Sample records for aleutian islands earthquake
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Modeling potential tsunami sources for deposits near Unalaska Island, Aleutian Islands
NASA Astrophysics Data System (ADS)
La Selle, S.; Gelfenbaum, G. R.
2013-12-01
In regions with little seismic data and short historical records of earthquakes, we can use preserved tsunami deposits and tsunami modeling to infer if, when and where tsunamigenic earthquakes have occurred. The Aleutian-Alaska subduction zone in the region offshore of Unalaska Island is one such region where the historical and paleo-seismicity is poorly understood. This section of the subduction zone is not thought to have ruptured historically in a large earthquake, leading some to designate the region as a seismic gap. By modeling various historical and synthetic earthquake sources, we investigate whether or not tsunamis that left deposits near Unalaska Island were generated by earthquakes rupturing through Unalaska Gap. Preliminary field investigations near the eastern end of Unalaska Island have identified paleotsunami deposits well above sea level, suggesting that multiple tsunamis in the last 5,000 years have flooded low-lying areas over 1 km inland. Other indicators of tsunami inundation, such as a breached cobble beach berm and driftwood logs stranded far inland, were tentatively attributed to the March 9, 1957 tsunami, which had reported runup of 13 to 22 meters on Umnak and Unimak Islands, to the west and east of Unalaska. In order to determine if tsunami inundation could have reached the runup markers observed on Unalaska, we modeled the 1957 tsunami using GeoCLAW, a numerical model that simulates tsunami generation, propagation, and inundation. The published rupture orientation and slip distribution for the MW 8.6, 1957 earthquake (Johnson et al., 1994) was used as the tsunami source, which delineates a 1200 km long rupture zone along the Aleutian trench from Delarof Island to Unimak Island. Model results indicate that runup and inundation from this particular source are too low to account for the runup markers observed in the field, because slip is concentrated in the western half of the rupture zone, far from Unalaska. To ascertain if any realistic
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2014-05-21
Remote, rugged and extraordinarily beautiful, Alaska’s Aleutian Islands are best known for wildlife reserves, military bases, fishing, furs and fog. The sprawling volcanic archipelago was brought into the spotlight by the Russian-supported expedition of Alexey Chirikov and Vitus Bering in 1741, and soon became controlled by the Russian-American Fur Company. In 1867 the United States purchased Alaska, including the Aleutian Islands, from Russia. By 1900 the port in Unalaska was well established as a shipping port for Alaska gold. The archipelago sweeps about 1,200 miles (1,800 km) from the tip of the Alaskan Peninsula to Attu, the most westward island. Four major island groups hold 14 large islands, about 55 smaller islands, and a large number of islets, adding up to roughly 150 islands/islets in total. This chain separates the Bering Sea (north) from the Pacific Ocean (south) and the islands are connected by the Marine Highway Ferry – at least as far as Unalaska. For the most remote islands, such as birding paradise of Attu, the western-most Aleutian Island, travel becomes trickier and relies primarily on custom charter. The Moderate Resolution Imaging Spectroradiometer (MODIS) flew over the region and captured this spectacular true-color image of the eastern Aleutian Islands on May 15, 2014. In this image, the Alaskan Peninsula protrudes from the mainland and sweeps to the southwest. The first set of islands are called the Fox Island group. Unalaska Island is part of this group and can be identified, with some imagination, as an island formed in the shape of a flying cherub, with two arms (peninsulas) outstretched towards the northeast, seemingly reaching for the round “balls” of Akutan and Akun Islands. The smallest islands in the west of the image belong to the group known as the Islands of Four Mountains. The Aleutians continue far to the west of this image. Fog surrounds the Aleutians, stretching from just off the southwestern Alaska mainland to the
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NASA Astrophysics Data System (ADS)
Butler, Rhett; Frazer, L. Neil; Templeton, William J.
2016-05-01
We use the global rate of Mw ≥ 9.0 earthquakes, and standard Bayesian procedures, to estimate the probability of such mega events in the Aleutian Islands, where they pose a significant risk to Hawaii. We find that the probability of such an earthquake along the Aleutians island arc is 6.5% to 12% over the next 50 years (50% credibility interval) and that the annualized risk to Hawai'i is about $30 M. Our method (the regionally scaled global rate method or RSGR) is to scale the global rate of Mw 9.0+ events in proportion to the fraction of global subduction (units of area per year) that takes place in the Aleutians. The RSGR method assumes that Mw 9.0+ events are a Poisson process with a rate that is both globally and regionally stationary on the time scale of centuries, and it follows the principle of Burbidge et al. (2008) who used the product of fault length and convergence rate, i.e., the area being subducted per annum, to scale the Poisson rate for the GSS to sections of the Indonesian subduction zone. Before applying RSGR to the Aleutians, we first apply it to five other regions of the global subduction system where its rate predictions can be compared with those from paleotsunami, paleoseismic, and geoarcheology data. To obtain regional rates from paleodata, we give a closed-form solution for the probability density function of the Poisson rate when event count and observation time are both uncertain.
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NASA Astrophysics Data System (ADS)
Nelson, A. R.; Briggs, R. W.; Kemp, A.; Haeussler, P. J.; Engelhart, S. E.; Dura, T.; Angster, S. J.; Bradley, L.
2012-12-01
Uncertainty in earthquake and tsunami prehistory of the Aleutian-Alaska megathrust westward of central Kodiak Island limit assessments of southern Alaska's earthquake hazard and forecasts of potentially damaging tsunamis along much of North America's west coast. Sitkinak Island, one of the Trinity Islands off the southwest tip of Kodiak Island, lies at the western end of the rupture zone of the 1964 Mw9.2 earthquake. Plafker reports that a rancher on the north coast of Sitkinak Island observed ~0.6 m of shoreline uplift immediately following the 1964 earthquake, and the island is now subsiding at about 3 mm/yr (PBO GPS). Although a high tsunami in 1788 caused the relocation of the first Russian settlement on southwestern Kodiak Island, the eastern extent of the megathrust rupture accompanying the tsunami is uncertain. Interpretation of GPS observations from the Shumagin Islands, 380 km southwest of Kodiak Island, suggests an entirely to partially creeping megathrust in that region. Here we report the first stratigraphic evidence of tsunami inundation and land-level change during prehistoric earthquakes west of central Kodiak Island. Beneath tidal and freshwater marshes around a lagoon on the south coast of Sitkinak Island, 27 cores and tidal outcrops reveal the deposits of four to six tsunamis in 2200 years and two to four abrupt changes in lithology that may correspond with coseismic uplift and subsidence over the past millennia. A 2- to 45-mm-thick bed of clean to peaty sand in sequences of tidal sediment and freshwater peat, identified in more than one-half the cores as far inland as 1.5 km, was probably deposited by the 1788 tsunami. A 14C age on Scirpus seeds, double 137Cs peaks at 2 cm and 7 cm depths (Chernobyl and 1963?), a consistent decline in 210Pb values, and our assumption of an exponential compaction rate for freshwater peat, point to a late 18th century age for the sand bed. Initial 14C ages suggest that two similar extensive sandy beds, identified
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Seismicity of the Earth 1900-2010 Aleutian arc and vicinity
Benz, Harley M.; Herman, Matthew; Tarr, Arthur C.; Hayes, Gavin P.; Furlong, Kevin P.; Villaseñor, Antonio; Dart, Richard L.; Rhea, Susan
2011-01-01
This map shows details of the Aleutian arc not visible in an earlier publication. The Aleutian arc extends about 3,000 km from the Gulf of Alaska to the Kamchatka Peninsula. It marks the region where the Pacific plate subducts into the mantle beneath the North America plate. This subduction is responsible for the generation of the Aleutian Islands and the deep offshore Aleutian Trench. Relative to a fixed North America plate, the Pacific plate is moving northwest at a rate that increases from about 55 mm per year at the arc's eastern edge to 75 mm per year near its western terminus. In the east, the convergence of the plates is nearly perpendicular to the plate boundary. However, because of the boundary's curvature, as one travels westward along the arc, the subduction becomes more and more oblique to the boundary until the relative plate motion becomes parallel to the arc at the Near Islands near its western edge. Subduction zones such as the Aleutian arc are geologically complex and produce numerous earthquakes from multiple sources. Deformation of the overriding North America plate generates shallow crustal earthquakes, whereas slip at the interface of the plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. At greater depths, Aleutian arc earthquakes occur within the subducting Pacific plate and can reach depths of 300 km. Since 1900, six great earthquakes have occurred along the Aleutian Trench, Alaska Peninsula, and Gulf of Alaska: M8.4 1906 Rat Islands; M8.6 1938 Shumagin Islands; M8.6 1946 Unimak Island; M8.6 1957 Andreanof Islands; M9.2 1964 Prince William Sound; and M8.7 1965 Rat Islands. Several relevant tectonic elements (plate boundaries and active volcanoes) provide a context for the seismicity presented on the main map panel. The plate boundaries are most accurate along the axis of the Aleutian Trench and more diffuse or speculative in extreme northeastern Russia. The active volcanoes parallel
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Billington, Serena; Engdahl, E.R.; Price, Stephanie
1981-01-01
On November 4 1977, a magnitude Ms 6.7 (mb 5.7) shallow-focus thrust earthquake occurred in the vicinity of the Adak seismographic network in the central Aleutian island arc. The earthquake and its aftershock sequence occurred in an area that had not experienced a similar sequence since at least 1964. About 13 1/2 months before the main shock, the rate of occurrence of very small magnitude earthquakes increased abruptly in the immediate vicinity of the impending main shock. To search for possible variations in the focal mechanism of small events preceding the main shock, a method was developed that objectively combines first-motion data to generate composite focal-mechanism information about events occurring within a small source region. The method could not be successfully applied to the whole study area, but the results show that starting about 10 1/2 months before the November 1977 earthquake, there was a change in the mechanism of small- to moderate-sized earthquakes in the immediate vicinity of the hypocenter and possibly in other parts of the eventual aftershock zone, but not in the surrounding regions.
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Clouds off the Aleutian Islands
2017-12-08
March 23, 2010 - Clouds off the Aleutian Islands Interesting cloud patterns were visible over the Aleutian Islands in this image, captured by the MODIS on the Aqua satellite on March 14, 2010. Turbulence, caused by the wind passing over the highest points of the islands, is producing the pronounced eddies that swirl the clouds into a pattern called a vortex "street". In this image, the clouds have also aligned in parallel rows or streets. Cloud streets form when low-level winds move between and over obstacles causing the clouds to line up into rows (much like streets) that match the direction of the winds. At the point where the clouds first form streets, they're very narrow and well-defined. But as they age, they lose their definition, and begin to spread out and rejoin each other into a larger cloud mass. The Aleutians are a chain of islands that extend from Alaska toward the Kamchatka Peninsula in Russia. For more information related to this image go to: modis.gsfc.nasa.gov/gallery/individual.php?db_date=2010-0... For more information about Goddard Space Flight Center go here: www.nasa.gov/centers/goddard/home/index.html
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Engdahl, E.R.; Billington, S.; Kisslinger, C.
1989-01-01
The Andreanof Islands earthquake (Mw 8.0) is the largest event to have occurred in that section of the Aleutian arc since the March 9, 1957, Aleutian Islands earthquake (Mw 8.6). Teleseismically well-recorded earthquakes in the region of the 1986 earthquake are relocated with a plate model and with careful attention to the focal depths. The data set is nearly complete for mb???4.7 between longitudes 172??W and 179??W for the period 1964 through April 1987 and provides a detailed description of the space-time history of moderate-size earthquakes in the region for that period. Additional insight is provided by source parameters which have been systematically determined for Mw???5 earthquakes that occurred in the region since 1977 and by a modeling study of the spatial distribution of moment release on the mainshock fault plane. -from Authors
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Perspective View of Umnak Island, Aleutian Islands, Alaska #2
2001-11-04
This image is a perspective view acquired by NASA Airborne Synthetic Aperture Radar AIRSAR in 2001, is of Umnak Island, one of Alaska Aleutian Islands. The active Okmok volcano appears in the center of the island.
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Perspective View of Umnak Island, Aleutian Islands, Alaska #1
2001-11-04
This image is a perspective view acquired by NASA Airborne Synthetic Aperture Radar AIRSAR in 2001, is of Umnak Island, one of Alaska Aleutian Islands. The active Okmok volcano appears in the center of the island.
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Ryan, Holly F.; von Huene, Roland E.; Wells, Ray E.; Scholl, David W.; Kirby, Stephen; Draut, Amy E.; Dumoulin, Julie A.; Dusel-Bacon, C.
2012-01-01
During the past several years, devastating tsunamis were generated along subduction zones in Indonesia, Chile, and most recently Japan. Both the Chile and Japan tsunamis traveled across the Pacific Ocean and caused localized damage at several coastal areas in California. The question remains as to whether coastal California, in particular the California Continental Borderland, is vulnerable to more extensive damage from a far-field tsunami sourced along a Pacific subduction zone. Assuming that the coast of California is at risk from a far-field tsunami, its coastline is most exposed to a trans-Pacific tsunami generated along the eastern Aleutian-Alaska subduction zone. We present the background geologic constraints that could control a possible giant (Mw ~9) earthquake sourced along the eastern Aleutian-Alaska megathrust. Previous great earthquakes (Mw ~8) in 1788, 1938, and 1946 ruptured single segments of the eastern Aleutian-Alaska megathrust. However, in order to generate a giant earthquake, it is necessary to rupture through multiple segments of the megathrust. Potential barriers to a throughgoing rupture, such as high-relief fracture zones or ridges, are absent on the subducting Pacific Plate between the Fox and Semidi Islands. Possible asperities (areas on the megathrust that are locked and therefore subject to infrequent but large slip) are identified by patches of high moment release observed in the historical earthquake record, geodetic studies, and the location of forearc basin gravity lows. Global Positioning System (GPS) data indicate that some areas of the eastern Aleutian-Alaska megathrust, such as that beneath Sanak Island, are weakly coupled. We suggest that although these areas will have reduced slip during a giant earthquake, they are not really large enough to form a barrier to rupture. A key aspect in defining an earthquake source for tsunami generation is determining the possibility of significant slip on the updip end of the megathrust near
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Witter, Robert C.; Briggs, Richard W.; Engelhart, Simon E.; Gelfenbaum, Guy R.; Koehler, Richard D.; Barnhart, William D.
2014-01-01
Can a predominantly creeping segment of a subduction zone generate a great (M > 8) earthquake? Despite Russian accounts of strong shaking and high tsunamis in 1788, geodetic observations above the Aleutian megathrust indicate creeping subduction across the Shumagin Islands segment, a well-known seismic gap. Seeking evidence for prehistoric great earthquakes, we investigated Simeonof Island, the archipelago's easternmost island, and found no evidence for uplifted marine terraces or subsided shorelines. Instead, we found freshwater peat blanketing lowlands, and organic-rich silt and tephra draping higher glacially smoothed bedrock. Basal peat ages place glacier retreat prior to 10.4 ka and imply slowly rising (<0.2 m/ka) relative sea level since ~3.4 ka. Storms rather than tsunamis probably deposited thin, discontinuous deposits in coastal sites. If rupture of the megathrust beneath Simeonof Island produced great earthquakes in the late Holocene, then coseismic uplift or subsidence was too small (≤0.3 m) to perturb the onshore geologic record.
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Multi-segment earthquakes and tsunami potential of the Aleutian megathrust
Shennan, I.; Bruhn, R.; Plafker, G.
2009-01-01
Large to great earthquakes and related tsunamis generated on the Aleutian megathrust produce major hazards for both the area of rupture and heavily populated coastlines around much of the Pacific Ocean. Here we use paleoseismic records preserved in coastal sediments to investigate whether segment boundaries control the largest ruptures or whether in some seismic cycles segments combine to produce earthquakes greater than any observed since instrumented records began. Virtually the entire megathrust has ruptured since AD1900, with four different segments generating earthquakes >M8.0. The largest was the M9.2 great Alaska earthquake of March 1964 that ruptured ???800 km of the eastern segment of the megathrust. The tsunami generated caused fatalities in Alaska and along the coast as far south as California. East of the 1964 zone of deformation, the Yakutat microplate experienced two >M8.0 earthquakes, separated by a week, in September 1899. For the first time, we present evidence that earthquakes ???900 and ???1500 years ago simultaneously ruptured adjacent segments of the Aleutian megathrust and the Yakutat microplate, with a combined area ???15% greater than 1964, giving an earthquake of greater magnitude and increased tsunamigenic potential. ?? 2008 Elsevier Ltd. All rights reserved.
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46 CFR 7.170 - Alaska Peninsula, AK to Aleutian Islands, AK.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 46 Shipping 1 2014-10-01 2014-10-01 false Alaska Peninsula, AK to Aleutian Islands, AK. 7.170 Section 7.170 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES APPLICABLE TO THE PUBLIC BOUNDARY LINES Alaska § 7.170 Alaska Peninsula, AK to Aleutian Islands, AK. (a) A line drawn from the...
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46 CFR 7.170 - Alaska Peninsula, AK to Aleutian Islands, AK.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 46 Shipping 1 2011-10-01 2011-10-01 false Alaska Peninsula, AK to Aleutian Islands, AK. 7.170 Section 7.170 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES APPLICABLE TO THE PUBLIC BOUNDARY LINES Alaska § 7.170 Alaska Peninsula, AK to Aleutian Islands, AK. (a) A line drawn from the...
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46 CFR 7.170 - Alaska Peninsula, AK to Aleutian Islands, AK.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 46 Shipping 1 2013-10-01 2013-10-01 false Alaska Peninsula, AK to Aleutian Islands, AK. 7.170 Section 7.170 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES APPLICABLE TO THE PUBLIC BOUNDARY LINES Alaska § 7.170 Alaska Peninsula, AK to Aleutian Islands, AK. (a) A line drawn from the...
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Cranial suture biology of the Aleutian Island inhabitants.
Cray, James; Mooney, Mark P; Siegel, Michael I
2011-04-01
Research on cranial suture biology suggests there is biological and taxonomic information to be garnered from the heritable pattern of suture synostosis. Suture synostosis along with brain growth patterns, diet, and biomechanical forces influence phenotypic variability in cranial vault morphology. This study was designed to determine the pattern of ectocranial suture synostosis in skeletal populations from the Aleutian Islands. We address the hypothesis that ectocranial suture synostosis pattern will differ according to cranial vault shape. Ales Hrdlicka identified two phenotypes in remains excavated from the Aleutian Island. The Paleo-Aleutians, exhibiting a dolichocranic phenotype with little prognathism linked to artifacts distinguished from later inhabitants, Aleutians, who exhibited a brachycranic phenotype with a greater amount of prognathism. A total of 212 crania representing Paleo-Aleuts and Aleutian as defined by Hrdlicka were investigated for suture synostosis pattern following standard methodologies. Comparisons were performed using Guttmann analyses. Results revealed similar suture fusion patterns for the Paleo-Aleut and Aleutian, a strong anterior to posterior pattern of suture fusion for the lateral-anterior suture sites, and a pattern of early termination at the sagittal suture sites for the vault. These patterns were found to differ from that reported in the literature. Because these two populations with distinct cranial shapes exhibit similar patterns of suture synostosis it appears pattern is independent of cranial shape in these populations of Homo sapiens. These findings suggest that suture fusion patterns may be population dependent and that a standardized methodology, using suture fusion to determine age-at-death, may not be applicable to all populations. Copyright © 2011 Wiley-Liss, Inc.
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Earthquake location in island arcs
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
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-07-07
.... 0910131363-0087-02] RIN 0648-XX17 Fisheries of the Exclusive Economic Zone Off Alaska; Greenland Turbot in the Aleutian Islands Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National... Islands subarea of the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary to...
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NASA Astrophysics Data System (ADS)
Ghosh, A.; LI, B.
2016-12-01
Alaska-Aleutian subduction zone is one of the most seismically active subduction zones in this planet. It is characterized by remarkable along-strike variations in seismic behavior, more than 50 active volcanoes, and presents a unique opportunity to serve as a natural laboratory to study subduction zone processes including fault dynamics. Yet details of the seismicity pattern, spatiotemporal distribution of slow earthquakes, nature of interaction between slow and fast earthquakes and their implication on the tectonic behavior remain unknown. We use a hybrid seismic network approach and install 3 mini seismic arrays and 5 stand-alone stations to simultaneously image subduction fault and nearby volcanic system (Makushin). The arrays and stations are strategically located in the Unalaska Island, where prolific tremor activity is detected and located by a solo pilot array in summer 2012. The hybrid network is operational between summer 2015 and 2016 in continuous mode. One of the three arrays starts in summer 2014 and provides additional data covering a longer time span. The pilot array in the Akutan Island recorded continuous seismic data for 2 months. An automatic beam-backprojection analysis detects almost daily tremor activity, with an average of more than an hour per day. We imaged two active sources separated by a tremor gap. The western source, right under the Unalaska Island shows the most prolific activity with a hint of steady migration. In addition, we are able to identify more than 10 families of low frequency earthquakes (LFEs) in this area. They are located within the tremor source area as imaged by the bean-backprojection technique. Application of a match filter technique reveals that intervals between LFE activities are shorter during tremor activity and longer during quiet time period. We expect to present new results from freshly obtained data. The experiment A-cubed is illuminating subduction zone processes under Unalaska Island in unprecedented
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-12
...-BC25 Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab... Amendment 42 to the Fishery Management Plan for Bering Sea/Aleutian Islands King and Tanner Crabs (FMP) for... economic zone of the Bering Sea and Aleutian Islands (BSAI) are managed under the FMP. The FMP was prepared...
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Molecular genetic status of Aleutian Canada Geese from Buldir and the Semidi Islands, Alaska
Pierson, Barbara J.; Pearce, John M.; Talbot, Sandra L.; Shields, Gerald F.; Scribner, Kim T.
2000-01-01
We conducted genetic analyses of Aleutian Canada Geese (Branta canadensis leucopareia) from Buldir Island in the western Aleutians and the Semidi Islands in the eastern portion of their breeding range. We compared data from seven microsatellite DNA loci and 143 base pairs of the control region of mitochondrial DNA from the two populations of Aleutian Canada Geese and another small-bodied subspecies, the Cackling Canada Goose (B. c. minima) which nests in western Alaska. The widely separated island-nesting Aleutian geese were genetically more closely related to each other than to mainland-nesting small-bodied geese. The populations of Aleutian geese were genetically differentiated from one another in terms of mitochondrial DNA haplotype and microsatellite allele frequencies, suggesting limited contemporary gene flow and/or major shifts in gene frequency through genetic drift. The degree of population genetic differentiation suggests that Aleutian Canada Goose populations could be considered separate management units. There was some evidence of population bottlenecks, although we found no significant genetic evidence of non-random mating or inbreeding.
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50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Bering Sea and Aleutian Islands (BSAI... PROVISIONS Specific Fishery or Program Fishing Capacity Reduction Regulations § 600.1103 Bering Sea and... Fishery Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs pursuant to § 679.2 of...
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50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Bering Sea and Aleutian Islands (BSAI... PROVISIONS Specific Fishery or Program Fishing Capacity Reduction Regulations § 600.1103 Bering Sea and... Fishery Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs pursuant to § 679.2 of...
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50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Bering Sea and Aleutian Islands (BSAI... PROVISIONS Specific Fishery or Program Fishing Capacity Reduction Regulations § 600.1103 Bering Sea and... Fishery Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs pursuant to § 679.2 of...
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50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false Bering Sea and Aleutian Islands (BSAI... PROVISIONS Specific Fishery or Program Fishing Capacity Reduction Regulations § 600.1103 Bering Sea and... Fishery Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs pursuant to § 679.2 of...
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50 CFR Figure 8 to Part 679 - Aleutian Islands Chinook Salmon Savings Area
Code of Federal Regulations, 2010 CFR
2010-10-01
... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Aleutian Islands Chinook Salmon Savings Area 8 Figure 8 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL... ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 8 Figure 8 to Part 679—Aleutian Islands Chinook Salmon Savings Area...
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50 CFR Figure 8 to Part 679 - Aleutian Islands Chinook Salmon Savings Area
Code of Federal Regulations, 2011 CFR
2011-10-01
... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Aleutian Islands Chinook Salmon Savings Area 8 Figure 8 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL... ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 8 Figure 8 to Part 679—Aleutian Islands Chinook Salmon Savings Area...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-28
.... 101126521-0640-2] RIN 0648-XA734 Fisheries of the Exclusive Economic Zone Off Alaska; ``Other Rockfish'' in the Aleutian Islands Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National... subarea of the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary because...
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Slow Earthquakes in the Alaska-Aleutian Subduction Zone Detected by Multiple Mini Seismic Arrays
NASA Astrophysics Data System (ADS)
LI, B.; Ghosh, A.; Thurber, C. H.; Lanza, F.
2017-12-01
The Alaska-Aleutian subduction zone is one of the most seismically and volcanically active plate boundaries on earth. Compared to other subduction zones, the slow earthquakes, such as tectonic tremors (TTs) and low frequency earthquakes (LFEs), are relatively poorly studied due to the limited data availability and difficult logistics. The analysis of two-months of continuous data from a mini array deployed in 2012 shows abundant tremor and LFE activities under Unalaska Island that is heterogeneously distributed [Li & Ghosh, 2017]. To better study slow earthquakes and understand their physical characteristics in the study region, we deployed a hybrid array of arrays, consisting of three well-designed mini seismic arrays and five stand alone stations, in the Unalaska Island in 2014. They were operational for between one and two years. Using the beam back-projection method [Ghosh et al., 2009, 2012], we detect continuous tremor activities for over a year when all three arrays are running. The sources of tremors are located south of the Unalaska and Akutan Islands, at the eastern and down-dip edge of the rupture zone of the 1957 Mw 8.6 earthquake, and they are clustered in several patches, with a gap between the two major clusters. Tremors show multiple migration patterns with propagation in both along-strike and dip directions and a wide range of velocities. We also identify tens of LFE families and use them as templates to search for repeating LFE events with the matched-filter method. Hundreds to thousands of LFEs for each family are detected and their activities are spatiotemporally consistent with tremor activities. The array techniques are revealing a near-continuous tremor activity in this area with remarkable spatiotemporal details. It helps us to better recognize the physical properties of the transition zone, provides new insights into the slow earthquake activities in this area, and explores their relation with the local earthquakes and the potential slow
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A new sea star of the genus Leptasterias (Asteroidea: Asteriidae) from the Aleutian Islands.
Clark, Roger N; Jewett, Stephen C
2015-04-02
A new species of asteriid sea star of the genus Leptasterias (Order Forcipulatida) is described from the nearshore waters of the Aleutian Islands. Leptaterias tatei sp. nov. is distinguished from Leptasterias stolacantha Fisher, 1930, by the characteristics of the spines and pedicellariae. Geographic distribution is discussed and a key to the five-rayed Leptasterias of the Aleutian Islands is provided.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-11-04
.... SUMMARY: NMFS issues regulations implementing Amendment 93 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP). These regulations amend the Bering Sea... Aleutian Islands Management Area; Limited Access Privilege Program AGENCY: National Marine Fisheries...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-02-01
... quota (IPQ) in the Western Aleutian Islands golden king crab fishery from the West regional delivery requirements. Federal regulations require West-designated golden king crab IFQ to be delivered to a processor... disruption to the Western Aleutian Islands golden king crab fishery, while providing for the sustained...
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Earthquakes, November-December 1977
Person, W.J.
1978-01-01
In the United States, the largest earthquake during this reporting period was a magntidue 6.6 in the Andreanof Islands, which are part of the Aleutian Islands chain, on November 4 that caused some minor damage. Northern California was struck by a magnitude 4.8 earthquake on November 22 causing moderate damage in the Willits area. This was the most damaging quake in the United States during the year. Two major earthquakes of magntidues 7.0 or above to 14 for the year.
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-21
.... 120806311-3213-01] RIN 0648-BC25 Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and... Bering Sea/Aleutian Islands King and Tanner Crabs (FMP). If approved, these regulations would revise the... of the CR Program were analyzed in the Bering Sea/Aleutian Islands Crab Fisheries Final EIS. Due to...
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Near-field survey of the 1946 Aleutian tsunami on Unimak and Sanak Islands
Okal, E.A.; Plafker, G.; Synolakis, C.E.; Borrero, J.C.
2003-01-01
The 1946 Aleutian earthquake stands out among tsunamigenic events because it generated both very high run-up near the earthquake source region and a destructive trans-Pacific tsunami. We obtained new data on the distribution of its tsunami in the near field along south-facing coasts between Unimak Pass on the west and Sanak Island on the east by measuring the height of driftwood and beach materials that were deposited by the tsunami above the extreme storm tide level. Our data indicate that (1) the highest measured run-up, which is at the Scotch Cap lighthouse, was 42 m above tide level or about 37 m above present storm tide elevation; (2) run-up along the rugged coast from Scotch Cap for 12 km northwest to Sennett Point is 12-18 m, and for 30 km east of Scotch Cap to Cape Lutke it is 24-42 m; (3) run-up along the broad lowlands bordering Unimak Bight is 10-20 m, and in-undation is locally more than 2 km; (5) run-up diminishes to 8 m or less at the southeast corner of Unimak Island; (6) no evidence was found for run-up above present storm tides (about 4-5 m above MLLW) on the Ikatan Peninsula or areas along the coast to the west; and (7) run-up above storm tide level in the Sanak Island group is restricted to southwest-facing coasts of Sanak, Long, and Clifford Islands, where it is continuous and locally up to 24 m high. Generation of the tsunami by one or more major earthquake-triggered submarine landslides near the shelf edge south of Unimak Island seems to be the only viable mechanism to account for the data on wave arrival time, run-up heights, and distribution, as well as for unconfirmed anecdotal reports of local postquake increases in water depth and diminished bottom-fisheries productivity. A preliminary hydrodynamic simulation of the local tsunami propagation and run-up using a dipolar model of a possible landslide off Davidson Bank provides an acceptable fit to the characteristics of the distribution of local run-up, with a value at 34 m at the Scotch Cap
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Nelson, Alan R.; Briggs, Richard; Dura, Tina; Engelhart, Simon E.; Gelfenbaum, Guy; Bradley, Lee-Ann; Forman, S.L.; Vane, Christopher H.; Kelley, K.A.
2015-01-01
cannot estimate source earthquake locations or magnitudes for most tsunami-deposited beds. We infer that no more than 3 of the 23 possible tsunamis beds at both sites were deposited following upper plate faulting or submarine landslides independent of megathrust earthquakes. If so, the Semidi segment of the Alaska-Aleutian megathrust near Chirikof Island probably sent high tsunamis southward every 180–270 yr for at least the past 3500 yr.
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-02-18
... due to a recent unforeseen event, no processing facility is open in the West region. This emergency... Magnuson-Stevens Fishery Conservation and Management Act, the Fishery Management Plan for Bering Sea... and Aleutian Islands (BSAI) are managed under the Fishery Management Plan for Bering Sea/Aleutian...
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Avian mortality associated with a volcanic gas seep at Kiska Island, Aleutian Islands, Alaska
Bond, Alexander L.; Evans, William C.; Jones, Ian L.
2012-01-01
We identified natural pits associated with avian mortality at the base of Kiska Volcano in the western Aleutian Islands, Alaska in 2007. Living, moribund, and dead birds were regularly found at low spots in a canyon between two lava flows during 2001–2006, but the phenomenon was attributed to natural trapping and starvation of fledgling seabirds (mostly Least Auklets, Aethia pusilla) at a colony site with >1 million birds present. However, 302 birds of eight species, including passerines, were found dead at the site during 2007–2010, suggesting additional factors were involved. Most carcasses showed no signs of injury and concentrations of dead birds had accumulated in a few distinctive low pits in the canyon. Gas samples from these locations showed elevated CO2 concentrations in late 2010. Analysis of carcasses indicated no evidence of blunt trauma or internal bleeding. Volcanic gases accumulating at these poorly ventilated sites may have caused the observed mortality, but are temporally variable. Most auklets breeding in the Aleutian Islands do so in recent lava flows that provide breeding habitat; our study documents a cost of this unusual habitat selection.
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Code of Federal Regulations, 2013 CFR
2013-10-01
... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679... Table 24 to Part 679—Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open...
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NASA Astrophysics Data System (ADS)
Brader, Martin; Shennan, Ian; Barlow, Natasha; Davies, Frank; Longley, Chris; Tunstall, Neil
2017-04-01
Recent paleoseismological studies question whether segment boundaries identified for 20th and 21st century great, >M 8, earthquakes persist through multiple earthquake cycles, or whether smaller segments with different boundaries rupture and cause significant hazards. The smaller segments may include some that are currently slipping rather than locked. The 1964 Alaska M 9.2 earthquake was the largest of five earthquakes of >M 7.9 between 1938 and 1965 along the Aleutian chain and coast of southcentral Alaska that helped define models of rupture segments along the Alaska-Aleutian megathrust. The 1964 M 9.2 earthquake ruptured ˜950 km of the megathrust, involving two main asperities focussed on Kodiak Island and Prince William Sound and crossed the Kenai segment, which is currently creeping. Paleoseismic studies of coastal sediments currently provide a long record of previous large earthquakes for the Prince William Sound segment, with widespread evidence of seven great earthquakes in the last 4000 years and more restricted evidence for three earlier ones. Shorter and more fragmentary records from the Kenai Peninsula, Yakataga and Kodiak Archipelago raise the hypothesis of different patterns of surface deformation during past great earthquakes. We present new evidence from coastal wetlands on Shuyak Island, towards the hypothesised north-eastern boundary of the Kodiak segment, to illustrate different detection limits of paleoseismic indicators and how these influence the identification of segment boundaries in late Holocene earthquakes. We compare predictions of co-seismic uplift and subsidence derived from geophysical models of earthquakes with different rupture modes. The spatial patterns of agreement and misfit between model predictions and quantitative reconstructions of co-seismic submergence and emergence suggest that no earthquake within the last 4000 years had the same rupture pattern as the 1964 M 9.2 earthquake.
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Code of Federal Regulations, 2010 CFR
2010-10-01
... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679 Wildlife and... 24 to Part 679—Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to...
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Kenney, Leah A; von Hippel, Frank A; Willacker, James J; O'Hara, Todd M
2012-11-01
The Aleutian Archipelago is an isolated arc of over 300 volcanic islands stretching 1,600 km across the interface of the Bering Sea and North Pacific Ocean. Although remote, some Aleutian Islands were heavily impacted by military activities from World War II until recently and were exposed to anthropogenic contaminants, including mercury (Hg). Mercury is also delivered to these islands via global atmospheric transport, prevailing ocean currents, and biotransport by migratory species. Mercury contamination of freshwater ecosystems is poorly understood in this region. Total Hg (THg) concentrations were measured in threespine stickleback fish (Gasterosteus aculeatus) collected from eight lakes at Adak Island, an island in the center of the archipelago with a long military history. Mean THg concentrations for fish whole-body homogenates for all lakes ranged from 0.314 to 0.560 mg/kg dry weight. Stickleback collected from seabird-associated lakes had significantly higher concentrations of THg compared to non-seabird lakes, including all military lakes. The δ(13)C stable isotope ratios of stickleback collected from seabird lakes suggest an input of marine-derived nutrients and/or marine-derived Hg. Copyright © 2012 SETAC.
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Andesites from northeastern Kanaga Island, Aleutians
NASA Astrophysics Data System (ADS)
Brophy, James G.
1990-04-01
Kanaga island is located in the central Aleutian island arc. Northeastern Kanaga is a currently active late Tertiary to Recent calc-alkaline volcanic complex. Basaltic andesite to andesite lavas record three episodes (series) of volcanic activity. Series I and Series II lavas are all andesite while Series III lavas are basaltic andesite to andesite. Four Series II andesites contain abundant quenched magmatic inclusions ranging in composition from high-MgO low-alumina basalt to low-MgO highalumina basalt. The spectrum of lava compositions is due primarily to fractional crystallization of a parental low-MgO high-alumina basalt but with variable degrees of crustal contamination and magma mixing. The earliest Series I lavas represent mixing between high-alumina basalt and silicic andesite with maximum SiO2 contents of 65 67 wt %. Later Series I and all Series II lavas are due to mixing of andesite magmas of similar composition. The maximum SiO2 content of the pre-mixed andesites magmas is estimated at 60 63 wt %. The youngest lavas (Series III) are all non-mixed and have maximum estimated SiO2 contents of 59 wt %. The earliest Series I lavas contain a significant crustal component while all later lavas do not. It is concluded that the maximum SiO2 contents of silicic magmas, the contribution of crustal material to silicic magma generation, and the role of magma mixing all decrease with time. Furthermore, silicic magmas generated by fractional crystallization at this volcanic center have a maximum SiO2 content of 63 wt %. All of these features have also been documented at the central Aleutian Cold Bay Volcanic Center (Brophy 1987). Based on data from these two centers a model of Aleutian calc-alkaline magma chamber development is proposed. The main features are: (1) a single low pressure magma chamber is continuously supplied by primitive low-alumina basalt; (2) non-primary high-alumina basalt is formed along the chamber margins by selective gravitational settling of
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Geologic framework of the Aleutian arc, Alaska
Vallier, Tracy L.; Scholl, David W.; Fisher, Michael A.; Bruns, Terry R.; Wilson, Frederic H.; von Huene, Roland E.; Stevenson, Andrew J.
1994-01-01
The Aleutian arc is the arcuate arrangement of mountain ranges and flanking submerged margins that forms the northern rim of the Pacific Basin from the Kamchatka Peninsula (Russia) eastward more than 3,000 km to Cooke Inlet (Fig. 1). It consists of two very different segments that meet near Unimak Pass: the Aleutian Ridge segment to the west and the Alaska Peninsula-the Kodiak Island segment to the east. The Aleutian Ridge segment is a massive, mostly submerged cordillera that includes both the islands and the submerged pedestal from which they protrude. The Alaska Peninsula-Kodiak Island segment is composed of the Alaska Peninsula, its adjacent islands, and their continental and insular margins. The Bering Sea margin north of the Alaska Peninsula consists mostly of a wide continental shelf, some of which is underlain by rocks correlative with those on the Alaska Peninsula.There is no pre-Eocene record in rocks of the Aleutian Ridge segment, whereas rare fragments of Paleozoic rocks and extensive outcrops of Mesozoic rocks occur on the Alaska Peninsula. Since the late Eocene, and possibly since the early Eocene, the two segments have evolved somewhat similarly. Major plutonic and volcanic episodes, however, are not synchronous. Furthermore, uplift of the Alaska Peninsula-Kodiak Island segment in late Cenozoic time was more extensive than uplift of the Aleutian Ridge segment. It is probable that tectonic regimes along the Aleutian arc varied during the Tertiary in response to such factors as the directions and rates of convergence, to bathymetry and age of the subducting Pacific Plate, and to the volume of sediment in the Aleutian Trench.The Pacific and North American lithospheric plates converge along the inner wall of the Aleutian trench at about 85 to 90 mm/yr. Convergence is nearly at right angles along the Alaska Peninsula, but because of the arcuate shape of the Aleutian Ridge relative to the location of the plates' poles of rotation, the angle of convergence
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New Near-Source Tsunami Field Data for the April 1, 1946 Aleutian Earthquake, Alaska
NASA Astrophysics Data System (ADS)
Plafker, G.; Synolakis, C. E.; Okal, E. A.
2001-12-01
The April 1, 1946 Aleutian earthquake (Ms 7.4; Mw 8.2) stands out among tsunamigenic events because it generated both very high run-up near the earthquake source region and a destructive trans-Pacific tsunami. For this puzzling event, maximum near-field run-up (42 m) is more than 6 times the computed average dip slip on the source fault (Johnson and Satake, 1997). Attempts to model the near-field tsunami have been hampered by an almost total absence of reliable data on wave run-up, direction, and arrival time because the ocean coast in the region was virtually uninhabited, the earthquake and tsunami occurred at night, and there were no nearby recording tide gauges. The lone exception is the Scotch Cap Coast Guard station on the southwestern end of Unimak Island where a reinforced concrete lighthouse and its crew of 5 Coast Guardsmen were obliterated by the tsunami. Survivors at the station, who were in a communications facility on the sea cliff above the lighthouse, report that the wave arrived shortly before low tide at 2:18 A.M., some 48 minutes after the main shock was felt. Previous surveys by Coast Guard personnel indicated a maximum wave run-up elevation of 30-35 m at the station above an unspecified datum. We obtained new data on tsunami distribution along south-facing coasts between Unimak Pass on the west and Sanak Island on the east by measuring the height of driftwood and beach materials that were deposited by the tsunami above the extreme storm tide level. Our data indicate that: 1. The highest measured run-up, which is at the Scotch Cap lighthouse, was 42 m above tide level or about 37 m above present storm tide elevation; 2. Run-up along the rugged coast from Scotch Cap for 12 km NW to Sennett Point is 12.6-18 m and for 30 km east of Scotch Cap to Cape Lutke it is 24-40.6 m; 3. Run-up along the broad lowlands bordering Unimak Bight is 10-15 m and inundation is locally more than 1,000 m; 5. Run-up diminishes to 8 m or less at the SE corner of Unimak
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The 7-8 August 2008 eruption of Kasatochi Volcano, central Aleutian Islands, Alaska
NASA Astrophysics Data System (ADS)
Waythomas, Christopher F.; Scott, William E.; Prejean, Stephanie G.; Schneider, David J.; Izbekov, Pavel; Nye, Christopher J.
2010-12-01
Kasatochi volcano in the central Aleutian Islands erupted unexpectedly on 7-8 August 2008. Kasatochi has received little study by volcanologists and has had no confirmed historical eruptions. The island is an important nesting area for seabirds and a long-term biological study site of the U.S. Fish and Wildlife Service. After a notably energetic preeruptive earthquake swarm, the volcano erupted violently in a series of explosive events beginning in the early afternoon of 7 August. Each event produced ash-gas plumes that reached 14-18 km above sea level. The volcanic plume contained large amounts of SO2 and was tracked around the globe by satellite observations. The cumulative volcanic cloud interfered with air travel across the North Pacific, causing many flight cancelations that affected thousands of travelers. Visits to the volcano in 2008-2009 indicated that the eruption generated pyroclastic flows and surges that swept all flanks of the island, accumulated several tens of meters of pyroclastic debris, and increased the diameter of the island by about 800 m. Pyroclastic flow deposits contain abundant accidental lithic debris derived from the inner walls of the Kasatochi crater. Juvenile material is crystal-rich silicic andesite that ranges from slightly pumiceous to frothy pumice. Fine-grained pyroclastic surge and fall deposits with accretionary lapilli cover the lithic-rich pyroclastic flow deposits and mark a change in eruptive style from episodic explosive activity to more continuous ash emission with smaller intermittent explosions. Pyroclastic deposits completely cover the island, but wave erosion and gully development on the flanks have begun to modify the surface mantle of volcanic deposits.
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DeGange, Anthony R.; Byrd, G. Vernon; Walker, Lawrence R.; Waythomas, C.F.
2010-01-01
The Aleutian Islands are situated on the northern edge of the so-called “Pacific Ring of Fire,” a 40,000-km-long horseshoe-shaped assemblage of continental landmasses and islands bordering the Pacific Ocean basin that contains many of the world's active and dormant volcanoes. Schaefer et al. (2009) listed 27 historically active volcanoes in the Aleutian Islands, of which nine have had at least one major eruptive event since 1990. Volcanic eruptions are often significant natural disturbances, and ecosystem responses to volcanic eruptions may vary markedly with eruption style (effusive versus explosive), frequency, and magnitude of the eruption as well as isolation of the disturbed sites from potential colonizing organisms (del Moral and Grishin, 1999). Despite the relatively high frequency of volcanic activity in the Aleutians, the response of island ecosystems to volcanic disturbances is largely unstudied because of the region's isolation. The only ecological studies in the region that address the effects of volcanic activity were done on Bogoslof Island, a remote, highly active volcanic island in the eastern Aleutians, which grew from a submarine eruption in 1796 (Merriam, 1910; Byrd et al., 1980; Byrd and Williams, 1994). Nevertheless, in the 214 years of Bogoslof's existence, the island has been visited only intermittently.Kasatochi Island is a small (2.9 km by 2.6 km, 314 m high) volcano in the central Aleutian Islands of Alaska (52.17°N latitude, 175.51°W longitude; Fig. 1) that erupted violently on 7-8 August 2008 after a brief, but intense period of precursory seismic activity (Scott et al., 2010 [this issue]; Waythomas et al., in review). The island is part of the Aleutian arc volcanic front, and is an isolated singular island. Although the immediate offshore areas are relatively shallow (20–50 m water depth), the island is about 10 km south of the 2000 m isobath, north of which, ocean depths increase markedly. Kasatochi is located between the
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InSAR imaging of volcanic deformation over cloud-prone areas - Aleutian islands
Lu, Zhong
2007-01-01
Interferometric synthetic aperture radar (INSAR) is capable of measuring ground-surface deformation with centimeter-tosubcentimeter precision and spatial resolution of tens-of meters over a relatively large region. With its global coverage and all-weather imaging capability, INSAR is an important technique for measuring ground-surface deformation of volcanoes over cloud-prone and rainy regions such as the Aleutian Islands, where only less than 5 percent of optical imagery is usable due to inclement weather conditions. The spatial distribution of surface deformation data, derived from INSAR images, enables the construction of detailed mechanical models to enhance the study of magmatic processes. This paper reviews the basics of INSAR for volcanic deformation mapping and the INSAR studies of ten Aleutian volcanoes associated with both eruptive and noneruptive activity. These studies demonstrate that all-weather INSAR imaging can improve our understanding of how the Aleutian volcanoes work and enhance our capability to predict future eruptions and associated hazards.
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Madison, Erica N.; Piatt, John F.; Arimitsu, Mayumi L.; Romano, Marc D.; van Pelt, Thomas I.; Nelson, S. Kim; Williams, Jeffrey C.; DeGange, Anthony R.
2011-01-01
The Kittlitz's Murrelet Brachyramphus brevirostris is adapted for life in glacial-marine ecosystems, being concentrated in the belt of glaciated fjords in the northern Gulf of Alaska from Glacier Bay to Cook Inlet. Most of the remaining birds are scattered along coasts of the Alaska Peninsula and Aleutian Islands, where they reside in protected bays and inlets, often in proximity to remnant glaciers or recently deglaciated landscapes. We summarize existing information on Kittlitz's Murrelet in this mainly unglaciated region, extending from Kodiak Island in the east to the Near Islands in the west. From recent surveys, we estimated that ~2400 Kittlitz's Murrelets were found in several large embayments along the Alaska Peninsula, where adjacent ice fields feed silt-laden water into the bays. On Kodiak Island, where only remnants of ice remain today, observations of Kittlitz's Murrelets at sea were uncommon. The species has been observed historically around the entire Kodiak Archipelago, however, and dozens of nest sites were found in recent years. We found Kittlitz's Murrelets at only a few islands in the Aleutian chain, notably those with long complex shorelines, high mountains and remnant glaciers. The largest population (~1600 birds) of Kittlitz's Murrelet outside the Gulf of Alaska was found at Unalaska Island, which also supports the greatest concentration of glacial ice in the Aleutian Islands. Significant populations were found at Atka (~1100 birds), Attu (~800) and Adak (~200) islands. Smaller numbers have been reported from Unimak, Umnak, Amlia, Kanaga, Tanaga, Kiska islands, and Agattu Island, where dozens of nest sites have been located in recent years. Most of those islands have not been thoroughly surveyed, and significant pockets of Kittlitz's Murrelets may yet be discovered. Our estimate of ~6000 Kittlitz's Murrelets along the Alaska Peninsula and Aleutian Islands is also likely to be conservative because of the survey protocols we employed (i.e. early
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-11-14
...NMFS proposes regulations to implement Amendment 102 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (BSAI FMP), and amend the Individual Fishing Quota Program for the Fixed-Gear Commercial Fisheries for Pacific Halibut and Sablefish in Waters in and off Alaska (IFQ Program). Amendment 102 and its proposed implementing regulations would create a Community Quota Entity (CQE) Program in halibut IFQ regulatory area 4B (Area 4B) and the sablefish Aleutian Islands regulatory area that is similar to the existing CQE Program in the Gulf of Alaska (GOA). Amendment 102 would also allow an eligible community in Area 4B and in the Aleutian Islands to establish a non-profit organization as a CQE to purchase halibut catcher vessel quota share (QS) assigned to Area 4B and sablefish QS assigned to the Aleutian Islands. The CQE could assign the resulting annual halibut and sablefish IFQ to participants according to defined CQE Program elements. An additional proposed revision to the IFQ Program regulations would allow IFQ derived from D share halibut QS to be fished on Category C vessels in Area 4B. These actions are necessary to provide additional fishing opportunities for residents of fishery dependent communities and sustain participation in the halibut and sablefish IFQ fisheries. These actions are intended to promote the goals and objectives of the Magnuson-Stevens Fishery Conservation and Management Act, the Northern Pacific Halibut Act of 1982, the BSAI FMP, and other applicable law.
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Haeussler, Peter J.; Plafker, George
1995-01-01
Earthquake risk is high in much of the southern half of Alaska, but it is not the same everywhere. This map shows the overall geologic setting in Alaska that produces earthquakes. The Pacific plate (darker blue) is sliding northwestward past southeastern Alaska and then dives beneath the North American plate (light blue, green, and brown) in southern Alaska, the Alaska Peninsula, and the Aleutian Islands. Most earthquakes are produced where these two plates come into contact and slide past each other. Major earthquakes also occur throughout much of interior Alaska as a result of collision of a piece of crust with the southern margin.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-11-03
... Aleutian Islands (AI) directed pollock fishery to the Aleut Corporation for economic development of Adak... necessary for conducting the AI directed pollock fishery. Management provisions for the AI directed pollock fishery include: restrictions on the harvest specifications for the AI directed pollock fishery...
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Vegetation of eastern Unalaska Island, Aleutian Islands, Alaska
Talbot, Stephen S.; Schofield, Wilfred B.; Talbot, Sandra L.; Daniëls, Fred J. A.
2010-01-01
Plant communities of Unalaska Island in the eastern Aleutian Islands of western Alaska, and their relationship to environmental variables, were studied using a combined Braun-Blanquet and multivariate approach. Seventy relevés represented the range of structural and compositional variation in the matrix of vegetation and landform zonation. Eleven major community types were distinguished within six physiognomic–ecological groups: I. Dry coastal meadows: Honckenya peploides beach meadow, Leymus mollis dune meadow. II. Mesic meadows: Athyrium filix-femina – Aconitum maximum meadow, Athyrium filix-femina – Calamagrostis nutkaensis meadow, Erigeron peregrinus – Thelypteris quelpaertensis meadow. III. Wet snowbed meadow: Carex nigricans snowbed meadow. IV. Heath: Linnaea borealis – Empetrum nigrum heath, Phyllodoce aleutica heath, Vaccinium uliginosum – Thamnolia vermicularis fellfield. V. Mire: Carex pluriflora – Plantago macrocarpa mire. VI. Deciduous shrub thicket: Salix barclayi – Athyrium filix-femina thicket. These were interpreted as a complex gradient primarily influenced by soil moisture, elevation, and pH. Phytogeographical and syntaxonomical analysis of the plant communities indicated that the dry coastal meadows, most of the heaths, and the mire vegetation belonged, respectively, to the widespread classes Honckenyo–Elymetea, Loiseleurio–Vaccinietea, and Scheuchzerio–Caricetea, characterized by their circumpolar and widespread species. Amphi-Beringian species were likely diagnostic of amphi-Beringian syntaxa, many of these yet to be described.
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NASA Astrophysics Data System (ADS)
Bai, Yefei; Yamazaki, Yoshiki; Cheung, Kwok Fai
2018-04-01
The latest tsunami evacuation maps of Hawaii include an extreme scenario triggered by an Mw 9.3 Aleutian earthquake with large near-trench rupture. The tectonic plate motion produces concentrated seafloor uplift toward the deepest part of the trench generating a tsunami with strong non-hydrostatic characters. A parametric study shows the skewed seafloor uplift produces a dispersive leading crest followed by a prominent trough in the form of an N-wave. The trough maintains its depth across the ocean in the absence of side lobes and dispersion. Shifting of the uplift toward the trench tends to deepen the trough, but has diminishing effects on the wave crest away from the source. While the attenuated leading crest produces relatively moderate runup on north-facing shores of the Hawaiian Islands, with matching of the N-wave and shelf resonance periods, the trough produces an impulsive drawdown followed by an energetic upswing with unprecedented runup for a far-field tsunami. A set of control computations without dispersion reaffirms that a non-hydrostatic model is essential to account for these complex wave processes from the source to the shore. This case study highlights the unique tsunami hazards posed by the Aleutians to Hawaii and the role of wave troughs in delineating the impacts for hazard assessment and engineering design.
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Measuring the size of an earthquake
Spence, W.
1977-01-01
Earthquakes occur in a broad range of sizes. A rock burst in an Idaho silver mine may involve the fracture of 1 meter of rock; the 1965 Rat island earthquake in the Aleutian arc involved a 650-kilometer lenght of Earth's crust. Earthquakes can be even smaller and even larger. if an earthquake is felt or causes perceptible surface damage, then its intesnity of shaking can be subjectively estimated. But many large earthquakes occur in oceanic area or at great focal depths. These are either simply not felt or their felt pattern does not really indicate their true size.
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NASA Astrophysics Data System (ADS)
Littell, J. S.; Poe, A.; van Pelt, T.
2015-12-01
Climate change is already affecting the Bering Sea and Aleutian Island region of Alaska. Past and present marine research across a broad spectrum of disciplines is shedding light on what sectors of the ecosystem and the human dimension will be most impacted. In a grassroots approach to extend existing research efforts, leveraging recently completed downscaled climate projections for the Bering Sea and Aleutian Islands region, we convened a team of 30 researchers-- with expertise ranging from anthropology to zooplankton to marine mammals-- to assess climate projections in the context of their expertise. This Aleutian-Bering Climate Vulnerability Assessment (ABCVA) began with researchers working in five teams to evaluate the vulnerabilities of key species and ecosystem services relative to projected changes in climate. Each team identified initial vulnerabilities for their focal species or services, and made recommendations for further research and information needs that would help managers and communities better understand the implications of the changing climate in this region. Those draft recommendations were shared during two focused, public sessions held within two hub communities for the Bering and Aleutian region: Unalaska and St. Paul. Qualitative insights about local concerns and observations relative to climate change were collected during these sessions, to be compared to the recommendations being made by the ABCVA team of researchers. Finally, we used a Structured Decision Making process to prioritize the recommendations of participating scientists, and integrate the insights shared during our community sessions. This work brought together residents, stakeholders, scientists, and natural resource managers to collaboratively identify priorities for addressing current and expected future impacts of climate change. Recommendations from this project will be incorporated into future research efforts of the Aleutian and Bering Sea Islands Landscape Conservation
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-09-28
... among harvesters, processors, and coastal communities and monitors the ``economic stability for... Collection; Comment Request; Alaska Region Bering Sea & Aleutian Islands (BSAI) Crab Economic Data Reports... CR Program's mandatory economic data collection report (EDR) used to assess the efficacy of the CR...
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Kaler, Robb S.A.; Kenney, Leah A.; Bond, Alexander L.; Eagles-Smith, Collin A.
2014-01-01
Mercury (Hg) is a toxic element distributed globally through atmospheric transport. Agattu Island, located in the western Aleutian Islands, Alaska, has no history of point-sources of Hg contamination. We provide baseline levels of total mercury (THg) concentrations in breast feathers of three birds that breed on the island. Geometric mean THg concentrations in feathers of fork-tailed storm-petrels (Oceanodroma furcata; 6703 ± 1635, ng/g fresh weight [fw]) were higher than all other species, including snowy owl (Bubo scandiacus; 2105 ± 1631, ng/g fw), a raptor with a diet composed largely of storm-petrels at Agattu Island. There were no significant differences in mean THg concentrations of breast feathers among adult Kittlitz’s murrelet (Brachyramphus brevirostris; 1658 ± 1276, ng/g fw) and chicks (1475 ± 671, ng/g fw) and snowy owls. The observed THg concentrations in fork-tailed storm-petrel feathers emphasizes the need for further study of Hg pollution in the western Aleutian Islands.
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Kaler, Robb S A; Kenney, Leah A; Bond, Alexander L; Eagles-Smith, Collin A
2014-05-15
Mercury (Hg) is a toxic element distributed globally through atmospheric transport. Agattu Island, located in the western Aleutian Islands, Alaska, has no history of point-sources of Hg contamination. We provide baseline levels of total mercury (THg) concentrations in breast feathers of three birds that breed on the island. Geometric mean THg concentrations in feathers of fork-tailed storm-petrels (Oceanodroma furcata; 6703 ± 1635, ng/g fresh weight [fw]) were higher than all other species, including snowy owl (Bubo scandiacus; 2105 ± 1631, ng/g fw), a raptor with a diet composed largely of storm-petrels at Agattu Island. There were no significant differences in mean THg concentrations of breast feathers among adult Kittlitz's murrelet (Brachyramphus brevirostris; 1658 ± 1276, ng/g fw) and chicks (1475 ± 671, ng/g fw) and snowy owls. The observed THg concentrations in fork-tailed storm-petrel feathers emphasizes the need for further study of Hg pollution in the western Aleutian Islands. Published by Elsevier Ltd.
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Ongoing Uplift Rates and Topography Across the Aleutian Forearc Region on Kodiak Island, Alaska.
NASA Astrophysics Data System (ADS)
Sauber, J. M.; Carver, G. A.
