential cooling of the plate can be stored and accumulated over millions of years. Earthquakes in older oceanic lithosphere are most likely to reflect stresses generated by plate driving forces.

  12. A Decade of Giant Earthquakes - What does it mean?

    SciTech Connect

    Wallace, Terry C. Jr.

    2012-07-16

    On December 26, 2004 the largest earthquake since 1964 occurred near Ache, Indonesia. The magnitude 9.2 earthquake and subsequent tsunami killed a quarter of million people; it also marked the being of a period of extraordinary seismicity. Since the Ache earthquake there have been 16 magnitude 8 earthquakes globally, including 2 this last April. For the 100 years previous to 2004 there was an average of 1 magnitude 8 earthquake every 2.2 years; since 2004 there has been 2 per year. Since magnitude 8 earthquakes dominate global seismic energy release, this period of seismicity has seismologist rethinking what they understand about plate tectonics and the connectivity between giant earthquakes. This talk will explore this remarkable period of time and its possible implications.

  13. Automatic Recognition of Seismic Intensity Based on RS and GIS: A Case Study in Wenchuan Ms8.0 Earthquake of China

    PubMed Central

    Zhang, Yan; Su, Bin

    2014-01-01

    In recent years, earthquakes have frequently occurred all over the world, which caused huge casualties and economic losses. It is very necessary and urgent to obtain the seismic intensity map timely so as to master the distribution of the disaster and provide supports for quick earthquake relief. Compared with traditional methods of drawing seismic intensity map, which require many investigations in the field of earthquake area or are too dependent on the empirical formulas, spatial information technologies such as Remote Sensing (RS) and Geographical Information System (GIS) can provide fast and economical way to automatically recognize the seismic intensity. With the integrated application of RS and GIS, this paper proposes a RS/GIS-based approach for automatic recognition of seismic intensity, in which RS is used to retrieve and extract the information on damages caused by earthquake, and GIS is applied to manage and display the data of seismic intensity. The case study in Wenchuan Ms8.0 earthquake in China shows that the information on seismic intensity can be automatically extracted from remotely sensed images as quickly as possible after earthquake occurrence, and the Digital Intensity Model (DIM) can be used to visually query and display the distribution of seismic intensity. PMID:24688445

  14. Automatic recognition of seismic intensity based on RS and GIS: a case study in Wenchuan Ms8.0 earthquake of China.

    PubMed

    Zhang, Qiuwen; Zhang, Yan; Yang, Xiaohong; Su, Bin

    2014-01-01

    In recent years, earthquakes have frequently occurred all over the world, which caused huge casualties and economic losses. It is very necessary and urgent to obtain the seismic intensity map timely so as to master the distribution of the disaster and provide supports for quick earthquake relief. Compared with traditional methods of drawing seismic intensity map, which require many investigations in the field of earthquake area or are too dependent on the empirical formulas, spatial information technologies such as Remote Sensing (RS) and Geographical Information System (GIS) can provide fast and economical way to automatically recognize the seismic intensity. With the integrated application of RS and GIS, this paper proposes a RS/GIS-based approach for automatic recognition of seismic intensity, in which RS is used to retrieve and extract the information on damages caused by earthquake, and GIS is applied to manage and display the data of seismic intensity. The case study in Wenchuan Ms8.0 earthquake in China shows that the information on seismic intensity can be automatically extracted from remotely sensed images as quickly as possible after earthquake occurrence, and the Digital Intensity Model (DIM) can be used to visually query and display the distribution of seismic intensity. PMID:24688445

  15. Active tectonics and earthquake sources in the epicentral area of the 1857 Basilicata earthquake (southern Italy)

    NASA Astrophysics Data System (ADS)

    Cello, G.; Tondi, E.; Micarelli, L.; Mattioni, L.

    2003-09-01

    The 1857 Basilicata earthquake (Imax=XI MCS; Me=6.9) is one of the most destructive events that occurred in peninsular Italy; shaking effects and ground breaks were recorded over a large area extending from the Vallo di Diano (Campania) to the Val d'Agri (Basilicata) for a length of about 60 km and with a width of more than 10 km. Within this seismogenic belt, only another strong earthquake, with maximum intensities in the range of X MCS (Me=6.4), occurred in 1561. In the epicentral area of the 1857 earthquake, two regional fault systems (i.e. the Val d'Agri and the Vallo di Diano fault systems) offset the main features of the southern Apennines fold and thrust belt; both systems show evidence of activity during Pleistocene times. The Vallo di Diano Fault System (DIFS) includes mostly NW-SE and WNW-ESE trending faults displaying long-term displacements of a few hundred meters; slip data from the latter faults record a kinematic transition from almost pure normal motion to dextral/oblique motion, whereas the NW-SE oriented faults are mostly dominated by normal/transtensional (sinistral) motion. The Val d'Agri Fault System (VAFS) is characterized by fault zones of different size; it is a kinematically coherent system including roughly N120 trending left-lateral strike-slip faults and N090-N100 trending left-lateral transtensional faults. Inversion of fault slip data indicates that the stress field conditions responsible for the genesis and evolution of the two fault systems are quite different, with ?1 being: (1) sub-horizontal and WSW-ENE trending, in the case of the VAFS, and (2) sub-vertical, in the case of the DIFS. However, the two fault systems are characterized by a roughly N-S oriented extension, and by R-values indicating that ?1? ?2>> ?3. This suggests the possibility that, in these areas, permutations between the principal maximum and intermediate axes of the stress ellipsoid may have frequently occurred during the faulting process. In this paper, we present new data for both the VAFS and DIFS and discuss the inferred modes of interaction between the two fault systems; this, in turn, suggests possible implications for seismic hazard analyses (SHA) in this sector of the southern Apennines.

  16. Land subsidence of clay deposits after the Tohoku-Pacific Ocean Earthquake

    NASA Astrophysics Data System (ADS)

    Yasuhara, K.; Kazama, M.

    2015-11-01

    Extensive infrastructure collapse resulted from the cataclysmic earthquake that struck off the eastern coast of Japan on 11 March 2011 and from its consequent gigantic tsunami, affecting not only the Tohoku region but also the Kanto region. Among the geological and geotechnical processes observed, land subsidence occurring in both coastal and inland areas and from Tohoku to Kanto is an extremely important issue that must be examined carefully. This land subsidence is classifiable into three categories: (i) land sinking along the coastal areas because of tectonic movements, (ii) settlement of sandy deposits followed by liquefaction, and (iii) long-term post-earthquake recompression settlement in soft clay caused by dissipation of excess pore pressure. This paper describes two case histories of post-earthquake settlement of clay deposits from among the three categories of ground sinking and land subsidence because such settlement has been frequently overlooked in numerous earlier earthquakes. Particularly, an attempt is made to propose a methodology for predicting such settlement and for formulating remedial or responsive measures to mitigate damage from such settlement.

  17. Redefining Earthquakes and the Earthquake Machine

    ERIC Educational Resources Information Center

    Hubenthal, Michael; Braile, Larry; Taber, John

    2008-01-01

    The Earthquake Machine (EML), a mechanical model of stick-slip fault systems, can increase student engagement and facilitate opportunities to participate in the scientific process. This article introduces the EML model and an activity that challenges ninth-grade students' misconceptions about earthquakes. The activity emphasizes the role of models

  18. Redefining Earthquakes and the Earthquake Machine

    ERIC Educational Resources Information Center

    Hubenthal, Michael; Braile, Larry; Taber, John

    2008-01-01

    The Earthquake Machine (EML), a mechanical model of stick-slip fault systems, can increase student engagement and facilitate opportunities to participate in the scientific process. This article introduces the EML model and an activity that challenges ninth-grade students' misconceptions about earthquakes. The activity emphasizes the role of models…

  19. Does Geothermal Energy Production Cause Earthquakes in the Geysers Region of Northern California?

    NASA Astrophysics Data System (ADS)

    Grove, K.; Bailey, C.; Sotto, M.; Yu, M.; Cohen, M.

    2003-12-01

    The Geysers region is located in Sonoma County, several hours north of San Francisco. At this location, hot magma beneath the surface heats ground water and creates steam that is used to make electricity. Since 1997, 8 billion gallons of treated wastewater have been injected into the ground, where the water becomes hot and increases the amount of thermal energy that can be produced. Frequent micro-earthquakes (up to magnitude 4.5) occur in the region and seem to be related to the geothermal energy production. The region is mostly uninhabited, except for several small towns such as Anderson Springs, where people have been extremely concerned about potential damage to their property. The energy companies are planning to double the amount of wastewater injected into the ground and to increase their energy production. Geothermal energy is important because it is better for the environment than burning coal, oil, or gas. Air and water pollution, which have negative impacts on living things, are reduced compared to power plants that generate electricity by burning fossil fuels. We have studied the frequency and magnitude of earthquakes that have occurred in the region since the early 1970s and that are occurring today. We used software to analyze the earthquakes and to look for patterns related to water injection and energy production. We are interested in exploring ways that energy production can be continued without having negative impacts on the people in the region.

  20. New earthquake catalog reexamines Hawaii's seismic history

    USGS Publications Warehouse

    Wright, Thomas L.; Klein, Fred W.

    2000-01-01

    On April 2,1868, an earthquake of magnitude 7.9 occurred beneath the southern part of the island of Hawaii. The quake, which was felt throughout all of the Hawaiian Islands, had a Modified Mercalli (MM) intensity of XII near its source.The destruction caused by a quake that large is nearly complete. A landslide triggered by the quake buried a small village, killing 31 people, and a tsunami that swept over coastal settlements added to the death toll. We know as much as we do about this and other early earthquakes thanks to detailed records kept by Hawaiian missionaries, including the remarkable diary maintained by the Lyman family that documented every earthquake felt at their home in Hilo between 1833 and 1917 [Wyss et al., 1992].Our analysis of these and other historical records indicates that Hawaii was at least as intensely seismic in the 19th century and first half of the 20th century as in its more recent past, with 26 M ?6.0 earthquakes occurring from 1823 to 1903 and 20 M ?6.0 earthquakes from 1904 to 1959. Just five M ?6.0 earthquakes occurred from 1960 to 1999. The potential damage caused by a repeat of some of the larger historic events could be catastrophic today.

  1. Earthquake Prognosis With Applied Microseism.

    NASA Astrophysics Data System (ADS)

    Ahmedov, N.; Nagiyev, A.

    Earthquakes are the most dangerous natural catastrophy in terms of numerous casualties, amount of damages, areal coverage and difficulties associated with a need to provide secure measures. Inability to forecast these events makes the situation worse due to the following circumstances:-their buried focuses are invisible in the subsurface, they occur suddenly as a thunder, and some tens of the seconds later they leave devastated areas and casualties of tens of thousands of people. Currently earthquake forecausting is actually absolutely inefficient. Microseism application is one of the possible ways to forecast earthquakes. These small oscillation of up-going low-ampitude, irregular wawes observed on seismograms are refered to as microseism. Having been different from earhquakes itself, they are continuous, that is, have no origin coordinate on time axis. Their occurence is associated with breakers observed along shorelines, strong wind and hurricane patterns and so on. J.J.Linch has discovered a new tool to monitor hurricane motion trend over the seas with applied microseism recorded at ad hocstations. Similar to these observations it became possible to monitor the formation of the earthquake focuses based on correlation between low-frequency horizontal ahannels'N-S and E-W components. Microseism field and preceding abnormal variations monitoring data derived from "Cherepaha" 3M and 6/12 device enable to draw out some systematic trend in amplitude/frecuency domain. This relationship observed in a certain frequency range made it possible to define the generation of earthquake focuses with regard to the monitoring station. This variation trend was observed while Turkish and Iranian events happened during 1990,1992, and 1997. It is suggested to be useful to verify these effects in other regions to further correlate available data and work out common forecausting criteria.

  2. Real Earthquakes, Real Learning

    ERIC Educational Resources Information Center

    Schomburg, Aaron

    2003-01-01

    One teacher took her class on a year long earthquake expedition. The goal was to monitor the occurrences of real earthquakes during the year and mark their locations with push pins on a wall-sized world map in the hallway outside the science room. The purpose of the project was to create a detailed picture of the earthquakes that occurred…

  3. Earthquake and Schools. [Videotape].

    ERIC Educational Resources Information Center

    Federal Emergency Management Agency, Washington, DC.

    Designing schools to make them more earthquake resistant and protect children from the catastrophic collapse of the school building is discussed in this videotape. It reveals that 44 of the 50 U.S. states are vulnerable to earthquake, but most schools are structurally unprepared to take on the stresses that earthquakes exert. The cost to the

  4. Children's Ideas about Earthquakes

    ERIC Educational Resources Information Center

    Simsek, Canan Lacin

    2007-01-01

    Earthquake, a natural disaster, is among the fundamental problems of many countries. If people know how to protect themselves from earthquake and arrange their life styles in compliance with this, damage they will suffer will reduce to that extent. In particular, a good training regarding earthquake to be received in primary schools is considered…

  5. Frequently Asked Questions about Rotavirus

    MedlinePLUS

    ... outbreaks can occur in childcare centers, playgroups, and hospitals. » Back to top Can I keep my child from being exposed to rotavirus? It is difficult to keep a child from being exposed to rotavirus. Better hygiene and sanitation have not been very good at ...

  6. Probing failure susceptibilities of earthquake faults using small-quake tidal correlations.

    PubMed

    Brinkman, Braden A W; LeBlanc, Michael; Ben-Zion, Yehuda; Uhl, Jonathan T; Dahmen, Karin A

    2015-01-01

    Mitigating the devastating economic and humanitarian impact of large earthquakes requires signals for forecasting seismic events. Daily tide stresses were previously thought to be insufficient for use as such a signal. Recently, however, they have been found to correlate significantly with small earthquakes, just before large earthquakes occur. Here we present a simple earthquake model to investigate whether correlations between daily tidal stresses and small earthquakes provide information about the likelihood of impending large earthquakes. The model predicts that intervals of significant correlations between small earthquakes and ongoing low-amplitude periodic stresses indicate increased fault susceptibility to large earthquake generation. The results agree with the recent observations of large earthquakes preceded by time periods of significant correlations between smaller events and daily tide stresses. We anticipate that incorporating experimentally determined parameters and fault-specific details into the model may provide new tools for extracting improved probabilities of impending large earthquakes. PMID:25625338

  7. Operational earthquake forecasting can enhance earthquake preparedness

    USGS Publications Warehouse

    Jordan, T.H.; Marzocchi, W.; Michael, A.J.; Gerstenberger, M.C.

    2014-01-01

    We cannot yet predict large earthquakes in the short term with much reliability and skill, but the strong clustering exhibited in seismic sequences tells us that earthquake probabilities are not constant in time; they generally rise and fall over periods of days to years in correlation with nearby seismic activity. Operational earthquake forecasting (OEF) is the dissemination of authoritative information about these time?dependent probabilities to help communities prepare for potentially destructive earthquakes. The goal of OEF is to inform the decisions that people and organizations must continually make to mitigate seismic risk and prepare for potentially destructive earthquakes on time scales from days to decades. To fulfill this role, OEF must provide a complete description of the seismic hazardground?motion exceedance probabilities as well as short?term rupture probabilitiesin concert with the long?term forecasts of probabilistic seismic?hazard analysis (PSHA).

  8. Earthquake location in island arcs

    USGS Publications Warehouse

    Engdahl, E.R.; Dewey, J.W.; Fujita, K.

    1982-01-01

    A comprehensive data set of selected teleseismic P-wave arrivals and local-network P- and S-wave arrivals from large earthquakes occurring at all depths within a small section of the central Aleutians is used to examine the general problem of earthquake location in island arcs. Reference hypocenters for this special data set are determined for shallow earthquakes from local-network data and for deep earthquakes from combined local and teleseismic data by joint inversion for structure and location. The high-velocity lithospheric slab beneath the central Aleutians may displace hypocenters that are located using spherically symmetric Earth models; the amount of displacement depends on the position of the earthquakes with respect to the slab and on whether local or teleseismic data are used to locate the earthquakes. Hypocenters for trench and intermediate-depth events appear to be minimally biased by the effects of slab structure on rays to teleseismic stations. However, locations of intermediate-depth events based on only local data are systematically displaced southwards, the magnitude of the displacement being proportional to depth. Shallow-focus events along the main thrust zone, although well located using only local-network data, are severely shifted northwards and deeper, with displacements as large as 50 km, by slab effects on teleseismic travel times. Hypocenters determined by a method that utilizes seismic ray tracing through a three-dimensional velocity model of the subduction zone, derived by thermal modeling, are compared to results obtained by the method of joint hypocenter determination (JHD) that formally assumes a laterally homogeneous velocity model over the source region and treats all raypath anomalies as constant station corrections to the travel-time curve. The ray-tracing method has the theoretical advantage that it accounts for variations in travel-time anomalies within a group of events distributed over a sizable region of a dipping, high-velocity lithospheric slab. In application, JHD has the practical advantage that it does not require the specification of a theoretical velocity model for the slab. Considering earthquakes within a 260 km long by 60 km wide section of the Aleutian main thrust zone, our results suggest that the theoretical velocity structure of the slab is presently not sufficiently well known that accurate locations can be obtained independently of locally recorded data. Using a locally recorded earthquake as a calibration event, JHD gave excellent results over the entire section of the main thrust zone here studied, without showing a strong effect that might be attributed to spatially varying source-station anomalies. We also calibrated the ray-tracing method using locally recorded data and obtained results generally similar to those obtained by JHD. ?? 1982.

  9. Seismic evidence for thermal runaway during intermediate-depth earthquake rupture

    NASA Astrophysics Data System (ADS)

    Prieto, Germn. A.; Florez, Manuel; Barrett, Sarah A.; Beroza, Gregory C.; Pedraza, Patricia; Blanco, Jose Faustino; Poveda, Esteban

    2013-12-01

    earthquakes occur at depths where temperatures and pressures exceed those at which brittle failure is expected. There are two leading candidates for the physical mechanism behind these earthquakes: dehydration embrittlement and self-localizing thermal shear runaway. A complete energy budget for a range of earthquake sizes can help constrain whether either of these mechanisms might play a role in intermediate-depth earthquake rupture. The combination of high stress drop and low radiation efficiency that we observe for Mw 4-5 earthquakes in the Bucaramanga Nest implies a temperature increase of 600-1000C for a centimeter-scale layer during earthquake failure. This suggests that substantial shear heating, and possibly partial melting, occurs during intermediate-depth earthquake failure. Our observations support thermal shear runaway as the mechanism for intermediate-depth earthquakes, which would help explain differences in their behavior compared to shallow earthquakes.

  10. Loma Prieta earthquake, October 17, 1989, Santa Cruz County, California

    SciTech Connect

    McNutt, S.

    1990-01-01

    On Tuesday, October 17, 1989 at 5:04 p.m. Pacific Daylight Time, a magnitude 7.1 earthquake occurred on the San Andreas fault 10 miles northeast of Santa Cruz. This earthquake was the largest earthquake to occur in the San Francisco Bay area since 1906, and the largest anywhere in California since 1952. The earthquake was responsible for 67 deaths and about 7 billion dollars worth of damage, making it the biggest dollar loss natural disaster in United States history. This article describes the seismological features of the earthquake, and briefly outlines a number of other geologic observations made during study of the earthquake, its aftershocks, and its effects. Much of the information in this article was provided by the U.S. Geological Survey (USGS).

  11. Frog Swarms: Earthquake Precursors or False Alarms?

    PubMed

    Grant, Rachel A; Conlan, Hilary

    2013-01-01

    In short-term earthquake risk forecasting, the avoidance of false alarms is of utmost importance to preclude the possibility of unnecessary panic among populations in seismic hazard areas. Unusual animal behaviour prior to earthquakes has been reported for millennia but has rarely been scientifically documented. Recently large migrations or unusual behaviour of amphibians have been linked to large earthquakes, and media reports of large frog and toad migrations in areas of high seismic risk such as Greece and China have led to fears of a subsequent large earthquake. However, at certain times of year large migrations are part of the normal behavioural repertoire of amphibians. News reports of "frog swarms" from 1850 to the present day were examined for evidence that this behaviour is a precursor to large earthquakes. It was found that only two of 28 reported frog swarms preceded large earthquakes (Sichuan province, China in 2008 and 2010). All of the reported mass migrations of amphibians occurred in late spring, summer and autumn and appeared to relate to small juvenile anurans (frogs and toads). It was concluded that most reported "frog swarms" are actually normal behaviour, probably caused by juvenile animals migrating away from their breeding pond, after a fruitful reproductive season. As amphibian populations undergo large fluctuations in numbers from year to year, this phenomenon will not occur on a yearly basis but will depend on successful reproduction, which is related to numerous climatic and geophysical factors. Hence, most large swarms of amphibians, particularly those involving very small frogs and occurring in late spring or summer, are not unusual and should not be considered earthquake precursors. In addition, it is likely that reports of several mass migration of small toads prior to the Great Sichuan Earthquake in 2008 were not linked to the subsequent M = 7.9 event (some occurred at a great distance from the epicentre), and were probably co-incidence. Statistical analysis of the data indicated frog swarms are unlikely to be connected with earthquakes. Reports of unusual behaviour giving rise to earthquake fears should be interpreted with caution, and consultation with experts in the field of earthquake biology is advised. PMID:26479746

  12. Sichuan Earthquake in China

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Sichuan earthquake in China occurred on May 12, 2008, along faults within the mountains, but near and almost parallel the mountain front, northwest of the city of Chengdu. This major quake caused immediate and severe damage to many villages and cities in the area. Aftershocks pose a continuing danger, but another continuing hazard is the widespread occurrence of landslides that have formed new natural dams and consequently new lakes. These lakes are submerging roads and flooding previously developed lands. But an even greater concern is the possible rapid release of water as the lakes eventually overflow the new dams. The dams are generally composed of disintegrated rock debris that may easily erode, leading to greater release of water, which may then cause faster erosion and an even greater release of water. This possible 'positive feedback' between increasing erosion and increasing water release could result in catastrophic debris flows and/or flooding. The danger is well known to the Chinese earthquake response teams, which have been building spillways over some of the new natural dams.

    This ASTER image, acquired on June 1, 2008, shows two of the new large landslide dams and lakes upstream from the town of Chi-Kua-Kan at 32o12'N latitude and 104o50'E longitude. Vegetation is green, water is blue, and soil is grayish brown in this enhanced color view. New landslides appear bright off-white. The northern (top) lake is upstream from the southern lake. Close inspection shows a series of much smaller lakes in an elongated 'S' pattern along the original stream path. Note especially the large landslides that created the dams. Some other landslides in this area, such as the large one in the northeast corner of the image, occur only on the mountain slopes, so do not block streams, and do not form lakes.

  13. Crowdsourced earthquake early warning.

    PubMed

    Minson, Sarah E; Brooks, Benjamin A; Glennie, Craig L; Murray, Jessica R; Langbein, John O; Owen, Susan E; Heaton, Thomas H; Iannucci, Robert A; Hauser, Darren L

    2015-04-01

    Earthquake early warning (EEW) can reduce harm to people and infrastructure from earthquakes and tsunamis, but it has not been implemented in most high earthquake-risk regions because of prohibitive cost. Common consumer devices such as smartphones contain low-cost versions of the sensors used in EEW. Although less accurate than scientific-grade instruments, these sensors are globally ubiquitous. Through controlled tests of consumer devices, simulation of an M w (moment magnitude) 7 earthquake on California's Hayward fault, and real data from the M w 9 Tohoku-oki earthquake, we demonstrate that EEW could be achieved via crowdsourcing. PMID:26601167

  14. Crowdsourced earthquake early warning

    PubMed Central

    Minson, Sarah E.; Brooks, Benjamin A.; Glennie, Craig L.; Murray, Jessica R.; Langbein, John O.; Owen, Susan E.; Heaton, Thomas H.; Iannucci, Robert A.; Hauser, Darren L.

    2015-01-01

    Earthquake early warning (EEW) can reduce harm to people and infrastructure from earthquakes and tsunamis, but it has not been implemented in most high earthquake-risk regions because of prohibitive cost. Common consumer devices such as smartphones contain low-cost versions of the sensors used in EEW. Although less accurate than scientific-grade instruments, these sensors are globally ubiquitous. Through controlled tests of consumer devices, simulation of an Mw (moment magnitude) 7 earthquake on California’s Hayward fault, and real data from the Mw 9 Tohoku-oki earthquake, we demonstrate that EEW could be achieved via crowdsourcing. PMID:26601167

  15. The Geology of Earthquakes

    NASA Astrophysics Data System (ADS)

    Wallace, Robert E.

    The Geology of Earthquakes is a major contribution that brings together under one cover the many and complex elements of geology that are fundamental to earthquakes and seismology. Here are described and analyzed the basic causes of earthquakes, the resulting effects of earthquakes and faulting on the surface of the Earth, techniques of analyzing these effects, and engineering and public policy considerations for earthquake hazard mitigation. The three authors have played major roles in developing the fundamentals in both scientific and policy matters; thus they speak with an authority that few others could.

  16. The effects of earthquake measurement concepts and magnitude anchoring on individuals' perceptions of earthquake risk

    USGS Publications Warehouse

    Celsi, R.; Wolfinbarger, M.; Wald, D.

    2005-01-01

    The purpose of this research is to explore earthquake risk perceptions in California. Specifically, we examine the risk beliefs, feelings, and experiences of lay, professional, and expert individuals to explore how risk is perceived and how risk perceptions are formed relative to earthquakes. Our results indicate that individuals tend to perceptually underestimate the degree that earthquake (EQ) events may affect them. This occurs in large part because individuals' personal felt experience of EQ events are generally overestimated relative to experienced magnitudes. An important finding is that individuals engage in a process of "cognitive anchoring" of their felt EQ experience towards the reported earthquake magnitude size. The anchoring effect is moderated by the degree that individuals comprehend EQ magnitude measurement and EQ attenuation. Overall, the results of this research provide us with a deeper understanding of EQ risk perceptions, especially as they relate to individuals' understanding of EQ measurement and attenuation concepts. ?? 2005, Earthquake Engineering Research Institute.

  17. Earthquake Stress Transfer within Continents: Migrating Earthquakes and Long Aftershock Sequences

    NASA Astrophysics Data System (ADS)

    Stein, S. A.; Liu, M.; Wang, H.

    2009-12-01

    Stress transfer after large earthquakes has different effects within continental plate interiors than at plate boundaries. These differences explain why the spatio-temporal patterns of earthquakes in the two environments are so different given that the physics of fault rupture is essentially the same. At plate boundaries, steady plate motion reloads faults quickly after large earthquakes. This tectonic reloading soon dominates all other stress effects including those due to earthquakes on other faults. As a result, fault segments produce quasi-periodic earthquakes. In contrast, after a large mid-continental earthquake, stress reaccumulates very slowly - if at all - on the fault that broke. Instead, the resulting stress changes can give rise to earthquakes on other faults that have been quiescent for a long time. As a result, continental seismicity is often episodic, temporally clustered, and migrate between faults over thousands of years. A striking example of this variability is in North China, where large (M>7) earthquakes have been frequent, but not a single one repeated in the same place since 1300 A.D. For similar reasons, aftershock sequences within continents can last hundreds of years. Aftershocks result from changes of stress and fault properties induced by the main shock. At a plate boundary, steady plate motion quickly reloads the fault after a large earthquake and overwhelms the effects of the main shock. Within continents, however, the faults are reloaded much more slowly, allowing aftershocks to continue much longer. The observed aftershock sequence lengths are consistent with a simple model based on rate-and-state fault friction that predicts that the length of aftershock sequences varies inversely with the fault loading rate. Recognizing the migration of large earthquakes and long aftershock sequences is crucial for seismic hazard assessment within continents. Because many small earthquakes are probably aftershocks, their locations are unlikely to indicate the timing or the locations of future large earthquakes. Moreover, because in the short term much of the seismic hazard results from aftershocks, which can be damaging, these aftershocks should not be removed in attempts to infer earthquake recurrence. In the longer term, relying unduly on recent seismicity to predict the locations of future large earthquakes will overestimate the hazard in some places and lead to surprises elsewhere.

  18. The surface latent heat flux anomalies related to major earthquake

    NASA Astrophysics Data System (ADS)

    Jing, Feng; Shen, Xuhui; Kang, Chunli; Xiong, Pan; Hong, Shunying

    2011-12-01

    SLHF (Surface Latent Heat Flux) is an atmospheric parameter, which can describe the heat released by phase changes and dependent on meteorological parameters such as surface temperature, relative humidity, wind speed etc. There is a sharp difference between the ocean surface and the land surface. Recently, many studies related to the SLHF anomalies prior to earthquakes have been developed. It has been shown that the energy exchange enhanced between coastal surface and atmosphere prior to earthquakes can increase the rate of the water-heat exchange, which will lead to an obviously increases in SLHF. In this paper, two earthquakes in 2010 (Haiti earthquake and southwest of Sumatra in Indonesia earthquake) have been analyzed using SLHF data by STD (standard deviation) threshold method. It is shows that the SLHF anomaly may occur in interpolate earthquakes or intraplate earthquakes and coastal earthquakes or island earthquakes. And the SLHF anomalies usually appear 5-6 days prior to an earthquake, then disappear quickly after the event. The process of anomaly evolution to a certain extent reflects a dynamic energy change process about earthquake preparation, that is, weak-strong-weak-disappeared.

  19. Ice melting and earthquake suppression in Greenland

    NASA Astrophysics Data System (ADS)

    Olivieri, M.; Spada, G.

    2015-03-01

    It has been suggested that the Greenland ice sheet is the cause of earthquake suppression in the region. With few exceptions, the observed seismicity extends only along the continental margins of Greenland, which almost coincide with the ice sheet margin. This pattern has been put forward as further validation of the earthquake suppression hypothesis. In this review, new evidence in terms of ice melting, post-glacial rebound and earthquake occurrence is gathered and discussed to re-evaluate the connection between ice mass unloading and earthquake suppression. In Greenland, the spatio-temporal distribution of earthquakes indicates that seismicity is mainly confined to regions where the thick layer of ice is absent and where significant ice melting is presently occurring. A clear correlation between seismic activity and ice melting in Greenland is not found. However, earthquake locations and corresponding depth distributions suggest two distinct governing mechanisms: post-glacial rebound promotes moderate-size crustal earthquakes at Greenland's regional scale, while current ice melting promotes shallow low magnitude seismicity locally.