2002-12-01
The Kodiak Islands are part of a large subduction complex that comprises the eastern Aleutian forearc; the islands form the subaerial part of a broad topographic ridge that includes a Mesozoic-Cenozoic accretionary complex. To explore the relation between the ongoing subduction process, uplift rates and topographic characteristics, we have used a 30 m digital elevation map (DEM) derived from the Shuttle Radar Topography Mission (SRTM), an older 90 m DEM and ocean bathymetry. The topographic characteristics of Kodiak Island vary along strike and as a function of distance from the trench. From the northern to southern part of island, the distance from the 5800 m bathymetric contour (Aleutian Trench) and the eastern coast of Kodiak Island, as well as the width of the island, narrows by about 10% and probably reflects a steepening of the dip of the downgoing Pacific plate under the southern part of the island. The northern and central part of the island have similar topographic profiles as a function of distance from the trench; the highest peaks are located in the central part of the island. Although most of the island was glaciated during the last glacial maximum, the southwest portion of the island remained unglaciated; this region is distinctly less dissected. Preliminary uplift rates across the forearc region have been estimated from coastal marine terraces and short-term geodetic observations. Elevation changes over the last 103 - 104 years are being obtained from kinematic GPS observations across two sets of Holocene marine terrace sequences and from elevation measurements in northern Kodiak of an extensive late Pleistocene marine terrace (probably an oxygen isotope stage 5a, 120 - 130 ka). Initial measurements from the older terrace in northern Kodiak suggest an average uplift rate for the eastern side of Kodiak, above the down-dip end of the locked zone on the megathrust, to be about 1.2 mm/yr; on the western side of the island the uplift rate decreases by an
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An introduced predator alters Aleutian Island plant communities by thwarting nutrient subsidies
Maron, J.L.; Estes, J.A.; Croll, D.A.; Danner, E.M.; Elmendorf, S.C.; Buckelew, S.L.
2006-01-01
The ramifying effects of top predators on food webs traditionally have been studied within the framework of trophic cascades. Trophic cascades are compelling because they embody powerful indirect effects of predators on primary production. Although less studied, indirect effects of predators may occur via routes that are not exclusively trophic. We quantified how the introduction of foxes onto the Aleutian Islands transformed plant communities by reducing abundant seabird populations, thereby disrupting nutrient subsidies vectored by seabirds from sea to land. We compared soil and plant fertility, plant biomass and community composition, and stable isotopes of nitrogen in soil, plants, and other organisms on nine fox-infested and nine historically fox-free islands across the Aleutians. Additionally, we experimentally augmented nutrients on a fox-infested island to test whether differences in plant productivity and composition between fox-infested and fox-free islands could have arisen from differences in nutrient inputs between island types. Islands with historical fox infestations had soils low in phosphorus and nitrogen and plants low in tissue nitrogen. Soils, plants, slugs, flies, spiders, and bird droppings on these islands had low d15N values indicating that these organisms obtained nitrogen from internally derived sources. In contrast, soils, plants, and higher trophic level organisms on fox-free islands had elevated d15N signatures indicating that they utilized nutrients derived from the marine environment. Furthermore, soil phosphorus (but not nitrogen) and plant tissue nitrogen were higher on fox-free than fox-infested islands. Nutrient subsidized fox-free islands supported lush, high biomass plant communities dominated by graminoids. Fox-infested islands were less graminoid dominated and had higher cover and biomass of low-lying forbs and dwarf shrubs. While d15N profiles of soils and plants and graminoid biomass varied with island size and distance from
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Genetic structure of the Common Eider in the western Aleutian Islands prior to fox eradication
Sonsthagen, Sarah A.; Talbot, Sandra L.; Wilson, Robert E.; Petersen, Margaret R.; Williams, Jeffrey C.; Byrd, G. Vernon; McCracken, Kevin G.
2013-01-01
Since the late 18th century bird populations residing in the Aleutian Archipelago have been greatly reduced by introduced arctic foxes (Alopex lagopus). We analyzed data from microsatellite, nuclear intron, and mitochondrial (mtDNA) loci to examine the spatial genetic structure, demography, and gene flow among four Aleutian Island populations of the Common Eider (Somateria mollissima) much reduced by introduced foxes. In mtDNA, we found high levels of genetic structure within and between island groups (ΦST = 0.643), but we found no population subdivision in microsatellites or nuclear introns. Differences in genetic structure between the mitochondrial and nuclear genomes are consistent with the Common Eider's breeding and winter biology, as females are highly philopatric and males disperse. Nevertheless, significant differences between islands in the mtDNA of males and marginal significance (P =0.07) in the Z-linked locus Smo 1 suggest that males may also have some level of fidelity to island groups. Severe reduction of populations by the fox, coupled with females' high philopatry, may have left the genetic signature of a bottleneck effect, resulting in the high levels of genetic differentiation observed in mtDNA (ΦST = 0.460–0.807) between islands only 440 km apart. Reestablishment of the Common Eider following the fox's eradication was likely through recruitment from within the islands and bolstered by dispersal from neighboring islands, as suggested by the lack of genetic structure and asymmetry in gene flow between Attu and the other Near Islands.
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Large-scale deformation related to the collision of the Aleutian Arc with Kamchatka
Gesit, Eric L.; Scholl, David W.
1994-01-01
The far western Aleutian Island Arc is actively colliding with Kamchatka. Westward motion of the Aleutian Arc is brought about by the tangential relative motion of the Pacific plate transferred to major, right-lateral shear zones north and south of the arc. Early geologic mapping of Cape Kamchatka (a promontory of Kamchatka along strike with the Aleutian Arc) revealed many similarities to the geology of the Aleutian Islands. Later studies support the notion that Cape Kamchatka is the farthest west Aleutian “island” and that it has been accreted to Kamchatka by the process of arc-continent collision. Deformation associated with the collision onshore Kamchatka includes gravimetrically determined crustal thickening and formation of a narrow thrust belt of intensely deformed rocks directly west of Cape Kamchatka. The trend of the thrust faults is concave toward the collision zone, indicating a radial distribution of maximum horizontal compressive stress. Offshore, major crustal faults trend either oblique to the Kamchatka margin or parallel to major Aleutian shear zones. These offshore faults are complex, accommodating both strike-slip and thrust displacements as documented by focal mechanisms and seismic reflection data. Earthquake activity is much higher in the offshore region within a zone bounded to the north by the northernmost Aleutian shear zone and to the west by an apparent aseismic front. Analysis of focal mechanisms in the region indicate that the present-day arc-continent “contact zone” is located directly east of Cape Kamchatka. In modeling the dynamics of the collision zone using thin viscous sheet theory, the rheological parameters are only partially constrained to values of n (the effective power law exponent) ≥ 3 and Ar(the Argand number) ≤ 30. These values are consistent with a forearc thermal profile of Kamchatka, previously determined from heat flow modeling. The thin viscous sheet modeling also indicates that onshore thrust faulting
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Seitz, A.C.; Loher, Timothy; Norcross, Brenda L.; Nielsen, J.L.
2011-01-01
Currently, it is assumed that eastern Pacific halibut Hippoglossus stenolepis belong to a single, fully mixed population extending from California through the Bering Sea, in which adult halibut disperse randomly throughout their range during their lifetime. However, we hypothesize that hali but dispersal is more complex than currently assumed and is not spatially random. To test this hypo thesis, we studied the seasonal dispersal and behavior of Pacific halibut in the Bering Sea and Aleutian Islands (BSAI). Pop-up Archival Transmitting tags attached to halibut (82 to 154 cm fork length) during the summer provided no evidence that individuals moved out of the Bering Sea and Aleutian Islands region into the Gulf of Alaska during the mid-winter spawning season, supporting the concept that this region contains a separate spawning group of adult halibut. There was evidence for geographically localized groups of halibut along the Aleutian Island chain, as all of the individuals tagged there displayed residency, with their movements possibly impeded by tidal currents in the passes between islands. Mid-winter aggregation areas of halibut are assumed to be spawning grounds, of which 2 were previously unidentified and extend the species' presumed spawning range ~1000 km west and ~600 km north of the nearest documented spawning area. If there are indeed independent spawning groups of Pacific halibut in the BSAI, their dynamics may vary sufficiently from those of the Gulf of Alaska, so that specifically accounting for their relative segregation and unique dynamics within the larger population model will be necessary for correctly predicting how these components may respond to fishing pressure and changing environmental conditions.?? Inter-Research 2011.
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Aleutian terranes from Nd isotopes
NASA Technical Reports Server (NTRS)
Kay, R. W.; Kay, S. M.; Rubenstone, J. L.
1986-01-01
Nd isotope ratios substantiate the identification of oceanic crustal terranes within the continental crustal basement of the Aleutian island arc. The oceanic terranes are exposed in the westernmost Aleutians, but to the east, they are completely buried by isotopically distinct arc-volcanic rocks. Analogous oceanic terranes may be important components of the terrane collages that comprise the continents.
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Revisiting Notable Earthquakes and Seismic Patterns of the Past Decade in Alaska
NASA Astrophysics Data System (ADS)
Ruppert, N. A.; Macpherson, K. A.; Holtkamp, S. G.
2015-12-01
Alaska, the most seismically active region of the United States, has produced five earthquakes with magnitudes greater than seven since 2005. The 2007 M7.2 and 2013 M7.0 Andreanof Islands earthquakes were representative of the most common source of significant seismic activity in the region, the Alaska-Aleutian megathrust. The 2013 M7.5 Craig earthquake, a strike-slip event on the Queen-Charlotte fault, occurred along the transform plate boundary in southeast Alaska. The largest earthquake of the past decade, the 2014 M7.9 Little Sitkin event in the western Aleutians, occurred at an intermediate depth and ruptured along a gently dipping fault through nearly the entire thickness of the subducted Pacific plate. Along with these major earthquakes, the Alaska Earthquake Center reported over 250,000 seismic events in the state over the last decade, and its earthquake catalog surpassed 500,000 events in mid-2015. Improvements in monitoring networks and processing techniques allowed an unprecedented glimpse into earthquake patterns in Alaska. Some notable recent earthquake sequences include the 2008 Kasatochi eruption, the 2006-2008 M6+ crustal earthquakes in the central and western Aleutians, the 2010 and 2015 Bering Sea earthquakes, the 2014 Noatak swarm, and the 2014 Minto earthquake sequence. In 2013, the Earthscope USArray project made its way into Alaska. There are now almost 40 new Transportable Array stations in Alaska along with over 20 upgraded sites. This project is changing the earthquake-monitoring scene in Alaska, lowering magnitude of completeness across large, newly instrumented parts of the state.
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Nicolsky, D. J.; Freymueller, J.T.; Witter, R.C.; Suleimani, E. N.; Koehler, R.D.
2016-01-01
We reassess the slip distribution of the 1957 Andreanof Islands earthquake in the eastern part of the aftershock zone where published slip models infer little or no slip. Eyewitness reports, tide gauge data, and geological evidence for 9–23 m tsunami runups imply seafloor deformation offshore Unalaska Island in 1957, in contrast with previous studies that labeled the area a seismic gap. Here, we simulate tsunami dynamics for a suite of deformation models that vary in depth and amount of megathrust slip. Tsunami simulations show that a shallow (5–15 km deep) rupture with ~20 m of slip most closely reproduces the 1957 Dutch Harbor marigram and nearby >18 m runup at Sedanka Island marked by stranded drift logs. Models that place slip >20 km predict waves that arrive too soon. Our results imply that shallow slip on the megathrust in 1957 extended east into an area that presently creeps.
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Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust
Witter, Robert C.; Carver, G.A.; Briggs, Richard; Gelfenbaum, Guy R.; Koehler, R.D.; La Selle, SeanPaul M.; Bender, Adrian M.; Engelhart, S.E.; Hemphill-Haley, E.; Hill, Troy D.
2016-01-01
Current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust. Here we report geological evidence for large tsunamis, occurring on average every 300–340 years, near the source areas of the 1946 and 1957 Aleutian tsunamis. These areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate that the megathrust is currently creeping. At Sedanka Island, evidence for large tsunamis includes six sand sheets that blanket a lowland facing the Pacific Ocean, rise to 15 m above mean sea level, contain marine diatoms, cap terraces, adjoin evidence for scour, and date from the past 1700 years. The youngest sheet, and modern drift logs found as far as 800 m inland and >18 m elevation, likely record the 1957 tsunami. Modern creep on the megathrust coexists with previously unrecognized tsunami sources along this part of the Aleutian Subduction Zone.
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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.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-12-27
... information collected during 2011, such as revised stock assessments and catch data. The Plan Team compiled... and socioeconomic data, including projected biomass trends, information on assumed distribution of..., skates, sculpins, and octopuses. Section 679.20(a)(5)(iii)(B)(1) requires the Aleutian Islands (AI...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-02-19
... and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS), National... fishery in the BSAI is 1,248,494 animals as established by the final 2009 and 2010 harvest specifications.... Emily H. Menashes, Acting Director, Office of Sustainable Fisheries, National Marine Fisheries Service...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-08-17
... West region of the Aleutian Islands. An emergency exists because, due to a recent unforeseen event, no... objectives of the Magnuson-Stevens Fishery Conservation and Management Act, the Fishery Management Plan for... and Management Act (Magnuson-Stevens Act) provides authority for rulemaking to address an emergency...
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Code of Federal Regulations, 2010 CFR
2010-10-01
... endorsement for Norton Sound red king. More specifically, the reduction endorsement fisheries, and the crab... endorsement fisheries, are: (1) Bristol Bay red king (the corresponding crab rationalization fishery is Bristol Bay red king crab), (2) Bering Sea and Aleutian Islands Area C. opilio and C. bairdi (the...
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Code of Federal Regulations, 2011 CFR
2011-10-01
... endorsement for Norton Sound red king. More specifically, the reduction endorsement fisheries, and the crab... endorsement fisheries, are: (1) Bristol Bay red king (the corresponding crab rationalization fishery is Bristol Bay red king crab), (2) Bering Sea and Aleutian Islands Area C. opilio and C. bairdi (the...
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-07-27
... of a zero (0) percent fee for cost recovery under the Bering Sea and Aleutian Islands Crab... Program includes a cost recovery provision to collect fees to recover the actual costs directly related to... processing sectors to each pay half the cost recovery fees. Catcher/processor quota share holders are...
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Material culture across the Aleutian archipelago.
Hatfield, Virginia L
2010-12-01
The material evidence from sites across the Aleutian Islands reflects colonization events, subsequent adaptations, and influxes of ideas and/or people from the east. The occurrence in the eastern Aleutians of bifacial technology around 7000 BP, of artifacts similar to the Arctic Small Tool tradition between 4000 and 3500 BP, and of slate and jet objects around 1000 BP reflects repeated surges of influence or movement of peoples from further east into the eastern end of the chain. In the central and western Aleutians, influence or perhaps colonization from east of the Aleutians is also marked by the occurrence of bifacial technology about 6500 BP and the appearance of slate artifacts after 1000 BP, suggesting the movement of ideas or people from further east. Basic trends across the archipelago include a decrease in formal chipped-stone tools, an increase in the use and the complexity of bone technology, and the increase in use and variety of ground-stone tools. In addition, increasing village site sizes and denser midden deposits are seen later in time throughout the archipelago. The similarity in sites and assemblages, albeit with regional variations, reflects trends that are seen across the chain and indicates that these island communities were not isolated from one another or from mainland Alaska.
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Code of Federal Regulations, 2014 CFR
2014-10-01
... Pribilof blue king (the corresponding crab rationalization fishery is Pribilof red king and blue king crab), and (6) St. Matthew blue king (the corresponding crab rationalization fishery is also St. Matthew blue... Aleutian Islands red king, $237,588.04; (5) For Pribilof red king and Pribilof blue king, $1,571,216.35...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-07-23
... of a 2.67-percent fee for cost recovery under the Bering Sea and Aleutian Islands Crab... for the 2010/2011 crab fishing year so they can calculate the required payment for cost recovery fees...-Stevens Act). The Program includes a cost recovery provision to collect fees to recover the actual costs...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-07-21
... of a 1.23-percent fee for cost recovery under the Bering Sea and Aleutian Islands Crab... for the 2011/2012 crab fishing year so they can calculate the required payment for cost recovery fees...-Stevens Act). The Program includes a cost recovery provision to collect fees to recover the actual costs...
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-08-01
... of a 0.69-percent fee for cost recovery under the Bering Sea and Aleutian Islands Crab... for the 2013/2014 crab fishing year so they can calculate the required payment for cost recovery fees... Program includes a cost recovery provision to collect fees to recover the actual costs directly related to...
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Maley, Blaine
2016-05-01
The number of distinct human migrations into the Aleutian Islands during the Holocene has been a recurrent debate in the anthropological literature. Stemming from Hrdlička's sorting of the prehistoric remains into two distinct populations based on archaeological context and cranial measurements, the human occupation of the Aleutian Islands has long been thought to be the consequence of two distinct human migrations, a Paleo-Aleut migration that provided the initial settlement of the islands, and a Neo-Aleut migration that replaced the original settlers around 1000 BP. This study examines the relationship of the Aleut cranial assemblages in the context of greater Alaskan population variability to assess the evidence for a substantial migration into the Aleutian Islands during the late Holocene. A battery of 29 cranial measurements that quantify global cranial shape were analyzed using Euclidean morphometric methods and quantitative genetic permutation methods to examine the plausibility for two distinct Aleut occupations ("Paleo-Aleut" and "Neo-Aleut"), the latter of which is held to share closer phenetic affinities to mainland Alaskan populations than the former. The Aleut skeletal assemblages were arranged according to temporal association, geographic location, and cranial typology, and analyzed within a comparative framework of mainland Alaskan samples using principal coordinates, biological distance and random skewers permutation methods. Regardless of how the Aleut assemblages are divided, they show greater similarity to each other than to any of the mainland Alaskan assemblages. These findings are consistent across the methodological approaches. The results obtained in this study provide no support for a cranial morphology-based subdivision of the Aleuts into two distinct samples, Hence, there is no evidence for a substantial population migration of so-called Neo-Aleuts, nor for a population replacement event of an extant Paleo-Aleut population by a mainland
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-07-27
... manages the groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management.... 111213751-2102-02] RIN 0648-XC119 Fisheries of the Exclusive Economic Zone Off Alaska; Squid in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS), National...
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NASA Astrophysics Data System (ADS)
Lindquist, Kent Gordon
We constructed a near-real-time system, called Iceworm, to automate seismic data collection, processing, storage, and distribution at the Alaska Earthquake Information Center (AEIC). Phase-picking, phase association, and interprocess communication components come from Earthworm (U.S. Geological Survey). A new generic, internal format for digital data supports unified handling of data from diverse sources. A new infrastructure for applying processing algorithms to near-real-time data streams supports automated information extraction from seismic wavefields. Integration of Datascope (U. of Colorado) provides relational database management of all automated measurements, parametric information for located hypocenters, and waveform data from Iceworm. Data from 1997 yield 329 earthquakes located by both Iceworm and the AEIC. Of these, 203 have location residuals under 22 km, sufficient for hazard response. Regionalized inversions for local magnitude in Alaska yield Msb{L} calibration curves (logAsb0) that differ from the Californian Richter magnitude. The new curve is 0.2\\ Msb{L} units more attenuative than the Californian curve at 400 km for earthquakes north of the Denali fault. South of the fault, and for a region north of Cook Inlet, the difference is 0.4\\ Msb{L}. A curve for deep events differs by 0.6\\ Msb{L} at 650 km. We expand geographic coverage of Alaskan regional seismic monitoring to the Aleutians, the Bering Sea, and the entire Arctic by initiating the processing of four short-period, Alaskan seismic arrays. To show the array stations' sensitivity, we detect and locate two microearthquakes that were missed by the AEIC. An empirical study of the location sensitivity of the arrays predicts improvements over the Alaskan regional network that are shown as map-view contour plots. We verify these predictions by detecting an Msb{L} 3.2 event near Unimak Island with one array. The detection and location of four representative earthquakes illustrates the expansion
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Drew, Gary S.; Piatt, John F.; Williams, Jeffrey C.
2018-01-01
Crested Auklets (Aethia cristatella) and Least Auklets (A. pusilla) are crevice-nesting birds that breed in large mixed colonies at relatively few sites in the Aleutian Island archipelago, Bering Sea, Gulf of Alaska, and Sea of Okhotsk. Many of these colonies are located on active volcanic islands. The eruption of Kasatochi volcano, in the central Aleutians, on August 7, 2008, completely buried all crevice-nesting seabird habitat on the island. This provided an opportunity to examine the response of a large, mixed auklet colony to a major geological disturbance. Time-lapse imagery of nesting habitat indicated that both species returned to the largest pre-eruption colony site for several years, but subsequently abandoned it within 5 yr after the eruption. In 2010, a rockfall site in a cove north of the old colony site began to accumulate talus, and groups of auklets were observed using the site in 2011. Use of the new colony appeared to coincide with the abandonment of the old colony site by both species, though surface counts suggested that Least Auklets shifted to the new colony sooner than Crested Auklets. At-sea surveys of seabirds before and after the eruption indicated that both Crested and Least auklets shifted their at-sea distributions from the waters around Kasatochi Island to nearby Koniuji Island. In combination, at-sea counts and colony time-lapse imagery indicated that Crested and Least auklets using Kasatochi responded to the volcanic disturbance and complete loss of nesting habitat at the main colony on Kasatochi with dispersal either to newly created habitat on Kasatochi or to an alternate colony on a nearby island.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-07
.... 101126521-0640-02] RIN 0648-XA683 Fisheries of the Exclusive Economic Zone Off Alaska; Octopus in the Bering... retention of octopus in the Bering Sea and Aleutian Islands (BSAI). This action is necessary because the 2011 total allowable catch of octopus in the BSAI has been reached. DATES: Effective 1200 hrs, Alaska...
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Duarte, Adam; Wolcott, Daniel M.; Chow, T. Edwin
2012-01-01
The Aleutian shield fern Polystichum aleuticum is endemic to the Aleutian archipelago of Alaska and is listed as endangered pursuant to the U.S. Endangered Species Act. Despite numerous efforts to discover new populations of this species, only four known populations are documented to date, and information is needed to prioritize locations for future surveys. Therefore, we incorporated topographical habitat characteristics (elevation, slope, aspect, distance from coastline, and anthropogenic footprint) found at known Aleutian shield fern locations into a Geographical Information System (GIS) model to create a habitat suitability map for the entirety of the Andreaonof Islands. A total of 18 islands contained 489.26 km2 of highly suitable and moderately suitable habitat when weighting each factor equally. This study reports a habitat suitability map for the endangered Aleutian shield fern using topographical characteristics, which can be used to assist current and future recovery efforts for the species.
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Preliminary volcano-hazard assessment for Akutan Volcano east-central Aleutian Islands, Alaska
Waythomas, Christopher F.; Power, John A.; Richter, Donlad H.; McGimsey, Robert G.
1998-01-01
Akutan Volcano is a 1100-meter-high stratovolcano on Akutan Island in the east-central Aleutian Islands of southwestern Alaska. The volcano is located about 1238 kilometers southwest of Anchorage and about 56 kilometers east of Dutch Harbor/Unalaska. Eruptive activity has occurred at least 27 times since historical observations were recorded beginning in the late 1700?s. Recent eruptions produced only small amounts of fine volcanic ash that fell primarily on the upper flanks of the volcano. Small amounts of ash fell on the Akutan Harbor area during eruptions in 1911, 1948, 1987, and 1989. Plumes of volcanic ash are the primary hazard associated with eruptions of Akutan Volcano and are a major hazard to all aircraft using the airfield at Dutch Harbor or approaching Akutan Island. Eruptions similar to historical Akutan eruptions should be anticipated in the future. Although unlikely, eruptions larger than those of historical time could generate significant amounts of volcanic ash, fallout, pyroclastic flows, and lahars that would be hazardous to life and property on all sectors of the volcano and other parts of the island, but especially in the major valleys that head on the volcano flanks. During a large eruption an ash cloud could be produced that may be hazardous to aircraft using the airfield at Cold Bay and the airspace downwind from the volcano. In the event of a large eruption, volcanic ash fallout could be relatively thick over parts of Akutan Island and volcanic bombs could strike areas more than 10 kilometers from the volcano.
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Plafker, George
1969-01-01
The March 27, 1964, earthquake was accomp anied by crustal deformation-including warping, horizontal distortion, and faulting-over probably more than 110,000 square miles of land and sea bottom in south-central Alaska. Regional uplift and subsidence occurred mainly in two nearly parallel elongate zones, together about 600 miles long and as much as 250 miles wide, that lie along the continental margin. From the earthquake epicenter in northern Prince William Sound, the deformation extends eastward 190 miles almost to long 142° and southwestward slightly more than 400 miles to about long 155°. It extends across the two zones from the chain of active volcanoes in the Aleutian Range and Wrangell Mountains probably to the Aleutian Trench axis. Uplift that averages 6 feet over broad areas occurred mainly along the coast of the Gulf of Alaska, on the adjacent Continental Shelf, and probably on the continental slope. This uplift attained a measured maximum on land of 38 feet in a northwest-trending narrow belt less than 10 miles wide that is exposed on Montague Island in southwestern Prince William Sound. Two earthquake faults exposed on Montague Island are subsidiary northwest-dipping reverse faults along which the northwest blocks were relatively displaced a maximum of 26 feet, and both blocks were upthrown relative to sea level. From Montague Island, the faults and related belt of maximum uplift may extend southwestward on the Continental Shelf to the vicinity of the Kodiak group of islands. To the north and northwest of the zone of uplift, subsidence forms a broad asymmetrical downwarp centered over the Kodiak-Kenai-Chugach Mountains that averages 2½ feet and attains a measured maximum of 7½ feet along the southwest coast of the Kenai Peninsula. Maximum indicated uplift in the Alaska and Aleutian Ranges to the north of the zone of subsidence was l½ feet. Retriangulation over roughly 25,000 square miles of the deformed region in and around Prince William Sound
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-02-25
... and Aleutian Islands (BSAI) exclusive economic zone according to the Fishery Management Plan for.... 0810141351-9087-02] RIN 0648-XU59 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-05-03
.... 121018563-3148-02] RIN 0648-XC654 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS... Bering Sea and Aleutian Island management area (BSAI) by vessels participating in the BSAI trawl limited...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-01-25
.... 0810141351-9087-02] RIN 0648-XT97 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS... and the Bering Sea subarea of the Bering Sea and Aleutian Islands management area (BSAI) for vessels...
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2010-02-08
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Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska final report
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wright, Bruce Albert
The Aleutian Pribilof Islands Association was awarded a U.S. Department of Energy Tribal Energy Program grant (DE-EE0005624) for the Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska (Project). The goal of the Project was to perform a feasibility study to determine if a tidal energy project would be a viable means to generate electricity and heat to meet long-term fossil fuel use reduction goals, specifically to produce at least 30% of the electrical and heating needs of the tribally-owned buildings in False Pass. The Project Team included the Aleut Region organizations comprised of the Aleutianmore » Pribilof Island Association (APIA), and Aleutian Pribilof Island Community Development Association (APICDA); the University of Alaska Anchorage, ORPC Alaska a wholly-owned subsidiary of Ocean Renewable Power Company (ORPC), City of False Pass, Benthic GeoScience, and the National Renewable Energy Laboratory (NREL). The following Project objectives were completed: collected existing bathymetric, tidal, and ocean current data to develop a basic model of current circulation at False Pass, measured current velocities at two sites for a full lunar cycle to establish the viability of the current resource, collected data on transmission infrastructure, electrical loads, and electrical generation at False Pass, performed economic analysis based on current costs of energy and amount of energy anticipated from and costs associated with the tidal energy project conceptual design and scoped environmental issues. Utilizing circulation modeling, the Project Team identified two target sites with strong potential for robust tidal energy resources in Isanotski Strait and another nearer the City of False Pass. In addition, the Project Team completed a survey of the electrical infrastructure, which identified likely sites of interconnection and clarified required transmission distances from the tidal energy resources. Based on resource and
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Uplift and subsidence reveal a nonpersistent megathrust rupture boundary (Sitkinak Island, Alaska)
Briggs, Richard W.; Engelhart, Simon E.; Nelson, Alan R.; Dura, Tina; Kemp, Andrew C.; Haeussler, Peter J.; Corbett, D. Reide; Angster, Stephen J.; Bradley, Lee-Ann
2014-01-01
We report stratigraphic evidence of land-level change and tsunami inundation along the Alaska-Aleutian megathrust during prehistoric and historical earthquakes west of Kodiak Island. On Sitkinak Island, cores and tidal outcrops fringing a lagoon reveal five sharp lithologic contacts that record coseismic land-level change. Radiocarbon dates, 137Cs profiles, CT scans, and microfossil assemblages are consistent with rapid uplift ca. 290-0, 520-300, and 1050-790 cal yr BP, and subsidence in AD 1964 and ca. 640-510 cal yr BP. Radiocarbon, 137Cs, and 210Pb ages bracketing a sand bed traced 1.5 km inland and evidence for sudden uplift are consistent with Russian accounts of an earthquake and tsunami in AD 1788. The mixed uplift and subsidence record suggests that Sitkinak Island sits above a non-persistent boundary near the southwestern limit of the AD 1964 Mw 9.2 megathrust rupture.
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Tsunami hazards to U.S. coasts from giant earthquakes in Alaska
Ryan, Holly F.; von Huene, Roland E.; Scholl, Dave; Kirby, Stephen
2012-01-01
In the aftermath of Japan's devastating 11 March 2011Mw 9.0 Tohoku earthquake and tsunami, scientists are considering whether and how a similar tsunami could be generated along the Alaskan-Aleutian subduction zone (AASZ). A tsunami triggered by an earthquake along the AASZ would cross the Pacific Ocean and cause extensive damage along highly populated U.S. coasts, with ports being particularly vulnerable. For example, a tsunami in 1946 generated by a Mw 8.6 earthquake near Unimak Pass, Alaska (Figure 1a), caused significant damage along the U.S. West Coast, took 150 lives in Hawaii, and inundated shorelines of South Pacific islands and Antarctica [Fryer et al., 2004; Lopez and Okal, 2006]. The 1946 tsunami occurred before modern broadband seismometers were in place, and the mechanisms that created it remain poorly understood.
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NASA Astrophysics Data System (ADS)
Twardzik, C.; Ji, C.
2015-12-01
It has been proposed that the mechanisms for intermediate-depth and deep earthquakes might be different. While previous extensive seismological studies suggested that such potential differences do not significantly affect the scaling relationships of earthquake parameters, there has been only a few investigations regarding their dynamic characteristics, especially for fracture energy. In this work, the 2014 Mw7.9 Rat Islands intermediate-depth (105 km) earthquake and the 2015 Mw7.8 Bonin Islands deep (680 km) earthquake are studied from two different perspectives. First, their kinematic rupture models are constrained using teleseismic body waves. Our analysis reveals that the Rat Islands earthquake breaks the entire cold core of the subducting slab defined as the depth of the 650oC isotherm. The inverted stress drop is 4 MPa, compatible to that of intra-plate earthquakes at shallow depths. On the other hand, the kinematic rupture model of the Bonin Islands earthquake, which occurred in a region lacking of seismicity for the past forty years, according to the GCMT catalog, exhibits an energetic rupture within a 35 km by 30 km slip patch and a high stress drop of 24 MPa. It is of interest to note that although complex rupture patterns are allowed to match the observations, the inverted slip distributions of these two earthquakes are simple enough to be approximated as the summation of a few circular/elliptical slip patches. Thus, we investigate subsequently their dynamic rupture models. We use a simple modelling approach in which we assume that the dynamic rupture propagation obeys a slip-weakening friction law, and we describe the distribution of stress and friction on the fault as a set of elliptical patches. We will constrain the three dynamic parameters that are yield stress, background stress prior to the rupture and slip weakening distance, as well as the shape of the elliptical patches directly from teleseismic body waves observations. The study would help us
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Environmental contaminants in bald eagle eggs from the Aleutian archipelago
Anthony, R.G.; Miles, A.K.; Ricca, M.A.; Estes, J.A.
2007-01-01
We collected 136 fresh and unhatched eggs from bald eagle (Haliaeetus leucocephalus) nests and assessed productivity on eight islands in the Aleutian archipelago, 2000 to 2002. Egg contents were analyzed for a broad spectrum of organochlorine (OC) contaminants, mercury (Hg), and stable isotopes of carbon (??13C) and nitrogen (??15N). Concentrations of polychlorinated biphenyls (??PCBs), p,p???- dichlorodiphenyldichloroethylene (DDE), and Hg in bald eagle eggs were elevated throughout the archipelago, but the patterns of distribution differed among the various contaminants. Total PCBs were highest in areas of past military activities on Adak and Amchitka Islands, indicating local point sources of these compounds. Concentrations of DDE and Hg were higher on Amchitka Island, which was subjected to much military activity during World War II and the middle of the 20th century. Concentrations of ??PCBs also were elevated on islands with little history of military activity (e.g., Amlia, Tanaga, Buldir), suggesting non-point sources of PCBs in addition to point sources. Concentrations of DDE and Hg were highest in eagle eggs from the most western Aleutian Islands (e.g., Buldir, Kiska) and decreased eastward along the Aleutian chain. This east-to-west increase suggested a Eurasian source of contamination, possibly through global transport and atmospheric distillation and/or from migratory seabirds. Eggshell thickness and productivity of bald eagles were normal and indicative of healthy populations because concentrations of most contaminants were below threshold levels for effects on reproduction. Contrary to our predictions, contaminant concentrations were not correlated with stable isotopes of carbon (??13C) or nitrogen (??15N) in eggs. These latter findings indicate that contaminant concentrations were influenced more by point sources and geographic location than trophic status of eagles among the different islands. ?? 2007 SETAC.
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Jessica Larsen,; Neal, Christina; Schaefer, Janet R.; Kaufman, Max; Lu, Zhong
2015-01-01
Okmok volcano, Aleutian Islands, Alaska, explosively erupted over a five-week period between July 12 and August 23, 2008. The eruption was predominantly phreatomagmatic, producing fine-grained tephra that covered most of northeastern Umnak Island. The eruption had a maximum Volcanic Explosivity Index (VEI) of 4, with eruption column heights up to 16 km during the opening phase. Several craters and a master tuff cone formed in the caldera as a result of phreatomagmatic explosions and accumulated tephra-fall and surge deposits. Ascending magma continuously interacted with an extensive shallow groundwater table in the caldera, resulting in the phreatomagmatic character of the eruption. Syneruptive explosion and collapse processes enlarged a pre-existing lake, created a second, entirely new lake, and formed new, deep craters. A field of ephemeral collapse pits and collapse escarpments formed where rapid groundwater withdrawal removed material from beneath capping lava flows. This was the first significant phreatomagmatic event in the U.S. since the Ukinrek Maars eruption in 1977.
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Gabbroic and Peridotitic Enclaves from the 2008 Kasatochi Eruption, Aleutian Islands, Alaska
NASA Astrophysics Data System (ADS)
Kentner, A.; Nadin, E. S.; Izbekov, P. E.; Nye, C. J.; Neill, O. K.
2012-12-01
Kasatochi volcano of the Andreanof Islands in the western Aleutian Arc violently erupted over a two day period from August 7-8, 2008. The eruption involved multiple explosive events generating pyroclastic flows, which included abundant mafic and ultramafic enclaves that have since weathered out and accumulated in talus along the coast. These and other mafic enclaves sampled by modern island arc lavas provide insight into subduction magmatism because they emerge from a section of the subduction system that is less likely than shallower zones to be modified by magmatic processes such as mixing, assimilation, or fractionation. We present new whole rock, clinopyroxene, amphibole, plagioclase, and melt compositions from Kasatochi enclaves of the 2008 eruption. The highly crystalline (~40 vol. % phenocryst content), medium-K basaltic andesite host rock contains ~52-55 wt. % SiO2 and 0.6-0.9 wt. % K2O, and is composed of plagioclase, ortho- and clinopyroxene, amphibole, and Ti-magnetite in a microlite-rich groundmass. Upon eruption, this magma sampled two distinct enclave populations: gabbro and peridotite. The gabbro has abundant amphibole (mostly magnesio-hastingsite) and plagioclase with minor clinopyroxene, olivine, and magnetite, while the peridotite is composed of olivine with minor amounts of clinopyroxene and orthopyroxene. There is little textural variation amongst the peridotitic samples collected, but the gabbroic samples vary from layered to massive and cover a range in grain size from fine-grained to pegmatitic. The layered gabbros display centimeter-scale bands of alternating plagioclase- and amphibole-rich layers, with a strong preferential alignment of the amphibole grains. The coarser-grained samples are very friable, with ~10% pore space; disaggregation of these upon host-magma ascent likely formed the amphibole and plagioclase xenocrysts in the andesitic host. Based on the textural and compositional differences, we divide the enclaves into four groups
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Code of Federal Regulations, 2014 CFR
2014-10-01
... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679... to Nonpelagic Trawl Fishing ER19FE08.009 ER19FE08.010 ER19FE08.011 ER19FE08.012 ER19FE08.013 ER19FE08...
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Code of Federal Regulations, 2012 CFR
2012-10-01
... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679... to Nonpelagic Trawl Fishing ER19FE08.009 ER19FE08.010 ER19FE08.011 ER19FE08.012 ER19FE08.013 ER19FE08...
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Code of Federal Regulations, 2011 CFR
2011-10-01
... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679... to Nonpelagic Trawl Fishing ER19FE08.009 ER19FE08.010 ER19FE08.011 ER19FE08.012 ER19FE08.013 ER19FE08...
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Ryan, Holly F.; Draut, Amy E.; Keranen, Katie M.; Scholl, David W.
2012-01-01
During Pliocene to Quaternary time, the central Aleutian forearc basin evolved in response to a combination of tectonic and climatic factors. Initially, along-trench transport of sediment and accretion of a frontal prism created the accommodation space to allow forearc basin deposition. Transport of sufficient sediment to overtop the bathymetrically high Amlia fracture zone and reach the central Aleutian arc began with glaciation of continental Alaska in the Pliocene. As the obliquely subducting Amlia fracture zone swept along the central Aleutian arc, it further affected the structural evolution of the forearc basins. The subduction of the Amlia fracture zone resulted in basin inversion and loss of accommodation space east of the migrating fracture zone. Conversely, west of Amlia fracture zone, accommodation space increased arcward of a large outer-arc high that formed, in part, by a thickening of arc basement. This difference in deformation is interpreted to be the result of a variation in interplate coupling across the Amlia fracture zone that was facilitated by increasing subduction obliquity, a change in orientation of the subducting Amlia fracture zone, and late Quaternary intensification of glaciation. The change in coupling is manifested by a possible tear in the subducting slab along the Amlia fracture zone. Differences in coupling across the Amlia fracture zone have important implications for the location of maximum slip during future great earthquakes. In addition, shaking during a great earthquake could trigger large mass failures of the summit platform, as evidenced by the presence of thick mass transport deposits of primarily Quaternary age that are found in the forearc basin west of the Amlia fracture zone.
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Massive edifice failure at Aleutian arc volcanoes
Coombs, M.L.; White, S.M.; Scholl, D. W.
2007-01-01
Along the 450-km-long stretch of the Aleutian volcanic arc from Great Sitkin to Kiska Islands, edifice failure and submarine debris-avalanche deposition have occurred at seven of ten Quaternary volcanic centers. Reconnaissance geologic studies have identified subaerial evidence for large-scale prehistoric collapse events at five of the centers (Great Sitkin, Kanaga, Tanaga, Gareloi, and Segula). Side-scan sonar data collected in the 1980s by GLORIA surveys reveal a hummocky seafloor fabric north of several islands, notably Great Sitkin, Kanaga, Bobrof, Gareloi, Segula, and Kiska, suggestive of landslide debris. Simrad EM300 multibeam sonar data, acquired in 2005, show that these areas consist of discrete large blocks strewn across the seafloor, supporting the landslide interpretation from the GLORIA data. A debris-avalanche deposit north of Kiska Island (177.6?? E, 52.1?? N) was fully mapped by EM300 multibeam revealing a hummocky surface that extends 40??km from the north flank of the volcano and covers an area of ??? 380??km2. A 24-channel seismic reflection profile across the longitudinal axis of the deposit reveals a several hundred-meter-thick chaotic unit that appears to have incised into well-bedded sediment, with only a few tens of meters of surface relief. Edifice failures include thin-skinned, narrow, Stromboli-style collapse as well as Bezymianny-style collapse accompanied by an explosive eruption, but many of the events appear to have been deep-seated, removing much of an edifice and depositing huge amounts of debris on the sea floor. Based on the absence of large pyroclastic sheets on the islands, this latter type of collapse was not accompanied by large eruptions, and may have been driven by gravity failure instead of magmatic injection. Young volcanoes in the central and western portions of the arc (177?? E to 175?? W) are located atop the northern edge of the ??? 4000-m-high Aleutian ridge. The position of the Quaternary stratocones relative to the
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Stewart, Nathan L.; Konar, Brenda; Tinker, M. Tim
2015-01-01
Sea otters (Enhydra lutris) inhabiting the Aleutian Islands have stabilized at low abundance levels following a decline and currently exhibit restricted habitat-utilization patterns. Possible explanations for restricted habitat use by sea otters can be classified into two fundamentally different processes, bottom-up and top-down forcing. Bottom-up hypotheses argue that changes in the availability or nutritional quality of prey resources have led to the selective use of habitats that support the highest quality prey. In contrast, top-down hypotheses argue that increases in predation pressure from killer whales have led to the selective use of habitats that provide the most effective refuge from killer whale predation. A third hypothesis suggests that current restricted habitat use is based on a need for protection from storms. We tested all three hypotheses for restricted habitat use by comparing currently used and historically used sea otter foraging locations for: (1) prey availability and quality, (2) structural habitat complexity, and (3) exposure to prevailing storms. Our findings suggest that current use is based on physical habitat complexity and not on prey availability, prey quality, or protection from storms, providing further evidence for killer whale predation as a cause for restricted sea otter habitat use in the Aleutian Islands.
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Stewart, Nathan L; Konar, Brenda; Tinker, M Tim
2015-03-01
Sea otters (Enhydra lutris) inhabiting the Aleutian Islands have stabilized at low abundance levels following a decline and currently exhibit restricted habitat-utilization patterns. Possible explanations for restricted habitat use by sea otters can be classified into two fundamentally different processes, bottom-up and top-down forcing. Bottom-up hypotheses argue that changes in the availability or nutritional quality of prey resources have led to the selective use of habitats that support the highest quality prey. In contrast, top-down hypotheses argue that increases in predation pressure from killer whales have led to the selective use of habitats that provide the most effective refuge from killer whale predation. A third hypothesis suggests that current restricted habitat use is based on a need for protection from storms. We tested all three hypotheses for restricted habitat use by comparing currently used and historically used sea otter foraging locations for: (1) prey availability and quality, (2) structural habitat complexity, and (3) exposure to prevailing storms. Our findings suggest that current use is based on physical habitat complexity and not on prey availability, prey quality, or protection from storms, providing further evidence for killer whale predation as a cause for restricted sea otter habitat use in the Aleutian Islands.
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The 1964 Great Alaska Earthquake and tsunamis: a modern perspective and enduring legacies
Brocher, Thomas M.; Filson, John R.; Fuis, Gary S.; Haeussler, Peter J.; Holzer, Thomas L.; Plafker, George; Blair, J. Luke
2014-01-01
The magnitude 9.2 Great Alaska Earthquake that struck south-central Alaska at 5:36 p.m. on Friday, March 27, 1964, is the largest recorded earthquake in U.S. history and the second-largest earthquake recorded with modern instruments. The earthquake was felt throughout most of mainland Alaska, as far west as Dutch Harbor in the Aleutian Islands some 480 miles away, and at Seattle, Washington, more than 1,200 miles to the southeast of the fault rupture, where the Space Needle swayed perceptibly. The earthquake caused rivers, lakes, and other waterways to slosh as far away as the coasts of Texas and Louisiana. Water-level recorders in 47 states—the entire Nation except for Connecticut, Delaware, and Rhode Island— registered the earthquake. It was so large that it caused the entire Earth to ring like a bell: vibrations that were among the first of their kind ever recorded by modern instruments. The Great Alaska Earthquake spawned thousands of lesser aftershocks and hundreds of damaging landslides, submarine slumps, and other ground failures. Alaska’s largest city, Anchorage, located west of the fault rupture, sustained heavy property damage. Tsunamis produced by the earthquake resulted in deaths and damage as far away as Oregon and California. Altogether the earthquake and subsequent tsunamis caused 129 fatalities and an estimated $2.3 billion in property losses (in 2013 dollars). Most of the population of Alaska and its major transportation routes, ports, and infrastructure lie near the eastern segment of the Aleutian Trench that ruptured in the 1964 earthquake. Although the Great Alaska Earthquake was tragic because of the loss of life and property, it provided a wealth of data about subductionzone earthquakes and the hazards they pose. The leap in scientific understanding that followed the 1964 earthquake has led to major breakthroughs in earth science research worldwide over the past half century. This fact sheet commemorates Great Alaska Earthquake and
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Savage, James C.; Plafker, George; Svarc, Jerry L.; Lisowski, Michael
2014-01-01
Middleton Island, located at the seaward edge of the continental shelf 50 km from the base of the inner wall of the Aleutian Trench, affords an opportunity to make land-based measurements of uplift near the toe of the Prince William Sound megathrust, site of the 1964, M = 9.2, Alaska earthquake. Leveling surveys (1973–1993) on Middleton Island indicate roughly uniform tilting (~1 µrad/a down to the northwest) of the island, and GPS surveys (1993–2012) show an uplift rate of 14 mm/a of the island relative to fixed North America. The data are consistent with a combined (coseismic and postseismic) uplift (in meters) due to the 1964 earthquake as a function of time τ (years after the earthquake) u(τ) = (3.5 + 1.21 log10 [1 + 1.67 τ]) H(τ) where 3.5 is the coseismic uplift and H(τ) is 0 for τ < 0 and 1 otherwise. The current uplift on Middleton Island is attributed to continuous slip on a fault splaying off from the megathrust, and the long-term uplift is the superposition of the effects of past earthquakes, each earthquake being similar to the 1964 event. Then, the predicted uplift at time t due to a sequence of earthquakes at times tiwould be . From studies of strandlines associated with the uplifted terraces on Middleton Island, Plafker et al. (1992) estimated the occurrence times of the last six earthquakes and measured the present-day elevations of those strandlines. The predicted uplift is in rough agreement with those measurements. About half of the predicted uplift is due to postseismic relaxation from previous earthquakes.
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NASA Astrophysics Data System (ADS)
Savage, J. C.; Plafker, G.; Svarc, J. L.; Lisowski, M.
2014-07-01
Middleton Island, located at the seaward edge of the continental shelf 50 km from the base of the inner wall of the Aleutian Trench, affords an opportunity to make land-based measurements of uplift near the toe of the Prince William Sound megathrust, site of the 1964, M = 9.2, Alaska earthquake. Leveling surveys (1973-1993) on Middleton Island indicate roughly uniform tilting ( 1 µrad/a down to the northwest) of the island, and GPS surveys (1993-2012) show an uplift rate of 14 mm/a of the island relative to fixed North America. The data are consistent with a combined (coseismic and postseismic) uplift (in meters) due to the 1964 earthquake as a function of time τ (years after the earthquake) u(τ) = (3.5 + 1.21 log10 [1 + 1.67 τ]) H(τ) where 3.5 is the coseismic uplift and H(τ) is 0 for τ < 0 and 1 otherwise. The current uplift on Middleton Island is attributed to continuous slip on a fault splaying off from the megathrust, and the long-term uplift is the superposition of the effects of past earthquakes, each earthquake being similar to the 1964 event. Then, the predicted uplift at time t due to a sequence of earthquakes at times ti would be
∑i ut-ti -
Tectonic setting of the Wooded Island earthquake swarm, eastern Washington
Blakely, Richard J.; Sherrod, Brian L.; Weaver, Craig S.; Rohay, Alan C.; Wells, Ray E.
2012-01-01
Magnetic anomalies provide insights into the tectonic implications of a swarm of ~1500 shallow (~1 km deep) earthquakes that occurred in 2009 on the Hanford site,Washington. Epicenters were concentrated in a 2 km2 area nearWooded Island in the Columbia River. The largest earthquake (M 3.0) had first motions consistent with slip on a northwest-striking reverse fault. The swarm was accompanied by 35 mm of vertical surface deformation, seen in satellite interferometry (InSAR), interpreted to be caused by ~50 mm of slip on a northwest-striking reverse fault and associated bedding-plane fault in the underlying Columbia River Basalt Group (CRBG). A magnetic anomaly over exposed CRBG at Yakima Ridge 40 km northwest of Wooded Island extends southeastward beyond the ridge to the Columbia River, suggesting that the Yakima Ridge anticline and its associated thrust fault extend southeastward in the subsurface. In map view, the concealed anticline passes through the earthquake swarm and lies parallel to reverse faults determined from first motions and InSAR data. A forward model of the magnetic anomaly near Wooded Island is consistent with uplift of concealed CRBG, with the top surface <200 m below the surface. The earthquake swarm and the thrust and bedding-plane faults modeled from interferometry all fall within the northeastern limb of the faulted anticline. Although fluids may be responsible for triggering the Wooded Island earthquake swarm, the seismic and aseismic deformation are consistent with regional-scale tectonic compression across the concealed Yakima Ridge anticline.
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Seismogenic Fault Geometry of 2010 Mw 7.1 Solomon Islands Earthquake
NASA Astrophysics Data System (ADS)
Kuo, Y.; Ku, C.; Taylor, F. W.; Huang, B.; Chen, Y.; Chao, W.; Huang, H.; Kuo, Y.; Wu, Y.; Suppe, J.
2010-12-01
The Solomon Islands is located in southwestern Pacific, where the Indo-Australian Plate is subducting northeastward beneath the Pacific Plate. Due to subduction of rugged seafloor topography, including seamounts, the seismic activity and tectonic behavior may be complicated. Seismicity in this region was anomalously low until 2007 when a megathrust rupture (Mw 8.1) occurred. More recently, on 3 January 2010, a Mw7.1 earthquake occurred beneath the extreme outer forearc next to the trench. It came with one foreshock (Mw 6.6, 50 minutes ahead) and two large aftershocks (Mw 6.8 and 6.0) greater than magnitude 6 within a week. It is interesting to note that these four focal mechanisms are very much similar and appear to have occurred along the interplate thrust zone between the Indo-Australian plate and Solomon Islands forearc. This Earthquake nucleated approximately 50 km to the southeast of the M8.1 Earthquake occurring in April of 2007, which is located to the other side of Rendova Island. Because a tsunami followed the 2010 earthquake, it is likely that submarine surface deformation accompanied the event. By the results of D-InSAR on ALOS and ERS, plus limited points of ground displacement from GPS and strong motion seismometers, the continuous ground displacement field is constructed and normalized. Our preliminary result shows the ground movement in the Rendova Island can reach tens of centimeters, implying shallow earthquake source consistent with the suggestion by triggering tsunami. Besides, the earthquake sequence retrieved from our local seismometer observation network allows us to further define underground fault geometry. The spatial distribution of the epicenter also concludes the seamount located in the middle divides two seismogenic asperities which generate 2007 and 2010 earthquakes respectively.
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Aleutian Pribilof Islands Wind Energy Feasibility Study
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bruce A. Wright
2012-03-27
Under this project, the Aleutian Pribilof Islands Association (APIA) conducted wind feasibility studies for Adak, False Pass, Nikolski, Sand Point and St. George. The DOE funds were also be used to continue APIA's role as project coordinator, to expand the communication network quality between all participants and with other wind interest groups in the state and to provide continued education and training opportunities for regional participants. This DOE project began 09/01/2005. We completed the economic and technical feasibility studies for Adak. These were funded by the Alaska Energy Authority. Both wind and hydro appear to be viable renewable energy optionsmore » for Adak. In False Pass the wind resource is generally good but the site has high turbulence. This would require special care with turbine selection and operations. False Pass may be more suitable for a tidal project. APIA is funded to complete a False Pass tidal feasibility study in 2012. Nikolski has superb potential for wind power development with Class 7 wind power density, moderate wind shear, bi-directional winds and low turbulence. APIA secured nearly $1M from the United States Department of Agriculture Rural Utilities Service Assistance to Rural Communities with Extremely High Energy Costs to install a 65kW wind turbine. The measured average power density and wind speed at Sand Point measured at 20m (66ft), are 424 W/m2 and 6.7 m/s (14.9 mph) respectively. Two 500kW Vestas turbines were installed and when fully integrated in 2012 are expected to provide a cost effective and clean source of electricity, reduce overall diesel fuel consumption estimated at 130,000 gallons/year and decrease air emissions associated with the consumption of diesel fuel. St. George Island has a Class 7 wind resource, which is superior for wind power development. The current strategy, led by Alaska Energy Authority, is to upgrade the St. George electrical distribution system and power plant. Avian studies in Nikolski
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Coombs, Michelle L.; Larsen, Jessica F.; Neal, Christina A.
2018-02-14
Semisopochnoi Island, located in the Rat Islands group of the western Aleutian Islands and Aleutian volcanic arc, is a roughly circular island composed of scattered volcanic vents, the prominent caldera of Semisopochnoi volcano, and older, ancestral volcanic rocks. The oldest rocks on the island are gently radially dipping lavas that are the remnants of a shield volcano and of Ragged Top, which is an eroded stratocone southeast of the current caldera. None of these oldest rocks have been dated, but they all are likely Pleistocene in age. Anvil Peak, to the caldera’s north, has the morphology of a young stratocone and is latest Pleistocene to early Holocene in age. The oldest recognized Holocene deposits are those of the caldera-forming eruption, which produced the 7- by 6-km caldera in the center of the island, left nonwelded ignimbrite in valleys below the edifice, and left welded ignimbrite high on its flanks. The caldera-forming eruption produced rocks showing a range of intermediate whole-rock compositions throughout the eruption sequence, although a majority of clasts analyzed form a fairly tight cluster on SiO2-variation diagrams at 62.9 to 63.4 weight percent SiO2. This clustering of compositions at about 63 weight percent SiO2 includes black, dense, obsidian-like clasts, as well as tan, variably oxidized, highly inflated pumice clasts. The best estimate for the timing of the eruption is from a soil dated at 6,920±60 14C years before present underlying a thin facies of the ignimbrite deposit on the island’s north coast. Shortly after the caldera-forming eruption, two scoria cones on the northwest flank of the volcano outside the caldera, Ringworm crater and Threequarter Cone, simultaneously erupted small volumes of andesite.The oldest intracaldera lavas, on the floor of the caldera, are andesitic to dacitic, but are mostly covered by younger lavas and tephras. These intracaldera lavas include the basaltic andesites of small Windy cone, as well as the
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Surface wind characteristics of some Aleutian Islands. [for selection of windpowered machine sites
NASA Technical Reports Server (NTRS)
Wentink, T., Jr.
1973-01-01
The wind power potential of Alaska is assessed in order to determine promising windpower sites for construction of wind machines and for shipment of wind derived energy. Analyses of near surface wind data from promising Aleutian sites accessible by ocean transport indicate probable velocity regimes and also present deficiencies in available data. It is shown that winds for some degree of power generation are available 77 percent of the time in the Aleutians with peak velocities depending on location.
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Insights on the 1990 Bohol Tsunamigenic Earthquake, Bohol Island, Philippines
NASA Astrophysics Data System (ADS)
Besana, G. M.; Daligdig, J. A.; Abigania, M. T.; Talisic, J. E.; Evangelista, N.
2004-12-01
The February 8, 1990 earthquake at Bohol area is one of the few strong earthquakes that have affected central Philippines since the early 1900's. This M6.0 1990 Bohol event nonetheless wrought havoc to at least 16 municipalities, caused numerous casualties, injured about three hundred people, rendered several thousand homeless and evacuated from the coastal areas, and damaged at least P154 million worth of properties. The epicenter of this earthquake was initially placed onshore at 17km east of Tagbilaran City and was attributed to the movement along the Alicia Thrust Fault- a fault trending northeast-southwest. Noticeably, there was no surface rupture and the succeeding aftershocks clustered along a northeast-southwest trend off the eastern shore of Bohol island. In addition, the southeastern part of Bohol island experienced tsunami inundation particularly the municipalities of Jagna, Duero, Guindulman, Garcia Hernandez, and Valencia. In this study, several issues were resolved regarding this seismic event. First, the 1990 Bohol earthquake was generated along an offshore thrust fault based on the reviews of seismicity data from the NEIC. -Post-determined plots of the mainshock and aftershocks indicate offshore event with focal mechanism solutions that imply thrust fault activity. Intensity data likewise indicates that intense ground shaking was mainly felt in the southeastern part of the island. Second, recent field investigations undertaken clearly indicated a widespread tsunami inundation wherein the southeastern shorelines of Bohol likewise experienced a regional retreat in sea level several minutes after the strong ground shaking. Lastly, such tsunamigenic structure could somehow explain the anomalously large waves that impacted Camiguin island, an island more than 50km southeast of Bohol. A reconstruction of true tsunami heights and runup distances was also undertaken based from eyewitness accounts. Future works would involve relocation of aftershocks and
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-02-28
... economic zone according to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian.... 0910131363-0087-02] RIN 0648-XA252 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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von Huene, Roland E.; Miller, John J.; Weinrebe, Wilhelm
2012-01-01
Three destructive earthquakes along the Alaska subduction zone sourced transoceanic tsunamis during the past 70 years. Since it is reasoned that past rupture areas might again source tsunamis in the future, we studied potential asperities and barriers in the subduction zone by examining Quaternary Gulf of Alaska plate history, geophysical data, and morphology. We relate the aftershock areas to subducting lower plate relief and dissimilar materials in the seismogenic zone in the 1964 Kodiak and adjacent 1938 Semidi Islands earthquake segments. In the 1946 Unimak earthquake segment, the exposed lower plate seafloor lacks major relief that might organize great earthquake rupture. However, the upper plate contains a deep transverse-trending basin and basement ridges associated with the Eocene continental Alaska convergent margin transition to the Aleutian island arc. These upper plate features are sufficiently large to have affected rupture propagation. In addition, massive slope failure in the Unimak area may explain the local 42-m-high 1946 tsunami runup. Although Quaternary geologic and tectonic processes included accretion to form a frontal prism, the study of seismic images, samples, and continental slope physiography shows a previous history of tectonic erosion. Implied asperities and barriers in the seismogenic zone could organize future great earthquake rupture.
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Sea birds as proxies of marine habitats and food webs in the western Aleutian Arc
Springer, Alan M.; Piatt, John F.; Van Vliet, Gus B.