  20. Scaling of seismic memory with earthquake size.

    PubMed

    Zheng, Zeyu; Yamasaki, Kazuko; Tenenbaum, Joel; Podobnik, Boris; Tamura, Yoshiyasu; Stanley, H Eugene

    2012-07-01

    It has been observed that discrete earthquake events possess memory, i.e., that events occurring in a particular location are dependent on the history of that location. We conduct an analysis to see whether continuous real-time data also display a similar memory and, if so, whether such autocorrelations depend on the size of earthquakes within close spatiotemporal proximity. We analyze the seismic wave form database recorded by 64 stations in Japan, including the 2011 "Great East Japan Earthquake," one of the five most powerful earthquakes ever recorded, which resulted in a tsunami and devastating nuclear accidents. We explore the question of seismic memory through use of mean conditional intervals and detrended fluctuation analysis (DFA). We find that the wave form sign series show power-law anticorrelations while the interval series show power-law correlations. We find size dependence in earthquake autocorrelations: as the earthquake size increases, both of these correlation behaviors strengthen. We also find that the DFA scaling exponent ? has no dependence on the earthquake hypocenter depth or epicentral distance. PMID:23005368

  1. Scaling of seismic memory with earthquake size

    NASA Astrophysics Data System (ADS)

    Zheng, Zeyu; Yamasaki, Kazuko; Tenenbaum, Joel; Podobnik, Boris; Tamura, Yoshiyasu; Stanley, H. Eugene

    2012-07-01

    It has been observed that discrete earthquake events possess memory, i.e., that events occurring in a particular location are dependent on the history of that location. We conduct an analysis to see whether continuous real-time data also display a similar memory and, if so, whether such autocorrelations depend on the size of earthquakes within close spatiotemporal proximity. We analyze the seismic wave form database recorded by 64 stations in Japan, including the 2011 “Great East Japan Earthquake,” one of the five most powerful earthquakes ever recorded, which resulted in a tsunami and devastating nuclear accidents. We explore the question of seismic memory through use of mean conditional intervals and detrended fluctuation analysis (DFA). We find that the wave form sign series show power-law anticorrelations while the interval series show power-law correlations. We find size dependence in earthquake autocorrelations: as the earthquake size increases, both of these correlation behaviors strengthen. We also find that the DFA scaling exponent α has no dependence on the earthquake hypocenter depth or epicentral distance.

  2. Changes in Permeability Produced By Distant Earthquakes

    NASA Astrophysics Data System (ADS)

    Manga, M.; Wang, C. Y.; Shi, Z.

    2014-12-01

    Oscillations in stress, such as those created by earthquakes, can increase permeability and fluid mobility in geologic media. In natural systems, strain amplitudes as small as 10-6 can increase discharge in streams and springs, change the water level of wells, and enhance production from petroleum reservoirs. Enhanced permeability typically recovers to pre-stimulated values over a period of months to years. This presentation will review some of the observations that indicate that dynamic stresses produced by seismic waves change permeability. We use the response of a set of wells distributed throughout China to multiple large earthquakes to probe the relationship between earthquake-generated stresses and water-level changes in wells. We find that dynamic stresses dominate the responses at distances more than 1 fault length from the earthquake and that permeability changes may explain the water level changes. Regions with high deformation rates are most sensitive to seismic waves. We also consider the response of a large alluvial fan in Taiwan to the 1999 M7.5 Chi-Chi earthquake where there were sustained changes in groundwater temperature after the earthquake. Using groundwater flow models, we infer that permeability increased by an order of magnitude over horizontal scales of tens of km, and vertical scales of several km. Permeability returned to the pre-earthquake value over many months. As much as half the total transport in the fan occurs during the short time periods with enhanced permeability.

  3. Intensity earthquake scenario (scenario event - a damaging earthquake with higher probability of occurrence) for the city of Sofia

    NASA Astrophysics Data System (ADS)

    Aleksandrova, Irena; Simeonova, Stela; Solakov, Dimcho; Popova, Maria

    2014-05-01

    Among the many kinds of natural and man-made disasters, earthquakes dominate with regard to their social and economical impact on the urban environment. Global seismic risk to earthquakes are increasing steadily as urbanization and development occupy more areas that a prone to effects of strong earthquakes. Additionally, the uncontrolled growth of mega cities in highly seismic areas around the world is often associated with the construction of seismically unsafe buildings and infrastructures, and undertaken with an insufficient knowledge of the regional seismicity peculiarities and seismic hazard. The assessment of seismic hazard and generation of earthquake scenarios is the first link in the prevention chain and the first step in the evaluation of the seismic risk. The earthquake scenarios are intended as a basic input for developing detailed earthquake damage scenarios for the cities and can be used in earthquake-safe town and infrastructure planning. The city of Sofia is the capital of Bulgaria. It is situated in the centre of the Sofia area that is the most populated (the population is of more than 1.2 mil. inhabitants), industrial and cultural region of Bulgaria that faces considerable earthquake risk. The available historical documents prove the occurrence of destructive earthquakes during the 15th-18th centuries in the Sofia zone. In 19th century the city of Sofia has experienced two strong earthquakes: the 1818 earthquake with epicentral intensity I0=8-9 MSK and the 1858 earthquake with I0=9-10 MSK. During the 20th century the strongest event occurred in the vicinity of the city of Sofia is the 1917 earthquake with MS=5.3 (I0=7-8 MSK). Almost a century later (95 years) an earthquake of moment magnitude 5.6 (I0=7-8 MSK) hit the city of Sofia, on May 22nd, 2012. In the present study as a deterministic scenario event is considered a damaging earthquake with higher probability of occurrence that could affect the city with intensity less than or equal to VIII. The usable and realistic ground motion maps for urban areas are generated: - either from the assumption of a "reference earthquake" - or directly, showing values of macroseimic intensity generated by a damaging, real earthquake. In the study, applying deterministic approach, earthquake scenario in macroseismic intensity ("model" earthquake scenario) for the city of Sofia is generated. The deterministic "model" intensity scenario based on assumption of a "reference earthquake" is compared with a scenario based on observed macroseimic effects caused by the damaging 2012 earthquake (MW5.6). The difference between observed (Io) and predicted (Ip) intensities values is analyzed.

  4. Earthquake Observation through Groundwater Monitoring in South Korea

    NASA Astrophysics Data System (ADS)

    Piao, J.; Woo, N. C.

    2014-12-01

    According to previous researches, the influence of the some earthquakes can be detected by groundwater monitoring. Even in some countries groundwater monitoring is being used as an important tool to identify earthquake precursors and prediction measures. Thus, in this study we attempt to catch the anomalous changes in groundwater produced by earthquakes occurred in Korea through the National Groundwater Monitoring Network (NGMN). For observing the earthquake impacts on groundwater more effectively, from the National Groundwater Monitoring Network we selected 28 stations located in the five earthquake-prone zones in South Korea. And we searched the responses to eight earthquakes with M ?2.5 which occurred in the vicinity of five earthquake-prone zones in 2012. So far, we tested the groundwater monitoring data (water-level, temperature and electrical conductivity). Those data have only been treated to remove barometric pressure changes. Then we found 29 anomalous changes, confirming that groundwater monitoring data can provide valuable information on earthquake effects. To identify the effect of the earthquake from mixture signals of water-level, other signals must be separated from the original data. Periodic signals will be separated from the original data using Fast Fourier Transform (FFT). After that we will attempt to separate precipitation effect, and determine if the anomalies were generated by earthquake or not.

  5. Frequently Asked Questions (FAQ) about Extreme Heat

    MedlinePLUS

    ... Health Matters What's New Preparation & Planning Disasters & Severe Weather Earthquakes Extreme Heat Floods Hurricanes Landslides Tornadoes Tsunamis ... environment. How much should I drink during hot weather? During hot weather you will need to drink ...

  6. Strong ground motion from the michoacan, Mexico, earthquake.

    PubMed

    Anderson, J G; Bodin, P; Brune, J N; Prince, J; Singh, S K; Quaas, R; Onate, M

    1986-09-01

    The network of strong motion accelerographs in Mexico includes instruments that were installed, under an international cooperative research program, in sites selected for the high potenial of a large earthquake. The 19 September 1985 earthquake (magnitude 8.1) occurred in a seismic gap where an earthquake was expected. As a result, there is an excellent descripton of the ground motions that caused the disaster. PMID:17746576

  7. Strong Ground Motion from the Michoacan, Mexico, Earthquake

    NASA Astrophysics Data System (ADS)

    Anderson, J. G.; Bodin, P.; Brune, J. N.; Prince, J.; Singh, S. K.; Quaas, R.; Onate, M.

    1986-09-01

    The network of strong motion accelerographs in Mexico includes instruments that were installed, under an international cooperative research program, in sites selected for the high potential of a large earthquake. The 19 September 1985 earthquake (magnitude 8.1) occurred in a seismic gap where an earthquake was expected. As a result, there is an excellent description of the ground motions that caused the disaster.

  8. Earthquake catalog for estimation of maximum earthquake magnitude, Central and Eastern United States: Part A, Prehistoric earthquakes

    USGS Publications Warehouse

    Wheeler, Russell L.

    2014-01-01

    Computation of probabilistic earthquake hazard requires an estimate of Mmax, the maximum earthquake magnitude thought to be possible within a specified geographic region. This report is Part A of an Open-File Report that describes the construction of a global catalog of moderate to large earthquakes, from which one can estimate Mmax for most of the Central and Eastern United States and adjacent Canada. The catalog and Mmax estimates derived from it were used in the 2014 edition of the U.S. Geological Survey national seismic-hazard maps. This Part A discusses prehistoric earthquakes that occurred in eastern North America, northwestern Europe, and Australia, whereas a separate Part B deals with historical events.

  9. Earthquake forecasting and warning

    SciTech Connect

    Rikitake, T.

    1983-01-01

    This review briefly describes two other books on the same subject either written or partially written by Rikitake. In this book, the status of earthquake prediction efforts in Japan, China, the Soviet Union, and the United States are updated. An overview of some of the organizational, legal, and societal aspects of earthquake prediction in these countries is presented, and scientific findings of precursory phenomena are included. A summary of circumstances surrounding the 1975 Haicheng earthquake, the 1978 Tangshan earthquake, and the 1976 Songpan-Pingwu earthquake (all magnitudes = 7.0) in China and the 1978 Izu-Oshima earthquake in Japan is presented. This book fails to comprehensively summarize recent advances in earthquake prediction research.

  10. Significant earthquakes on the Enriquillo fault system, Hispaniola, 1500-2010

    NASA Astrophysics Data System (ADS)

    Bakun, W.; Flores, C. H.; ten Brink, U. S.

    2010-12-01

    Although the 2010 Haiti earthquake came as a surprise to many, historical records indicate frequent seismic activity along the northeast Caribbean plate boundary over the past 500 years, particularly on the island of Hispaniola. Here we show that a series of devastating earthquakes on the Enriquillo fault system in the 18th century started with an intensity magnitude (MI) of 6.8 earthquake in 1701 near the location of the 2010 Haiti earthquake and that the accounts of the shaking in the 1701 earthquake are similar to those of the 2010 earthquake. A series of large earthquakes migrating from east to west started with the October 18, 1751 MI7.6 earthquake near the eastern end of the fault in the Dominican Republic, followed by the November 21, 1751 MI6.7 earthquake near Port-au-Prince, Haiti, and the June 3, 1770 MI7.7 earthquake west of the 2010 earthquake rupture. We associate no other significant events since 1500 with the Enriquillo fault system. The 2010 Haiti earthquake may mark the beginning of a new cycle of large earthquakes on the Enriquillo fault system after 240 years of quiescence. Future devastating earthquakes should be expected.

  11. Source Characteristics of Shallow Intraslab Earthquakes from Strong Motion Data

    NASA Astrophysics Data System (ADS)

    Asano, K.; Iwata, T.; Irikura, K.

    2002-12-01

    Large shallow intraslab earthquakes, occurring within subducting slabs at 30-100km depths, generate earthquake damages by strong ground motions (e.g. the 1993 Kushiro-oki earthquake, the 2001 Geiyo earthquake, and the 2001 Nisqually earthquake). Source characteristics of intraslab earthquakes have been pointed out to have some different features compared to those of inland crustal earthquakes and interplate earthquakes by some researchers. We examined six shallow intraslab earthquakes that recently occurred around Japan (MJMA 5.1-7.0) using dense strong motion network data. The observed peak ground accelerations at K-NET stations for the 2001 Geiyo earthquake in near distance are about 3 times larger than those expected from the attenuation relation based on inland crustal earthquakes proposed by Fukushima and Tanaka (1992). For other intraslab events, the observed peak ground accelerations are also larger than the expected values. These seem to be related with high stress drop in source as well as low attenuation along the propagation path in case of intraslab earthquakes. We carried out strong motion simulation based on the empirical Green's function method to investigate the source characteristics of intraslab earthquakes. Using the empirical Green's function method, we can construct the source model to explain observed waveforms in broadband frequency range (Irikura, 1986; Miyake et al., 1999). We used the observed waveforms of a small event occurring at each source region as the empirical Green's function, and estimated the number, size, and location of asperity (strong motion generation area), rise time, and rupture propagation velocity of target events by forward modeling. Since the combined area of asperities obtained for each earthquake is about 14-66% of values predicted by the empirical relation for inland crustal earthquakes proposed by Somerville et al. (1999), the stress drops on asperity of shallow intraslab earthquakes are higher than those of inland crustal earthquakes. The ratios between the combined area of asperities obtained in this study and the value predicted from the empirical relation decrease with focal depth. The stress drops on asperity of shallow intraslab earthquakes increase with focal depth. We used the strong motion data from K-NET, KiK-net, and F-net operated by the National Research Institute for Earth Science and Disaster Prevention (NIED) and the CMT solutions by F-net and Harvard University. We also used the hypocentral information provided by the Japan Meteorological Agency (JMA).

  12. Frequent Hemodialysis Fistula Infectious Complications

    PubMed Central

    Lok, Charmaine E.; Sontrop, Jessica M.; Faratro, Rose; Chan, Christopher T.; Zimmerman, Deborah Lynn

    2014-01-01

    Background Few studies have examined if infectious arteriovenous access complications vary with the cannulation technique and whether this is modified by dialysis frequency. We compared the infection rate between fistulas cannulated using buttonhole versus stepladder techniques for patients treated with short daily (SDH) or nocturnal hemodialysis at home (NHD). We also compared patients receiving conventional intermittent hemodialysis (CIHD) using stepladder cannulation. Methods Data were prospectively collected from 631 patients dialyzed with a fistula from 2001 to 2010 (Toronto and Ottawa, Canada). We compared the person-time incidence rate of bacteremia and local fistula infections using the exact binomial test. Results Forty-six (7.3%) patients received SDH (?5 sessions/week, 2-4 h/session), 128 (20.3%) NHD (?4 sessions/week, ?5 h/session) and 457 (72%) CIHD (3 sessions/week, ?4 h/session). Fifty percent of SDH and 72% of NHD patients used the buttonhole technique. There were 39 buttonhole-related bacteremias (rate: 0.196/1,000 fistula days) and at least 2 local buttonhole site infections. Staphylococcus aureus accounted for 85% of the bacteremias. There were 5 (13%) infection-related hospitalizations and 3 (10%) serious metastatic infections, including fistula loss. In comparison, there was 1 possible fistula-related infection in CIHD during follow-up (rate: 0.002/1,000 fistula days). Conclusions The rate of buttonhole-related infections was high among patients on frequent hemodialysis and more than 50 times greater than that among patients on CIHD with the stepladder technique. Most bacteremias were due to S. aureus with serious consequences. The risks and benefits of buttonhole cannulation require individual consideration with careful monitoring, prophylaxis and management. PMID:25473405

  13. Introduction to the special issue on the 2004 Parkfield earthquake and the Parkfield earthquake prediction experiment

    USGS Publications Warehouse

    Harris, R.A.; Arrowsmith, J.R.

    2006-01-01

    The 28 September 2004 M 6.0 Parkfield earthquake, a long-anticipated event on the San Andreas fault, is the world's best recorded earthquake to date, with state-of-the-art data obtained from geologic, geodetic, seismic, magnetic, and electrical field networks. This has allowed the preearthquake and postearthquake states of the San Andreas fault in this region to be analyzed in detail. Analyses of these data provide views into the San Andreas fault that show a complex geologic history, fault geometry, rheology, and response of the nearby region to the earthquake-induced ground movement. Although aspects of San Andreas fault zone behavior in the Parkfield region can be modeled simply over geological time frames, the Parkfield Earthquake Prediction Experiment and the 2004 Parkfield earthquake indicate that predicting the fine details of future earthquakes is still a challenge. Instead of a deterministic approach, forecasting future damaging behavior, such as that caused by strong ground motions, will likely continue to require probabilistic methods. However, the Parkfield Earthquake Prediction Experiment and the 2004 Parkfield earthquake have provided ample data to understand most of what did occur in 2004, culminating in significant scientific advances.

  14. Frequent Video Game Players Resist Perceptual Interference

    PubMed Central

    Berard, Aaron V.; Cain, Matthew S.; Watanabe, Takeo; Sasaki, Yuka

    2015-01-01

    Playing certain types of video games for a long time can improve a wide range of mental processes, from visual acuity to cognitive control. Frequent gamers have also displayed generalized improvements in perceptual learning. In the Texture Discrimination Task (TDT), a widely used perceptual learning paradigm, participants report the orientation of a target embedded in a field of lines and demonstrate robust over-night improvement. However, changing the orientation of the background lines midway through TDT training interferes with overnight improvements in overall performance on TDT. Interestingly, prior research has suggested that this effect will not occur if a one-hour break is allowed in between the changes. These results have suggested that after training is over, it may take some time for learning to become stabilized and resilient against interference. Here, we tested whether frequent gamers have faster stabilization of perceptual learning compared to non-gamers and examined the effect of daily video game playing on interference of training of TDT with one background orientation on perceptual learning of TDT with a different background orientation. As a result, we found that non-gamers showed overnight performance improvement only on one background orientation, replicating previous results with the interference in TDT. In contrast, frequent gamers demonstrated overnight improvements in performance with both background orientations, suggesting that they are better able to overcome interference in perceptual learning. This resistance to interference suggests that video game playing not only enhances the amplitude and speed of perceptual learning but also leads to faster and/or more robust stabilization of perceptual learning. PMID:25807394

  15. Frequent video game players resist perceptual interference.

    PubMed

    Berard, Aaron V; Cain, Matthew S; Watanabe, Takeo; Sasaki, Yuka

    2015-01-01

    Playing certain types of video games for a long time can improve a wide range of mental processes, from visual acuity to cognitive control. Frequent gamers have also displayed generalized improvements in perceptual learning. In the Texture Discrimination Task (TDT), a widely used perceptual learning paradigm, participants report the orientation of a target embedded in a field of lines and demonstrate robust over-night improvement. However, changing the orientation of the background lines midway through TDT training interferes with overnight improvements in overall performance on TDT. Interestingly, prior research has suggested that this effect will not occur if a one-hour break is allowed in between the changes. These results have suggested that after training is over, it may take some time for learning to become stabilized and resilient against interference. Here, we tested whether frequent gamers have faster stabilization of perceptual learning compared to non-gamers and examined the effect of daily video game playing on interference of training of TDT with one background orientation on perceptual learning of TDT with a different background orientation. As a result, we found that non-gamers showed overnight performance improvement only on one background orientation, replicating previous results with the interference in TDT. In contrast, frequent gamers demonstrated overnight improvements in performance with both background orientations, suggesting that they are better able to overcome interference in perceptual learning. This resistance to interference suggests that video game playing not only enhances the amplitude and speed of perceptual learning but also leads to faster and/or more robust stabilization of perceptual learning. PMID:25807394

  16. Disturbances in equilibrium function after major earthquake

    PubMed Central

    Honma, Motoyasu; Endo, Nobutaka; Osada, Yoshihisa; Kim, Yoshiharu; Kuriyama, Kenichi

    2012-01-01

    Major earthquakes were followed by a large number of aftershocks and significant outbreaks of dizziness occurred over a large area. However it is unclear why major earthquake causes dizziness. We conducted an intergroup trial on equilibrium dysfunction and psychological states associated with equilibrium dysfunction in individuals exposed to repetitive aftershocks versus those who were rarely exposed. Greater equilibrium dysfunction was observed in the aftershock-exposed group under conditions without visual compensation. Equilibrium dysfunction in the aftershock-exposed group appears to have arisen from disturbance of the inner ear, as well as individual vulnerability to state anxiety enhanced by repetitive exposure to aftershocks. We indicate potential effects of autonomic stress on equilibrium function after major earthquake. Our findings may contribute to risk management of psychological and physical health after major earthquakes with aftershocks, and allow development of a new empirical approach to disaster care after such events. PMID:23087814

  17. Disturbances in equilibrium function after major earthquake

    NASA Astrophysics Data System (ADS)

    Honma, Motoyasu; Endo, Nobutaka; Osada, Yoshihisa; Kim, Yoshiharu; Kuriyama, Kenichi

    2012-10-01

    Major earthquakes were followed by a large number of aftershocks and significant outbreaks of dizziness occurred over a large area. However it is unclear why major earthquake causes dizziness. We conducted an intergroup trial on equilibrium dysfunction and psychological states associated with equilibrium dysfunction in individuals exposed to repetitive aftershocks versus those who were rarely exposed. Greater equilibrium dysfunction was observed in the aftershock-exposed group under conditions without visual compensation. Equilibrium dysfunction in the aftershock-exposed group appears to have arisen from disturbance of the inner ear, as well as individual vulnerability to state anxiety enhanced by repetitive exposure to aftershocks. We indicate potential effects of autonomic stress on equilibrium function after major earthquake. Our findings may contribute to risk management of psychological and physical health after major earthquakes with aftershocks, and allow development of a new empirical approach to disaster care after such events.

  18. Strong ground motion prediction using virtual earthquakes.

    PubMed

    Denolle, M A; Dunham, E M; Prieto, G A; Beroza, G C

    2014-01-24

    Sedimentary basins increase the damaging effects of earthquakes by trapping and amplifying seismic waves. Simulations of seismic wave propagation in sedimentary basins capture this effect; however, there exists no method to validate these results for earthquakes that have not yet occurred. We present a new approach for ground motion prediction that uses the ambient seismic field. We apply our method to a suite of magnitude 7 scenario earthquakes on the southern San Andreas fault and compare our ground motion predictions with simulations. Both methods find strong amplification and coupling of source and structure effects, but they predict substantially different shaking patterns across the Los Angeles Basin. The virtual earthquake approach provides a new approach for predicting long-period strong ground motion. PMID:24458636

  19. "Naturally occurring asbestos

    NASA Astrophysics Data System (ADS)

    Cagnard, F.; Lahondère, D.; Blein, O.; Lahfid, A.; Wille, G.

    2012-04-01

    The term asbestos refers to six silicate minerals from amphibole and serpentine groups. By definition, it consists in bundles of thin and flexible long fibers, with high-tensile strength, and chemical and heat resistance. In contrast to asbestos found within commercial products and mining, the specific term ''naturally occurring asbestos'' (NOA) refers to asbestiform minerals occurring within rocks or soils that can be released by human activities or weathering processes. The fact that the exposure to asbestos is related to lung pathologies is now widely demonstrated (e.g. asbestosis, mesothelioma and lung cancer). However, if health risks associated with exposure to NOA exist, they are not yet well documented. The crystallization of natural asbestos occurs in specific Mg-rich lithologies associated with peculiar structural and metamorphic conditions. By recognizing and combining such specific geologic criteria, the presence or the absence of asbestos in bedrock terrains can be reasonably predicted and maps of NOA hazard can be drawn. We present here new results of geological mapping and petrological study concerning the evaluation of the NOA hazard in the Alps and Corsica, in France. The three folds approach consists in (1) a determination of lithologies with potential NOA from a bibliographic compilation and extraction of target zones from a geological geodatabase (2) a geological mapping of the target zones followed by a petrological characterization of sampled asbestiform minerals in the laboratory (optical microscopy, TEM, SEM, and Raman spectroscopy technics), and (3) the drawing of the final map of NOA hazard, at regional-scale. Occurrence criteria can be retained as follows: 1. NOA are abundant in the internal zones of the Alps and Corsica, especially within ophiolitic complexes. Natural asbestos are mostly concentrated within ultramafic rocks but can also occur within basic lithologies such as Mg-metagabbros, metabasalts and meta-pillow-lavas, 2. Asbestos is commonly located within fractures, shear-bands or shear-planes, developed during late retrograde metamorphic history, 3. Tremolite-actinolite-type asbestos is abundant both in ultramafic and mafic rocks, 4. Natural asbestos occur in few places within the external zones of the Alps, especially within hercynian ophiolitic massifs or concentrated in late Alpine fractures affecting leptyno-amphibolic lithologies.

  20. Earthquake sources near Uturuncu Volcano

    NASA Astrophysics Data System (ADS)

    Keyson, L.; West, M. E.

    2013-12-01

    Uturuncu, located in southern Bolivia near the Chile and Argentina border, is a dacitic volcano that was last active 270 ka. It is a part of the Altiplano-Puna Volcanic Complex, which spans 50,000 km2 and is comprised of a series of ignimbrite flare-ups since ~23 ma. Two sets of evidence suggest that the region is underlain by a significant magma body. First, seismic velocities show a low velocity layer consistent with a magmatic sill below depths of 15-20 km. This inference is corroborated by high electrical conductivity between 10km and 30km. This magma body, the so called Altiplano-Puna Magma Body (APMB) is the likely source of volcanic activity in the region. InSAR studies show that during the 1990s, the volcano experienced an average uplift of about 1 to 2 cm per year. The deformation is consistent with an expanding source at depth. Though the Uturuncu region exhibits high rates of crustal seismicity, any connection between the inflation and the seismicity is unclear. We investigate the root causes of these earthquakes using a temporary network of 33 seismic stations - part of the PLUTONS project. Our primary approach is based on hypocenter locations and magnitudes paired with correlation-based relative relocation techniques. We find a strong tendency toward earthquake swarms that cluster in space and time. These swarms often last a few days and consist of numerous earthquakes with similar source mechanisms. Most seismicity occurs in the top 10 kilometers of the crust and is characterized by well-defined phase arrivals and significant high frequency content. The frequency-magnitude relationship of this seismicity demonstrates b-values consistent with tectonic sources. There is a strong clustering of earthquakes around the Uturuncu edifice. Earthquakes elsewhere in the region align in bands striking northwest-southeast consistent with regional stresses.

  1. Forecasting the Next Great San Francisco Earthquake

    NASA Astrophysics Data System (ADS)

    Rundle, P.; Rundle, J. B.; Turcotte, D. L.; Donnellan, A.; Yakovlev, G.; Tiampo, K. F.

    2005-12-01

    The great San Francisco earthquake of 18 April 1906 and its subsequent fires killed more than 3,000 persons, and destroyed much of the city leaving 225,000 out of 400,000 inhabitants homeless. The 1906 earthquake occurred on a km segment of the San Andreas fault that runs from the San Juan Bautista north to Cape Mendocino and is estimated to have had a moment magnitude m ,l 7.9. Observations of surface displacements across the fault were in the range m. As we approach the 100 year anniversary of this event, a critical concern is the hazard posed by another such earthquake. In this talk we examine the assumptions presently used to compute the probability of occurrence of these earthquakes. We also present the results of a numerical simulation of interacting faults on the San Andreas system. Called Virtual California, this simulation can be used to compute the times, locations and magnitudes of simulated earthquakes on the San Andreas fault in the vicinity of San Francisco. Of particular importance are new results for the statistical distribution of interval times between great earthquakes, results that are difficult or impossible to obtain from a purely field-based approach. We find that our results are fit well under most circumstances by the Weibull statistical distribution, and we compute waiting times to future earthquakes based upon our simulation results. A contrasting approach to the same problem has been adopted by the Working Group on California Earthquake Probabilities, who use observational data combined with statistical assumptions to compute probabilities of future earthquakes.

  2. Source parameters of Ulsan, Korea offshore earthquake sequence in 2012

    NASA Astrophysics Data System (ADS)

    Park, Eun Hee; Park, Sun-Cheon; Jeon, Young Soo; Hwang, Eui-Hong; Lee, Chang Wook; Choi, Young-Jean

    2013-04-01

    Seismicity in Korea is known to be relatively low compared to China and Japan. But the seismicity seems to be relatively active historically, according to historical documents on earthquake. The magnitudes of historical earthquakes were estimated mostly to be about 4 - 6 and there were some events with magnitude over 6. Instrumental earthquakes recorded in 1978 - 2012 seem to be smaller than historical earthquakes, according to the report by the Korea Meteorological Administration (KMA). Their magnitudes are smaller than 4 in general. Although epicenters of instrumental earthquakes seem to be randomly distributed on the entire Korean Peninsula, Some earthquakes occur intensively in several specific areas in the East Sea and the easternregion of Jeju Island. Among these areas, we studied earthquake cluster zones in the East Sea. We installed portable seismographs (8 stations) in the eastern coast and ocean bottom seismometers (4 stations) in the East Sea to study micro-earthquake activity and geotectonics. Observation was carried out from October, 2011 to April, 2012. We detected about 60 micro-earthquakes occurred around the temporal stations during the observation period. Among the seismicity observed in the period, we analyzed 6 earthquakes sequentially occurred in the Ulsan offshore on February 19 - March 27, 2012. For analysis of Ulsan offshore earthquake sequence, we used various data sets, including permanent stations of KMA, temporary stations, and Broadband Seismograph Network (F-net) of the National Research Institute for Earth Science and Disaster Prevention (NIED). For the hypocenter determination, 1D velocity structure (Chang and Baag, 2006) and HYPOELLIPSE (Lahr, 1980) were used. The equation of Tsuboi (1954) was used for determination of magnitude. The epicenters of the earthquakes were distributed within 3 km and the focal depths were in the range of 13 - 17 km, meaning shallow events. Magnitudes were 2.0 - 3.2. The largest earthquake was M3.2 event occurred at 00:05 (UTC) on February 24, 2012. According to analysis of focal mechanism, this earthquake was oblique strike-slip fault event. Prior to the sequence, no earthquake occurred in this area, and the seismicity pattern of this sequence showed the characteristics of swarm behavior without obvious mainshock. To understand the characteristics of seismic acitivty in earthquake cluster zones in the East Sea, researches on swarm behavior may be needed.

  3. Seismic Hazard Assessment in China: From the 2008 Wenchuan Earthquake to the 2013 Minxian Earthquake

    NASA Astrophysics Data System (ADS)

    Wang, Z.

    2013-12-01

    Seismic-hazard assessment is an effort by earth scientists to estimate potential hazards, ground-motion hazard in particular, that could be generated by future earthquakes. Results from a seismic hazard assessment provide the basis for society to formulate policies to mitigate the impact of earthquakes. For example, the ground-motion hazards with 2, 5, and 10 percent probabilities of exceedance (PE) in 50 years, produced from a probabilistic seismic hazard analysis (PSHA), have been used to development mitigation policy in many countries, including the United States and China. Currently, the ground motion with 10 percent PE in 50 years is the basis for seismic design for buildings and other structures in China. However, recent earthquakes, including the 2008 Wenchuan, 2010 Yushu, and 2013 Lushan and Minxian earthquakes, showed that the hazard maps do not provide good estimates of the ground-motion hazards for the areas where these earthquakes occurred. All these earthquakes occurred in areas that were estimated to have low ground-motion hazards. These earthquakes demonstrate that the use of PSHA for seismic-hazard assessment is problematic.

  4. Computer simulation of earthquakes

    NASA Technical Reports Server (NTRS)

    Cohen, S. C.

    1976-01-01

    Two computer simulation models of earthquakes were studied for the dependence of the pattern of events on the model assumptions and input parameters. Both models represent the seismically active region by mechanical blocks which are connected to one another and to a driving plate. The blocks slide on a friction surface. In the first model elastic forces were employed and time independent friction to simulate main shock events. The size, length, and time and place of event occurrence were influenced strongly by the magnitude and degree of homogeniety in the elastic and friction parameters of the fault region. Periodically reoccurring similar events were frequently observed in simulations with near homogeneous parameters along the fault, whereas, seismic gaps were a common feature of simulations employing large variations in the fault parameters. The second model incorporated viscoelastic forces and time-dependent friction to account for aftershock sequences. The periods between aftershock events increased with time and the aftershock region was confined to that which moved in the main event.