1996-01-01
We propose that ocean conditions of the Near Islands in the western Aleutian Arc mimic those of the shallow continental shelf of the eastern Bering Sea to the extent that the marine community, including assemblages of forage fishes and their avian predators, has distinctly coastal characteristics. In contrast, marine avifauna and their prey at neighbouring Buldir Island are distinctly oceanic. For example, at the Near Islands, the ratio of thick-billed to common murres, Vria lomvia and U. aalge, is low and black-legged kittiwakes, Rissa tridactyla, but not red-legged kittiwakes, R. brevirostris, nest there. Diets of murres and kittiwakes are dominated by sand lance, Ammodytes hexapterus, an abundant coastal species. At Buldir Island, thick-billed murres greatly outnumber common murres, red-legged kittiwakes and black-legged kittiwakes are both abundant, and diets of the birds consist primarily of oceanic squid and lantern-fish (Myctophidae). This mesoscale difference in food webs is apparently a consequence of the local physiography. A broad escarpment on the Near physiographic block creates a comparatively expansive, shallow, shelflike habitat around the Near Islands, where a pelagic community typical of coastal regions flourishes. Buldir Island is the only emergent feature of the Buldir physiographic block, with little shallow water surrounding it and, apparently, little opportunity for other than oceanic species to exist. Patterns in the distribution of fishes, and thus of sea birds, throughout the Aleutian Islands might be largely explained by the presence or absence of shelf-like habitat and the relationship between physical environments and food webs. In the larger context of fisheries oceanography, this model for the Aleutian Islands improves our ability to interpret physical and biological heterogeneity in the ocean and its relationship to regional community dynamics and trends in the abundance and productivity of individual species at higher trophic levels.
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Kirby, Stephen; Scholl, David; von Huene, Roland E.; Wells, Ray
2013-01-01
Tsunami modeling has shown that tsunami sources located along the Alaska Peninsula segment of the Aleutian-Alaska subduction zone have the greatest impacts on southern California shorelines by raising the highest tsunami waves for a given source seismic moment. The most probable sector for a Mw ~ 9 source within this subduction segment is between Kodiak Island and the Shumagin Islands in what we call the Semidi subduction sector; these bounds represent the southwestern limit of the 1964 Mw 9.2 Alaska earthquake rupture and the northeastern edge of the Shumagin sector that recent Global Positioning System (GPS) observations indicate is currently creeping. Geological and geophysical features in the Semidi sector that are thought to be relevant to the potential for large magnitude, long-rupture-runout interplate thrust earthquakes are remarkably similar to those in northeastern Japan, where the destructive Mw 9.1 tsunamigenic earthquake of 11 March 2011 occurred. In this report we propose and justify the selection of a tsunami source seaward of the Alaska Peninsula for use in the Tsunami Scenario that is part of the U.S. Geological Survey (USGS) Science Application for Risk Reduction (SAFRR) Project. This tsunami source should have the potential to raise damaging tsunami waves on the California coast, especially at the ports of Los Angeles and Long Beach. Accordingly, we have summarized and abstracted slip distribution from the source literature on the 2011 event, the best characterized for any subduction earthquake, and applied this synoptic slip distribution to the similar megathrust geometry of the Semidi sector. The resulting slip model has an average slip of 18.6 m and a moment magnitude of Mw = 9.1. The 2011 Tohoku earthquake was not anticipated, despite Japan having the best seismic and geodetic networks in the world and the best historical record in the world over the past 1,500 years. What was lacking was adequate paleogeologic data on prehistoric earthquakes
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Searching for a paleotsunami record in the Hawaiian Islands
NASA Astrophysics Data System (ADS)
La Selle, S.; Richmond, B. M.; Arcos, M. E. M.; Jaffe, B. E.; Lunghino, B.; Kane, H. H.; Bishop, J. M.; Habel, S. L.
2016-12-01
Historical records of tsunamis over the last 200 years in the state of Hawai'i demonstrate that earthquakes in subduction zones around the Pacific (Aleutian, Kuril-Kamchatka, Chile, Japan, and Alaska) can cause significant tsunami inundation on multiple Hawaiian islands. Deposits found along these subduction zones provide evidence for older tsunamis, but it is unclear if any of these prehistoric far-field events have impacted the Hawaiian islands because no study has successfully correlated Hawaiian paleotsunami deposits between sites or islands. We cored coastal marshlands on Óahu, Maui, and Kauái searching for tsunami deposits in order to determine the viability of extending the record of tsunami inundation in the state of Hawai'i. Sites were selected based on historical tsunami runup, numerical inundation modeling results, the presence of a coastal marsh in close proximity to a sandy shoreline, the extent of undisturbed wetlands, and the breadth of prior geological investigations. Several possible tsunami deposits were identified on the north and northeast shores of Kauái and Óahu as marine sand layers within marsh peat or mud. At some sites, the presence of deposits from the 1946 and 1957 Aleutian tsunamis aided identification of the deeper candidate tsunami deposits. Radiocarbon ages of the deeper sand layers suggest deposition around 800-600 cal yr B.P., which may coincide with a tsunami deposit in the eastern Aleutians that was deposited 660-560 cal yr B.P. (Witter et al., 2016). Further dating and analyses of the deposits is needed to determine whether or not deposition was synchronous on O'ahu and Kaua'i and to determine from sedimentological and micropaleontological characteristics that a tsunami formed the deposits.
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Pacific Basin tsunami hazards associated with mass flows in the Aleutian arc of Alaska
Waythomas, Christopher F.; Watts, Philip; Shi, Fengyan; Kirby, James T.
2009-01-01
We analyze mass-flow tsunami generation for selected areas within the Aleutian arc of Alaska using results from numerical simulation of hypothetical but plausible mass-flow sources such as submarine landslides and volcanic debris avalanches. The Aleutian arc consists of a chain of volcanic mountains, volcanic islands, and submarine canyons, surrounded by a low-relief continental shelf above about 1000–2000 m water depth. Parts of the arc are fragmented into a series of fault-bounded blocks, tens to hundreds of kilometers in length, and separated from one another by distinctive fault-controlled canyons that are roughly normal to the arc axis. The canyons are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes. The volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large-scale sector collapse into the sea. Large scale mass-flow deposits have not been mapped on the seafloor south of the Aleutian Islands, in part because most of the area has never been examined at the resolution required to identify such features, and in part because of the complex nature of erosional and depositional processes. Extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the Aleutian Islands. Because the Aleutian arc is surrounded by deep, open ocean, mass flows of unconsolidated debris that originate either as submarine landslides or as volcanic debris avalanches entering the sea may be potential tsunami sources. To test this hypothesis we present a series of numerical simulations of submarine mass-flow initiated tsunamis from eight different source areas. We consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides on the trench slope. The flows have lengths
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Coccidia of Aleutian Canada geese
Greiner, E.C.; Forrester, Donald J.; Carpenter, J.W.; Yparraguirre, D.R.
1981-01-01
Fecal samples from 122 captive and 130 free-ranging Aleutian Canada geese (Branta canadensis leucopareia) were examined for oocysts of coccidia. Freeranging geese sampled on the spring staging ground near Crescent City, California were infected with Eimeria hermani, E. truncata, E. magnalabia, E. fulva, E. clarkei and Tyzzeria parvula. Except for E. clarkei, the same species of coccidia were found in geese on their breeding grounds in Alaska. Most of the coccidial infections in captive geese from Amchitka Island, Alaska and Patuxent Wildlife Research Center, Maryland, consisted of Tyzzeria.
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Hair methylmercury levels of mummies of the Aleutian Islands, Alaska
DOE Office of Scientific and Technical Information (OSTI.GOV)
Egeland, G.M.; Ponce, Rafael; Bloom, Nicolas S.
2009-04-15
Ancient human hair specimens can shed light on the extent of pre-historic exposures to methylmercury and provide valuable comparison data with current-day exposures, particularly for Indigenous Peoples who continue to rely upon local traditional food resources. Human hair from ancient Aleutian Island Native remains were tested for total and methylmercury (Hg, MeHg) and were radiocarbon dated. The remains were approximately 500 years old (1450 A.D.). For four adults, the mean and median total hair mercury concentration was 5.8 ppm (SD=0.9). In contrast, MeHg concentrations were lower with a mean of 1.2 ppm (SD=1.8) and a median of 0.54 ppm (0.12-3.86).more » For the five infants, the mean and median MeHg level was 1.2 ppm (SD=1.8) and 0.20 ppm (0.007-4.61), respectively. Segmental analyses showed variations in MeHg concentrations in 1-cm segments, consistent with fluctuations in naturally occurring exposure to mercury through dietary sources. The levels are comparable to or lower than those found in fish and marine mammal-eating populations today who rely far less on subsistence food than pre-historic humans. The findings are, therefore, compatible with increased anthropogenic release of trace metals during the past several centuries.« less
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Tsunami Field Survey for the Solomon Islands Earthquake of April 1, 2007
NASA Astrophysics Data System (ADS)
Nishimura, Y.; Tanioka, Y.; Nakamura, Y.; Tsuji, Y.; Namegaya, Y.; Murata, M.; Woodward, S.
2007-12-01
Two weeks after the 2007 off-Solomon earthquake, an international tsunami survey team (ITST) of Japanese and US researchers performed a post tsunami survey in Ghizo and adjacent islands. Main purpose of the team was to provide information on the earthquake and tsunami to the national disaster council of the Solomon Islands, who was responsible for the disaster management at that time. The ITST had interview with the affected people and conducted reconnaissance mapping of the tsunami heights and flow directions. Tsunami flow heights at beach and inland were evaluated from watermarks on buildings and the position of broken branches and stuck materials on trees. These tsunami heights along the southern to western coasts of Ghizo Island were ca. 5m (a.s.l.). Tsunami run-up was traced by distribution of floating debris that carried up by the tsunami and deposited at their inundation limit. The maximum run-up was measured at Tapurai of Simbo Island to be ca. 9 m. Most of the inundation area was covered by 0-10 cm thick tsunami deposit that consists of beach sand, coral peaces and eroded soil. Coseismic uplift and subsidence were clearly identified by changes of the sea level before and after the earthquake, that were inferred by eyewitness accounts and evidences such as dried up coral reeves. These deformation patterns, as well as the tsunami height distribution, could constrain the earthquake fault geometry and motion. It is worthy of mention that the tsunami damage in villages in Ranongga Island has significantly reduced by 2-3 m uplift before the tsunami attack.
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Seismicity associated with the Sumatra-Andaman Islands earthquake of 26 December 2004
Dewey, J.W.; Choy, G.; Presgrave, B.; Sipkin, S.; Tarr, A.C.; Benz, H.; Earle, P.; Wald, D.
2007-01-01
The U.S. Geological Survey/National Earthquake Information Center (USGS/ NEIC) had computed origins for 5000 earthquakes in the Sumatra-Andaman Islands region in the first 36 weeks after the Sumatra-Andaman Islands mainshock of 26 December 2004. The cataloging of earthquakes of mb (USGS) 5.1 and larger is essentially complete for the time period except for the first half-day following the 26 December mainshock, a period of about two hours following the Nias earthquake of 28 March 2005, and occasionally during the Andaman Sea swarm of 26-30 January 2005. Moderate and larger (mb ???5.5) aftershocks are absent from most of the deep interplate thrust faults of the segments of the Sumatra-Andaman Islands subduction zone on which the 26 December mainshock occurred, which probably reflects nearly complete release of elastic strain on the seismogenic interplate-thrust during the mainshock. An exceptional thrust-fault source offshore of Banda Aceh may represent a segment of the interplate thrust that was bypassed during the mainshock. The 26 December mainshock triggered a high level of aftershock activity near the axis of the Sunda trench and the leading edge of the overthrust Burma plate. Much near-trench activity is intraplate activity within the subducting plate, but some shallow-focus, near-trench, reverse-fault earthquakes may represent an unusual seismogenic release of interplate compressional stress near the tip of the overriding plate. The interplate-thrust Nias earthquake of 28 March 2005, in contrast to the 26 December aftershock sequence, was followed by many interplate-thrust aftershocks along the length of its inferred rupture zone.
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Paleoseismicity and neotectonics of the Aleutian Subduction Zone—An overview
NASA Astrophysics Data System (ADS)
Carver, Gary; Plafker, George
The Aleutian subduction zone is one of the most seismically active plate boundaries and the source of several of the world's largest historic earthquakes. The structural architecture of the subduction zone varies considerably along its length. At the eastern end is a tectonically complex collision zone where the allochthonous Yakutat terrane is moving northwest into mainland Alaska. West of the collision zone a shallow-dipping subducted plate beneath a wide forearc, nearly orthogonal convergence, and a continental-type subduction regime characterizes the eastern part of the subduction zone. In the central part of the subduction zone, convergence becomes increasingly right oblique and the forearc is divided into a series of large clockwise-rotated fault-bounded blocks. Highly oblique convergence and island arc tectonics characterize the western part of the subduction zone. At the extreme western end of the arc, the relative plate motion is nearly pure strike-slip. A series of great subduction earthquakes ruptured most of the 4000-km length of the subduction zone during a period of several decades in the mid 1900s. The majority of these earthquakes broke multiple segments as defined by the large-scale structure of the overriding plate margin and patterns of historic seismicity. Several of these earthquakes generated Pacific-wide tsunamis and significant damage in the southwestern and south-central regions of Alaska. Characterization of previous subduction earthquakes is important in assessing future seismic and tsunami hazards. However, at present such information is available only for the eastern part of the subduction zone. The 1964 Alaska earthquake (M 9.2) ruptured about ˜950 km of the plate boundary that encompassed the Kodiak and Prince William Sound (PWS) segments. Within this region, nine paleosubduction earthquakes in the past ˜5000 years are recognized on the basis of geologic evidence of sudden land level change and, at some sites, coeval tsunami
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Aleutian Arc Magmatism: Continuous or Episodic?
NASA Astrophysics Data System (ADS)
Stone, D. B.; Layer, P. W.
2004-05-01
For essentially all of Cenozoic time, the plates of the north Pacific - the Pacific, Kula and Faralon plates - have had a generally northward motion. Most models show that rates of subduction perpendicular to the Alaska Peninsula and eastern Aleutian arc were substantial, and do not show any interruptions in expected rates and directions. In contrast, the eastern Aleutian arc (the arc bounded on both sides by oceanic depths) and to some extent the Alaska Peninsula (the parts of the arc built on continental material) appear to have significant gaps in the geologic record of volcanism. In addition to these arc-wide, generally long period gaps in volcanism, individual volcanic centers also appear to have significant temporal gaps (of shorter duration) in their eruptive histories. The most obvious example is the lack of volcanic rocks associated with today's volcanoes that are older than 2 Ma. Paleomagnetic data from Aleutian volcanoes show only one reversal, which would suggest that the bulk of the volcanic rocks were erupted during the Bruhnes normal polarity chron (roughly 700 ka to the present). The earth's field in Cenozoic time spends equal time in each polarity with an average polarity interval of about .25Ma. If eruptive activity was spread uniformly over time, more reversals would be expected. On longer timescales, available radiometric ages for volcanic and plutonic rocks from the eastern Aleutian islands divide roughly into four groups; 0-2Ma, rocks associated with the modern volcanic chain; 5-6Ma, flows, dikes and other intrusives not associated with modern volcanoes; 10-17Ma, mainly small intrusive bodies; 30-40(?)Ma, mainly isolated flow units, dikes and other intrusive rocks. This leaves gaps in the record of igneous rocks ranging from about 3Ma to 15Ma. An analogous but more complex distribution of ages is seen on the Alaska Peninsula where the arc has been built on continental crust. If the chronology and geologic history of the arc is more
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Crustal Deformation and the Seismic Cycle Across the Kodiak Islands, Alaska
NASA Technical Reports Server (NTRS)
Sauber, Jeanne; Carver, Gary; Cohen, Steven; King, Robert
2005-01-01
The Kodiak Islands are located approximately 120 to 250 km from the Alaska-Aleutian Trench - and are within the southern extent of the 1964 Prince William Sound (M(sub w) = 9.2) earthquake rupture zone. Here we report new campaign GPS results (1993-2001) from northern Kodiak Island. The rate and orientation of the horizontal velocities, relative to a fixed North America, range from 25.3 plus or minus 1.4 mm/yr at N32.9 deg. W plus or minus 2.5 to 8.5 plus or minus 1.0 mm/yr at N59.7 deg. W plus or minus 6.5 deg. In addition to the northern Kodiak data, we analyzed data from three southern Kodiak Island stations. The inland stations from both the northern and southern networks indicate a counterclockwise rotation of the velocity vectors. These results are consistent with the hypothesis that the difference between the Pacific-North American plate motion and the orientation of the down going slab would lead to 4-8 mm/yr of left-lateral slip above the unlocked, down-dip portion of the main thrust zone. The northern and southern Kodiak geodetic data are consistent with a model that includes the viscoelastic response to (1) a downgoing Pacific plate interface that is locked at shallow depths, (2) local coseismic slip in the 1964 earthquake, and (3) interseismic creep down dip from the seismogenic zone. Based on the pre-1964 and post-1944 earthquake history, as well as the pattern of interseismic earthquakes across the plate boundary zone, we hypothesize that in southern Kodiak some strain is released in moderate to large earthquakes between the occurrences of great earthquakes like the 1964 event.
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Earthquake Births New Island off Pakistan
2017-12-08
On September 24, 2013, a major strike-slip earthquake rattled western Pakistan, killing at least 350 people and leaving more than 100,000 homeless. The 7.7 magnitude quake struck the Baluchistan province of northwestern Pakistan. Amidst the destruction, a new island was created offshore in the Paddi Zirr (West Bay) near Gwadar, Pakistan. On September 26, 2013, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured the top image of that new island, which sits roughly one kilometer (0.6 miles) offshore. Likely a “mud volcano,” the island rose from the seafloor near Gwadar on September 24, shortly after the earthquake struck about 380 kilometers (230 miles) inland. The lower image, acquired by the Operational Land Imager on the Landsat 8 satellite, shows the same area on April 17, 2013. In the satellite images, lighter shades of green and tan in the water reveal shallow seafloor or suspended sediment. The water depth around the new island is roughly 15 to 20 meters (50 to 65 feet), according to marine geologist Asif Inam of Pakistan’s National Institute of Oceanography. “The floor in that area is generally flat, but the gradient in this area changes quite abruptly,” Inam said. The top image from ALI is also clear enough to show the parallel ripples of waves marching toward the shore. Read more: earthobservatory.nasa.gov/IOTD/view.php?id=82146 NASA Earth Observatory image by Jesse Allen and Robert Simmon, using EO-1 ALI data from the NASA EO-1 team. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
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Volcanoes of the Alaska Peninsula and Aleutian Islands, Alaska: selected photographs
Neal, Christina A.; McGimsey, Robert G.
2002-01-01
This CD-ROM contains 97 digital images of volcanoes along the Aleutian volcanic arc in Alaska. Perspectives include distant aerial shots, ground views of volcanic products and processes, and dramatic views of eruptions in progress. Each image is stored as a .PCD file in five resolutions. Brief captions, a location map, and glossary are included.
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Miles, A. Keith; Ricca, Mark A.; Anthony, Robert G.; Estes, James A.
2009-01-01
Organochlorines were examined in liver and stable isotopes in muscle of fishes from the western Aleutian Islands, Alaska, in relation to islands or locations affected by military occupation. Pacific cod (Gadus macrocephalus), Pacific halibut (Hippoglossus stenolepis), and rock greenling (Hexagrammos lagocephalus) were collected from nearshore waters at contemporary (decommissioned) and historical (World War II) military locations, as well as at reference locations. Total (Σ) polychlorinated biphenyls (PCBs) dominated the suite of organochlorine groups (ΣDDTs, Σchlordane cyclodienes, Σother cyclodienes, and Σchlorinated benzenes and cyclohexanes) detected in fishes at all locations, followed by ΣDDTs and Σchlordanes; dichlorodiphenyldi-chloroethylene (p,p′DDE) composed 52 to 66% of ΣDDTs by species. Organochlorine concentrations were higher or similar in cod compared to halibut and lowest in greenling; they were among the highest for fishes in Arctic or near Arctic waters. Organochlorine group concentrations varied among species and locations, but ΣPCB concentrations in all species were consistently higher at military locations than at reference locations. Moreover, all organochlorine group concentrations were higher in halibut from military locations than those from reference locations. A wide range of molecular weight organochlorines was detected at all locations, which implied regional or long-range transport and deposition, as well as local point-source contamination. Furthermore, a preponderance of higher-chlorinated PCB congeners in fishes from contemporary military islands implied recent exposure. Concentrations in all organochlorine groups increased with δ15N enrichment in fishes, and analyses of residual variation provided further evidence of different sources of ΣPCBs and p,p′DDE among species and locations.
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Barkan, Roy; ten Brink, Uri S.
2010-01-01
The 18 November 1867 Virgin Island earthquake and the tsunami that closely followed caused considerable loss of life and damage in several places in the northeast Caribbean region. The earthquake was likely a manifestation of the complex tectonic deformation of the Anegada Passage, which cuts across the Antilles island arc between the Virgin Islands and the Lesser Antilles. In this article, we attempt to characterize the 1867 earthquake with respect to fault orientation, rake, dip, fault dimensions, and first tsunami wave propagating phase, using tsunami simulations that employ high-resolution multibeam bathymetry. In addition, we present new geophysical and geological observations from the region of the suggested earthquake source. Results of our tsunami simulations based on relative amplitude comparison limit the earthquake source to be along the northern wall of the Virgin Islands basin, as suggested by Reid and Taber (1920), or on the carbonate platform north of the basin, and not in the Virgin Islands basin, as commonly assumed. The numerical simulations suggest the 1867 fault was striking 120°–135° and had a mixed normal and left-lateral motion. First propagating wave phase analysis suggests a fault striking 300°–315° is also possible. The best-fitting rupture length was found to be relatively small (50 km), probably indicating the earthquake had a moment magnitude of ∼7.2. Detailed multibeam echo sounder surveys of the Anegada Passage bathymetry between St. Croix and St. Thomas reveal a scarp, which cuts the northern wall of the Virgin Islands basin. High-resolution seismic profiles further indicate it to be a reasonable fault candidate. However, the fault orientation and the orientation of other subparallel faults in the area are more compatible with right-lateral motion. For the other possible source region, no clear disruption in the bathymetry or seismic profiles was found on the carbonate platform north of the basin.
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Burger, Joanna; Gochfeld, Michael; Kosson, David S; Powers, Charles W; Friedlander, Barry; Eichelberger, John; Barnes, David; Duffy, Lawrence K; Jewett, Stephen C; Volz, Conrad D
2005-05-01
With the ending of the Cold War, the US Department of Energy is responsible for the remediation of radioactive waste and disposal of land no longer needed for nuclear material production or related national security missions. The task of characterizing the hazards and risks from radionuclides is necessary for assuring the protection of health of humans and the environment. This is a particularly daunting task for those sites that had underground testing of nuclear weapons, where the radioactive contamination is currently inaccessible. Herein we report on the development of a Science Plan to characterize the physical and biological marine environment around Amchitka Island in the Aleutian chain of Alaska, where three underground nuclear tests were conducted (1965-1971). Information on the ecology, geology, and current radionuclide levels in biota, water, and sediment is necessary for evaluating possible current contamination and to serve as a baseline for developing a plan to ensure human and ecosystem health in perpetuity. Other information required includes identifying the location of the salt water/fresh water interface where migration to the ocean might occur in the future and determining groundwater recharge balances, as well as assessing other physical/geological features of Amchitka near the test sites. The Science Plan is needed to address the confusing and conflicting information available to the public about radionuclide risks from underground nuclear blasts in the late 1960s and early 1970s, as well as the potential for volcanic or seismic activity to disrupt shot cavities or accelerate migration of radionuclides into the sea. Developing a Science Plan involved agreement among regulators and other stakeholders, assignment of the task to the Consortium for Risk Evaluation with Stakeholder Participation, and development of a consensus Science Plan that dealt with contentious scientific issues. Involvement of the regulators (State of Alaska), resource
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Volcanic Tsunami Generation in the Aleutian Arc of Alaska
NASA Astrophysics Data System (ADS)
Waythomas, C. F.; Watts, P.
2003-12-01
, geological evidence of tsunamis, such as tsunami deposits on land, should be found in the area around Augustine Island. Paradoxically, unequivocal evidence for tsunami inundation has been found. Augustine Volcano is the most historically active volcano in the Cook Inlet region and a future tsunami from the volcano would have devastating consequences to villages, towns, oil-production facilities, and the fishing industry, especially if it occurred at high tide (the tidal range in this area is about 5 m). Numerical simulation experiments of tsunami generation, propagation and inundation using a subaerial debris avalanche source at Augustine volcano indicate only modest wave generation because of the shallow water surrounding the volcano (maximum water depth about 25 m). Lahar flows produced during eruptions at snow and ice clad volcanoes in the Aleutian arc also deliver copious amounts of sediment to the sea. These flows only rarely transform to subaqueous debris flows that may become tsunamigenic. However, the accumulation of loose, unconsolidated sediment on the continental shelf may lead to subaqueous debris flows and landslides if these deposits become mobilized by large earthquakes. Tsunamis produced by this mechanism could potentially reach coastlines all along the Pacific Rim. Finally, recent work in the western Aleutian Islands indicates that many of the island volcanoes in this area have experienced large-scale flank collapse. Because these volcanoes are surrounded by deep water, the tsunami hazard associated with a future sector collapse could be significant.
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Kelsey, Harvey M.; Witter, Robert C.; Engelhart, Simon E.; Briggs, Richard; Nelson, Alan R.; Haeussler, Peter J.; Corbett, D. Reide
2015-01-01
The Kenai section of the eastern Alaska-Aleutian subduction zone straddles two areas of high slip in the 1964 great Alaska earthquake and is the least studied of the three megathrust segments (Kodiak, Kenai, Prince William Sound) that ruptured in 1964. Investigation of two coastal sites in the eastern part of the Kenai segment, on the southeast coast of the Kenai Peninsula, identified evidence for two subduction zone earthquakes that predate the 1964 earthquake. Both coastal sites provide paleoseismic data through inferred coseismic subsidence of wetlands and associated subsidence-induced erosion of beach ridges. At Verdant Cove, paleo-beach ridges record the paleoseismic history; whereas at Quicksand Cove, buried soils in drowned coastal wetlands are the primary indicators of paleoearthquake occurrence and age. The timing of submergence and death of trees mark the oldest earthquake at Verdant Cove that is consistent with the age of a well documented ∼900-year-ago subduction zone earthquake that ruptured the Prince William Sound segment of the megathrust to the east and the Kodiak segment to the west. Soils buried within the last 400–450 years mark the penultimate earthquake on the southeast coast of the Kenai Peninsula. The penultimate earthquake probably occurred before AD 1840 from its absence in Russian historical accounts. The penultimate subduction zone earthquake on the Kenai segment did not rupture in conjunction with the Prince William Sound to the northeast. Therefore the Kenai segment, which is presently creeping, can rupture independently of the adjacent Prince William Sound segment that is presently locked.
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Earth observation views of the Aleutian Mt. Range taken during STS-99
2000-03-16
STS099-749-089 (11-22 February 2000) ---As evidenced by this 70mm frame from the Space Shuttle Endeavour, the Alaska Peninsula and Aleutian Islands form a long arc that intervenes between the Bering Sea and the northern Pacific Ocean. This view is of the snowy south coast of the peninsula, from Chignik Bay and Cape Kumliun (on the triangular peninsula) northeastward to Chiginagak Bay and David Island. Port Heiden is the darker area of little ice on the north coast. Within the rim of the Aniakchak volcanic crater (4,450 feet at highest point) the frozen waters of Surprise Lake are visible. The North American and Pacific tectonic plates are converging in this region at a rate of about 5 centimeters a year. The Pacific plate descends beneath North America, producing a deep trench along the south coast; the Aleutian Trench reaches depths greater than 25,000 ft. In such regions (subduction zones) volcanoes form on the overriding plate -- the North American plate in this instance; Aniakchak is one of the many young volcanoes in this arc.
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Bond, Alexander L; Jones, Ian L; Williams, Jeffrey C; Byrd, G Vernon
2010-08-01
The ingestion of plastic marine debris is a chronic problem for some of the world's seabird species, contributing to reduced chick survival, population declines, and deposition of contaminants via absorption in birds' gastrointestinal tract. We analysed the frequency of ingested plastic in chick meals delivered by adults in four species of auklet - Crested (Aethia cristatella), Least (A. pusilla), Parakeet (A. psittacula), and Whiskered (A. pygmaea) - from three breeding colonies in the Aleutian Islands, Alaska, USA over a 14-year period from 1993 to 2006. Among 2541 chick meals, we found plastic in only one - from a Whiskered Auklet on Buldir Island in 1993. While adult Parakeet Auklets have a high frequency of plastic ingestion (over 90%), no chick meals contained plastic. Unlike other seabirds, the planktivorous auklets do not appear to offload plastic to their chicks, and we conclude that auklet chicks are probably at a low risk of contamination from plastic debris. Copyright 2010 Elsevier Ltd. All rights reserved.
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A tectonic earthquake sequence preceding the April-May 1999 eruption of Shishaldin Volcano, Alaska
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.
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Tilling, Robert I.; Koyanagi, R.Y.; Lipman, P.W.; Lockwood, J.P.; Moore, J.G.; Swanson, D.A.
1976-01-01
The largest earthquake in over a century--magnitude 7.2 on the Richter Scale--struck Hawaii the morning of November 29, 1975, at 0448. It was centered about 5 km beneath the Kalapana area on the southeastern coast of the island at 19? 20.1 ' N., long 155? 01.4 ' W.). The earthquake was preceded by numerous foreshocks, the largest of which was a 5.7-magnitude jolt at 0336 the same morning, and was accompanied, or closely followed, by a tsunami seismic sea wave), massive ground movements, hundreds of aftershocks, and a volcanic eruption. The tsunami reached a height of 12.2-14.6 m above sea level on the southeastern coast about 25 km west of the earthquake center, elsewhere generally 8 m or less. The south flank of Kilauea Volcano, which forms the southeastern part of the island, was deformed by dislocations along old and new faults along a 25-km long zone. Downward and seaward fault displacements resulted in widespread subsidence, locally as much as 3.5 m, leaving coconut palms standing in the sea and nearly submerging a small, near-shore island. A brief, small-volume volcanic eruption, triggered by the earthquake and associated ground movements occurred at Kilauea's summit about three-quarters of an hour later. The earthquake, together with the tsunami it generated, locally caused severe property damage in the southeastern part of the island; the tsunami also caused two deaths. Damage from the earthquake and related catastrophic events is estimated by the Hawaii Civil Defense Agency at about $4.1 million. The 1975 Kalapana earthquake and accompanying events represent the latest events in a recurring pattern of behavior for Kilauea. A large earthquake of about the same magnitude, tsunami, subsidence, and eruption occurred at Kilauea in 1868, and a less powerful earthquake and similar related processes are believed to have occurred in 1823. Indeed, the geologic evidence suggests that such events have been repeated many times in Kilauea's past and will continue. The
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Plafter, George
1967-01-01
Two reverse faults on southwestern Montague Island in Prince William Sound were reactivated during the earthquake of March 27, 1964. New fault scarps, fissures, cracks, and flexures appeared in bedrock and unconsolidated surficial deposits along or near the fault traces. Average strike of the faults is between N. 37° E. and N. 47° E.; they dip northwest at angles ranging from 50° to 85°. The dominant motion was dip slip; the blocks northwest of the reactivated faults were relatively upthrown, and both blocks were upthrown relative to sea level. No other earthquake faults have been found on land. The Patton Bay fault on land is a complex system of en echelon strands marked by a series of spectacular landslides along the scarp and (or) by a zone of fissures and flexures on the upthrown block that locally is as much as 3,000 feet wide. The fault can be traced on land for 22 miles, and it has been mapped on the sea floor to the southwest of Montague Island an additional 17 miles. The maximum measured vertical component of slip is 20 to 23 feet and the maximum indicated dip slip is about 26 feet. A left-lateral strike-slip component of less than 2 feet occurs near the southern end of the fault on land where its strike changes from northeast to north. Indirect evidence from the seismic sea waves and aftershocks associated with the earthquake, and from the distribution of submarine scarps, suggests that the faulting on and near Montague Island occurred at the northeastern end of a reactivated submarine fault system that may extend discontinuously for more than 300 miles from Montague Island to the area offshore of the southeast coast of Kodiak Island. The Hanning Bay fault is a minor rupture only 4 miles long that is marked by an exceptionally well defined almost continuous scarp. The maximum measured vertical component of slip is 16⅓ feet near the midpoint, and the indicated dip slip is about 20 feet. There is a maximum left-lateral strike-slip component of one
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Seasonal and distributional patterns of seabirds along the Aleutian Archipelago
Renner, M.; Hunt, G.L.; Piatt, John F.; Byrd, G.V.
2008-01-01
The Aleutian Archipelago is of global importance to seabirds during the northern summer, but little is known about seabird use of these waters during winter. We compare summer and winter abundances of seabirds around 3 islands: Buldir in the western, Kasatochi in the central, and Aiktak in the eastern Aleutians. The density of combined seabird biomass in nearshore marine waters was higher in summer than in winter at Buldir and Kasatochi, but was higher in winter at Aiktak, despite the departure of abundant migratory species. Comparing foraging guilds, we found that only piscivores increased at the western and central sites in winter, whereas at the eastern site several planktivorous species increased as well. The only planktivore remaining in winter at the central and western sites in densities comparable to summer densities was whiskered auklet Aethia pygmaea. Crested auklet Aethia cristatella and thick-billed murre Uria lomvia showed the greatest proportional winter increase at the eastern site. The seasonal patterns of the seabird communities suggest a winter breakdown of the copepod-based food web in the central and western parts of the archipelago, and a system that remains rich in euphausiids in the eastern Aleutians. We suggest that in winter crested auklets take the trophic role that short-tailed shearwaters Puffinus tenuirostris occupy during summer. We hypothesize that advection of euphausiids in the Aleutian North Slope Current is important for supporting the high biomass of planktivores that occupy the Unimak Pass region on a year-round basis. ?? Inter-Research 2008.
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Sea otter population declines in the Aleutian Archipelago
Doroff, Angela M.; Estes, James A.; Tinker, M. Tim; Burn, Douglas M.; Evans, Thomas J.
2003-01-01
Sea otter (Enhydra lutris) populations were exploited to near extinction and began to recover after the cessation of commercial hunting in 1911. Remnant colonies of sea otters in the Aleutian archipelago were among the first to recover; they continued to increase through the 1980s but declined abruptly during the 1990s. We conducted an aerial survey of the Aleutian archipelago in 2000 and compared results with similar surveys conducted in 1965 and 1992. The number of sea otters counted decreased by 75% between 1965 and 2000; 88% for islands at equilibrial density in 1965. The population decline likely began in the mid-1980s and declined at a rate of 17.5%/year in the 1990s. The minimal population estimate was 8,742 sea otters in 2000. The population declined to a uniformly low density in the archipelago, suggesting a common and geographically widespread cause. These data are in general agreement with the hypothesis of increased predation on sea otters. These data chronicle one of the most widespread and precipitous population declines for a mammalian carnivore in recorded history.
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Geological and biological heterogeneity of the Aleutian margin (1965-4822 m)
NASA Astrophysics Data System (ADS)
Rathburn, A. E.; Levin, L. A.; Tryon, M.; Gieskes, J. M.; Martin, J. B.; Pérez, M. E.; Fodrie, F. J.; Neira, C.; Fryer, G. J.; Mendoza, G.; McMillan, P. A.; Kluesner, J.; Adamic, J.; Ziebis, W.
2009-01-01
Geological, biological and biogeochemical characterization of the previously unexplored margin off Unimak Island, Alaska between 1965 and 4822 m water depth was conducted to examine: (1) the geological processes that shaped the margin, (2) the linkages between depth, geomorphology and environmental disturbance in structuring benthic communities of varying size classes and (3) the existence, composition and nutritional sources of methane seep biota on this margin. The study area was mapped and sampled using multibeam sonar, a remotely operated vehicle (ROV) and a towed camera system. Our results provide the first characterization of the Aleutian margin mid and lower slope benthic communities (microbiota, foraminifera, macrofauna and megafauna), recognizing diverse habitats in a variety of settings. Our investigations also revealed that the geologic feature known as the “Ugamak Slide” is not a slide at all, and could not have resulted from a large 1946 earthquake. However, sediment disturbance appears to be a pervasive feature of this margin. We speculate that the deep-sea occurrence of high densities of Elphidium, typically a shallow-water foraminiferan, results from the influence of sediment redeposition from shallower habitats. Strong representation of cumacean, amphipod and tanaid crustaceans among the Unimak macrofauna may also reflect sediment instability. Although some faunal abundances decline with depth, habitat heterogeneity and disturbance generated by canyons and methane seepage appear to influence abundances of biota in ways that supercede any clear depth gradient in organic matter input. Measures of sediment organic matter and pigment content as well as C and N isotopic signatures were highly heterogeneous, although the availability of organic matter and the abundance of microorganisms in the upper sediment (1-5 cm) were positively correlated. We report the first methane seep on the Aleutian slope in the Unimak region (3263-3285 m), comprised of
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NASA Astrophysics Data System (ADS)
Chao, K.; Gonzalez-Huizar, H.; Tang, V.; Klaeser, R. D.; Mattia, M.; Van der Lee, S.
2017-12-01
Triggered tremor is one type of slow earthquake that activated by teleseismic surfaces waves of large magnitude earthquake. Observations of triggered tremor can help to evaluate the background ambient tremor rate and slow slip events in the surrounding region. The Mw 8.1 Tehuantepec earthquake in Mexico is an ideal tremor-triggering candidate for a global search for triggered tremor. Here, we examine triggered tremor globally following the M8.1 event and model the tremor-triggering potential. We examine 7,000 seismic traces and found a widely spread triggered tremor along the western coast of the North America occur during the surface waves of the Mw 8.1 event. Triggered tremor appeared in the San Jacinto Fault, San Andreas Fault around Parkfield, and Calaveras Fault in California, in Vancouver Island in Cascadia subduction zone, in Queen Charlotte Margin and Eastern Denali Fault in Canada, and in Alaska and Aleutian Arc. In addition, we observe a newly found triggered tremor source in Mt. Etna in Sicily Island, Italy. However, we do not find clear triggered tremor evidences in the tremor active regions in Japan, Taiwan, and in New Zealand. We model tremor-triggering potential at the triggering earthquake source and triggered tremor sources. Our modeling results suggest the source parameters of the M8.1 triggering events and the stress at the triggered fault zone are two critical factors to control tremor-triggering threshold.
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NASA Astrophysics Data System (ADS)
Martin, C.; Nicolaysen, K. P.; McConville, K.; Hatfield, V.; West, D.
2013-12-01
By examining the existing geological and archeological record of radiocarbon dated Aleutian tephras of the last 12,000 years, this study sought to determine whether there were spatial or temporal patterns of explosive eruptive activity. The Holocene tephra record has important implications because two episodes of migration and colonization by humans of distinct cultures established the Unangan/Aleut peoples of the Aleutian Islands concurrently with the volcanic activity. From Aniakchak Volcano on the Alaska Peninsula to the Andreanof Islands (158 to 178° W longitude), 55 distinct tephras represent significant explosive eruptions of the last 12,000 years. Initial results suggest that the Andreanof and Fox Island regions of the archipelago have had frequent explosive eruptions whereas the Islands of Four Mountains, Rat, and Near Island regions have apparently had little or no eruptive activity. However, one clear result of the investigation is that sampling bias strongly influences the apparent spatial patterns. For example field reconnaissance in the Islands of Four Mountains documents two Holocene calderas and a minimum of 20 undated tephras in addition to the large ignimbrites. Only the lack of significant explosive activity in the Near Islands seems a valid spatial result as archeological excavations and geologic reports failed to document Holocene tephras there. An intriguing preliminary temporal pattern is the apparent absence of large explosive eruptions across the archipelago from ca. 4,800 to 6,000 yBP. To test the validity of apparent patterns, a statistical treatment of the compiled data grappled with the sampling bias by considering three confounding variables: larger island size allows more opportunity for geologic preservation of tephras; larger magnitude eruption promotes tephra preservation by creating thicker and more widespread deposits; the comprehensiveness of the tephra sampling of each volcano and island varies widely because of logistical and
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Fisher, Michael A.; Geist, Eric L.; Sliter, Ray; Wong, Florence L.; Reiss, Carol; Mann, Dennis M.
2007-01-01
On April 1, 2007, a destructive earthquake (Mw 8.1) and tsunami struck the central Solomon Islands arc in the southwestern Pacific Ocean. The earthquake had a thrust-fault focal mechanism and occurred at shallow depth (between 15 km and 25 km) beneath the island arc. The combined effects of the earthquake and tsunami caused dozens of fatalities and thousands remain without shelter. We present a preliminary analysis of the Mw-8.1 earthquake and resulting tsunami. Multichannel seismic-reflection data collected during 1984 show the geologic structure of the arc's frontal prism within the earthquake's rupture zone. Modeling tsunami-wave propagation indicates that some of the islands are so close to the earthquake epicenter that they were hard hit by tsunami waves as soon as 5 min. after shaking began, allowing people scant time to react.
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49 CFR 71.12 - Hawaii-Aleutian zone.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 49 Transportation 1 2010-10-01 2010-10-01 false Hawaii-Aleutian zone. 71.12 Section 71.12 Transportation Office of the Secretary of Transportation STANDARD TIME ZONE BOUNDARIES § 71.12 Hawaii-Aleutian zone. The seventh zone, the Hawaii-Aleutian standard time zone, includes the entire State of Hawaii and...
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NASA Astrophysics Data System (ADS)
Rahimi, A.; Shahrisvand, M.
2017-09-01
GRACE satellites (the Gravity Recovery And climate Experiment) are very useful sensors to extract gravity anomalies after earthquakes. In this study, we reveal co-seismic signals of the two combined earthquakes, the 2006 Mw8.3 thrust and 2007 Mw8.1 normal fault earthquakes of the central Kuril Islands from GRACE observations. We compute monthly full gravitational gradient tensor in the local north-east-down frame for Kuril Islands earthquakes without spatial averaging and de-striping filters. Some of gravitational gradient components (e.g. ΔVxx, ΔVxz) enhance high frequency components of the earth gravity field and reveal more details in spatial and temporal domain. Therefore, co-seismic activity can be better illustrated. For the first time, we show that the positive-negative-positive co-seismic ΔVxx due to the Kuril Islands earthquakes ranges from - 0.13 to + 0.11 milli Eötvös, and ΔVxz shows a positive-negative-positive pattern ranges from - 0.16 to + 0.13 milli Eötvös, agree well with seismic model predictions.
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The 2006-2007 Kuril Islands great earthquake sequence
Lay, T.; Kanamori, H.; Ammon, C.J.; Hutko, Alexander R.; Furlong, K.; Rivera, L.
2009-01-01
The southwestern half of a ???500 km long seismic gap in the central Kuril Island arc subduction zone experienced two great earthquakes with extensive preshock and aftershock sequences in late 2006 to early 2007. The nature of seismic coupling in the gap had been uncertain due to the limited historical record of prior large events and the presence of distinctive upper plate, trench and outer rise structures relative to adjacent regions along the arc that have experienced repeated great interplate earthquakes in the last few centuries. The intraplate region seaward of the seismic gap had several shallow compressional events during the preceding decades (notably an MS 7.2 event on 16 March 1963), leading to speculation that the interplate fault was seismically coupled. This issue was partly resolved by failure of the shallow portion of the interplate megathrust in an MW = 8.3 thrust event on 15 November 2006. This event ruptured ???250 km along the seismic gap, just northeast of the great 1963 Kuril Island (Mw = 8.5) earthquake rupture zone. Within minutes of the thrust event, intense earthquake activity commenced beneath the outer wall of the trench seaward of the interplate rupture, with the larger events having normal-faulting mechanisms. An unusual double band of interplate and intraplate aftershocks developed. On 13 January 2007, an MW = 8.1 extensional earthquake ruptured within the Pacific plate beneath the seaward edge of the Kuril trench. This event is the third largest normal-faulting earthquake seaward of a subduction zone on record, and its rupture zone extended to at least 33 km depth and paralleled most of the length of the 2006 rupture. The 13 January 2007 event produced stronger shaking in Japan than the larger thrust event, as a consequence of higher short-period energy radiation from the source. The great event aftershock sequences were dominated by the expected faulting geometries; thrust faulting for the 2006 rupture zone, and normal faulting for
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NASA Astrophysics Data System (ADS)
Oda, Takuma; Nakamura, Mamoru
2017-09-01
We estimated the location and magnitude of earthquakes constituting the 1858 earthquake swarm in the central Ryukyu Islands using the felt earthquakes recorded by Father Louis Furet who lived in Naha, Okinawa Island, in the middle of the nineteenth century. First, we estimated the JMA seismic intensity of the earthquakes by interpreting the words used to describe the shaking. Next, using the seismic intensity and shaking duration of the felt earthquakes, we estimated the epicentral distance and magnitude range of three earthquakes in the swarm. The results showed that the epicentral distances of the earthquakes were 20-250 km and that magnitudes ranged between 4.5 and 6.5, with a strong correlation between epicentral distance and magnitude. Since the rumblings accompanying some earthquakes in the swarm were heard from a northward direction, the swarm probably occurred to the north of Naha. The most likely source area for the 1858 swarm is the central Okinawa Trough, where a similar swarm event occurred in 1980. If the 1858 swarm occurred in the central Okinawa Trough, the estimated maximum magnitude would have reached 6-7. In contrast, if the 1858 swarm occurred in the vicinity of Amami Island, which is the second most likely candidate area, it would have produced a cluster of magnitude 7-8 earthquakes.[Figure not available: see fulltext.
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Waythomas, C.F.
1999-01-01
Akutan Volcano is one of the most active volcanoes in the Aleutian arc, but until recently little was known about its history and eruptive character. Following a brief but sustained period of intense seismic activity in March 1996, the Alaska Volcano Observatory began investigating the geology of the volcano and evaluating potential volcanic hazards that could affect residents of Akutan Island. During these studies new information was obtained about the Holocene eruptive history of the volcano on the basis of stratigraphic studies of volcaniclastic deposits and radiocarbon dating of associated buried soils and peat. A black, scoria-bearing, lapilli tephra, informally named the 'Akutan tephra,' is up to 2 m thick and is found over most of the island, primarily east of the volcano summit. Six radiocarbon ages on the humic fraction of soil A-horizons beneath the tephra indicate that the Akutan tephra was erupted approximately 1611 years B.P. At several locations the Akutan tephra is within a conformable stratigraphic sequence of pyroclastic-flow and lahar deposits that are all part of the same eruptive sequence. The thickness, widespread distribution, and conformable stratigraphic association with overlying pyroclastic-flow and lahar deposits indicate that the Akutan tephra likely records a major eruption of Akutan Volcano that may have formed the present summit caldera. Noncohesive lahar and pyroclastic-flow deposits that predate the Akutan tephra occur in the major valleys that head on the volcano and are evidence for six to eight earlier Holocene eruptions. These eruptions were strombolian to subplinian events that generated limited amounts of tephra and small pyroclastic flows that extended only a few kilometers from the vent. The pyroclastic flows melted snow and ice on the volcano flanks and formed lahars that traveled several kilometers down broad, formerly glaciated valleys, reaching the coast as thin, watery, hyperconcentrated flows or water floods. Slightly
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NASA Astrophysics Data System (ADS)
Suleimani, E.; Nicolsky, D.; Freymueller, J. T.; Koehler, R.
2013-12-01
The Alaska Earthquake Information Center conducts tsunami inundation mapping for coastal communities in Alaska along several segments of the Aleutian Megathrust, each having a unique seismic history and tsunami generation potential. Accurate identification and characterization of potential tsunami sources is a critical component of our project. As demonstrated by the 2011 Tohoku-oki tsunami, correct estimation of the maximum size event for a given segment of the subduction zone is particularly important. In that event, unexpectedly large slip occurred approximately updip of the epicenter of the main shock, based on seafloor GPS and seafloor pressure gage observations, generating a much larger tsunami than anticipated. This emphasizes the importance of the detailed knowledge of the region-specific subduction processes, and using the most up-to-date geophysical data and research models that define the magnitude range of possible future tsunami events. Our study area extends from the eastern half of the 1957 rupture zone to Kodiak Island, covering the 1946 and 1938 rupture areas, the Shumagin gap, and the western part of the 1964 rupture area. We propose a strategy for generating worst-case credible tsunami scenarios for locations that have a short or nonexistent paleoseismic/paleotsunami record, and in some cases lack modern seismic and GPS data. The potential tsunami scenarios are built based on a discretized plate interface model fit to the Slab 1.0 model geometry. We employ estimates of slip deficit along the Aleutian Megathrust from GPS campaign surveys, the Slab 1.0 interface surface, empirical magnitude-slip relationships, and a numerical code that distributes slip among the subfault elements, calculates coseismic deformations and solves the shallow water equations of tsunami propagation and runup. We define hypothetical asperities along the megathrust and in down-dip direction, and perform a set of sensitivity model runs to identify coseismic deformation
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The 7.2 magnitude earthquake, November 1975, Island of Hawaii
1976-01-01
It was centered about 5 km beneath the Kalapana area on the southeastern coast of Hawaii, the largest island of the Hawaiian chain (Fig. 1) and was preceded by numerous foreshocks. The event was accompanied, or followed shortly, by a tsunami, large-scale ground movemtns, hundreds of aftershocks, an eruption in the summit caldera of Kilauea Volcano. The earthquake and the tsunami it generated produced about 4.1 million dollars in property damage, and the tsumani caused two deaths. Although we have some preliminary findings about the cause and effects of the earthquake, detailed scientific investigations will take many more months to complete. This article is condensed from a recent preliminary report (Tillings an others 1976)
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NASA Astrophysics Data System (ADS)
Miyagi, Yousuke; Ozawa, Taku; Shimada, Masanobu
2009-10-01
On April 1, 2007 (UTC), a large Mw 8.1 interplate earthquake struck the Solomon Islands subduction zone where complicated tectonics result from the subduction of four plates. Extensive ground movements and a large tsunami occurred in the epicentral area causing severe damage over a wide area. Using ALOS/PALSAR data and the DInSAR technique, we detected crustal deformation exceeding 2 m in islands close to the epicenter. A slip distribution of the inferred seismic fault was estimated using geodetic information derived from DInSAR processing and field investigations. The result indicates large slip areas around the hypocenter and the centroid. It is possible that the largest slip area is related to subduction of the plate boundary between the Woodlark and Australian plates. A small slip area between those large slip areas may indicate weak coupling due to thermal activity related to volcanic activity on Simbo Island. The 2007 earthquake struck an area where large earthquake has not occurred since 1970. Most of this seismic gap was filled by the 2007 events, however a small seismic gap still remains in the southeastern region of the 2007 earthquake.
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Eberhart-Phillips, D.; Christensen, D.H.; Brocher, T.M.; Hansen, R.; Ruppert, N.A.; Haeussler, Peter J.; Abers, G.A.
2006-01-01
In southern and central Alaska the subduction and active volcanism of the Aleutian subduction zone give way to a broad plate boundary zone with mountain building and strike-slip faulting, where the Yakutat terrane joins the subducting Pacific plate. The interplay of these tectonic elements can be best understood by considering the entire region in three dimensions. We image three-dimensional seismic velocity using abundant local earthquakes, supplemented by active source data. Crustal low-velocity correlates with basins. The Denali fault zone is a dominant feature with a change in crustal thickness across the fault. A relatively high-velocity subducted slab and a low-velocity mantle wedge are observed, and high Vp/Vs beneath the active volcanic systems, which indicates focusing of partial melt. North of Cook Inlet, the subducted Yakutat slab is characterized by a thick low-velocity, high-Vp/Vs, crust. High-velocity material above the Yakutat slab may represent a residual older slab, which inhibits vertical flow of Yakutat subduction fluids. Alternate lateral flow allows Yakutat subduction fluids to contribute to Cook Inlet volcanism and the Wrangell volcanic field. The apparent northeast edge of the subducted Yakutat slab is southwest of the Wrangell volcanics, which have adakitic composition consistent with melting of this Yakutat slab edge. In the mantle, the Yakutat slab is subducting with the Pacific plate, while at shallower depths the Yakutat slab overthrusts the shallow Pacific plate along the Transition fault. This region of crustal doubling within the shallow slab is associated with extremely strong plate coupling and the primary asperity of the Mw 9.2 great 1964 earthquake. Copyright 2006 by the American Geophysical Union.
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Wilson, Frederic H.; White, Willis H.; Detterman, Robert L.
1988-01-01
Geologic mapping of the Port Moller, Stepovak Bay, and Simeonof Island quadrangles was begun under the auspices of the Alaska Mineral Resource Assessment Program (AMRAP) in 1983 . Two important mineral deposits are located in the Port Moller quadrangle; the Pyramid prospect is the largest copper porphyry system in the Aleutian Arc, and the Apollo Mine is the only gold mine to reach production status in the Aleutian Arc.
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Seismogenic structures of the 2006 ML4.0 Dangan Island earthquake offshore Hong Kong
NASA Astrophysics Data System (ADS)
Xia, Shaohong; Cao, Jinghe; Sun, Jinlong; Lv, Jinshui; Xu, Huilong; Zhang, Xiang; Wan, Kuiyuan; Fan, Chaoyan; Zhou, Pengxiang
2018-02-01
The northern margin of the South China Sea, as a typical extensional continental margin, has relatively strong intraplate seismicity. Compared with the active zones of Nanao Island, Yangjiang, and Heyuan, seismicity in the Pearl River Estuary is relatively low. However, a ML4.0 earthquake in 2006 occurred near Dangan Island (DI) offshore Hong Kong, and this site was adjacent to the source of the historical M5.8 earthquake in 1874. To reveal the seismogenic mechanism of intraplate earthquakes in DI, we systematically analyzed the structural characteristics in the source area of the 2006 DI earthquake using integrated 24-channel seismic profiles, onshore-offshore wide-angle seismic tomography, and natural earthquake parameters. We ascertained the locations of NW- and NE-trending faults in the DI sea and found that the NE-trending DI fault mainly dipped southeast at a high angle and cut through the crust with an obvious low-velocity anomaly. The NW-trending fault dipped southwest with a similar high angle. The 2006 DI earthquake was adjacent to the intersection of the NE- and NW-trending faults, which suggested that the intersection of the two faults with different strikes could provide a favorable condition for the generation and triggering of intraplate earthquakes. Crustal velocity model showed that the high-velocity anomaly was imaged in the west of DI, but a distinct entity with low-velocity anomaly in the upper crust and high-velocity anomaly in the lower crust was found in the south of DI. Both the 1874 and 2006 DI earthquakes occurred along the edge of the distinct entity. Two vertical cross-sections nearly perpendicular to the strikes of the intersecting faults revealed good spatial correlations between the 2006 DI earthquake and the low to high speed transition in the distinct entity. This result indicated that the transitional zone might be a weakly structural body that can store strain energy and release it as a brittle failure, resulting in an earthquake
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NASA Astrophysics Data System (ADS)
Peng, Z.; Yao, D.; Fry, B.; Wallace, L. M.; Kaneko, Y.; Meng, X.
2017-12-01
We conduct a systematic search for dynamically triggered earthquakes in the North Island of New Zealand following the 11/13/2016 Mw7.8 Kaikoura earthquake. This event ruptured multiple faults in the northeastern South Island of New Zealand, and propagated for more than 170 km mostly in the NE direction. By examining earthquakes listed in the GeoNet catalog, we can observe a clear increase of microseismicity in the North Island following the Kaikoura mainshock. However, visual inspection of high-frequency seismograms recorded by 130 dense broadband and short-period sensors revealed that many local earthquakes were not captured by the GeoNet catalog, likely due to being obscured by the mainshock coda and intense aftershock sequence in the South Island. To further quantify the triggering phenomenon in the North Island following the mainshock, we apply a waveform matched filter technique to obtain a more complete catalog around the mainshock occurrence time. Assuming many of the triggered North Island events occur on faults that were active prior to the Mw7.8 earthquake, we select 17,500 events listed in the GeoNet catalog from 04/2016 to 03/2017 as templates to scan through continuous data from 11/01/2017 to 11/30/2017. Currently, 19,000 additional events are detected within the one month study period, comparing to 1,950 events listed in the catalog. The initial locations from the GeoNet catalog reveal that most triggered earthquakes occurred in the uppermost crust (<20km), likely linked to inland crustal faults and/or volcanic systems. In addition, another burst of seismicity (including a magnitude 6 event) occurred near the Wairarapa coastline about 400km north of the main rupture, which was likely driven by a M7 slow slip events triggered by the mainshock. Our next step is to calibrate the magnitudes of both catalog and newly detected events by measuring their principle component slopes. In addition, we plan to measure cross-correlation differential times between
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Aleutian volcanic eruption taken by Expedition 13 crewmember
2006-05-23
ISS013-E-24184 (23 May 2006) --- Eruption of Cleveland Volcano, Aleutian Islands, Alaska is featured in this image photographed by an Expedition 13 crewmember on the International Space Station. This most recent eruption was first reported to the Alaska Volcano Observatory by astronaut Jeffrey N. Williams, NASA space station science officer and flight engineer, at 3:00 p.m. Alaska Daylight Time (23:00 GMT). This image, acquired shortly after the beginning of the eruption, captures the ash plume moving west-southwest from the summit vent. The eruption was short-lived; the plume had completely detached from the volcano summit two hours later.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-28
... manages the groundfish fishery in the GOA exclusive economic zone according to the Fishery Management Plan.... 101126521-0640-2] RIN 0648-XA731 Fisheries of the Exclusive Economic Zone Off Alaska; Skates in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS), National...
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Inter-plate aseismic slip on the subducting plate boundaries estimated from repeating earthquakes
NASA Astrophysics Data System (ADS)
Igarashi, T.