  5. The Ordered Network Structure of M?8 Earthquakes and its Prediction for the Ordered Pair Great Earthquakes in Mainland China

    NASA Astrophysics Data System (ADS)

    Men, Ke-Pei; Zhao, Kai

    2014-04-01

    According to the statistical data, a total of 23 M ? 8 earthquakes occurred in Mainland China from 1303 to 2012. The seismic activity of M ? 8 earthquakes has showed an obvious self-organized orderliness. It should be remarked especially that there were three ordered pairs of M ?8 earthquakes occurred in West China during 1902 - 2001, of which the time interval in each pair of two earthquakes was four years. This is a unique and rare earthquake example in earthquake history of China and the world. In the guidance of the information forecasting theory of Wen-Bo Weng, based on previous research results, combining ordered analysis with complex network technology, this paper focuses on the summary of the ordered network structure of M ? 8 earthquakes, supplements new information, constructs and further optimizes the 2D- and 3D-ordered network structure of M ? 8 earthquakes to make prediction research. At last, a new prediction opinion is presented that the future ordered pair of great earthquakes will probably occur around 2022 and 2026 in Mainland China.

  6. The persistence of directivity in small earthquakes

    USGS Publications Warehouse

    Boatwright, J.

    2007-01-01

    We derive a simple inversion of peak ground acceleration (PGA) or peak ground velocity (PGV) for rupture direction and rupture velocity and then test this inversion on the peak motions obtained from seven 3.5 ??? M ??? 4.1 earthquakes that occurred in two clusters in November 2002 and February 2003 near San Ramon, California. These clusters were located on two orthogonal strike-slip faults so that the events share the same approximate focal mechanism but not the same fault plane. Three earthquakes exhibit strong directivity, but the other four earthquakes exhibit relatively weak directivity. We use the residual PGAs and PGVs from the other six events to determine station corrections for each earthquake. The inferred rupture directions unambiguously identify the fault plane for the three earthquakes with strong directivity and for three of the four earthquakes with weak directivity. The events with strong directivity have fast rupture velocities (0.63????? v ??? 0.87??); the events with weak directivity either rupture more slowly (0.17????? v ???0.35??) or bilaterally. The simple unilateral inversion cannot distinguish between slow and bilateral ruptures: adding a bilateral rupture component degrades the fit of the rupture directions to the fault planes. By comparing PGAs from the events with strong and weak directivity, we show how an up-dip rupture in small events can distort the attenuation of peak ground motion with distance. When we compare the rupture directions of the earthquakes to the location of aftershocks in the two clusters, we find than almost all the aftershocks of the three earthquakes with strong directivity occur within 70?? of the direction of rupture.

  7. The Likelihood of Major Global Earthquakes and the 2014 Napa Earthquake

    NASA Astrophysics Data System (ADS)

    Ejeta, M. Z.

    2014-12-01

    A previous study that analyzed global major earthquakes of magnitude 7.6 and above for the 1897 to 1977 period suggests that random occurrence of these earthquakes is very unlikely (Olsson 1982). Following an analysis of global major earthquakes of magnitude 7 and above for the 1901 to January 2010 period, a recent study attempts to show an association between major global earthquake and cyclic lunisolar alignment events (Ejeta 2011). The latter study suggests that the inverse square relationship in Newton's law of universal gravitation is likely to explain the physics behind the skewed occurrences of major earthquake events around these alignment events. Using random and non-random occurrence analysis, this paper will present the likelihoods of major global earthquakes since 1990 through September 2014 and how the magnitude 6.0 Napa earthquake of 2014 may be a particular realization of the observed association. Specifically, it will show that using the random occurrence approach, the average probability of occurrence on any day of the 396 major earthquakes recorded by the United States Geological Survey (USGS) during the selected period, which has 9,039 days, is about 4.4%. It will also show that based on the observed association, these events are skewed, with average probabilities of about 39% and 68%, respectively, towards one and two days within lunisolar alignment events recorded by the National Aeronautic and Space Administration (NASA) during the same period. Of the 396 major earthquake events during the selected period, 154 and 271 occurred, respectively, within one and two days of either new, first quarter, full, or last quarter moon days. This result suggests that a major earthquake event that occurred during this period was more likely than not to have occurred within two days of an alignment event. The magnitude 6.0 Napa earthquake of August 24, 2014, occurred within a day of the August 25, 2014, new moon day. This paper suggests that further research and insight is likely to increase this skewed probability and calls for a continued research into the likelihood of earthquakes and their global spatial distributions around known tectonic plates. It also poses the question of the impact that better awareness about this likelihood may have on the normal functioning of the built environment.

  8. Seismic and geodetic investigation of the 1996-1998 earthquake swarm at Strandline Lake, Alaska

    NASA Astrophysics Data System (ADS)

    Kilgore, Wayne W.; Roman, Diana C.; Biggs, Juliet; Hansen, Roger

    2011-09-01

    Microearthquake swarms occur frequently in volcanic environments, but do not always culminate in an eruption. Such non-eruptive swarms may be caused by stresses induced by magma intrusion, hydrothermal fluid circulation or possibly other tectonic processes such as slow-slip earthquakes. The Strandline Lake region of southcentral Alaska, located 30 km northeast of Mt Spurr volcano, experienced an intense earthquake swarm between 1996 August and 1998 September. A total of 2507 earthquakes were recorded by the Alaska Volcano Observatory's permanent seismic network during the swarm period, with a maximum magnitude of ML 3.6. The cumulative seismic moment of the swarm was 1.2 1015 N m, equivalent to that of a single Mw 4.0 earthquake. Because of the swarm's distance from the nearest Holocene volcanic vent, seismic monitoring was minimal and gas emission and GPS data do not exist for the swarm period. However, combined waveforms from a dense seismic network on Mt Spurr and from several regional seismic stations allow reanalysis of a representative set of swarm and background earthquakes. Swarm hypocentres calculated using a newly formulated 1-D velocity model and station corrections indicate a roughly circular swarm volume with dimensions of approximately 5 km, centred below 10 km below sea level (BSL). Composite fault-plane solutions for swarm earthquakes indicate oblique strike-slip faulting with a northeast-trending P-axis orientation. In contrast, a composite fault-plane solution for background earthquakes indicates a fundamentally different, though poorly constrained, local stress field orientation. Interferometric Synthetic Aperture Radar images spanning the swarm period unambiguously show no evidence of surface deformation, but do not rule out subcentimetre-scale deformation during the swarm. While a shallow (<10 km BSL) magma intrusion appears to be an unlikely cause of the 1996-1998 Strandline Lake swarm based on the new earthquake depths and the absence of strong surface deformation, it is possible that the swarm was driven by deep (>10 km BSL) magma intrusion representing an intrusive or protovolcanic segment of the Aleutian arc.

  9. Seismicity and earthquake hazard analysis of the Teton-Yellowstone region, Wyoming

    NASA Astrophysics Data System (ADS)

    White, Bonnie J. Pickering; Smith, Robert B.; Husen, Stephan; Farrell, Jamie M.; Wong, Ivan

    2009-11-01

    Earthquakes of the Teton-Yellowstone region represent a high level of seismicity in the Intermountain west (U.S.A.) that is associated with intraplate extension associated with the Yellowstone hotspot including the nearby Teton and Hebgen Lake faults. The seismicity and the occurrence of high slip-rate late Quaternary faults in this region leads to a high level of seismic hazard that was evaluated using new earthquake catalogues determined from three-dimensional (3-D) seismic velocity models, followed by the estimation of the probabilistic seismic hazard incorporating fault slip and background earthquake occurrence rates. The 3-D P-wave velocity structure of the Teton region was determined using local earthquake data from the Jackson Lake seismic network that operated from 1986-2002. An earthquake catalog was then developed for 1986-2002 for the Teton region using relocated hypocenters. The resulting data revealed a seismically quiescent Teton fault, at M L, local magnitude > 3, with diffuse seismicity in the southern Jackson Hole Valley area but notable seismicity eastward into the Gros Ventre Range. Relocated Yellowstone earthquakes determined by the same methods highlight a dominant E-W zone of seismicity that extends from the aftershock area of the 1959 (M S surface wave magnitude) 7.5 Hebgen Lake, Montana, earthquake along the north side of the 0.64 Ma Yellowstone caldera. Earthquakes are less frequent and shallow beneath the Yellowstone caldera and notably occur along northward trending zones of activity sub-parallel to the post-caldera volcanic vents. Stress-field orientations derived from inversion of focal mechanism data reveal dominant E-W extension across the Teton fault with a NE-SW extension along the northern Teton fault area and southern Yellowstone. The minimum stress axes directions then rotate to E-W extension across the Yellowstone caldera to N-S extension northwest of the caldera and along the Hebgen Lake fault zone. The combination of accurate hypocenters, unified magnitudes, and seismotectonic analysis helped refine the characterization of the background seismicity that was used as input into a probabilistic seismic hazards analysis. Our results reveals the highest seismic hazard is associated with the Teton fault because of its high slip-rate of approximately 1.3 mm/yr compared to the highest rate of 1.4 mm/yr in southern Yellowstone on the Mt. Sheridan fault. This study demonstrates that the Teton-Yellowstone area is among the regions highest seismic hazard in the western U.S.

  10. Seismotectonics of Recent Large Earthquakes at 50 km Depth within Subducted Slabs

    NASA Astrophysics Data System (ADS)

    Ruff, L.; Steinberg, D.; McElroy, B.

    2001-05-01

    The largest earthquakes in most of the world's subduction zones are underthrusting events on the plate interface. The intra-plate seismicity within the subducting oceanic lithosphere is typically less frequent and smaller in size than plate interface seismicity. However, large Wadati-Benioff earthquakes occasionally occur just deeper than the seismogenic plate interface with normal faulting focal mechanisms. Recently, three of these events have occurred in the subduction zones of the eastern Pacific Ocean: the Sept. 30, 1999 Oaxaca event (Mw 7.3); the Jan. 13, 2001 El Salvador event (Mw 7.8); and the Feb. 28, 2001 Puget Sound event (Mw 6.8). While there is considerable variation in the size of these three events, they are all significant events in the context of regional seismicity of their respective subduction zones. Previous global-scale investigations of the space-time occurrence of intermediate-depth slab seismicity have found it difficult to associate the intra-plate events with plate interface seismicity or other tectonic features of subduction zones. In our examination of the seismotectonic setting of these recent events, we note that the three subduction zone segments appear quite different in their characteristics. In particular, Cascadia apparently ruptures in great earthquakes (Mw of about 9) with recurrence intervals of hundreds of years, great earthquakes in Oaxaca (Mw of about 7.8) occur with a relatively short recurrence time, while the El Salvador segment of the Middle America subduction zone is characterized by relatively small plate interface earthquakes. This inverted order of underthrust and intra-slab earthquake sizes does not apply to all subduction zones. Despite the differences in slab geometry and great underthrusting events at Cascadia, Oaxaca, and El Salvador, there are some curious similarities in the occurrence of the slab events. For example, focal depths for the recent three events are in the range from 45 to 55 km, and all three events occurred close to previous large slab events with "recurrence times" that vary from 68 to 19 years. One implication is that while these large slab events are rare in the global sense, their occurrence is not random. It seems that certain "spots" within subducting slabs continue to generate this type of large event.

  11. The Algerian earthquake of October 10, 1980 - a preliminary report.

    USGS Publications Warehouse

    Espinosa, A.F.

    1981-01-01

    The earthquake occurred at 1.25 pm local time and had a surface-wave magnitude of 7.3. The main event was followed by an aftershock 3 hours later with a magnitude of 6.0. The main earthquake epicenter was located 170 km from the capital, Algiers. -from Author

  12. Prediction of Future Great Earthquake Locations from Cumulative Stresses Released by Prior Earthquakes

    NASA Astrophysics Data System (ADS)

    Lee, J.; Hong, T. K.

    2014-12-01

    There are 17 great earthquakes with magnitude greater than or equal to 8.5 in the world since 1900. The great events cause significant damages to the humanity. The prediction of potential maximum magnitudes of earthquakes is important for seismic hazard mitigation. In this study, we calculate the Coulomb stress changes around the active plate margins for 507 events with magnitudes greater than 7.0 during 1976-2013 to estimate the cumulative stress releases. We investigate the spatio-temporal variations of ambient stress field from the cumulative Coulomb stress changes as a function of plate motion speed, plate age and dipping angle. It is observed that the largest stress drop occur in relatively high plate velocity in the convergent margins between Nazca and South American plates, between Pacific and North American plates, between Philippine Sea and Eurasian plates, and between Pacific and Australian plates. It is intriguing to note that the great earthquakes such as Tohoku-Oki earthquake and Maule earthquake occur in the highest plate velocity. On the other hand, the largest stress drop occur in the margins with relatively slow plate speeds such as the boundaries between Cocos and North American plates and between Indo-Australian and Eurasian plates. Earthquakes occur dominantly in the regions with positive Coulomb stress changes, suggesting that post-earthquakes are controlled by the stresses released from prior earthquakes. We find strong positive correlations between Coulomb stress changes and plate speeds. The observation suggests that large stress drop was controlled by high plate speed, suggesting possible prediction of potential maximum magnitudes of events.

  13. Controls of the Xiannvshan Fault on landslides and Reservoir induced earthquakes located at head area of the Three Gorges Reservoir

    NASA Astrophysics Data System (ADS)

    Shimei, Wang; Yeming, Zhang

    2015-04-01

    Landslides and reservoir induced earthquakes are two main types of geological disasters, which have serious influence on the Three Gorges Project. The Xiannvshan Fault is ten kilometers away from the Three Gorges Dam, and it has important control on landslides and earthquakes located at head area of the Three Gorges Reservoir. Data collected show that: (1) the fault stretch runs in northwest-west orientation with a total length of more than 80 kilometers, it north endpoint extends to the Yangtze River and Jiuwanxi Fault is one of its branches. The Xiannvshan Fault has a high level of activity with the average annual decline of 0.076mm in the west wall and the dextral sliding of 0.116mm. (2) Controls on landslides resulted from the Xiannvshan Fault lie in two aspects. One is a large of landslide accumulation bodies resulted from two collapse events, which are corresponded to the two intense faulting. The other is that the Xintan landslide occurred in 1982, which is resulted from the stress accumulation of the fault. (3) The Xiannvshan Fault is active. Three big earthquakes had been induced by the fault from 1959 to the time of impounding, of which one occurred at its southern endpoint, Panjiawan of Yidu, and was magnitude 5, one occurred at its northern section, Zhou Ping, and was magnitude 3.3, and another occurred at Huilongguan of Zigui with a magnitude 5.1. Earthquakes have been happening more frequently after the impoundment of the Three Gorges Reservoir or on the high water level than before. More than 40 earthquakes with magnitudes bigger than 3.3 were recorded after the impoundment, of which 4 ranged from 4.1 to 5.1 and occurred when the high water level was decreasing. Otherwise, most earthquakes centered on the northern endpoint of the fault, which indicates a characteristics of tectonic reservoir earthquake. This study, for the three gorges reservoir area landslide and seismic reservoir prediction is of great significance.

  14. Fractal Dimension of Earthquakes From Relocated Seismicity

    NASA Astrophysics Data System (ADS)

    Nadaeau, R. M.

    2001-12-01

    Fractal dimension (D) describing the distribution of earthquakes has been shown to be a very useful parameter for understanding earthquakes on many levels. Estimates of D have been used to infer the state of stress in Earth's crust, the degree of predictability of earthquakes, scaling relationships for earthquake source parameters recurrence times and b-values, and for estimating kernels used in earthquake hazard estimation. Most estimates of D (D2 and Do) for earthquake distributions are based on earthquake epicentral (2-D) or hypocenters (3-D) locations from standard location catalogs derived using routine location methods. Location uncertainties using these methods are typically on the order of 1 km or more in both relative terms. Relative uncertainties can be viewed as the scatter of earthquakes from their true locations, and in 2 and 3 dimensions this property preferentially increases separation distances (offsets) between events. This imposes serious limitations on the accuracy with which D can be determined, since it limits the usable range of event separations and introduces a bias in D estimates towards larger values by diminishing the numbers of small offsets in favor of larger offsets. Location uncertainties can also mask second order effects in fractal structure such as log-periodic fluctuations indicative of discrete rescaling, hierarchal clustering, and lineations in earthquake quake distributions. In this study, various catalogs of relocated events derived using cross-correlation and double-difference techniques on earthquakes occurring along the SAF system in Central CA are used to estimate D (3-D) and the estimates are compared with those derived using corresponding routine catalogs and relocated catalogs with random scatter added. Implications of the results are discussed. Initial results indicate that D using relocated events is generally between 1 and 1.5, compared to 2 or greater using routine catalogs and relocated catalogs with 1 km of added scatter. The effect of masking second order fractal structure is also observed. The lower values of D suggest a lower stress criticality in Earth's crust in this region and greater predictability of earthquake occurrence. Lower D is also in accordance with scaling relationships derived using repeating earthquakes from this region.

  15. Naturally occurring insecticides.

    PubMed Central

    Soloway, S B

    1976-01-01

    Naturally occurring insecticides are abundant and varied in their effects, though but a few are articles of commerce. Even for these, pyrethrum, nicotine, rotenone, hellebore, ryania, and sabadilla, there is a paucity of information on mammalian toxicology and environmental effects. In general, these materials are characterized favorably by low acute toxicity and ready dissipation in nature. Unfavorable aspects of natural insecticides are the contained mixture of active and inactive components and the low active ingredient content on a crop yield basis pointing to a high unit cost. Natural insecticides can serve additionally as leads to unnatural mimics, of which the commercially successful synthetic pyrethroids are prime examples. The chemical nature, relationship of insecticidal activity to chemical structure, occurrence, production, and utilization, registered uses, metabolism, and insect and mammalian toxicity are reviewed. PMID:789058

  16. Implications for prediction and hazard assessment from the 2004 Parkfield earthquake.

    PubMed

    Bakun, W H; Aagaard, B; Dost, B; Ellsworth, W L; Hardebeck, J L; Harris, R A; Ji, C; Johnston, M J S; Langbein, J; Lienkaemper, J J; Michael, A J; Murray, J R; Nadeau, R M; Reasenberg, P A; Reichle, M S; Roeloffs, E A; Shakal, A; Simpson, R W; Waldhauser, F

    2005-10-13

    Obtaining high-quality measurements close to a large earthquake is not easy: one has to be in the right place at the right time with the right instruments. Such a convergence happened, for the first time, when the 28 September 2004 Parkfield, California, earthquake occurred on the San Andreas fault in the middle of a dense network of instruments designed to record it. The resulting data reveal aspects of the earthquake process never before seen. Here we show what these data, when combined with data from earlier Parkfield earthquakes, tell us about earthquake physics and earthquake prediction. The 2004 Parkfield earthquake, with its lack of obvious precursors, demonstrates that reliable short-term earthquake prediction still is not achievable. To reduce the societal impact of earthquakes now, we should focus on developing the next generation of models that can provide better predictions of the strength and location of damaging ground shaking. PMID:16222291

  17. Absence of remotely triggered large earthquakes beyond the mainshock region

    USGS Publications Warehouse

    Parsons, T.; Velasco, A.A.

    2011-01-01

    Large earthquakes are known to trigger earthquakes elsewhere. Damaging large aftershocks occur close to the mainshock and microearthquakes are triggered by passing seismic waves at significant distances from the mainshock. It is unclear, however, whether bigger, more damaging earthquakes are routinely triggered at distances far from the mainshock, heightening the global seismic hazard after every large earthquake. Here we assemble a catalogue of all possible earthquakes greater than M 5 that might have been triggered by every M 7 or larger mainshock during the past 30 years. We compare the timing of earthquakes greater than M 5 with the temporal and spatial passage of surface waves generated by large earthquakes using a complete worldwide catalogue. Whereas small earthquakes are triggered immediately during the passage of surface waves at all spatial ranges, we find no significant temporal association between surface-wave arrivals and larger earthquakes. We observe a significant increase in the rate of seismic activity at distances confined to within two to three rupture lengths of the mainshock. Thus, we conclude that the regional hazard of larger earthquakes is increased after a mainshock, but the global hazard is not.

  18. The 2005 Tarapaca earthquake: a likely indirect trigger of the 2014 Iquique earthquake

    NASA Astrophysics Data System (ADS)

    Bie, Lidong; Ryder, Isabelle

    2015-04-01

    Static stress change has been proposed as an integral earthquake triggering mechanism. Here we investigate the effect of 2005 Tarapaca earthquake on the occurrence of the 2014 M8.1 Iquique earthquake from the static stress change triggering perspective. The 2005 Mw7.8 Tarapaca earthquake occurred ~200 km to east of the Iquique earthquake and was identified as a result of normal faulting on a west-dipping plane at depths between 90 and 115 km within the subducting slab of northern Chile (Delouis and Legrand, 2007). It is supposed that the induced coseismic stress could be gradually released by any nearby weak layers. Before calculating the Coulomb stress changes associated with the coseismic slip and postseismic processes, we first need to constrain the subduction zone rheological properties. We built a postseismic deformation rate map for the Tarapaca earthquake using 45 atmospheric noise corrected interferograms. The Envisat-recorded short-term postseismic deformation shows a broad pattern of uplift across the fault's surface projection. A semi-analytical three-dimensional model considering the vertical and horizontal rheological heterogeneities was tested with variable inputs to obtain a set of optimal rheological parameters. With the optimal rheological parameters as input, we then compute the static Coulomb stress change on the megathrust interface caused by the coseismic slip and viscoelastic relaxation (VER) processes of the Tarapaca earthquake. It is found that the coseismic rupture and most aftershocks of the Iquique earthquake locate in a zone with negative stress loading. However, calculation of Coulomb stress change on nodal planes of the M6.7 preshock shows a positive loading on the shallow dipping fault plane, which indicates a likely triggering effect on the preshock. Based on the understanding that the preshock triggered the mainshock, we suggest that the 2005 Tarapaca earthquake may act as an indirect trigger of the 2014 Iquique earthquake.

  19. Integrated Simulation of Earthquake Generation and Ground Motion and Tsunami for Nankai Trough Megathrust Earthquakes

    NASA Astrophysics Data System (ADS)

    Todoriki, M.; Hyodo, M.; Hori, T.; Furumura, T.; Maeda, T.

    2014-12-01

    We have conducted an integrated simulation of earthquake generation and seismic ground motion and tsunami for realizing a realistic earthquake scenario for large earthquakes along the Nankai Trough in southwest Japan where large earthquakes have repeatedly occurred with the recurrence interval of 100-150 years. The understanding of diversity of the characteristics of the huge earthquakes and their seismic and tsunami hazards are quite important issue. Various earthquake cycle simulations have been recently performed to estimate the diversity of the patterns of the huge earthquakes in the trough and the possibility of the future earthquakes, where the fault rupture propagation process and the friction in a plate boundary are considered. Here, we integrated these two simulations by one-way weakly coupled approach; First we conduct the quasi-dynamic earthquake cycle simulation, then the resultant time-dependent heterogeneous slip histories on the plate boundary are smoothly connected to as inputs of the ground motion and tsunami simulation. As a trial of this approach, the integrated simulation was performed under the huge earthquake scenario with large fault rupture area very similar to the 1707 Hoei earthquake. The target volume of the latter simulation is 1,200 km (EW) x 1,000 km (NS) x 250 km (depth). The equations of motion for viscoelastic body were solved by finite-difference method with discretization of 0.5 km and 0.25 km in horizontal and vertical direction, respectively. For such large-scale simulation the K computer at the AICS, RIKEN was utilized with 2,400 CPUs. The computation time was approx. 1 hour for 80,000 time steps calculation. The results of the integrated simulation show that we successfully reproduced a series of phenomena from earthquake generation to seismic wave propagation, strong ground motion in land, and tsunami growth. Moreover, we confirmed seismic wave generation accompanied by the heterogeneous fault rupture propagation on the plate boundary and the features of the subsequent ground motion on earth surface. It is expected that the high-performance computing of the integrated system enables us to investigate diversity of the seismic and tsunami hazards of huge earthquakes in southwestern Japan as well as their complexity of earthquake generation itself based on physical models.

  20. Psychological Intervention in Primary Care After Earthquakes in Lorca, Spain

    PubMed Central

    Garriga, Ascensin; Egea, Carmen

    2015-01-01

    Objective: After the earthquakes that occurred in Lorca, Spain, on May 11, 2011, the regional mental health management employed 2 clinical psychologists for 6 months to provide care to people referred by primary care physicians. The objective was to address the expected increased demand for treatment of mental disorders, notably posttraumatic stress disorder (PTSD) and adjustment disorders. Method: Referred individuals were evaluated and treated according to a clinical protocol designed ad hoc from June 12, 2011, to November 30, 2011. The protocol provided a stepped intervention guided by clinical and psychometric assessment using normalization for those with no psychiatric diagnosis, brief group treatment for mild to moderate PTSD or adjustment disorders, individual treatment for more severe PTSD, and referral to the local mental health center for other mental health disorders. Standard adult and child scales to assess posttraumatic, depression, and anxiety symptoms and resilience were used at initial assessment to guide treatment allocation and repeated to assess outcome status. Psychologists also provided a clinical assessment of symptom resolution at the end of the study. Results: Rates of symptom resolution and improvements on all scales (PTSD, depression, anxiety, and resilience) demonstrated clinically and statistically significant improvement in all treatment groups (P = .000). Dropout was low. Medications were prescribed frequently to adults; no child received medication as a result of the earthquakes. No case of mental disorder related to the earthquakes was referred to the local mental health center during the 6 months of psychologist intervention. Conclusion:The structured intervention resulted in a high resolution of cases and low dropout, allowing treatment of a larger number of people with optimal frequency (weekly), devoting more time to the most severe cases and less to those moderately or mildly affected. PMID:26137356

  1. Structural geometry of the source region for the 2013 Mw 6.6 Lushan earthquake: Implication for earthquake hazard assessment along the Longmen Shan

    NASA Astrophysics Data System (ADS)

    Li, Yiquan; Jia, Dong; Wang, Maomao; Shaw, John H.; He, Jiankun; Lin, Aiming; Xiong, Lin; Rao, Gang

    2014-03-01

    The 2013 Mw 6.6 Lushan earthquake occurred in the Longmen Shan fold-and-thrust belt, Sichuan Province, China, near the five-year anniversary of the devastating 2008 Mw 7.8 Wenchuan earthquake. To define the fault that generated the 2013 earthquake and its relationship with the Beichuan fault, which ruptured in the Wenchuan earthquake, we construct several cross sections and a 3D structural model. The sections and models reveal that the main-shock of the Lushan earthquake occurred on a portion of the Range Front blind thrust (RFBT) and that the structural geometry of this fault varies along strike. The Lushan main-shock occurred at a location along the strike of the fault where the geologic shortening and total fault slip are greatest. A lateral ramp of the RFBT appears to coincide with the northern limit of aftershocks from the Lushan earthquake, leading to a 75 km seismic gap between the Wenchuan earthquake and the 2013 earthquake sequence. Although both the Wenchuan and Lushan earthquakes occurred within the Longmen Shan fold-and-thrust belt, different faults generated the two events. Based on this structural characterization and analysis of the aftershocks of the Wenchuan and Lushan earthquakes, we suggest that the Lushan earthquake may have been triggered by the 2008 rupture but is best considered as an independent event rather than an aftershock of the Wenchuan earthquake. The RFBT that generated the Lushan earthquake is linked to a detachment that extends into the Sichuan basin along the Triassic evaporite layer. The coulomb stress change simulation suggests that other faults linked to this detachment may have been loaded by the 2008 and 2013 earthquake, posing the risk of future earthquakes along the Longmen Shan and in the densely populated Sichuan basin.

  2. Earthquake Hazard in the Heart of the Homeland

    USGS Publications Warehouse

    Gomberg, Joan; Schweig, Eugene

    2007-01-01

    Evidence that earthquakes threaten the Mississippi, Ohio, and Wabash River valleys of the Central United States abounds. In fact, several of the largest historical earthquakes to strike the continental United States occurred in the winter of 1811-1812 along the New Madrid seismic zone, which stretches from just west of Memphis, Tenn., into southern Illinois. Several times in the past century, moderate earthquakes have been widely felt in the Wabash Valley seismic zone along the southern border of Illinois and Indiana. Throughout the region, between 150 and 200 earthquakes are recorded annually by a network of monitoring instruments, although most are too small to be felt by people. Geologic evidence for prehistoric earthquakes throughout the region has been mounting since the late 1970s. But how significant is the threat? How likely are large earthquakes and, more importantly, what is the chance that the shaking they cause will be damaging?

  3. Real-time earthquake monitoring using a search engine method.

    PubMed

    Zhang, Jie; Zhang, Haijiang; Chen, Enhong; Zheng, Yi; Kuang, Wenhuan; Zhang, Xiong

    2014-01-01

    When an earthquake occurs, seismologists want to use recorded seismograms to infer its location, magnitude and source-focal mechanism as quickly as possible. If such information could be determined immediately, timely evacuations and emergency actions could be undertaken to mitigate earthquake damage. Current advanced methods can report the initial location and magnitude of an earthquake within a few seconds, but estimating the source-focal mechanism may require minutes to hours. Here we present an earthquake search engine, similar to a web search engine, that we developed by applying a computer fast search method to a large seismogram database to find waveforms that best fit the input data. Our method is several thousand times faster than an exact search. For an Mw 5.9 earthquake on 8 March 2012 in Xinjiang, China, the search engine can infer the earthquake's parameters in <1 s after receiving the long-period surface wave data. PMID:25472861

  4. Study of tectonic earthquake precursors by geodetic methods

    SciTech Connect

    Sigalov, V.M.

    1985-02-01

    Deformations of the Earth's surface which can be revealed by geodetic methods are among the most reliable earthquake precursors. A brief list is presented of geodetic leveling methods which have revealed the precursors of several earthquakes. To confirm the accuracy of determination of precursors of earthquakes based on the results of repeated leveling in epicenter zones and observations at Alma-Ata, the magnitudes of 7 earthquakes which occurred in northern Tien Shan during measurement of tectonic precursors were calculated and compared to valves based on seismologic measurements. The agreement found is satisfactory. A scientifically well-founded program of tectonic movements by geodetic methods in the northern Tien Shan has thus established the presence of tectonic precursors of earthquakes, determined the distances over which they are manifested and shown the possiblity of using the results of geodetic measurements in combiantion with geophysical and seismologic data to estimate the possible time of appearance of earthquake precursors.

  5. Source parameters of a M4.8 and its accompanying repeating earthquakes off Kamaishi, NE Japan: Implications for the hierarchical structure of asperities and earthquake cycle

    NASA Astrophysics Data System (ADS)

    Uchida, Naoki; Matsuzawa, Toru; Ellsworth, William L.; Imanishi, Kazutoshi; Okada, Tomomi; Hasegawa, Akira

    2007-10-01

    We determine the source parameters of a M4.9 +/- 0.1 `characteristic earthquake' sequence and its accompanying microearthquakes at ~50 km depth on the subduction plate boundary offshore of Kamaishi, NE Japan. The microearthquakes tend to occur more frequently in the latter half of the recurrence intervals of the M4.9 +/- 0.1 events. Our results show that the microearthquakes are repeating events and they are located not only around but also within the slip area for the 2001 M4.8 event. From the hierarchical structure of slip areas and smaller stress drops for the microearthquakes compared to the M4.8 event, we infer the small repeating earthquakes rupture relatively weak patches in and around the slip area for the M4.8 event and their activity reflects a stress concentration process and/or change in frictional property (healing) at the area. We also infer the patches for the M4.9 +/- 0.1 and other repeating earthquakes undergo aseismic slip during their interseismic period.

  6. Source parameters of a M4.8 and its accompanying repeating earthquakes off Kamaishi, NE Japan: Implications for the hierarchical structure of asperities and earthquake cycle

    USGS Publications Warehouse

    Uchida, N.; Matsuzawa, T.; Ellsworth, W.L.; Imanishi, K.; Okada, T.; Hasegawa, A.

    2007-01-01

    We determine the source parameters of a M4.9 ?? 0.1 'characteristic earthquake' sequence and its accompanying microearthquakes at ???50 km depth on the subduction plate boundary offshore of Kamaishi, NE Japan. The microearthquakes tend to occur more frequently in the latter half of the recurrence intervals of the M4.9 ?? 0.1 events. Our results show that the microearthquakes are repeating events and they are located not only around but also within the slip area for the 2001 M4.8 event. From the hierarchical structure of slip areas and smaller stress drops for the microearthquakes compared to the M4.8 event, we infer the small repeating earthquakes rupture relatively weak patches in and around the slip area for the M4.8 event and their activity reflects a stress concentration process and/or change in frictional property (healing) at the area. We also infer the patches for the M4.9 ?? 0.1 and other repeating earthquakes undergo aseismic slip during their interseismic period. Copyright 2007 by the American Geophysical Union.

  7. High performance simulations for transformational earthquake risk assessments

    NASA Astrophysics Data System (ADS)

    McCallen, D. B.; Larsen, S. C.

    2009-07-01

    Earthquakes occurring around the world are responsible for extensive loss of life and infrastructure damage. On average, 1100 earthquakes with significant damage potential occur world-wide per year, and a major societal challenge is to design a human environment that contains appropriate earthquake resistance. Design of critical infrastructure such as large buildings, bridges, industrial facilities and nuclear power plants in seismically active regions is a significant scientific and engineering challenge that encompasses the multiple disciplines of geophysics, geotechnical and structural engineering. Because of the great complexities in earthquake physical processes, traditional approaches to seismic hazard assessment have relied heavily on historical earthquake observations. In this approach, observational data from many locations is homogenized into an empirical assessment of earthquake hazard at any specific site of interest. With major advancements in high performance computing platforms and algorithms, it is now possible to utilize physics-based predictive models to gain enhanced insight about site-specific earthquake ground motions and infrastructure response. This paper discusses recent advancements in geophysics and infrastructure simulations and future challenges in implementing advanced simulations for both earthquake hazard (future ground motions) and earthquake risk (infrastructure response and damage) assessments.

  8. Advance earthquake warnings

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    Urban centers can receive a 15-to-30-second advance warning about impending earthquakes if several technical criteria are met, according to a study by Ta-liang (Leon) Teng of the Southern California Earthquake Center and Yih-Min Wu of the Taiwan Central Weather Bureau. The study is published in the Bulletin of the Seismological Society of America, vol. 92, no. 5, June 2002).Teng and Wu's system for developing early warnings for earthquakes relies on data from a "virtual sub-network" automatically established when an earthquake triggers a group of nearby seismic stations. That information can then be immediately distributed as an early warning.

  9. Earthquakes and Plate Boundaries

    ERIC Educational Resources Information Center

    Lowman, Paul; And Others

    1978-01-01

    Contains the contents of the Student Investigation booklet of a Crustal Evolution Education Project (CEEP) instructional modules on earthquakes. Includes objectives, procedures, illustrations, worksheets, and summary questions. (MA)

  10. Are Earthquake Magnitudes Clustered?

    SciTech Connect

    Davidsen, Joern; Green, Adam

    2011-03-11

    The question of earthquake predictability is a long-standing and important challenge. Recent results [Phys. Rev. Lett. 98, 098501 (2007); ibid.100, 038501 (2008)] have suggested that earthquake magnitudes are clustered, thus indicating that they are not independent in contrast to what is typically assumed. Here, we present evidence that the observed magnitude correlations are to a large extent, if not entirely, an artifact due to the incompleteness of earthquake catalogs and the well-known modified Omori law. The latter leads to variations in the frequency-magnitude distribution if the distribution is constrained to those earthquakes that are close in space and time to the directly following event.

  11. On the reported magnetic precursor of the 1989 Loma Prieta earthquake

    USGS Publications Warehouse

    Thomas, J.N.; Love, J.J.; Johnston, M.J.S.

    2009-01-01

    Among the most frequently cited reports in the science of earthquake prediction is that by Fraser-Smith et al. (1990) and Bernardi et al. (1991). They found anomalous enhancement of magnetic-field noise levels prior to the 18 October 1989 Loma Prieta earthquake in the ultra-low-frequency range (0.0110-10.001 Hz) from a ground-based sensor at Corralitos, CA, just 7 km from the earthquake epicenter. In this analysis, we re-examine all of the available Corralitos data (21 months from January 1989 to October 1990) and the logbook kept during this extended operational period. We also examine 1.0-Hz (1-s) data collected from Japan, 0.0167-Hz (1-min) data collected from the Fresno, CA magnetic observatory, and the global Kp magnetic-activity index. The Japanese data are of particular importance since their acquisition rate is sufficient to allow direct comparison with the lower-frequency bands of the Corralitos data. We identify numerous problems in the Corralitos data, evident from both straightforward examination of the Corralitos data on their own and by comparison with the Japanese and Fresno data sets. The most notable problems are changes in the baseline noise levels occurring during both the reported precursory period and at other times long before and after the earthquake. We conclude that the reported anomalous magnetic noise identified by Fraser-Smith et al. and Bernardi et al. is not related to the Loma Prieta earthquake but is an artifact of sensor-system malfunction. ?? 2008 Elsevier B.V.

  12. Activated Very Low Frequency Earthquakes By the Slow Slip Events in the Ryukyu Subduction Zone

    NASA Astrophysics Data System (ADS)

    Nakamura, M.; Sunagawa, N.

    2014-12-01

    The Ryukyu Trench (RT), where the Philippine Sea plate is subducting, has had no known thrust earthquakes with a Mw>8.0 in the last 300 years. However, the rupture source of the 1771 tsunami has been proposed as an Mw > 8.0 earthquake in the south RT. Based on the dating of tsunami boulders, it has been estimated that large tsunamis occur at intervals of 150-400 years in the south Ryukyu arc (RA) (Araoka et al., 2013), although they have not occurred for several thousand years in the central and northern Ryukyu areas (Goto et al., 2014). To address the discrepancy between recent low moment releases by earthquakes and occurrence of paleo-tsunamis in the RT, we focus on the long-term activity of the very low frequency earthquakes (VLFEs), which are good indicators of the stress release in the shallow plate interface. VLFEs have been detected along the RT (Ando et al., 2012), which occur on the plate interface or at the accretionary prism. We used broadband data from the F-net of NIED along the RT and from the IRIS network. We applied two filters to all the raw broadband seismograms: a 0.02-0.05 Hz band-pass filter and a 1 Hz high-pass filter. After identification of the low-frequency events from the band-pass-filtered seismograms, the local and teleseismic events were removed. Then we picked the arrival time of the maximum amplitude of the surface wave of the VLFEs and determined the epicenters. VLFEs occurred on the RA side within 100 km from the trench axis along the RT. Distribution of the 6670 VLFEs from 2002 to 2013 could be divided to several clusters. Principal large clusters were located at 27.1-29.0N, 25.5-26.6N, and 122.1-122.4E (YA). We found that the VLFEs of the YA are modulated by repeating slow slip events (SSEs) which occur beneath south RA. The activity of the VLFEs increased to two times of its ordinary rate in 15 days after the onset of the SSEs. Activation of the VLFEs could be generated by low stress change of 0.02-20 kPa increase in Coulomb failure stress. The strain in the plate interface where the VLFEs occur frequently would be released by small change in stress. Cluster of the VLFEs is complementally to the historical tsunami source area and locked area. Continuous activity of VLFEs would release the stress patchily in the plate interface and give the constraint to the maximum size of large thrust earthquakes.

  13. Naturally Occurring Food Toxins

    PubMed Central

    Dolan, Laurie C.; Matulka, Ray A.; Burdock, George A.

    2010-01-01

    Although many foods contain toxins as a naturally-occurring constituent or, are formed as the result of handling or processing, the incidence of adverse reactions to food is relatively low. The low incidence of adverse effects is the result of some pragmatic solutions by the US Food and Drug Administration (FDA) and other regulatory agencies through the creative use of specifications, action levels, tolerances, warning labels and prohibitions. Manufacturers have also played a role by setting limits on certain substances and developing mitigation procedures for process-induced toxins. Regardless of measures taken by regulators and food producers to protect consumers from natural food toxins, consumption of small levels of these materials is unavoidable. Although the risk for toxicity due to consumption of food toxins is fairly low, there is always the possibility of toxicity due to contamination, overconsumption, allergy or an unpredictable idiosyncratic response. The purpose of this review is to provide a toxicological and regulatory overview of some of the toxins present in some commonly consumed foods, and where possible, discuss the steps that have been taken to reduce consumer exposure, many of which are possible because of the unique process of food regulation in the United States. PMID:22069686

  14. Earthquake Breccias (Invited)

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Melosh, B. L.; Lamothe, K.; Schnitzer, V.; Bate, C.

    2013-12-01

    Fault breccias are one of the fundamental classes of fault rocks and are observed in many exhumed faults. Some breccias have long been assumed to form co-seismically, but textural or mechanistic evidence for the association with earthquakes has never been documented. For example, at dilational jogs in brittle faults, it is common to find small bodies of chaotic breccia in lenticular or rhombohedral voids bounded by main slip surfaces and linking segments. Sibson interpreted these 'implosion breccias' as evidence of wall rock fracturing during sudden unloading when the dilational jogs open during earthquake slip (Sibson 1985, PAGEOPH v. 124, n. 1, 159-175). However, the role of dynamic fracturing in forming these breccias has not been tested. Moreover, the criteria for identifying implosion breccia have not been defined - do all breccias in dilational jogs or step-overs represent earthquake slip? We are building a database of breccia and microbreccia textures to develop a strictly observational set of criteria for distinction of breccia texture classes. Here, we present observations from the right-lateral Pofadder Shear Zone, South Africa, and use our textural criteria to identify the relative roles of dynamic and quasi-static fracture patterns, comminution/grinding and attrition, hydrothermal alteration, dissolution, and cementation. Nearly 100% exposure in the hyper-arid region south of the Orange River allowed very detailed mapping of frictional fault traces associated with rupture events, containing one or more right-steps in each rupture trace. Fracture patterns characteristic of on- and off-fault damage associated with propagation of dynamic rupture are observed along straight segments of the faults. The wall rock fractures are regularly spaced, begin at the fault trace and propagate at a high angle to the fault, and locally branch into subsidiary fractures before terminating a few cm away. This pattern of fractures has been previously linked to dynamic fracture tip propagation in both field studies and analog experiments. In dilational jogs, these fractures interact and intersect the wall rock foliation to cut the wall rock into distinctive clast shapes and sizes, giving the breccia a characteristic texture that can be defined quantitatively by image analysis. Breccia clast morphology, size distribution and angularity are markers for dynamic fracture patterns. Older microbreccias are cemented, and interfingering grain boundaries between quartz in clasts and quartz in cement show that crystal plastic deformation of quartz has occurred after breccia cementation. These deformed breccias are cut by younger breccias, establishing cyclicity of brittle and ductile slip on the Pofadder Shear Zone. Our results distinguish between fault breccias that could have formed quasi-statically, and those that are the result of dynamic processes and therefore define a new tool for recognizing earthquakes in the rock record.

  15. Post-earthquake building safety assessments for the Canterbury Earthquakes

    USGS Publications Warehouse

    Marshall, J.; Barnes, J.; Gould, N.; Jaiswal, K.; Lizundia, B.; Swanson, David A.; Turner, F.

    2012-01-01

    This paper explores the post-earthquake building assessment program that was utilized in Christchurch, New Zealand following the Canterbury Sequence of earthquakes beginning with the Magnitude (Mw.) 7.1 Darfield event in September 2010. The aftershocks or triggered events, two of which exceeded Mw 6.0, continued with events in February and June 2011 causing the greatest amount of damage. More than 70,000 building safety assessments were completed following the February event. The timeline and assessment procedures will be discussed including the use of rapid response teams, selection of indicator buildings to monitor damage following aftershocks, risk assessments for demolition of red-tagged buildings, the use of task forces to address management of the heavily damaged downtown area and the process of demolition. Through the post-event safety assessment program that occurred throughout the Canterbury Sequence of earthquakes, many important lessons can be learned that will benefit future response to natural hazards that have potential to damage structures.

  16. A century of induced earthquakes in Oklahoma?

    USGS Publications Warehouse

    Hough, Susan E.; Page, Morgan T.

    2015-01-01

    Seismicity rates have increased sharply since 2009 in the central and eastern United States, with especially high rates of activity in the state of Oklahoma. Growing evidence indicates that many of these events are induced, primarily by injection of wastewater in deep disposal wells. The upsurge in activity has raised two questions: What is the background rate of tectonic earthquakes in Oklahoma? How much has the rate varied throughout historical and early instrumental times? In this article, we show that (1) seismicity rates since 2009 surpass previously observed rates throughout the twentieth century; (2) several lines of evidence suggest that most of the significant earthquakes in Oklahoma during the twentieth century were likely induced by oil production activities, as they exhibit statistically significant temporal and spatial correspondence with disposal wells, and intensity measurements for the 1952 El Reno earthquake and possibly the 1956 Tulsa County earthquake follow the pattern observed in other induced earthquakes; and (3) there is evidence for a low level of tectonic seismicity in southeastern Oklahoma associated with the Ouachita structural belt. The 22 October 1882 Choctaw Nation earthquake, for which we estimate Mw 4.8, occurred in this zone.

  17. Landslides triggered by the earthquake

    SciTech Connect

    Harp, E.L.; Keefer, D.K.

    1990-01-01

    The May 2 earthquake triggered landslides numbering in the thousands. Most numerous were rockfalls and rockslides that occurred mainly on slopes steeper than 60{degree} within sandstone, siltstone, and shale units of Upper Cretaceous and Tertiary strata. Soil falls from cutbank slopes along streams were also numerous. Seven slumps in natural slopes were triggered, and minor liquefaction-induced lateral-spread failures occurred along Los Gatos Creek. Rockfalls and rockslides occurred as far as 34 km northwest, 15 km south, and 26 km southwest of the epicenter. There were few slope failures to the east of the epicenter, owing to the absence of steep slopes in that direction. Throughout the area affected, rockfalls and rockslides were concentrated on southwest-facing slopes; the failures on slopes facing in the southwest quadrant accounted for as much as 93% of all failures in some areas. Rockfalls and rockslides from ridge crests were predominantly from sandstone units. Along steeply incised canyons, however, failures in shale and siltstone units were also common. Small rockslides and soil slides occurred from cut slopes above oil-well pump pads in the oil fields; slumps were common in the outer parts of steep fill slopes of the pump pads. The distribution of seismically induced landslides throughout the entire earthquake-affected area was mapped from true-color airphotos taken on May 3, 1985.

  18. Clustered and transient earthquake sequences in mid-continents

    NASA Astrophysics Data System (ADS)

    Liu, M.; Stein, S. A.; Wang, H.; Luo, G.

    2012-12-01

    Earthquakes result from sudden release of strain energy on faults. On plate boundary faults, strain energy is constantly accumulating from steady and relatively rapid relative plate motion, so large earthquakes continue to occur so long as motion continues on the boundary. In contrast, such steady accumulation of stain energy does not occur on faults in mid-continents, because the far-field tectonic loading is not steadily distributed between faults, and because stress perturbations from complex fault interactions and other stress triggers can be significant relative to the slow tectonic stressing. Consequently, mid-continental earthquakes are often temporally clustered and transient, and spatially migrating. This behavior is well illustrated by large earthquakes in North China in the past two millennia, during which no single large earthquakes repeated on the same fault segments, but moment release between large fault systems was complementary. Slow tectonic loading in mid-continents also causes long aftershock sequences. We show that the recent small earthquakes in the Tangshan region of North China are aftershocks of the 1976 Tangshan earthquake (M 7.5), rather than indicators of a new phase of seismic activity in North China, as many fear. Understanding the transient behavior of mid-continental earthquakes has important implications for assessing earthquake hazards. The sequence of large earthquakes in the New Madrid Seismic Zone (NMSZ) in central US, which includes a cluster of M~7 events in 1811-1812 and perhaps a few similar ones in the past millennium, is likely a transient process, releasing previously accumulated elastic strain on recently activated faults. If so, this earthquake sequence will eventually end. Using simple analysis and numerical modeling, we show that the large NMSZ earthquakes may be ending now or in the near future.

  19. Fault plane parameters of Sanhe-Pinggu M8 earthquake in 1679 determined using present-day small earthquakes

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoshan; Feng, Xiangdong; Xu, Xiwei; Diao, Guiling; Wan, Yongge; Wang, Libin; Ma, Guangqing

    2014-12-01

    The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area. We relocated those earthquakes with the double-difference method. Based on the assumption that clustered small earthquakes often occur in the vicinity of fault plane of large earthquake, and referring to the morphology of the long axis of the isoseismal line obtained by the predecessors, we selected a strip-shaped zone from the relocated earthquake catalog in the period from 1980 to 2009 to invert fault plane parameters of this earthquake. The inversion results are as follows: the strike is 38.23, the dip angle is 82.54, the slip angle is -156.08, the fault length is about 80 km, the lower-boundary depth is about 23 km and the buried depth of upper boundary is about 3 km. This shows that the seismogenic fault is a NNE-trending normal dip-slip fault, southeast wall downward and northwest wall uplift, with the right-lateral strike-slip component. Moreover, the surface rupture zone, intensity distribution of the earthquake and seismic-wave velocity profile in the focal area all verified our study result.

  20. Seismic and Geodetic Investigation of the 1996-1998 Earthquake Swarm at Strandline Lake, Alaska

    NASA Astrophysics Data System (ADS)

    Kilgore, W.; Roman, D. C.; Power, J. A.; Hansen, R. A.; Biggs, J.

    2009-12-01

    Microearthquake (< M3.0) swarms occur frequently in volcanic environments, but do not always culminate in an eruption. Such non-eruptive swarms may be caused by stresses induced by magma intrusion, hydrothermal fluid circulation, or regional tectonic processes, such as slow-slip earthquakes. Strandline Lake, located 30 km northeast of Mount Spurr volcano in south-central Alaska, experienced a strong earthquake swarm between August 1996 and August 1998. The Alaska Volcano Observatory (AVO) catalog indicates that a total of 2,999 earthquakes were detected during the swarm period, with a maximum magnitude of Mw 3.1 and a depth range of 0-30 km below sea level (with the majority of catalog hypocenters located between 5-10 km BSL). The cumulative seismic moment of the swarm was 2.03e15 N m, equivalent to a cumulative magnitude of Mw 4.2. Because of the swarm's distance from the nearest Holocene volcanic vent, seismic monitoring was poor and gas and deformation data for the swarm period do not exist. However, combined waveforms from a dense seismic network on Mount Spurr and from several regional seismic stations allowed us to re-analyze the swarm earthquakes. We first developed a new 1-D velocity model for the Strandline Lake region by re-picking and inverting precise arrival times for 27 large Strandline Lake earthquakes. The new velocity model reduced the average RMS for these earthquakes from 0.16 to 0.11s, and the average horizontal and vertical location errors from 3.3 to 2.5 km and 4.7 to 3.0 km, respectively. Depths of the 27 earthquakes ranged from 10.5 to 22.1 km with an average depth of 16.6 km. A moderately high b-value of 1.33 was determined for the swarm period, possibly indicative of magmatic activity. However, a similarly high b-value of 1.25 was calculated for the background period. 28 well-constrained fault plane solutions for both swarm and background earthquakes indicate a diverse mixture of strike-slip, dip-slip, and reverse faulting beneath Strandline Lake. Finally, 8 Interferometric Synthetic Aperture Radar (InSAR) images spanning the swarm period unambiguously show no evidence of surface deformation. While a shallow volcanic intrusion appears to be an unlikely cause of the Strandline Lake swarm based on our new well-constrained earthquake depths and the absence of strong surface deformation, the depth range of 10.5 and 22.1 km for relocated earthquakes and the high degree of FPS heterogeneity for this swarm are similar to an earthquake swarm beneath Lake Tahoe, California in 2003 caused by a deep intrusion near the base of the crust (Smith et al, 2004, Science 305,1277-1280). This similarity suggests that a deep crustal magmatic intrusion could have occurred beneath the Strandline Lake area in 1997 and may have been responsible for the resulting microearthquake activity.

  1. Continuing Megathrust Earthquake Potential in northern Chile after the 2014 Iquique Earthquake Sequence

    NASA Astrophysics Data System (ADS)

    Hayes, G. P.; Herman, M. W.; Barnhart, W. D.; Furlong, K. P.; Riquelme, S.; Benz, H.; Bergman, E.; Barrientos, S. E.; Earle, P. S.; Samsonov, S. V.

    2014-12-01

    The seismic gap theory, which identifies regions of elevated hazard based on a lack of recent seismicity in comparison to other portions of a fault, has successfully explained past earthquakes and is useful for qualitatively describing where future large earthquakes might occur. A large earthquake had been expected in the subduction zone adjacent to northern Chile, which until recently had not ruptured in a megathrust earthquake since a M~8.8 event in 1877. On April 1 2014, a M 8.2 earthquake occurred within this northern Chile seismic gap, offshore of the city of Iquique; the size and spatial extent of the rupture indicate it was not the earthquake that had been anticipated. Here, we present a rapid assessment of the seismotectonics of the March-April 2014 seismic sequence offshore northern Chile, including analyses of earthquake (fore- and aftershock) relocations, moment tensors, finite fault models, moment deficit calculations, and cumulative Coulomb stress transfer calculations over the duration of the sequence. This ensemble of information allows us to place the current sequence within the context of historic seismicity in the region, and to assess areas of remaining and/or elevated hazard. Our results indicate that while accumulated strain has been released for a portion of the northern Chile seismic gap, significant sections have not ruptured in almost 150 years. These observations suggest that large-to-great sized megathrust earthquakes will occur north and south of the 2014 Iquique sequence sooner than might be expected had the 2014 events ruptured the entire seismic gap.

  2. Tremor, remote triggering and earthquake cycle

    NASA Astrophysics Data System (ADS)

    Peng, Z.

    2012-12-01

    Deep tectonic tremor and episodic slow-slip events have been observed at major plate-boundary faults around the Pacific Rim. These events have much longer source durations than regular earthquakes, and are generally located near or below the seismogenic zone where regular earthquakes occur. Tremor and slow-slip events appear to be extremely stress sensitive, and could be instantaneously triggered by distant earthquakes and solid earth tides. However, many important questions remain open. For example, it is still not clear what are the necessary conditions for tremor generation, and how remote triggering could affect large earthquake cycle. Here I report a global search of tremor triggered by recent large teleseismic earthquakes. We mainly focus on major subduction zones around the Pacific Rim. These include the southwest and northeast Japan subduction zones, the Hikurangi subduction zone in New Zealand, the Cascadia subduction zone, and the major subduction zones in Central and South America. In addition, we examine major strike-slip faults around the Caribbean plate, the Queen Charlotte fault in northern Pacific Northwest Coast, and the San Andreas fault system in California. In each place, we first identify triggered tremor as a high-frequency non-impulsive signal that is in phase with the large-amplitude teleseismic waves. We also calculate the dynamic stress and check the triggering relationship with the Love and Rayleigh waves. Finally, we calculate the triggering potential with the local fault orientation and surface-wave incident angles. Our results suggest that tremor exists at many plate-boundary faults in different tectonic environments, and could be triggered by dynamic stress as low as a few kPas. In addition, we summarize recent observations of slow-slip events and earthquake swarms triggered by large distant earthquakes. Finally, we propose several mechanisms that could explain apparent clustering of large earthquakes around the world.

  3. The Magnitude and Energy of Large Earthquakes

    NASA Astrophysics Data System (ADS)

    Purcaru, G.

    2003-12-01

    Several magnitudes were introduced to quantify large earthquakes better and more comprehensive than Ms: Mw (moment magnitude; Kanamori, 1977), ME (strain energy magnitude; Purcaru and Berckhemer, 1978), Mt (tsunami magnitude; Abe, 1979), Mm (mantle magnitude; Okal and Talandier, 1985), Me (seismic energy magnitude; Choy and Boatwright, 1995). Although these magnitudes are still subject to different uncertainties, various kinds of earthquakes can now be better understood in terms or combinations of them. They can also be viewd as mappings of basic source parameters: seismic moment, strain energy, seismic energy, stress drop, under certain assumptions or constraints. We studied a set of about 90 large earthquakes (shallow and deeper) occurred in different tectonic regimes, with more reliable source parameters, and compared them in terms of the above magnitudes. We found large differences between the strain energy (mapped to ME) and seismic energy (mapped to Me), and between ME of events with about the same Mw. This confirms that no 1-to-1 correspondence exists between these magnitudes (Purcaru, 2002). One major cause of differences for "normal" earthquakes is the level of the stress drop over asperities which release and partition the strain energy. We quantify the energetic balance of earthquakes in terms of strain energy Est and its components (fracture (Eg), friction (Ef) and seismic (Es) energy) using an extended Hamilton's principle. The earthquakes are thrust-interplate, strike slip, shallow in-slab, slow/tsunami, deep and continental. The (scaled) strain energy equation we derived is: Est/M0 = (1+e(g,s))(Es/M_0), e(g,s) = Eg/E_s, assuming complete stress drop, using the (static) stress drop variability, and that Est and Es are not in a 1-to-1 correspondence. With all uncertainties, our analysis reveal, for a given seismic moment, a large variation of earthquakes in terms of energies, even in the same seismic region. In view of these, for further understanding of earthquakes behaviour we introduce energy classes, and present first results.

  4. OMG Earthquake! Can Twitter improve earthquake response?

    NASA Astrophysics Data System (ADS)

    Earle, P. S.; Guy, M.; Ostrum, C.; Horvath, S.; Buckmaster, R. A.

    2009-12-01

    The U.S. Geological Survey (USGS) is investigating how the social networking site Twitter, a popular service for sending and receiving short, public, text messages, can augment its earthquake response products and the delivery of hazard information. The goal is to gather near real-time, earthquake-related messages (tweets) and provide geo-located earthquake detections and rough maps of the corresponding felt areas. Twitter and other social Internet technologies are providing the general public with anecdotal earthquake hazard information before scientific information has been published from authoritative sources. People local to an event often publish information within seconds via these technologies. In contrast, depending on the location of the earthquake, scientific alerts take between 2 to 20 minutes. Examining the tweets following the March 30, 2009, M4.3 Morgan Hill earthquake shows it is possible (in some cases) to rapidly detect and map the felt area of an earthquake using Twitter responses. Within a minute of the earthquake, the frequency of “earthquake” tweets rose above the background level of less than 1 per hour to about 150 per minute. Using the tweets submitted in the first minute, a rough map of the felt area can be obtained by plotting the tweet locations. Mapping the tweets from the first six minutes shows observations extending from Monterey to Sacramento, similar to the perceived shaking region mapped by the USGS “Did You Feel It” system. The tweets submitted after the earthquake also provided (very) short first-impression narratives from people who experienced the shaking. Accurately assessing the potential and robustness of a Twitter-based system is difficult because only tweets spanning the previous seven days can be searched, making a historical study impossible. We have, however, been archiving tweets for several months, and it is clear that significant limitations do exist. The main drawback is the lack of quantitative information such as epicenter, magnitude, and strong-motion recordings. Without quantitative data, prioritization of response measures, including building and infrastructure inspection, are not possible. The main advantage of Twitter is speed, especially in sparsely instrumented areas. A Twitter based system potentially could provide a quick notification that there was a possible event and that seismographically derived information will follow. If you are interested in learning more, follow @USGSted on Twitter.

  5. The 2013 Mw6.7 Lushan earthquake triggered by viscoelastic stress transfer of the 2008 Mw7.9 Wenchuan earthquake

    NASA Astrophysics Data System (ADS)

    Xiao, J.; Wang, W.; He, J.

    2013-12-01

    On April 20, 2013, the Mw6.7 Lushan earthquake collapsed hundreds of buildings and killed more than 190 people in Sichuan, China. This earthquake occurred about 80 km south from the epicenter of, and about 5 years after, the devastating 2008 Mw7.9 Wenchuan earthquake. Previous studies indicated that around area near the Lushan earthquake, the coseismic change of Coulomb failure stress induced by the Wenchuan earthquake is enhanced. However, the Coulomb failure stress change resolved on the Lushan rupture is unclear; more importantly, the elastic change of Coulomb failure stress alone seems hard to explain delayed occurrence of the Lushan earthquake. Here, we build a three-dimensional viscoelastic finite element model to explore possible triggering behavior between the two events. Constrained with rupture parameters of the two earthquakes and reasonable bounds of crustal rheology between the Tibetan plateau and the Sichuan basin, we find that within ~5 years after the Wenchuan earthquake, the Coulomb failure stress change resolved on epicenter of the Lushan earthquake increased from ~0.09-0.23 bar to ~0.23-0.50 bar with apparent coefficient of friction from 0.6 to 0.4, attesting that the Lushan earthquake is a delayed-triggering event by viscoelastic stress transfer of the Wenchuan earthquake. This means that the great Wenchuan earthquake has been still strengthening the failure stress on some active faults, highlighting that its triggering potential for strong earthquakes should be paid a great attention in a relatively long period.

  6. Napa earthquake: An earthquake in a highly connected world

    NASA Astrophysics Data System (ADS)

    Bossu, R.; Steed, R.; Mazet-Roux, G.; Roussel, F.

    2014-12-01

    The Napa earthquake recently occurred close to Silicon Valley. This makes it a good candidate to study what social networks, wearable objects and website traffic analysis (flashsourcing) can tell us about the way eyewitnesses react to ground shaking. In the first part, we compare the ratio of people publishing tweets and with the ratio of people visiting EMSC (European Mediterranean Seismological Centre) real time information website in the first minutes following the earthquake occurrence to the results published by Jawbone, which show that the proportion of people waking up depends (naturally) on the epicentral distance. The key question to evaluate is whether the proportions of inhabitants tweeting or visiting the EMSC website are similar to the proportion of people waking up as shown by the Jawbone data. If so, this supports the premise that all methods provide a reliable image of the relative ratio of people waking up. The second part of the study focuses on the reaction time for both Twitter and EMSC website access. We show, similarly to what was demonstrated for the Mineral, Virginia, earthquake (Bossu et al., 2014), that hit times on the EMSC website follow the propagation of the P waves and that 2 minutes of website traffic is sufficient to determine the epicentral location of an earthquake on the other side of the Atlantic. We also compare with the publication time of messages on Twitter. Finally, we check whether the number of tweets and the number of visitors relative to the number of inhabitants is correlated to the local level of shaking. Together these results will tell us whether the reaction of eyewitnesses to ground shaking as observed through Twitter and the EMSC website analysis is tool specific (i.e. specific to Twitter or EMSC website) or whether they do reflect people's actual reactions.