2015-12-01
Sequences of repeating earthquakes are caused by repeating slips of small patches surrounded by aseismic slip areas at plate boundary zones. Recently, they have been detected in many regions. In this study, I detected repeating earthquakes which occurred in Japan and the world by using seismograms observed in the Japanese seismic network, and investigated the space-time characteristics of inter-plate aseismic slip on the subducting plate boundaries. To extract repeating earthquakes, I calculate cross-correlation coefficients of band-pass filtering seismograms at each station following Igarashi [2010]. I used two data-set based on USGS catalog for about 25 years from May 1990 and JMA catalog for about 13 years from January 2002. As a result, I found many sequences of repeating earthquakes in the subducting plate boundaries of the Andaman-Sumatra-Java and Japan-Kuril-Kamchatka-Aleutian subduction zones. By applying the scaling relations among a seismic moment, recurrence interval and slip proposed by Nadeau and Johnson [1998], they indicate the space-time changes of inter-plate aseismic slips. Pairs of repeating earthquakes with the longest time interval occurred in the Solomon Islands area and the recurrence interval was about 18.5 years. The estimated slip-rate is about 46 mm/year, which correspond to about half of the relative plate motion in this area. Several sequences with fast slip-rates correspond to the post-seismic slips after the 2004 Sumatra-Andaman earthquake (M9.0), the 2006 Kuril earthquake (M8.3), the 2007 southern Sumatra earthquake (M8.5), and the 2011 Tohoku-oki earthquake (M9.0). The database of global repeating earthquakes enables the comparison of the inter-plate aseismic slips of various plate boundary zones of the world. I believe that I am likely to detect more sequences by extending analysis periods in the area where they were not found in this analysis.
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-10-21
... manages the groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management.... 0910131363-0087-01] RIN 0648-XZ85 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-03-26
... the groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management Plan.... 0910131363-0087-02] RIN 0648-XV52 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-09-01
... the groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management Plan.... 0910131363-0087-02] RIN 0648-XY62 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-01-28
... groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management Plan for.... 0810141351-9087-02] RIN 0648-XU11 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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NASA Astrophysics Data System (ADS)
Ryan, K. J.; Geist, E. L.; Oglesby, D. D.; Kyriakopoulos, C.
2016-12-01
Motivated by the 2011 Mw 9 Tohoku-Oki event, we explore the effects of realistic fault dynamics on slip, free surface deformation, and the resulting tsunami generation and local propagation from a hypothetical Mw 9 megathrust earthquake along the Alaskan-Aleutian (A-A) Megathrust. We demonstrate three scenarios: a spatially-homogenous prestress and frictional parameter model and two models with rate-strengthening-like friction (e.g., Dieterich, 1992). We use a dynamic finite element code to model 3-D ruptures, using time-weakening friction (Andrews, 2004) as a proxy for rate-strengthening friction, along a portion of the A-A subduction zone. Given geometric, material, and plate-coupling data along the A-A megathrust assembled from the Science Application for Risk Reduction (SAFRR) team (e.g., Bruns et al., 1987; Hayes et al., 2012; Johnson et al., 2004; Santini et al., 2003; Wells at al., 2003), we are able to dynamically model rupture. Adding frictional-strengthening to a region of the fault reduces both average slip and free surface displacement above the strengthening zone, with the magnitude of the reductions depending on the strengthening zone location. Corresponding tsunami models, which use a finite difference method to solve the long-wave equations (e.g., Liu et al., 1995; Satake, 2002; Shuto, 1991), match sea floor displacement, in time, to the free surface displacement from the rupture models. Tsunami models show changes in local peak amplitudes and beaming patterns for each slip distribution. Given these results, other heterogeneous parameterizations, with respect to prestress and friction, still need to be examined. Additionally, a more realistic fault geometry will likely affect the rupture dynamics. Thus, future work will incorporate stochastic stress and friction distributions as well as a more complex fault geometry based on Slab 1.0 (Hayes et al., 2012).
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Earthquakes, March-April, 1993
Person, Waverly J.
1993-01-01
Worldwide, only one major earthquake (7.0
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-06-08
... fishery in the (BSAI) exclusive economic zone according to the Fishery Management Plan for Groundfish of.... 101126521-0640-02] RIN 0648-XA483 Fisheries of the Exclusive Economic Zone Off Alaska; Alaska Plaice in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-06-08
.... 101126521-0640-02] RIN 0648-XA482 Fisheries of the Exclusive Economic Zone Off Alaska; Alaska Plaice in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS... management area (BSAI). This action is necessary to prevent exceeding the 2011 Alaska plaice total allowable...
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Discrete Scaling in Earthquake Precursory Phenomena: Evidence in the Kobe Earthquake, Japan
NASA Astrophysics Data System (ADS)
Johansen, Anders; Sornette, Didier; Wakita, Hiroshi; Tsunogai, Urumu; Newman, William I.; Saleur, Hubert
1996-10-01
We analyze the ion concentration of groundwater issuing from deep wells located near the epicenter of the recent earthquake of magnitude 6.9 near Kobe, Japan, on January 17, 1995. These concentrations are well fitted by log-periodic modulations around a leading power law. The exponent (real and imaginary parts) is very close to those already found for the fits of precursory seismic activity for Loma Prieta and the Aleutian Islands. This brings further support for the general hypothesis that complex critical exponents are a general phenomenon in irreversible self-organizing systems and particularly in rupture and earthquake phenomena. Nous analysons les fluctuations de concentrations ioniques de l'eau issue de puits profonds situés à proximité de l'épicentre du récent tremblement de terre de magnitude 6.9 proche de Kobe au Japon, le 17 janvier 1995. Ces fluctuations sont bien reproduites par des modulations log-périodiques autour d'une loi de puissance. Les parties réelle et imaginaire de l'exposant sont très proches de celles trouvées précédemment pour les tremblements de terre de Loma Prieta et des Iles Aléoutiennes. Ces résultats renforcent l'hypothèse que des exposants critiques complexes sont une propriété générale des phénomènes de croissance irréversible, et en particulier des problèmes de rupture et des tremblements de terre.
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-09-17
.... 121018563-3418-02] RIN 0648-XC872 Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering... prohibiting retention of sharks in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary because the 2013 total allowable catch (TAC) of sharks in the BSAI has been reached. DATES...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-28
.... 101126521-0640-2] RIN 0648-XA733 Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering... prohibiting retention of sharks in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary because the 2011 total allowable catch (TAC) of sharks in the BSAI has been reached. DATES...
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NASA Astrophysics Data System (ADS)
Bender, A. M.; Witter, R. C.; Munk, L. A.
2012-12-01
Nearly the entire 4000-km-long Alaska-Aleutian megathrust has ruptured in large or great (Mw ≥8) earthquakes in the past 100 years, yet paleoseismic records of earlier events are only documented east of Kodiak Is. in the region of the 1964 Alaska earthquake. The Mw 9.2 1964 earthquake dropped the coast along Cook Inlet and Turnagain Arm by ≤1.8 m and raised shore platforms around Prince William Sound by ≤3 m. Evidence of sudden (coseismic) vertical displacements during megathrust earthquakes are archived in coastal sediments as sharp stratigraphic contacts that record rapid relative sea-level (RSL) changes. We use geochemical analyses of coastal sediments to detect sudden RSL changes at 2 sites above the Alaska-Aleutian megathrust. One site on Knik Arm near Anchorage subsided ~0.6 m during the 1964 earthquake. The other site overlies the Shumagin Islands segment of the megathrust, without rupture since before 1903. Relative to terrestrial sources of sediment, marine sources should be enriched in δ13C, δ15N, and have higher C:N, and Cl- concentrations. Our analyses will test whether these geochemical proxies can provide evidence for sudden RSL change across stratigraphic contacts that record coseismic uplift or subsidence. Coseismic subsidence should be represented by contacts that place sediment with enriched δ13C, δ15N signatures, elevated C:N and Cl- concentrations over sediment with lower values of these geochemical proxies and the reverse for coseismic uplift. A 1-2 m tall, ~0.5-km-long bluff along Knik Arm exposes three buried wetland soils overlain by gray mud. The soils become faint and pinch out to the northeast near a large tidal channel. Other studies of similar buried soils at adjacent sites suggest the youngest soil at Knik Arm subsided in 1964. 14C analyses of plant fossils in two older soils will provide age estimates for earlier events. We will apply the proposed geochemical methods to 20 samples collected along a forested upland to tidal
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Plafker, George; Kachadoorian, Reuben
1966-01-01
Kodiak Island and the nearby islands constitute a mountainous landmass with an aggregate area of 4,900 square miles that lies at the western border of the Gulf of Alaska and from 20 to 40 miles off the Alaskan mainland. Igneous and metamorphic rocks underlie most of the area except for a narrow belt of moderately to poorly indurated rocks bordering the Gulf of Alaska coast and local accumulations of unconsolidated alluvial and marine deposits along the streams and coast. The area is relatively undeveloped and is sparsely inhabited. About 4,800 of the 5,700 permanent residents in the area live in the city of Kodiak or at the Kodiak Naval Station. The great earthquake, which occurred on March 27, 1964, at 5:36 p.m. Alaska standard time (March 28,1964, 0336 Greenwich mean time), and had a Richter magnitude of 8.4-8.5, was the most severe earthquake felt on Kodiak Island and its nearby islands in modern times. Although the epicenter lies in Prince William Sound 250 miles northeast of Kodiak—the principal city of the area—the areal distribution of the thousands of aftershocks that followed it, the local tectonic deformation, and the estimated source area of the subsequent seismic sea wave, all suggest that the Kodiak group of islands lay immediately adjacent to, and northwest of, the focal region from which the elastic seismic energy was radiated. The duration of strong ground motion in the area was estimated at 2½ minutes. Locally, the tremors were preceded by sounds audible to the human ear and were reportedly accompanied in several places by visible ground waves. Intensity and felt duration of the shocks during the main earthquake and aftershock sequence varied markedly within the area and were strongly influenced by the local geologic environment. Estimated Mercalli intensities in most areas underlain by unconsolidated Quaternary deposits ranged from VIII to as high as IX. In contrast, intensities in areas of upper Tertiary rock ranged from VII to VIII, and in
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Ruppert, Natalia G.; Prejean, Stephanie G.; Hansen, Roger A.
2011-01-01
An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field.
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Solomon Islands 2007 Tsunami Near-Field Modeling and Source Earthquake Deformation
NASA Astrophysics Data System (ADS)
Uslu, B.; Wei, Y.; Fritz, H.; Titov, V.; Chamberlin, C.
2008-12-01
The earthquake of 1 April 2007 left behind momentous footages of crust rupture and tsunami impact along the coastline of Solomon Islands (Fritz and Kalligeris, 2008; Taylor et al., 2008; McAdoo et al., 2008; PARI, 2008), while the undisturbed tsunami signals were also recorded at nearby deep-ocean tsunameters and coastal tide stations. These multi-dimensional measurements provide valuable datasets to tackle the challenging aspects at the tsunami source directly by inversion from tsunameter records in real time (available in a time frame of minutes), and its relationship with the seismic source derived either from the seismometer records (available in a time frame of hours or days) or from the crust rupture measurements (available in a time frame of months or years). The tsunami measurements in the near field, including the complex vertical crust motion and tsunami runup, are particularly critical to help interpreting the tsunami source. This study develops high-resolution inundation models for the Solomon Islands to compute the near-field tsunami impact. Using these models, this research compares the tsunameter-derived tsunami source with the seismic-derived earthquake sources from comprehensive perceptions, including vertical uplift and subsidence, tsunami runup heights and their distributional pattern among the islands, deep-ocean tsunameter measurements, and near- and far-field tide gauge records. The present study stresses the significance of the tsunami magnitude, source location, bathymetry and topography in accurately modeling the generation, propagation and inundation of the tsunami waves. This study highlights the accuracy and efficiency of the tsunameter-derived tsunami source in modeling the near-field tsunami impact. As the high- resolution models developed in this study will become part of NOAA's tsunami forecast system, these results also suggest expanding the system for potential applications in tsunami hazard assessment, search and rescue operations
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Amundsen, C.C.
1985-01-01
Measured and inferred ecological characteristics and holocoenotic factors which affect the dynamics and manifestations of central Aleutian maritime tundra and beach-dune vegetational expressions of Adak and Amchitka Islands are discussed. The known vascular flora is enumerated and predominant taxa are grouped into communities and topoedaphic units. Stability of community composition and structure is elaborated and the absence of ecological succession demonstrated. Perturbations occasioned by human activities which impinge on these remote islands are detailed. The testing and monitoring of subsequent passive and managed recovery of stable vegetation on disturbed areas is described. Selection, preparation and utilization of transplants of Elymusmore » mollis Trin. is documented. Transplants of rhizomes of E. mollis are successful in the reestablishment of vegetative cover in disturbed habitats which are topoedaphically suitable for graminoid success. The responses of plant population stands to environmental processes and habitat insults are reported. The relatively limited but stable biota and the lethargic ecological response as defined by extant vegetational expressions provide field test potentials which mandate further basic and applied research.« less
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-03-29
.... 101126521-0640-02] RIN 0648-XA322 Fisheries of the Exclusive Economic Zone Off Alaska; Octopus in the Bering... allowable catch of octopus in the Bering Sea and Aleutian Islands (BSAI). This action is necessary to allow... subpart H of 50 CFR part 600 and 50 CFR part 679. The 2011 initial total allowable catch (ITAC) of octopus...
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Burger, Joanna; Gochfeld, Michael; Jewett, Stephen C
2007-05-01
Concentrations of 13 radionuclides (137Cs, 129I, 60Co, 152Eu, 90Sr, 99Tc, 241Am, 238Pu, 239,249Pu, 234U, 235U, 236U, 238U) were examined in seven species of invertebrates from Amchitka and Kiska Islands, in the Aleutian Chain of Alaska, using gamma spectroscopy, inductively coupled plasma mass spectroscopy, and alpha spectroscopy. Amchitka Island was the site of three underground nuclear test (1965-1971), and we tested the null hypotheses that there were no differences in radionuclide concentrations between Amchitka and the reference site (Kiska) and there were no differences among species. The only radionuclides where composite samples were above the Minimum Detectable Activity (MDA) were 137Cs, 241Am, 239,249Pu, 234U, 235U, 236U, and 238U. Green sea urchin (Strongylocentrotus polyacanthus), giant chiton (Cryptochiton stelleri), plate limpets (Tectura scutum) and giant Pacific octopus (Enteroctopus dofleini) were only tested for 137Cs; octopus was the only species with detectable levels of 137Cs (0.262 +/- 0.029 Bq/kg, wet weight). Only rock jingle (Pododesmus macroschisma), blue mussel (Mytilus trossulus) and horse mussel (Modiolus modiolus) were analyzed for the actinides. There were no interspecific differences in 241Am and 239,240Pu, and almost no samples above the MDA for 238Pu and 236U. Horse mussels had significantly higher concentrations of 234U (0.844 +/- 0.804 Bq/kg) and 238U (0.730 +/- 0.646) than the other species (both isotopes are naturally occurring). There were no differences in actinide concentrations between Amchitka and Kiska. In general, radionuclides in invertebrates from Amchitka were similar to those from uncontaminated sites in the Northern Hemisphere, and below those from the contaminated Irish Sea. There is a clear research need for authors to report the concentrations of radionuclides by species, rather than simply as 'shellfish', for comparative purposes in determining geographical patterns, understanding possible effects, and for
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Tohoku-Oki Earthquake Tsunami Runup and Inundation Data for Sites Around the Island of Hawaiʻi
Trusdell, Frank A.; Chadderton, Amy; Hinchliffe, Graham; Hara, Andrew; Patenge, Brent; Weber, Tom
2012-01-01
At 0546 U.t.c. March 11, 2011, a Mw 9.0 ("great") earthquake occurred near the northeast coast of Honshu Island, Japan, generating a large tsunami that devastated the east coast of Japan and impacted many far-flung coastal sites around the Pacific Basin. After the earthquake, the Pacific Tsunami Warning Center issued a tsunami alert for the State of Hawaii, followed by a tsunami-warning notice from the local State Civil Defense on March 10, 2011 (Japan is 19 hours ahead of Hawaii). After the waves passed the islands, U.S. Geological Survey (USGS) scientists from the Hawaiian Volcano Observatory (HVO) measured inundation (maximum inland distance of flooding), runup (elevation at maximum extent of inundation) and took photographs in coastal areas around the Island of Hawaiʻi. Although the damage in West Hawaiʻi is well documented, HVO's mapping revealed that East Hawaiʻi coastlines were also impacted by the tsunami. The intent of this report is to provide runup and inundation data for sites around the Island of Hawaiʻi.
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Why the 1964 Great Alaska Earthquake matters 50 years later
West, Michael E.; Haeussler, Peter J.; Ruppert, Natalia A.; Freymueller, Jeffrey T.; ,
2014-01-01
Spring was returning to Alaska on Friday 27 March 1964. A two‐week cold snap had just ended, and people were getting ready for the Easter weekend. At 5:36 p.m., an earthquake initiated 12 km beneath Prince William Sound, near the eastern end of what is now recognized as the Alaska‐Aleutian subduction zone. No one was expecting this earthquake that would radically alter the coastal landscape, influence the direction of science, and indelibly mark the growth of a burgeoning state.
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Ruppert, N.A.; Prejean, S.; Hansen, R.A.
2011-01-01
An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field. Copyright ?? 2011 by the American Geophysical Union.
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Heavy metals in fish from the Aleutians: Interspecific and locational differences
DOE Office of Scientific and Technical Information (OSTI.GOV)
Burger, Joanna, E-mail: burger@biology.rutgers.edu; Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ; Consortium for Risk Evaluation with Stakeholder Participation, Vanderbilt University, Nashville, TN 37235
The objectives of this study were to examine levels of arsenic, cadmium, lead, mercury and selenium in edible tissue of seven species of marine fish collected from several Aleutian islands (in 2004) to determine: (1) interspecific differences, (2) locational differences (among Aleutian Islands), (3) size-related differences in any metal levels within a species, and (4) potential risk to the fish or to predators on the fish, including humans. We also compared metals levels to those of three other fish species previously examined in detail, as well as examining metals in the edible tissue of octopus (Octopus dofleini). Octopus did notmore » have the highest levels of any metal. There were significant interspecific differences in all metal levels among the fish species, although the differences were less than an order of magnitude, except for arsenic (mean of 19,500 ppb in Flathead sole, Hippoglossoides elassodon). Significant intraisland variation occurred among the four sites on Amchitka, but there was not a consistent pattern. There were significant interisland differences for some metals and species. Mercury levels increased significantly with size for several species; lead increased significantly for only one fish species; and cadmium and selenium decreased significantly with size for halibut (Hippoglossus stenolepis). The Alaskan Department of Health and Social Services supports unrestricted consumption of most Alaskan fish species for all people, including pregnant women. Most mean metal concentrations were well below the levels known to adversely affect the fish themselves, or predators that consume them (including humans), except for mercury in three fish species (mean levels just below 0.3 ppm), and arsenic in two fish species. However, even at low mercury levels, people who consume fish almost daily will exceed guideline values from the Centers for Disease Control and the Environmental Protection Agency. - Highlights: • Cadmium, lead, mercury and
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Crustal Deformation and the Seismic Cycle across the Kodiak Islands, Alaska
NASA Technical Reports Server (NTRS)
Sauber, Jeanne; Carver, Gary; Cohen, Steven; King, Robert
2006-01-01
The Kodiak Islands are located approx.120 to 250 km from the Alaska-Aleutian Trench and are within the southern extent of the 1964 Prince William Sound (M(sub W) = 9.2) earthquake rupture and aftershock zone. Here we report new campaign GPS results (1993-2001) from northeastern Kodiak and reprocessed GPS results (1993-1997) from southwestern Kodiak. The rate and orientation of the horizontal velocities, relative to a fixed North America, range from 29.7 +/- 1.7 mm/yr at N30.3degW +/- 3.3deg, located approx.120 km from the deepest point of the trench, to 8.0 +/- 1.3 mm/yr at N62.4degW +/- 9.3deg, located approx.230 km from the trench. We evaluated alternate models of coseismic and interseismic slip to test the importance of the mechanisms that account for surface deformation rates. Near the Gulf of Alaska coastal region of Kodiak the horizontal velocity can be accounted for primarily by the viscoelastic response to plate motion and a locked main thrust zone (MTZ), down-dip creep, and to a lesser extent, slip in the 1964 earthquake. Further inland the dominant mechanisms that account for post-1964 uplift rates are time-dependent, down-dip creep and a locked MTZ; for the horizontal velocity component southwest translation of western Kodiak may be important as well. Based on the pre-1964 and post-1964 earthquake pattern of interseismic earthquakes, we suggest that between the occurrences of great earthquakes like the 1964 event, more moderate to large earthquakes occur in the southwestern Kodiak region than near northeastern Kodiak .
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NASA Astrophysics Data System (ADS)
Ozawa, S.; Miyazaki, S.; Nishimura, T.; Murakami, M.; Kaidzu, M.; Imakiire, T.; Ji, X.
2004-02-01
Analysis of Global Positioning System data shows shrinkage of Miyake Island and the widening between Nijima and Kozu Islands during the period of the Miyake island volcanic activity and the ensuing Izu islands earthquakes in 2000. The estimated time evolution of a model consisting of a dike, creeping faults, and a Mogi source suggests that a crack opening on Miyake Island occurred immediately after the start of the seismic activities on 26 June and ended within several days at the west coast of Miyake Island. After the seabed eruption on 27 June, magma migrated from Miyake Island to Kozu and Nijima Islands within several days. The estimated volume of intruded magma totals around 1.2 × 109 m3. Associated with the magma intrusion between Miyake and Kozu Islands, left-lateral and right-lateral creep motions occurred in regions off the west coast of Miyake Island and near Kozu Island. The accumulated moment energy is equivalent to an earthquake of Mw 6.6 and 6.6 for right-lateral and left-lateral creeping faults, respectively. The estimated magma chamber continued deflation beneath the southwestern part of Miyake Island from 26 June, totaling around 0.12 × 109 m3 in volume change, in addition to the collapse volume of 0.6 × 109 m3 at the summit of Mount Oyama on Miyake Island. The volume change on Miyake Island can be compensated by the migrated magma toward Kozu Island from the deflation source beneath Miyake Island. The deflation speed of the magma chamber beneath Miyake Island decreased and increased before and after the eruption of 14-15 July and 18 August, suggesting a change in balance of mass influx and draining out rate of the magma chamber.
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NASA Astrophysics Data System (ADS)
Heidarzadeh, Mohammad; Harada, Tomoya; Satake, Kenji; Ishibe, Takeo; Gusman, Aditya Riadi
2016-05-01
The July 2015 Mw 7.0 Solomon Islands tsunamigenic earthquake occurred ~40 km north of the February 2013 Mw 8.0 Santa Cruz earthquake. The proximity of the two epicenters provided unique opportunities for a comparative study of their source mechanisms and tsunami generation. The 2013 earthquake was an interplate event having a thrust focal mechanism at a depth of 30 km while the 2015 event was a normal-fault earthquake occurring at a shallow depth of 10 km in the overriding Pacific Plate. A combined use of tsunami and teleseismic data from the 2015 event revealed the north dipping fault plane and a rupture velocity of 3.6 km/s. Stress transfer analysis revealed that the 2015 earthquake occurred in a region with increased Coulomb stress following the 2013 earthquake. Spectral deconvolution, assuming the 2015 tsunami as empirical Green's function, indicated the source periods of the 2013 Santa Cruz tsunami as 10 and 22 min.
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NASA Astrophysics Data System (ADS)
Ioualalen, Mansour; Pelletier, Bernard; Solis Gordillo, Gabriela
2017-07-01
New Caledonia's Loyalty Islands are located in the southwest region of the Pacific ocean in the highly seismogenic southern Vanuatu subduction zone and therefore may be subject to devastating local tsunamis. Over the past 150 years, two large tsunamis were triggered by major earthquakes on March 28th 1875 and September 20th 1920. In this study, we use historical observations of these tsunamis (mostly in the form of testimonials), earthquake scenarios, and tsunami modeling to derive the magnitudes of these earthquakes, as well as tsunami runup and inundation maps. Assuming that these earthquakes were located on the interplate megathrust zone, the 1875 earthquake's magnitude was Mw8.1-8.2 and the 1920 event's magnitude was Mw7.5-7.8. The tsunami damage inflicted on the Lifou and Maré islands was approximately proportional to these magnitudes, with Maré being less impacted due to favorable wave directivity. Damage at Ouvéa island may have varied irregularly with the magnitude due to the effects of resonance. This study demonstrates that the quantitative characteristics of historical tsunamigenic earthquakes may be derived from qualitative estimates of tsunami runup.
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Nature and Significance of the High-Sr Aleutian Lavas
NASA Astrophysics Data System (ADS)
Yogodzinski, G. M.; Arndt, S.; Turka, J. R.; Kelemen, P. B.; Vervoort, J. D.; Portnyagin, M.; Hoernle, K.
2011-12-01
Results of the Western Aleutian Volcano Expedition and German-Russian KALMAR cruises include the discovery of seafloor volcanism at the Ingenstrem Depression and at unnamed seamounts 300 km west of Buldir, the westernmost emergent volcano in the Aleutian arc. These discoveries indicate that the surface expression of active Aleutian volcanism goes below sea level just west of Buldir, but is otherwise continuous along the full length of the arc. Many lavas dredged from western Aleutian seamounts are basalts, geochemically similar to basalts from elsewhere in Aleutians and other arcs (La/Yb 4-8, Sr/Y<30, 87Sr/86Sr=0.7031-0.7033). Western Aleutian dredge samples also include high-Sr lavas (>700 ppm Sr), which are mostly plagioclase-hornblende andesites and dacites with low Y and middle-heavy rare-earth elements, fractionated trace element patterns (Sr/Y=50-200, La/Yb=9-25) and MORB-like isotopes (87Sr/86Sr < 0.7028). The endmember Sr-rich lavas are magnesian rhyodacites (SiO2~68%, Mg# >0.65) with 1250-1700 ppm Sr, 4-7 ppm Y, low abundances of all rare-earth elements (La<7 ppm, Yb<0.4 ppm) and 87Sr/86Sr < 0.70266. The high silica and primitive (high Mg#) character of the high-Sr lavas, combined with their strongly fractionated trace element patterns and MORB-like isotopes are consistent with a source predominantly of subducted basalt and a melt residue that contained garnet. The high-Sr lavas have some characteristics of MORB fluids (low Ce/Pb and unradiogenic Pb), and their highly calc-alkaline nature implies high pre-eruptive water contents[1], but low 87Sr/86Sr indicates that their source was in MORB, not seawater-altered MORB. The high-Sr endmember is clearly present in andesites from some emergent volcanoes in the western Aleutians, and mixing arrays indicate that it may be present in all Aleutian lavas (e.g., 87Sr/86Sr vs. La/Yb or Sr/Y); however, radiogenic Pb and Sr from subducted sediment renders the high-Sr endmember isotopically invisible in most central and
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Evolution of stickleback in 50 years on earthquake-uplifted islands
Lescak, Emily A.; Bassham, Susan L.; Catchen, Julian; Gelmond, Ofer; Sherbick, Mary L.; von Hippel, Frank A.
2015-01-01
How rapidly can animal populations in the wild evolve when faced with sudden environmental shifts? Uplift during the 1964 Great Alaska Earthquake abruptly created freshwater ponds on multiple islands in Prince William Sound and the Gulf of Alaska. In the short time since the earthquake, the phenotypes of resident freshwater threespine stickleback fish on at least three of these islands have changed dramatically from their oceanic ancestors. To test the hypothesis that these freshwater populations were derived from oceanic ancestors only 50 y ago, we generated over 130,000 single-nucleotide polymorphism genotypes from more than 1,000 individuals using restriction site-associated DNA sequencing (RAD-seq). Population genomic analyses of these data support the hypothesis of recent and repeated, independent colonization of freshwater habitats by oceanic ancestors. We find evidence of recurrent gene flow between oceanic and freshwater ecotypes where they co-occur. Our data implicate natural selection in phenotypic diversification and support the hypothesis that the metapopulation organization of this species helps maintain a large pool of genetic variation that can be redeployed rapidly when oceanic stickleback colonize freshwater environments. We find that the freshwater populations, despite population genetic analyses clearly supporting their young age, have diverged phenotypically from oceanic ancestors to nearly the same extent as populations that were likely founded thousands of years ago. Our results support the intriguing hypothesis that most stickleback evolution in fresh water occurs within the first few decades after invasion of a novel environment. PMID:26668399
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GLORIA imagery links sedimentation in Aleutian Trench to Yakutat margin via surveyor channel
DOE Office of Scientific and Technical Information (OSTI.GOV)
Carlson, P.R.; Bruns, T.R.; Mann, D.M.
1990-06-01
GLORIA side-scan sonar imagery shows that the continental slope developing along the active margin of the Gulf of Alaska is devoid of large submarine canyons, in spite of the presence of large glacially formed sea valleys that cross the continental shelf. In the western and northern Gulf, discontinuous, actively growing deformation structures disrupt or divert the downslope transport of sediment into the Aleutian Trench. To the east of Middleton Island, the slope is intensively gullied and incised only by relatively small canyons. At the base of the gullied slope between Pamplona Spur and Alsek Valley, numerous small slope gullies coalescemore » into three turbidity current channels that merge to form the Surveyor deep-sea channel. About 350 km from the margin, the channel crosses the structural barrier formed by the Kodiak-Bowie Seamount chain and heads south for another 150 km where it bends northerly, perhaps influenced by the oceanic basement relief of the Patton Seamounts. The channel, now up to 5 km wide and deeply entrenched to 450 m, continues northerly for 200 km where it intercepts the Aleutian Trench, some 700 km from the Yakutat margin. South of Surveyor Channel, GLORIA imagery revealed evidence of another older channel. The older channel meanders through a gap in the seamount chain and eventually bends northwesterly. This now inactive, largely buried channel may have carried turbidity currents to the Aleutian Trench concurrent with the active Surveyor Channel.« less
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NASA Astrophysics Data System (ADS)
Lay, Thorne; Ye, Lingling; Ammon, Charles J.; Kanamori, Hiroo
2017-02-01
The 17 December 2016 Solomon Islands earthquake (Mw 7.9) initiated 103 km deep in the subducting Solomon Sea slab near the junction of the Solomon Islands and New Britain trenches. Most aftershocks are located near the Solomon Islands plate boundary megathrust west of Bougainville, where previous large interplate thrust faulting earthquakes occurred in 1995 (Mw 7.7) and 1971 (Mw 8.0). Teleseismic body wave modeling and aftershock relocations indicate that the initial 30 s of the 2016 rupture occurred over depths of 90 to 120 km on an intraslab fault dipping 30° to the southwest, almost perpendicular to the dipping slab interface. The next 50 s of rupture took place at depths of 32 to 47 km in the deeper (Domain C) portion of the overlying megathrust fault dipping 35° to the northeast. High susceptibility to triggering in the region accounts for this compound rupture of two separate fault planes.
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Sydeman, William J.; Thompson, Sarah Ann; Piatt, John F.; García-Reyes, Marisol; Zador, Stephani; Williams, Jeffrey C.; Romano, Marc; Renner, Heather
2017-01-01
Seabirds are thought to be reliable, real-time indicators of forage fish availability and the climatic and biotic factors affecting pelagic food webs in marine ecosystems. In this study, we tested the hypothesis that temporal trends and interannual variability in seabird indicators reflect simultaneously occurring bottom-up (climatic) and competitor (pink salmon) forcing of food webs. To test this hypothesis, we derived multivariate seabird indicators for the Bering Sea–Aleutian Island (BSAI) ecosystem and related them to physical and biological conditions known to affect pelagic food webs in the ecosystem. We examined covariance in the breeding biology of congeneric pelagic gulls (kittiwakes Rissa tridactyla and R. brevirostris) andauks (murres Uria aalge and U. lomvia), all of whichare abundant and well-studiedinthe BSAI. At the large ecosystem scale, kittiwake and murre breeding success and phenology (hatch dates) covaried among congeners, so data could be combined using multivariate techniques, but patterns of responsedifferedsubstantially betweenthe genera.Whiledata fromall sites (n = 5)inthe ecosystemcould be combined, the south eastern Bering Sea shelf colonies (St. George, St. Paul, and Cape Peirce) provided the strongest loadings on indicators, and hence had the strongest influence on modes of variability. The kittiwake breeding success mode of variability, dominated by biennial variation, was significantly related to both climatic factors and potential competitor interactions. The murre indicator mode was interannual and only weakly related to the climatic factors measured. The kittiwake phenology indicator mode of variability showed multi-year periods (“stanzas”) of late or early breeding, while the murre phenology indicator showed a trend towards earlier timing. Ocean climate relationships with the kittiwake breeding success indicator suggestthat early-season (winter–spring) environmental conditions and the abundance of pink salmon affect the
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NASA Astrophysics Data System (ADS)
Sakkas, Vassilis; Lagios, Evangelos
2017-03-01
The implications of the earthquakes that took place in the central Ionian Islands in 2014 (Cephalonia, M w6.1, M w5.9) and 2015 (Lefkas, M w6.4) are described based on repeat measurements of the local GPS networks in Cephalonia and Ithaca, and the available continuous GPS stations in the broader area. The Lefkas earthquake occurred on a branch of the Cephalonia Transform Fault, affecting Cephalonia with SE displacements gradually decreasing from north ( 100 mm) to south ( 10 mm). This earthquake revealed a near N-S dislocation boundary separating Paliki Peninsula in western Cephalonia from the rest of the island, as well as another NW-SE trending fault that separates kinematically the northern and southern parts of Paliki. Strain field calculations during the interseismic period (2014-2015) indicate compression between Ithaca and Cephalonia, while extension appears during the following co-seismic period (2015-2016) including the 2015 Lefkas earthquake. Additional tectonically active zones with differential kinematic characteristics were also identified locally.
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Earthquakes, November-December 1991
Person, W.J.
1992-01-01
There were three major earthquakes (7.0-7.9) during the last two months of the year: a magntidue 7.0 on November 19 in Columbia, a magnitude 7.4 in the Kuril Islands on December 22, and a magnitude 7.1 in the South Sandwich Islands on December 27. Earthquake-related deaths were reported in Colombia, Yemen, and Iran. there were no significant earthquakes in the United States during this reporting period.
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NASA Astrophysics Data System (ADS)
Lough, A. C.; Roman, D. C.; Haney, M. M.
2015-12-01
Deep long period (DLP) earthquakes are commonly observed in volcanic settings such as the Aleutian Arc in Alaska. DLPs are poorly understood but are thought to be associated with movements of fluids, such as magma or hydrothermal fluids, deep in the volcanic plumbing system. These events have been recognized for several decades but few studies have gone beyond their identification and location. All long period events are more difficult to identify and locate than volcano-tectonic (VT) earthquakes because traditional detection schemes focus on high frequency (short period) energy. In addition, DLPs present analytical challenges because they tend to be emergent and so it is difficult to accurately pick the onset of arriving body waves. We now expect to find DLPs at most volcanic centers, the challenge lies in identification and location. We aim to reduce the element of human error in location by applying back projection to better constrain the depth and horizontal position of these events. Power et al. (2004) provided the first compilation of DLP activity in the Aleutian Arc. This study focuses on the reanalysis of 162 cataloged DLPs beneath 11 volcanoes in the Aleutian arc (we expect to ultimately identify and reanalyze more DLPs). We are currently adapting the approach of Haney (2014) for volcanic tremor to use back projection over a 4D grid to determine position and origin time of DLPs. This method holds great potential in that it will allow automated, high-accuracy picking of arrival times and could reduce the number of arrival time picks necessary for traditional location schemes to well constrain event origins. Back projection can also calculate a relative focal mechanism (difficult with traditional methods due to the emergent nature of DLPs) allowing the first in depth analysis of source properties. Our event catalog (spanning over 25 years and volcanoes) is one of the longest and largest and enables us to investigate spatial and temporal variation in DLPs.
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Microbial consortia of gorgonian corals from the Aleutian islands
Gray, Michael A.; Stone, R.P.; McLaughlin, M.R.; Kellogg, C.A.
2011-01-01
Gorgonians make up the majority of corals in the Aleutian archipelago and provide critical fish habitat in areas of economically important fisheries. The microbial ecology of the deep-sea gorgonian corals Paragorgea arborea, Plumarella superba, and Cryogorgia koolsae was examined with culture-based and 16S rRNA gene-based techniques. Six coral colonies (two per species) were collected. Samples from all corals were cultured, and clone libraries were constructed from P. superba and C. koolsae. Cultured bacteria were dominated by the Gammaproteobacteria, especially Vibrionaceae, with other phyla comprising <6% of the isolates. The clone libraries showed dramatically different bacterial communities between corals of the same species collected at different sites, with no clear pattern of conserved bacterial consortia. Two of the clone libraries (one from each coral species) were dominated by Tenericutes, with Alphaproteobacteria dominating the remaining sequences. The other libraries were more diverse and had a more even distribution of bacterial phyla, showing more similarity between genera than within coral species. Here we report the first microbiological characterization of P. arborea, P. superba, and C. koolsae. FEMS Microbiology Ecology ?? 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. No claim to original US government works.
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Crustal Deformation and the Seismic Cycle across the Kodiak Islands, Alaska
NASA Technical Reports Server (NTRS)
Sauber, Jeanne; Carver, G.; Cohen, Steven C.; King, Robert
2004-01-01
The Kodiak Islands are located approximately 130 to 250 km from the Alaska-Aleutian Trench where the Pacific plate is underthrusting the North American plate at a rate of about 57 mm/yr. The southern extent of the 1964 Prince William Sound (${M-w}$ = 9.2) earthquake rupture occurred offshore and beneath the eastern portion of the Kodiak Islands. Here we report GPS results (1993-2001) from northern Kodiak Island that span the transition between the 1964 uplift region along the eastern coast and the region of coseismic subsidence further inland. The horizontal velocity vectors range from 22.9 $\\pm$ 2.2 mm/yr at N26.3$\\deg$W $\\pm$ 2.5$\\deg$, about 150 km from the trench, to 5.9 $\\pm$ 1.3 mm/yr at N65.9$\\deg$W $\\pm$ 6.6$\\deg$, about 190 km from the trench. Near the northeastern coast of Kodiak the velocity vector above the shallow, locked main thrust zone is between the orientation of PCFC-NOAM plate motion (N22$/deg$W) and the trench-normal (N3O$\\deg$W). Further west, our geodetic results suggest the accumulation of shear strain that will be released eventually as left-lateral motion on upper plate faults such as the Kodiak Island fault. These results are consistent with the hypothesis that the difference between the Pacific-North American plate motion and the orientation of the down going slab would lead to 4-8 mm/yr of left-lateral slip. Short-term geodetic uplift rates range from 2 - 14 mm/yr, with the maximum uplift located near the axis of maximum subsidence during the 1964 earthquake. We evaluated alternate interseismic models for Kodiak to test the importance of various mechanisms responsible for crustal deformation rates. These models are based on the plate interface slip history inferred from earlier modeling of coseismic and post-seismic geodetic results. The horizontal (trench perpendicular) and vertical deformation rates across Kodiak are consistent with a model that includes the viscoelastic response to : (1) a downgoing Pacific plate interface
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A dynamic model for slab development associated with the 2015 Mw 7.9 Bonin Islands deep earthquak
NASA Astrophysics Data System (ADS)
Zhan, Z.; Yang, T.; Gurnis, M.
2016-12-01
The 680 km deep May 30, 2015 Mw 7.9 Bonin Islands earthquake is isolated from the nearest earthquakes by more than 150 km. The geodynamic context leading to this isolated deep event is unclear. Tomographic models and seismicity indicate that the morphology of the west-dipping Pacific slab changes rapidly along the strike of the Izu-Bonin-Mariana trench. To the north, the Izu-Bonin section of the Pacific slab lies horizontally above the 660 km discontinuity and extends more than 500 km westward. Several degrees south, the Mariana section dips vertically and penetrates directly into the lower mantle. The observed slab morphology is consistent with plate reconstructions suggesting that the northern section of the IBM trench retreated rapidly since the late Eocene while the southern section of the IBM trench was relatively stable during the same period. We suggest that the location of the isolated 2015 Bonin Islands deep earthquake can be explained by the buckling of the Pacific slab beneath the Bonin Islands. We use geodynamic models to investigate the slab morphology, temperature and stress regimes under different trench motion histories. Models confirm previous results that the slab often lies horizontally within the transition zone when the trench retreats, but buckles when the trench position becomes fixed with respect to the lower mantle. We show that a slab-buckling model is consistent with the observed deep earthquake P-axis directions (assumed to be the axis of principal compressional stress) regionally. The influences of various physical parameters on slab morphology, temperature and stress regime are investigated. In the models investigated, the horizontal width of the buckled slab is no more than 400 km.
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-10-01
...NMFS publishes regulations to implement Amendment 97 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP). Amendment 97 allows the owner of a trawl catcher/processor vessel authorized to participate in the Amendment 80 catch share program to replace that vessel with a vessel that meets certain requirements. This action establishes the regulatory process for replacement of vessels in the Amendment 80 fleet and the requirements for Amendment 80 replacement vessels, such as a limit on the overall length of a replacement vessel, a prohibition on the use of an AFA vessel as a replacement vessel, measures to prevent a replaced vessel from participating in Federal groundfish fisheries off Alaska that are not Amendment 80 fisheries, and measures that extend specific catch limits (known as Amendment 80 sideboards) to a replacement vessel. This action is necessary to promote safety-at-sea by allowing Amendment 80 vessel owners to replace their vessels for any reason at any time and by requiring replacement vessels to meet certain U.S. Coast Guard vessel safety standards, and to improve the retention and utilization of groundfish catch by these vessels by facilitating an increase in the processing capabilities of the fleet. This action is intended to promote the goals and objectives of the Magnuson-Stevens Fishery Conservation and Management Act, the FMP, and other applicable laws.
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Person, W.J.
1983-01-01
During this reporting period, there were three major (7.0-7.9) earthquakes all in unpopulated areas. The quakes occurred north of Macquarie Island on July 7, in the Santa Cruz Islands on August 5, and south of Panama on August 19. In the United Stats, a number of earthquakes occurred, but no damage was reported.
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NASA Astrophysics Data System (ADS)
Barama, L.; Newman, A. V.; Convers, J.
2016-12-01
The Solomon Islands are heavily affected by frequent and destructive tsunamigenic earthquakes. Many of these earthquakes have rupture very near the trench, a feature normally associated with slow-source "tsunami earthquakes" as defined by Kanamori [Kanamori, PEPI 1972]. However, prior evaluation of energetic behavior of some recent larger tsunamigenic earthquakes have revealed little evidence for such a slow nature [Convers and Newman, JGR 2011; Newman et al., GJI 2011]. In this study, we evaluate all regional earthquakes surrounding the Solomon Islands with moment magnitude greater than 5.5 since 1976. We will use a newly developed methodology for more robustly characterizing the rupture duration along with seismic energy radiation from teleseismically located broad-band seismic stations, called the Time-Averaged Cumulative Energy Rate (TACER) [Convers and Newman, GRL 2013], for evaluating the slow-source nature. This methodology uniquely identifies the slow-rupture often associated with tsunami earthquakes due to the contrasting nature of the up-to order-of-magnitude negative deviation in energy and up-to three-fold excess in rupture duration in such events for a particular seismic moment [Newman et al., GRL 2011]. A ubiquitous slow-nature in this region would be surprising due to the spatial variance of the subducting features, and lack of any known slow-source tsunami earthquakes in the past century. It is more likely this region is not solely characterized by such slow-nature events, but instead have rupture energies comparable to what we see for events elsewhere and occuring in deeper segments of the megathrust interface. The most recent tsunamigenic earthquakes in the Solomon islands include the 2007 April 1, MW 8.1, 2010 January 3, MW 7.1 and 2013 February 6, MW 7.9 events, that display higher radiated seismic energies and shorter rupture durations than expected in recognized tsunami earthquakes that are observed at higher magnitudes (MW >7.5) elsewhere
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NASA Astrophysics Data System (ADS)
Miller, H.; Lopez, T. M.; Fischer, T. P.; Schrenk, M. O.
2016-12-01
Subduction-related processes, including the movement and alteration of carbon compounds, are an important component of global geochemical cycles. Actively degassing volcanoes of the Aleutian Island arc offer interesting opportunities to not only characterize the composition and abundance of volatiles, but also to identify the origin of the discharging gases (e.g. mantle, organic matter, or carbonates). Taking this approach a step further, microbial activities in and around volcanic fumarole areas may impact the composition and flux of reduced volcanic gases, either through their modification or their assimilation into fixed biomass. Microbiological studies of these systems can be used to develop predictive models to complement those based upon geochemical data while providing greater understanding of the causal relationships between microbial populations and their environment, and ultimately refine estimates of volcanic outgassing. Coupled fumarole soil and gas samples were collected from several Aleutian Island volcanoes in 2015 (Gareloi, Kanaga, Kiska, Little Sitkin) and 2016 (Okmok, Resheschnoi). DNA was extracted from the soil and used to describe microbial community composition, while gas samples were analyzed through chromatography and mass spectrometry. Preliminary data suggests a relationship between the abundance of specific groups of prokaryotes known to metabolize reduced gases, such as sulfur-oxidizers and methanotrophs, and the abundances of the degassing volatiles, including sulfur dioxide and methane. Ongoing studies aimed at investigating the relationship between the genomic composition of the fumarolic microbial community and the physical and chemical properties of the soil (i.e. mineralogy, bulk geochemistry, nutrient concentration, gas flux, and environmental measurements) are underway. These data will be used to evaluate the potential for microbial communities to remove volcanic carbon and store it as biomass, or to modify the volatile carbon
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Microbial consortia of gorgonian corals from the Aleutian islands.
Gray, Michael A; Stone, Robert P; McLaughlin, Molly R; Kellogg, Christina A
2011-04-01
Gorgonians make up the majority of corals in the Aleutian archipelago and provide critical fish habitat in areas of economically important fisheries. The microbial ecology of the deep-sea gorgonian corals Paragorgea arborea, Plumarella superba, and Cryogorgia koolsae was examined with culture-based and 16S rRNA gene-based techniques. Six coral colonies (two per species) were collected. Samples from all corals were cultured, and clone libraries were constructed from P. superba and C. koolsae. Cultured bacteria were dominated by the Gammaproteobacteria, especially Vibrionaceae, with other phyla comprising <6% of the isolates. The clone libraries showed dramatically different bacterial communities between corals of the same species collected at different sites, with no clear pattern of conserved bacterial consortia. Two of the clone libraries (one from each coral species) were dominated by Tenericutes, with Alphaproteobacteria dominating the remaining sequences. The other libraries were more diverse and had a more even distribution of bacterial phyla, showing more similarity between genera than within coral species. Here we report the first microbiological characterization of P. arborea, P. superba, and C. koolsae. FEMS Microbiology Ecology © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. No claim to original US government works.
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Transient evolution of plate coupling after the giant 1960 Chile earthquake at Guafo Island
NASA Astrophysics Data System (ADS)
Melnick, Daniel; Moreno, Marcos; Li, Shaoyang; Cisternas, Marco; Baez, Juan Carlos; Wesson, Robert; Nelson, Alan; Bevis, Michael
2015-04-01
In subduction zones, elastic energy is slowly accumulated during decades to centuries and suddenly released by great earthquakes. The moment deficit-the energy available for future earthquakes-is commonly inferred by extrapolating modern plate coupling rates estimated from space geodesy back to the last great earthquake's date. However, the evolution of plate coupling between two great earthquakes integrating the moment deficit has been difficult to quantify due to limited geodetic data at decadal time scale, or longer. We infer the evolution of plate coupling below Guafo Island in the south Chilean subduction zone since the 1960 earthquake (Mw=9.5) using photographic and satellite images dating back to 1974, a campaign GPS benchmark installed in 1994, and a permanent GPS station installed in 2009. Guafo was uplifted 3.6-4.0 m in 1960 and has been subsiding since at least the late 1970s. A peaty soil that rapidly developed on the bedrock abrasion platforms that emerged in 1960 has been continuously eroding by relative sea-level rise resulting mostly from land subsidence. This process has resulted in continuous retreat of beach berms overlying bedrock platforms. We mapped such shoreline features in photographic and satellite images through time and, using the measured slope of the underlying platform, inferred relative sea-level changes between image pairs. Land-level changes were subsequently estimated by subtracting a mean absolute sea-level rise rate of 1.7 +/- 0.1 mm/yr calculated from satellite altimetry between 1992-2014. The combined time series shows a steady acceleration in the subsidence rate of Guafo Island from 6-8 mm/yr in the late 1970s to 20 mm/yr at present estimated from the permanent GPS. Using a viscoelastic numerical model and constraints for the seismogenic zone width from published thermal models we infer that interseismic plate coupling increased continuously from ~30% in the late 1970s to ~90% at present. Plate coupling apparently needed more
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NASA Astrophysics Data System (ADS)
Takemura, Shunsuke; Saito, Tatsuhiko; Shiomi, Katsuhiko
2017-03-01
An M 6.8 ( Mw 6.5) deep-focus earthquake occurred beneath the Bonin Islands at 21:18 (JST) on June 23, 2015. Observed high-frequency (>1 Hz) seismograms across Japan, which contain several sets of P- and S-wave arrivals for the 10 min after the origin time, indicate that moderate-to-large earthquakes occurred sequentially around Japan. Snapshots of the seismic energy propagation illustrate that after one deep-focus earthquake occurred beneath the Sea of Japan, two deep-focus earthquakes occurred sequentially after the first ( Mw 6.5) event beneath the Bonin Islands in the next 4 min. The United States Geological Survey catalog includes three Bonin deep-focus earthquakes with similar hypocenter locations, but their estimated magnitudes are inconsistent with seismograms from across Japan. The maximum-amplitude patterns of the latter two earthquakes were similar to that of the first Bonin earthquake, which indicates similar locations and mechanisms. Furthermore, based on the ratios of the S-wave amplitudes to that of the first event, the magnitudes of the latter events are estimated as M 6.5 ± 0.02 and M 5.8 ± 0.02, respectively. Three magnitude-6-class earthquakes occurred sequentially within 4 min in the Pacific slab at 480 km depth, where complex heterogeneities exist within the slab.[Figure not available: see fulltext.
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Earthquakes, September-October 1986
Person, W.J.
1987-01-01
There was one great earthquake (8.0 and above) during this reporting period in the South Pacific in the Kermadec Islands. There were no major earthquakes (7.0-7.9) but earthquake-related deaths were reported in Greece and in El Salvador. There were no destrcutive earthquakes in the United States.
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Preliminary Volcano-Hazard Assessment for Gareloi Volcano, Gareloi Island, Alaska
Coombs, Michelle L.; McGimsey, Robert G.; Browne, Brandon L.
2008-01-01
Gareloi Volcano (178.794 degrees W and 51.790 degrees N) is located on Gareloi Island in the Delarof Islands group of the Aleutian Islands, about 2,000 kilometers west-southwest of Anchorage and about 150 kilometers west of Adak, the westernmost community in Alaska. This small (about 8x10 kilometer) volcano has been one of the most active in the Aleutians since its discovery by the Bering expedition in the 1740s, though because of its remote location, observations have been scant and many smaller eruptions may have gone unrecorded. Eruptions of Gareloi commonly produce ash clouds and lava flows. Scars on the flanks of the volcano and debris-avalanche deposits on the adjacent seafloor indicate that the volcano has produced large landslides in the past, possibly causing tsunamis. Such events are infrequent, occurring at most every few thousand years. The primary hazard from Gareloi is airborne clouds of ash that could affect aircraft. In this report, we summarize and describe the major volcanic hazards associated with Gareloi.
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Person, Waverly J.
1992-01-01
The months of May and June were very active in terms of earthquake occurrence. Six major earthquakes (7.0
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Ricca, Mark A.; Miles, A. Keith; Anthony, Robert G.
2008-01-01
Persistent organochlorine compounds and mercury (Hg) have been detected in numerous coastal organisms of the Aleutian archipelago of Alaska, yet sources of these contaminants are unclear. We collected glaucous-winged gulls, northern fulmars, and tufted puffins along a natural longitudinal gradient across the western and central Aleutian Islands (Buldir, Kiska, Amchitka, Adak), and an additional 8 seabird species representing different foraging and migratory guilds from Buldir Island to evaluate: 1) point source input from former military installations, 2) westward increases in contaminant concentrations suggestive of distant source input, and 3) effects of trophic status (δ15N) and carbon source (δ13C) on contaminant accumulation. Concentrations of Σ polychlorinated biphenyls (PCBs) and most chlorinated pesticides in glaucous-winged gulls consistently exhibited a ‘U’-shaped pattern of high levels at Buldir and the east side of Adak and low levels at Kiska and Amchitka. In contrast, concentrations of Σ PCBs and chlorinated pesticides in northern fulmars and tufted puffins did not differ among islands. Hg concentrations increased westward in glaucous-winged gulls and were highest in northern fulmars from Buldir. Among species collected only at Buldir, Hg was notably elevated in pelagic cormorants, and relatively high Σ PCBs were detected in black-legged kittiwakes. Concentrations of Σ PCBs, dichlorodiphenyldichloroethylene (p,p′ DDE), and Hg were positively correlated with δ15N across all seabird species, indicating biomagnification across trophic levels. The east side of Adak Island (a former military installation) was a likely point source of Σ PCBs and p,p′ DDE, particularly in glaucous-winged gulls. In contrast, elevated levels of these contaminants and Hg, along with PCB congener and chlorinated pesticide compositional patterns detected at Buldir Island indicated exposure from distant sources influenced by a combination of atmospheric
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USDA-ARS?s Scientific Manuscript database
Burned stone slabs, historically called griddlestones, were recovered from Components 1 (2390-2590 RCYPB) and 2 (170-415 RCYBP) at archaeological site ADK-011 on Adak Island, Aleutian Islands, Alaska. The griddlestones show evidence of fire exposure and have a dark, often greasy, matrix of decompose...
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NASA Astrophysics Data System (ADS)
Mooney, W. D.; Kayal, J.
2007-05-01
The December 26, 2004 Sumatra-Andaman earthquake (MW 9.3) is the fourth largest event (M>9.0) in the world during the last 100 years. It occurred by thrust faulting on the interplate thrust zone of the subducting India plate and overriding Burma platelet. The main shock rupture, ~1300 km long and ~200 km wide, propagated from north of Sumatra to Andaman - Nicobar Islands; the slow rupture generated Tsunami which killed about 300,000 people. The epicenter of the earthquake is located at 3.90N and 94.260E with a focal depth at 28 km (USGS). This mega seismic event triggered giant tsunamis that devastated the coastal regions of Indonesia, Malaysia, Thailand, Sri Lanka, India, Maldives and even the east coast of Africa. The impact of the tsunami was quite severe in India, in the coasts of Andaman and Nicobar Islands. The Air-base in the Car- Nicobar island was totally devastated by the tsunami and killed about 200 people. Macroseismic survey was carried out by different teams of GSI in North Andaman, Middle Andaman, South Andaman, Havelock Hut Bay and also in the Nicobar Islands. A maximum intensity VIII was recorded in the Andaman Islands. The mega thrust event was followed by an intense aftershock activity spreading over an area extending between 30-140N along the Andaman - Nicobar - Sumatra Island arc region. The aftershocks are distributed northwards from the epicenter of the main shock suggesting a unilateral rupture propagation. The aftershock (M >4.5) area covers a length of about 1300 km and a width of about 200 km, in a 'banana' shape. The national network (IMD) recorded almost all aftershocks M >5.0; about 350 were recorded till 31.01.2005. The Geological Survey of India (GSI) deployed six temporary seismograph stations in the Andaman and Nicobar Islands and also in Havelok and Narkunda (volcanic) islands. About 20,000 aftershocks (M >3.0) were recorded until end of March, 2005. About 1000 aftershocks (M >3.0) located by the GSI network until January 31, 2005
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Buldir Depression - A Late Tertiary graben on the Aleutian Ridge, Alaska
Marlow, M. S.; Scholl, D. W.; Buffington, E.C.; Boyce, R.E.; Alpha, T.R.; Smith, P.J.; Shipek, C.J.
1970-01-01
Buldir Depression is a large, rectilinear basin that lies on the northern edge of the Aleutian Ridge and is aligned with the arcuate chain of active volcanoes on the ridge crest. The depression appears to be a volcanic-tectonic feature, which began to form in Late Tertiary time and which is still forming. It is a graben formed by extensional rifting and accompanied by contemporaneous volcanism on the Aleutian Ridge. Subsidence rates for the depression are estimated at 20-70 cm/1,000 years. Sediments in the depression are 300 m thick and are probably pelagic and turbidite deposits of Pleistocene age. The turbidites were apparently derived from the plateau area of the Aleutian Ridge surrounding the depression. Older sediments on the northern slope of the Aleutian Ridge have a maximum thickness of 550 m and are deformed and slumped toward the Bering Sea. These sediments are postulated to overlie a mid-flank terrace on the northern Aleutian Ridge that titled to the north during the formation of Buldir Depression. ?? 1970.
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NASA Astrophysics Data System (ADS)
Hernandez, F. J.; Lopez, A. M.; Vanacore, E. A.
2017-12-01
The presence of earthquake swarms and clusters in the north and northeast of the island of Puerto Rico in the northeastern Caribbean have been recorded by the Puerto Rico Seismic Network (PRSN) since it started operations in 1974. Although clusters in the Puerto Rico-Virgin Island (PRVI) block have been observed for over forty years, the nature of their enigmatic occurrence is still poorly understood. In this study, the entire seismic catalog of the PRSN, of approximately 31,000 seismic events, has been limited to a sub-set of 18,000 events located all along north of Puerto Rico in an effort to characterize and understand the underlying mechanism of these clusters. This research uses two de-clustering methods to identify cluster events in the PRVI block. The first method, known as Model Independent Stochastic Declustering (MISD), filters the catalog sub-set into cluster and background seismic events, while the second method uses a spatio-temporal algorithm applied to the catalog in order to link the separate seismic events into clusters. After using these two methods, identified clusters were classified into either earthquake swarms or seismic sequences. Once identified, each cluster was analyzed to identify correlations against other clusters in their geographic region. Results from this research seek to : (1) unravel their earthquake clustering behavior through the use of different statistical methods and (2) better understand the mechanism for these clustering of earthquakes. Preliminary results have allowed to identify and classify 128 clusters categorized in 11 distinctive regions based on their centers, and their spatio-temporal distribution have been used to determine intra- and interplate dynamics.