  7. The 2011 Tohoku earthquake (Mw 9.0) sequence and subduction dynamics in Western Pacific and East Asia

    NASA Astrophysics Data System (ADS)

    Zhao, Dapeng

    2015-02-01

    We review recent findings on the causal mechanism of the great 2011 Tohoku earthquake (Mw 9.0) sequence and related issues on seismic structure and subduction dynamics in Western Pacific and East Asia. High-resolution tomography revealed significant lateral heterogeneities in the interplate megathrust zone beneath the Tohoku, South Kuril and Southwest Japan forearc regions. Large megathrust earthquakes since 1900 generally occurred in or around high-velocity (high-V) patches in the megathrust zone, which may reflect asperities resulting from subducted seamounts, oceanic ridges and other topographic highs on the Pacific seafloor. In contrast, low-velocity (low-V) patches in the megathrust zone may contain more sediments and fluids, where the subducting oceanic plate and the overlying continental plate are less coupled or even decoupled. The nucleation of large crustal earthquakes in the Japan Islands, including the 11 April 2011 Iwaki earthquake (M 7.0) in SE Tohoku, is affected by arc magma and fluids resulting from slab dehydration. The Philippine Sea plate has subducted aseismically down to 430-460 km depth under East China Sea, Tsushima Strait and Japan Sea. A window in the aseismic Philippine Sea slab is detected, which may be caused by splitting of weak parts of the slab at the subducted ridges (e.g., Kyushu-Paula ridge) and hot upwelling in the mantle wedge above the Pacific slab. The intraplate volcanism in Northeast Asia is caused by hot and wet upwelling flows in the big mantle wedge above the stagnant Pacific slab in the mantle transition zone. Frequent generation of large deep earthquakes (>500 km depth) in the Pacific slab may supply additional fluids preserved in the slab to the mantle wedge under the Changbai volcano, making Changbai the largest and most active intraplate volcano in Northeast Asia. Fluids may be involved in nucleation and rupture processes of all types of earthquakes.

  8. Modified-Fibonacci-Dual-Lucas method for earthquake prediction

    NASA Astrophysics Data System (ADS)

    Boucouvalas, A. C.; Gkasios, M.; Tselikas, N. T.; Drakatos, G.

    2015-06-01

    The FDL method makes use of Fibonacci, Dual and Lucas numbers and has shown considerable success in predicting earthquake events locally as well as globally. Predicting the location of the epicenter of an earthquake is one difficult challenge the other being the timing and magnitude. One technique for predicting the onset of earthquakes is the use of cycles, and the discovery of periodicity. Part of this category is the reported FDL method. The basis of the reported FDL method is the creation of FDL future dates based on the onset date of significant earthquakes. The assumption being that each occurred earthquake discontinuity can be thought of as a generating source of FDL time series The connection between past earthquakes and future earthquakes based on FDL numbers has also been reported with sample earthquakes since 1900. Using clustering methods it has been shown that significant earthquakes (<6.5R) can be predicted with very good accuracy window (+-1 day). In this contribution we present an improvement modification to the FDL method, the MFDL method, which performs better than the FDL. We use the FDL numbers to develop possible earthquakes dates but with the important difference that the starting seed date is a trigger planetary aspect prior to the earthquake. Typical planetary aspects are Moon conjunct Sun, Moon opposite Sun, Moon conjunct or opposite North or South Modes. In order to test improvement of the method we used all +8R earthquakes recorded since 1900, (86 earthquakes from USGS data). We have developed the FDL numbers for each of those seeds, and examined the earthquake hit rates (for a window of 3, i.e. +-1 day of target date) and for <6.5R. The successes are counted for each one of the 86 earthquake seeds and we compare the MFDL method with the FDL method. In every case we find improvement when the starting seed date is on the planetary trigger date prior to the earthquake. We observe no improvement only when a planetary trigger coincided with the earthquake date and in this case the FDL method coincides with the MFDL. Based on the MDFL method we present the prediction method capable of predicting global events or localized earthquakes and we will discuss the accuracy of the method in as far as the prediction and location parts of the method. We show example calendar style predictions for global events as well as for the Greek region using planetary alignment seeds.

  9. Earthquake casualty models within the USGS Prompt Assessment of Global Earthquakes for Response (PAGER) system

    USGS Publications Warehouse

    Jaiswal, Kishor; Wald, David J.; Earle, Paul; Porter, Keith A.; Hearne, Mike

    2011-01-01

    Since the launch of the USGSs Prompt Assessment of Global Earthquakes for Response (PAGER) system in fall of 2007, the time needed for the U.S. Geological Survey (USGS) to determine and comprehend the scope of any major earthquake disaster anywhere in the world has been dramatically reduced to less than 30 min. PAGER alerts consist of estimated shaking hazard from the ShakeMap system, estimates of population exposure at various shaking intensities, and a list of the most severely shaken cities in the epicentral area. These estimates help government, scientific, and relief agencies to guide their responses in the immediate aftermath of a significant earthquake. To account for wide variability and uncertainty associated with inventory, structural vulnerability and casualty data, PAGER employs three different global earthquake fatality/loss computation models. This article describes the development of the models and demonstrates the loss estimation capability for earthquakes that have occurred since 2007. The empirical model relies on country-specific earthquake loss data from past earthquakes and makes use of calibrated casualty rates for future prediction. The semi-empirical and analytical models are engineering-based and rely on complex datasets including building inventories, time-dependent population distributions within different occupancies, the vulnerability of regional building stocks, and casualty rates given structural collapse.

  10. Amending and complicating Chile’s seismic catalog with the Santiago earthquake of 7 August 1580

    NASA Astrophysics Data System (ADS)

    Cisternas, Marco; Torrejón, Fernando; Gorigoitia, Nicolás

    2012-02-01

    Historical earthquakes of Chile's metropolitan region include a previously uncatalogued earthquake that occurred on 7 August 1580 in the Julian calendar. We found an authoritative account of this earthquake in a letter written four days later in Santiago and now archived in Spain. The letter tells of a destructive earthquake that struck Santiago and its environs. In its reported effects it surpassed the one in the same city in 1575, until now presumed to be the only earthquake in the first century of central Chile's written history. It is not yet possible to identify the source of the 1580 earthquake but viable candidates include both the plate boundary and Andean faults at shallows depths around Santiago. By occurring just five years after another large earthquake, the 1580 earthquake casts doubt on the completeness of the region's historical earthquake catalog and the periodicity of its large earthquakes. That catalog, based on eyewitness accounts compiled mainly by Alexander Perrey and Fernand Montessus de Ballore, tells of large Chile's metropolitan region earthquakes in 1575, 1647, 1730, 1822, 1906 and 1985. The addition of a large earthquake in 1580 implies greater variability in recurrence intervals and may also mean greater variety in earthquake sources.

  11. The USGS Earthquake Scenario Project

    NASA Astrophysics Data System (ADS)

    Wald, D. J.; Petersen, M. D.; Wald, L. A.; Frankel, A. D.; Quitoriano, V. R.; Lin, K.; Luco, N.; Mathias, S.; Bausch, D.

    2009-12-01

    The U.S. Geological Surveys (USGS) Earthquake Hazards Program (EHP) is producing a comprehensive suite of earthquake scenarios for planning, mitigation, loss estimation, and scientific investigations. The Earthquake Scenario Project (ESP), though lacking clairvoyance, is a forward-looking project, estimating earthquake hazard and loss outcomes as they may occur one day. For each scenario event, fundamental input includes i) the magnitude and specified fault mechanism and dimensions, ii) regional Vs30 shear velocity values for site amplification, and iii) event metadata. A grid of standard ShakeMap ground motion parameters (PGA, PGV, and three spectral response periods) is then produced using the well-defined, regionally-specific approach developed by the USGS National Seismic Hazard Mapping Project (NHSMP), including recent advances in empirical ground motion predictions (e.g., the NGA relations). The framework also allows for numerical (3D) ground motion computations for specific, detailed scenario analyses. Unlike NSHMP ground motions, for ESP scenarios, local rock and soil site conditions and commensurate shaking amplifications are applied based on detailed Vs30 maps where available or based on topographic slope as a proxy. The scenario event set is comprised primarily by selection from the NSHMP events, though custom events are also allowed based on coordination of the ESP team with regional coordinators, seismic hazard experts, seismic network operators, and response coordinators. The event set will be harmonized with existing and future scenario earthquake events produced regionally or by other researchers. The event list includes approximate 200 earthquakes in CA, 100 in NV, dozens in each of NM, UT, WY, and a smaller number in other regions. Systematic output will include all standard ShakeMap products, including HAZUS input, GIS, KML, and XML files used for visualization, loss estimation, ShakeCast, PAGER, and for other systems. All products will be delivered via the EHP web pages in a user-searchable archive. In addition, we aim to duplicate most of the real-time earthquake event web page functionality for scenario drills and exercises, including all standard post-earthquake information tools. Hence, for each event, USGS PAGER runs will be produced, providing population exposure at current population levels, and Federal Emergency Management Agency (FEMA) will produce HAZUS impact assessments. Anticipated users include FEMA, the loss modeling and insurance communities, emergency responders and mitigation planners (city, county, state, industry, utilities, corporate), the general public and the media. The Earthquake Scenario Project will also take on several pending scientific challenges related to scenario generation, including ways to include fault directivity, numerical ground motions, and ways to produce ground motion uncertainties (in addition to median peak ground motions). A parallel though less comprehensive effort is underway to produce scenarios for targeted regions and events around the globe.

  12. Tsunami history of an Oregon coastal lake reveals a 4600 yr record of great earthquakes on the Cascadia subduction zone

    USGS Publications Warehouse

    Kelsey, H.M.; Nelson, A.R.; Hemphill-Haley, E.; Witter, R.C.

    2005-01-01

    Bradley Lake, on the southern Oregon coastal plain, records local tsunamis and seismic shaking on the Cascadia subduction zone over the last 7000 yr. Thirteen marine incursions delivered landward-thinning sheets of sand to the lake from nearshore, beach, and dune environments to the west. Following each incursion, a slug of marine water near the bottom of the freshwater lake instigated a few-year-to-several-decade period of a brackish (??? 4??? salinity) lake. Four additional disturbances without marine incursions destabilized sideslopes and bottom sediment, producing a suspension deposit that blanketed the lake bottom. Considering the magnitude and duration of the disturbances necessary to produce Bradley Lake's marine incursions, a local tsunami generated by a great earthquake on the Cascadia subduction zone is the only accountable mechanism. Extreme ocean levels must have been at least 5-8 m above sea level, and the cumulative duration of each marine incursion must have been at least 10 min. Disturbances without marine incursions require seismic shaking as well. Over the 4600 yr period when Bradley Lake was an optimum tsunami recorder, tsunamis from Cascadia plate-boundary earthquakes came in clusters. Between 4600 and 2800 cal yr B.P., tsunamis occurred at the average frequency of ??? 3-4 every 1000 yr. Then, starting ???2800 cal yr B.P., there was a 930-1260 yr interval with no tsunamis. That gap was followed by a ???1000 yr period with 4 tsunamis. In the last millennium, a 670-750 yr gap preceded the A.D. 1700 earthquake and tsunami. The A.D. 1700 earthquake may be the first of a new cluster of plate-boundary earthquakes and accompanying tsunamis. Local tsunamis entered Bradley Lake an average of every 390 yr, whereas the portion of the Cascadia plate boundary that underlies Bradley Lake ruptured in a great earthquake less frequently, about once every 500 yr. Therefore, the entire length of the subduction zone does not rupture in every earthquake, and Bradley Lake has recorded earthquakes caused by rupture along the entire length of the Cascadia plate boundary as well as earthquakes caused by rupture of shorter segments of the boundary. The tsunami record from Bradley Lake indicates that at times, most recently ???1700 yr B.P., overlapping or adjoining segments of the Cascadia plate boundary ruptured within decades of each other. ?? 2005 Geological Society of America.

  13. Relationship between marine mammal stranding events and offshore earthquakes

    NASA Astrophysics Data System (ADS)

    Grant, Rachel; Savirina, Anna; Hoppit, Will

    2014-05-01

    The causes of marine mammal stranding events are largely unknown, but may relate to ocean currents, severe weather, anthropogenic noise pollution, and other factors. Large stranding events have been suggested to occur as a result of offshore earthquakes but there is little evidence as yet to support this hypothesis. Stranding events occur in hotspots, which are sometimes areas of high seismic activity, such as Taiwan, and other times, in areas that are removed from seismic zones, such as Cape Cod. We analyse a large and robust dataset of marine mammal stranding data collected off the coast of Washington and Oregon from 1999 to 2010, to look for statistical connections to offshore earthquakes. We looked forward, as well as backward in time from significant seismic events, to ascertain whether stranding occurrences, if connected to earthquakes, are a result of the earthquake preparation period or the earthquake itself. Possible mechanisms are discussed.

  14. Detection of Temporally and Spatially Limited Periodic Earthquake Recurrence in Synthetic Seismic Records

    NASA Astrophysics Data System (ADS)

    Zielke, O.; Arrowsmith, R. J.

    2005-12-01

    The nonlinear dynamics of fault behavior are dominated by complex interactions among the multiple processes controlling the system. For example, temporal and spatial variations in pore pressure, healing effects, and stress transfer cause significant heterogeneities in fault properties and the stress-field at the sub-fault level. Numerical and laboratory fault models show that the interaction of large systems of fault elements causes the entire system to develop into a state of self-organized criticality. Once in this state, small perturbations of the system may result in chain reactions (i.e., earthquakes) which can affect any number of fault segments. This sensitivity to small perturbations is strong evidence for chaotic fault behavior, which implies that exact event prediction is not possible. However, earthquake prediction with a useful accuracy is nevertheless possible. Studies of other natural chaotic systems have shown that they may enter states of metastability, in which the system's behavior is predictable. Applying this concept to earthquake faults, these windows of metastable behavior should be characterized by periodic earthquake recurrence. The observed periodicity of the Parkfield, CA (M= 6) events may resemble such a window of metastability. I am statistically analyzing numerically generated seismic records to study these phases of periodic behavior. In this preliminary study, seismic records were generated using a model introduced by Nakanishi [Phys. Rev. A, 43, 6613-6621, 1991]. It consists of a one-dimensional chain of blocks (interconnected by springs) with a relaxation function that mimics velocity-weakened frictional behavior. The earthquakes occurring in this model show generally a power-law frequency-size distribution. However, for large events the distribution has a shoulder where the frequency of events is higher than expected from the power law. I have analyzed time-series of single block motions within the system. These time-series include noticeable periodicity during certain intervals in an otherwise aperiodic record. The observed periodic signal is not equally distributed over the range of offsets but shows a multi-modal distribution with increased periodicity for the smallest events and for large events that show a specific offset. These large events also form a shoulder in the frequency-size distribution. Apparently, the model exhibits characteristic earthquakes (defined by similar coseismic slip) that occur more frequently than expected from a power law distribution, and also are significantly more periodic. The wavelength of the periodic signal generally equals the minimum loading time, which is related to the loading velocity and the amount of coseismic slip (i.e., stress drop). No significant event occurs between the characteristic events as long as the system stays in a window of periodic behavior. Within the windows of periodic behavior, earthquake prediction is straightforward. Therefore, recognition of these windows not only in synthetic data but also in real seismic records, may improve the intra-window forecast of earthquakes. Further studies will attempt to determine the characteristics of onset, duration, and end of these windows of periodic earthquake recurrence. Only the motion of a single block within a bigger system was analyzed so far. Going from a zero dimensional scenario to a two dimensional case where the offsets not only of a single block but the displacement patterns caused by a certain event are analyzed will increase the verisimilitude of the detection of periodic earthquake recurrence within an otherwise chaotic seismic record.

  15. Earthquake Monitoring in Haiti

    USGS Multimedia Gallery

    Following the devastating 2010 Haiti earthquake, the USGS has been helping with earthquake awareness and monitoring in the country, with continued support from the U.S. Agency for International Development (USAID). This assistance has helped the Bureau des Mines et de l'Energie (BME) in Port-au-Prin...

  16. Stress interaction and the Canterbury earthquake sequence

    NASA Astrophysics Data System (ADS)

    Steacy, S.; Francois-Holden, C.

    2012-12-01

    The on-going Canterbury earthquake sequence, which includes the devastating Christchurch event of February 2011, has to date led to insured losses of greater than 16 billion US dollars. Each successive event increases the damage and the loss; the most recent M = 6 earthquake occurred on 23 December 2011. The location and severity of the earthquakes was a surprise due to the relatively low perceived seismic hazard in the region compared to other, more active parts of New Zealand. The first event (M=7.2) occurred in September 2010 approximately 40 km west of Christchurch. This was followed by 3 off-fault M>6 earthquakes in Feb., June, and Dec. 2011; the aftershock sequence was still continuing at the time of this writing. Here we investigate the stress relations between the large events and the entire aftershock population as well as the interaction between the large earthquakes themselves. For the former, we compute Coulomb stress changes on 3D optimally oriented planes assuming that the values of regional stresses ?2 and ?3 are nearly equal, consistent with observations of strike slip and reverse faulting in the region; our results show that >90% of aftershocks are consistent with triggering. We also compute stress changes directly on the fault planes of subsequent large events and compare these to slip in those events; not surprisingly the relation is fairly complex and depends to some extent on the choice of slip model.

  17. Intermediate- and long-term earthquake prediction.

    PubMed Central

    Sykes, L R

    1996-01-01

    Progress in long- and intermediate-term earthquake prediction is reviewed emphasizing results from California. Earthquake prediction as a scientific discipline is still in its infancy. Probabilistic estimates that segments of several faults in California will be the sites of large shocks in the next 30 years are now generally accepted and widely used. Several examples are presented of changes in rates of moderate-size earthquakes and seismic moment release on time scales of a few to 30 years that occurred prior to large shocks. A distinction is made between large earthquakes that rupture the entire downdip width of the outer brittle part of the earth's crust and small shocks that do not. Large events occur quasi-periodically in time along a fault segment and happen much more often than predicted from the rates of small shocks along that segment. I am moderately optimistic about improving predictions of large events for time scales of a few to 30 years although little work of that type is currently underway in the United States. Precursory effects, like the changes in stress they reflect, should be examined from a tensorial rather than a scalar perspective. A broad pattern of increased numbers of moderate-size shocks in southern California since 1986 resembles the pattern in the 25 years before the great 1906 earthquake. Since it may be a long-term precursor to a great event on the southern San Andreas fault, that area deserves detailed intensified study. Images Fig. 1 PMID:11607658

  18. Retrospective stress-forecasting of earthquakes

    NASA Astrophysics Data System (ADS)

    Gao, Yuan; Crampin, Stuart

    2015-04-01

    Observations of changes in azimuthally varying shear-wave splitting (SWS) above swarms of small earthquakes monitor stress-induced changes to the stress-aligned vertical microcracks pervading the upper crust, lower crust, and uppermost ~400km of the mantle. (The microcracks are intergranular films of hydrolysed melt in the mantle.) Earthquakes release stress, and an appropriate amount of stress for the relevant magnitude must accumulate before each event. Iceland is on an extension of the Mid-Atlantic Ridge, where two transform zones, uniquely run onshore. These onshore transform zones provide semi-continuous swarms of small earthquakes, which are the only place worldwide where SWS can be routinely monitored. Elsewhere SWS must be monitored above temporally-active occasional swarms of small earthquakes, or in infrequent SKS and other teleseismic reflections from the mantle. Observations of changes in SWS time-delays are attributed to stress-induced changes in crack aspect-ratios allowing stress-accumulation and stress-relaxation to be identified. Monitoring SWS in SW Iceland in 1988, stress-accumulation before an impending earthquake was recognised and emails were exchanged between the University of Edinburgh (EU) and the Iceland Meteorological Office (IMO). On 10th November 1988, EU emailed IMO that a M5 earthquake could occur soon on a seismically-active fault plane where seismicity was still continuing following a M5.1 earthquake six-months earlier. Three-days later, IMO emailed EU that a M5 earthquake had just occurred on the specified fault-plane. We suggest this is a successful earthquake stress-forecast, where we refer to the procedure as stress-forecasting earthquakes as opposed to predicting or forecasting to emphasise the different formalism. Lack of funds has prevented us monitoring SWS on Iceland seismograms, however, we have identified similar characteristic behaviour of SWS time-delays above swarms of small earthquakes which have enabled us to retrospectively stress-forecasting ~17 earthquakes ranging in magnitude from a M1.7 swarm event in N Iceland, to the 1999 M7.7 Chi-Chi Earthquake in Taiwan, and the 2004 Mw9.2 Sumatra-Andaman Earthquake (SAE). Before SAE, the changes in SWS were observed at seismic stations in Iceland at a distance of ~10,500km the width of the Eurasian Plate, from Indonesia demonstrating the 'butterfly wings' sensitivity of the New Geophysics of a critically microcracked Earth. At that time, the sensitivity of the phenomena had not been recognised, and the SAE was not stress-forecast. These results have been published at various times in various formats in various journals. This presentation displays all the results in a normalised format that allows the similarities to be recognised, confirming that observations of SWS time-delays can stress-forecast the times, magnitudes, and in some circumstances fault-breaks, of impending earthquakes. Papers referring to these developments can be found in geos.ed.ac.uk/home/scrampin/opinion. Also see abstracts in EGU2015 Sessions: Crampin & Gao (SM1.1), Liu & Crampin (NH2.5), and Crampin & Gao (GD.1).

  19. Earthquake sound perception

    NASA Astrophysics Data System (ADS)

    Tosi, Patrizia; Sbarra, Paola; De Rubeis, Valerio

    2012-12-01

    Sound is an effect produced by almost all earthquakes. Using a web-based questionnaire on earthquake effects that included questions relating to seismic sound, we collected 77,000 responses for recent shallow Italian earthquakes. An analysis of audibility attenuation indicated that the decrease of the percentage of respondents hearing the sound was proportional to the logarithm of the epicentral distance and linearly dependent on earthquake magnitude, in accordance with the behavior of ground displacement. Even if this result was based on Italian data, qualitative agreement with the results of theoretical displacement, and of a similar study based on French seismicity suggests wider validity. We also found that, given earthquake magnitude, audibility increased together with the observed macroseismic intensity, leading to the possibility of accounting for sound audibility in intensity assessment. Magnitude influenced this behavior, making small events easier to recognize, as suggested by their frequency content.

  20. On numerical earthquake prediction

    NASA Astrophysics Data System (ADS)

    Shi, Yaolin; Zhang, Bei; Zhang, Siqi; Zhang, Huai

    2014-06-01

    Can earthquakes be predicted? How should people overcome the difficulties encountered in the study of earthquake prediction? This issue can take inspiration from the experiences of weather forecast. Although weather forecasting took a period of about half a century to advance from empirical to numerical forecast, it has achieved significant success. A consensus has been reached among the Chinese seismological community that earthquake prediction must also develop from empirical forecasting to physical prediction. However, it is seldom mentioned that physical prediction is characterized by quantitatively numerical predictions based on physical laws. This article discusses five key components for numerical earthquake prediction and their current status. We conclude that numerical earthquake prediction should now be put on the planning agenda and its roadmap designed, seismic stations should be deployed and observations made according to the needs of numerical prediction, and theoretical research should be carried out.

  1. Demand surge following earthquakes

    USGS Publications Warehouse

    Olsen, Anna H.

    2012-01-01

    Demand surge is understood to be a socio-economic phenomenon where repair costs for the same damage are higher after large- versus small-scale natural disasters. It has reportedly increased monetary losses by 20 to 50%. In previous work, a model for the increased costs of reconstruction labor and materials was developed for hurricanes in the Southeast United States. The model showed that labor cost increases, rather than the material component, drove the total repair cost increases, and this finding could be extended to earthquakes. A study of past large-scale disasters suggested that there may be additional explanations for demand surge. Two such explanations specific to earthquakes are the exclusion of insurance coverage for earthquake damage and possible concurrent causation of damage from an earthquake followed by fire or tsunami. Additional research into these aspects might provide a better explanation for increased monetary losses after large- vs. small-scale earthquakes.

  2. A fluid-driven earthquake swarm on the margin of the Yellowstone caldera

    NASA Astrophysics Data System (ADS)

    Shelly, David R.; Hill, David P.; Massin, Frdrick; Farrell, Jamie; Smith, Robert B.; Taira, Taka'aki

    2013-09-01

    the past several decades, the Yellowstone caldera has experienced frequent earthquake swarms and repeated cycles of uplift and subsidence, reflecting dynamic volcanic and tectonic processes. Here we examine the detailed spatial-temporal evolution of the 2010 Madison Plateau swarm, which occurred near the northwest boundary of the Yellowstone caldera. To fully explore the evolution of the swarm, we integrated procedures for seismic waveform-based earthquake detection with precise double-difference relative relocation. Using cross correlation of continuous seismic data and waveform templates constructed from cataloged events, we detected and precisely located 8710 earthquakes during the 3 week swarm, nearly 4 times the number of events included in the standard catalog. This high-resolution analysis reveals distinct migration of earthquake activity over the course of the swarm. The swarm initiated abruptly on 17 January 2010 at about 10 km depth and expanded dramatically outward (both shallower and deeper) over time, primarily along a NNW striking, ~55 ENE dipping structure. To explain these characteristics, we hypothesize that the swarm was triggered by the rupture of a zone of confined high-pressure aqueous fluids into a preexisting crustal fault system, prompting release of accumulated stress. The high-pressure fluid injection may have been accommodated by hybrid shear and dilatational failure, as is commonly observed in exhumed hydrothermally affected fault zones. This process has likely occurred repeatedly in Yellowstone as aqueous fluids exsolved from magma migrate into the brittle crust, and it may be a key element in the observed cycles of caldera uplift and subsidence.

  3. A fluid-driven earthquake swarm on the margin of the Yellowstone caldera

    USGS Publications Warehouse

    Shelly, David R.; Hill, David P.; Massin, Frederick; Farrell, Jamie; Smith, Robert B.; Taira, Taka'aki

    2013-01-01

    Over the past several decades, the Yellowstone caldera has experienced frequent earthquake swarms and repeated cycles of uplift and subsidence, reflecting dynamic volcanic and tectonic processes. Here, we examine the detailed spatial-temporal evolution of the 2010 Madison Plateau swarm, which occurred near the northwest boundary of the Yellowstone caldera. To fully explore the evolution of the swarm, we integrated procedures for seismic waveform-based earthquake detection with precise double-difference relative relocation. Using cross-correlation of continuous seismic data and waveform templates constructed from cataloged events, we detected and precisely located 8710 earthquakes during the three-week swarm, nearly four times the number of events included in the standard catalog. This high-resolution analysis reveals distinct migration of earthquake activity over the course of the swarm. The swarm initiated abruptly on January 17, 2010 at about 10 km depth and expanded dramatically outward (both shallower and deeper) over time, primarily along a NNW-striking, ~55º ENE-dipping structure. To explain these characteristics, we hypothesize that the swarm was triggered by the rupture of a zone of confined high-pressure aqueous fluids into a pre-existing crustal fault system, prompting release of accumulated stress. The high-pressure fluid injection may have been accommodated by hybrid shear and dilatational failure, as is commonly observed in exhumed hydrothermally affected fault zones. This process has likely occurred repeatedly in Yellowstone as aqueous fluids exsolved from magma migrate into the brittle crust, and it may be a key element in the observed cycles of caldera uplift and subsidence.

  4. The Maupin, Oregon Earthquake Swarm

    NASA Astrophysics Data System (ADS)

    Braunmiller, J.; Williams, M.; Trehu, A. M.; Nabelek, J.

    2008-12-01

    The area near Maupin, Oregon has experienced over 300 earthquakes since December 2006. The events, located by the Pacific Northwest Seismic Network (PNSN), occurred ~10 km SE of the town in central Oregon and ~50 km E-SE of Mount Hood. The temporal event pattern and lack of a distinct main shock are characteristic of an earthquake swarm with the event-size distribution indicating a low b-value similar to other non-volcanic swarms. Locations show a NW-SE trending, ~4x3 km cluster at apparent depths of 12-24 km. The largest events (Mw=3.8 and 3.9) on March 1, 2007 and July 14, 2008 occurred more than one year apart; 11 other events had a magnitude of 3 or greater. The larger events were felt locally. During the first 14 months EarthScope USArray seismic stations surrounded the swarm, providing a unique high-quality dataset. Waveform similarity at the closest USArray site G06A indicates hypocenters are much tighter than suggested by the PNSN distribution. Moment tensor inversion reveals nearly identical double- couple strike-slip mechanisms on a plane striking ~15 NW for the three largest 2007 events and the July 2008 event. The April 2008 Mw=3.3 event is rotated ~10 clockwise consistent with slight changes of G06A three-component waveforms relative to the other events. Preferred centroid depths are in the 15-20 km range. Historically, seismicity in the Pacific Northwest east of the Cascades is characterized by sporadic bursts of clustered seismicity with occasional M=6 earthquakes. The largest instrumentally recorded earthquake near Maupin (Mw=4.6) occurred 1976. An earlier swarm was observed 1987, but since then only ~2 events/yr occurred until the current swarm. In spite of recurrent seismicity, exposed surface rocks near Maupin are undeformed lava flows of the Columbia River Basalt Group and older John Day volcanics. The geologic map of Oregon shows a NW-trending dip slip fault near the epicenter area, inconsistent with moment tensor solutions. The cause for the swarm is currently unknown with hypotheses ranging from magmatic or fluid motion in the crust to tectonic activity along a weakly coupled microplate boundary.

  5. Protecting Your Family From Earthquakes-The Seven Steps to Earthquake Safety (in Spanish and English)

    USGS Publications Warehouse

    Developed by American Red Cross, Asian Pacific Fund, California Earthquake Authority, Governor's Office of Emergency Services, New America Media, U.S. Department of Homeland Security Federal Emergency Management Agency, and U.S. Geological Survey

    2007-01-01

    This book is provided here to share an important message on emergency preparedness. Historically, we have suffered earthquakes here in the San Francisco Bay Area that have caused severe hardship for residents and incredible damage to our cities. It is likely we will experience a severe earthquake within the next 30 years. Many of us come from other countries where we have experienced earth- quakes, so we believe that we understand them. However, the way we prepare for earthquakes in our home country may be different from the way it is necessary to prepare for earthquakes here. Very f w people die from collapsing buildings in the Bay Area because most structures are built to stand up to the shaking. But it is quite possible that your family will be without medical care or grocery stores and separated from one another for several days to weeks. It will ultimately be up to you to keep your family safe until help arrives, so we are asking you to join us in learning to take care of your family before, during, and after an earthquake. The first step is to read this book. Everyone in your family, children and adults, can learn how to prepare for an earthquake. Then take advantage of the American Red Cross Earthquake Preparedness training courses offered in your community. These preparedness courses are free, and also offered in Spanish and available to everyone in the community regardless of family history, leg al status, gender, or age. We encourage you to take one of these free training workshops. Look on the back cover for more information. Remember that an earthquake can occur without warning, and the only way that we can reduce the harm caused by earthquakes is to be prepared. Get Prepared!

  6. Earthquake fault superhighways

    NASA Astrophysics Data System (ADS)

    Robinson, D. P.; Das, S.; Searle, M. P.

    2010-10-01

    Motivated by the observation that the rare earthquakes which propagated for significant distances at supershear speeds occurred on very long straight segments of faults, we examine every known major active strike-slip fault system on land worldwide and identify those with long (> 100 km) straight portions capable not only of sustained supershear rupture speeds but having the potential to reach compressional wave speeds over significant distances, and call them "fault superhighways". The criteria used for identifying these are discussed. These superhighways include portions of the 1000 km long Red River fault in China and Vietnam passing through Hanoi, the 1050 km long San Andreas fault in California passing close to Los Angeles, Santa Barbara and San Francisco, the 1100 km long Chaman fault system in Pakistan north of Karachi, the 700 km long Sagaing fault connecting the first and second cities of Burma, Rangoon and Mandalay, the 1600 km Great Sumatra fault, and the 1000 km Dead Sea fault. Of the 11 faults so classified, nine are in Asia and two in North America, with seven located near areas of very dense populations. Based on the current population distribution within 50 km of each fault superhighway, we find that more than 60 million people today have increased seismic hazards due to them.

  7. Magnitude calibration of north Indian earthquakes

    NASA Astrophysics Data System (ADS)

    Ambraseys, N. N.; Douglas, J.

    2004-10-01

    This article is concerned primarily with the evaluation of the size and location of northern Indian and southern Tibetan earthquakes during the last 200 yr. It draws attention to the problems of assessing intensity of early and more recent earthquakes in a built environment, which is different from that for which the intensity scale has been constructed and to the way in which isoseismals are drawn. Through a re-evaluation of intensities and a reassessment of isoseismals, a formula for the estimation of surface wave magnitude using isoseismal radii is derived. This formula is used to estimate the surface wave magnitudes of 16 earthquakes that occurred in the region between 1803 and 1900. This study shows that it is possible to calculate accurate surface wave magnitudes for earthquakes that occurred before the advent of the scale and that there is no need to resort to empirical formulae for the assessment of the size and seismic moment release of pre-20th-century earthquakes. Also derived are formulae for the conversion of Ms to M0. In total, locations, surface wave magnitudes and M0 estimates are presented for 43 important events that occurred in the region between 1803 and 1974, eight of which were in the lower crust or were subcrustal. We find that the M0-Ms scaling for India yields smaller Ms than the global relation and that the methodology used can help to evaluate more realistic slip rates as well as to address other issues related to earthquake hazard in northern India.

  8. Waveform Cross-Correlation for Improved North Texas Earthquake Locations

    NASA Astrophysics Data System (ADS)

    Phillips, M.; DeShon, H. R.; Oldham, H. R.; Hayward, C.

    2014-12-01

    In November 2013, a sequence of earthquakes began in Reno and Azle, TX, two communities located northwest of Fort Worth in an area of active oil and gas extraction. Only one felt earthquake had been reported within the area before the occurrence of probable injection-induced earthquakes at the Dallas-Fort Worth airport in 2008. The USGS National Earthquakes Information Center (NEIC) has reported 27 felt earthquakes in the Reno-Azle area through January 28, 2014. A temporary seismic network was installed beginning in December 2013 to acquire data to improve location and magnitude estimates and characterize the earthquake sequence. Here, we present high-resolution relative earthquake locations derived using differential time data from waveform cross-correlation. Cross-correlation is computed using the GISMO software suite and event relocation is done using double difference relocation techniques. Waveform cross-correlation of the local data indicates high (>70%) similarity between 4 major swarms of events lasting between 18 and 24 hours. These swarms are temporal zones of high event frequency; 1.4% of the time series data accounts for 42.1% of the identified local earthquakes. Local earthquakes are occurring along the Newark East Fault System, a NE-SW striking normal fault system previously thought inactive at depths between 2 and 8 km in the Ellenburger limestone formation and underlying Precambrian basement. Data analysis is ongoing and continued characterization of the associated fault will provide improved location estimates.

  9. Real-time forecasts of tomorrow's earthquakes in California.

    PubMed

    Gerstenberger, Matthew C; Wiemer, Stefan; Jones, Lucile M; Reasenberg, Paul A

    2005-05-19

    Despite a lack of reliable deterministic earthquake precursors, seismologists have significant predictive information about earthquake activity from an increasingly accurate understanding of the clustering properties of earthquakes. In the past 15 years, time-dependent earthquake probabilities based on a generic short-term clustering model have been made publicly available in near-real time during major earthquake sequences. These forecasts describe the probability and number of events that are, on average, likely to occur following a mainshock of a given magnitude, but are not tailored to the particular sequence at hand and contain no information about the likely locations of the aftershocks. Our model builds upon the basic principles of this generic forecast model in two ways: it recasts the forecast in terms of the probability of strong ground shaking, and it combines an existing time-independent earthquake occurrence model based on fault data and historical earthquakes with increasingly complex models describing the local time-dependent earthquake clustering. The result is a time-dependent map showing the probability of strong shaking anywhere in California within the next 24 hours. The seismic hazard modelling approach we describe provides a better understanding of time-dependent earthquake hazard, and increases its usefulness for the public, emergency planners and the media. PMID:15902254

  10. Earthquakes and fault creep on the northern San Andreas fault

    USGS Publications Warehouse

    Nason, R.

    1979-01-01

    At present there is an absence of both fault creep and small earthquakes on the northern San Andreas fault, which had a magnitude 8 earthquake with 5 m of slip in 1906. The fault has apparently been dormant after the 1906 earthquake. One possibility is that the fault is 'locked' in some way and only produces great earthquakes. An alternative possibility, presented here, is that the lack of current activity on the northern San Andreas fault is because of a lack of sufficient elastic strain after the 1906 earthquake. This is indicated by geodetic measurements at Fort Ross in 1874, 1906 (post-earthquake), and 1969, which show that the strain accumulation in 1969 (69 ?? 10-6 engineering strain) was only about one-third of the strain release (rebound) in the 1906 earthquake (200 ?? 10-6 engineering strain). The large difference in seismicity before and after 1906, with many strong local earthquakes from 1836 to 1906, but only a few strong earthquakes from 1906 to 1976, also indicates a difference of elastic strain. The geologic characteristics (serpentine, fault straightness) of most of the northern San Andreas fault are very similar to the characteristics of the fault south of Hollister, where fault creep is occurring. Thus, the current absence of fault creep on the northern fault segment is probably due to a lack of sufficient elastic strain at the present time. ?? 1979.

  11. Thermal Runaway during Intermediate-Depth Earthquake Rupture

    NASA Astrophysics Data System (ADS)

    Prieto, German; Florez, Manuel; Barrett, Sarah; Beroza, Gregory; Pedraza, Patricia; Blanco, Jose; Poveda, Esteban

    2014-05-01

    Intermediate-depth earthquakes occur at depths of 50 to 300 km in subducting lithosphere. Despite their ubiquity in earthquake catalogs, their physical mechanism remains unclear because ambient temperatures and pressures are expected to lead to ductile, rather than brittle deformation. There are two leading explanations for the physical mechanism that enables these earthquakes. In the first, high pore pressure from metamorphic dehydration reactions in the subducting slab reduces the effective normal stress sufficiently to enable frictional failure. In the second, slow deformation generates heat, which leads to weakening, further deformation, and a self-localizing thermal shear runaway. We use the nest of intermediate-depth earthquakes under Bucaramanga, Colombia as recorded by the digital RSNC (Red Ssmica Nacional de Colombia) regional seismic network to explore these two possibilities. We observe a combination of high stress drop and low radiation efficiency for Mw 4-5 earthquakes in the Bucaramanga Nest that points to the importance of thermal effects. If we assume a cm-scale fault-zone width, this combination implies a temperature increase of 600-1,000C during earthquake failure, which suggests that substantial shear heating, and possibly partial melting, occurs during intermediate-depth earthquake failure. Our observations support thermal shear runaway as the mechanism for intermediate-depth earthquakes. This mechanism could help explain differences in their behavior, such as the paucity of aftershocks, compared to shallow earthquakes. Although we have inferred these mechanisms for intermediate depth earthquakes, it's likely that they would apply for rapid deformation on the deep extensions of fault zones as well - particularly during large earthquakes, such as the 2012 Mw 8.6 strike-slip event off Sumatra, which is inferred to have ruptured well into the oceanic mantle.

  12. Andean earthquakes felt at long distances in Brazil! What will we do?

    NASA Astrophysics Data System (ADS)

    Franca, G. S.; Assumpcao, M.; Santiago, P. S.

    2007-12-01

    In the past several decades, more than 45 Andean earthquakes have been felt in Brazilian cities, thousands of kilometers away from the epicenter, especially by oscillations of high-rise buildings. Because of the increase of skyscrapers in big cities, such long-distance effects are becoming more frequent. In Sao Paulo, for example, such macroseismic effects have been observed every 3-5 years on average. We present a study on the characteristics of the earthquakes and cities more susceptible to cause high-rise buildings to oscillate. Most earthquakes occur at intermediate or large depths and those with magnitudes larger or equal than 5.0 mb, such as in the Jujuy and Santiago del Estero regions of northern Argentina, have caused long distance macroseismic effects. Most affected cities lie in sedimentary basins, such as Sao Paulo and Manaus, which can amplify the ground motions through basin resonance. In some cases, buildings with the longest axis oriented perpendicular to the largest S amplitudes (SH component) seem to be more susceptible to oscillations. As response levels are small, we used a on broad-band stations on each floor of a residential building (9-storey) in Brasilia City, in order to identify the characteristics of the building for preliminary analysis. This result is being compared with analysis of the ground motion amplitudes, recorded by nearby broadband stations.

  13. Mental health training experiences among Haitian healthcare workers post-earthquake 2010

    PubMed Central

    Cianelli, R.; Wilkinson, C.; Mitchell, E.; Anglade, D.; Nicolas, G.; Mitrani, V.; Peragallo, N.

    2014-01-01

    Background After the 2010 earthquake in Haiti, the large number of persons with major limb damage, amputations, shock, trauma, anxiety and depression placed a severe strain on mental health (MH) services. Purpose This qualitative study describes the impact and acceptability of a Mental Health Training Program (MHTP) implemented in the north of Haiti after the earthquake. Methods A total of 113 healthcare workers (HCWs) participated in a training program designed to build local MH care capacity. The training curriculum draws on literature related to MH and the impact of the Haiti earthquake. Two focus groups were conducted with 16 HCWs; discussions centred on the personal and professional impact and acceptability of the training program. Discussion Results demonstrated that the MHTP changed the HCWs perceptions about MH issues and provided them with the knowledge and skills to respond to growing community MH needs. Acceptability of the MHTP was related to the content covered, to the delivery mode of the content and to the cultural appropriateness of the program. Conclusions Disasters of different types will continue to occur and to impact MH in communities around the world. MH training will allow nurses to quickly and effectively respond to disasters. A coordinated emergency plan that is subject to frequent review, rehearsal and evaluation is also essential. PMID:24251943

  14. A tectonic earthquake sequence preceding the April-May 1999 eruption of Shishaldin Volcano, Alaska

    USGS Publications Warehouse

    Moran, S.C.; Stihler, S.D.; Power, J.A.

    2002-01-01

    On 4 March 1999, a shallow ML 5.2 earthquake occurred beneath Unimak Island in the Aleutian Arc. This earthquake was located 10-15 km west of Shishaldin Volcano, a large, frequently active basaltic-andesite stratovolcano. A Strombolian eruption began at Shishaldin roughly 1 month after the mainshock, culminating in a large explosive eruption on 19 April. We address the question of whether or not the eruption caused the mainshock by computing the Coulomb stress change caused by an inflating dike on fault planes oriented parallel to the mainshock focal mechanism. We found Coulomb stress increases of ???0.1 MPa in the region of the mainshock, suggesting that magma intrusion prior to the eruption could have caused the mainshock. Satellite and seismic data indicate that magma was moving upwards beneath Shishaldin well before the mainshock. indicating that, in an overall sense, the mainshock cannot be said to have caused the eruption. However, observations of changes at the volcano following the mainshock and several large aftershocks suggest that the earthquakes may, in turn, have influenced the course of the eruption.

  15. Earthquake Variations Along the Middle America Trench, Central America

    NASA Astrophysics Data System (ADS)

    Bilek, S. L.; Stankova-Pursley, J.

    2008-12-01

    Subduction zones, home to the majority of the world's earthquakes, have also been the hosts for some of the world's most devastating tsunami. Seismic characteristics of subduction zone earthquakes, including the time constant of rupture, range from typical fast (few-10s seconds) ruptures to slow, long duration (100s of seconds) tsunami events, to silent (days-years) earthquakes that are observed geodetically rather than seismically. Causes for variations in the seismic parameters are currently not well understood, yet the causative factors influencing rupture could be very important in seismic and tsunami hazard assessment. Several aspects of subduction zone conditions may be important for influencing earthquake rupture, with our focus here on the effects of subducting plate inputs on earthquake rupture characteristics. Our main focus area for this study is along the Central American subduction zone because of the well-characterized input into the zone as well as detailed seismic catalogs. This region has also experienced slow, silent, and tsunami earthquakes in the past. We suggest that complexity on the subducting Cocos plate dictates variations in rupture characteristics for earthquakes over a range of magnitudes. Preliminary results for earthquakes larger than Mw=5.7 suggest earthquakes with slow rupture durations from southern Mexico through Costa Rica, with the slowest events occurring in the region between the high slip zones of the 1992 Nicaragua tsunami earthquake, away from imaged seamounts in the high slip regions. Slow earthquakes are also observed in southern Mexico. In addition, analysis of rupture characteristics of small magnitude (Mw<4) along the Costa Rica margin also suggests variations in stress drop that correspond with variations in geodetically estimated plate locking and rupture zones of past large earthquakes.

  16. The Lushan earthquake and the giant panda: impacts and conservation.

    PubMed

    Zhang, Zejun; Yuan, Shibin; Qi, Dunwu; Zhang, Mingchun

    2014-06-01

    Earthquakes not only result in a great loss of human life and property, but also have profound effects on the Earth's biodiversity. The Lushan earthquake occurred on 20 Apr 2013, with a magnitude of 7.0 and an intensity of 9.0 degrees. A distance of 17.0 km from its epicenter to the nearest distribution site of giant pandas recorded in the Third National Survey was determined. Making use of research on the Wenchuan earthquake (with a magnitude of 8.0), which occurred approximately 5 years ago, we briefly analyze the impacts of the Lushan earthquake on giant pandas and their habitat. An earthquake may interrupt ongoing behaviors of giant pandas and may also cause injury or death. In addition, an earthquake can damage conservation facilities for pandas, and result in further habitat fragmentation and degradation. However, from a historical point of view, the impacts of human activities on giant pandas and their habitat may, in fact, far outweigh those of natural disasters such as earthquakes. Measures taken to promote habitat restoration and conservation network reconstruction in earthquake-affected areas should be based on requirements of giant pandas, not those of humans. PMID:24952972

  17. Paleoseismoloigcal evidence of the 1762 and earlier earthquakes off Myanmar

    NASA Astrophysics Data System (ADS)

    Aung, T.; Satake, K.; Okamura, Y.; Shishikura, M.; Swe, W.; Saw, H.; Swe, T.; Tun, S.; Aung, T.

    2007-12-01

    The potential for giant tsunamigenic earthquakes off the west coast of Myanmar, north of the 2004 Sumatra- Andaman earthquake has been debated. Tectonic environments (Cummins, 2007), recent GPS observations (Socquet, 2006) and historical descriptions of geomorphological changes and eyewitness accounts of the 1762 Bengal earthquake seem to support that the earthquake potential exists. As possible evidence of past earthquakes, marine terraces have developed along the Rakhine coast. Our field surveys at the four localities on west and middle Phayonkar islands identified at least three clear steps of marine terraces approximately 1-2 m, ~5 m and ~10 m above present sea level. These steps indicate that sudden sea level change, or coseismic uplift associated with the large earthquakes, occurred in the past. Radiocarbon dating of coral or shell fossils provide ages of the uplift events. Six samples from the lower terrace indicate the most recent uplift occurred between 1585 and 1860 AD. This range includes the 1762 Bengal earthquake. Dates of the middle step, based on four samples, range between 805 and 1220 AD. Four samples on the upper step indicate an uplift event between 1295 and 600 BC. The time interval between the lower and middle step is several hundred years, while that between the middle and upper step is more than 1000 years. The longer time span and the larger elevation difference of the earlier interval may indicate either missing event(s) or variability of earthquake size and recurrence interval.

  18. Interseismic Lithospheric Response of the Southern End of the Cascadia Subduction Zone Following the 1992 Cape Mendocino Earthquake

    NASA Astrophysics Data System (ADS)

    Vermeer, J.; Hemphill-Haley, M. A.

    2014-12-01

    The Cascadia subduction zone (CSZ) in the Pacific Northwest where the pacific plate is subducting beneath the North American plate may be capable of producing M 9 earthquakes. At its southern end, the CSZ terminates at the Mendocino triple junction in northern California, a region of frequent seismic activity. The 1992 M 7.1 Cape Mendocino earthquake caused up to 1.4 m of measured coseismic deformation and it is thought to have been rupture of the southern end of the CSZ. I will present static GPS monument relocation data and the positions of intertidal organisms to measure the interseismic crustal deformation in the 22 years since the 1992 event. This evidence for post- and interseismic lithospheric response may show whether the earthquake was due to rupture of the southern end of the CSZ or a subsidiary fault. Because the megathrust has higher strain rates than subsidiary faults, we expect that significant interseismic deformation should have occurred if the 1992 earthquake was on the subduction zone interface. It will also provide an estimate of whether post-seismic recovery has been occurring since that event. Although the coseismic deformation was well documented via leveling and Vertical Extent of Mortality (VEM) of sessile intertidal organisms, no post seismic work had been done to measure the interseismic deformation. This study utilizes high resolution GPS observation of established benchmarks compared with the leveling from 1992 to measure the vertical change. It also compares elevation of specific intertidal organism colonies to the elevation of living organisms following the 1992 uplift as a proxy for relative sea level change. Quantifying the interseismic deformation allows us to better understand the source of the earthquake and how the upper plate is responding to strain accumulation along the subduction zone. Significant interseismic deformation would indicate that the fault may be reloading quickly and the earthquake was likely associated with rupture of the megathrust, which has much higher strain rates than subsidiary faults. This, in turn, may suggest segmentation of the southern CSZ. Little interseismic deformation might indicate the 1992 earthquake occurred on a subsidiary fault and not the megathrust itself. Preliminary results indicate that there has been little interseismic deformation.

  19. Earthquake fluctuations in wells in New Jersey

    USGS Publications Warehouse

    Austin, Charles R.

    1960-01-01

    New Jersey is fortunate to be situated in a region that is relatively stable, geologically. For this reason scientists believe, on the basis of the best scientific evidence available, that the chances of New Jersey experiencing a major earthquake are very small. The last major earthquake on the east coast occurred at Charleston, S. C., in 1886. Minor shocks have been felt in New Jersey, however, from time to time. Reports of dishes being rattled or even of plaster in buildings being cracked are not uncommon. These minor disturbances are generally restricted to relatively small areas.

  20. Earthquakes induced by deep penetrating bombing?

    NASA Astrophysics Data System (ADS)

    Balassanian, Serguei Y.

    2005-11-01

    The data of M?5 earthquakes occurred in one year before and after 4 deep penetrating bombs in the region within 500 km and 1 000 km from the shooting site are presented. The 4 bombs are those happened in 1999 Kosovo of Yugoslavia, the 1991 Baghdad of Iraq, the 2001 Tora Bora of Afghanistan, and the 2003 Kirkuk of Iraq, respectively. The data indicate that the deep penetrating bombs may have remotely triggered some earthquakes. The deep penetrating bombs in seismically active regions should be forbidden.

  1. The Challenge of Centennial Earthquakes to Improve Modern Earthquake Engineering

    NASA Astrophysics Data System (ADS)

    Saragoni, G. Rodolfo

    2008-07-01

    The recent commemoration of the centennial of the San Francisco and Valparaiso 1906 earthquakes has given the opportunity to reanalyze their damages from modern earthquake engineering perspective. These two earthquakes plus Messina Reggio Calabria 1908 had a strong impact in the birth and developing of earthquake engineering. The study of the seismic performance of some up today existing buildings, that survive centennial earthquakes, represent a challenge to better understand the limitations of our in use earthquake design methods. Only Valparaiso 1906 earthquake, of the three considered centennial earthquakes, has been repeated again as the Central Chile, 1985, Ms = 7.8 earthquake. In this paper a comparative study of the damage produced by 1906 and 1985 Valparaiso earthquakes is done in the neighborhood of Valparaiso harbor. In this study the only three centennial buildings of 3 stories that survived both earthquakes almost undamaged were identified. Since for 1985 earthquake accelerogram at El Almendral soil conditions as well as in rock were recoded, the vulnerability analysis of these building is done considering instrumental measurements of the demand. The study concludes that good performance of these buildings in the epicentral zone of large earthquakes can not be well explained by modern earthquake engineering methods. Therefore, it is recommended to use in the future of more suitable instrumental parameters, such as the destructiveness potential factor, to describe earthquake demand.

  2. The Challenge of Centennial Earthquakes to Improve Modern Earthquake Engineering

    SciTech Connect

    Saragoni, G. Rodolfo

    2008-07-08

    The recent commemoration of the centennial of the San Francisco and Valparaiso 1906 earthquakes has given the opportunity to reanalyze their damages from modern earthquake engineering perspective. These two earthquakes plus Messina Reggio Calabria 1908 had a strong impact in the birth and developing of earthquake engineering. The study of the seismic performance of some up today existing buildings, that survive centennial earthquakes, represent a challenge to better understand the limitations of our in use earthquake design methods. Only Valparaiso 1906 earthquake, of the three considered centennial earthquakes, has been repeated again as the Central Chile, 1985, Ms = 7.8 earthquake. In this paper a comparative study of the damage produced by 1906 and 1985 Valparaiso earthquakes is done in the neighborhood of Valparaiso harbor. In this study the only three centennial buildings of 3 stories that survived both earthquakes almost undamaged were identified. Since for 1985 earthquake accelerogram at El Almendral soil conditions as well as in rock were recoded, the vulnerability analysis of these building is done considering instrumental measurements of the demand. The study concludes that good performance of these buildings in the epicentral zone of large earthquakes can not be well explained by modern earthquake engineering methods. Therefore, it is recommended to use in the future of more suitable instrumental parameters, such as the destructiveness potential factor, to describe earthquake demand.

  3. The 2014 M 6.0 South Napa Earthquake in the Context of the Earthquake Cycle in the San Francisco Bay Area

    NASA Astrophysics Data System (ADS)

    Jaume, S. C.

    2014-12-01

    The 2014 M 6.0 South Napa earthquake is the second M ? 5.5 earthquake to occur in the San Francisco Bay region since the 1989 M 7.0 Loma Prieta earthquake. This poster will examine how this earthquake fits into the earthquake history of the Bay region, which has shown considerable variation in the rate of moderate (M 5.5-6.5) earthquakes. A number of models have been developed to explain these changes in moderate earthquake rates, including the Accelerating Moment Release model (e.g., Sykes and Jaum, Nature, 1990; Bufe and Varnes, J. Geophys. Res., 1993) and the Stress Shadow model (e.g., Harris and Simpson, J. Geophys. Res., 1998). In addition, various groups have made projections of future earthquake activity in the San Francisco Bay region, including the Working Group on California Earthquake Probabilities (Field et al., USGS OFR, 2008) and Bebbington et al. (PAGEOPH, 2010), utilizing different physical models for earthquake occurrence. In my poster I will compare and contrast these different views of seismicity in the Bay region and where the 2014 South Napa earthquake fits into them. In particular, I will explore what these different models imply for future moderate earthquake occurrence and hazards thereof.

  4. Rapid estimation of earthquake loss based on instrumental seismic intensity: design and realization

    NASA Astrophysics Data System (ADS)

    Huang, Hongsheng; Chen, Lin; Zhu, Gengqing; Wang, Lin; Lin, Yanzhao; Wang, Huishan

    2013-11-01

    As a result of our ability to acquire large volumes of real-time earthquake observation data, coupled with increased computer performance, near real-time seismic instrument intensity can be obtained by using ground motion data observed by instruments and by using the appropriate spatial interpolation methods. By combining vulnerability study results from earthquake disaster research with earthquake disaster assessment models, we can estimate the losses caused by devastating earthquakes, in an attempt to provide more reliable information for earthquake emergency response and decision support. This paper analyzes the latest progress on the methods of rapid earthquake loss estimation at home and abroad. A new method involving seismic instrument intensity rapid reporting to estimate earthquake loss is proposed and the relevant software is developed. Finally, a case study using the M L4.9 earthquake that occurred in Shun-chang county, Fujian Province on March 13, 2007 is given as an example of the proposed method.

  5. Cooperative earthquake research between the United States and the People's Republic of China

    SciTech Connect

    Russ, D.P.; Johnson, L.E.

    1986-01-01

    This paper describes cooperative research by scientists of the US and the People's Republic of China (PRC) which has resulted in important new findings concerning the fundamental characteristics of earthquakes and new insight into mitigating earthquake hazards. There have been over 35 projects cooperatively sponsored by the Earthquake Studies Protocol in the past 5 years. The projects are organized into seven annexes, including investigations in earthquake prediction, intraplate faults and earthquakes, earthquake engineering and hazards investigation, deep crustal structure, rock mechanics, seismology, and data exchange. Operational earthquake prediction experiments are currently being developed at two primary sites: western Yunnan Province near the town of Xiaguan, where there are several active faults, and the northeast China plain, where the devastating 1976 Tangshan earthquake occurred.

  6. Earthquake swarm activity with a low stress drop beneath Mt. Fuji, Japan: Indication of fluid-induced earthquakes?

    NASA Astrophysics Data System (ADS)

    Yamada, T.

    2012-12-01

    An earthquake swarm activity took place beneath Mount Fuji, Japan with a depth of 20 km in the end of January, 2012. Japan Meteorological Agency (JMA) determined hypocenters of 76 earthquakes with M > 2 in the area within two days on January 28 and 29. Five of them had magnitudes greater than 4 and the largest one was 5.4. The swarm activity showed a circular migration from the epicenter of an earthquake with M4.9 at 0739am on January 28 (JST, 2239pm UT on January 27) with a speed of 2 to 5 km/day. We analyzed stress drops of 17 earthquakes with M > 3.5 that occurred from January, 2000 to June, 2012 in the area of the swarm activity. We calculated empirical Green's functions from waveforms of earthquakes with magnitudes of 3.0 to 3.2 and estimated stress drops of the earthquakes assuming that the source spectra can be expressed as the omega-squared model. We found that earthquakes of the swarm had smaller stress drops by an order of magnitude than the values of earthquakes that occurred in the same area before the swarm. This result would suggest that the fluid increased the pore pressure and triggered the swarm activity, which is consistent with the epicenter migration. Epicenters of hte 76 earthquakes determined by the Japan Meteorological Agency. Color indicates the origin time of earthquakes. Time zero corresponds to 6am on January 28 (JST). Stress drops of 17 earthquakes with magnitudes greater than 3.5.

  7. The great Lisbon earthquake and tsunami of 1755: lessons from the recent Sumatra earthquakes and possible link to Plato's Atlantis

    NASA Astrophysics Data System (ADS)

    Gutscher, M.-A.

    2006-05-01

    Great earthquakes and tsunami can have a tremendous societal impact. The Lisbon earthquake and tsunami of 1755 caused tens of thousands of deaths in Portugal, Spain and NW Morocco. Felt as far as Hamburg and the Azores islands, its magnitude is estimated to be 8.5 9. However, because of the complex tectonics in Southern Iberia, the fault that produced the earthquake has not yet been clearly identified. Recently acquired data from the Gulf of Cadiz area (tomography, seismic profiles, high-resolution bathymetry, sampled active mud volcanoes) provide strong evidence for an active east dipping subduction zone beneath Gibraltar. Eleven out of 12 of the strongest earthquakes (M>8.5) of the past 100 years occurred along subduction zone megathrusts (including the December 2004 and March 2005 Sumatra earthquakes). Thus, it appears likely that the 1755 earthquake and tsunami were generated in a similar fashion, along the shallow east-dipping subduction fault plane. This implies that the Cadiz subduction zone is locked (like the Cascadia and Nankai/Japan subduction zones), with great earthquakes occurring over long return periods. Indeed, the regional paleoseismic record (contained in deep-water turbidites and shallow lagoon deposits) suggests great earthquakes off South West Iberia every 1500 2000 years. Tsunami deposits indicate an earlier great earthquake struck SW Iberia around 200 BC, as noted by Roman records from Cadiz. A written record of even older events may also exist. According to Plato's dialogues The Critias and The Timaeus, Atlantis was destroyed by strong earthquakes and floods in a single day and night at a date given as 11,600 BP. A 1 m thick turbidite deposit, containing coarse grained sediments from underwater avalanches, has been dated at 12,000 BP and may correspond to the destructive earthquake and tsunami described by Plato. The effects on a paleo-island (Spartel) in the straits of Gibraltar would have been devastating, if inhabited, and may have formed the basis for the Atlantis legend.

  8. Response of Sensitive Behaviors to Frequent Measurement

    PubMed Central

    2014-01-01

    We study the influence of frequent survey measurement on behavior. Widespread access to the Internet has made important breakthroughs in frequent measurement possible—potentially revolutionizing social science measurement of processes that change quickly over time. One key concern about using such frequent measurement is that it may influence the behavior being studied. We investigate this possibility using both a population-based experiment with random assignment to participation in a weekly journal for twelve months (versus no journal) and a large scale population-based journal-keeping study with weekly measurement for 30 months. Results reveal few of the measured behaviors are correlated with assignment to frequent measurement. Theoretical reasoning regarding the likely behavioral response to frequent measurement correctly predicts domains most vulnerable to this possibility. Overall, however, we found little evidence of behavioral response to frequent measurement. PMID:25432599

  9. Response of sensitive behaviors to frequent measurement.

    PubMed

    Axinn, William G; Jennings, Elyse A; Couper, Mick P

    2015-01-01

    We study the influence of frequent survey measurement on behavior. Widespread access to the Internet has made important breakthroughs in frequent measurement possible-potentially revolutionizing social science measurement of processes that change quickly over time. One key concern about using such frequent measurement is that it may influence the behavior being studied. We investigate this possibility using both a population-based experiment with random assignment to participation in a weekly journal for twelve months (versus no journal) and a large-scale, population-based, journal-keeping study with weekly measurement for 30 months. Results reveal few of the measured behaviors are correlated with assignment to frequent measurement. Theoretical reasoning regarding the likely behavioral response to frequent measurement correctly predicts domains most vulnerable to this possibility. Overall, however, we found little evidence of behavioral response to frequent measurement. PMID:25432599

  10. Earthquakes and emergence

    NASA Astrophysics Data System (ADS)

    Earthquakes and emerging infections may not have a direct cause and effect relationship like tax evasion and jail, but new evidence suggests that there may be a link between the two human health hazards. Various media accounts have cited a massive 1993 earthquake in Maharashtra as a potential catalyst of the recent outbreak of plague in India that has claimed more than 50 lives and alarmed the world. The hypothesis is that the earthquake may have uprooted underground rat populations that carry the fleas infected with the bacterium that causes bubonic plague and can lead to the pneumonic form of the disease that is spread through the air.