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A Bayesian inversion for slip distribution of 1 Apr 2007 Mw8.1 Solomon Islands Earthquake
NASA Astrophysics Data System (ADS)
Chen, T.; Luo, H.
2013-12-01
On 1 Apr 2007 the megathrust Mw8.1 Solomon Islands earthquake occurred in the southeast pacific along the New Britain subduction zone. 102 vertical displacement measurements over the southeastern end of the rupture zone from two field surveys after this event provide a unique constraint for slip distribution inversion. In conventional inversion method (such as bounded variable least squares) the smoothing parameter that determines the relative weight placed on fitting the data versus smoothing the slip distribution is often subjectively selected at the bend of the trade-off curve. Here a fully probabilistic inversion method[Fukuda,2008] is applied to estimate distributed slip and smoothing parameter objectively. The joint posterior probability density function of distributed slip and the smoothing parameter is formulated under a Bayesian framework and sampled with Markov chain Monte Carlo method. We estimate the spatial distribution of dip slip associated with the 1 Apr 2007 Solomon Islands earthquake with this method. Early results show a shallower dip angle than previous study and highly variable dip slip both along-strike and down-dip.
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High-speed rupture during the initiation of the 2015 Bonin Islands deep earthquake
NASA Astrophysics Data System (ADS)
Zhan, Z.; Ye, L.; Shearer, P. M.; Lay, T.; Kanamori, H.
2015-12-01
Among the long-standing questions on how deep earthquakes rupture, the nucleation phase of large deep events is one of the most puzzling parts. Resolving the rupture properties of the initiation phase is difficult to achieve with far-field data because of the need for accurate corrections for structural effects on the waveforms (e.g., attenuation, scattering, and site effects) and alignment errors. Here, taking the 2015 Mw 7.9 Bonin Islands earthquake (depth = 678 km) as an example, we jointly invert its far-field P waves at multiple stations for the average rupture speed during the first second of the event. We use waveforms from a closely located aftershock as empirical Green's functions, and correct for possible differences in focal mechanisms and waveform misalignments with an iterative approach. We find that the average initial rupture speed is over 5 km/s, significantly higher than the average rupture speed of 3 km/s later in the event. This contrast suggests that rupture speeds of deep earthquakes can be highly variable during individual events and may define different stages of rupture, potentially with different mechanisms.
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NASA Astrophysics Data System (ADS)
Rubinstein, Justin L.; Gomberg, Joan; Vidale, John E.; Wech, Aaron G.; Kao, Honn; Creager, Kenneth C.; Rogers, Garry
2009-02-01
We explore the physical conditions that enable triggering of nonvolcanic tremor and earthquakes by considering local seismic activity on Vancouver Island, British Columbia during and immediately after the arrival of large-amplitude seismic waves from 30 teleseismic and 17 regional or local earthquakes. We identify tremor triggered by four of the teleseismic earthquakes. The close temporal and spatial proximity of triggered tremor to ambient tremor and aseismic slip indicates that when a fault is close to or undergoing failure, it is particularly susceptible to triggering of further events. The amplitude of the triggering waves also influences the likelihood of triggering both tremor and earthquakes such that large amplitude waves triggered tremor in the absence of detectable aseismic slip or ambient tremor. Tremor and energy radiated from regional/local earthquakes share the same frequency passband so that tremor cannot be identified during these smaller, more frequent events. We confidently identify triggered local earthquakes following only one teleseism, that with the largest amplitude, and four regional or local events that generated vigorous aftershock sequences in their immediate vicinity. Earthquakes tend to be triggered in regions different from tremor and with high ambient seismicity rates. We also note an interesting possible correlation between large teleseismic events and episodic tremor and slip (ETS) episodes, whereby ETS events that are "late" and have built up more stress than normal are susceptible to triggering by the slight nudge of the shaking from a large, distant event, while ETS events that are "early" or "on time" are not.
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An isolated population of small Canada geese on Kaliktagik Island, Alaska
Hatch, Scott A.; Hatch, Martha A.
1983-01-01
Recently we discovered that a small form of the Canada Goose Branta canadensis breeds on Kaliktagik Island, one of the Semidi Islands, about 80 km south of the Alaska Peninsula near longitude 157°W (Figure 1). The unexpected occurrence of geese on this oceanic island and the possibility that they are closely allied with the endangered Aleutian race of Canada Geese B. c. leucopareia prompt this summary of observations made between 1977 and 1981, in the course of field studies on seabirds of the area.
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NASA Astrophysics Data System (ADS)
Zelenak, G.; Key, K.; Bennington, N. L.; Bedrosian, P.
2015-12-01
Understanding the factors controlling the release of volatiles from the downgoing slab, the subsequent generation of melt in the overlying mantle wedge, the migration of melt to the crust, and its evolution and emplacement within the crust are important for advancing our understanding of arc magmatism and crustal genesis. Because melt and aqueous fluids are a few orders of magnitude more electrically conductive than unmelted peridotite, the conductivity-mapping magnetotelluric (MT) method is well-suited to imaging fluids and melt beneath arc volcanoes. Here we present conductivity results from an amphibious MT profile crossing Okmok volcano in the central Aleutian arc. The Aleutian arc is one of the most volcanically active regions in North America, making it an ideal location for studying arc magnetism. Okmok volcano, located on the northeastern portion of Umnak Island, is among the most active volcanoes in the Aleutian chain. In addition to two caldera-forming events in the Holocene, numerous eruptions in the past century indicate a robust magmatic supply. Previous coarse resolution seismic studies have inferred a crustal magma reservoir. In order to investigate the role fluids play in melting the mantle wedge, how melts ascend through the corner flow regime of the mantle wedge, how melt migrates and is stored within the upper mantle and crust, and how this impacts explosive caldera forming eruptions, we carried out an amphibious geophysical survey across the arc in June-July 2015. Twenty-nine onshore MT stations and 10 offshore stations were collected in a 3D array covering Okmok, and 43 additional offshore MT stations completed a 300 km amphibious profile starting at the trench, crossing the forearc, arc and backarc. Thirteen onshore passive seismic stations were also installed and will remain in place for one year to supplement the twelve permanent stations on the island. Data collected by this project will be used to map seismic velocity and electrical
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Repeating coupled earthquakes at Shishaldin Volcano, Alaska
Caplan-Auerbach, J.; Petersen, T.
2005-01-01
Since it last erupted in 1999, Shishaldin Volcano, Aleutian Islands, Alaska, has produced hundreds to thousands of long-period (1-2 Hz; LP) earthquakes every day with no other sign of volcanic unrest. In 2002, the earthquakes also exhibited a short-period (4-7 Hz; SP) signal occurring between 3 and 15 s before the LP phase. Although the SP phase contains higher frequencies than the LP phase, its spectral content is still well below that expected of brittle failure events. The SP phase was never observed without the LP phase, although LP events continued to occur in the absence of the precursory signal. The two-phased events are termed "coupled events", reflecting a triggered relationship between two discrete event types. Both phases are highly repetitive in time series, suggestive of stable, non-destructive sources. Waveform cross-correlation and spectral coherence are used to extract waveforms from the continuous record and determine precise P-wave arrivals for the SP phase. Although depths are poorly constrained, the SP phase is believed to lie at shallow (<4 km) depths just west of Shishaldin's summit. The variable timing between the SP and LP arrivals indicates that the trigger mechanism between the phases itself moves at variable speeds. A model is proposed in which the SP phase results from fluid moving within the conduit, possibly around an obstruction and the LP phase results from the coalescence of a shallow gas bubble. The variable timing is attributed to changes in gas content within the conduit. The destruction of the conduit obstacle on November 21, 2002 resulted in the abrupt disappearance of the SP phase.
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GLORIA side-scan imagery of Aleutian basin, Bering Sea slope and Abyssal plain
DOE Office of Scientific and Technical Information (OSTI.GOV)
Carlson, P.R.; Cooper, A.K.; Gardner, J.V.
1987-05-01
During July-September 1986, about 700,000 km/sup 2/ of continental slope and abyssal plain of the Aleutian basin, Bering Sea, were insonified with GLORIA (Geological Long Range Inclined Asdic) side-scane sonar. A sonar mosaic displays prominent geomorphic features including the massive submarine canyons of the Beringian and the northern Aleutian Ridge slopes and shows well-defined sediment patterns including large deep-sea channels and fan systems on the Aleutian basin abyssal plain. Dominant erosional and sediment transport processes on both the Beringian and the Aleutian Ridge slopes include varieties of mass movement that range from small debris flows and slides to massive slidesmore » and slumps of blocks measuring kilometers in dimension. Sediment-flow patterns that appear to be formed by sheet flow rather than channelized flow extend basinward from the numerous canyons and gullies that incise the slopes of the Beringian margin and of Bowers Ridge and some places along the Aleutian Ridge. These Beringian and Bowers canyon sediment sources, however, appear to have contributed less modern sediment to the Aleutian basin than the large, well-defined channel systems that emanate from Bering, Umnak, and Amchitka submarine canyons and extend for several hundred kilometers across the abyssal plain. This GLORIA imagery emphasizes the important contribution of the Aleutian Ridge to modern sedimentation in the deep Bering Sea.« less
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Yehle, Lynn A.
1977-01-01
A program to study the engineering geology of most larger Alaska coastal communities and to evaluate their earthquake and other geologic hazards was started following the 1964 Alaska earthquake; this report about the Metlakatla area, Annette Island, is a product of that program. Field-study methods were of a reconnaissance nature, and thus the interpretations in the report are tentative. Landscape of the Metlakatla Peninsula, on which the city of Metlakatla is located, is characterized by a muskeg-covered terrane of very low relief. In contrast, most of the rest of Annette Island is composed of mountainous terrane with steep valleys and numerous lakes. During the Pleistocene Epoch the Metlakatla area was presumably covered by ice several times; glaciers smoothed the present Metlakatla Peninsula and deeply eroded valleys on the rest. of Annette Island. The last major deglaciation was completed probably before 10,000 years ago. Rebound of the earth's crust, believed to be related to glacial melting, has caused land emergence at Metlakatla of at least 50 ft (15 m) and probably more than 200 ft (61 m) relative to present sea level. Bedrock in the Metlakatla area is composed chiefly of hard metamorphic rocks: greenschist and greenstone with minor hornfels and schist. Strike and dip of beds are generally variable and minor offsets are common. Bedrock is of late Paleozoic to early Mesozoic age. Six types of surficial geologic materials of Quaternary age were recognized: firm diamicton, emerged shore, modern shore and delta, and alluvial deposits, very soft muskeg and other organic deposits, and firm to soft artificial fill. A combination map unit is composed of bedrock or diamicton. Geologic structure in southeastern Alaska is complex because, since at least early Paleozoic time, there have been several cycles of tectonic deformation that affected different parts of the region. Southeastern Alaska is transected by numerous faults and possible faults that attest to major
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Lu, Z.; Wicks, C.; Power, J.A.; Dzurisin, D.
2000-01-01
In March 1996 an intense swarm of volcano-tectonic earthquakes (???3000 felt by local residents, Mmax = 5.1, cumulative moment of 2.7 ??1018 N m) beneath Akutan Island in the Aleutian volcanic arc, Alaska, produced extensive ground cracks but no eruption of Akutan volcano. Synthetic aperture radar interferograms that span the time of the swarm reveal complex island-wide deformation: the western part of the island including Akutan volcano moved upward, while the eastern part moved downward. The axis of the deformation approximately aligns with new ground cracks on the western part of the island and with Holocene normal faults that were reactivated during the swarm on the eastern part of the island. The axis is also roughly parallel to the direction of greatest compressional stress in the region. No ground movements greater than 2.83 cm were observed outside the volcano's summit caldera for periods of 4 years before or 2 years after the swarm. We modeled the deformation primarily as the emplacement of a shallow, east-west trending, north dipping dike plus inflation of a deep, Mogi-type magma body beneath the volcano. The pattern of subsidence on the eastern part of the island is poorly constrained. It might have been produced by extensional tectonic strain that both reactivated preexisting faults on the eastern part of the island and facilitated magma movement beneath the western part. Alternatively, magma intrusion beneath the volcano might have been the cause of extension and subsidence in the eastern part of the island. We attribute localized subsidence in an area of active fumaroles within the Akutan caldera, by as much as 10 cm during 1992-1993 and 1996-1998, to fluid withdrawal or depressurization of the shallow hydrothermal system. Copyright 2000 by the American Geophysical Union.
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Quaternary uplift and tilting of Amorgos Island (southern Aegean) and the 1956 earthquake
NASA Astrophysics Data System (ADS)
Stiros, Stathis C.; Marangou, Lila; Arnold, Maurice
1994-12-01
Uplifted Pleistocene marine sediments, submerged ancient ruins and raised beaches confirm earlier views that the asymmetry of the relief of Amorgos Island (southern Aegean) testifies to a fault-bounded block uplifted and tilted along a SW-NE trending horizontal axis; the uplifted coast corresponds to a high-gradient slope controlled by an oblique master normal fault. Furthermore, geomorphic and biological evidence, radiometric data and comparison of aerial photographs indicates that the 1956 earthquake (Ms = 7.4) uplifted the footwall of this normal fault by about 30 cm.
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NASA Astrophysics Data System (ADS)
Graham, S. E.; Rodriguez, M.; Rogers, R. D.; Strauch, W.; Hernandez, D.; Demets, C.
2010-12-01
The May 28, 2009 M=7.3 Swan Islands earthquake off the north coast of Honduras caused significant damage in the northern part of the country, including seven deaths. This event, the largest in the region for several decades, ruptured the offshore continuation of the Motagua-Polochic fault system, whose 1976 earthquake (located several hundred kilometers to the southwest of the 2009 epicenter) caused more than 23,000 deaths in Central America and left homeless 20% of Guatemala’s population. We use elastic half-space modeling of coseismic offsets measured at 39 GPS stations in Honduras, El Salvador, and Guatemala to better understand the slip source of the recent Swan Islands earthquake. Measured offsets range from .32 meters at a campaign site near the Motagua fault in northern Honduras to 4 millimeters at five continuous sites in El Salvador. Coulomb stress calculations based on the estimated distribution of coseismic slip will be presented and compared to earthquake focal mechanisms and aftershock locations determined from a portable seismic network that was installed in northern Honduras after the main shock. Implications of the Swan Islands rupture for the seismically hazardous Motagua-Polochic fault system will be described.
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Earthquakes, September-October 1991
Person, W.J.
1992-01-01
There were two major earthquakes (7.0-7.9) during this reporting period. the first was in the Solomon Islands on October 14 and the second was in India on October 19. Earthquake-related deaths were reported in Guatemala and India. Htere were no significant earthquakes in the United States during the period covered in this report.
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Parvovirus-associated syndrome (Aleutian disease) in two ferrets.
Palley, L S; Corning, B F; Fox, J G; Murphy, J C; Gould, D H
1992-07-01
There is a paucity of information regarding natural Aleutian disease, caused by a parvovirus in ferrets. With the increasing popularity of ferrets as household pets and laboratory animals, and with the advent of a USDA-approved rabies vaccine, the occurrence and the etiopathogenesis of naturally acquired diseases in ferrets needs to be documented. We present the clinical and laboratory findings associated with Aleutian disease in 2 domestic ferrets, one with the chronic wasting form of the disease and one with the central nervous system form.
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Lin, Jyh-Woei
2013-01-01
Two-dimensional principal component analysis (2DPCA) and principal component analysis (PCA) are used to examine the ionospheric total electron content (TEC) data during the time period from 00:00 on August 21 to 12: 45 on August 31 (UT), which are 10 days before the M = 7.6 Philippines earthquake at 12:47:34 on August 31, 2012 (UT) with the depth at 34.9 km. From the results by using 2DPCA, a TEC precursor of Philippines earthquake is found during the time period from 4:25 to 4:40 on August 28, 2012 (UT) with the duration time of at least 15 minutes. Another earthquake-related TEC anomaly is detectable for the time period from 04:35 to 04:40 on August 27, 2012 (UT) with the duration time of at least 5 minutes during the Puerto earthquake at 04: 37:20 on August 27, 2012 (UT) (M w = 7.3) with the depth at 20.3 km. The precursor of the Puerto earthquake is not detectable. TEC anomaly is not to be found related to the Jan Mayen Island earthquake (M w = 6.8) at 13:43:24 on August 30, 2012 (UT). These earthquake-related TEC anomalies are detectable by using 2DPCA rather than PCA. They are localized nearby the epicenters of the Philippines and Puerto earthquakes. PMID:23844386
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NASA Technical Reports Server (NTRS)
Harding, David; Sauber, J.; Luthcke, S.; Carabajal, C.; Muller, J
2005-01-01
The Andaman Islands are located 120 km east of the Sunda trench in the northern quarter of the 1300 km long rupture zone of the 2004 Sumatra-Andaman Islands earthquake inferred from the distribution of aftershocks. Initial field reports indicate that several meters of uplift and up to a meter of submergence occurred on the western and eastern shorelines of the Andaman Islands, respectively, associated with the earthquake (Bilham, 2005). Satellite images also document uplift of western shoreline coral reef platforms above sea level. Body-wave (Ji, 2005; Yamamaka, 2005) and tide-gauge (Ortiz, 2005) slip inversions only resolve coseismic slip in the southern one-third to one-half of the rupture zone. The amount of coseismic slip in the Andaman Islands region is poorly constrained by these inversions. The Ice, Cloud, and land Elevation Satellite (ICESat), a part of the NASA Earth Observing System, is being used to document the spatial pattern of Andaman Islands vertical displacements in order to constrain models of slip distribution in the northern part of the rupture zone. ICESat carries the Geoscience Laser Altimeter System (GLAS) that obtains elevation measurements from 80 m diameter footprints spaced 175 m apart along profiles. For surfaces of low slope, single-footprint absolute elevation and horizontal accuracies of 10 cm and 6 m (1 sigma), respectively, referenced to the ITRF 2002 TOPEX/Poseidon ellipsoid are being obtained. Laser pulse backscatter waveforms enable separation of ground topography and overlying vegetation cover. During each 33-day observing period ICESat acquires three profiles crossing the Andaman Islands. A NNE-SSW oriented track consists of 1600 laser footprints along the western side of North, Middle, and South Andaman Islands and 240 laser footprints across the center of Great Andaman Island. Two NNW-SSE tracks consist of 440 footprints across Middle Andaman Island and 25 footprints across the west side of Sentinel Island. Cloud
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NASA Astrophysics Data System (ADS)
Barnoud, Anne; Coutant, Olivier; Bouligand, Claire; Massin, Frédérick; Stehly, Laurent
2015-04-01
We image the volcanic island of Basse-Terre, Guadeloupe, Lesser Antilles, using both earthquake travel times and noise correlations. (1) A new earthquake catalog was recently compiled for the Lesser Antilles by the CDSA/OVSG/IPGP (Massin et al., EGU General Assembly 2014) and allows us to perform classical travel time tomography to obtain smooth 3D body wave velocity models. The geometrical configuration of the volcanic arc controls the resolution of the model in our zone of interest. (2) Surface wave tomography using noise correlations was successfully applied to volcanoes (Brenguier et al., Geophys. Res. Lett. 2007). We use seismic noise recorded at 16 broad-band stations and 9 short-period stations from Basse-Terre over a period of six years (2007-2012). For each station pair, we extract a dispersion curve from the noise correlation to get surface wave velocity models. The inversion of the dispersion curves produces a 3D S-wave velocity model of the island. The spatial distribution of seismic stations accross the island is highly heterogeneous, leading to higher resolution near the dome of the Soufrière of Guadeloupe volcano. Resulting velocity models are compared with densities obtained by 3D inversion of gravimetric data (Barnoud et al., AGU Fall Meeting 2013). Further work should include simultaneous inversion of seismic and gravimetric datasets to overcome resolution limitations.
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Inception and Early Evolution of the Aleutian Arc
NASA Astrophysics Data System (ADS)
Bezard, R.; Hoernle, K.; Hauff, F.; Portnyagin, M.; Werner, R.; Yogodzinski, G.; Jicha, B.; Garbe-Schönberg, D.; Turner, S.; Schaefer, B. F.
2017-12-01
Constraining the timing and style of subduction initiation in the Aleutian system is critical to model the Cenozoic geodynamic evolution of the Pacific. Until now, the oldest ages for the Aleutian arc suggest a subduction inception at c.a. 46-47 Ma. However, the compositions of these samples (arc tholeiites and calc-alkaline rocks) are different from those of typical early-arc sequences found at extensively studied subduction systems (Izu-Bonin-Mariana), dominated by FABs and boninites. Thus, if the FAB/boninite model applies to the Aleutian, the oldest units might not have been recovered yet and the arc inception could have occurred earlier than 47 Ma. To test this hypothesis, we have sampled the lowermost submarine Aleutian sequences at ten forearc and rear-arc localities during the R/V SONNE Cruise 249. We present preliminary whole-rock major and trace element concentrations, Sr-Nd-Hf-Pb isotopes as well as U-Pb zircon dating on the recovered igneous rocks. The sample compositions range from tholeiitic to calc-alkaline. No boninites were found. Most of the samples show strong subduction signatures. However, the remaining rocks present no or minor arc-type trace element features. These samples are either depleted tholeiites with similar trace element characteristics to FABs or enriched calc-alkaline rocks. Preliminary zircon dating suggests an age of 47.2 ± 1.2 Ma for one of the samples with strong arc signatures, consistent with the oldest published ages for the Aleutian so far. However, based on their compositional similarities to FABs, the depleted tholeiites should be older than the arc-type rocks, suggesting that subduction initiation could have occurred earlier than the above-mentioned age. The absence of boninite could either reflect an incomplete sampling of the early-arc sequences or a different initiation style compared to other Pacific subduction zones. Further ages and radiogenic isotope data should refine these interpretations.
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Composite Megathrust Rupture From Deep Interplate to Trench of the 2016 Solomon Islands Earthquake
NASA Astrophysics Data System (ADS)
Lee, Shiann-Jong; Lin, Tzu-Chi; Feng, Kuan-Fu; Liu, Ting-Yu
2018-01-01
The deep plate boundary has usually been recognized as an aseismic area, with few large earthquakes occurring at the 60-100 km depth interface. In contrast, we use a finite-fault rupture model to demonstrate that large slip in the 2016
M 7.9 Solomon Islands earthquake may have originated from the deep subduction interface and propagated all the way up to the trench. The initial rupture occurred at a depth of about 100 km, forming a deep asperity and then propagating updip to the middle-depth large coseismic slip area. Our proposed source model indicates that the depth-varying rupture characteristics of this event could shift to deeper depths with respect to other subduction zones. This result also implied that the deep subducting plate boundary could also be seismogenic, which might trigger rupture at the typical middle-depth stress-locked zone and develop into rare composite megathrust events. -
Summary of Paleotsunami Investigations in Aliomanu, Anahola, Kauai
NASA Astrophysics Data System (ADS)
Griswold, F. R.; La Selle, S.; Richmond, B. M.; Jaffe, B. E.; Gelfenbaum, G. R.; Chague-Goff, C.; LeVeque, R. J.; Bellanova, P.; Sugawara, D.; Nelson, A. R.
2016-12-01
The Hawaiian Islands are susceptible to tsunami hazards from both local and distant sources. Damaging historical tsunamis, such as the 1946 and 1957 Aleutian, and 1960 Chile tsunamis, have been observed in the Hawaiian Islands, but little is known about prehistoric tsunami events. We conducted a field survey in a freshwater marsh in Anahola Valley, on the northeast shore of Kauai, looking for prehistoric tsunami deposits. Cores were collected at 142 sites, spanning to 700 meters inland, using a vibracore, gouge augers, and Russian D-corer. The coring reveals the presence of at least three marine sand layers, which all exhibit a sharp basal contact with underlying marsh peats and muds. The two uppermost sand layers were dated by measuring 137Cs activity in the upper 50 cm of several cores. These sands were likely deposited by the 1946 and 1957 Aleutian tsunamis, both of which were observed by residents in Anahola Valley, with recorded run-ups of 5.2 m and 4.9 m, respectively. The deepest sand layer was deposited approximately 700 cal yr B.P. and may correspond to recently discovered tsunami deposits on Sedanka Island in the Aleutian Islands. In order to characterize the structure and composition of the deeper sand unit, as well as its possible origin, grain size, CT scan, and X-Ray fluorescence data were collected from the cores. We are modeling tsunami propagation and inundation in Anahola Valley to test whether the observed deposits are consistent with an Aleutian subduction zone earthquake source. Additional field investigations and analyses of candidate tsunami deposits are required in order to map the extent of this deposit throughout the Hawaiian Islands and to determine a probable source of this event.
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Person, W.J.
1981-01-01
The months of May and June were somewhat quiet, seismically speaking. There was one major earthquake (7.0-7.9) off the west coast of South Island, New Zealand. The most destructive earthquake during this reporting period was in southern Iran on June 11 which caused fatalities and extensive damage. Peru also experienced a destructive earthquake on June 22 which caused fatalities and damage. In the United States, a number of earthquakes were experienced, but none caused significant damage.
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Source complexity and the physical mechanism of the 2015 Mw 7.9 Bonin Island earthquake
NASA Astrophysics Data System (ADS)
Chen, Y.; Meng, L.; Wen, L.
2015-12-01
The 30 May 2015 Mw 7.9 Bonin Island earthquake is the largest instrument-recorded deep-focus earthquake in the Izu-Bonin arc. It occurred approximately 100 km deeper than the previous seismicity, in the region unlikely to be within the core of the subducting Izu-Bonin slab. The earthquake provides an unprecedented opportunity to understand the unexpected occurrence of such isolated deep earthquakes. Multiple source inversion of the P, SH, pP and sSH phases and a novel fully three-dimensional back-projection of P and pP phases are applied to study the coseismic source process. The subevents locations and short-period energy radiations both show a L-shape bilateral rupture propagating initially in the SW direction then in the NW direction with an average rupture speed of 2.0 km/s. The decrease of focal depth on the NW branch suggests that the rupture is consistent with a single sub-horizontal plane inferred from the GCMT solution. The multiple source inversion further indicates slight variation of the focal strikes of the sub-events with the curvature of the subducting Izu-Bonin slab. The rupture is confined within an area of 20 km x 35 km, rather compact compared with the shallow earthquake of similar magnitude. The earthquake is of high stress drop on the order of 100 MPa and a low seismic efficiency of 0.19, indicating large frictional heat dissipation. The only aftershock is 11 km to the east of the mainshock hypocenter and 3 km away from the centroid of the first sub-event. Analysis of the regional tomography and nearby seismicity suggests that the earthquake may occur at the edge/periphery of the bending slab and is unlikely to be within the "cold" metastable olivine wedge. Our results suggest the spontaneous nucleation of the thermally induced shear instability is a possible mechanism for such isolated deep earthquakes.
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NASA Astrophysics Data System (ADS)
Cai, Y.; Kelemen, P. B.; Goldstein, S. L.; Yogodzinski, G. M.; Hemming, S. R.; Rioux, M. E.; Cooperdock, E. H. G.
2016-12-01
On average, arc volcanics are compositionally different from the bulk continental crust. The relatively little known plutonic part of intra-oceanic arcs is more similar to continental crust, and may play a significant role for understanding continental crust formation. Our pilot study [1] demonstrated that in the central and eastern Aleutian islands, predominantly tholeiitic Quaternary volcanic rocks have statistically different Pb-Nd-Sr-Hf isotopic signatures than predominantly calc-alkaline Miocene and older plutonic rocks, showing that these plutonics and volcanics were derived from compositionally different sources. However, studies of older volcanics are needed to determine whether (1) there was a change in magma chemistry in the central and eastern Aleutian arc between the Miocene and the present-day, or (2) coeval plutonics and volcanics are compositionally different, and formed by different processes. For example, silica- and water-rich calc-alkaline magmas may preferentially stall and form plutons after extensive degassing and rapid viscosity increase in the mid-crust, while silica- and water-poor tholeiitic magmas tend to erupt at the surface. Here we report new geochronological and geochemical results on samples collected during the 2015 GeoPRISMS shared logistics field campaign. We collected more than 500 volcanic and plutonic samples from Unalaska, Umnak and Atka islands, including pillow lavas, sills, and larger plutons. A subset of 50 samples has been analyzed for major and trace element chemistry, Pb-Nd-Sr-Hf isotopes, and Ar-Ar geochronology. So far,40Ar/39Ar cooling dates measured for the volcanics span a wide range, from zero to 35 Ma, which is comparable to the age distribution of the plutons ( 9 Ma to 39 Ma) from these islands. The forthcoming, combined geochronology and geochemistry of coeval plutonics and volcanics will contribute to our understanding of the connections between arc magmatism and continental crust formation. [1] Cai et al
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Incubation of Chile's 1960 Earthquake
NASA Astrophysics Data System (ADS)
Atwater, B. F.; Cisternas, M.; Salgado, I.; Machuca, G.; Lagos, M.; Eipert, A.; Shishikura, M.
2003-12-01
Infrequent occurrence of giant events may help explain how the 1960 Chile earthquake attained M 9.5. Although old documents imply that this earthquake followed great earthquakes of 1575, 1737 and 1837, only three earthquakes of the past 1000 years produced geologic records like those for 1960. These earlier earthquakes include the 1575 event but not 1737 or 1837. Because the 1960 earthquake had nearly twice the seismic slip expected from plate convergence since 1837, much of the strain released in 1960 may have been accumulating since 1575. Geologic evidence for such incubation comes from new paleoseismic findings at the R¡o Maullin estuary, which indents the Pacific coast at 41.5§ S midway along the 1960 rupture. The 1960 earthquake lowered the area by 1.5 m, and the ensuing tsunami spread sand across lowland soils. The subsidence killed forests and changed pastures into sandy tidal flats. Guided by these 1960 analogs, we inferred tsunami and earthquake history from sand sheets, tree rings, and old maps. At Chuyaquen, 10 km upriver from the sea, we studied sand sheets in 31 backhoe pits on a geologic transect 1 km long. Each sheet overlies the buried soil of a former marsh or meadow. The sand sheet from 1960 extends the entire length of the transect. Three earlier sheets can be correlated at least half that far. The oldest one, probably a tsunami deposit, surrounds herbaceous plants that date to AD 990-1160. Next comes a sandy tidal-flat deposit dated by stratigraphic position to about 1000-1500. The penultimate sheet is a tsunami deposit younger than twigs from 1410-1630. It probably represents the 1575 earthquake, whose accounts of shaking, tsunami, and landslides rival those of 1960. In that case, the record excludes the 1737 and 1837 events. The 1737 and 1837 events also appear missing in tree-ring evidence from islands of Misquihue, 30 km upriver from the sea. Here the subsidence in 1960 admitted brackish tidal water that defoliated tens of thousands of
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Drew, Gary S.; Piatt, John F.; Byrd, G. Vernon; Dragoo, Donald E.
2003-01-01
Although islands in the Aleutians are known to support some of the highest densities of seabirds in the world, their remoteness has limited systematic research on the at-sea distribution of seabirds near these colonies. Kasatochi, Koniuji, and Ulak islands, in the central Aleutian Islands, together comprise one of nine ecological sites monitored once every 5 years on an annual rotation since 1996 by the Alaska Maritime National Wildlife Refuge (AMNWR). To supplement annual colony monitoring and examine seabird distribution away from colony sites, the AMNWR personnel in conjunction with U.S. Geological Survey (USGS) researchers, conducted a pelagic survey of the waters around these 3 islands in 1996.Previous research in this area has focused on the seabird colony sites located on Kasatochi, Koniuji, and Ulak islands. Although boat-based circumnavigations have been used to evaluate colony populations (Early et al. 1981; Bailey and Trapp 1986; Byrd and Williams 1994; Byrd 1995a, 1995b), wide ranging pelagic surveys to examine foraging patterns had not previously been conducted near the islands. The goal of this survey was to examine foraging patterns of the seabirds nesting in the study area and identify factors that may explain seabird distribution patterns.
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NASA Astrophysics Data System (ADS)
Garcia, S.; Karplus, M. S.; Farrell, J.; Lin, F. C.; Smith, R. B.
2017-12-01
A large seismic nodal array incorporating 133 three-component, 5-Hz geophones deployed for two weeks in early November 2015 in the Upper Geyser Basin recorded earthquake and hydrothermal activity. The University of Utah, the University of Texas at El Paso, and Yellowstone National Park collaborated to deploy Fairfield Nodal ZLand 3-C geophones concentrically centered around the Old Faithful Geyser with an average station spacing of 50 m and an aperture of 1 km. The array provided a unique dataset to investigate wave propagation through various fractures and active geysers in a hydrothermal field located over the Yellowstone hotspot. The complicated sub-surface features associated with the hydrothermal field appear to impact earthquake wave propagation in the Upper Geyser Basin and to generate seismic signals. Previous work using ambient noise cross-correlation has found an intricately fractured sub-surface that provides pathways for water beneath parts of the Upper Geyser Basin that likely feed Old Faithful and other nearby geysers and hot springs. For this study, we used the data to create visualizations of local earthquake, teleseismic earthquake, and hydrothermal events as they propagate through the array. These ground motion visualizations allow observation of wave propagation through the geyser field, which may indicate the presence of anomalous structure impacting seismic velocities and attenuation. Three teleseismic events were observed in the data, two 6.9MW earthquakes that occurred off the coast of Coquimbo, Colombia 9,000km from the array and one 6.5MW near the Aleutian Islands 4,500km from the array. All three teleseismic events observed in the data exhibited strong direct P-wave arrivals and several additional phases. One local earthquake event (2.5ML) 100km from the Upper Geyser Basin was also well-recorded by the array. Time-domain spectrograms show the dominant frequencies present in the recordings of these events. The two 6.9MW earthquakes in Chile
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Herman, Matthew W.; Herrmann, Robert B.; Benz, Harley M.; Furlong, Kevin P.
2014-01-01
On September 3, 2010, a MW 7.0 (U.S. Geological Survey moment magnitude) earthquake ruptured across the Canterbury Plains in South Island, New Zealand. Since then, New Zealand GNS Science has recorded over 10,000 aftershocks ML 2.0 and larger, including three destructive ~ MW 6.0 earthquakes near Christchurch. We treat the Canterbury earthquake sequence as an intraplate earthquake sequence, and compare its kinematics to an Andersonian model for fault slip in a uniform stress field. We determined moment magnitudes and double couple solutions for 150 earthquakes having MW 3.7 and larger through the use of a waveform inversion technique using data from broadband seismic stations on South Island, New Zealand. The majority (126) of these double couple solutions have strike-slip focal mechanisms, with right-lateral slip on ENE fault planes or equivalently left-lateral slip on SSE fault planes. The remaining focal mechanisms indicate reverse faulting, except for two normal faulting events. The strike-slip segments have compatible orientations for slip in a stress field with a horizontal σ1 oriented ~ N115°E, and horizontal σ3. The preference for right lateral strike-slip earthquakes suggests that these structures are inherited from previous stages of deformation. Reverse slip is interpreted to have occurred on previously existing structures in regions with an absence of existing structures optimally oriented for strike-slip deformation. Despite the variations in slip direction and faulting style, most aftershocks had nearly the same P-axis orientation, consistent with the regional σ1. There is no evidence for significant changes in these stress orientations throughout the Canterbury earthquake sequence.
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NASA Astrophysics Data System (ADS)
Haney, M. M.; Tsai, V. C.; Ward, K. M.
2016-12-01
Recently, Haney and Tsai (2015) developed a new approach to Rayleigh-wave inversion based on assumptions that are similar to those used in the formulation of the Dix equation in reflection seismology. Here we apply the Dix technique to Rayleigh-wave phase-velocity maps by Ekstrom (2013) and Ward (2015) of the contiguous US and Alaska, respectively, at periods between 12 and 45 s. We refine the initial Dix result with subsequent nonlinear inversion to estimate Moho depth together with shear-wave velocity of the lower crust and upper mantle. In the contiguous US, the Moho we image agrees well with recent receiver function studies. There is an apparent deepening of the Moho to the west of the Cascades volcanic chain that we interpret as the waveguide interface transitioning to the slab due to the continental Moho becoming transparent above the mantle forearc. This feature abruptly terminates at the southern extent of the Cascadia subduction zone. We compare the depths of this "apparent Moho" with published estimates of the depth to the Juan de Fuca Plate since, owing to the paucity of tectonic earthquakes, the Slab1.0 model is not defined in Cascadia. Our result in Alaska is the first regional Moho map derived explicitly from seismic waves. We find that crustal thickness is generally correlated with topography, with thicker crust beneath mountain ranges in southern Alaska. North of the Denali Fault, the Moho is smoother than to the south and located at typical depths of 30-35 km. There are also indications that the waveguide interface we solve for beneath Prince William Sound is actually the subducting slab instead of the continental Moho. The slab structure beneath Prince William Sound extends further east than the Pacific slab represented in the Slab1.0 model. Using the limited number of broadband seismometers in the Aleutian Islands, we obtain preliminary estimates for the crustal structure beneath the western portion of the Aleutian-Alaska subduction zone.
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The isolated 678-km deep 30 May 2015 MW 7.9 Ogasawara (Bonin) Islands earthquake
NASA Astrophysics Data System (ADS)
Ye, L.; Lay, T.; Zhan, Z.; Kanamori, H.; Hao, J.
2015-12-01
Deep-focus earthquakes, located 300 to 700 km below the Earth's surface within sinking slabs of relatively cold oceanic lithosphere, are mysterious phenomena. Seismic radiation from deep events is essentially indistinguishable from that for shallow stick-slip frictional-sliding earthquakes, but the confining pressure and temperature are so high for deep-focus events that a distinct process is likely needed to account for their abrupt energy release. The largest recorded deep-focus earthquake (MW 7.9) in the Izu-Bonin slab struck on 30 May 2015 beneath the Ogasawara (Bonin) Islands, isolated from prior seismicity by over 100 km in depth, and followed by only 2 small aftershocks. Globally, this is the deepest (678 km) major (MW > 7) earthquake in the seismological record. Seismicity indicates along-strike contortion of the Izu-Bonin slab, with horizontal flattening near a depth of 550 km in the Izu region and progressive steepening to near-vertical toward the south above the location of the 2015 event. Analyses of a large global data set of P, SH and pP seismic phases using short-period back-projection, subevent directivity, and broadband finite-fault inversion indicate that the mainshock ruptured a shallowly-dipping fault plane with patchy slip that spread over a distance of ~40 km with variable expansion rate (~5 km/s down-dip initially, ~3 km/s up-dip later). During the 17 s rupture duration the radiated energy was ~3.3 x 1016 J and the stress drop was ~38 MPa. The radiation efficiency is moderate (0.34), intermediate to that of the 1994 Bolivia and 2013 Sea of Okhotsk MW 8.3 earthquakes, indicating a continuum of processes. The isolated occurrence of the event suggests that localized stress concentration associated with the pronounced deformation of the Izu-Bonin slab likely played a role in generating this major earthquake.
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Earthquakes, September-October 1980
Person, W.J.
1981-01-01
There were two major (magnitudes 7.0-7.9) earthquakes during this reporting period; a magnitude (M) 7.3 in Algeria where many people were killed or injured and extensive damage occurred, and an M=7.2 in the Loyalty Islands region of the South Pacific. Japan was struck by a damaging earthquake on September 24, killing two people and causing injuries. There were no damaging earthquakes in the United States.
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Person, W.J.
1992-01-01
There were two major earthquakes (7.0≤M<8.0) during this reporting period. A magnitude 7.5 earthquake occurred in Kyrgyzstan on August 19 and a magnitude 7.0 quake struck the Ascension Island region on August 28. In southern California, aftershocks of the magnitude 7.6 earthquake on June 28, 1992, continued. One of these aftershocks caused damage and injuries, and at least one other aftershock caused additional damage. Earthquake-related fatalities were reportred in Kyrgzstan and Pakistan.
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Hardell, Sara; Tilander, Hanna; Welfinger-Smith, Gretchen; Burger, Joanna; Carpenter, David O.
2010-01-01
Background Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs) and chlorinated pesticides, have been shown to have many adverse human health effects. These contaminants therefore may pose a risk to Alaska Natives that follow a traditional diet high in marine mammals and fish, in which POPs bioaccumulate. Methods and Findings This study examined the levels of PCBs and three pesticides [p, p′-DDE, mirex, and hexachlorobenzene (HCB)] in muscle tissue from nine fish species from several locations around the Aleutian Islands of Alaska. The highest median PCB level was found in rock sole (Lepidopsetta bilineata, 285 ppb, wet weight), while the lowest level was found in rock greenling (Hexagrammos lagocephalus, 104 ppb, wet weight). Lipid adjusted PCB values were also calculated and significant interspecies differences were found. Again, rock sole had the highest level (68,536 ppb, lipid weight). Concerning the PCB congener patterns, the more highly chlorinated congeners were most common as would be expected due to their greater persistence. Among the pesticides, p, p′-DDE generally dominated, and the highest level was found in sockeye salmon (Oncorhynchus nerka, 6.9 ppb, wet weight). The methodology developed by U.S. Environmental Protection Agency (USEPA) was used to calculate risk-based consumption limits for the analyzed fish species. For cancer health endpoints for PCBs, all species would trigger strict advisories of between two and six meals per year, depending upon species. For noncancer effects by PCBs, advisories of between seven and twenty-two meals per year were triggered. None of the pesticides triggered consumption limits. Conclusion The fish analyzed, mainly from Adak, contain significant concentrations of POPs, in particular PCBs, which raises the question whether these fish are safe to eat, particularly for sensitive populations. However when assessing any risk of the traditional diet, one must also consider the many health
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Ischia Island: Historical Seismicity and Dynamics
NASA Astrophysics Data System (ADS)
Carlino, S.; Cubellis, E.; Iannuzzi, R.; Luongo, G.; Obrizzo, F.
2003-04-01
The seismic energy release in volcanic areas is a complex process and the island of Ischia provides a significant scenario of historical seismicity. This is characterized by the occurence of earthquakes with low energy and high intensity. Information on the seismicity of the island spans about eight centuries, starting from 1228. With regard to effects, the most recent earthquake of 1883 is extensively documented both in the literature and unpublished sources. The earthquake caused 2333 deaths and the destruction of the historical and environmental heritage of some areas of the island. The most severe damage occurred in Casamicciola. This event, which was the first great catastrophe after the unification of Italy in the 1860s (Imax = XI degree MCS), represents an important date in the prevention of natural disasters, in that it was after this earthquake that the first Seismic Safety Act in Italy was passed by which lower risk zones were identified for new settlements. Thanks to such detailed analysis, reliable modelling of the seismic source was also obtained. The historical data onwards makes it possible to identify the area of the epicenter of all known earthquakes as the northern slope of Monte Epomeo, while analysis of the effects of earthquakes and the geological structures allows us to evaluate the stress fields that generate the earthquakes. In a volcanic area, interpretation of the mechanisms of release and propagation of seismic energy is made even more complex as the stress field that acts at a regional level is compounded by that generated from migration of magmatic masses towards the surface, as well as the rheologic properties of the rocks dependent on the high geothermic gradient. Such structural and dynamic conditions make the island of Ischia a seismic area of considerable interest. It would appear necessary to evaluate the expected damage caused by a new event linked to the renewal of dynamics of the island, where high population density and the
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NASA Astrophysics Data System (ADS)
Zeglin, L. H.; Rainey, F.; Wang, B.; Waythomas, C.; Talbot, S. L.
2013-12-01
Microorganisms are abundant and diverse in soil and their integrated activity drives nutrient cycling on the ecosystem scale. Organic matter (OM) inputs from plant production support microbial heterotrophic life, and soil geochemistry constrains microbial activity and diversity. As vegetation and soil develops over time, these factors change, modifying the controls on microbial heterogeneity. Following a volcanic eruption, ash deposition creates new surfaces where both organismal growth and weathering processes are effectively reset. The trajectory of microbial community development following this disturbance depends on both organic matter accumulation and geochemical constraints. Also, dispersal of microbial cells to the sterile ash surface may determine microbial community succession. The Aleutian Islands (Alaska, USA) are a dynamic volcanic region, with active and dormant volcanoes distributed across the volcanic arc. One of these volcanoes, Kasatochi, erupted violently in August 2008, burying a small lush island in pryoclastic flows and fine ash. Since, plants and birds are beginning to re-establish on developing surfaces, including legacy soils exposed by rapid erosion of pyroclastic deposits, suggesting that recovery of microbial life is also proceeding. However, soil microbial diversity and function has not been examined on Kasatochi Island or across the greater Aleutian region. The project goal is to address these questions: How is soil microbial community structure and function developing following the Kasatochi eruption? What is the relative importance of dispersal, soil OM and geochemistry to microbial community heterogeneity across the Aleutians? Surface mineral soil (20-cm depth) samples were collected from Kasatochi Island in summer 2013, five years after the 2008 eruption, and from eight additional Aleutian islands. On Kasatochi, pryoclastic deposits, exposed legacy soils supporting regrowth of remnant dune wild-rye (Leymus mollis) and mesic meadow
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NASA Astrophysics Data System (ADS)
Gorum, Tolga; Yildirim, Cengiz
2017-04-01
This study presents the first results on analysis of the landslides triggered by the Mw 7.8 Kaikoura earthquake that occurred on November 14, 2016 in the region between the Hikurangi subduction system of the North Island and the oblique collisional regime of the South Island (Alpine Fault). The earthquake ruptured several faults that expand into two different tectonic domains which are compose of the strike-slip Marlborough fault system and the compressional North Canterbury Fault Zone. Here we present the preliminary mapping results of the distribution of landslides triggered by the earthquake. An extensive landslide interpretation was carried out using sets of optical high resolution satellite images (e.g. Sentinel-2 and Göktürk-2) for both the pre- and post-earthquake situation. The landslides were identified and mapped as polygons using multi-temporal visual image interpretation based on satellite imagery and morphological elements of landslide diagnostic indicators. Nearly 8,500 individual landslides with different sizes and types were mapped. The distribution pattern of the mapped coseismic landslides shows that the slope failures are highly concentrated along the ruptured faults and side slopes of the structurally controlled major rivers such as Hapuku and Clarence Rivers that drain the northeastern slopes of the region. Our spatial analysis of landslide occurrences with ground acceleration, lithology, slope, topographic relief and surface deformation indicated extensive control of steep slope and high topographic relief on landslides with ground acceleration as the trigger. We show that spatial distribution of slope failures shows decreasing frequency away from the earthquake faults up to 25 km towards east, and abundance of landslides spatially coincides with the coseismic fault geometries and aftershock distributions. We conclude that combined effect of complex rupture dynamics and topography primarily control the distribution pattern of the landslides
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NASA Astrophysics Data System (ADS)
Chen, Ting; Luo, Haipeng; Furlong, Kevin P.
2017-05-01
On 1st April 2007 a Mw 8.1 megathrust earthquake occurred in the western Solomon Islands of the Southwest Pacific and generated a regional tsunami with run-up heights of up to 12 m. A Bayesian inversion model is constructed to derive fault dip angle and cumulative co-seismic and early post-seismic slip using coral reef displacement measurements, in which both data misfit and moment magnitude are used as constraints. Results show three shallow, high-slip patches concentrated along the trench from west of Ranongga Island to Rendova Island on a fault plane dipping 20°, and a maximum dip slip of 11.6 m beneath Ranongga Island. Considerable subsidence on Simbo Island outboard of the trench on the subducting plate is not well explained with this model, but may be related to the effects of afterslip and/or Simbo Island's location near the triple junction among the Australia, Woodlark and Pacific plates.
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Indirect food web interactions: Sea otters and kelp forest fishes in the Aleutian archipelago
Reisewitz, S.E.; Estes, J.A.; Simenstad, C.A.
2006-01-01
Although trophic cascades - the effect of apex predators on progressively lower trophic level species through top-down forcing - have been demonstrated in diverse ecosystems, the broader potential influences of trophic cascades on other species and ecosystem processes are not well studied. We used the overexploitation, recovery and subsequent collapse of sea otter (Enhydra lutris) populations in the Aleutian archipelago to explore if and how the abundance and diet of kelp forest fishes are influenced by a trophic cascade linking sea otters with sea urchins and fleshy macroalgae. We measured the abundance of sea urchins (biomass density), kelp (numerical density) and fish (Catch per unit effort) at four islands in the mid-1980s (when otters were abundant at two of the islands and rare at the two others) and in 2000 (after otters had become rare at all four islands). Our fish studies focused on rock greenling (Hexagrammos lagocephalus), the numerically dominant species in this region. In the mid-1980s, the two islands with high-density otter populations supported dense kelp forests, relatively few urchins, and abundant rock greenling whereas the opposite pattern (abundant urchins, sparse kelp forests, and relatively few rock greenling) occurred at islands where otters were rare. In the 2000, the abundances of urchins, kelp and greenling were grossly unchanged at islands where otters were initially rare but had shifted to the characteristic pattern of otter-free systems at islands where otters were initially abundant. Significant changes in greenling diet occurred between the mid-1980s and the 2000 although the reasons for these changes were difficult to assess because of strong island-specific effects. Whereas urchin-dominated communities supported more diverse fish assemblages than kelp-dominated communities, this was not a simple effect of the otter-induced trophic cascade because all islands supported more diverse fish assemblages in 2000 than in the mid-1980s
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-09-14
... Yellowfin Sole in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries... allowable catch (TAC) assigned to the Bering Sea and Aleutian Islands trawl limited access sector to the Amendment 80 cooperative in the Bering Sea and Aleutian Islands management area (BSAI). This action is...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-10-12
... Yellowfin Sole in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries... allowable catch (TAC) assigned to the Bering Sea and Aleutian Islands trawl limited access sector to the Amendment 80 cooperative in the Bering Sea and Aleutian Islands management area (BSAI). This action is...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-11-17
... the Bering Sea Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine... Bering Sea subarea of the Bering Sea and Aleutian Islands management area. This action is necessary to... management plan for the Bering Sea and Aleutian Islands management area. DATES: Effective November 14, 2011...
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NASA Astrophysics Data System (ADS)
Lin, G.; Okubo, P.
2015-12-01
We present a refined catalog of earthquake locations and focal mechanisms for the Island of Hawaii, focusing on Mauna Loa and Kilauea volcanoes. The location catalog is based on first-arrival times and waveform data of both compressional and shear waves from over 181,000 events on and near the Island of Hawaii between 1986 and 2009 recorded by the seismic stations at the Hawaiian Volcano Observatory. We relocate all the earthquakes by applying ray-tracing through an existing three-dimensional velocity model, similar event cluster analysis and a differential-time relocation method. The resulting location catalog represents an extension of previous relocation studies, covering a longer time period and consisting of more events with well-constrained absolute locations. The focal mechanisms are obtained based on the compressional-wave first motion polarities by applying the HASH program to the waveform cross-correlation relocated earthquakes. Overall, the good-quality focal solutions are dominated by normal faulting in our study area, especially in the active Kaoiki and Hilea seismic zones. Kilauea caldera is characterized by a mixture of approximately equal numbers of normal, strike-slip, and reverse faults, whereas focal mechanisms in its south flank are predominantly reverse. Our results are essential for mapping the seismic strain and stress field and for understanding the seismo-volcano-tectonic relationships within the magmatic systems.
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Petersen, Margaret R.; Sonsthagen, Sarah A.; Sexson, Matthew G.
2015-01-01
Islands provide refuges for populations of many species where they find safety from predators, but the introduction of predators frequently results in elimination or dramatic reductions in island-dwelling organisms. When predators are removed, re-colonization for some species occurs naturally, and inter-island phylogeographic relationships and current movement patterns can illuminate processes of colonization. We studied a case of re-colonization of common eiders Somateria mollissima following removal of introduced arctic foxes Vulpes lagopus in the Aleutian Archipelago, Alaska. We expected common eiders to resume nesting on islands cleared of foxes and to re-colonize from nearby islets, islands, and island groups. We thus expected common eiders to show limited genetic structure indicative of extensive mixing among island populations. Satellite telemetry was used to record current movement patterns of female common eiders from six islands across three island groups. We collected genetic data from these and other nesting common eiders at 14 microsatellite loci and the mitochondrial DNA control region to examine population genetic structure, historical fluctuations in population demography, and gene flow. Our results suggest recent interchange among islands. Analysis of microsatellite data supports satellite telemetry data of increased dispersal of common eiders to nearby areas and little between island groups. Although evidence from mtDNA is suggestive of female dispersal among island groups, gene flow is insufficient to account for recolonization and rapid population growth. Instead, near-by remnant populations of common eiders contributed substantially to population expansion, without which re-colonization would have likely occurred at a much lower rate. Genetic and morphometric data of common eiders within one island group two and three decades after re-colonization suggests reduced movement of eiders among islands and little movement between island groups after
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-11-07
... in the Bering Sea Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National... Pacific ocean perch in the Bering Sea subarea of the Bering Sea and Aleutian Islands management area. This... Bering Sea subarea of the Bering Sea and Aleutian Islands management area. DATES: Effective 1200 hrs...
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50 CFR 679.64 - Harvesting sideboard limits in other fisheries.
Code of Federal Regulations, 2013 CFR
2013-10-01
... Pacific ocean perch. (A) The Aleutian Islands Pacific ocean perch harvest limit will be equal to the 1996 through 1997 aggregate retained catch of Aleutian Islands Pacific ocean perch by catcher/processors listed... sum of the Aleutian Islands Pacific ocean perch catch in 1996 and 1997 multiplied by the remainder of...
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50 CFR 679.64 - Harvesting sideboard limits in other fisheries.
Code of Federal Regulations, 2014 CFR
2014-10-01
... area or subarea of the BSAI as follows: (i) Aleutian Islands Pacific ocean perch. (A) The Aleutian Islands Pacific ocean perch harvest limit will be equal to the 1996 through 1997 aggregate retained catch of Aleutian Islands Pacific ocean perch by catcher/processors listed in Sections 208(e)(1) through...
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50 CFR 679.64 - Harvesting sideboard limits in other fisheries.
Code of Federal Regulations, 2012 CFR
2012-10-01
... Pacific ocean perch. (A) The Aleutian Islands Pacific ocean perch harvest limit will be equal to the 1996 through 1997 aggregate retained catch of Aleutian Islands Pacific ocean perch by catcher/processors listed... sum of the Aleutian Islands Pacific ocean perch catch in 1996 and 1997 multiplied by the remainder of...
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Age and significance of earthquake-induced liquefaction near Vancouver, British Columbia, Canada
Clague, J.J.; Naesgaard, E.; Nelson, A.R.
1997-01-01
In late 1994, sand dykes, large sand blows, and deformed strata were exposed in the walls of an excavation at Annacis Island on the Fraser River delta near Vancouver, British Columbia. The features record liquefaction during a large earthquake about 1700 years ago; this was perhaps the largest earthquake to affect the Vancouver area in the last 3500 years. Similar, less well-dated features have been reported from several other sites on the Fraser delta and may be products of the same earthquake. Three radiocarbon ages that closely delimit the time of liquefaction on Annacis Island are similar to the most precise radiocarbon ages on coseismically subsided marsh soils at estuaries in southern Washington and Oregon. Both the liquefaction and the subsidence may have been produced by a single great plate-boundary earthquake at the Cascadia subduction zone. Alternatively, liquefaction at Annacis Island may have been caused by a large crustal or subcrustal earthquake of about the same age as a plate-boundary earthquake farther west. The data from Annacis Island and other sites on the Fraser delta suggest that earthquakes capable of producing extensive liquefaction in this area are rare events. Further, liquefaction analysis using historical seismicity suggests that current assessment procedures may overestimate liquefaction risk.
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NASA Technical Reports Server (NTRS)
Murray, John J.; Hudnall, L. A.; Matus, A.; Krueger, A. J.; Trepte, C. r.
2010-01-01
The Aleutian Islands of Alaska are home to a number of major volcanoes which periodically present a significant hazard to aviation. During summer of 2008, the Okmok and Kasatochi volcanoes experienced moderate eruptive events. These were followed a dramatic, major eruption of Mount Redoubt in late March 2009. The Redoubt case is extensively covered in this paper. Volcanic ash and SO2 from each of these eruptions dispersed throughout the atmosphere. This created the potential for major problems for air traffic near the ash dispersions and at significant distances downwind. The NASA Applied Sciences Weather Program implements a wide variety of research projects to develop volcanic ash detection, characterization and tracking applications for NASA Earth Observing System and NOAA GOES and POES satellites. Chemistry applications using NASA AURA satellite Ozone Monitoring System (OMI) retrievals produced SO2 measurements to trace the dispersion of volcanic aerosol. This work was complimented by advanced multi-channel imager applications for the discrimination and height assignment of volcanic ash using NASA MODIS and NOAA GOES and POES imager data. Instruments similar to MODIS and OMI are scheduled for operational deployment on NPOESS. In addition, the NASA Calipso satellite provided highly accurate measurements of aerosol height and dispersion for the calibration and validation of these algorithms and for corroborative research studies. All of this work shortens the lead time for transition to operations and ensures that research satellite data and applications are operationally relevant and utilized quickly after the deployment of operational satellite systems. Introduction
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Selected 1970 Census Data for Alaska Communities. Part 4 - Bristol Bay-Aleutian Region.
ERIC Educational Resources Information Center
Alaska State Dept. of Community and Regional Affairs, Juneau. Div. of Community Planning.
As 1 of 6 regional reports supplying statistical information on Alaska's incorporated and unincorporated communities (those of 25 or more people), this report on Alaska's Bristol Bay-Aleutian Region presents data derived from the 1970 U.S. Census first-count microfilm. Organized via the 3 Bristol Bay-Aleutian census divisions, data are presented…
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50 CFR 679.64 - Harvesting sideboard limits in other fisheries.
Code of Federal Regulations, 2010 CFR
2010-10-01
.../processors be calculated? Except for Aleutian Islands pollock and BSAI Pacific cod, the Regional... group in which a TAC is specified for an area or subarea of the BSAI as follows: (i) Aleutian Islands Pacific ocean perch. (A) The Aleutian Islands Pacific ocean perch harvest limit will be equal to the 1996...