  11. Proceedings of the third U. S. national conference on earthquake engineering. Volume II

    SciTech Connect

    Not Available

    1986-01-01

    During the past quarter century the North American continent has experienced a number of damaging earthquakes, among which were the 1964 Alaska earthquake, the 1971 San Fernando, California, earthquake, and most recently the 1985 Mexico City earthquake. A large number of smaller earthquakes have occurred during this period, all of which, along with large earthquakes that have occurred in other parts of the world, serve to remind one that the earthquake hazard is real. In view of potential loss of life and the economic losses that could result from large earthquakes, it is important that the United States continue its vigorous efforts towards mitigating the hazards of earthquakes including developing and implementing safe and economic methods of earthquake-resistant design and construction. In the light of the foregoing observations it it fitting that this Third U.S. National Conference on Earthquake Engineering be held in 1986 at Charleston, South Carolina, on the one-hundred-year anniversary of the 1886 Charleston earthquake. Although intended primarily for participation by U.S. practitioners and researchers, participants from many other parts of the world are also present. From the more than 300 papers offered for publication and presentation, over 200 papers are published in the three volumes of Proceedings and the single volume of Post-Conference Proceedings.

  12. Origin of anomalous Earthquake Early Warning Parameter Values for earthquakes in the Ibero-Maghrebian Region

    NASA Astrophysics Data System (ADS)

    Carranza, Marta; Buforn, Elisa; Zollo, Aldo

    2015-04-01

    We have studied the anomalous values of the predominant period ?c and peak displacement Pd measured offline from the initial P-wave (3 sec time window) of several earthquakes occurred at the Ibero-Maghrebian region. Understanding the origin of these anomalous values is of a great importance in view of the development of an Earthquake Early Warning System (EEWS), since they can lead to missed and false alarms by a wrong estimation of the magnitude. In particular, we have observed lower ?c values at stations such as ESPR, EGRO or EADA, for earthquakes occurred at the SW of Iberian Peninsula and higher ?c for earthquakes occurred at S and SE of Iberian Peninsula. These anomalous values may be correlated with the ray path. Due to the large variability of attenuation in the whole region, different correction of Pd with distance must be used. We have analyzed the effect of expanding the P-wave time window for the magnitude estimation and explained the magnitude underestimation for the 2003 Algerian earthquake as the possible effect of an un-sufficient P-wave window length to measure the EEW parameters

  13. On near-source earthquake triggering

    USGS Publications Warehouse

    Parsons, T.; Velasco, A.A.

    2009-01-01

    When one earthquake triggers others nearby, what connects them? Two processes are observed: static stress change from fault offset and dynamic stress changes from passing seismic waves. In the near-source region (r ??? 50 km for M ??? 5 sources) both processes may be operating, and since both mechanisms are expected to raise earthquake rates, it is difficult to isolate them. We thus compare explosions with earthquakes because only earthquakes cause significant static stress changes. We find that large explosions at the Nevada Test Site do not trigger earthquakes at rates comparable to similar magnitude earthquakes. Surface waves are associated with regional and long-range dynamic triggering, but we note that surface waves with low enough frequency to penetrate to depths where most aftershocks of the 1992 M = 5.7 Little Skull Mountain main shock occurred (???12 km) would not have developed significant amplitude within a 50-km radius. We therefore focus on the best candidate phases to cause local dynamic triggering, direct waves that pass through observed near-source aftershock clusters. We examine these phases, which arrived at the nearest (200-270 km) broadband station before the surface wave train and could thus be isolated for study. Direct comparison of spectral amplitudes of presurface wave arrivals shows that M ??? 5 explosions and earthquakes deliver the same peak dynamic stresses into the near-source crust. We conclude that a static stress change model can readily explain observed aftershock patterns, whereas it is difficult to attribute near-source triggering to a dynamic process because of the dearth of aftershocks near large explosions.

  14. The b-value as an earthquake precursor: Spatiotemporal variations for the NW Himalayan region, India

    NASA Astrophysics Data System (ADS)

    Sushil, R.; Kumar, S.

    2011-12-01

    The northwest Himalayan region and the adjoining regions fall in the most intense seismic zone. Earthquakes of varying intensities have hit the region in the past and similar threats remain imminent. In the last 105 years, the main earthquakes occurred are the Kangra earthquake of 1905 (Ms=8.0), the Kinnaur earthquake of 1975 (M=6.8), Dharchula earthquake of 1980 (Mw=6.5), Uttarkashi earthquake of 1991 (Mb=6.6), Chamoli earthquake of 1999 (Mb=6.8) and the Kashmir earthquake of 2005 (Mw=7.6), which resulted in tremendous loss of life and property. The earthquakes occurrence possesses non-linear relation with respect to space and size. Spatiotemporal variations in b-Value are determined from 3846 well-located earthquakes, recorded at 10-19 seismic stations in Northwest Himalaya during 1995-2011. A systematic study of b-values in NW Himalaya has shown that within the vicinity of forthcoming large earthquakes there is initially a decrease and then increase in b after that return to normal. The Uttarkashi earthquake (Mb=6.5) and Chamoli earthquake (Mb=6.8) shows the same phenomenon. The results of this analysis will be discussed during the presentation of this paper.

  15. Influence of Solar Cycles on Earthquakes

    NASA Astrophysics Data System (ADS)

    Tavares, M.

    2011-12-01

    This research inspects possible influence of solar cycles on earthquakes through of statistical analyses. We also discussed the mechanism that would drive the occurrence of increasing of earthquakes during solar maxima. The study was based on worldwide earthquakes events during approximately four hundred years (1600-2010). The increase of earthquakes events followed the Maxima of Solar cycle, and also depends on the tectonic plate location. From 1600 until 1645 events increased during the Maxima in some of the tectonic plates as Pacific, Arabian and South America. The earthquakes analyzed during two grand solar minima, the Maunder (1645-1720) and the Dalton (1790-1820) showed a decrease in the number of earthquakes and the solar activity. It was observed during these minima a significant number of events at specific geological features. After the last minima (Dalton) the earthquakes pattern increased with solar maxima. The calculations showed that events increasing during solar maxima most in the Pacific, South America or Arabian until 1900. Since there were few records during these three centuries we needed additional analysis on modern data. We took the last four solar cycles events (1950-2010) and made similar calculations. The results agreed with the former calculations. It might be that the mechanism for the Sun-Earth connection relies on the solar wind speed. In both records (1600-1900) and (1950-2010) the results showed a significant increase in earthquakes events in some of the tectonic plates linked to solar maxima. The Solar wind energy striking the Earth's magnetosphere affects the entire environment because the pressure on the region increases and the magnetosphere shrinks sometimes four Earth's radii. This sudden compression causes earthquakes in specific plates. During the times of solar minima the pressure from the solar wind on the earth decreases, then the magnetosphere expands and earthquakes happen in a different pattern according to the geological feature on earth's surface less frequently. Solar driven events include coronal mass ejections (CME) and coronal holes, which are at a maximum during the descending phase of solar activity. The tectonic are important because there is heterogeneity in the crust and the tectonic stress depends on each region. The geo-effectiveness of solar wind from a coronal hole only depends on the position of the hole relative to the Earth and for the CMEs an additional factor is their velocity. The influence of these solar events could be detected from electromagnetic variations on the ground prior the earthquakes. The goal in this research was to show the solar events influenced the earthquakes and seismologic events following some special display and also how the Sun's activity played to make earthquakes increase. This paper discussed details of this mechanism, calculations and associated factors.

  16. The 1984 Morgan Hill, California, earthquake

    USGS Publications Warehouse

    Bakun, W.H.; Clark, M.M.; Cockerham, R.S.; Ellsworth, W.L.; Lindh, A.G.; Prescott, W.H.; Shakal, A.F.; Spudich, P.

    1984-01-01

    The Morgan Hill, California, earthquake (magnitude 6.1) of 24 April 1984 ruptured a 30-kilometer-long segment of the Calaveras fault zone to the east of San Jose. Although it was recognized in 1980 that an earthquake of magnitude 6 occurred on this segment in 1911 and that a repeat of this event might reasonably be expected, no short-term precursors were noted and so the time of the 1984 earthquake was not predicted. Unilateral rupture propagation toward the south-southeast and an energetic late source of seismic radiation located near the southeast end of the rupture zone contributed to the highly focused pattern of strong motion, including an exceptionally large horizontal acceleration of 1.29g at a site on a dam abutment near the southeast end of the rupture zone.

  17. Metrics for comparing dynamic earthquake rupture simulations

    USGS Publications Warehouse

    Barall, Michael; Harris, Ruth A.

    2014-01-01

    Earthquakes are complex events that involve a myriad of interactions among multiple geologic features and processes. One of the tools that is available to assist with their study is computer simulation, particularly dynamic rupture simulation. A dynamic rupture simulation is a numerical model of the physical processes that occur during an earthquake. Starting with the fault geometry, friction constitutive law, initial stress conditions, and assumptions about the condition and response of the near?fault rocks, a dynamic earthquake rupture simulation calculates the evolution of fault slip and stress over time as part of the elastodynamic numerical solution (?see the simulation description in the electronic supplement to this article). The complexity of the computations in a dynamic rupture simulation make it challenging to verify that the computer code is operating as intended, because there are no exact analytic solutions against which these codes results can be directly compared. One approach for checking if dynamic rupture computer codes are working satisfactorily is to compare each codes results with the results of other dynamic rupture codes running the same earthquake simulation benchmark. To perform such a comparison consistently, it is necessary to have quantitative metrics. In this paper, we present a new method for quantitatively comparing the results of dynamic earthquake rupture computer simulation codes.

  18. Northridge, CA Earthquake Damage

    USGS Multimedia Gallery

    The person in this image was a USGS employee at the time this was taken. Collection of USGS still images taken after the January 17, 1994 Northridge earthquake highlighting the damage to buildings and infrastructure....

  19. Nonlinear processes in earthquakes

    SciTech Connect

    Jones, E.M.; Frohlich, C.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Three-dimensional, elastic-wave-propagation calculations were performed to define the effects of near-source geologic structure on the degree to which seismic signals produced by earthquakes resemble {open_quotes}non-double-couple{close_quotes} sources. Signals from sources embedded in a subducting slab showed significant phase and amplitude differences compared with a {open_quotes}no-slab{close_quotes} case. Modifications to the LANL elastic-wave propagation code enabled improved simulations of path effects on earthquake and explosion signals. These simulations demonstrate that near-source, shallow, low-velocity basins can introduce earthquake-like features into explosion signatures through conversion of compressive (P-wave) energy to shear (S- and R-wave) modes. Earthquake sources simulated to date do not show significant modifications.

  20. To capture an earthquake

    SciTech Connect

    Ellsworth, W.L. )

    1990-11-01

    An earthquake model based on the theory of plate tectonics is presented. It is assumed that the plates behave elastically in response to slow, steady motions and the strains concentrate within the boundary zone between the plates. When the accumulated stresses exceed the bearing capacity of the rocks, the rocks break, producing an earthquake and releasing the accumulated stresses. As the steady movement of the plates continues, strain begins to reaccumulate. The cycle of strain accumulation and release is modeled using the motion of a block, pulled across a rough surface by a spring. A model earthquake can be predicted by taking into account a precursory event or the peak spring force prior to slip as measured in previous cycles. The model can be applied to faults, e.g., the San Andreas fault, if the past earthquake history of the fault and the rate of strain accumulation are known.

  1. Extending the ISC-GEM Global Earthquake Instrumental Catalogue

    NASA Astrophysics Data System (ADS)

    Di Giacomo, Domenico; Engdhal, Bob; Storchak, Dmitry; Villaseñor, Antonio; Harris, James

    2015-04-01

    After a 27-month project funded by the GEM Foundation (www.globalquakemodel.org), in January 2013 we released the ISC-GEM Global Instrumental Earthquake Catalogue (1900 2009) (www.isc.ac.uk/iscgem/index.php) as a special product to use for seismic hazard studies. The new catalogue was necessary as improved seismic hazard studies necessitate that earthquake catalogues are homogeneous (to the largest extent possible) over time in their fundamental parameters, such as location and magnitude. Due to time and resource limitation, the ISC-GEM catalogue (1900-2009) included earthquakes selected according to the following time-variable cut-off magnitudes: Ms=7.5 for earthquakes occurring before 1918; Ms=6.25 between 1918 and 1963; and Ms=5.5 from 1964 onwards. Because of the importance of having a reliable seismic input for seismic hazard studies, funding from GEM and two commercial companies in the US and UK allowed us to start working on the extension of the ISC-GEM catalogue both for earthquakes that occurred beyond 2009 and for earthquakes listed in the International Seismological Summary (ISS) which fell below the cut-off magnitude of 6.25. This extension is part of a four-year program that aims at including in the ISC-GEM catalogue large global earthquakes that occurred before the beginning of the ISC Bulletin in 1964. In this contribution we present the updated ISC GEM catalogue, which will include over 1000 more earthquakes that occurred in 2010 2011 and several hundreds more between 1950 and 1959. The catalogue extension between 1935 and 1949 is currently underway. The extension of the ISC-GEM catalogue will also be helpful for regional cross border seismic hazard studies as the ISC-GEM catalogue should be used as basis for cross-checking the consistency in location and magnitude of those earthquakes listed both in the ISC GEM global catalogue and regional catalogues.

  2. Variation of P-wave velocity before the Bear Valley, California, earthquake of 24 February 1972

    USGS Publications Warehouse

    Robinson, R.; Wesson, R.L.; Ellsworth, W.L.

    1974-01-01

    Residuals for P-wave traveltimes at a seismograph station near Bear Valley, California, for small, precisely located local earthquakes at distances of 20 to 70 kilometers show a sharp increase of nearly 0.3 second about 2 months before a magnitude 5.0 earthquake that occurred within a few kilometers of the station. This indicates that velocity changes observed elsewhere premonitory to earthquakes, possibly related to dilatancy, occur along the central section of the San Andreas fault system.

  3. On the origin of electrotelluric disturbances prior to an earthquake in Kalamata, Greece

    NASA Astrophysics Data System (ADS)

    Gershenzon, N.; Gokhberg, M.

    1993-08-01

    A long distance (200 km) electromagnetic signal occured at Keratea (near Athens), few days prior to the September 13th 1986, Kalamata earthquake. We suggest an explanation based on the fact that long range stress occuring before an earthquake should create local electrical potential gradients in heterogeneous ground at great distances. This could be a general explanation for the origin of electrical telluric signals appearing before an earthquake.

  4. Great earthquakes, seismicity gaps and potential for earthquake disaster along the Himalaya plate boundary

    NASA Astrophysics Data System (ADS)

    Khattri, K. N.

    1987-06-01

    Analysis of the space-time patterns of seismicity in the Himalaya plate boundary has established the existence of three seismic gaps: (1) The "Kashmir gap" lying west of the 1905 Kangra earthquake; (2) the "Central gap", situated between the 1905 Kangra and the 1934 Bihar earthquakes; (3) the "Assam gap" between the 1897 and 1950 Assam earthquakes. This study has shown that the above great earthquakes were preceded as well as followed by long periods (? 19 years) of decreased levels of seismic activity in the epicentral regions. Remarkable decrease in the seismicity following the year 1970 has been observed in the western half of the Central gap as well as in the Assam gap. Local seismic investigation in the Assam gap confirms this feature and the seismicity suggests the existence there of an asperity. The local seismic investigations in Garhwal Himalaya have shown that the small earthquakes are confined to the upper 6-8 km of the crust and may have strike-slip motions. These earthquakes occur in a region where teleseismically recorded events were few.

  5. Earthquakes and Tremors Remotely Triggered by the 2011, M9.0 Japan Earthquake's Seismic Waves

    NASA Astrophysics Data System (ADS)

    Gonzalez-Huizar, H.; Velasco, A. A.

    2011-12-01

    Evidence suggests that large earthquakes can trigger seismicity at large distances. The passing of seismic waves can change the stress conditions on previously over stressed regions causing the triggering of small earthquakes and tremors, this phenomenon is known as remote or dynamic triggering seismicity. Here we present the results of a global search of earthquakes and tremors potentially triggered by the surfaces waves from the 2011, M9.0 Tohoku, Japan earthquake. Global seismic networks and catalogs were used to search for instance of instantaneous triggering of earthquakes and tremors during the passing of the seismic waves, as well as for significant changes in local seismic rate after the passing of the waves at several regions of interest. Instantaneous triggering of tremor and earthquakes was observed in places as US, Taiwan, Armenia, Russia, Ecuador and the Caribbean. Important local seismic rate changes were observed in places as Mexico and the Solomon Sea. In order to have a better understanding of this phenomenon, we analyzed the seismic waves and modeled the stress changes caused by them and their relationship with the local stress where triggering occurred.

  6. Earthquake-volcano interaction imaged by coda wave interferometry

    NASA Astrophysics Data System (ADS)

    Battaglia, Jean; Mtaxian, Jean-Philippe; Garaebiti, Esline

    2012-06-01

    Large earthquakes are often assumed to influence the eruptive activity of volcanoes. A major challenge to better understand the causal relationship between these phenomena is to detect and image, in detail, all induced changes, including subtle, non-eruptive responses. We show that coda wave interferometry can be used to image such earthquake-induced responses, as recorded at Yasur volcano (Vanuatu) following a magnitude 7.3 earthquake which occurred 80 km from its summit. We use repeating Long-Period events to show that the earthquake caused a sudden seismic velocity drop, followed by a slow partial recovery process. The spatial distribution of the response amplitude indicates an effect centered on the volcano. Our result demonstrates that, even if no major change in eruptive activity is observed, volcanoes will be affected by the propagation of large amplitude seismic waves through their structure, suggesting that Earthquake-volcano interaction is likely a more common phenomenon than previously believed.

  7. Periodic slow slip triggers megathrust zone earthquakes in northeastern Japan.

    PubMed

    Uchida, Naoki; Iinuma, Takeshi; Nadeau, Robert M; Brgmann, Roland; Hino, Ryota

    2016-01-29

    Both aseismic and seismic slip accommodate relative motion across partially coupled plate-boundary faults. In northeastern Japan, aseismic slip occurs in the form of decelerating afterslip after large interplate earthquakes and as relatively steady slip on uncoupled areas of the subduction thrust. Here we report on a previously unrecognized quasi-periodic slow-slip behavior that is widespread in the megathrust zone. The repeat intervals of the slow slip range from 1 to 6 years and often coincide with or precede clusters of large [magnitude (M) ? 5] earthquakes, including the 2011 M 9 Tohoku-oki earthquake. These results suggest that inherently periodic slow-slip events result in periodic stress perturbations and modulate the occurrence time of larger earthquakes. The periodicity in the slow-slip rate has the potential to help refine time-dependent earthquake forecasts. PMID:26823425

  8. An appraisal of aftershocks behavior for large earthquakes in Persia

    NASA Astrophysics Data System (ADS)

    Nemati, Majid

    2014-01-01

    This study focuses on the distribution of aftershocks in both location and magnitude for recent earthquakes in Iran. 43 Earthquakes are investigated, using data from the global International Seismological Center (ISC) seismic catalogue and from the regional earthquake catalogue of the Institute of Geophysics, University of Tehran (IGUT) between 1961-2006 and 2006-2012 respectively. We only consider the earthquakes with magnitude greater than 5.0. The majority of these events are intracontinental, occurring over four seismotectonic provinces across Iran. Processing aftershock sequences reported by both catalogues with cut-off magnitude of 2.5 and a sequence duration of 70 days, leads us to define a spatial horizontal area (A) occupied with the aftershocks as a function of mainshock magnitude (M) for Persian earthquakes: ISC: Log10(A) = 0.45MS + 0.23; IGUT: Log10(A) = 0.25MN + 1.7.

  9. Intraplate earthquakes and the state of stress in oceanic lithosphere

    NASA Technical Reports Server (NTRS)

    Bergman, Eric A.

    1986-01-01

    The dominant sources of stress relieved in oceanic intraplate earthquakes are investigated to examine the usefulness of earthquakes as indicators of stress orientation. The primary data for this investigation are the detailed source studies of 58 of the largest of these events, performed with a body-waveform inversion technique of Nabelek (1984). The relationship between the earthquakes and the intraplate stress fields was investigated by studying, the rate of seismic moment release as a function of age, the source mechanisms and tectonic associations of larger events, and the depth-dependence of various source parameters. The results indicate that the earthquake focal mechanisms are empirically reliable indicators of stress, probably reflecting the fact that an earthquake will occur most readily on a fault plane oriented in such a way that the resolved shear stress is maximized while the normal stress across the fault, is minimized.

  10. The Parkfield experiment; capturing what happens in an earthquake

    USGS Publications Warehouse

    Hickman, Steve; Langbein, John; Stauffer, Peter H.

    2004-01-01

    To better understand what happens on and near a fault before, during, and after an earthquake, the U.S. Geological Survey (USGS) and the California Geological Survey began the Parkfield Earthquake Experiment in the 1980's. Researchers from the USGS and collaborating institutions have created a dense network of instruments on the San Andreas Fault at Parkfield, California, where moderate earthquakes have occurred at fairly regular intervals. Data from these instruments are revealing the earthquake process in unprecedented detail and will aid in predicting the time and severity of future shocks. The USGS and the National Science Foundation plan to expand the Parkfield Experiment by drilling a deep borehole and installing instruments at the actual depths where earthquakes initiate, creating a San Andreas Fault Observatory at Depth.

  11. Real-time earthquake monitoring using a search engine method

    PubMed Central

    Zhang, Jie; Zhang, Haijiang; Chen, Enhong; Zheng, Yi; Kuang, Wenhuan; Zhang, Xiong

    2014-01-01

    When an earthquake occurs, seismologists want to use recorded seismograms to infer its location, magnitude and source-focal mechanism as quickly as possible. If such information could be determined immediately, timely evacuations and emergency actions could be undertaken to mitigate earthquake damage. Current advanced methods can report the initial location and magnitude of an earthquake within a few seconds, but estimating the source-focal mechanism may require minutes to hours. Here we present an earthquake search engine, similar to a web search engine, that we developed by applying a computer fast search method to a large seismogram database to find waveforms that best fit the input data. Our method is several thousand times faster than an exact search. For an Mw 5.9 earthquake on 8 March 2012 in Xinjiang, China, the search engine can infer the earthquake’s parameters in <1 s after receiving the long-period surface wave data. PMID:25472861

  12. Oklahoma’s recent earthquakes and saltwater disposal

    PubMed Central

    Walsh, F. Rall; Zoback, Mark D.

    2015-01-01

    Over the past 5 years, parts of Oklahoma have experienced marked increases in the number of small- to moderate-sized earthquakes. In three study areas that encompass the vast majority of the recent seismicity, we show that the increases in seismicity follow 5- to 10-fold increases in the rates of saltwater disposal. Adjacent areas where there has been relatively little saltwater disposal have had comparatively few recent earthquakes. In the areas of seismic activity, the saltwater disposal principally comes from “produced” water, saline pore water that is coproduced with oil and then injected into deeper sedimentary formations. These formations appear to be in hydraulic communication with potentially active faults in crystalline basement, where nearly all the earthquakes are occurring. Although most of the recent earthquakes have posed little danger to the public, the possibility of triggering damaging earthquakes on potentially active basement faults cannot be discounted. PMID:26601200

  13. Simulating Earthquake Early Warning Systems in the Classroom as a New Approach to Teaching Earthquakes

    NASA Astrophysics Data System (ADS)

    D'Alessio, M. A.

    2010-12-01

    A discussion of P- and S-waves seems an ubiquitous part of studying earthquakes in the classroom. Textbooks from middle school through university level typically define the differences between the waves and illustrate the sense of motion. While many students successfully memorize the differences between wave types (often utilizing the first letter as a memory aide), textbooks rarely give tangible examples of how the two waves would "feel" to a person sitting on the ground. One reason for introducing the wave types is to explain how to calculate earthquake epicenters using seismograms and travel time charts -- very abstract representations of earthquakes. Even when the skill is mastered using paper-and-pencil activities or one of the excellent online interactive versions, locating an epicenter simply does not excite many of our students because it evokes little emotional impact, even in students located in earthquake-prone areas. Despite these limitations, huge numbers of students are mandated to complete the task. At the K-12 level, California requires that all students be able to locate earthquake epicenters in Grade 6; in New York, the skill is a required part of the Regent's Examination. Recent innovations in earthquake early warning systems around the globe give us the opportunity to address the same content standard, but with substantially more emotional impact on students. I outline a lesson about earthquakes focused on earthquake early warning systems. The introductory activities include video clips of actual earthquakes and emphasize the differences between the way P- and S-waves feel when they arrive (P arrives first, but is weaker). I include an introduction to the principle behind earthquake early warning (including a summary of possible uses of a few seconds warning about strong shaking) and show examples from Japan. Students go outdoors to simulate P-waves, S-waves, and occupants of two different cities who are talking to one another on cell phones. The culminating activity is for students to "design" an early warning system that will protect their school from nearby earthquakes. The better they design the system, the safer they will be. Each team of students receives a map of faults in the area and possible sites for real-time seismometer installation. Given a fixed budget, they must select the best sites for detecting a likely earthquake. After selecting their locations, teams face-off two-by-two in a tournament of simulated earthquakes. We created animations of a few simulated earthquakes for our institution and have plans to build a web-based version that will allow others to customize the location to their own location and facilitate the competition between teams. Earthquake early warning is both cutting-edge and has huge societal benefits. Instead of teaching our students how to locate epicenters after an earthquake has occurred, we can teach the same content standards while showing them that earthquake science can really save lives.

  14. The deep resistivity variation during water loading and unloading and induced earthquake in the Longtan reservoir, Guangxi Province,China

    NASA Astrophysics Data System (ADS)

    Zhan, Y.; Wang, L.; Wang, J.; Qiao, Q.

    2011-12-01

    Longtan reservoir is located in the northwest of Guangxi province in South China. The reservoir began to store water since 2006. Now the current generation has been completed. As the reservoir water level rise, earthquakes frequently happened, and the distribution of these earthquakes is concentrated in four clustering areas. In order to understand the relationship between reservoir earthquakes and reservoir water level change. Five times of magnetotelluric measurements were carried out during loading and unloading of the Longtan reservoir from 2009 to 2010. The surveys were conducted at 4 sites (Jiaobitun,Pingshang,Zhongliangping and Xiangyang sites)with a frequency band of 320Hz-1000s and The 4 sites were located in an earthquake clustering areas. Moreover along the two NW-trending Profiles, 34 MT sites had measured and the two MT profiles across the main reservoir earthquake-prone areas. Combined with the regional deep electrical structure, the analysis of measurements of the reservoir suggests that the five measured apparent resistivity values at the three sites Pingshang, Zhongliangping and Xiangyang, which bear same lithology, were roughly the same, with the minimum at the low frequency band less than 1 Hz when the water level of the reservoir was the highest. While the measured apparent resistivity values at the Jiaobitun site of distinct lithology was different from the other three sites, and did not change considerably during loading and unloading of the reservoir. It implies that the seepage behaviors of reservoir water depend on lithology and deep electric structure. When the lithology and deep electric structure are largely consistent, the water seepage is primarily controlled by the gravity weight of reservoir water. Among the sources of 4 earthquake clustering areas, three are located in the lower portion of the Permian(P1) and Carboniferous(C) strata with low resistivity, attributed to the induced events associated with water in karsts. The seismic event with the maximum magnitude occurred within the lower part of high-resistivity body, of which the width tapers downward. It is speculated that the earthquakes in this reservoir can be attributed to strain accumulation in the high-resistivity body due to the increase of water pressure after water storage and the water permeation. This study indicates that electromagnetic method can be utilized to study processes of reservoir water loading and unloading and water filtration, and the type, mechanism and setting of reservoir induced earthquakes. This research was supported by the "Eleventh Five-Year" national scientific and technological support projects (2008BAC38B033).

  15. Understanding Earthquake Hazard & Disaster in Himalaya - A Perspective on Earthquake Forecast in Himalayan Region of South Central Tibet

    NASA Astrophysics Data System (ADS)

    Shanker, D.; Paudyal, ,; Singh, H.

    2010-12-01

    It is not only the basic understanding of the phenomenon of earthquake, its resistance offered by the designed structure, but the understanding of the socio-economic factors, engineering properties of the indigenous materials, local skill and technology transfer models are also of vital importance. It is important that the engineering aspects of mitigation should be made a part of public policy documents. Earthquakes, therefore, are and were thought of as one of the worst enemies of mankind. Due to the very nature of release of energy, damage is evident which, however, will not culminate in a disaster unless it strikes a populated area. The word mitigation may be defined as the reduction in severity of something. The Earthquake disaster mitigation, therefore, implies that such measures may be taken which help reduce severity of damage caused by earthquake to life, property and environment. While earthquake disaster mitigation usually refers primarily to interventions to strengthen the built environment, and earthquake protection is now considered to include human, social and administrative aspects of reducing earthquake effects. It should, however, be noted that reduction of earthquake hazards through prediction is considered to be the one of the effective measures, and much effort is spent on prediction strategies. While earthquake prediction does not guarantee safety and even if predicted correctly the damage to life and property on such a large scale warrants the use of other aspects of mitigation. While earthquake prediction may be of some help, mitigation remains the main focus of attention of the civil society. Present study suggests that anomalous seismic activity/ earthquake swarm existed prior to the medium size earthquakes in the Nepal Himalaya. The mainshocks were preceded by the quiescence period which is an indication for the occurrence of future seismic activity. In all the cases, the identified episodes of anomalous seismic activity were characterized by an extremely high annual earthquake frequency as compared to the preceding normal and the following gap episodes, and is the characteristics of the events in such an episode is causally related with the magnitude and the time of occurrence of the forthcoming earthquake. It is observed here that for the shorter duration of the preparatory time period, there will be the smaller mainshock, and vice-versa. The Western Nepal and the adjoining Tibet region are potential for the future medium size earthquakes. Accordingly, it has been estimated here that an earthquake with M 6.5 0.5 may occur at any time from now onwards till December 2011 in the Western Nepal within an area bounded by 29.3-30.5 N and 81.2-81.9 E, in the focal depth range 10 -30 km.