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NASA Astrophysics Data System (ADS)
Tsuji, Y.; Takahashi, T.; Imai, K.
2010-12-01
The tsunami of the Chilean Earthquake (Mw8.8) of February 27, 2010 was detected also on the coasts of the Japanese Islands about 23 hours after the occurrence of the main shock. It caused no human damage. There was slight house damage manly in Miyagi prefecture, south part of Sanriku coast; six and fifty one houses were flooded above and below the floor, respectively. It caused remarkable fishery loss of 75 Million US$ mainly due to breaking of cultivation rafts. The tsunami of the 1960 Chilean Earthquake(Mw9.5) also hit the Japanese coasts more severely. It caused more immense damage than the 2010 tsunami; 142 people were killed, 1,581 houses were entirely destroyed, and 1,256 houses were swept away. Most of damage occurred in the districts of Sanriku coast, where inundation heights exceeded six meters at several points. We made field survey along the Japanese coast, visited offices of fishermen’s cooperatives at over 300 fishery ports, gathered eyewitnesses counts, and obtained information of the inundation limit, arrival time, and building and fishery damage. On the basis of the information of inundation, we measured tsunami heights. We obtained data of tsunami height at more than two hundred points (Tsuji et al., 2010). The distributions of the two tsunamis of the 1960 and the 2010 Chilean earthquakes on the coasts along the Japanese Islands are shown as Fig. 1. The maximum height of 2.2 meters was recorded at Kesennuma City, Miyagi Prefecture. The heights of the 2010 tsunami were generally one third of those of the 1960 tsunami. An eminent peak appears at Sanriku coast commonly for both tsunamis. In addition smaller peaks also appear commonly at the coasts of the east part of Hokkaido, near the top of Boso peninsula, near the top of Izu Peninsula, the east coast of Kii Peninsula, Tokushima prefecture, eastern part of Shikoku, and near the Cape Ashizuri in western part of Shikoku. Fig. 1 Trace height distributions of the tsunamis of the 1960(red) and the 2010
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NASA Astrophysics Data System (ADS)
Miyagi, Y.; Ozawa, T.
2010-12-01
The Solomon Islands are located in the southwest of the Pacific Ocean. The Australian, Woodlark, and Solomon Sea plates subduct toward the northeast beneath the Pacific plate. Interaction among these four plates cause complicated tectonics around the Solomon Islands, and have caused interplate earthquakes in the subduction zone (e.g. Lay and Kanamori, 1980; Xu and Schwarts, 1993). On April 1, 2007 (UTC), an M8.1 interplate earthquake occurred in the subduction zone between the Pacific Plate and the Australian Plate. This earthquake was accompanied by a large tsunami and caused considerable damage in the area. The Japan Aerospace Exploration Agency (JAXA) carried out emergency observations using the Phased Array type L-band Synthetic Aperture Rader (PALSAR) installed on Advanced Land Observing Satellite (ALOS), and detected more than 2m of maximum displacement using differential interferometric SAR (DInSAR) technique. Miyagi et al. (2009) estimated a slip distribution of the seismic fault mainly from the PALSAR/DInSAR data and suggested that most of a seismic gap was filled by the 2007 events, but a small seismic gap connecting to an Mw7.0-sized earthquake still remained. On January 3, 2010, an M7.1 earthquake occurred in the vicinity of the remnant seismic gap. ALOS/PALSAR observed epicentral area both before and after the event, and detected crustal deformation associated with the earthquake. We inferred fault model using the PALSAR/DInSAR data and concluded that the 2010 event was the supposed thrust earthquake filling the remnant seismic gap. A distribution of coulomb failure stress change in the epicentral area after the 2007 event suggested the possibility that the 2010 event was triggered by the 2007 earthquake.
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NASA Astrophysics Data System (ADS)
Graham, Shannon E.; DeMets, Charles; DeShon, Heather R.; Rogers, Robert; Maradiaga, Manuel Rodriguez; Strauch, Wilfried; Wiese, Klaus; Hernandez, Douglas
2012-09-01
We use measurements at 35 GPS stations in northern Central America and 25 seismometers at teleseismic distances to estimate the distribution of slip, source time function and Coulomb stress changes of the Mw = 7.3 2009 May 28, Swan Islands fault earthquake. This event, the largest in the region for several decades, ruptured the offshore continuation of the seismically hazardous Motagua fault of Guatemala, the site of the destructive Ms = 7.5 earthquake in 1976. Measured GPS offsets range from 308 millimetres at a campaign site in northern Honduras to 6 millimetres at five continuous sites in El Salvador. Separate inversions of geodetic and seismic data both indicate that up to ˜1 m of coseismic slip occurred along a ˜250-km-long rupture zone between the island of Roatan and the eastern limit of the 1976 M = 7.5 Motagua fault earthquake in Guatemala. Evidence for slip ˜250 km west of the epicentre is corroborated independently by aftershocks recorded by a local seismic network and by the high concentration of damage to structures in areas of northern Honduras adjacent to the western limit of the rupture zone. Coulomb stresses determined from the coseismic slip distribution resolve a maximum of 1 bar of stress transferred to the seismically hazardous Motagua fault and further indicate unclamping of normal faults along the northern shore of Honduras, where two M > 5 normal-faulting earthquakes and numerous small earthquakes were triggered by the main shock.
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Mercury levels and potential risk from subsistence foods from the Aleutians.
Burger, Joanna; Gochfeld, Michael; Jeitner, Christian; Burke, Sean; Stamm, Tim; Snigaroff, Ronald; Snigaroff, Dan; Patrick, Robert; Weston, Jim
2007-10-01
Considerable attention has been devoted to contaminants (mainly PCBs and mercury) in subsistence foods (particularly fish) from various parts of the world. However, relatively little attention has been devoted to examining mercury levels in a full range of subsistence foods from a particular region. While managers and scientists compute risk based on site-specific data on contaminant levels and consumption rates, a first step in making risk decisions by subsistence peoples is knowledge about the relative levels of mercury in the foods they eat. This study examined levels of mercury in subsistence foods (edible components) from several islands in the western Aleutians of Alaska, including algae (4 species), invertebrates (9 species), fish (15 species) and birds (5 species). Samples were gathered by both subsistence hunters/fishers and by scientists using the same equipment. Another objective was to determine if there were differences in mercury levels in subsistence foods gathered from different Aleutian islands. We tested the null hypotheses that there were no interspecific and interisland differences in mercury levels. Because of variation in distribution and the nature of subsistence hunting and fishing, not all organisms were collected from each of the islands. There were significant and important differences in mercury levels among species, but the locational differences were rather small. There was an order of magnitude difference between algae/some invertebrates and fish/birds. Even within fish, there were significant differences. The highest mean mercury levels were in flathead sole (Hippoglossoides elassodon, 0.277 ppm), yellow irish lord (Hemilepidotus jardani, 0.281 ppm), great sculpin (Myoxocephalus polyacanthocephalus, 0.366 ppm), glaucous-winged gull (Larus glaucescens, 0.329 ppm) and its eggs (0.364 ppm), and pigeon guillemot (Cepphus columba, 0.494 ppm). Mercury levels increased with increasing weight of the organisms for limpets (Tectura scutum
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Variations in Melt Generation and Migration along the Aleutian Arc (Invited)
NASA Astrophysics Data System (ADS)
Plank, T. A.; Van Keken, P. E.
2013-12-01
The generation and ascent of mantle melt beneath volcanic arcs sets the course for how magmas differentiate to form the continental crust and erupt explosively from volcanoes. Although the basic framework of melting at subduction zones is understood to involve the convective influx of hot mantle (Tp ≥ 1300°C) and advective transport of water-rich fluids from the subducting slab, the P-T paths that melts follow during melt generation and migration are still not well known. The Aleutian Arc provides an opportunity to explore the conditions of mantle melting in the context of volcanoes that span an unusually large range in the depth to the slab, from Seguam island, with among the shallowest depths to the slab worldwide (~65 km, [1]) to Bogoslof island, behind the main volcanic front and twice the depth to the slab (~130 km). Here we combine thermal models tuned to Aleutian subduction parameters [after 2] with petrological estimates of the T and P of mantle-melt equilibration, using a major element geothermometer [3] and estimates of H2O and fO2 from olivine-hosted melt inclusion measurements [4] for basaltic magmas from 6 volcanoes in the central Aleutians (Korovin, Seguam, Bogoslof, Pakushin, Akutan, Shishaldin). We find mantle-melt equilibration conditions to vary systematically as a function of the depth to the slab, from 30 km and 1220°C (for Seguam) to 60 km and 1300°C (for Bogoslof). Such shallow depths, which extend up to the Moho, define a region perched well above the hot core of the mantle wedge predicted from thermal models, even considering the shallow depths of slab-mantle coupling (< 60 km) required to supply hot mantle beneath Seguam. Thus, even though the greatest melt production will occur in the hot core of the wedge (50-100 km depth), melts apparently ascend and re-equilibrate in the shallowest mantle. Volcanoes that overlie the greatest depth to the slab, and lie furthest from the wedge corner, stall at greater depths (~60 km), at the base of
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Amchitka Island, Alaska, Biological Monitoring Report 2011 Sampling Results
DOE Office of Scientific and Technical Information (OSTI.GOV)
None
The Long-Term Surveillance and Maintenance (LTS&M) Plan for the U.S. Department of Energy (DOE) Office of Legacy Management (LM) Amchitka Island sites describes how LM plans to conduct its mission to protect human health and the environment at the three nuclear test sites located on Amchitka Island, Alaska. Amchitka Island, near the western end of the Aleutian Islands, is approximately 1,340 miles west-southwest of Anchorage, Alaska. Amchitka is part of the Aleutian Island Unit of the Alaska Maritime National Wildlife Refuge, which is administered by the U.S. Fish and Wildlife Service (USFWS). Since World War II, Amchitka has been usedmore » by multiple U.S. government agencies for various military and research activities. From 1943 to 1950, it was used as a forward air base for the U.S. Armed Forces. During the middle 1960s and early 1970s, the U.S. Department of Defense (DOD) and the U.S. Atomic Energy Commission (AEC) used a portion of the island as a site for underground nuclear tests. During the late 1980s and early 1990s, the U.S. Navy constructed and operated a radar station on the island. Three underground nuclear tests were conducted on Amchitka Island. DOD, in conjunction with AEC, conducted the first nuclear test (named Long Shot) in 1965 to provide data that would improve the United States' capability of detecting underground nuclear explosions. The second nuclear test (Milrow) was a weapons-related test conducted by AEC in 1969 as a means to study the feasibility of detonating a much larger device. Cannikin, the third nuclear test on Amchitka, was a weapons-related test detonated on November 6, 1971. With the exception of small concentrations of tritium detected in surface water shortly after the Long Shot test, radioactive fission products from the tests remain in the subsurface at each test location As a continuation of the environmental monitoring that has taken place on Amchitka Island since before 1965, LM in the summer of 2011 collected
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Lin, Guoqing; Okubo, Paul G.
2016-01-01
We present high-quality focal mechanisms based on a refined earthquake location catalog for the Island of Hawai'i, focusing on Mauna Loa and Kīlauea volcanoes. The relocation catalog is based on first-arrival times and waveform data of both compressional and shear waves for about 180,000 events on and near the Island of Hawai'i between 1986 and 2009 recorded by the seismic stations at the Hawaiian Volcano Observatory. We relocate all the earthquakes by applying ray tracing through an existing three-dimensional velocity model, similar event cluster analysis, and a differential-time relocation method. The resulting location catalog represents an expansion of previous relocation studies, covering a longer time period and consisting of more events with well-constrained absolute locations. The focal mechanisms are obtained based on the compressional-wave first-motion polarities and compressional-to-shear wave amplitude ratios by applying the HASH program to the waveform cross correlation relocated earthquakes. Overall, the good-quality (defined by the HASH parameters) focal solutions are dominated by normal faulting in our study area, especially in the active Ka'ōiki and Hīlea seismic zones. Kīlauea caldera is characterized by a mixture of approximately equal numbers of normal, strike-slip, and reverse faults, whereas its south flank has slightly fewer strike-slip events. Our relocation and focal mechanism results will be useful for mapping the seismic stress and strain fields and for understanding the seismic-volcanic-tectonic relationships within the magmatic systems.
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NASA Astrophysics Data System (ADS)
Lin, Guoqing; Okubo, Paul G.
2016-07-01
We present high-quality focal mechanisms based on a refined earthquake location catalog for the Island of Hawai'i, focusing on Mauna Loa and Kīlauea volcanoes. The relocation catalog is based on first-arrival times and waveform data of both compressional and shear waves for about 180,000 events on and near the Island of Hawai'i between 1986 and 2009 recorded by the seismic stations at the Hawaiian Volcano Observatory. We relocate all the earthquakes by applying ray tracing through an existing three-dimensional velocity model, similar event cluster analysis, and a differential-time relocation method. The resulting location catalog represents an expansion of previous relocation studies, covering a longer time period and consisting of more events with well-constrained absolute locations. The focal mechanisms are obtained based on the compressional-wave first-motion polarities and compressional-to-shear wave amplitude ratios by applying the HASH program to the waveform cross correlation relocated earthquakes. Overall, the good-quality (defined by the HASH parameters) focal solutions are dominated by normal faulting in our study area, especially in the active Ka'ōiki and Hīlea seismic zones. Kīlauea caldera is characterized by a mixture of approximately equal numbers of normal, strike-slip, and reverse faults, whereas its south flank has slightly fewer strike-slip events. Our relocation and focal mechanism results will be useful for mapping the seismic stress and strain fields and for understanding the seismic-volcanic-tectonic relationships within the magmatic systems.
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NASA Astrophysics Data System (ADS)
Yano, Tomoko E.; Takeda, Tetsuya; Matsubara, Makoto; Shiomi, Katsuhiko
2017-04-01
We have generated a high-resolution catalog called the ;Japan Unified hIgh-resolution relocated Catalog for Earthquakes; (JUICE), which can be used to evaluate the geometry and seismogenic depth of active faults in Japan. We relocated > 1.1 million hypocenters from the NIED Hi-net catalog for events which occurred between January 2001 and December 2012, to a depth of 40 km. We apply a relative hypocenter determination method to the data in each grid square, in which entire Japan is divided into 1257 grid squares to parallelize the relocation procedure. We used a double-difference method, incorporating cross-correlating differential times as well as catalog differential times. This allows us to resolve, in detail, a seismicity distribution for the entire Japanese Islands. We estimated location uncertainty by a statistical resampling method, using Jackknife samples, and show that the uncertainty can be within 0.37 km in the horizontal and 0.85 km in the vertical direction with a 90% confidence interval for areas with good station coverage. Our seismogenic depth estimate agrees with the lower limit of the hypocenter distribution for a recent earthquake on the Kamishiro fault (2014, Mj 6.7), which suggests that the new catalog should be useful for estimating the size of future earthquakes for inland active faults.
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Research on the spatial analysis method of seismic hazard for island
NASA Astrophysics Data System (ADS)
Jia, Jing; Jiang, Jitong; Zheng, Qiuhong; Gao, Huiying
2017-05-01
Seismic hazard analysis(SHA) is a key component of earthquake disaster prevention field for island engineering, whose result could provide parameters for seismic design microscopically and also is the requisite work for the island conservation planning’s earthquake and comprehensive disaster prevention planning macroscopically, in the exploitation and construction process of both inhabited and uninhabited islands. The existing seismic hazard analysis methods are compared in their application, and their application and limitation for island is analysed. Then a specialized spatial analysis method of seismic hazard for island (SAMSHI) is given to support the further related work of earthquake disaster prevention planning, based on spatial analysis tools in GIS and fuzzy comprehensive evaluation model. The basic spatial database of SAMSHI includes faults data, historical earthquake record data, geological data and Bouguer gravity anomalies data, which are the data sources for the 11 indices of the fuzzy comprehensive evaluation model, and these indices are calculated by the spatial analysis model constructed in ArcGIS’s Model Builder platform.
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NASA Astrophysics Data System (ADS)
Farrugia, D.; Galea, P. M.; D'Amico, S.
2016-12-01
The Maltese archipelago is characterised by a four layer sequence of limestones and clays. The Lower Coralline Limestone is the oldest exposed layer, overlain by the Globigerina Limestone. Some parts of the islands are characterised by Upper Coralline Limestone plateaus and hillcaps covering a soft Blue Clay layer which can be up to 75 m thick. The BC layer introduces a velocity inversion in the stratigraphy, and makes the Vs30 parameter not always suitable for seismic microzonation purposes. Such a layer may still produce amplification effects, however would not contribute to the numerical mean of Vs in the upper 30m. In this study, site response analysis for the Maltese islands is conducted, with particular attention being given to sites described above. Array and single-station measurements of ambient noise were first carried out at numerous sites in Malta. Surface wave dispersion and H/V curves were jointly inverted using a genetic algorithm, so that the Vs profiles were obtained. The stochastic extended-fault algorithm EXSIM was used to simulate historical and recent earthquakes at the bedrock. These were used in conjunction with the equivalent-linear programme SHAKE2000 to carry out the site-specific response analysis, using the derived geophysical models. Maps of ground motion parameters, such as peak ground acceleration and spectral accelerations, confirm that the clay, even when buried under a hard outcropping layer can still produce significant amplifications at frequencies which are of engineering interest when considering the recent urbanisation patterns. The results of this project will give important, and previously unavailable information and predictions about the behaviour of local lithotypes in response to earthquake ground shaking while also contributing knowledge about the issue of buried low velocity layers.
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NASA Astrophysics Data System (ADS)
Rooper, Christopher N.; Wilkins, Mark E.; Rose, Craig S.; Coon, Catherine
2011-11-01
The abundance of some marine fish species are correlated to the abundance of habitat-forming benthic organisms such as sponges and corals. A concern for fisheries management agencies is the recovery of these benthic invertebrates from removal or mortality from bottom trawling and other commercial fisheries activities. Using a logistic model, observations of available substrate and data from bottom trawl surveys of the Aleutian Islands, Alaska, we estimated recovery rates of sponges and corals following removal. The model predicted the observed sponge and coral catch in bottom trawl surveys relatively accurately ( R2=0.38 and 0.46). For sponges, the results show that intrinsic growth rates were slow ( r=0.107 yr -1). Results show that intrinsic growth rates of corals were also slow ( r=0.062 yr -1). The best models for corals and sponges were models that did not include the impacts of commercial fishing removals. Subsequent recovery times for both taxa were also predicted to be slow. Mortality of 67% of the initial sponge biomass would recover to 80% of the original biomass after 20 years, while mortality of 67% of the coral biomass would recover to 80% of the original biomass after 34 years. The modeled recovery times were consistent with previous studies in estimating that recovery times were of the order of decades, however improved data from directed studies would no doubt improve parameter estimates and reduce the uncertainty in the model results. Given their role as a major ecosystem component and potential habitat for marine fish, damage and removal of sponges and corals must be considered when estimating the impacts of commercial bottom trawling on the seafloor.
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New constraints on subduction inputs and volatile outputs along the Aleutian Arc
NASA Astrophysics Data System (ADS)
Lopez, T. M.; Fischer, T. P.; Plank, T. A.; Rizzo, A. L.; Rasmussen, D. J.; Cottrell, E.; Werner, C. A.; Kern, C.; Ilanko, T.; Buff, L.; Andrys, J.; Kelley, K. A.
2017-12-01
Volatile cycling drives volcanism in subduction zone settings. At arcs, volatiles can originate from the subducted slab, mantle wedge and/or crust. Each region has characteristic isotopic signatures, which can be used to fingerprint volatile provenance. We speculate that differences in subduction parameters, such as convergence angle, plate coupling and subducted sediment fluxes, may lead to differences in volatile provenance, which may in turn influence volcanic eruption style and frequency. Here we combine updated constraints on subduction inputs and volatile outputs to provide new insights into volatile cycling within the Aleutian Arc. The high proportion of organic carbon (80-100% to total carbon) in sediments subducting at the Aleutian trench stands out globally and predicts a light carbon isotopic composition of recycled volcanic fluids. We assess volatile outputs on volcanic timescales and along the arc by combining carbon (C), nitrogen (N) and helium (He) isotopic compositions of volcanic gases and new analyses of He and, where possible, C isotopes in olivine-hosted fluid inclusions. From our preliminary isotopic analyses of volcanic gases, we find a greater proportion of mantle-derived volatiles released from the Western segment of the Aleutian Arc (>40% mantle) compared with other volcanic arcs around the world (<30% mantle), where volatiles are sourced primarily from subducted or upper crustal carbonates. This trend may be due to the oblique convergence and low subducted sediment input in this region. The Aleutian Arc also exhibits among the lightest carbon isotope ratios of arcs worldwide (δ13C = -10 to -15‰), especially in the central part of the arc, where organic-bearing terrigneous sediment fills the trench and the convergence rate is high. New constraints on subduction inputs and outputs presented here will help discriminate between upper crustal and subducted carbon sources, and provide further insights into volatile cycling and subduction
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Feasibility Study of Earthquake Early Warning in Hawai`i For the Mauna Kea Thirty Meter Telescope
NASA Astrophysics Data System (ADS)
Okubo, P.; Hotovec-Ellis, A. J.; Thelen, W. A.; Bodin, P.; Vidale, J. E.
2014-12-01
Earthquakes, including large damaging events, are as central to the geologic evolution of the Island of Hawai`i as its more famous volcanic eruptions and lava flows. Increasing and expanding development of facilities and infrastructure on the island continues to increase exposure and risk associated with strong ground shaking resulting from future large local earthquakes. Damaging earthquakes over the last fifty years have shaken the most heavily developed areas and critical infrastructure of the island to levels corresponding to at least Modified Mercalli Intensity VII. Hawai`i's most recent damaging earthquakes, the M6.7 Kiholo Bay and M6.0 Mahukona earthquakes, struck within seven minutes of one another off of the northwest coast of the island in October 2006. These earthquakes resulted in damage at all thirteen of the telescopes near the summit of Mauna Kea that led to gaps in telescope operations ranging from days up to four months. With the experiences of 2006 and Hawai`i's history of damaging earthquakes, we have begun a study to explore the feasibility of implementing earthquake early warning systems to provide advanced warnings to the Thirty Meter Telescope of imminent strong ground shaking from future local earthquakes. One of the major challenges for earthquake early warning in Hawai`i is the variety of earthquake sources, from shallow crustal faults to deeper mantle sources, including the basal decollement separating the volcanic pile from the ancient oceanic crust. Infrastructure on the Island of Hawai`i may only be tens of kilometers from these sources, allowing warning times of only 20 s or less. We assess the capability of the current seismic network to produce alerts for major historic earthquakes, and we will provide recommendations for upgrades to improve performance.
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Gochfeld, Michael
2014-01-01
We analyzed arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in the feathers of common eiders (Somateria mollissima) and tufted puffins (Fratercula cirrhata) from Amchitka and Kiska islands (Aleutians). Between species, puffins had 10 times higher chromium (arithmetic mean = 1820 ppb), 7.5 times higher selenium (mean = 6600 ppb), and 3 times higher mercury (mean = 2540 ppb) than eiders. Eiders had significantly higher levels of manganese than puffins. Puffins are higher on the food chain than eiders, which is reflected in their generally higher levels of metals in their feathers. Interisland differences were generally small, and there were few significant differences as a function of the three nuclear test locations on Amchitka. The only sex-related difference was that female puffins had higher mercury than males (arithmetic mean of 3060 ppb vs. 2270 ppb). Mean levels of metals in the feathers of puffins and eiders from the Aleutians were low compared with comparable studies elsewhere, and the relatively low levels of metals do not indicate the potential for adverse behavioral or reproductive effects in the birds themselves, nor pose concern for other consumers, including subsistence hunters. PMID:18712499
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Station corrections for the Katmai Region Seismic Network
Searcy, Cheryl K.
2003-01-01
Most procedures for routinely locating earthquake hypocenters within a local network are constrained to using laterally homogeneous velocity models to represent the Earth's crustal velocity structure. As a result, earthquake location errors may arise due to actual lateral variations in the Earth's velocity structure. Station corrections can be used to compensate for heterogeneous velocity structure near individual stations (Douglas, 1967; Pujol, 1988). The HYPOELLIPSE program (Lahr, 1999) used by the Alaska Volcano Observatory (AVO) to locate earthquakes in Cook Inlet and the Aleutian Islands is a robust and efficient program that uses one-dimensional velocity models to determine hypocenters of local and regional earthquakes. This program does have the capability of utilizing station corrections within it's earthquake location proceedure. The velocity structures of Cook Inlet and Aleutian volcanoes very likely contain laterally varying heterogeneities. For this reason, the accuracy of earthquake locations in these areas will benefit from the determination and addition of station corrections. In this study, I determine corrections for each station in the Katmai region. The Katmai region is defined to lie between latitudes 57.5 degrees North and 59.00 degrees north and longitudes -154.00 and -156.00 (see Figure 1) and includes Mount Katmai, Novarupta, Mount Martin, Mount Mageik, Snowy Mountain, Mount Trident, and Mount Griggs volcanoes. Station corrections were determined using the computer program VELEST (Kissling, 1994). VELEST inverts arrival time data for one-dimensional velocity models and station corrections using a joint hypocenter determination technique. VELEST can also be used to locate single events.
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NASA Astrophysics Data System (ADS)
Yang, Ting; Gurnis, Michael; Zhan, Zhongwen
2017-07-01
The subducted old and cold Pacific Plate beneath the young Philippine Sea Plate at the Izu-Bonin trench over the Cenozoic hosts regional deep earthquakes. We investigate slab morphology and stress regimes under different trench motion histories with mantle convection models. Viscosity, temperature, and deviatoric stress are inherently heterogeneous within the slab, which we link to the occurrence of isolated earthquakes. Models expand on previous suggestions that observed slab morphology variations along the Izu-Bonin subduction zone, exhibited as shallow slab dip angles in the north and steeper dip angles in the south, are mainly due to variations in the rate of trench retreat from the north (where it is fast) to the south (where it is slow). Geodynamic models consistent with the regional plate tectonics, including oceanic plate age, plate convergence rate, and trench motion history, reproduce the seismologically observed principal stress direction and slab morphology. We suggest that the isolated 680 km deep, 30 May 2015 Mw 7.9 Bonin Islands earthquake, which lies east of the well-defined Benioff zone and has its principal compressional stress direction oriented toward the tip of the previously defined Benioff zone, can be explained by Pacific slab buckling in response to the slow trench retreat.
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NASA Astrophysics Data System (ADS)
Lee, C. J.; Cakir, R.; Walsh, T. J.; LeVeque, R. J.; Adams, L. M.; Gonzalez, F. I.
2016-12-01
The Strait of Juan de Fuca and adjacent coastal zone are prone to tsunami hazard triggered by a M9+ Cascadia Subduction Zone (CSZ) earthquake. In addition to the numerous tsunami deposits observed on the outer coast, there is geological evidence for nine sandy or muddy tsunami layers deposited in last 2500-year period in a tidal marsh area of Discovery Bay, Northeastern Olympic Peninsula, Washington (Williams et al., 2005, The Holocene, v. 15, no. 1). Thus, it is important to assess the potential tsunami hazard due to a future M9+ CSZ earthquake event that may impact local communities in and near Discovery Bay area . In this study, we conducted tsunami simulations using Clawpack-GeoClaw and the earthquake source scenario M9.1 CSZ, designated as "L1" (Witter et al., 2011, Oregon DOGAMI Special Paper 43). A fine-resolution (1/3 arc-second) NOAA digital elevation model (DEM) was used to provide a high resolution tsunami inundation simulation in Sequim Bay (about 5 miles west of Discovery Bay), Clallam county and Lopez Island, San Juan County. The test gauges, set around major infrastructures and properties, provided estimates of wave height, wave velocity, and wave arrival time. The results will contribute to further improving mitigation planning and emergency response efforts of the counties.
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Hayes, Gavin P.; Furlong, Kevin P.; Benz, Harley M.; Herman, Matthew W.
2014-01-01
Aseismic or slow slip events have been observed in many subduction zones, but whether they affect the occurrence of earthquakes or result from stress changes caused by nearby events is unclear. In an area lacking direct geodetic observations, inferences can be made from seismological studies of co-seismic slip, associated stress changes and the spatiotemporal nature of aftershocks. These observations indicate that the February 2013 Mw 8.0 Santa Cruz Islands earthquake may have triggered slow or aseismic slip on an adjacent section of the subduction thrust over the following hours to days. This aseismic event was equivalent to Mw 7.6, significantly larger than any earthquakes in the aftershock sequence. The aseismic slip was situated within the seismogenic portion of the subduction interface, and must have occurred to the south of the main seismic slip and most aftershocks in order to promote right-lateral faulting in the upper plate, the dominant deformation style of the aftershock sequence. This plate boundary segment can support either stable sliding (aseismic) or stick-slip (seismic) deformation in response to different driving conditions. The complete lack of aftershocks on the thrust interface implies this pair of megathrust slip episodes (seismic and aseismic) released a substantial portion of the stored strain on the northernmost section of the Vanuatu subduction zone.
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NASA Astrophysics Data System (ADS)
Bernardino, M. J.; Hayes, G. P.; Dannemann, F.; Benz, H.
2012-12-01
One of the main missions of the United States Geological Survey (USGS) National Earthquake Information Center (NEIC) is the dissemination of information to national and international agencies, scientists, and the general public through various products such as ShakeMap and earthquake summary posters. During the summer of 2012, undergraduate and graduate student interns helped to update and improve our series of regional seismicity posters and regional tectonic summaries. The "Seismicity of the Earth (1900-2007)" poster placed over a century's worth of global seismicity data in the context of plate tectonics, highlighting regions that have experienced great (M+8.0) earthquakes, and the tectonic settings of those events. This endeavor became the basis for a series of more regionalized seismotectonic posters that focus on major subduction zones and their associated seismicity, including the Aleutian and Caribbean arcs. The first round of these posters were inclusive of events through 2007, and were made with the intent of being continually updated. Each poster includes a regional tectonic summary, a seismic hazard map, focal depth cross-sections, and a main map that illustrates the following: the main subduction zone and other physiographic features, seismicity, and rupture zones of historic great earthquakes. Many of the existing regional seismotectonic posters have been updated and new posters highlighting regions of current seismological interest have been created, including the Sumatra and Java arcs, the Middle East region and the Himalayas (all of which are currently in review). These new editions include updated lists of earthquakes, expanded tectonic summaries, updated relative plate motion vectors, and major crustal faults. These posters thus improve upon previous editions that included only brief tectonic discussions of the most prominent features and historic earthquakes, and which did not systematically represent non-plate boundary faults. Regional tectonic
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Earthquake relocation near the Leech River Fault, southern Vancouver Island
NASA Astrophysics Data System (ADS)
Li, G.; Liu, Y.; Regalla, C.
2015-12-01
The Leech River Fault (LRF), a northeast dipping thrust, extends across the southern tip of Vancouver Island in Southwest British Columbia, where local tectonic regime is dominated by the subduction of the Juan de Fuca plate beneath the North American plate at the present rate of 40-50 mm/year. British Columbia geologic map (Geoscience Map 2009-1A) shows that this area also consists of many crosscutting minor faults in addition to the San Juan Fault north of the LRF. To investigate the seismic evidence of the subsurface structures of these minor faults and of possible hidden active structures in this area, precise earthquake locations are required. In this study, we relocate 941 earthquakes reported by Canadian National Seismograph Network (CNSN) catalog from 2000 to 2015 within a 100km x 55km study area surrounding the LRF. We use HypoDD [Waldhauser, F., 2001] double-difference relocation method by combining P/S phase arrivals provided by the CNSN at 169 stations and waveform data with correlation coefficient values greater than 0.7 at 50 common stations and event separation less than 10km. A total of 900 out of the 931 events satisfy the above relocation criteria. Velocity model used is a 1-D model extracted from the Ramachandran et al. (2005) model. Average relative location errors estimated by the bootstrap method are 546.5m (horizontal) and 1128.6m (in depth). Absolute errors reported by SVD method for individual clusters are ~100m in both dimensions. We select 5 clusters visually according to their epicenters (see figure). Cluster 1 is parallel to the LRF and a thrust FID #60. Clusters 2 and 3 are bounded by two faults: FID #75, a northeast dipping thrust marking the southwestern boundary of the Wrangellia terrane, and FID #2 marking the northern boundary. Clusters 4 and 5, to the northeast and northwest of Victoria respectively, however, do not represent the surface traces of any mapped faults. The depth profile of Cluster 5 depicts a hidden northeast
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Proceedings of the North Aleutian Basin information status and research planning meeting.
DOE Office of Scientific and Technical Information (OSTI.GOV)
LaGory, K. E.; Krummel, J. R.; Hayse, J. W.
2007-10-26
The North Aleutian Basin Planning Area of the Minerals Management Service (MMS) is a large geographic area with significant ecological and natural resources. The Basin includes most of the southeastern part of the Bering Sea continental shelf including all of Bristol Bay. The area supports important habitat for a wide variety of species and globally significant habitat for birds and marine mammals including federally listed species. Villages and communities of the Alaska Peninsula and other areas bordering or near the Basin rely on its natural resources (especially commercial and subsistence fishing) for much of their sustenance and livelihood. The offshoremore » area of the North Aleutian Basin is considered to have important hydrocarbon reserves, especially natural gas. In 2006, the MMS released a draft proposed program, Outer Continental Shelf Oil and Gas Leasing Program, 2007-2012 and an accompanying draft programmatic environmental impact statement (EIS). The draft proposed program identified two lease sales proposed in the North Aleutian Basin in 2010 and 2012, subject to restrictions. The area proposed for leasing in the Basin was restricted to the Sale 92 Area in the southwestern portion. Additional EISs will be needed to evaluate the potential effects of specific lease actions, exploration activities, and development and production plans in the Basin. A full range of updated multidisciplinary scientific information will be needed to address oceanography, fate and effects of oil spills, marine ecosystems, fish, fisheries, birds, marine mammals, socioeconomics, and subsistence in the Basin. Scientific staff at Argonne National Laboratory (Argonne) were contracted to assist the MMS Alaska Outer Continental Shelf (OCS) Region in identifying and prioritizing information needs related to the North Aleutian Basin and potential future oil and gas leasing and development activities. The overall approach focused on three related but separate tasks: (1
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Swarms of repeating long-period earthquakes at Shishaldin Volcano, Alaska, 2001-2004
Petersen, Tanja
2007-01-01
During 2001–2004, a series of four periods of elevated long-period seismic activity, each lasting about 1–2 months, occurred at Shishaldin Volcano, Aleutian Islands, Alaska. The time periods are termed swarms of repeating events, reflecting an abundance of earthquakes with highly similar waveforms that indicate stable, non-destructive sources. These swarms are characterized by increased earthquake amplitudes, although the seismicity rate of one event every 0.5–5 min has remained more or less constant since Shishaldin last erupted in 1999. A method based on waveform cross-correlation is used to identify highly repetitive events, suggestive of spatially distinct source locations. The waveform analysis shows that several different families of similar events co-exist during a given swarm day, but generally only one large family dominates. A network of hydrothermal fractures may explain the events that do not belong to a dominant repeating event group, i.e. multiple sources at different locations exist next to a dominant source. The dominant waveforms exhibit systematic changes throughout each swarm, but some of these waveforms do reappear over the course of 4 years indicating repeatedly activated source locations. The choked flow model provides a plausible trigger mechanism for the repeating events observed at Shishaldin, explaining the gradual changes in waveforms over time by changes in pressure gradient across a constriction within the uppermost part of the conduit. The sustained generation of Shishaldin's long-period events may be attributed to complex dynamics of a multi-fractured hydrothermal system: the pressure gradient within the main conduit may be regulated by temporarily sealing and reopening of parallel flow pathways, by the amount of debris within the main conduit and/or by changing gas influx into the hydrothermal system. The observations suggest that Shishaldin's swarms of repeating events represent time periods during which a dominant source
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Weather as the Decisive Factor of the Aleutian Campaign, June 1942 - August 1943
1993-01-01
examine the effect of weather on the living and fighting conditions during the campaign. The Delimitations The study will not examine prewar...airstrip the engineers drained and filled a flooded tidal basin . 52 An innovation available to the Americans and not Japan or Germany was "Marston mat...p, 47. 30 See Aleutians Cawnpaign, p. 87; Army Air Force in World War II, Vol 4, p. 383. ൯ See Aleutians Campaign, pp. 88-89; Argy Air Force in
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Damages in American Samoa due to the 29 September 2009 Samoa Islands Region Earthquake Tsunami
NASA Astrophysics Data System (ADS)
Okumura, Y.; Takahashi, T.; Suzuki, S.
2009-12-01
A large earthquake of Mw 8.0 occurred in Samoa Islands Region in the early morning on 29 September 2009 (local time). A Large Tsunami generated by the earthquake hit Samoa, American Samoa, Tonga. Total 192 people were died or missing in these three countries (22 October 2009). The authors surveyed in Tutuila Island, American Samoa from 6 to 8 in October 2009 with the aim to find out damages in the disaster. In American Samoa, death and missing toll was 35. The main findings are as follows; first, human damages were little for tsunami run-up height of about 4 to 6 meters and tsunami arrival time of about 20 minutes. We can suppose that residents evacuated quickly after feeling shaking or something. Secondly, houses were severely damaged in some low elevation coastal villages such as Amanave, Leone, Pago Pago, Tula and so on. Third, a power plant and an airport, which are important infrastructures in relief and recovery phase, were also severely damaged. Inundation depth at the power plant was 2.31 meters. A blackout in the daytime lasted when we surveyed. On the other hand, the airport could use already at that time. But it was closed on the first day in the disaster because of a lot of disaster debris on the runway carried by tsunami. Inundation depth at the airport fence was measured in 0.7 to 0.8 meters. Other countries in the south-western Pacific region may have power plants or airports with similar risk, so it should be assessed against future tsunami disasters. Inundated thermal power plant in Pago Pago Debris on runway in Tafuna Airport (Provided by Mr. Chris Soti, DPA)
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Uplift and Subsidence Associated with the Great Aceh-Andaman Earthquake of 2004
NASA Technical Reports Server (NTRS)
2006-01-01
The magnitude 9.2 Indian Ocean earthquake of December 26, 2004, produced broad regions of uplift and subsidence. In order to define the lateral extent and the downdip limit of rupture, scientists from Caltech, Pasadena, Calif.; NASA's Jet Propulsion Laboratory, Pasadena, Calif.; Scripps Institution of Oceanography, La Jolla, Calif.; the U.S. Geological Survey, Pasadena, Calif.; and the Research Center for Geotechnology, Indonesian Institute of Sciences, Bandung, Indonesia; first needed to define the pivot line separating those regions. Interpretation of satellite imagery and a tidal model were one of the key tools used to do this. These pre-Sumatra earthquake (a) and post-Sumatra earthquake (b) images of North Sentinel Island in the Indian Ocean, acquired from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft, show emergence of the coral reef surrounding the island following the earthquake. The tide was 30 plus or minus 14 centimeters lower in the pre-earthquake image (acquired November 21, 2000) than in the post-earthquake image (acquired February 20, 2005), requiring a minimum of 30 centimeters of uplift at this locality. Observations from an Indian Coast Guard helicopter on the northwest coast of the island suggest that the actual uplift is on the order of 1 to 2 meters at this site. In figures (c) and (d), pre-earthquake and post-earthquake ASTER images of a small island off the northwest coast of Rutland Island, 38 kilometers east of North Sentinel Island, show submergence of the coral reef surrounding the island. The tide was higher in the pre-earthquake image (acquired January 1, 2004) than in the post-earthquake image (acquired February 4, 2005), requiring subsidence at this locality. The pivot line must run between North Sentinel and Rutland islands. Note that the scale for the North Sentinel Island images differs from that for the Rutland Island images. The tidal model used -
Poly IC therapy in aleutian disease of mink.
Russell, A S; Percy, J S; Cho, H J
1975-01-01
Twenty-four virgin female aleutian mink were infected with aleutian disease agent and after 24 hours, 12 of these were treated with a course of polyinosinic acid-polycytidilic acid (Poly IC) injections. After six weeks the gammaglobulin level was significantly lower in the treated group but at 12 weeks this difference was no longer present. Four of the treated mink had normal target organ histology when killed at 20 weeks. The untreated group all showed moderate to marked changes but this difference was not statistically significant. There was a marked increase in the reactive lymphocyte blastogenesis index during the first weeks of infection and the phytohaemagglutinin response was seen to fall progressively. The antiglobulin reaction usually became positive after infection but neither antinuclear nor antierythrocyte antibodies were found. Precipitating antibodies to several polynucleotides were frequently present and were unrelated to infection or to Poly IC treatment. Images Fig. 1. Fig. 2A Fig. 2B. PMID:1095164
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Assessment of earthquake effects - contribution from online communication
NASA Astrophysics Data System (ADS)
D'Amico, Sebastiano; Agius, Matthew; Galea, Pauline
2014-05-01
The rapid increase of social media and online newspapers in the last years have given the opportunity to make a national investigation on macroseismic effects on the Maltese Islands based on felt earthquake reports. A magnitude 4.1 earthquake struck close to Malta on Sunday 24th April 2011 at 13:02 GMT. The earthquake was preceded and followed by a series of smaller magnitude quakes throughout the day, most of which were felt by the locals on the island. The continuous news media coverage during the day and the extensive sharing of the news item on social media resulted in a strong public response to fill in the 'Did you feel it?' online form on the website of the Seismic Monitoring and Research Unit (SMRU) at the University of Malta (http://seismic.research.um.edu.mt/). The results yield interesting information about the demographics of the island, and the different felt experiences possibly relating to geological settings and diverse structural and age-classified buildings. Based on this case study, the SMRU is in the process of developing a mobile phone application dedicated to share earthquake information to the local community. The application will automatically prompt users to fill in a simplified 'Did you feel it?' report to potentially felt earthquakes. Automatic location using Global Positioning Systems can be incorporated to provide a 'real time' intensity map that can be used by the Civil Protection Department.
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Luzon earthquake strongest in 90 years
NASA Astrophysics Data System (ADS)
The magnitude 7.7 Philippine earthquake that took place 2 weeks ago was the strongest recorded on the island of Luzon in nearly 90 years and the strongest in all of the Philippines in nearly 14 years, according to the U.S. Geological Survey.The earthquake occurred 60 miles north of Manila and was the third strongest recorded on Luzon, exceeded only by an earthquake with an estimated magnitude of 7.8, on December 14, 1901, near Lucena, about 80 miles southeast of Manila, and an earthquake with an estimated magnitude of 7.9 on August 15, 1897, off the northwest coast of Luzon.
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Kachadoorian, Reuben; Plafker, George
1967-01-01
The great earthquake (Richter magnitude of 8.4–8.5) that struck south-central Alaska at 5:36 p.m., Alaska standard time, on March 27, 1964 (03:36, March 28, Greenwich mean time), was felt in every community on Kodiak Island and the nearby islands. It was the most severe earthquake to strike this part of Alaska in modern time, and took the lives of 18 persons in the area by drowning; this includes two in Kodiak and three at Kaguyak. Property damage and loss of income to the communities is estimated at more than $45 million. The largest community, Kodiak, had the greatest loss from the earthquake. Damage was caused chiefly by 5.6 feet of tectonic subsidence and a train of 10 seismic sea waves that inundated the low-lying areas of the town. The seismic sea waves destroyed all but one of the docking facilities and more than 215 structures; many other structures were severely damaged. The waves struck the town during the evening hours of March 27 and early morning hours of March 28. They moved from the southwest and northeast: and reached their maximum height of 20–30 feet above mean lower low water at Shahafka Cove between 11:00 and 11:45 p.m., March 27. The violently destructive seismic sea waves not only severely damaged homes, shops, and naval-station structures but also temporarily crippled the fishing industry in Kodiak by destroying the processing plants and most of the fishing vessels. The waves scoured out 10 feet of sediments in the channel between Kodiak Island and Near Island and exposed bedrock. This bedrock presented a major post-earthquake construction problem because no sediments remained into which piles could be driven for foundations of waterfront facilities. Because of tectonic subsidence, high tides now flood Mission and Potatopatch Lakes which, before the earthquake, had not been subject to tidal action. The subsidence also accelerated erosion of the unconsolidated sediments along the shoreline in the city of Kodiak. Seismic shaking lasted 4
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Photointerpretation of Alaskan post-earthquake photography
Hackman, R.J.
1965-01-01
Aerial photographs taken after the March 27, 1964, Good Friday, Alaskan earthquake were examined stereoscopically to determine effects of the earthquake in areas remote from the towns, highways, and the railroad. The two thousand black and white photographs used in this study were taking in April, after the earthquake, by the U. S. Coast & Geodetic Survey and were generously supplied to the U. S. Geological Survey. Part of the photographs, at a scale of 1/24,000, provide blanket coverage of approximately 2,000 square miles of land area north and west of Prince William Sound, including parts of the mainland and some of the adjacent islands. The epicenter of the earthquake, near the head of Unakwik Inlet, is located in this area. The rest of the photographs, at scales ranging from 1/17,000 to 1/40,000, cover isolated strips of the coastline of the mainland and nearby islands in the general area of Prince William Sound. Figure 1 shows the area of new photo coverage used in this study. The objective of the study was to determine quickly whether geological features resulting from the earthquake, such as faults, changes in shoreline, cracks in surficial material, pressure ridges in lake ice, fractures in glaciers and lake ice, and rock slides and avalanches, might be identifiable by photointerpretation. The study was made without benefit of comparisons with older, or pre-earthquake photography, which was not readily available for immediate use.
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NASA Astrophysics Data System (ADS)
Spieker, Kathrin; Rondenay, Stéphane; Sawade, Lucas
2016-04-01
The Circum-Pacific belt, also called the Pacific Ring of Fire, is the most seismically active region on Earth. Multiple plate boundaries form a zone characterized by frequent volcanic eruptions and seismicity. While convergent plate boundaries such as the Peru-Chile trench dominate the Circum-Pacific belt, divergent and transform boundaries are present as well. The eastern section of the Circum-Pacific belt extends from the Aleutian arc, through the Cascadia subduction zone, San Andreas Fault, middle America trench and the Andean margin down to Tierra del Fuego. Due to the significant hazards posed by this tectonic activity, the region has been densely instrumented by thousands of seismic stations deployed across fifteen countries, over a distance of more than 15000 km. Various seismological studies, including receiver function analyses, have been carried out to investigate the crustal and mantle structure beneath local segments of the eastern Circum-Pacific belt (i.e., at ~100-500 km scale). However, to the best of our knowledge, no study to date has ever attempted to combine all available seismic data from the eastern Circum-Pacific belt to generate a continuous profile of seismic discontinuities extending from the Aleutians to Tierra del Fuego. Here, we use results from the "Global Imaging using Earthquake Records" (GLImER) P-wave receiver function database to create a long-range profile of crustal and upper mantle discontinuities across the entire eastern portion of the Circum-Pacific belt. We image intermittent crustal and mantle discontinuities along the profile, and examine them with regard to their behaviour and properties across transitions between different tectonic regimes.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Abers, G.A.
1994-03-10
Free-air gravity highs over forearcs represent a large fraction of the power in the Earth`s anomalous field, yet their origin remains uncertain. Seismic velocities, as indicators of density, are estimated here as a means to compare the relative importance of upper plate sources for the gravity high with sources in the downgoing plate. P and S arrival times for local earthquakes, recorded by a seismic network in the eastern Aleutians, are inverted for three-dimensional velocity structure between the volcanic arc and the downgoing plate. A three-dimensional ray tracing scheme is used to invert the 7974 P and 6764 S arrivalsmore » for seismic velocities and hypocenters of 635 events. One-dimensional inversions show that station P residuals are systematically 0.25 - 0.5 s positive at stations 0-30 km north of the Aleutian volcanic arc, indicating slow material, while residuals at stations 10-30 km south of the arc are 0.1-0.25 s negative. Both features are explained in three-dimensional inversions by velocity variations at depths less than 25-35 km. Tests using a one-dimensional or a two-dimensional slab starting model show that below 100 km depth, velocities are poorly determined and trade off almost completely with hypocenters for earthquakes at these depths. The locations of forearc velocity highs, in the crust of the upper plate, correspond to the location of the gravity high between the trench and volcanic arc. Free-air anomalies, calculated from the three-dimensional velocity inversion result, match observed gravity for a linear density-velocity relationship between 0.1 and 0.3 (Mg m{sup {minus}3})/(km s{sup {minus}1}), when a 50-km-thick slab is included with a density of 0.055{+-}0.005 Mg m{sup {minus}3}. Values outside these ranges do not match the observed gravity. The slab alone contributes one third to one half of the total 75-150 mGal amplitude of the gravity high but predicts a high that is much broader than is observed.« less
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Mortera-Gutierrez, C. A.; Scholl, D. W.; Carlson, R.L.
2003-01-01
Normal faults along the seaward trench slope (STS) commonly strike parallel to the trench in response to bending of the oceanic plate into the subduction zone. This is not the circumstance for the Aleutian Trench, where the direction of convergence gradually changes westward, from normal to transform motion. GLORIA side-scan sonar images document that the Aleutian STS is dominated by faults striking oblique to the trench, west of 179??E and east of 172??W. These images also show a pattern of east-west trending seafloor faults that are aligned parallel to the spreading fabric defined by magnetic anomalies. The stress-strain field along the STS is divided into two domains west and east, respectively, of 179??E. Over the western domain, STS faults and nodal planes of earthquakes are oriented oblique (9??-46??) to the trench axis and (69??-90??) to the magnetic fabric. West of 179??E, STS fault strikes change by 36?? from the E-W trend of STS where the trench-parallel slip gets larger than its orthogonal component of convergence. This rotation indicates that horizontal stresses along the western domain of the STS are deflected by the increasing obliquity in convergence. An analytical model supports the idea that strikes of STS faults result from a superposition of stresses associated with the dextral shear couple of the oblique convergence and stresses caused by plate bending. For the eastern domain, most nodal planes of earthquakes strike parallel to the outer rise, indicating bending as the prevailing mechanism causing normal faulting. East of 172??W, STS faults strike parallel to the magnetic fabric but oblique (10??-26??) to the axis of the trench. On the basis of a Coulomb failure criterion the trench-oblique strikes probably result from reactivation of crustal faults generated by spreading. Copyright 2003 by the American Geophysical Union.
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New earthquake catalog reexamines Hawaii's seismic history
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.
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Geist, Eric L.; Vallier, Tracy L.; Scholl, David W.
1994-01-01
consequence of either infra-oceanic transport or coastwise translation is that an open corridor between the western terminus of the Aleutian Arc and Kamchatka must have existed until middle to late Eocene time. Spreading within the Komandorsky Basin, subduction of sea-mounts, and collision of the Aleutian Arc with Kamchatka are proposed to have instigated the second Miocene phase of deformation, which uplifted and reexposed the island-arc terrane.
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Population genetic structure and conservation of marbled murrelets (Brachyramphus marmoratus)
Friesen, Vicki L.; Birt, T.P.; Piatt, John F.; Golightly, R.T.; Newman, S.H.; Hebert, P.N.; Congdon, B.C.; Gissing, G.
2005-01-01
Marbled murrelets (Brachyramphus marmoratus) are coastal seabirds that nest from California to the Aleutian Islands. They are declining and considered threatened in several regions. We compared variation in the mitochondrial control region, four nuclear introns and three microsatellite loci among 194 murrelets from throughout their range except Washington and Oregon. Significant population genetic structure was found: nine private control region haplotypes and three private intron alleles occurred at high frequency in the Aleutians and California; global estimates of FST or ??ST and most pairwise estimates involving the Aleutians and/or California were significant; and marked isolation-by-distance was found. Given the available samples, murrelets appear to comprise five genetic management units: (1) western Aleutian Islands, (2) central Aleutian Islands, (3) mainland Alaska and British Columbia, (4) northern California, and (5) central California.
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Land-level changes from a late Holocene earthquake in the northern Puget lowland, Washington
Kelsey, H.M.; Sherrod, B.; Johnson, S.Y.; Dadisman, S.V.
2004-01-01
An earthquake, probably generated on the southern Whidbey Island fault zone, caused 1-2 m of ground-surface uplift on central Whidbey Island ???2800-3200 yr ago. The cause of the uplift is a fold that grew coseismically above a blind fault that was the earthquake source. Both the fault and the fold at the fault's tip are imaged on multichannel seismic refection profiles in Puget Sound immediately east of the central Whidbey Island site. Uplift is documented through contrasting histories of relative sea level at two coastal marshes on either side of the fault. Late Holocene shallow-crustal earthquakes of Mw = 6.5-7 pose substantial seismic hazard to the northern Puget Lowland. ?? 2004 Geological Society of America.
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NASA Astrophysics Data System (ADS)
Taylor, F. W.; Lavier, L. L.; Bevis, M. G.; Thirumalai, K.; Frohlich, C. A.
2012-12-01
Over million-year time scales, what is the relationship between the meter-scale vertical displacements that occur in individual large subduction-zone earthquakes, and the observed topography and geology of island arcs? Because the geographic distribution of vertical displacements associated with the earthquake cycle sometimes mimics topography, it is tempting to assume that vertical deformation simply accrues as the coseismic part of the cycle that is preserved from one event to another. However, our research in the Central New Hebrides and Western Solomon arcs demonstrates that truly permanent tectonic deformation is a step farther removed from the earthquake cycle than we originally assumed. By precisely dating of coral reef terraces we are able to evaluate vertical deformation over time scales of 10,000 to 100,000 years. This analysis indicates that these arcs undergo episodes of hundreds of meters of subsidence and uplift over time scales of tens of thousands of years. Thus what remains in the geologic record is potentially providing invaluable information about more fundamental processes than the elastic earthquake cycle. These longer-term episodes of vertical motion may act in many arcs throughout the world, but evidence of them may be poorly preserved outside of tropical regions where corals along island coastlines provide a record of their occurrence.In our presentation we will describe the tectonic behavior observed in the Central New Hebrides and Western Solomons. We will speculate about some possible mechanisms that explain how the subduction process generates longer-term episodes of subsidence and uplift, and make suggestions about future observations that could better constrain the nature of these processes.
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Burger, Joanna
2007-11-01
World War II and the Cold War have left the Unites States, and other Nations, with massive cleanup and remediation tasks for radioactive and other legacy hazardous wastes. While some sites can be cleaned up to acceptable residential risk levels, others will continue to hold hazardous wastes, which must be contained and monitored to protect human health and the environment. While media (soil, sediment, groundwater) monitoring is the usual norm at many radiological waste sites, for some situations (both biological and societal), biomonitoring may provide the necessary information to assure greater peace of mind for local and regional residents, and to protect ecologically valuable buffer lands or waters. In most cases, indicators are selected using scientific expertise and a literature review, but not all selected indicators will seem relevant to stakeholders. In this paper, I provide a model for the inclusion of stakeholders in the development of bioindicators for assessing radionuclide levels of biota in the marine environment around Amchitka Island, in the Aleutian Chain of Alaska. Amchitka was the site of three underground nuclear tests from 1965 to 1971. The process was stakeholder-initiated, stakeholder-driven, and included stakeholders during each phase. Phases included conceptualization, initial selection of biota and radionuclides, refinement of biota and radionuclide target lists, collection of biota, selection of biota and radionuclides for analysis, and selection of biota, tissues, and radionuclides for bioindicators. The process produced site-specific information on biota availability and on radionuclide levels that led to selection of site-appropriate bioindicators. I suggest that the lengthy, iterative, stakeholder-driven process described in this paper results in selection of bioindicators that are accepted by biologists, public health personnel, public-policy makers, resource agencies, regulatory agencies, subsistence hunters/fishers, and a wide
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Dove, C.J.; Peurach, S.C.; Frohlich, Bruno; Harper, Albert B.; Gilberg, Rolf
2002-01-01
Human mummified remains of 34 different infant and adult individuals from Kagamil Island, Alaska, are accessioned in the Department of Anthropology, National Museum of Natural History, Smithsonian Institution. Kagamil Island is one of the small islands in the Island of Four Mountains group of the Aleutian Islands, Alaska and is well known for the mummy caves located on the southwest coast of the island. The Kagamil mummy holdings at the Smithsonian represent one of the largest, best documented and preserved collections of this type. Although these specimens are stored in ideal conditions, many small feather and hair fragments have become loose or disassociated from the actual mummies over the years. This preliminary investigation of fragmentary fiber material retrieved from these artifacts is the first attempt to identify bird and mammal species associated with the mummified remains of the Kagamil Island, Alaska collection and is part of the ongoing research connected with these artifacts.
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Estes, James A.; Tinker, M. Tim; Bodkin, James L.
2010-01-01
Recovery criteria for depleted species or populations normally are based on demographic measures, the goal being to maintain enough individuals over a sufficiently large area to assure a socially tolerable risk of future extinction. Such demographically based recovery criteria may be insufficient to restore the functional roles of strongly interacting species. We explored the idea of developing a recovery criterion for sea otters (Enhydra lutris) in the Aleutian archipelago on the basis of their keystone role in kelp forest ecosystems. We surveyed sea otters and rocky reef habitats at 34 island-time combinations. The system nearly always existed in either a kelp-dominated or deforested phase state, which was predictable from sea otter density. We used a resampling analysis of these data to show that the phase state at any particular island can be determined at 95% probability of correct classification with information from as few as six sites. When sea otter population status (and thus the phase state of the kelp forest) was allowed to vary randomly among islands, just 15 islands had to be sampled to estimate the true proportion that were kelp dominated (within 10%) with 90% confidence. We conclude that kelp forest phase state is a more appropriate, sensitive, and cost-effective measure of sea otter recovery than the more traditional demographically based metrics, and we suggest that similar approaches have broad potential utility in establishing recovery criteria for depleted populations of other functionally important species.
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NASA Astrophysics Data System (ADS)
Kato, T.; Ito, T.; Abidin, H. Z.; Agustan
2007-09-01
A large earthquake (Mw=7.7) along a plate boundary occurred in the south of Java Island on July 17, 2006, and caused a significant tsunami. We made GPS observations and tsunami heights measurements during the period from July 24 to August 1, 2006. The earthquake seems to be due to an interplate low angle reverse faulting, though there might be a possibility of high angle faulting within the subducting lithosphere. Crustal deformation distribution due to the earthquake, aided by tsunami heights measurements, might clarify which would be the case. We occupied 29 sites by GPS in the area of southern Java encompassing the area from 107.8 E to 109.50 E. These sites were occupied once before the earthquake. However, we were not able to detect significant co-seismic displacements. The obtained displacements, most of which span several years, show ESE direction in ITRF2000 frame. This represents the direction of Sunda block motion. The tsunami heights measured at 11 sites were 6-7 m along the southern coast of Java and indicate that the observed heights are systematically higher than those estimated from numerical simulations that are based on seismic data analysis. This might suggest that fault offsets might have been larger - nearly double - than those estimated using seismic analysis. These results lead us to an idea that the rupture was very slow. If this is the case, the earthquake might have been a "tsunami earthquake" that is similar to the one that occurred on June 2, 1994 in the east of the present earthquake.
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Megathrust Earthquakes and Sediment Input to the Subduction Channel
NASA Astrophysics Data System (ADS)
Scholl, David W.; Keranen, Katie; von Huene, Roland; Wells, Ray; Ryan, Holly; Kirby, Stephen
2010-05-01
HABITATS OF GREAT MEGATHRUST EARTHQUAKES: Great megathrust earthquakes (Mw8.5 or higher) most commonly (~65%) nucleate along subduction zones (SZ) bordered by laterally continuous (more than 500 km), sediment-flooded trenches. Examples include: south-central Chile (1922, Mw8.5; 1960, Mw9.5), eastern Alaska (1964, Mw9.2), Sumatra (2004, Mw9.1), Cascadia (1700, Mw9.0), Colombia (1906, Mw8.8), Sumatra (1883, Mw8.8), west-central Aleutian (1965, Mw8.7), central Aleutian (1986, Mw8.7), Sumatra (2005, Mw8.6), and Nankai (1707, Mw8.5). All known megathrust events greater than Mw9 ruptured at sediment-charged SZs (Alaska, S.C. Chile, Sumatra). Sediment entering high-seismicity SZs is typically a 1-3-km-thick wedge of trench-axis turbidite beds overlying a 0.3-2-km-thick sequence of hemipelagic or abyssal turbiditic deposits that accrued seaward of the trench. Most commonly, laterally-continuous turbidite wedges are built by down-axis flowing turbidity currents sourced from mountainous and/or glaciated drainages (e.g., SE Alaska, Cascadia, Southern Andes, Himalaya). Great rupture events also occur at SZs receiving little sediment, for example Kamchatka (1952, Mw9.0), Kuril Islands (1963, Mw8.5) and north Chile SZs (1868, Mw9.0). These SZs exhibit evidence of upper plate thinning, subsidence, and truncation effected by frontal and basal subduction erosion. They also have a SC filled with ~1 km or more of debris in transport toward the mantle. WORKINGS OF THE SUBDUCTION CHANNEL (SC): Beneath the submerged forearc, the SC functions to transport subducted ocean floor sediment and tectonically eroded forearc debris toward and ultimately into the mantle. The SC is the lowest structural unit containing upper plate crustal material and the seismogenic zone runs along the SC's upper boundary. It has long been conjectured (e.g., Ruff, 1989; PAGEOPH, v. 129. Nos 1/2) that a laterally uninterrupted, sediment- or debris-charged SC serves to smooth the surface of interplate slip to set
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Amchitka Island, Alaska, special sampling project 1997
DOE Office of Scientific and Technical Information (OSTI.GOV)
U.S. Department of Energy, Nevada Operations Office
2000-06-28
This 1997 special sampling project represents a special radiobiological sampling effort to augment the 1996 Long-Term Hydrological Monitoring Program (LTHMP) for Amchitka Island in Alaska. Lying in the western portion of the Aleutian Islands arc, near the International Date Line, Amchitka Island is one of the southernmost islands of the Rat Island Chain. Between 1965 and 1971, the U.S. Atomic Energy Commission conducted three underground nuclear tests on Amchitka Island. In 1996, Greenpeace collected biota samples and speculated that several long-lived, man-made radionuclides detected (i.e., americium-241, plutonium-239 and -240, beryllium-7, and cesium-137) leaked into the surface environment from underground cavitiesmore » created during the testing. The nuclides of interest are detected at extremely low concentrations throughout the environment. The objectives of this special sampling project were to scientifically refute the Greenpeace conclusions that the underground cavities were leaking contaminants to the surface. This was achieved by first confirming the presence of these radionuclides in the Amchitka Island surface environment and, second, if the radionuclides were present, determining if the source is the underground cavity or worldwide fallout. This special sampling and analysis determined that the only nonfallout-related radionuclide detected was a low level of tritium from the Long Shot test, which had been previously documented. The tritium contamination is monitored and continues a decreasing trend due to radioactive decay and dilution.« less
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What role did the Hikurangi subduction zone play in the M7.8 Kaikoura earthquake?
NASA Astrophysics Data System (ADS)
Wallace, L. M.; Hamling, I. J.; Kaneko, Y.; Fry, B.; Clark, K.; Bannister, S. C.; Ellis, S. M.; Francois-Holden, C.; Hreinsdottir, S.; Mueller, C.
2017-12-01
The 2016 M7.8 Kaikoura earthquake ruptured at least a dozen faults in the northern South Island of New Zealand, within the transition from the Hikurangi subduction zone (in the North Island) to the transpressive Alpine Fault (in the central South Island). The role that the southern end of the Hikurangi subduction zone played (or did not play) in the Kaikoura earthquake remains one of the most controversial aspects of this spectacularly complex earthquake. Investigations using near-field seismological and geodetic data suggest a dominantly crustal faulting source for the event, while studies relying on teleseismic data propose that a large portion of the moment release is due to rupture of the Hikurangi subduction interface beneath the northern South Island. InSAR and GPS data also show that a large amount of afterslip (up to 0.5 m) occurred on the subduction interface beneath the crustal faults that ruptured in the M7.8 earthquake, during the months following the earthquake. Modeling of GPS velocities for the 20 year period prior to the earthquake indicate that interseismic coupling was occurring on the Hikurangi subduction interface beneath the northern South Island, in a similar location to the suggested coseismic and postseismic slip on the subduction interface. We will integrate geodetic, seismological, tsunami, and geological observations in an attempt to balance the seemingly conflicting views from local and teleseismic data regarding the role that the southern Hikurangi subduction zone played in the earthquake. We will also discuss the broader implications of the observed coseismic and postseismic deformation for understanding the kinematics of the southern termination of the Hikurangi subduction zone, and its role in the transition from subduction to strike-slip in the central New Zealand region.
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The nearshore benthic community of Kasatochi Island, one year after the 2008 volcanic eruption
Jewett, S.C.; Bodkin, James L.; Chenelot, H.; Esslinger, George G.; Hoberg, M.K.
2010-01-01
A description is presented of the nearshore benthic community of Kasatochi Island 10–12 months after a catastrophic volcanic eruption in 2008. The eruption extended the coastline of the island approximately 400 m offshore, mainly along the south, southeast, and southwest shores, to roughly the 20 m isobath. Existing canopy kelp of Eualaria (Alaria) fistulosa, as well as limited understory algal species and associated fauna (e.g., urchin barrens) on the hard substratum were apparently buried following the eruption. Samples and observations revealed the substrate around the island in 2009 was comprised almost entirely of medium and coarse sands with a depauperate benthic community, dominated by opportunistic pontogeneiid amphipods. Comparisons of habitat and biological communities with other nearby Aleutian Islands, as well as with the Icelandic volcanic island of Surtsey, confirm dramatic reductions in flora and fauna consistent with an early stage of recovery from a large-scale disturbance event.
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The isolated ˜680 km deep 30 May 2015 MW 7.9 Ogasawara (Bonin) Islands earthquake
NASA Astrophysics Data System (ADS)
Ye, Lingling; Lay, Thorne; Zhan, Zhongwen; Kanamori, Hiroo; Hao, Jin-Lai
2016-01-01
Deep-focus earthquakes, located in very high-pressure conditions 300 to 700 km below the Earth's surface within sinking slabs of relatively cold oceanic lithosphere, are mysterious phenomena. The largest recorded deep-focus earthquake (MW 7.9) in the Izu-Bonin slab struck on 30 May 2015 beneath the Ogasawara (Bonin) Islands, isolated from prior seismicity by over 100 km in depth, and followed by only a few small aftershocks. Globally, this is the deepest (680 km centroid depth) event with MW ≥ 7.8 in the seismological record. Seismicity indicates along-strike contortion of the Izu-Bonin slab, with horizontal flattening near a depth of 550 km in the Izu region and rapid steepening to near-vertical toward the south above the location of the 2015 event. This event was exceptionally well-recorded by seismic stations around the world, allowing detailed constraints to be placed on the source process. Analyses of a large global data set of P, SH and pP seismic phases using short-period back-projection, subevent directivity, and broadband finite-fault inversion indicate that the mainshock ruptured a shallowly-dipping fault plane with patchy slip that spread over a distance of ∼40 km with a multi-stage expansion rate (∼ 5 + km /s down-dip initially, ∼3 km/s up-dip later). During the 17 s total rupture duration the radiated energy was ∼ 3.3 ×1016 J and the stress drop was ∼38 MPa. The radiation efficiency is moderate (0.34), intermediate to that of the 1994 Bolivia and 2013 Sea of Okhotsk MW 8.3 deep earthquakes, indicating that source processes of very large deep earthquakes sample a wide range of behavior from dissipative, more viscous failure to very brittle failure. The isolated occurrence of the event, much deeper than the apparently thermally-bounded distribution of Bonin-slab seismicity above 600 km depth, suggests that localized stress concentration associated with the pronounced deformation of the Izu-Bonin slab and proximity to the 660-km phase
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NASA Astrophysics Data System (ADS)
Wallace, Laura M.; Hreinsdóttir, Sigrún; Ellis, Susan; Hamling, Ian; D'Anastasio, Elisabetta; Denys, Paul
2018-05-01
The 2016 MW7.8 Kaikōura earthquake ruptured a complex sequence of strike-slip and reverse faults in New Zealand's northeastern South Island. In the months following the earthquake, time-dependent inversions of Global Positioning System and interferometric synthetic aperture radar data reveal up to 0.5 m of afterslip on the subduction interface beneath the northern South Island underlying the crustal faults that ruptured in the earthquake. This is clear evidence that the far southern end of the Hikurangi subduction zone accommodates plate motion. The MW7.8 earthquake also triggered widespread slow slip over much of the subduction zone beneath the North Island. The triggered slow slip included immediate triggering of shallow (<15 km), short (2-3 weeks) slow slip events along much of the east coast, and deep (>30 km), long-term (>1 year) slow slip beneath the southern North Island. The southern Hikurangi slow slip was likely triggered by large (0.5-1.0 MPa) static Coulomb stress increases.
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NASA Astrophysics Data System (ADS)
Kiratzi, Anastasia
2018-01-01
On 12 June 2017 (UTC 12:28:38.26) a magnitude Mw 6.3 earthquake occurred offshore Lesvos Island in SE Aegean Sea, which was widely felt, caused 1 fatality, and partially ruined the village of Vrisa on the south-eastern coast of the island. I invert broad band and strong motion waveforms from regional stations to obtain the source model and the distribution of slip onto the fault plane. The hypocentre is located at a depth of 7 km in the upper crust. The mainshock ruptured a WNW-ESE striking, SW dipping, normal fault, projecting offshore and bounding the Lesvos Basin. The strongest and most aftershocks clustered away from the hypocentre, at the eastern edge of the activated area. This cluster indicates the activation of a different fault segment, exhibiting sinistral strike-slip motions, along a plane striking WNW-ESE. The slip of the mainshock is confined in a single large asperity, WNW from the hypocentre, with dimensions 20 km × 10 km along fault strike and dip, respectively. The average slip of the asperity is 50 cm and the peak slip is 1 m. The rupture propagated unilaterally towards WNW to the coastline of Lesvos island at a relatively high speed ( 3.1 km/s). The imaged slip model and forward modelling was used to calculate peak ground velocities (PGVs) in the near-field. The damage pattern produced by this earthquake, especially in the village of Vrisa is compatible with the combined effect of rupture directivity, proximity to the slip patch and the fault edge, spectral content of motions, and local site conditions.
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Cascades/Aleutian Play Fairway Analysis: Data and Map Files
Lisa Shevenell
2015-11-15
Contains Excel data files used to quantifiably rank the geothermal potential of each of the young volcanic centers of the Cascade and Aleutian Arcs using world power production volcanic centers as benchmarks. Also contains shapefiles used in play fairway analysis with power plant, volcano, geochemistry and structural data.
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2013-12-30
On December 10, 2013 the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite flew across the central Atlantic Ocean and captured a true-color image of the Canary Islands. Lying off of the coast of Western Sahara and Morocco, the islands were created by successive submarine volcanic eruptions which raised the ocean floor vertically until some of land rose above sea level. The oldest islands lie in the east and the youngest in the west. From east to west, the major islands seen in this image are: Lanzarote, Fuerteventura, Gran Canaria, Tenerife, La Gomera, La Palmera and El Hierro. While the creation of the islands began in the Late Cretaceous Period (70 – 80 million years ago), active volcanic activity continues. In 2011, a spectacular submarine eruption occurred just off the shore of El Hierro. The volcano became quiet again, but very recently increasing earthquakes and changing height of El Hierro suggested the volcano may again be entering an active eruptive phase. On December 27 the island’s volcano monitoring agency had raised the volcanic eruption risk for El Hierro to “yellow” – a code that means increasing activity but no eruption imminent. That afternoon a magnitude 5.1 earthquake struck offshore at El Hierro. The epicenter was 9 miles (15 km) deep, and it was one of the largest quakes ever recorded at the island. Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
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Takahashi, Taeko Jane; Ikeda, Nancy A.; Okubo, Paul G.; Sako, Maurice K.; Dow, David C.; Priester, Anna M.; Steiner, Nolan A.
2011-01-01
Although the vast majority of earthquakes in the State of Hawaii are closely related to the active volcanism associated with the southeastern part of the Island of Hawai‘i, the October 2006 Kīholo Bay and Māhukona earthquakes clearly suggest the devastating potential of deeper lithospheric earthquakes. Large earthquakes thought to be nearly M7 have struck near the islands of Lāna‘i (1871) and Maui (1938). It is thought that these, like the 2006 earthquakes, were deep lithospheric flexure earthquakes (Wyss and Koyanagi, 1992; Klein and others, 2001). Thus, it is important to recognize the potential seismic hazard posed by such earthquakes beneath the older Hawaiian Islands. The data and observations afforded by the 2006 earthquakes promise to improve probabilistic seismic hazards modeling in Hawai‘i. The effects of the October 15, 2006, Kīholo Bay-Māhukona earthquakes are shown in images taken from the coastal route along the northern half of the Island of Hawai‘i, where damage was the most concentrated. The direction of presentation is counter-clockwise, from Pa‘auilo on the eastern or windward (Hāmākua) side to Kealakekua Bay on the western or leeward (Kona) side. A list of sites, their locations, coordinates, and distance from the epicenter at Kīholo Bay are given in table 1. A Google Earth map (fig. 7) and a topographic map (fig. 8) pinpoint the 36 sites where damage was documented and digital images were compiled for this collection.
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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
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Catalog of Hawaiian earthquakes, 1823-1959
Klein, Fred W.; Wright, Thomas L.
2000-01-01
This catalog of more than 17,000 Hawaiian earthquakes (of magnitude greater than or equal to 5), principally located on the Island of Hawaii, from 1823 through the third quarter of 1959 is designed to expand our ability to evaluate seismic hazard in Hawaii, as well as our knowledge of Hawaiian seismic rhythms as they relate to eruption cycles at Kilauea and Mauna Loa volcanoes and to subcrustal earthquake patterns related to the tectonic evolution of the Hawaiian chain.
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Photocopy of photograph (original located at Mare Island Archives). Original ...
Photocopy of photograph (original located at Mare Island Archives). Original photographer unknown. View of sawmill after earthquake of 1898. - Mare Island Naval Shipyard, East of Nave Drive, Vallejo, Solano County, CA
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Person, W.J.
1981-01-01
The months were seismically active, although only one major event (7.0-7.9) occurred in an unpopulated Philippine Island. Mexico was struck by a 6.3 quake on June 9 killing at least two people. The most significant earthquake in the United States was in the Mammoth Lakes area of California. -from Author
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Kenney, Leah A.; Eagles-Smith, Collin A.; Ackerman, Joshua T.; von Hippel, Frank A.
2014-01-01
We assessed temporal variation in mercury (Hg) concentrations of threespine stickleback (Gasterosteus aculeatus) from Agattu Island, Aleutian Archipelago, Alaska. Total Hg concentrations in whole-bodied stickleback were measured at two-week intervals from two sites in each of two lakes from June 1 to August 10, 2011 during the time period when lakes were ice-free. Across all sites and sampling events, stickleback Hg concentrations ranged from 0.37–1.07 µg/g dry weight (dw), with a mean (± SE) of 0.55±0.01 µg/g dw. Mean fish Hg concentrations declined by 9% during the study period, from 0.57±0.01 µg/g dw in early June to 0.52±0.01 µg/g dw in mid-August. Mean fish Hg concentrations were 6% higher in Loon Lake (0.56±0.01 µg/g dw) than in Lake 696 (0.53±0.01 µg/g dw), and 4% higher in males (0.56±0.01 µg/g dw) than in females (0.54±0.01 µg/g dw). Loon Lake was distinguished from Lake 696 by the presence of piscivorous waterbirds during the breeding season. Mercury concentrations in stickleback from Agattu Island were higher than would be expected for an area without known point sources of Hg pollution, and high enough to be of concern to the health of piscivorous wildlife.
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Anomalous Variation in GPS TEC, Land and Ocean Parameters Prior to 3 Earthquakes
NASA Astrophysics Data System (ADS)
Yadav, Kunvar; Karia, Sheetal P.; Pathak, Kamlesh N.
2016-02-01
The present study reports the analysis of GPS TEC prior to 3 earthquakes ( M > 6.0). The earthquakes are: (1) Loyalty Island (22°36'S, 170°54'E) on 19 January 2009 ( M = 6.6), (2) Samoa Island (15°29'S, 172°5'W) on 30 August 2009 ( M = 6.6), and (3) Tohoku (38°19'N, 142°22'E) on 11 March 2011 ( M = 9.0). In an effort to search for a precursory signature we analysed the land and ocean parameters prior to the earthquakes, namely SLHF (Land) and SST (Ocean). The GPS TEC data indicate an anomalous behaviour from 1-13 days prior to earthquakes. The main purpose of this study was to explore and demonstrate the possibility of any changes in TEC, SST, and SLHF before, during and after the earthquakes which occurred near or beneath an ocean. This study may lead to better understanding of response of land, ocean, and ionosphere parameters prior to seismic activities.
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NASA Astrophysics Data System (ADS)
Li, J.; Abers, G. A.; Christensen, D. H.; Kim, Y.; Calkins, J. A.
2011-12-01
Earthquakes in subduction zones are mostly generated at the interface between the subducting and overlying plates. In 2006-2009, the MOOS (Multidisciplinary Observations Of Subduction) seismic array was deployed around the Kenai Peninsula, Alaska, consisting of 34 broadband seismometers recording for 1-3 years. This region spans the eastern end of the Aleutian megathrust that ruptured in the 1964 Mw 9.2 great earthquake, the second largest recorded earthquake, and ongoing seismicity is abundant. Here, we report an initial analysis of seismicity recorded by MOOS, in the context of preliminary imaging. There were 16,462 events detected in one year from initial STA/LTA signal detections and subsequent event associations from the MOOS Array. We manually reviewed them to eliminate distant earthquakes and noise, leaving 11,879 local earthquakes. To refine this catalog, an adaptive auto-regressive onset estimation algorithm was applied, doubling the original dataset and producing 20,659 P picks and 22,999 S picks for one month (September 2007). Inspection shows that this approach lead to almost negligible false alarms and many more events than hand picking. Within the well-sampled part of the array, roughly 200 km by 300 km, we locate 250% more earthquakes for one month than the permanent network catalog, or 10 earthquakes per day on this patch of the megathrust. Although the preliminary locations of earthquakes still show some scatter, we can see a concentration of events in a ~20-km-wide belt, part of which can be interpreted as seismogenic thrust zone. In conjunction with the seismicity study, we are imaging the plate interface with receiver functions. The main seismicity zone corresponds to the top of a low-velocity layer imaged in receiver functions, nominally attributed to the top of the downgoing plate. As we refine velocity models and apply relative relocation algorithms, we expect to improve the precision of the locations substantially. When combined with image
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Bald eagles and sea otters in the Aleutian Archipelago: indirect effects of trophic cascades.
Anthony, R.G.; Estes, J.A.; Ricca, M.A.; Miles, A.K.; Forsman, E.D.
2008-01-01
Because sea otters (Enhydra lutris) exert a wide array of direct and indirect effects on coastal marine ecosystems throughout their geographic range, we investigated the potential influence of sea otters on the ecology of Bald Eagles (Haliaeetus leucocephalus) in the Aleutian Islands, Alaska, USA. We studied the diets, productivity, and density of breeding Bald Eagles on four islands during 1993–1994 and 2000–2002, when sea otters were abundant and scarce, respectively. Bald Eagles depend on nearshore marine communities for most of their prey in this ecosystem, so we predicted that the recent decline in otter populations would have an indirect negative effect on diets and demography of Bald Eagles. Contrary to our predictions, we found no effects on density of breeding pairs on four islands from 1993–1994 to 2000–2002. In contrast, diets and diet diversity of Bald Eagles changed considerably between the two time periods, likely reflecting a change in prey availability resulting from the increase and subsequent decline in sea otter populations. The frequency of sea otter pups, rock greenling (Hexagammus lagocephalus), and smooth lumpsuckers (Aptocyclus ventricosus) in the eagle's diet declined with corresponding increases in Rock Ptarmigan (Lagopus mutus), Glaucous-winged Gulls (Larus glaucescens), Atka mackerel (Pleurogrammus monopterygius), and various species of seabirds during the period of the recent otter population decline. Breeding success and productivity of Bald Eagles also increased during this time period, which may be due to the higher nutritional quality of avian prey consumed in later years. Our results provide further evidence of the wide-ranging indirect effects of sea otter predation on nearshore marine communities and another apex predator, the Bald Eagle. Although the indirect effects of sea otters are widely known, this example is unique because the food-web pathway transcended five species and several trophic levels in linking one apex
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NASA Astrophysics Data System (ADS)
Wallace, L. M.; Hreinsdottir, S.; Hamling, I. J.; D'Anastasio, E.; Bartlow, N. M.
2017-12-01
Just after midnight on 14 Nov 2016 (NZ Local time), the M7.8 Kaikoura earthquake ruptured a complex sequence of strike-slip and reverse faults over an approximately 150 km length in the northeastern South Island of New Zealand (Hamling et al., 2017, Science). In the months following the earthquake, time-dependent inversions of InSAR observations and continuous and semi-continuous GPS measurements reveal up to 0.5 m of afterslip on the subduction interface beneath the northern South Island underlying the region of large coseismic slip on crustal faults in the M7.8 earthquake. The geodetic data also require significant afterslip on a subset of the crustal faults that ruptured in the earthquake, including the Needles, Jordan Thrust, and Kekerengu faults. Our best-fitting models also suggest significant afterslip on an offshore reverse fault, in a similar position to one inferred by Clark et al. (2017, EPSL) from coseismic coastal uplift data. The M7.8 earthquake also triggered widespread slow slip occurring over much of the Hikurangi subduction zone beneath the North Island. Immediately following the earthquake, continuous GPS sites operated by GeoNet (www.geonet.org.nz) along the North Island's east coast (above the Hikurangi subduction zone) detected several to 30 mm of eastward motion over the two-week period immediately following the M7.8 event. These sites are located 350-650 km from the M7.8 earthquake. Such large eastward motion along the North Island's east coast following the earthquake is consistent with the initiation of a large slow slip event along the shallow, offshore portion of the Hikurangi subduction zone. In addition to shallow slow slip (<15 km depth) triggered offshore the east coast, we also observe deeper slow slip (>30 km depth) triggered in the Kapiti region at the southern Hikurangi margin. The Kapiti SSE was still ongoing as of August 2017, although we expect it to finish before the end of 2017. Given the large distance of the shallow east
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Earthquakes of Loihi submarine volcano and the Hawaiian hot spot.
Klein, F.W.
1982-01-01
Loihi is an active submarine volcano located 35km S of the island of Hawaii and may eventually grow to be the next and S most island in the Hawaiian chain. The Hawaiian Volcano Observatory recorded two major earthquake swarms located there in 1971-1972 and 1975 which were probably associated with submarine eruptions or intrusions. The swarms were located very close to Loihi's bathymetric summit, except for earthquakes during the second stage of the 1971-1972 swarm, which occurred well onto Loihi's SW flank. The flank earthquakes appear to have been triggered by the preceding activity and possible rifting along Loihi's long axis, similar to the rift-flank relationship at Kilauea volcano. Other changes accompanied the shift in locations from Loihi's summit to its flank, including a shift from burst to continuous seismicity, a rise in maximum magnitude, a change from small earthquake clusters to a larger elongated zone, a drop in b value, and a presumed shift from concentrated volcanic stresses to a more diffuse tectonic stress on Loihi's flank. - Author
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NASA Astrophysics Data System (ADS)
Obana, Koichiro; Takahashi, Tsutomu; No, Tetsuo; Kaiho, Yuka; Kodaira, Shuichi; Yamashita, Mikiya; Sato, Takeshi; Nakamura, Takeshi
2014-04-01
describe the aftershocks of a Mw 7.4 intraplate normal-faulting earthquake that occurred 150 km east Ogasawara (Bonin) Islands, Japan, on 21 December 2010. It occurred beneath the outer trench slope of the Izu-Ogasawara trench, where the Pacific plate subducts beneath the Philippine Sea plate. Aftershock observations using ocean bottom seismographs (OBSs) began soon after the earthquake and multichannel seismic reflection surveys were conducted across the aftershock area. Aftershocks were distributed in a NW-SE belt 140 km long, oblique to the N-S trench axis. They formed three subparallel lineations along a fracture zone in the Pacific plate. The OBS observations combined with data from stations on Chichi-jima and Haha-jima Islands revealed a migration of the aftershock activity. The first hour, which likely outlines the main shock rupture, was limited to an 80 km long area in the central part of the subsequent aftershock area. The first hour activity occurred mainly around, and appears to have been influenced by, nearby large seamounts and oceanic plateau, such as the Ogasawara Plateau and the Uyeda Ridge. Over the following days, the aftershocks expanded beyond or into these seamounts and plateau. The aftershock distribution and migration suggest that crustal heterogeneities related to a fracture zone and large seamounts and oceanic plateau in the incoming Pacific plate affected the rupture of the main shock. Such preexisting structures may influence intraplate normal-faulting earthquakes in other regions of plate flexure prior to subduction.
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L'aléa tsunami en Polynésie française : synthèse des observations et des mesures
NASA Astrophysics Data System (ADS)
Schindelé, François; Hébert, Hélène; Reymond, Dominique; Sladen, Anthony
2006-12-01
Since 1837, 15 tsunamis in French Polynesia have been reported, 11 generated damage. The two last major Pacific-wide tsunamis, 1946 Aleutian and 1960 Chilean, generated damage in most of the archipelagos. Only one in 1999 was generated by a local source, a coastal cliff failure on Fatu-Hiva Island. Since 1965, no earthquake magnitude was greater than 8.4 and, consequently, no ocean-wide tsunami of large amplitude has crossed the Pacific Ocean. Nevertheless, the four tide gauge installed in French Polynesia recorded 33 distinct tsunamis of amplitude from several centimetres to 1.6 m, generated by earthquakes of magnitude between 7.3 and 8.4, two of them damageable in Marquesas bays. To cite this article: F. Schindelé et al., C. R. Geoscience 338 (2006).
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2011-11-21
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2010-09-14
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2013-08-23
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NASA Astrophysics Data System (ADS)
Lynch, L.
2015-12-01
The economies of most of the Anglo-phone Eastern Caribbean islands have tripled to quadrupled in size since independence from England. There has also been commensurate growth in human and physical development as indicated by macro-economic indices such as Human Development Index and Fixed Capital Formation. A significant proportion of the accumulated wealth is invested in buildings and infrastructure which are highly susceptible to strong ground motion since the region is located along an active plate boundary. In the case of Trinidad and Tobago, Fixed Capital Formation accumulation since 1980 is almost US200 billion dollars. Recent studies have indicated that this twin island state is at significant risk from several seismic sources, both on land and offshore. To effectively mitigate the risk it is necessary to prescribe long-term measures such as the development and implementation of building code and standards, structural retrofitting, land use planning, preparedness planning and risk transfer mechanisms. The record has shown that Trinidad and Tobago has been been slow in the prescribing such measures which has consequently compounded it vulnerability to large earthquakes. This assessment reveals that the losses from a large (magnitude 7+) on land or an extreme (magnitude 8+) event could result in losses of up to US28B and that current risk transfer measures will only cater for less than ten percent of such losses.
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A comparison study of 2006 Java earthquake and other Tsunami earthquakes
NASA Astrophysics Data System (ADS)
Ji, C.; Shao, G.
2006-12-01
We revise the slip processes of July 17 2006 Java earthquakes by combined inverting teleseismic body wave, long period surface waves, as well as the broadband records at Christmas island (XMIS), which is 220 km away from the hypocenter and so far the closest observation for a Tsunami earthquake. Comparing with the previous studies, our approach considers the amplitude variations of surface waves with source depths as well as the contribution of ScS phase, which usually has amplitudes compatible with that of direct S phase for such low angle thrust earthquakes. The fault dip angles are also refined using the Love waves observed along fault strike direction. Our results indicate that the 2006 event initiated at a depth around 12 km and unilaterally rupture southeast for 150 sec with a speed of 1.0 km/sec. The revised fault dip is only about 6 degrees, smaller than the Harvard CMT (10.5 degrees) but consistent with that of 1994 Java earthquake. The smaller fault dip results in a larger moment magnitude (Mw=7.9) for a PREM earth, though it is dependent on the velocity structure used. After verified with 3D SEM forward simulation, we compare the inverted result with the revised slip models of 1994 Java and 1992 Nicaragua earthquakes derived using the same wavelet based finite fault inversion methodology.
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NASA Astrophysics Data System (ADS)
Worthington, Lindsay L.; Gulick, Sean P. S.; Pavlis, Terry L.
Within the northern Gulf of Alaska, the Yakutat (YAK) microplate obliquely collides with and subducts beneath the North American (NA) continent at near-Pacific plate velocities. We investigate the extent that thin-skinned deformation on offshore structures located within the western portion of the unsubducted YAK block accommodates YAK-NA convergence. We compare faulting and folding observed on high-resolution and basin-scale multichannel seismic (MCS) reflection data with earthquake locations and surface ruptures observed on high-resolution bathymetric data. Holocene sediments overlying the Kayak Island fault zone (KIZ), previously interpreted as a region of active contraction, are relatively flat-lying, suggesting that active convergence within the KIZ is waning. Seismic reflection profiles east of KIZ show up to ˜200 m of undisturbed sediments overlying older folds in the Bering Trough, indicating that this area has been tectonically inactive since at least the last ˜1.3 Ma. Farther east, MCS profiles image active deformation in surface sediments along the eastern edge of the Pamplona zone (PZ) fold-and-thrust belt, that are collocated with a concentration of earthquake events that continues southwest to Khitrov Ridge and onshore through Icy Bay. These observations suggest that during the late Quaternary offshore shallow deformation style changed from distributed across the western Yakutat block to localized at the eastern edge of the PZ with extrusion of sediments southwest through the Khitrov Ridge area to the Aleutian Trench. This shallow deformation is interpreted as deformation of an accretionary complex above a shallow decollement.
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NASA Technical Reports Server (NTRS)
Shin-Chan, Han; Sauber, Jeanne; Pollitz, Fred
2016-01-01
Large earthquakes often trigger viscoelastic adjustment for years to decades depending on the rheological properties and the nature and spatial extent of coseismic stress. The 2006 Mw8.3 thrust and 2007 Mw8.1 normal fault earthquakes of the central Kuril Islands resulted in significant postseismic gravity change in GRACE but without a discernible coseismic gravity change. The gravity increase of approximately 4 micro-Gal, observed consistently from various GRACE solutions around the epicentral area during 2007-2015, is interpreted as resulting from gradual seafloor uplift by (is) approximately 6 cm produced by postseismic relaxation. The GRACE data are best fit with a model of 25-35 km for the elastic thickness and approximately 10(exp 18) Pa s for the Maxwell viscosity of the asthenosphere. The large measurable postseismic gravity change (greater than coseismic change) emphasizes the importance of viscoelastic relaxation in understanding tectonic deformation and fault-locking scenarios in the Kuril subduction zone.
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Han, Shin-Chan; Sauber, Jeanne; Pollitz, Fred
2016-04-16
Large earthquakes often trigger viscoelastic adjustment for years to decades depending on the rheological properties and the nature and spatial extent of coseismic stress. The 2006 M w 8.3 thrust and 2007 M w 8.1 normal fault earthquakes of the central Kuril Islands resulted in significant postseismic gravity change in GRACE but without a discernible coseismic gravity change. The gravity increase of ~4 µGal, observed consistently from various GRACE solutions around the epicentral area during 2007-2015, is interpreted as resulting from gradual seafloor uplift by ~6 cm produced by postseismic relaxation. The GRACE data are best fit with a model of 25-35 km for the elastic thickness and ~10 18 Pa s for the Maxwell viscosity of the asthenosphere. The large measurable postseismic gravity change (greater than coseismic change) emphasizes the importance of viscoelastic relaxation in understanding tectonic deformation and fault-locking scenarios in the Kuril subduction zone.
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NASA Astrophysics Data System (ADS)
Taymaz, Tuncay; Yolsal-Çevikbilen, Seda; Ulutaş, Ergin
2016-04-01
The finite-fault source rupture models and numerical simulations of tsunami waves generated by 28 October 2012 Queen Charlotte Islands (Mw: 7.8), and 16 September 2015 Illapel-Chile (Mw: 8.3) earthquakes are presented. These subduction zone earthquakes have reverse faulting mechanisms with small amount of strike-slip components which clearly reflect the characteristics of convergence zones. The finite-fault slip models of the 2012 Queen Charlotte and 2015 Chile earthquakes are estimated from a back-projection method that uses teleseismic P- waveforms to integrate the direct P-phase with reflected phases from structural discontinuities near the source. Non-uniform rupture models of the fault plane, which are obtained from the finite fault modeling, are used in order to describe the vertical displacement on seabed. In general, the vertical displacement of water surface was considered to be the same as ocean bottom displacement, and it is assumed to be responsible for the initial water surface deformation gives rise to occurrence of tsunami waves. In this study, it was calculated by using the elastic dislocation algorithm. The results of numerical tsunami simulations are compared with tide gauges and Deep-ocean Assessment and Reporting of Tsunami (DART) buoy records. De-tiding, de-trending, low-pass and high-pass filters were applied to detect tsunami waves in deep ocean sensors and tide gauge records. As an example, the observed records and results of simulations showed that the 2012 Queen Charlotte Islands earthquake generated about 1 meter tsunami-waves in Maui and Hilo (Hawaii), 5 hours and 30 minutes after the earthquake. Furthermore, the calculated amplitudes and time series of the tsunami waves of the recent 2015 Illapel (Chile) earthquake are exhibiting good agreement with the records of tide and DART gauges except at stations Valparaiso and Pichidangui (Chile). This project is supported by The Scientific and Technological Research Council of Turkey (TUBITAK
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NASA Astrophysics Data System (ADS)
Fukao, Y.; Sugioka, H.; Ito, A.; Shiobara, H.; Sandanbata, O.; Watada, S.; Satake, K.
2016-12-01
An array of ocean bottom pressure gauges was deployed off east of Aogashima island of the Izu-Bonin arc from May 2014 to May 2015. The array consists of 10 ocean bottom pressure gauges using ParoScientific quartz resonators which can measure absolute water pressure at 7000m depth with nano-resolution. The array configures equilateral triangles with minimum and maximum lengths of 10 and 30km. This array recorded seismic and tsunami waves from the CLVD-type earthquake (M5.7) of May 02, 2015, that occurred near Torishima Island 100 km distant from the array. Comparison with records of ordinary thrust earthquakes with similar magnitudes at similar distances indicates that this event generated anomalously large tsunamis relative to seismic waves. We made an array analysis for the phase speed, propagating azimuth and travel time of tsunami wave in a frequency range 1-10 mHz, where the dispersion effect is significant. The results show excellent agreements with the frequency-dependent ray-tracing calculations. The tsunami trace apparently starts with positive onset (pressure increase) and reaches a maximum amplitude of about 200Pa (≈2cm in tsunami height). A closer inspection, however, shows a preceding negative small pulse (Fig. 1), suggesting that the seafloor deformation at the tsunami source consists of a central large uplift and a peripheral small depression. This mode of deformation is qualitatively consistent with a finite CLVD source uniformly shortened laterally and uniformly stretched vertically without volume change. The detection of weak initial motions is indebted to the array deployment of sensitive pressure gauges far away from coastal regions. The bandpass-filtered waveform is drastically different between the lower and higher frequency ranges. The waveform is single-peaked in the lower frequency range (<5 mHz) but is ringing in the higher frequency range (>5 mHz), corresponding to the tsunami spectrum that consists of the broad primary peak around 3.5 m
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2011-04-20
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2011-04-14
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2011-11-15
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2013-12-17
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2010-12-13
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2011-12-09
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2010-11-12
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2013-04-25
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2013-02-08
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2012-10-09
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2011-03-07
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2013-01-03
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2011-11-29
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NASA Astrophysics Data System (ADS)
Tsuboi, S.; Nakamura, T.; Miyoshi, T.
2015-12-01
May 30, 2015 Bonin Islands, Japan earthquake (Mw 7.8, depth 679.9km GCMT) was one of the deepest earthquakes ever recorded. We apply the waveform inversion technique (Kikuchi & Kanamori, 1991) to obtain slip distribution in the source fault of this earthquake in the same manner as our previous work (Nakamura et al., 2010). We use 60 broadband seismograms of IRIS GSN seismic stations with epicentral distance between 30 and 90 degrees. The broadband original data are integrated into ground displacement and band-pass filtered in the frequency band 0.002-1 Hz. We use the velocity structure model IASP91 to calculate the wavefield near source and stations. We assume that the fault is squared with the length 50 km. We obtain source rupture model for both nodal planes with high dip angle (74 degree) and low dip angle (26 degree) and compare the synthetic seismograms with the observations to determine which source rupture model would explain the observations better. We calculate broadband synthetic seismograms with these source propagation models using the spectral-element method (Komatitsch & Tromp, 2001). We use new Earth Simulator system in JAMSTEC to compute synthetic seismograms using the spectral-element method. The simulations are performed on 7,776 processors, which require 1,944 nodes of the Earth Simulator. On this number of nodes, a simulation of 50 minutes of wave propagation accurate at periods of 3.8 seconds and longer requires about 5 hours of CPU time. Comparisons of the synthetic waveforms with the observation at teleseismic stations show that the arrival time of pP wave calculated for depth 679km matches well with the observation, which demonstrates that the earthquake really happened below the 660 km discontinuity. In our present forward simulations, the source rupture model with the low-angle fault dipping is likely to better explain the observations.
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2012-03-05
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2013-12-05
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2012-10-31
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NASA Astrophysics Data System (ADS)
Lee, Shiann-Jong; Liu, Qinya; Tromp, Jeroen; Komatitsch, Dimitri; Liang, Wen-Tzong; Huang, Bor-Shouh
2014-06-01
We developed a Real-time Online earthquake Simulation system (ROS) to simulate regional earthquakes in Taiwan. The ROS uses a centroid moment tensor solution of seismic events from a Real-time Moment Tensor monitoring system (RMT), which provides all the point source parameters including the event origin time, hypocentral location, moment magnitude and focal mechanism within 2 min after the occurrence of an earthquake. Then, all of the source parameters are automatically forwarded to the ROS to perform an earthquake simulation, which is based on a spectral-element method (SEM). A new island-wide, high resolution SEM mesh model is developed for the whole Taiwan in this study. We have improved SEM mesh quality by introducing a thin high-resolution mesh layer near the surface to accommodate steep and rapidly varying topography. The mesh for the shallow sedimentary basin is adjusted to reflect its complex geometry and sharp lateral velocity contrasts. The grid resolution at the surface is about 545 m, which is sufficient to resolve topography and tomography data for simulations accurate up to 1.0 Hz. The ROS is also an infrastructural service, making online earthquake simulation feasible. Users can conduct their own earthquake simulation by providing a set of source parameters through the ROS webpage. For visualization, a ShakeMovie and ShakeMap are produced during the simulation. The time needed for one event is roughly 3 min for a 70 s ground motion simulation. The ROS is operated online at the Institute of Earth Sciences, Academia Sinica (http://ros.earth.sinica.edu.tw/). Our long-term goal for the ROS system is to contribute to public earth science outreach and to realize seismic ground motion prediction in real-time.
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Arc segmentation and seismicity in the Solomon Islands arc, SW Pacific
NASA Astrophysics Data System (ADS)
Chen, Ming-Chu; Frohlich, Cliff; Taylor, Frederick W.; Burr, George; van Ufford, Andrew Quarles
2011-07-01
This paper evaluates neotectonic segmentation in the Solomon Islands forearc, and considers how it relates to regional tectonic evolution and the extent of ruptures of large megathrust earthquakes. We first consider regional geomorphology and Quaternary vertical displacements, especially uplifted coral reef terraces. Then we consider geographic seismicity patterns, aftershock areas and vertical displacements for large earthquakes, focal mechanisms, and along-arc variations in seismic moment release to evaluate the relationship between neotectonically defined segments and seismicity. Notably, one major limitation of using seismicity to evaluate arc segmentation is the matter of accurately defining earthquake rupture zones. For example, shoreline uplifts associated with the 1 April 2007 M w 8.1 Western Solomons earthquake indicate that the along-arc extent of rupture was about 50 km smaller than the aftershock area. Thus if we had relied on aftershocks alone to identify the 2007 rupture zone, as we do for most historical earthquakes, we would have missed the rupture's relationship to a major morphologic feature. In many cases, the imprecision of defining rupture zones without surface deformation data may be largely responsible for the poor mismatches to neotectonic boundaries. However, when a precise paleoseismic vertical deformation history is absent, aftershocks are often the best available tool for inferring rupture geometries. Altogether we identify 16 segments in the Solomon Islands. These comprise three major tectonic regimes or supersegments that correspond respectively to the forearc areas of Guadalcanal-Makira, the New Georgia island group, and Bougainville Islands. Subduction of the young and relatively shallow and buoyant Woodlark Basin and spreading system distinguishes the central New Georgia supersegment from the two neighboring supersegments. The physiographic expression of the San Cristobal trench is largely absent, but bathymetric mapping of the
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Stevenson, A.J.; Scholl, D.W.; Vallier, T.L.
1990-05-01
The central segment of the Aleutian Trench (162{degree}W to 175{degree}E) is an intraoceanic subduction zone that contains an anomalously thick sedimentary fill (4 km maximum). The fill is an arcward-thickening and slightly tilted wedge of sediment characterized acoustically by laterally continuous, closely spaced, parallel reflectors. These relations are indicative of turbidite deposition. The trench floor and reflection horizons are planar, showing no evidence of an axial channel or any transverse fan bodies. Cores of surface sediment recover turbidite layers, implying that sediment transport and deposition occur via diffuse, sheetlike, fine-grained turbidite flows that occupy the full width of the trench.more » The mineralogy of Holocene trench sediments document a mixture of island-arc (dominant) and continental source terranes. GLORIA side-scan sonar images reveal a westward-flowing axial trench channel that conducts sediment to the eastern margin of the central segment, where channelized flow cases. Much of the sediment transported in this channel is derived from glaciated drainages surrounding the Gulf of Alaska which empty into the eastern trench segment via deep-sea channel systems (Surveyor and others) and submarine canyons (Hinchinbrook and others). Insular sediment transport is more difficult to define. GLORIA images show the efficiency with which the actively growing accretionary wedge impounds sediment that manages to cross a broad fore-arc terrace. It is likely that island-arc sediment reaches the trench either directly via air fall, via recycling of the accretionary prism, or via overtopping of the accretionary ridges by the upper parts of thick turbidite flows.« less
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NASA Astrophysics Data System (ADS)
Vanacore, E.; Niu, F.
2007-12-01
This study analyzes SKS and SKKS waveforms recorded on the BOLIVAR array in Venezuela and the BANJO array in South America from earthquake sources located in Tonga and Alaska regions to characterize the lower mantle beneath the Galapagos Islands. The data analysis applies two independent methods, residual differential SKKS-SKS travel times and anisotropy measurements, to examine the historically unsampled region. The residual differential travel time observations were performed using 21 earthquakes from the Tonga trench with magnitudes greater than 5.5 Mw that were recorded on the Bolivar array. Only data that was deemed to have a high SNR for both the SKS and SKKS phases were retained for analysis. Significant positive values of differential travel time that indicate low velocity along the SKKS raypaths are detected east of ~\\m270° longitude. The anisotropy data set consists of 31 intermediate and deep focus earthquakes from the Tonga and Aleutian trenches recorded on the BOLIVAR and BANJO arrays respectively. The anisotropy fast axis angle and time lag of the two phases are calculated using the 1-layer cross-convolution method of Menke and Levin (2003) with a maximum time lag window of 3 seconds. We retain results with an amplitude normalized squared L2 norm value of 0.6 or less for analysis. Because the raypaths of the SKS and SKKS phases are similar in the upper mantle and sample different regions of the lower mantle, we attribute inconsistencies between the two anisotropy to difference of the mantle structure near the CMB. We define significant difference in the azimuth of the fast axis as any difference between the SKSac and SKKSac measurements greater than 15 degrees. The dataset is dominated by inconsistent fast axis azimuth measurements between the SKSac and SKKSac phases, but does not isolate a single geographic region. Comparison of the splitting time measurements yields that inconsistency between the two phases is more significant, greater than 0.5 s
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NASA Astrophysics Data System (ADS)
Major, J. R.; Liu, Z.; Harris, R. A.; Fisher, T. L.
2011-12-01
Using Dutch records of geophysical events in Indonesia over the past 400 years, and tsunami modeling, we identify tsunami sources that have caused severe devastation in the past and are likely to reoccur in the near future. The earthquake history of Western Indonesia has received much attention since the 2004 Sumatra earthquakes and subsequent events. However, strain rates along a variety of plate boundary segments are just as high in eastern Indonesia where the earthquake history has not been investigated. Due to the rapid population growth in this region it is essential and urgent to evaluate its earthquake and tsunami hazards. Arthur Wichmann's 'Earthquakes of the Indian Archipelago' shows that there were 30 significant earthquakes and 29 tsunami between 1629 to 1877. One of the largest and best documented is the great earthquake and tsunami effecting the Banda islands on 1 August, 1629. It caused severe damage from a 15 m tsunami that arrived at the Banda Islands about a half hour after the earthquake. The earthquake was also recorded 230 km away in Ambon, but no tsunami is mentioned. This event was followed by at least 9 years of aftershocks. The combination of these observations indicates that the earthquake was most likely a mega-thrust event. We use a numerical simulation of the tsunami to locate the potential sources of the 1629 mega-thrust event and evaluate the tsunami hazard in Eastern Indonesia. The numerical simulation was tested to establish the tsunami run-up amplification factor for this region by tsunami simulations of the 1992 Flores Island (Hidayat et al., 1995) and 2006 Java (Katoet al., 2007) earthquake events. The results yield a tsunami run-up amplification factor of 1.5 and 3, respectively. However, the Java earthquake is a unique case of slow rupture that was hardly felt. The fault parameters of recent earthquakes in the Banda region are used for the models. The modeling narrows the possibilities of mega-thrust events the size of the one
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2011-03-30
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2010-04-01
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2011-04-05
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2010-03-16
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2012-04-18
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2012-10-31
... Bering Sea and Aleutian Islands Management Area, the Fishery Management Plan for Groundfish of the Gulf... D. The U.S. groundfish fisheries of the Gulf of Alaska (GOA) and the Bering Sea and Aleutian Islands... groundfish species under the FMP for Groundfish of the Gulf of Alaska. The fixed-gear sablefish fishery is...
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Han, Shin-Chan; Sauber, Jeanne; Pollitz, Fred
2016-01-01
Large earthquakes often trigger viscoelastic adjustment for years to decades depending on the rheological properties and the nature and spatial extent of coseismic stress. The 2006 Mw8.3 thrust and 2007 Mw8.1 normal fault earthquakes of the central Kuril Islands resulted in significant postseismic gravity change in GRACE but without a discernible coseismic gravity change. The gravity increase of ~4 µGal, observed consistently from various GRACE solutions around the epicentral area during 2007–2015, is interpreted as resulting from gradual seafloor uplift by ~6 cm produced by postseismic relaxation. The GRACE data are best fit with a model of 25–35 km for the elastic thickness and ~1018 Pa s for the Maxwell viscosity of the asthenosphere. The large measurable postseismic gravity change (greater than coseismic change) emphasizes the importance of viscoelastic relaxation in understanding tectonic deformation and fault-locking scenarios in the Kuril subduction zone. PMID:27642200
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Han, Shin-Chan; Sauber, Jeanne; Pollitz, Fred
2016-01-01
Large earthquakes often trigger viscoelastic adjustment for years to decades depending on the rheological properties and the nature and spatial extent of coseismic stress. The 2006 Mw8.3 thrust and 2007 Mw8.1 normal fault earthquakes of the central Kuril Islands resulted in significant postseismic gravity change in Gravity Recovery and Climate Experiment (GRACE) but without a discernible coseismic gravity change. The gravity increase of ~4 μGal, observed consistently from various GRACE solutions around the epicentral area during 2007–2015, is interpreted as resulting from gradual seafloor uplift by ~6 cm produced by postseismic relaxation. The GRACE data are best fit with a model of 25–35 km for the elastic thickness and ~1018 Pa s for the Maxwell viscosity of the asthenosphere. The large measurable postseismic gravity change (greater than coseismic change) emphasizes the importance of viscoelastic relaxation in understanding tectonic deformation and fault-locking scenarios in the Kuril subduction zone.
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NASA Astrophysics Data System (ADS)
Akhter, S. H.; Seeber, L.; Steckler, M. S.
2015-12-01
Bangladesh is one of the most densely populated countries in the world. It occupies a major part of the Bengal Basin, which contains the Ganges-Brahmaputra Delta (GBD), the largest and one of the most active of world deltas, and is located along the Alpine-Himalayan seismic belt. As such it is vulnerable to many natural hazards, especially earthquakes. The country sits at the junction of three tectonic plates - Indian, Eurasian, and the Burma 'sliver' of the Sunda plate. These form two boundaries where plates converge- the India-Eurasia plate boundary to the north forming the Himalaya Arc and the India-Burma plate boundary to the east forming the Indo-Burma Arc. The India-Burma plate boundary is exceptionally wide because collision with the GBD feeds an exception amount of sediment into the subduction zone. Thus the Himalayan continent collision orogeny along with its syntaxes to the N and NE of Bangladesh and the Burma Arc subduction boundary surround Bangladesh on two sides with active faults of regional scale, raising the potential for high-magnitude earthquakes. In recent years Bangladesh has experienced minor to moderate earthquakes. Historical records show that major and great earthquakes have ravaged the country and the neighboring region several times over the last 450 years. Field observations of Tertiary structures along the Chittagong-Teknaf coast reveal that the rupture of 1762 Arakan megathrust earthquake extended as far north as the Sitakund anticline to the north of the city of Chittagong. This earthquake brought changes to the landscape, uplifting the Teknaf peninsula and St. Martin's Island by about 2-2.5 m, and activated two mud volcanos along the axis of the Sitakund anticline, where large tabular blocks of exotic crystalline limestone, were tectonically transported from a deep-seated formation along with the eruptive mud. Vast area of the coast including inland areas east of the lower Meghna River were inundated. More than 500 peoples died near
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NASA Astrophysics Data System (ADS)
Tanigawa, K.; Sawai, Y.; Bobrowsky, P. T.; Huntley, D.; Goff, J. R.; Shinozaki, T.
2017-12-01
We examined tsunami deposits within salt marshes at Tofino, Ucluelet and Port Alberni along the west coast of Vancouver Island aligned with the Cascadia Subduction Zone. Previous studies in 1990s reported tsunami deposits associated with the 1964 Alaska, the 1700 Cascadia and older earthquakes from these sites (Clague and Bobrowsky, 1994a; b). However, the ages of older tsunami deposits were not well constrained. We excavated pits and collected salt marsh sediments in 2015 and 2016. Sand layers interbedded within peat and mud deposits occur at widely separated sites on Vancouver Island. Two visible sand layers were observed in Tofino, four in Ucluelet and three in Port Alberni; which is consistent with previous studies. We used a combination of 210Pb, 137Cs and 14C dating to constrain the depositional ages of sand layers. Plant microfossils and insects obtained directly above and below each sand layer were used for radiocarbon dating. Radiocarbon ages indicate that the sand layer prior to the 1700 tsunami sediments was deposited between 550-300 calendar years before present. This depositional age is correlative to the T2 event of the Cascadia Subduction Zone turbidite history (Goldfinger et al., 2012). References: Clague and Bobrowsky (1994a) Quaternary Research, 41, 176-184. Clague and Bobrowsky (1994b) GSA Bulletin 106, 1293-1303. Goldfinger et al. (2012) USGS Professional Paper 1661-F, 170 p.
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Field survey of the March 28, 2005 Nias-Simeulue earthquake and Tsunami
Borrero, J.C.; McAdoo, B.; Jaffe, B.; Dengler, L.; Gelfenbaum, G.; Higman, B.; Hidayat, R.; Moore, A.; Kongko, W.; ,; Peters, R.; Prasetya, G.; Titov, V.; Yulianto, E.
2011-01-01
On the evening of March 28, 2005 at 11:09 p.m. local time (16:09 UTC), a large earthquake occurred offshore of West Sumatra, Indonesia. With a moment magnitude (Mw) of 8.6, the event caused substantial shaking damage and land level changes between Simeulue Island in the north and the Batu Islands in the south. The earthquake also generated a tsunami, which was observed throughout the source region as well as on distant tide gauges. While the tsunami was not as extreme as the tsunami of December 26th, 2004, it did cause significant flooding and damage at some locations. The spatial and temporal proximity of the two events led to a unique set of observational data from the earthquake and tsunami as well as insights relevant to tsunami hazard planning and education efforts. ?? 2010 Springer Basel AG.
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-02-19
.... 0810141351-9087-02] RIN 0648-XU36 Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod by Catcher/Processors Using Hook-and-Line Gear in the Bering Sea and Aleutian Islands Management Area AGENCY: National... using hook-and-line gear in the Bering Sea and Aleutian Islands management area (BSAI). This action is...
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Moles, A; Heintz, R A
2007-07-01
Fish serve as intermediate hosts for a number of larval parasites that have the potential of maturing in marine mammals such as Steller sea lions (Eumetopias jubatus). We examined the prevalence of parasites from 229 fish collected between March and July 2002 near two islands used by Steller sea lions in Southeast Alaska and island habitats in the Aleutian Islands. Sea lion populations have remained steady in Southeast Alaska but have been declining over the last 30 yr in the Aleutian Islands. Even though the fish samples near the Southeast Alaska haul-outs were composed of numerous small species of fish and the Aleutian Islands catch was dominated by juveniles of commercially harvested species, the parasite fauna was similar at all locations. Eleven of the 20 parasite taxa identified were in their larval stage in the fish hosts, several of which have been described from mammalian final hosts. Four species of parasite were more prevalent in Southeast Alaska fish samples, and seven parasite species, including several larval forms capable of infecting marine mammals, were more prevalent in fish from the Aleutian Islands. Nevertheless, parasites available to Steller sea lions from common fish prey are not likely to be a major factor in the decline of this marine mammal species.
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Evidence of the 1762 Arakan and Prior Earthquakes in the Northern Sunda Subduction
NASA Astrophysics Data System (ADS)
Mondal, Dhiman Ranjan
The objective of this dissertation is to understand the seismic hazard associated with Arakan segment of the northern Sunda subduction along SE Bangladesh. In order to do that, it is necessary to document geologic evidence for the 1762 Arakan earthquake and prior events, to help estimate the recurrence interval (repeat time) for that earthquake. Historical records described that the 1762 earthquake caused extensive damage along the Arakan segment of the Sunda subduction system. But the geologic evidence for the earthquake farther north is necessary to better understand its associated seismic hazard to the densely populated nation of Bangladesh. This dissertation presents the results obtained from U/Th dating of the dead and live coral microatolls including their elevations measured by high precision GPS from the Saint Martin's Island, DEM analysis and elevation of terraces from Teknaf coast and fault dislocation modeling based on the data obtained from the Saint Martin's Island and Teknaf. Coral microatolls from Saint Martin's island documents the evidence of the 1762 and prior earthquakes. The U/Th ages documents strong evidence of microatoll die offs related to the 1762 earthquake. The > 2 m elevation difference between the dead microatolls and present-day living corals suggest that the microatolls died due to the coseismic uplift of 1762 Arakan earthquake. This dissertation also provides evidence for two additional earthquakes taking place in 700 and 1140 C.E. which suggests an earthquake recurrence interval of 500 years. Geomorphic studies documented three terraces along the coast of Teknaf. Several marine terraces have been previously documented along the west coast of Myanmar. The youngest of these terraces has been correlated to the coseismic uplift of 1762 Arakan along the Myanmar coast. The terraces along the coast of Teknaf are characterized by flat to semi-flat surfaces followed by sharp topographic rises. DEM (Digital Elevation System) analysis and GPS
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Literature and information related to the natural resources of the North Aleutian Basin of Alaska.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Stull, E.A.; Hlohowskyj, I.; LaGory, K. E.