  16. Injection-induced earthquakes.

    PubMed

    Ellsworth, William L

    2013-07-12

    Earthquakes in unusual locations have become an important topic of discussion in both North America and Europe, owing to the concern that industrial activity could cause damaging earthquakes. It has long been understood that earthquakes can be induced by impoundment of reservoirs, surface and underground mining, withdrawal of fluids and gas from the subsurface, and injection of fluids into underground formations. Injection-induced earthquakes have, in particular, become a focus of discussion as the application of hydraulic fracturing to tight shale formations is enabling the production of oil and gas from previously unproductive formations. Earthquakes can be induced as part of the process to stimulate the production from tight shale formations, or by disposal of wastewater associated with stimulation and production. Here, I review recent seismic activity that may be associated with industrial activity, with a focus on the disposal of wastewater by injection in deep wells; assess the scientific understanding of induced earthquakes; and discuss the key scientific challenges to be met for assessing this hazard. PMID:23846903

  17. Fundamental questions of earthquake statistics, source behavior, and the estimation of earthquake probabilities from possible foreshocks

    USGS Publications Warehouse

    Michael, Andrew J.

    2012-01-01

    Estimates of the probability that an ML 4.8 earthquake, which occurred near the southern end of the San Andreas fault on 24 March 2009, would be followed by an M 7 mainshock over the following three days vary from 0.0009 using a Gutenberg–Richter model of aftershock statistics (Reasenberg and Jones, 1989) to 0.04 using a statistical model of foreshock behavior and long‐term estimates of large earthquake probabilities, including characteristic earthquakes (Agnew and Jones, 1991). I demonstrate that the disparity between the existing approaches depends on whether or not they conform to Gutenberg–Richter behavior. While Gutenberg–Richter behavior is well established over large regions, it could be violated on individual faults if they have characteristic earthquakes or over small areas if the spatial distribution of large‐event nucleations is disproportional to the rate of smaller events. I develop a new form of the aftershock model that includes characteristic behavior and combines the features of both models. This new model and the older foreshock model yield the same results when given the same inputs, but the new model has the advantage of producing probabilities for events of all magnitudes, rather than just for events larger than the initial one. Compared with the aftershock model, the new model has the advantage of taking into account long‐term earthquake probability models. Using consistent parameters, the probability of an M 7 mainshock on the southernmost San Andreas fault is 0.0001 for three days from long‐term models and the clustering probabilities following the ML 4.8 event are 0.00035 for a Gutenberg–Richter distribution and 0.013 for a characteristic‐earthquake magnitude–frequency distribution. Our decisions about the existence of characteristic earthquakes and how large earthquakes nucleate have a first‐order effect on the probabilities obtained from short‐term clustering models for these large events.

  18. Antimicrobial susceptibility of clinical isolates from earthquake victims in Wenchuan.

    PubMed

    Kang, M; Xie, Y; Mintao, C; Chen, Z; Chen, H; Fan, H; Chen, W; Guo, X

    2009-01-01

    On 12 May 2008, an earthquake measuring 8.0 on the Richter scale struck Wenchuan County, Sichuan, China. Between 12 May and 11 June, 1823 victims were hospitalized in West China Hospital. These patients were severely injured, and most of their wounds were contaminated. Here, the results of bacteriological identification and antibiotic susceptibility testing of 725 non-duplicate isolates from earthquake victims are presented. Gram-negative bacilli were most frequently isolated (71.3%). Only 18.9% of isolates were Gram-positive bacteria; Candida spp. accounted for 9.7%, and Gram-negative cocci for 0.1%. After anaerobic culture, four Clostridium sordellii strains and one Clostridium bifermentans strain were isolated from deep wounds. Specimen culture from earthquake victims revealed a spectrum of pathogens and antibiotic susceptibilities that was different from that usually encountered in West China Hospital, especially concerning methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase producers, and multidrug-resistant (MDR) non-fermenting Gram-negative bacilli. The pathophysiology of the injuries in earthquake victims was different from that in the patients who were not earthquake victims. A combination of environmental bacteria with a high proportion of Gram-negative bacteria was often observed in the earthquake victims. Approximately 26% of all earthquake victims were shown to be carriers of MDR microorganisms. Therefore, appropriate microbiological assessment upon admission, and identification of patients to be put in quarantine, is of paramount importance. PMID:19220339

  19. Slow earthquakes associated with fault healing on a serpentinized plate interface

    PubMed Central

    Katayama, Ikuo; Iwata, Mutsumi; Okazaki, Keishi; Hirauchi, Ken-ichi

    2013-01-01

    Slow earthquakes that occur at subduction zones are distinct from regular earthquakes in terms of their slip behavior. We consider this difference to relate to localized hydration reactions at the plate interface that influence the frictional properties. The results of laboratory friction experiments indicate that simulated serpentine faults are characterized by a low healing rate and large slip-weakening distance compared with unaltered dry fault patches. These results are consistent with the slip mechanism of slow earthquakes, indicating that a locally serpentinized plate interface could trigger slow earthquakes, assisted by pore pressure build-up, whereas unaltered dry patches that remain strongly coupled are potential sites of regular earthquakes.

  20. Hidden Markov Modeling of Waiting Times in the 1985 Yellowstone Earthquake Swarm

    NASA Astrophysics Data System (ADS)

    Li, Yumei; Anderson-Sprecher, Richard

    2013-05-01

    Earthquake swarms occur in many regions of the world. The study of earthquake swarms is very limited, and most contributions are descriptive. In this paper we propose use of a hidden Markov model to estimate the distribution of waiting times for swarm earthquakes and apply this approach to the largest earthquake swarm in the history of the Yellowstone area. Hidden Markov modeling is superior to modeling using either single distributions or finite mixture distributions because of the heterogeneity of data and temporal dependencies in earthquake sequences.

  1. Predicting earthquakes along the major plate tectonic boundaries in the Pacific

    USGS Publications Warehouse

    Spall, H.

    1978-01-01

    In an article in the last issue of the Earthquake Information Bulletin ("Earthquakes and Plate Tectonics," by Henry Spall), we saw how 90 percent of the world's earthquakes occur at the margins of the Earth's major crustal plates. however, when we look at the distribution of earthquakes in detail, we see that a number of nearly aseismic regions, or seismic gaps, can be found along the present-day plate boundaries. Why is this? And can we regard these areas as being more likely to be the sites for future larger earthquakes than those segments of the plate boundaries that have ruptured recently. 

  2. Polar motion, atmospheric angular momentum excitation and earthquakes - Correlations and significance

    NASA Technical Reports Server (NTRS)

    Preisig, Joseph R.

    1992-01-01

    Equatorial atmospheric angular momentum (AAM) excitation functions and polar motion excitation functions (derived by Kalman filtering Very Long Baseline Interferometry polar motion estimates) are compared with the times of 1984-mid-1988 large earthquakes (magnitude greater than or equal to 7.5). There is a moderate correlation between times of large earthquakes and peaks in polar motion excitation. A strong correlation exists between the times of large earthquakes and large peaks in equatorial AAM amplitude; such a correlation is evident for six out of the eight large earthquakes occurring over the studied time interval. The AAM results indicate potential for the temporal prediction of large/great earthquakes.

  3. Statistical distributions of earthquake numbers: consequence of branching process

    NASA Astrophysics Data System (ADS)

    Kagan, Yan Y.

    2010-03-01

    We discuss various statistical distributions of earthquake numbers. Previously, we derived several discrete distributions to describe earthquake numbers for the branching model of earthquake occurrence: these distributions are the Poisson, geometric, logarithmic and the negative binomial (NBD). The theoretical model is the `birth and immigration' population process. The first three distributions above can be considered special cases of the NBD. In particular, a point branching process along the magnitude (or log seismic moment) axis with independent events (immigrants) explains the magnitude/moment-frequency relation and the NBD of earthquake counts in large time/space windows, as well as the dependence of the NBD parameters on the magnitude threshold (magnitude of an earthquake catalogue completeness). We discuss applying these distributions, especially the NBD, to approximate event numbers in earthquake catalogues. There are many different representations of the NBD. Most can be traced either to the Pascal distribution or to the mixture of the Poisson distribution with the gamma law. We discuss advantages and drawbacks of both representations for statistical analysis of earthquake catalogues. We also consider applying the NBD to earthquake forecasts and describe the limits of the application for the given equations. In contrast to the one-parameter Poisson distribution so widely used to describe earthquake occurrence, the NBD has two parameters. The second parameter can be used to characterize clustering or overdispersion of a process. We determine the parameter values and their uncertainties for several local and global catalogues, and their subdivisions in various time intervals, magnitude thresholds, spatial windows, and tectonic categories. The theoretical model of how the clustering parameter depends on the corner (maximum) magnitude can be used to predict future earthquake number distribution in regions where very large earthquakes have not yet occurred.

  4. Acute Myocardial Infarction and Stress Cardiomyopathy following the Christchurch Earthquakes

    PubMed Central

    Chan, Christina; Elliott, John; Troughton, Richard; Frampton, Christopher; Smyth, David; Crozier, Ian; Bridgman, Paul

    2013-01-01

    Background Christchurch, New Zealand, was struck by 2 major earthquakes at 4:36am on 4 September 2010, magnitude 7.1 and at 12:51pm on 22 February 2011, magnitude 6.3. Both events caused widespread destruction. Christchurch Hospital was the region's only acute care hospital. It remained functional following both earthquakes. We were able to examine the effects of the 2 earthquakes on acute cardiac presentations. Methods Patients admitted under Cardiology in Christchurch Hospital 3 week prior to and 5 weeks following both earthquakes were analysed, with corresponding control periods in September 2009 and February 2010. Patients were categorised based on diagnosis: ST elevation myocardial infarction, Non ST elevation myocardial infarction, stress cardiomyopathy, unstable angina, stable angina, non cardiac chest pain, arrhythmia and others. Results There was a significant increase in overall admissions (p<0.003), ST elevation myocardial infarction (p<0.016), and non cardiac chest pain (p<0.022) in the first 2 weeks following the early morning September earthquake. This pattern was not seen after the early afternoon February earthquake. Instead, there was a very large number of stress cardiomyopathy admissions with 21 cases (95% CI 2.6–6.4) in 4 days. There had been 6 stress cardiomyopathy cases after the first earthquake (95% CI 0.44–2.62). Statistical analysis showed this to be a significant difference between the earthquakes (p<0.05). Conclusion The early morning September earthquake triggered a large increase in ST elevation myocardial infarction and a few stress cardiomyopathy cases. The early afternoon February earthquake caused significantly more stress cardiomyopathy. Two major earthquakes occurring at different times of day differed in their effect on acute cardiac events. PMID:23844213

  5. Information Needs While A Disaster Is Occurring

    NASA Astrophysics Data System (ADS)

    Perry, S. C.

    2010-12-01

    Evidence from recent earthquakes, wildfires, and debris flows in southern California indicates that many people - local officials as well as residents and visitors - lack important understanding during the time that a disaster is unfolding, a time of uncertainty and confusion. While some of the uncertainty is inherent, some could be alleviated. Physical scientists and engineers know what to expect as the event unfolds. Social scientists know how humans will react during a disaster, and how to effectively communicate the warnings or evacuation orders that may precede it. Such knowledge can improve public safety. As just a few of many examples: - Based on questions posed at numerous public talks, many individuals who practice "Drop Cover and Hold" during earthquake drills do not understand what they are protecting themselves against, and thus cannot determine what to do when an earthquake strikes and they have no cover available. Similarly, they do not know how to act during the aftershocks that follow. - The 2009 Station Fire in the San Gabriel Mountains put foothills communities at risk, first from the wildfire and then from debris flows. Some neighborhoods received multiple evacuation notices during a few days or months. Local officials have expressed frustration and concern about an evacuation compliance rate that is steadily dropping and is now below 50%. The debris flow danger will persist over the next 2-4 winters yet evacuation compliance may drop lower still. - On February 6, 2010, a significant rainstorm brought the threat of imminent debris flows to areas burned by the Station Fire. In one neighborhood, residents loaded their cars with important belongings then waited for indications that they should evacuate. Powerful debris flows suddenly appeared, sweeping the cars downhill and destroying both cars and belongings. Some residents did understand that rainfall intensity would control the generation of debris flows in that storm. But they didn't understand that rainfall intensity at their homes might be less than the intensity up in the mountains where the debris flows would start. Nor did they know that debris flows travel too quickly to be outrun. These and many other examples indicate need for social and natural scientists to increase awareness of what to expect when the disaster strikes. This information must be solidly understood before the event occurs - while a disaster is unfolding there are no teachable moments. Case studies indicate that even those who come into a disaster well educated about the phenomenon can struggle to apply what they know when the real situation is at hand. In addition, psychological studies confirm diminished ability to comprehend information at times of stress.

  6. Analysis of Landslides Triggered by October 2005, Kashmir Earthquake

    PubMed Central

    Mahmood, Irfan; Qureshi, Shahid Nadeem; Tariq, Shahina; Atique, Luqman; Iqbal, Muhammad Farooq

    2015-01-01

    Introduction: The October 2005, Kashmir earthquake main event was triggered along the Balakot-Bagh Fault which runs from Bagh to Balakot, and caused more damages in and around these areas. Major landslides were activated during and after the earthquake inflicting large damages in the area, both in terms of infrastructure and casualties. These landslides were mainly attributed to the minimum threshold of the earthquake, geology of the area, climatologic and geomorphologic conditions, mudflows, widening of the roads without stability assessment, and heavy rainfall after the earthquake. These landslides were mainly rock and debris falls. Hattian Bala rock avalanche was largest landslide associated with the earthquake which completely destroyed a village and blocked the valley creating a lake. Discussion: The present study shows that the fault rupture and fault geometry have direct influence on the distribution of landslides and that along the rupture zone a high frequency band of landslides was triggered. There was an increase in number of landslides due to 2005 earthquake and its aftershocks and that most of earthquakes have occurred along faults, rivers and roads. It is observed that the stability of landslide mass is greatly influenced by amplitude, frequency and duration of earthquake induced ground motion. Most of the slope failures along the roads resulted from the alteration of these slopes during widening of the roads, and seepages during the rainy season immediately after the earthquake. Conclusion: Landslides occurred mostly along weakly cemented and indurated rocks, colluvial sand and cemented soils. It is also worth noting that fissures and ground crack which were induced by main and after shock are still present and they pose a major potential threat for future landslides in case of another earthquake activity or under extreme weather conditions. PMID:26366324

  7. Magnitude 8.1 Earthquake off the Solomon Islands

    NASA Technical Reports Server (NTRS)

    2007-01-01

    On April 1, 2007, a magnitude 8.1 earthquake rattled the Solomon Islands, 2,145 kilometers (1,330 miles) northeast of Brisbane, Australia. Centered less than ten kilometers beneath the Earth's surface, the earthquake displaced enough water in the ocean above to trigger a small tsunami. Though officials were still assessing damage to remote island communities on April 3, Reuters reported that the earthquake and the tsunami killed an estimated 22 people and left as many as 5,409 homeless. The most serious damage occurred on the island of Gizo, northwest of the earthquake epicenter, where the tsunami damaged the hospital, schools, and hundreds of houses, said Reuters. This image, captured by the Landsat-7 satellite, shows the location of the earthquake epicenter in relation to the nearest islands in the Solomon Island group. Gizo is beyond the left edge of the image, but its triangular fringing coral reefs are shown in the upper left corner. Though dense rain forest hides volcanic features from view, the very shape of the islands testifies to the geologic activity of the region. The circular Kolombangara Island is the tip of a dormant volcano, and other circular volcanic peaks are visible in the image. The image also shows that the Solomon Islands run on a northwest-southeast axis parallel to the edge of the Pacific plate, the section of the Earth's crust that carries the Pacific Ocean and its islands. The earthquake occurred along the plate boundary, where the Australia/Woodlark/Solomon Sea plates slide beneath the denser Pacific plate. Friction between the sinking (subducting) plates and the overriding Pacific plate led to the large earthquake on April 1, said the United States Geological Survey (USGS) summary of the earthquake. Large earthquakes are common in the region, though the section of the plate that produced the April 1 earthquake had not caused any quakes of magnitude 7 or larger since the early 20th century, said the USGS.

  8. Cluster analysis of earthquake swarms - results from West Bohemia and South-West Iceland

    NASA Astrophysics Data System (ADS)

    Čermáková, Hana; Cesca, Simone; Horálek, Josef

    2015-04-01

    Earthquake swarms are specific type of seismic activity when strain energy is released in numerous mostly shallow earthquakes, which are missing a single large event; instead a few dominant earthquakes reach similar magnitudes so that smaller events are not associated with any identifiable mainshock. Earthquake swarms distinctively cluster in time and space and last from several hours to several months. They occur at boundaries of the lithospheric plates (interplate), within the plates (intraplate), and they are very often related to the volcanic areas, geothermal fields and ocean ridges. In our study we explored the behaviour of earthquake swarms within a tectonic plate, in a boundary of tectonic plates and in volcanic areas in order to understand why the energy is released successively by sequences of small events in contrast to mainshock-aftershock earthquakes. We used catalogue data from West Bohemia-Vogtland region (WB) situated within a tectonic plate, and three different tectonic basis in South-West Iceland (SWI), namely boundary of tectonic plates (Krísuvík), the edge of a zone where typically mainshock-aftershock earthquakes occur (Olfus, South Iceland Sesmic Zone) and the volcanic area (Hengill). In case of WB we analyzed two swarms, 2000 and 2008, which occurred on the same fault segments. We analyzed distribution of events in a view of a spatial metric obtained from relative locations and time metric (in case of WB and SWI), and a focal mechanism metric based on double couple (DC) solutions (in case of WB). For this purpose we used clustering method by Cesca et al. (2014). The results are strongly affected by the subjective choice of two parameters which describe the desired density of points to infer a cluster. For the tested applications, we repeated the clustering several times to decide the best combination of these parameters. The cluster analysis applied to the double-difference locations disclosed several separate clusters in each area investigated which indicates that in all such different tectonic environments the swarms activate a number of smaller fault segments rather than one main fault. The time clustering discovered several separate phases in time which are characterized by abrupt increase of activity in a view of number of events and their magnitude. In case of WB, both 2000 and 2008 swarms show the same pattern. One significant and several smaller clusters appeared by processing of locations. From the analysis based on focal mechanisms we obtained three main mechanisms (oblique-normal, oblique-thrust and thrust faulting). For 2008 we got one additional mechanism appearing on a fault segment which was not activated in 2000 (thrust faulting with different strike). Strikes and dips of the focal mechanisms correspond to geometry of fault segments which are identified by the clustering method applied to the locations. The main fault segment is characterized by the most frequent mechanism (oblique-normal with strike and dip of about 170° and 80°). However, in its northern part, on its edge and sometime even inside the segment focal mechanisms differ significantly. This supports an idea that earthquake swarms occur on short fault segments with heterogeneous stress. References: Cesca S, Sen AT, Dahm T (2014) "Seismicity monitoring by cluster analysis of moment tensors", Geophys. J. Int., 196 (3):1813-1826

  9. Re-examination of large 20th century earthquakes along the southern Japan trench

    NASA Astrophysics Data System (ADS)

    Murotani, S.; Satake, K.

    2012-12-01

    We re-examine hypocenters, focal mechanisms and fault models for large earthquakes off Fukushima and off Boso regions along the southern Japan trench. The 1938 off Fukushima earthquakes, which consist of five earthquakes of Mjma ranging from 6.9 to 7.5, occurred in the southern part of the 2011 Tohoku earthquake source, where many M~6 aftershocks occurred since March 2011. To the south, off Boso region, the 1927 (Mjma 6.9) and 1953 (Mjma 7.4) earthquakes occurred, but the details are not well known. The 1938 off Fukushima (Shioya-oki) earthquakes were the only M>7 earthquakes recorded in the southern part of the 2011 Tohoku earthquake source. The earthquake sequence consists of 5 events as shown in Table. Abe (1977, Tectonophysics) studied these events and estimated the focal mechanisms and seismic moments. However, the slip distributions are not known. We first examined the teleseismic waveforms recorded at Pasadena, De Bilt and Christchurch. Comparison of waveforms from the five earthquakes shows that P wave and following phases from event 4 are the largest. Event 4 at CHR and event 5 at DBN show clear downward initial motions. While the above three stations are located near nodal planes on focal sphere, the comparison indicates the focal mechanism of event 4 and 5 are different each other. After the 2011 Tohoku earthquake, many aftershocks with M~6 occurred in this region with various focal mechanisms, including reverse fault, normal fault and strike-slip fault. We compared the teleseismic waveforms of these aftershocks and the 1938 earthquakes. Few of the teleseismic waveforms from the 2011 aftershocks are comparable with the 1938 events, because the aftershocks were smaller in M and waveforms from many aftershocks overlap. Off the Boso region, the southern neighbor of the 2011 Tohoku earthquake source, several large earthquakes and tsunami earthquakes (e.g., 1677 Empo earthquake) have occurred, but their recurrence is not known. Two earthquakes, one on August 18, 1927 with Mjma 6.9 and Mt 7.4, and the other on November 25 1953 with Mjma 7.4 and Mt 7.8, have different epicenters and the tsunami source areas. While the 1927 epicenter was located to southeast of the 1953 epicenter, the 1927 tsunami source was estimated to the northwest of the 1953 tsunami source (Hatori, 1975). The S-P times at 9 Japanese stations and at University of Tokyo station indicate are larger for the 1927 earthquake than that of the 1953 event, indicating that the epicenter was at far southeast of the tsunami source area.The 1938 off Fukushima earthquakes;

  10. Rock friction and its implications for earthquake prediction examined via models of Parkfield earthquakes.

    PubMed Central

    Tullis, T E

    1996-01-01

    The friction of rocks in the laboratory is a function of time, velocity of sliding, and displacement. Although the processes responsible for these dependencies are unknown, constitutive equations have been developed that do a reasonable job of describing the laboratory behavior. These constitutive laws have been used to create a model of earthquakes at Parkfield, CA, by using boundary conditions appropriate for the section of the fault that slips in magnitude 6 earthquakes every 20-30 years. The behavior of this model prior to the earthquakes is investigated to determine whether or not the model earthquakes could be predicted in the real world by using realistic instruments and instrument locations. Premonitory slip does occur in the model, but it is relatively restricted in time and space and detecting it from the surface may be difficult. The magnitude of the strain rate at the earth's surface due to this accelerating slip seems lower than the detectability limit of instruments in the presence of earth noise. Although not specifically modeled, microseismicity related to the accelerating creep and to creep events in the model should be detectable. In fact the logarithm of the moment rate on the hypocentral cell of the fault due to slip increases linearly with minus the logarithm of the time to the earthquake. This could conceivably be used to determine when the earthquake was going to occur. An unresolved question is whether this pattern of accelerating slip could be recognized from the microseismicity, given the discrete nature of seismic events. Nevertheless, the model results suggest that the most likely solution to earthquake prediction is to look for a pattern of acceleration in microseismicity and thereby identify the microearthquakes as foreshocks. Images Fig. 4 Fig. 4 Fig. 5 Fig. 7 PMID:11607668

  11. Inland Normal Faulting during the Mw 6.6 Iwaki Earthquake Induced By Temporal Change of Stress State after the Mw 9.0 2011 Tohoku Earthquake, Japan

    NASA Astrophysics Data System (ADS)

    Miyakawa, A.; Otsubo, M.

    2014-12-01

    A Mw 6.6 earthquake hit Iwaki area, northeastern Honshu arc, Japan on April 11, 2011 (here 2011 Iwaki earthquake). The 2011 Iwaki earthquake occurred one month after the 2011 Mw 9.0 earthquake off the Pacific coast of Tohoku (March 11, 2011; hereafter, 2011 Tohoku earthquake) (Ozawa et al., 2011; Simons et al., 2011). The 2011 Iwaki earthquake was followed by simultaneous slips of multi faults (the Itozawa fault and the Yunodake fault) (e.g. Toda and Tsutsumi, 2013). We examine the activity of the Itozawa fault and Yunodake fault and the mechanical preparation of the 2011 Iwaki earthquake from the temporal change of the stress state before and after the 2011 Tohoku earthquake. Furthermore, we quantitatively evaluate the role of crustal fluid beneath the faults and its supply mechanisms when the 2011 Iwaki earthquake occurred. We revealed that the generation of the slip on the Itozawa fault and simultaneous activity of faults cannot be occurred under the state of stress before the 2011 Tohoku earthquake, even though the both the state of stress is normal-faulting stress regimes before and after 2011 Tohoku earthquake. We show the importance of excess fluid pressure on the 2011 Iwaki earthquake, and we estimated the magnitude of excess fluid pressure ~30 MPa and ~20 MPa on the Itozawa and Yunodake fault respectively. We also show that the state of stress after the 2011 Tohoku earthquake favorably change the permeability of the Itozawa fault to be supplied the crustal fluid beneath the fault. A part of this research project has been conducted as the regulatory supporting research funded by the Secretariat of Nuclear Regulation Authority (Secretariat of NRA), Japan.

  12. Earthquake-induced water-level fluctuations at Yucca Mountain, Nevada, June 1992

    SciTech Connect

    O`Brien, G.M.

    1993-07-01

    This report presents earthquake-induced water-level and fluid-pressure data for wells in the Yucca Mountain area, Nevada, during June 1992. Three earthquakes occurred which caused significant water-level and fluid-pressure responses in wells. Wells USW H-5 and USW H-6 are continuously monitored to detect short-term responses caused by earthquakes. Two wells, monitored hourly, had significant, longer-term responses in water level following the earthquakes. On June 28, 1992, a 7.5-magnitude earthquake occurred near Landers, California causing an estimated maximum water-level change of 90 centimeters in well USW H-5. Three hours later a 6.6-magnitude earthquake occurred near Big Bear Lake, California; the maximum water-level fluctuation was 20 centimeters in well USW H-5. A 5.6-magnitude earthquake occurred at Little Skull Mountain, Nevada, on June 29, approximately 23 kilometers from Yucca Mountain. The maximum estimated short-term water-level fluctuation from the Little Skull Mountain earthquake was 40 centimeters in well USW H-5. The water level in well UE-25p {number_sign}1, monitored hourly, decreased approximately 50 centimeters over 3 days following the Little Skull Mountain earthquake. The water level in UE-25p {number_sign}1 returned to pre-earthquake levels in approximately 6 months. The water level in the lower interval of well USW H-3 increased 28 centimeters following the Little Skull Mountain earthquake. The Landers and Little Skull Mountain earthquakes caused responses in 17 intervals of 14 hourly monitored wells, however, most responses were small and of short duration. For several days following the major earthquakes, many smaller magnitude aftershocks occurred causing measurable responses in the continuously monitored wells.

  13. Threshold magnitude for Ionospheric TEC response to earthquakes

    NASA Astrophysics Data System (ADS)

    Perevalova, N. P.; Sankov, V. A.; Astafyeva, E. I.; Zhupityaeva, A. S.

    2014-02-01

    We have analyzed ionospheric response to earthquakes with magnitudes of 4.1-8.8 which occurred under quiet geomagnetic conditions in different regions of the world (the Baikal region, Kuril Islands, Japan, Greece, Indonesia, China, New Zealand, Salvador, and Chile). This investigation relied on measurements of total electron content (TEC) variations made by ground-based dual-frequency GPS receivers. To perform the analysis, we selected earthquakes with permanent GPS stations installed close by. Data processing has revealed that after 4.1-6.3-magnitude earthquakes wave disturbances in TEC variations are undetectable. We have thoroughly analyzed publications over the period of 1965-2013 which reported on registration of wave TIDs after earthquakes. This analysis demonstrated that the magnitude of the earthquakes having a wave response in the ionosphere was no less than 6.5. Based on our results and on the data from other researchers, we can conclude that there is a threshold magnitude (near 6.5) below which there are no pronounced earthquake-induced wave TEC disturbances. The probability of detection of post-earthquake TIDs with a magnitude close to the threshold depends strongly on geophysical conditions. In addition, reliable identification of the source of such TIDs generally requires many GPS stations in an earthquake zone. At low magnitudes, seismic energy is likely to be insufficient to generate waves in the neutral atmosphere which are able to induce TEC disturbances observable at the level of background fluctuations.

  14. Comparison of hydrological responses to the Wenchuan and Lushan earthquakes

    NASA Astrophysics Data System (ADS)

    Shi, Zheming; Wang, Guangcai; Wang, Chi-yuen; Manga, Michael; Liu, Chenglong

    2014-04-01

    On 20th April, 2013, a large earthquake (Lushan Mw 6.6) occurred in Sichuan, China, in the same fault zone as the devastating 2008 Mw 7.9 Wenchuan earthquake. The two earthquakes have similar focal mechanisms and both caused large hydrological changes in the region. The similarity of focal mechanisms, fault zone geology and the abundance of hydrological responses provide a rare opportunity for testing proposed mechanisms for hydrological responses to earthquakes. Using data from wells installed in hard rocks, we find that both the magnitude and the sign of water level changes are inconsistent with those predicted by the coseismic strain hypothesis in the near-field and in the intermediate-field. Instead, permeability change may be the dominant mechanism for the coseismic changes in water level. We also find that the minimum seismic energy required to trigger liquefaction for the Wenchuan earthquake is only 1/20 of that for the Lushan earthquake, suggesting either that the occurrence of liquefaction is more sensitive to low seismic frequencies or that the Wenchuan earthquake changed the sensitivity of unconsolidated materials, and properties had not completely recovered during the 5-year interval between the two earthquakes.

  15. The 1909 Taipei earthquake: implication for seismic hazard in Taipei

    USGS Publications Warehouse

    Kanamori, Hiroo; Lee, William H.K.; Ma, Kuo-Fong

    2012-01-01

    The 1909 April 14 Taiwan earthquake caused significant damage in Taipei. Most of the information on this earthquake available until now is from the written reports on its macro-seismic effects and from seismic station bulletins. In view of the importance of this event for assessing the shaking hazard in the present-day Taipei, we collected historical seismograms and station bulletins of this event and investigated them in conjunction with other seismological data. We compared the observed seismograms with those from recent earthquakes in similar tectonic environments to characterize the 1909 earthquake. Despite the inevitably large uncertainties associated with old data, we conclude that the 1909 Taipei earthquake is a relatively deep (50–100 km) intraplate earthquake that occurred within the subducting Philippine Sea Plate beneath Taipei with an estimated M_W of 7 ± 0.3. Some intraplate events elsewhere in the world are enriched in high-frequency energy and the resulting ground motions can be very strong. Thus, despite its relatively large depth and a moderately large magnitude, it would be prudent to review the safety of the existing structures in Taipei against large intraplate earthquakes like the 1909 Taipei earthquake.

  16. Earthquake scenarios based on lessons from the past

    NASA Astrophysics Data System (ADS)

    Solakov, Dimcho; Simeonova, Stella; Aleksandrova, Irena; Popova, Iliana

    2010-05-01

    Earthquakes are the most deadly of the natural disasters affecting the human environment; indeed catastrophic earthquakes have marked the whole human history. Global seismic hazard and vulnerability to earthquakes are increasing steadily as urbanization and development occupy more areas that are prone to effects of strong earthquakes. Additionally, the uncontrolled growth of mega cities in highly seismic areas around the world is often associated with the construction of seismically unsafe buildings and infrastructures, and undertaken with an insufficient knowledge of the regional seismicity peculiarities and seismic hazard. The assessment of seismic hazard and generation of earthquake scenarios is the first link in the prevention chain and the first step in the evaluation of the seismic risk. The implementation of the earthquake scenarios into the policies for seismic risk reduction will allow focusing on the prevention of earthquake effects rather than on intervention followin