The North Aleutian Basin Planning Area of the Minerals Management Service (MMS) is a large geographic area with significant natural resources. The Basin includes most of the southeastern part of the Bering Sea Outer Continental Shelf, including all of Bristol Bay. The area supports important habitat for a wide variety of species and globally significant habitat for birds and marine mammals, including several federally listed species. Villages and communities of the Alaska Peninsula and other areas bordering or near the Basin rely on its natural resources (especially commercial and subsistence fishing) for much of their sustenance and livelihood. The offshoremore » area of the North Aleutian Basin is considered to have important hydrocarbon reserves, especially natural gas. In 2006, the MMS released a draft proposed program, 'Outer Continental Shelf Oil and Gas Leasing Program, 2007-2012' and an accompanying draft programmatic environmental impact statement (EIS). The draft proposed program identified two lease sales proposed in the North Aleutian Basin in 2010 and 2012, subject to restrictions. The area proposed for leasing in the Basin was restricted to the Sale 92 Area in the southwestern portion. Additional EISs will be needed to evaluate the potential effects of specific lease actions, exploration activities, and development and production plans in the Basin. A full range of updated multidisciplinary scientific information will be needed to address oceanography, fate and effects of oil spills, marine ecosystems, fish, fisheries, birds, marine mammals, socioeconomics, and subsistence in the Basin. Scientific staff at Argonne National Laboratory were contracted to assist MMS with identifying and prioritizing information needs related to potential future oil and gas leasing and development activities in the North Aleutian Basin. Argonne focused on three related tasks: (1) identify and gather relevant literature published since 1996, (2) synthesize and summarize
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Spatial and temporal seismic velocity changes on Kyushu Island during the 2016 Kumamoto earthquake
Nimiya, Hiro; Ikeda, Tatsunori; Tsuji, Takeshi
2017-01-01
Monitoring of earthquake faults and volcanoes contributes to our understanding of their dynamic mechanisms and to our ability to predict future earthquakes and volcanic activity. We report here on spatial and temporal variations of seismic velocity around the seismogenic fault of the 2016 Kumamoto earthquake [moment magnitude (Mw) 7.0] based on ambient seismic noise. Seismic velocity near the rupture faults and Aso volcano decreased during the earthquake. The velocity reduction near the faults may have been due to formation damage, a change in stress state, and an increase in pore pressure. Further, we mapped the post-earthquake fault-healing process. The largest seismic velocity reduction observed at Aso volcano during the earthquake was likely caused by pressurized volcanic fluids, and the large increase in seismic velocity at the volcano’s magma body observed ~3 months after the earthquake may have been a response to depressurization caused by the eruption. This study demonstrates the usefulness of continuous monitoring of faults and volcanoes. PMID:29202026
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Interim report on the St. Elias, Alaska earthquake of 28 February 1979
Lahr, John C.; Plafker, George; Stephens, C.D.; Foglean, K.A.; Blackford, M.E.
1979-01-01
On 28 February 1979 an earthquake with surface wave magnitude (Ms) of 7.7 (W. Person, personal communication, 1979) occurred beneath the Chugach and St. Elias mountains of southern Alaska (fig. 1). This is a region of complex tectonics resulting from northwestward convergence between the Pacific and North American plates. To the east, the northwest-trending Fairweather fault accommodates the movement with dextral slip of about 5.5 cm/yr (Plafker, Hudson, and others, 1978); to the west, the Pacific plate underthrusts Alaska at the Aleutian trench, which trends southwestward (Plafker 1969). The USGS has operated a telemetered seismic network in southern Alaska since 1971 and it was greatly expanded along the eastern Gulf of Alaska in September 1974. The current configuration of stations is shown in Figure 9. Technical details of the network are available in published earthquake catalogs (Lahr, Page, and others, 1974; Fogleman, Stephens, and others, 1978). Preliminary analysis of the data from this network covering the time period September 1, 1978 through March 10, 1979, as well as worldwide data for the main shock will be discussed in this paper.
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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.
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Trusdell, Frank A.; Moore, Richard B.; Sako, Maurice K.
2006-01-01
Pagan Island is the subaerial portion of two adjoining Quaternary stratovolcanoes near the middle of the active Mariana Arc, [FAT1]north of Saipan. Pagan and the other volcanic islands that constitute part of the Arc form the northern half of the East Mariana Ridge[FAT2], which extends about 2-4 km above the ocean floor. The > 6-km-deep Mariana Trench adjoins the East Mariana Ridge on the east, and the Mariana Trough, partly filled with young lava flows and volcaniclastic sediment, lies on the west of the Northern Mariana Islands (East Mariana Ridge. The submarine West Mariana Ridge, Tertiary in age, bounds the western side of the Mariana Trough. The Mariana Trench and Northern Mariana Islands (East Mariana Ridge) overlie an active subduction zone where the Pacific Plate, moving northwest at about 10.3 cm/year, is passing beneath the Philippine Plate, moving west-northwest at 6.8 cm/year. Beneath the Northern Mariana Islands, earthquake hypocenters at depths of 50-250 km identify the location of the west-dipping subduction zone, which farther west becomes nearly vertical and extends to 700 km depth. During the past century, more than 40 earthquakes of magnitude 6.5-8.1 have shaken the Mariana Trench. The Mariana Islands form two sub-parallel, concentric, concave-west arcs. The southern islands comprise the outer arc and extend north from Guam to Farallon de Medinilla. They consist of Eocene to Miocene volcanic rocks and uplifted Tertiary and Quaternary limestone. The nine northern islands extend from Anatahan to Farallon de Pajaros and form part of the inner arc. The active inner arc extends south from Anatahan, where volcanoes, some of which are active, form seamounts west of the older outer arc. Other volcanic seamounts of the active arc surmount the East Mariana Ridge in the vicinity of Anatahan and Sarigan and north and south of Farallon de Pajaros. Six volcanoes (Farallon de Pajaros, Asuncion, Agrigan, Mount Pagan, Guguan, and Anatahan) in the northern islands
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NASA Astrophysics Data System (ADS)
Almendros, J.; Carmona, E.; Jiménez, V.; Díaz-Moreno, A.; Lorenzo, F.
2018-05-01
In September 2014 there was a sharp increase in the seismic activity of the Bransfield Strait, Antarctica. More than 9,000 earthquakes with magnitudes up to 4.6 located SE of Livingston Island were detected over a period of 8 months. A few months after the series onset, local seismicity at the nearby (˜35 km) Deception Island volcano increased, displaying enhanced long-period seismicity and several outbursts of volcano-tectonic (VT) earthquakes. Before February 2015, VT earthquakes occurred mainly at 5-20 km SW of Deception Island. In mid-February the numbers and sizes of VT earthquakes escalated, and their locations encompassed the whole volcanic edifice, suggesting a situation of generalized unrest. The activity continued in anomalously high levels at least until May 2015. Given the spatial and temporal coincidence, it is unlikely that the Livingston series and the Deception VT swarm were unrelated. We propose that the Livingston series may have produced a triggering effect on Deception Island volcano. Dynamic stresses associated to the seismic swarm may have induced overpressure in the unstable volcanic system, leading to a magmatic intrusion that may in turn have triggered the VT swarm. Alternatively, both the Livingston earthquakes and the VT swarm could be consequences of a magmatic intrusion at Deception Island. The Livingston series would be an example of precursory distal VT swarm, which seems to be a common feature preceding volcanic eruptions and magma intrusions in long-dormant volcanoes.
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NASA Astrophysics Data System (ADS)
Lange, Dietrich; Ruiz, Javier; Carrasco, Sebastián; Manríquez, Paula
2018-04-01
On 2016 December 25, an Mw 7.6 earthquake broke a portion of the Southern Chilean subduction zone south of Chiloé Island, located in the central part of the Mw 9.5 1960 Valdivia earthquake. This region is characterized by repeated earthquakes in 1960 and historical times with very sparse interseismic activity due to the subduction of a young (˜15 Ma), and therefore hot, oceanic plate. We estimate the coseismic slip distribution based on a kinematic finite-fault source model, and through joint inversion of teleseismic body waves and strong motion data. The coseismic slip model yields a total seismic moment of 3.94 × 1020 N.m that occurred over ˜30 s, with the rupture propagating mainly downdip, reaching a peak slip of ˜4.2 m. Regional moment tensor inversion of stronger aftershocks reveals thrust type faulting at depths of the plate interface. The fore- and aftershock seismicity is mostly related to the subduction interface with sparse seismicity in the overriding crust. The 2016 Chiloé event broke a region with increased locking and most likely broke an asperity of the 1960 earthquake. The updip limit of the main event, aftershocks, foreshocks and interseismic activity are spatially similar, located ˜15 km offshore and parallel to Chiloé Islands west coast. The coseismic slip model of the 2016 Chiloé earthquake suggests a peak slip of 4.2 m that locally exceeds the 3.38 m slip deficit that has accumulated since 1960. Therefore, the 2016 Chiloé earthquake possibly released strain that has built up prior to the 1960 Valdivia earthquake.
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Neal, Christina A.; Herrick, Julie; Girina, O.A.; Chibisova, Marina; Rybin, Alexander; McGimsey, Robert G.; Dixon, Jim
2014-01-01
The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest or suspected unrest at 12 volcanic centers in Alaska during 2010. The most notable volcanic activity consisted of intermittent ash emissions from long-active Cleveland volcano in the Aleutian Islands. AVO staff also participated in hazard communication regarding eruptions or unrest at seven volcanoes in Russia as part of an ongoing collaborative role in the Kamchatka and Sakhalin Volcanic Eruption Response Teams.
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Aleutian tholeiitic and calc-alkaline magma series I: The mafic phenocrysts
NASA Astrophysics Data System (ADS)
Kay, S. Mahlburg; Kay, Robert W.
1985-07-01
Diagnostic mafic silicate assemblages in a continuous spectrum of Aleutian volcanic rocks provide evidence for contrasts in magmatic processes in the Aleutian arc crust. Tectonic segmentation of the arc exerts a primary control on the variable mixing, fractional crystallization and possible assimilation undergone by the magmas. End members of the continuum are termed calc-alkaline (CA) and tholeiitic (TH). CA volcanic rocks (e.g., Buldir and Moffett volcanoes) have low FeO/MgO ratios and contain compositionally diverse phenocryst populations, indicating magma mixing. Their Ni and Cr-rich magnesian olivine and clinopyroxene come from mantle-derived mafic olivine basalts that have mixed with more fractionated magmas at mid-to lower-crustal levels immediately preceding eruption. High-Al amphibole is associated with the mafic end member. In contrast, TH lavas (e.g., Okmok and Westdahl volcanoes) have high FeO/MgO ratios and contain little evidence for mixing. Evolved lavas represent advanced stages of low pressure crystallization from a basaltic magma. These lavas contain groundmass olivine (FO 40 50) and lack Ca-poor pyroxene. Aleutian volcanic rocks with intermediate FeO/MgO ratios are termed transitional tholeiitic (TTH) and calc-alkaline (TCA). TCA magmas are common (e.g., Moffett, Adagdak, Great Sitkin, and Kasatochi volcanoes) and have resulted from mixing of high-Al basalt with more evolved magmas. They contain amphibole (high and low-Al) or orthopyroxene or both and are similar to the Japanese hypersthene-series. TTH magmas (e.g., Okmok and Westdahl) contain orthopyroxene or pigeonite or both, and show some indication of upper crustal mixing. They are mineralogically similar to the Japanese pigeonite-series. High-Al basalt lacks Mg-rich mafic phases and is a derivative magma produced by high pressure fractionation of an olivine tholeiite. The low pressure mineral assemblage of high-Al basalt results from crystallization at higher crustal levels.
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New seafloor map of the Puerto Rico trench helps assess earthquake and tsunami hazards
NASA Astrophysics Data System (ADS)
Brink, Uri ten; Danforth, William; Polloni, Christopher; Andrews, Brian; Llanes, Pilar; Smith, Shepard; Parker, Eugene; Uozumi, Toshihiko
2004-09-01
The Puerto Rico Trench, the deepest part of the Atlantic Ocean, is located where the North American (NOAM) plate is subducting under the Caribbean plate (Figure l). The trench region may pose significant seismic and tsunami hazards to Puerto Rico and the U.S.Virgin Islands, where 4 million U.S. citizens reside. Widespread damage in Puerto Rico and Hispaniola from an earthquake in 1787 was estimated to be the result of a magnitude 8 earthquake north of the islands [McCann et al., 2004]. A tsunami killed 40 people in NW Puerto Rico following a magnitude 7.3 earthquake in 1918 [Mercado and McCann, 1998]. Large landslide escarpments have been mapped on the seafloor north of Puerto Rico [Mercado et al., 2002; Schwab et al., 1991],although their ages are unknown.
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New seafloor map of the Puerto Rico Trench helps assess earthquake and tsunami hazards
ten Brink, Uri S.; Danforth, William; Polloni, Christopher; Andrews, Brian D.; Llanes Estrada, Pilar; Smith, Shepard; Parker, Eugene; Uozumi, Toshihiko
2004-01-01
The Puerto Rico Trench, the deepest part of the Atlantic Ocean, is located where the North American (NOAM) plate is subducting under the Caribbean plate (Figure l). The trench region may pose significant seismic and tsunami hazards to Puerto Rico and the U.S.Virgin Islands, where 4 million U.S. citizens reside. Widespread damage in Puerto Rico and Hispaniola from an earthquake in 1787 was estimated to be the result of a magnitude 8 earthquake north of the islands [McCann et al., 2004]. A tsunami killed 40 people in NW Puerto Rico following a magnitude 7.3 earthquake in 1918 [Mercado and McCann, 1998]. Large landslide escarpments have been mapped on the seafloor north of Puerto Rico [Mercado et al., 2002; Schwab et al., 1991],although their ages are unknown.
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Tsunami Numerical Simulation for Hypothetical Giant or Great Earthquakes along the Izu-Bonin Trench
NASA Astrophysics Data System (ADS)
Harada, T.; Ishibashi, K.; Satake, K.
2013-12-01
We performed tsunami numerical simulations from various giant/great fault models along the Izu-Bonin trench in order to see the behavior of tsunamis originated in this region and to examine the recurrence pattern of great interplate earthquakes along the Nankai trough off southwest Japan. As a result, large tsunami heights are expected in the Ryukyu Islands and on the Pacific coasts of Kyushu, Shikoku and western Honshu. The computed large tsunami heights support the hypothesis that the 1605 Keicho Nankai earthquake was not a tsunami earthquake along the Nankai trough but a giant or great earthquake along the Izu-Bonin trench (Ishibashi and Harada, 2013, SSJ Fall Meeting abstract). The Izu-Bonin subduction zone has been regarded as so-called 'Mariana-type subduction zone' where M>7 interplate earthquakes do not occur inherently. However, since several M>7 outer-rise earthquakes have occurred in this region and the largest slip of the 2011 Tohoku earthquake (M9.0) took place on the shallow plate interface where the strain accumulation had considered to be a little, a possibility of M>8.5 earthquakes in this region may not be negligible. The latest M 7.4 outer-rise earthquake off the Bonin Islands on Dec. 22, 2010 produced small tsunamis on the Pacific coast of Japan except for the Tohoku and Hokkaido districts and a zone of abnormal seismic intensity in the Kanto and Tohoku districts. Ishibashi and Harada (2013) proposed a working hypothesis that the 1605 Keicho earthquake which is considered a great tsunami earthquake along the Nankai trough was a giant/great earthquake along the Izu-Bonin trench based on the similarity of the distributions of ground shaking and tsunami of this event and the 2010 Bonin earthquake. In this study, in order to examine the behavior of tsunamis from giant/great earthquakes along the Izu-Bonin trench and check the Ishibashi and Harada's hypothesis, we performed tsunami numerical simulations from fault models along the Izu-Bonin trench
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Near-Field Postseismic Deformation Measurements from the Andaman and Nicobar Islands
NASA Astrophysics Data System (ADS)
Freymueller, J. T.; Rajendran, C.; Rajendran, K.; Rajamani, A.
2006-12-01
Since the December 26, 2004 Sumatra-Andaman Islands earthquake, we have carried out campaign GPS measurements at several sites in the Andaman and Nicobar Islands (India) and installed three continuous GPS sites in the region. Most of these sites had pre-earthquake measurements, which showed slow westward motion relative to the Indian plate. Postseismic measurements, on the other hand, show average westward velocities of several cm/yr to a few decimeters per year relative to the Indian plate. The motion of all sites is strongly non-linear in time, and is not uniform in space. We use a combination of continuous site time series and nearby campaign site time series to construct the most complete possible postseismic displacement records. Postseismic deformation from large earthquakes is likely to be dominated by a combination of afterslip on the deeper subduction interface, and viscoelastic relaxation of the mantle. Afterslip following the (similar magnitude) 1964 Alaska earthquake amounted to 20-50% of the magnitude of the coseismic slip, and smaller subduction zone earthquakes have exhibited the same or even larger proportion of afterslip to coseismic slip. We compare the time decay and spatial pattern of the observed postseismic displacement to postseismic deformation models and to observations from the Alaska earthquake.
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The Aleutian Low and Winter Climatic Conditions in the Bering Sea. Part I: Classification
NASA Astrophysics Data System (ADS)
Rodionov, S. N.; Overland, J. E.; Bond, N. A.
2005-01-01
The Aleutian low is examined as a primary determinant of surface air temperature (SAT) variability in the Bering Sea during the winter (December-January-February-March (DJFM)) months. The Classification and Regression Tree (CART) method is used to classify five types of atmospheric circulation for anomalously warm months (W1-W5) and cold months (C1-C5). For the Bering Sea, changes in the position of the Aleutian low are shown to be more important than changes in its central pressure. The first two types, W1 and C1, account for 51% of the "warm" and 37% of the "cold" months. The W1-type pattern is characterized by the anomalously deep Aleutian low shifted west and north of its mean position. In this situation, an increased cyclonic activity occurs in the western Bering Sea. The C1-type pattern represents a split Aleutian low with one center in the northwestern Pacific and the other in the Gulf of Alaska. The relative frequency of the W1 to C1 types of atmospheric circulation varies on decadal time scales, which helps to explain the predominance of fluctuations on these time scales in the weather of the Bering Sea. Previous work has noted the prominence of multidecadal variability in the North Pacific. The present study finds multidecadal variations in frequencies of the W3 and C3 patterns, both of which are characterized by increased cyclonic activity south of 51°N. In general, the CART method is found to be a suitable means for characterizing the wintertime atmospheric circulation of the North Pacific in terms of its impact on the Bering Sea. The results show that similar pressure anomaly patterns for the North Pacific as a whole can actually result in different conditions for the Bering Sea, and that similar weather conditions in the Bering Sea can arise from decidedly different large-scale pressure patterns.
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The Relationships Between Earthquakes, Faults, and Recent Glacial Fluctuations in Southern Alaska
NASA Astrophysics Data System (ADS)
Wiest, K. R.; Sauber, J. M.; Doser, D. I.; Hurtado, J. M.; Velasco, A. A.
2004-12-01
In southern Alaska, northwestward-directed subduction of the Pacific plate is accompanied by accretion of the Yakutat terrane to continental Alaska. In the tectonically complex region between the transcurrent Fairweather fault and the Alaska-Aleutian subduction zone, active crustal shortening and strike-slip faulting occurs. Since a series of large earthquakes in 1899 (Mw = 8.1, Yakataga; Mw=8.1 Yakutat), there has been only one large event (1979 St. Elias Mw = 7.4) in the Yakutat region between the aftershock zones of the 1964 Prince William Sound (Mw = 9.2) and 1958 Fairweather (Mw = 8.2) earthquakes. In this region, the glaciers are extensive and many of them have undergone significant retreat in the last 100 years. This study investigates the relationships between small to moderate magnitude events, ongoing crustal deformation, active geological structures in the region, and recent glacial fluctuations. To map earthquake locations with respect to current glacier positions, we will incorporate Ice Cloud and land Elevation Satellite (ICESat) data into an updated Digital Elevation Model (DEM) of key glaciated regions that has been created using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images in conjunction with Shuttle Radar Topography Mission (SRTM) data. For the seismological investigation, we focused on relocating events that have occurred since the last large earthquake at St. Elias in 1979 using data obtained from the Alaska Earthquake Information Center (AEIC). P-wave polarity first motion focal mechanisms were generated for the relocated events and evaluated. Our preliminary relocations suggest a dipping slab in cross-section and also show a number of shallow event clusters around local glaciers. The focal mechanisms are quite variable but, in general, indicate strike-slip and oblique-slip focal mechanisms. Some of our highest quality focal mechanisms show dip-slip faulting and are from shallow events located near glacial
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Complex multifault rupture during the 2016 Mw 7.8 Kaikōura earthquake, New Zealand.
Hamling, Ian J; Hreinsdóttir, Sigrún; Clark, Kate; Elliott, John; Liang, Cunren; Fielding, Eric; Litchfield, Nicola; Villamor, Pilar; Wallace, Laura; Wright, Tim J; D'Anastasio, Elisabetta; Bannister, Stephen; Burbidge, David; Denys, Paul; Gentle, Paula; Howarth, Jamie; Mueller, Christof; Palmer, Neville; Pearson, Chris; Power, William; Barnes, Philip; Barrell, David J A; Van Dissen, Russ; Langridge, Robert; Little, Tim; Nicol, Andrew; Pettinga, Jarg; Rowland, Julie; Stirling, Mark
2017-04-14
On 14 November 2016, northeastern South Island of New Zealand was struck by a major moment magnitude ( M w ) 7.8 earthquake. Field observations, in conjunction with interferometric synthetic aperture radar, Global Positioning System, and seismology data, reveal this to be one of the most complex earthquakes ever recorded. The rupture propagated northward for more than 170 kilometers along both mapped and unmapped faults before continuing offshore at the island's northeastern extent. Geodetic and field observations reveal surface ruptures along at least 12 major faults, including possible slip along the southern Hikurangi subduction interface; extensive uplift along much of the coastline; and widespread anelastic deformation, including the ~8-meter uplift of a fault-bounded block. This complex earthquake defies many conventional assumptions about the degree to which earthquake ruptures are controlled by fault segmentation and should motivate reevaluation of these issues in seismic hazard models. Copyright © 2017, American Association for the Advancement of Science.
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Distinctly different parental magmas for plutons and lavas in the central Aleutian arc
NASA Astrophysics Data System (ADS)
Cai, Y.; Rioux, M. E.; Kelemen, P. B.; Goldstein, S. L.; Bolge, L.; Kylander-Clark, A. R.
2014-12-01
While it is generally agreed that continental crust is generated by arc magmatism, average arc lavas are basaltic while the bulk continental crust is andesitic, and this has led to many models for secondary reprocessing of the arc crust in order to form continental crust. We report new data on calc-alkaline plutons in the central Aleutians showing that they have distinctly different sources compared to Holocene tholeiitic lavas. Therefore the lavas are not representative of the net magmatic transfer from the mantle into the arc crust. Eocene to Miocene (9-39 Ma) intermediate to felsic plutonic rocks from the central Aleutian arc show higher SiO2 at a given Mg#, higher ɛNd- and ɛHf-values, and lower Pb isotope ratios than Holocene volcanic rocks from the same region. Instead, the plutonic rocks resemble volcanics from the western Aleutians isotopically, and have chemical compositions similar to bulk continental crust. These data could reflect temporal variation of Aleutian magma source compositions, from Eocene-Miocene "isotopically depleted" and predominantly calc-alkaline to Holocene "isotopically enriched" and predominantly tholeiitic. Alternatively, they may reflect different transport and emplacement processes for the magmas that form plutons and lavas: calc-alkaline magmas with higher Si content and high viscosity may preferentially form plutons, perhaps after extensive mid-crustal degassing of initially high water contents. The latter case implies that the upper and middle arc crust is more like the calc-alkaline bulk composition of the continental crust than the lavas alone. Crustal reprocessing mechanisms that preserve upper and middle arc crust, while removing lower arc crust, can account for the genesis and evolution of continental crust. Since gabbroic lower arc crust extends from ca 20-40 km depth, and is density stable over most of this depth range, "delamination" of dense lithologies [1] may not be sufficient to accomplish this. Alternatively
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Identifying Intraplate Mechanism by B-Value Calculations in the South of Java Island
NASA Astrophysics Data System (ADS)
Bagus Suananda Y., Ida; Aufa, Irfan; Harlianti, Ulvienin
2018-03-01
Java is the most populous island in Indonesia with 50 million people live there. This island geologically formed at the Eurasia plate margin by the subduction of the Australian oceanic crust. At the south part of Java, beside the occurrence of 2-plate convergence earthquake (interplate), there are also the activities of the intraplate earthquake. Research for distinguish this 2 different earthquake type is necessary for estimating the behavior of the earthquake that may occur. The aim of this research is to map the b-value in the south of Java using earthquake data from 1963 until 2008. The research area are divided into clusters based on the epicenter mapping results with magnitude more than 4 and three different depth (0-30 km, 30-60 km, 60-100 km). This location clustering indicate group of earthquakes occurred by the same structure or mechanism. On some cluster in the south of Java, b-value obtained are between 0.8 and 1.25. This range of b-value indicates the region was intraplate earthquake zone, with 0.72-1.2 b-value range is the indication of intraplate earthquake zone. The final validation is to determine the mechanism of a segment done by correlating the epicenter and b-value plot with the available structural geology data. Based on this research, we discover that the earthquakes occur in Java not only the interplate earthquake, the intraplate earthquake also occurred here. By identifying the mechanism of a segment in the south of Java, earthquake characterization that may occur can be done for developing the accurate earthquake disaster mitigation system.
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Aftereffects of Subduction-Zone Earthquakes: Potential Tsunami Hazards along the Japan Sea Coast.
Minoura, Koji; Sugawara, Daisuke; Yamanoi, Tohru; Yamada, Tsutomu
2015-10-01
The 2011 Tohoku-Oki Earthquake is a typical subduction-zone earthquake and is the 4th largest earthquake after the beginning of instrumental observation of earthquakes in the 19th century. In fact, the 2011 Tohoku-Oki Earthquake displaced the northeast Japan island arc horizontally and vertically. The displacement largely changed the tectonic situation of the arc from compressive to tensile. The 9th century in Japan was a period of natural hazards caused by frequent large-scale earthquakes. The aseismic tsunamis that inflicted damage on the Japan Sea coast in the 11th century were related to the occurrence of massive earthquakes that represented the final stage of a period of high seismic activity. Anti-compressive tectonics triggered by the subduction-zone earthquakes induced gravitational instability, which resulted in the generation of tsunamis caused by slope failing at the arc-back-arc boundary. The crustal displacement after the 2011 earthquake infers an increased risk of unexpected local tsunami flooding in the Japan Sea coastal areas.
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Nelson, A.R.; Johnson, S.Y.; Kelsey, H.M.; Wells, R.E.; Sherrod, B.L.; Pezzopane, S.K.; Bradley, L.A.; Koehler, R. D.; Bucknam, R.C.
2003-01-01
Five trenches across a Holocene fault scarp yield the first radiocarbon-measured earthquake recurrence intervals for a crustal fault in western Washington. The scarp, the first to be revealed by laser imagery, marks the Toe Jam Hill fault, a north-dipping backthrust to the Seattle fault. Folded and faulted strata, liquefaction features, and forest soil A horizons buried by hanging-wall-collapse colluvium record three, or possibly four, earthquakes between 2500 and 1000 yr ago. The most recent earthquake is probably the 1050-1020 cal. (calibrated) yr B.P. (A.D. 900-930) earthquake that raised marine terraces and triggered a tsunami in Puget Sound. Vertical deformation estimated from stratigraphic and surface offsets at trench sites suggests late Holocene earthquake magnitudes near M7, corresponding to surface ruptures >36 km long. Deformation features recording poorly understood latest Pleistocene earthquakes suggest that they were smaller than late Holocene earthquakes. Postglacial earthquake recurrence intervals based on 97 radiocarbon ages, most on detrital charcoal, range from ???12,000 yr to as little as a century or less; corresponding fault-slip rates are 0.2 mm/yr for the past 16,000 yr and 2 mm/yr for the past 2500 yr. Because the Toe Jam Hill fault is a backthrust to the Seattle fault, it may not have ruptured during every earthquake on the Seattle fault. But the earthquake history of the Toe Jam Hill fault is at least a partial proxy for the history of the rest of the Seattle fault zone.
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NASA Astrophysics Data System (ADS)
Koulali, A.; McClusky, S.; Wallace, L.; Allgeyer, S.; Tregoning, P.; D'Anastasio, E.; Benavente, R.
2017-08-01
Following a sequence of three Slow Slip Events (SSEs) on the northern Hikurangi Margin, between June 2015 and August 2016, a Mw 7.1 earthquake struck 30 km offshore of the East Cape region in the North Island of New Zealand on the 2 September 2016 (NZ local time). The earthquake was also followed by a transient deformation event (SSE or afterslip) northeast of the North Island, closer to the earthquake source area. We use data from New Zealand's continuous Global Positioning System networks to invert for the SSE slip distribution and evolution on the Hikurangi subduction interface. Our slip inversion results show an increasing amplitude of the slow slip toward the Te Araroa earthquake foreshock and main shock area, suggesting a possible triggering of the Mw 7.1 earthquake by the later stage of the slow slip sequence. We also show that the transient deformation following the Te Araroa earthquake ruptured a portion of the Hikurangi Trench northeast of the North Island, farther north than any previously observed Hikurangi margin SSEs. Our slip inversion and the coulomb stress calculation suggest that this transient may have been induced as a response to the increase in the static coulomb stress change downdip of the rupture plane on the megathrust. These observations show the importance of considering the interaction between slow slip events, seismic, and aseismic events, not only on the same megathrust interface but also on faults within the surrounding crust.
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Wells, R.E.; Blakely, R.J.; Sugiyama, Y.; Scholl, D. W.; Dinterman, P.A.
2003-01-01
Published areas of high coseismic slip, or asperities, for 29 of the largest Circum-Pacific megathrust earthquakes are compared to forearc structure revealed by satellite free-air gravity, bathymetry, and seismic profiling. On average, 71% of an earthquake's seismic moment and 79% of its asperity area occur beneath the prominent gravity low outlining the deep-sea terrace; 57% of an earthquake's asperity area, on average, occurs beneath the forearc basins that lie within the deep-sea terrace. In SW Japan, slip in the 1923, 1944, 1946, and 1968 earthquakes was largely centered beneath five forearc basins whose landward edge overlies the 350??C isotherm on the plate boundary, the inferred downdip limit of the locked zone. Basin-centered coseismic slip also occurred along the Aleutian, Mexico, Peru, and Chile subduction zones but was ambiguous for the great 1964 Alaska earthquake. Beneath intrabasin structural highs, seismic slip tends to be lower, possibly due to higher temperatures and fluid pressures. Kilometers of late Cenozoic subsidence and crustal thinning above some of the source zones are indicated by seismic profiling and drilling and are thought to be caused by basal subduction erosion. The deep-sea terraces and basins may evolve not just by growth of the outer arc high but also by interseismic subsidence not recovered during earthquakes. Basin-centered asperities could indicate a link between subsidence, subduction erosion, and seismogenesis. Whatever the cause, forearc basins may be useful indicators of long-term seismic moment release. The source zone for Cascadia's 1700 A.D. earthquake contains five large, basin-centered gravity lows that may indicate potential asperities at depth. The gravity gradient marking the inferred downdip limit to large coseismic slip lies offshore, except in northwestern Washington, where the low extends landward beneath the coast. Transverse gravity highs between the basins suggest that the margin is seismically segmented and
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-08-06
...NMFS apportions amounts of the non-specified reserve to the initial total allowable catch (ITAC) of ``other flatfish'' in the Bering Sea and Aleutian Islands management area (BSAI) and Greenland turbot in the Aleutian Island subarea of the BSAI. This action is necessary to allow the fisheries to continue operating. It is intended to promote the goals and objectives of the fishery management plan for the BSAI.
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Regional Variations in Aleutian Magma Composition
NASA Astrophysics Data System (ADS)
Nye, C. J.
2008-12-01
This study is based on sample data spanning 20 years from USGS, UAF, and DGGS geologists too numerous to list here. The 2900-km long Aleutian arc contains more than 50 active and over 90 Holocene volcanoes. The arc is built on oceanic Bering-sea floor west of 166W and quasi-continental crust east of 166W. Over the past twenty years the Alaska Volcano Observatory has conducted baseline geologic mapping (or remapping) and volcanic-hazards studies of selected volcanoes - generally those targeted for geophysical monitoring. This marks the largest sustained effort to study Aleutian volcanoes in half a century; AVO scientists have logged as many as 700 person-days per field season. Geologic studies have resulted in comprehensive suites of stratigraphically constrained samples and more than 3500 new whole-rock analyses by XRF and ICP/MS from more than 30 centers, more than doubling the number of previously published analyses. Examination of the data for regional and inter-volcano variations yields a number of first-order observations. (1) The arc can be broadly divided into an eastern segment (east of 158W) of calcalkaline andesite stratocones; a central segment dominated by large, mafic, tholeiitic shield volcanoes and stratocones; and a western segment (west of 175W) of smaller volcanoes with variable morphologies and generally more andesitic compositions. (2) There are NO significant first-order compositional signals that coincide with the transition from oceanic to continental basement. (3) Individual volcanoes are often subtly distinct from neighbors, and those distinctions persist for the lifetime of the centers. (4) All centers, notably including the large basaltic centers of the central arc, are strongly affected by open-system processes significantly more complicated than mixing among sibling-fractionates of parental mafic magmas. (5) Petrogenetic pathways are long-lived; individual batches of magma are (generally) not. (6) Calcalkaline andesites have
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Field survey of the 1994 Mindoro Island, Philippines tsunami
NASA Astrophysics Data System (ADS)
Imamura, Fumihiko; Synolakis, Costas E.; Gica, Edison; Titov, Vasily; Listanco, Eddie; Lee, Ho Jun
1995-09-01
This is a report of the field survey of the November 15, 1994 Mindoro Island, Philippines, tsunami generated by an earthquake ( M=7.0) with a strike-slip motion. We will report runup heights from 54 locations on Luzon, Mindoro and other smaller islands in the Cape Verde passage between Mindoro and Luzon. Most of the damage was concentrated along the northern coast of Mindoro. Runup height distribution ranged 3 4 m at the most severely damaged areas and 2 4 in neighboring areas. The tsunami-affected area was limited to within 10 km of the epicenter. The largest recorded runup value of 7.3 m was measured on the southwestern coast of Baco Island while a runup of 6.1 m was detected on its northern coastline. The earthquake and tsunami killed 62 people, injured 248 and destroyed 800 houses. As observed in other recent tsunami disasters, most of the casualties were children. Nearly all eyewitnesses interviewed described the first wave as a leading-depression wave. Eyewitnesses reported that the main direction of tsunami propagation was SW in Subaang Bay, SE in Wawa and Calapan, NE on Baco Island and N on Verde Island, suggesting that the tsunami source area was in the southern Pass of Verde Island and that the wave propagated rapidly in all directions. The fault plane extended offshore to the N of Mindoro Island, with its rupture originating S of Verde Island and propagating almost directly south to the inland of Mindoro, thereby accounting for the relatively limited damage area observed on the N of Mindoro.
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Kirkby, M.J.; Kirkby, Anne V.
1969-01-01
During the 1964 Alaska earthquake, tectonic deformation uplifted the southern end of Montague Island as much as 33 feet or more. The uplifted shoreline is rapidly being modified by subaerial and marine processes. The new raised beach is formed in bedrock, sand, gravel, and deltaic bay-head deposits, and the effect of each erosional process was measured in each material. Fieldwork was concentrated in two areas—MacLeod Harbor on the northwest side and Patton Bay on the southeast side of Montague Island. In the unconsolidated deltaic deposits of MacLeod Harbor, 97 percent of the erosion up to June 1965, 15 months after the earthquake, was fluvial, 2.2 percent was by rainwash, and only 0.8 percent was marine; 52 percent of the total available raised beach material had already been removed. The volume removed by stream erosion was proportional to low-flow discharge raised to the power of 0.75 to 0.95, and this volume increased as the bed material became finer. Stream response to the relative fall in base level was very rapid, most of the downcutting in unconsolidated materials occurring within 48 hours of the uplift for streams with low flows greater than 10 cubic feet per second. Since then, erosion by these streams has been predominantly lateral. Streams with lower discharges, in unconsolidated materials, still had knickpoints after 15 months. No response to uplift could be detected in stream courses above the former preearthquake sea level. Where the raised beach is in bedrock, it is being destroyed principally by marine action but at such a low rate that no appreciable erosion of bedrock was found 15 months after the earthquake. A dated rock platform raised earlier has eroded at a mean rate of 0.49 foot per year. In this area the factor limiting the rate of erosion was rock resistance rather than the transporting capacity of the waves. The break in slope between the top of the raised beach and the former seacliff is being obliterated by debris which is
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Prevention of strong earthquakes: Goal or utopia?
NASA Astrophysics Data System (ADS)
Mukhamediev, Sh. A.
2010-11-01
In the present paper, we consider ideas suggesting various kinds of industrial impact on the close-to-failure block of the Earth’s crust in order to break a pending strong earthquake (PSE) into a number of smaller quakes or aseismic slips. Among the published proposals on the prevention of a forthcoming strong earthquake, methods based on water injection and vibro influence merit greater attention as they are based on field observations and the results of laboratory tests. In spite of this, the cited proofs are, for various reasons, insufficient to acknowledge the proposed techniques as highly substantiated; in addition, the physical essence of these methods has still not been fully understood. First, the key concept of the methods, namely, the release of the accumulated stresses (or excessive elastic energy) in the source region of a forthcoming strong earthquake, is open to objection. If we treat an earthquake as a phenomenon of a loss in stability, then, the heterogeneities of the physicomechanical properties and stresses along the existing fault or its future trajectory, rather than the absolute values of stresses, play the most important role. In the present paper, this statement is illustrated by the classical examples of stable and unstable fractures and by the examples of the calculated stress fields, which were realized in the source regions of the tsunamigenic earthquakes of December 26, 2004 near the Sumatra Island and of September 29, 2009 near the Samoa Island. Here, just before the earthquakes, there were no excessive stresses in the source regions. Quite the opposite, the maximum shear stresses τmax were close to their minimum value, compared to τmax in the adjacent territory. In the present paper, we provide quantitative examples that falsify the theory of the prevention of PSE in its current form. It is shown that the measures for the prevention of PSE, even when successful for an already existing fault, can trigger or accelerate a catastrophic
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NASA Astrophysics Data System (ADS)
Dianala, J. D. B.; Aurelio, M.; Rimando, J. M.; Taguibao, K.
2015-12-01
In a region with little understanding in terms of active faults and seismicity, two large-magnitude reverse-fault related earthquakes occurred within 100km of each other in separate islands of the Central Philippines—the Mw=6.7 February 2012 Negros earthquake and the Mw=7.2 October 2013 Bohol earthquake. Based on source faults that were defined using onshore, offshore seismic reflection, and seismicity data, stress transfer models for both earthquakes were calculated using the software Coulomb. Coulomb stress triggering between the two main shocks is unlikely as the stress change caused by Negros earthquake on the Bohol fault was -0.03 bars. Correlating the stress changes on optimally-oriented reverse faults with seismicity rate changes shows that areas that decreased both in static stress and seismicity rate after the first earthquake were then areas with increased static stress and increased seismicity rate caused by the second earthquake. These areas with now increased stress, especially those with seismicity showing reactivity to static stress changes caused by the two earthquakes, indicate the presence of active structures in the island of Cebu. Comparing the history of instrumentally recorded seismicity and the recent large earthquakes of Negros and Bohol, these structures in Cebu have the potential to generate large earthquakes. Given that the Philippines' second largest metropolitan area (Metro Cebu) is in close proximity, detailed analysis of the earthquake potential and seismic hazards in these areas should be undertaken.
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Lu, Z.; Wicks, C.; Kwoun, O.; Power, J.A.; Dzurisin, D.
2005-01-01
In March 1996, an intense earthquake swarm beneath Akutan Island, Alaska, was accompanied by extensive ground cracking but no eruption of Akutan volcano. Radar interferograms produced from L-band JERS-1 and C-band ERS-1/2 images show uplift associated with the swarm by as much as 60 cm on the western part of the island. The JERS-1 interferogram has greater coherence, especially in areas with loose surface material or thick vegetation. It also shows subsidence of similar magnitude on the eastern part of the island and displacements along faults reactivated during the swarm. The axis of uplift and subsidence strikes about N70??W, which is roughly parallel to a zone of fresh cracks on the northwest flank of the volcano, to normal faults that cut the island and to the inferred maximum compressive stress direction. A common feature of models that fit the deformation is the emplacement of a shallow dike along this trend beneath the northwest flank of the volcano. Both before and after the swarm, the northwest flank was uplifted 5-20 mm/year relative to the southwest flank, probably by magma intrusion. The zone of fresh cracks subsided about 20 mm during 1996-1997 and at lesser rates thereafter, possibly because of cooling and degassing of the intrusion. ?? 2005 CASI.
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Biomarker responses of mussels exposed to earthquake disturbances
NASA Astrophysics Data System (ADS)
Chandurvelan, Rathishri; Marsden, Islay D.; Glover, Chris N.; Gaw, Sally
2016-12-01
The green-lipped mussel, Perna canaliculus is recognised as a bioindicator of coastal contamination in New Zealand (NZ). Mussels (shell length 60-80 mm) were collected from three intertidal areas of Canterbury in the South Island of NZ prior to extreme earthquake disturbances on 22nd February 2011, and 9 months later in October 2011. Trace elements, including arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn), were measured in the gills, digestive gland, foot and mantle. Metal levels in tissues were site specific, and mostly unaffected by earthquake disturbances. Physiological biomarkers were negatively affected by earthquake disturbances and mussels from the Port of Lyttelton had higher negative scope for growth post-earthquake. Metallothionein-like protein in the digestive gland correlated with metal content of tissues, as did catalase activity in the gill and lipid peroxidation values for the digestive gland. This research demonstrates that physiological and other biomarkers are effective at detecting the effects of multiple stressors following seismic disturbances.
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Publications - MP 133 v. 2 | Alaska Division of Geological & Geophysical
Tidal Datum Portal Climate and Cryosphere Hazards Coastal Hazards Program Guide to Geologic Hazards in Maps; Alaska, State of; Aleutian Arc; Aleutian Islands; Coastal and River; Coastal and River Hazards
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NASA Astrophysics Data System (ADS)
Biasi, G. P.; Clark, K.; Berryman, K. R.; Cochran, U. A.; Prior, C.
2010-12-01
-correlate sections at the site. Within a series of dates from a section, ordering with intrinsic precision of the dates indicates an uncertainty at event horizons on the order of 50 years, while the transitions from peat to silt indicating an earthquake are separated by several times this amount. The effect is to create a stair-stepping date sequence that often allows us to link sections and improve dating resolution in both sections. The combined section provides clear evidence for at least 18 earthquake-induced cycles. Event recurrence would be about 390 years in a simple average. Internal evidence and close examination of date sequences provide preliminary indications of as many as 22 earthquakes could be represented at Hokuri Creek, and a recurrence interval of ~320 years. Both sequences indicate a middle sequence from 3800 to 1000 BC in which recurrence intervals are resolvably longer than average. Variability in recurrence is relatively small - relatively few intervals are even >1.5x the average. This indicates that large earthquakes on the Alpine Fault of South Island, New Zealand are best fit by a time-predictable model.
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Earthquake Potential in Myanmar
NASA Astrophysics Data System (ADS)
Aung, Hla Hla
Myanmar region is generally believed to be an area of high earthquake potential from the point of view of seismic activity which has been low compared to the surrounding regions like Indonesia, China, and Pakistan. Geoscientists and seismologists predicted earthquakes to occur in the area north of the Sumatra-Andaman Islands, i.e. the southwest and west part of Myanmar. Myanmar tectonic setting relative to East and SE Asia is rather peculiar and unique with different plate tectonic models but similar to the setting of western part of North America. Myanmar crustal blocks are caught within two lithospheric plates of India and Indochina experiencing oblique subduction with major dextral strike-slip faulting of the Sagaing fault. Seismic tomography and thermal structure of India plate along the Sunda subduction zone vary from south to north. Strong partitioning in central Andaman basin where crustal fragmentation and northward dispersion of Burma plate by back-arc spreading mechanism has been operating since Neogene. Northward motion of Burma plate relative to SE Asia would dock against the major continent further north and might have caused the accumulation of strain which in turn will be released as earthquakes in the future.
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Wald, David J.; Hayes, Gavin P.; Benz, Harley M.; Earle, Paul S.; Briggs, Richard W.
2011-01-01
The M 9.0 11 March 2011 Tohoku, Japan, earthquake and associated tsunami near the east coast of the island of Honshu caused tens of thousands of deaths and potentially over one trillion dollars in damage, resulting in one of the worst natural disasters ever recorded. The U.S. Geological Survey National Earthquake Information Center (USGS NEIC), through its responsibility to respond to all significant global earthquakes as part of the National Earthquake Hazards Reduction Program, quickly produced and distributed a suite of earthquake information products to inform emergency responders, the public, the media, and the academic community of the earthquake's potential impact and to provide scientific background for the interpretation of the event's tectonic context and potential for future hazard. Here we present a timeline of the NEIC response to this devastating earthquake in the context of rapidly evolving information emanating from the global earthquake-response community. The timeline includes both internal and publicly distributed products, the relative timing of which highlights the inherent tradeoffs between the requirement to provide timely alerts and the necessity for accurate, authoritative information. The timeline also documents the iterative and evolutionary nature of the standard products produced by the NEIC and includes a behind-the-scenes look at the decisions, data, and analysis tools that drive our rapid product distribution.
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Eyewitness account of the 1931 great earthquake at Hawke’s Bay, New Zealand
Spall, H.
1984-01-01
No part of New Zealand is far from a known earthquake origin. The magnitude 7.9 earthquake of 1931 at Hawke's Bay, North Island, on February 3, 1931, was the most serious event recorded in New Zealand hsitory. It was responsible for 256 deaths. The Modified Mercalli intensity reached XI in Napier, a city of 35,000 people, and hence, caused considerable destruction to property.
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Code of Federal Regulations, 2013 CFR
2013-10-01
...&GRegulations Alaska PeninsulaSouth Peninsula (MS) North Peninsula (MN) King Crab:AK Peninsula/Aleutian Islands Salmon MM M 5 AAC 34.5005 AAC 12.100 (Aleutians) 5 AAC 09.100 (AK Peninsula) Herring M 5 AAC 27.600...
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Code of Federal Regulations, 2014 CFR
2014-10-01
...&GRegulations Alaska PeninsulaSouth Peninsula (MS) North Peninsula (MN) King Crab:AK Peninsula/Aleutian Islands Salmon MM M 5 AAC 34.5005 AAC 12.100 (Aleutians) 5 AAC 09.100 (AK Peninsula) Herring M 5 AAC 27.600...
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Code of Federal Regulations, 2012 CFR
2012-10-01
...&GRegulations Alaska PeninsulaSouth Peninsula (MS) North Peninsula (MN) King Crab:AK Peninsula/Aleutian Islands Salmon MM M 5 AAC 34.5005 AAC 12.100 (Aleutians) 5 AAC 09.100 (AK Peninsula) Herring M 5 AAC 27.600...
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NASA Astrophysics Data System (ADS)
Ghani, Kay Dora Abd.; Tukiar, Mohd Azuan; Hamid, Nor Hayati Abdul
2017-08-01
Malaysia is surrounded by the tectonic feature of the Sumatera area which consists of two seismically active inter-plate boundaries, namely the Indo-Australian and the Eurasian Plates on the west and the Philippine Plates on the east. Hence, Malaysia experiences tremors from far distant earthquake occurring in Banda Aceh, Nias Island, Padang and other parts of Sumatera Indonesia. In order to predict the safety of precast buildings in Malaysia under near field ground motion the response spectrum analysis could be used for dealing with future earthquake whose specific nature is unknown. This paper aimed to develop of capacity demand response spectrum subject to Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE) in order to assess the performance of precast beam column joint. From the capacity-demand response spectrum analysis, it can be concluded that the precast beam-column joints would not survive when subjected to earthquake excitation with surface-wave magnitude, Mw, of more than 5.5 Scale Richter (Type 1 spectra). This means that the beam-column joint which was designed using the current code of practice (BS8110) would be severely damaged when subjected to high earthquake excitation. The capacity-demand response spectrum analysis also shows that the precast beam-column joints in the prototype studied would be severely damaged when subjected to Maximum Considered Earthquake (MCE) with PGA=0.22g having a surface-wave magnitude of more than 5.5 Scale Richter, or Type 1 spectra.
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NASA Astrophysics Data System (ADS)
Putra, Aprizon; Mutmainah, Herdiana
2016-11-01
Mentawai Islands Regency, especially north Pagai island, suffered two earthquakes on April 15 2016. The local government in cooperation with the relevant parties had tried to minimize casualties before the disaster or during the disaster by making an evacuation route to the TES. The purpose of this study was to the mapping of TES and tsunami evacuation route using the approach of Geographic Information Systems (GIS) for disaster mitigation of tsunami-potential earthquake in north Pagai island.The research was conducted at 3 locations in the coast of Sikakap village, 4 locations in the coast of Taikako village, 3 locations in the coast of Silabu village, 7 locations in the coast of Saumanganya village, and 3 locations in the coast of Matobe village. The effort taken was to evacuate people to the TES with an average distance of 372.62 m from the beach. The results showed that the feasibility of TES that could accommodate residents, among others, were in the hills behind Sikakap Port, Taikako Silaoinan hills, the hills near the Mapinang Silabu village chief's office and Mapinang hills, Gulukguluk Saumanganya and Panatarat Matobe hills.
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Localized surface disruptions observed by InSAR during strong earthquakes in Java and Hawai'i
Poland, M.
2010-01-01
Interferometric Synthetic Aperture Radar data spanning strong earthquakes on the islands of Java and Hawai‘i in 2006 reveal patches of subsidence and incoherence indicative of localized ground failure. Interferograms spanning the 26 May 2006 Java earthquake suggest an area of about 7.5 km2 of subsidence (~2 cm) and incoherence south of the city of Yogyakarta that correlates with significant damage to housing, high modeled peak ground accelerations, and poorly consolidated geologic deposits. The subsidence and incoherence is inferred to be a result of intense shaking and/or damage. At least five subsidence patches on the west side of the Island of Hawai‘i, ranging 0.3–2.2 km2 in area and 3–8 cm in magnitude, occurred as a result of a pair of strong earthquakes on 15 October 2006. Although no felt reports or seismic data are available from the areas in Hawai‘i, the Java example suggests that the subsidence patches indicate areas of amplified earthquake shaking. Surprisingly, all subsidence areas in Hawai‘i were limited to recent, and supposedly stable, lava flows and may reflect geological conditions not detectable at the surface. In addition, two ‘a‘ā lava flows in Hawai‘i were partially incoherent in interferograms spanning the earthquakes, indicating surface disruption as a result of the earthquake shaking. Coearthquake incoherence of rubbly deposits, like ‘a‘ā flows, should be explored as a potential indicator of earthquake intensity and past strong seismic activity.
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Seismic hazard in Hawaii: High rate of large earthquakes and probabilistics ground-motion maps
Klein, F.W.; Frankel, A.D.; Mueller, C.S.; Wesson, R.L.; Okubo, P.G.
2001-01-01
The seismic hazard and earthquake occurrence rates in Hawaii are locally as high as that near the most hazardous faults elsewhere in the United States. We have generated maps of peak ground acceleration (PGA) and spectral acceleration (SA) (at 0.2, 0.3 and 1.0 sec, 5% critical damping) at 2% and 10% exceedance probabilities in 50 years. The highest hazard is on the south side of Hawaii Island, as indicated by the MI 7.0, MS 7.2, and MI 7.9 earthquakes, which occurred there since 1868. Probabilistic values of horizontal PGA (2% in 50 years) on Hawaii's south coast exceed 1.75g. Because some large earthquake aftershock zones and the geometry of flank blocks slipping on subhorizontal decollement faults are known, we use a combination of spatially uniform sources in active flank blocks and smoothed seismicity in other areas to model seismicity. Rates of earthquakes are derived from magnitude distributions of the modem (1959-1997) catalog of the Hawaiian Volcano Observatory's seismic network supplemented by the historic (1868-1959) catalog. Modern magnitudes are ML measured on a Wood-Anderson seismograph or MS. Historic magnitudes may add ML measured on a Milne-Shaw or Bosch-Omori seismograph or MI derived from calibrated areas of MM intensities. Active flank areas, which by far account for the highest hazard, are characterized by distributions with b slopes of about 1.0 below M 5.0 and about 0.6 above M 5.0. The kinked distribution means that large earthquake rates would be grossly under-estimated by extrapolating small earthquake rates, and that longer catalogs are essential for estimating or verifying the rates of large earthquakes. Flank earthquakes thus follow a semicharacteristic model, which is a combination of background seismicity and an excess number of large earthquakes. Flank earthquakes are geometrically confined to rupture zones on the volcano flanks by barriers such as rift zones and the seaward edge of the volcano, which may be expressed by a magnitude
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Vorhis, Robert C.; Rexin, Elmer E.; Coble, R.W.
1967-01-01
The Alaska earthquake of March 27, 1964, had widespread hydrologic effects throughout practically all of the United States. More than 1,450 water-level recorders, scattered throughout all the 50 States except Connecticut, Delaware, and Rhode Island, registered the earthquake. Half of the water-level records were obtained from ground-water observation wells and half at surface-water gaging stations. The earthquake is also known to have registered on water-level recorders on wells in Canada, England, Denmark, Belgium, Egypt, Israel, Libya, Philippine Islands, South-West Africa, South Africa, and Northern Territory of Australia. The Alaska earthquake is the first for which widespread surface-water effects are known. The effects were recorded at stations on flowing streams, rivers, reservoirs, lakes, and ponds. The 755 surface-water stations recording effects are spread through 38 States, but are most numerous in the south-central and southeastern States, especially in Florida and Louisiana. Most of the fluctuations recorded can be referred to more precisely as seismic seiches; however, a few stations recorded the quake as a minor change in stage. The largest recorded seiche outside Alaska was 1.83 feet on a reservoir in Michigan. The next largest was 1.45 feet on Lake Ouachita in Arkansas. The largest fluctuation in a well was 23 feet registered by a pressure recorder near Belle Fourche, S. Dak. Fluctuations of more than 10 feet were reported from wells in Alabama, Florida, Georgia, Illinois, Missouri, and Pennsylvania. A 3.40-foot fluctuation was recorded in a well in Puerto Rico. The Alaska earthquake was registered by about seven times as many water-level recorders as recorded the Hebgen Lake, Mont., earthquake of August 19, 1959.
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Introduction to the High-Rate GPS Network of Puerto Rico and the U.S. Virgin Islands
NASA Astrophysics Data System (ADS)
Wang, G.; Hillebrandt, C. V.; Martinez, J. M.; Huerfano, V.; Schellekens, J.
2008-12-01
The Puerto Rico Seismic Network at the University of Puerto Rico at Mayagüez is a regional earthquake and tsunami monitoring institute. One of its primary objective is to provide timely and reliable earthquake and tsunami information and warning to the state (Puerto Rico) and local governments, the US and British Virgin Islands, as well as to the general public. In the past five years, it has been expanding its operations for the establishment of a Caribbean Tsunami Warning Center. With funding of the Puerto Rico government and NOAA, it is operated 24 hours per day and 7 days per week. Broadband seismometers are generally unable to capture the full bandwidth of long period ground motions following very large earthquakes. As a result, it is difficult to rapidly estimate the true magnitudes of large earthquakes using only seismic data. High-rate GPS has been justified as a very useful tool in recording long-period and permanent earthquake ground motions. Estimation of the true magnitude (and therefore tsunami potential) of large earthquakes may be determined more accurately in a timely manner (minutes after the quake) using high rate GPS observations. With the major aim of improving the ability of the PRSN in rapidly and precisely monitoring large earthquakes, NSF funded a Major Research Instrumentation (MRI) project, Acquisition of 9 High-rate GPS Units for Developing a Broadband Earthquake Observation System in Puerto Rico and the U.S. Virgin Islands (EAR-0722540, August 1, 2007-July 31, 2009). The major purpose of this project is to build a high-rate GPS network in Puerto Rico and the U.S. Virgin Islands. The GPS network includes 3 campaign and 6 permanent GPS stations. These campaign stations were designed to use in emergency response after large earthquakes to get co-seismic and post-seismic displacement. These six permanent stations were designed to complement current seismic observation system of Puerto Rico and U.S. Virgin Islands. We have installed three
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NASA Astrophysics Data System (ADS)
Pamungkas, S. S.; Koesuma, S.; Legowo, Budi
2018-03-01
Sumatra Island is an area that has high tectonic activities. This is because the island of Sumatra is located in two major plates of the world, the Indo-Australian plate and the Eurasia plate. The subduction zone causes Sumatra to deform from time to time. The deformation of Sumatra Island can be observed by continuous recording coordinates using the GPS Station. Continous-GPS (C-GPS) in Sumatra Island is named Sumatran GPS Array (SuGAr), one of them named UMLH. The UMLH GPS station used to observe the displacement in the Aceh City of Sumatra Island, is located in Ujung Muloh. The changes of GPS coordinate recording data can represent the deformation pattern that occurred in Sumatra. On April 11, 2012, according to USGS data, there had been an earthquake in the city of Aceh about 8.6 at coordinates of 2.433°N, 93.072°E. The purpose of this research is to analyze the horizontal displacement due to the occurrence of the earthquake. Data processing is carried out using software GAMIT/GLOBK. The magnitude of the displacement of Sumatra Island before the earthquake, during the earthquake, and after the quake on component X were respectively: 0.04 mm/day, 56.63 mm/day, and 8.28 mm/day; while on component Y were respectively: 0.03 mm/day, 23.78 mm/day, and 1.22 mm/day. The direction of displacement was 253.8° towards Southwest with the assumption that 0° was in the North.
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Tsunami damage along the Andaman Islands coasts
NASA Technical Reports Server (NTRS)
2005-01-01
Among the first places to be affected by the massive tidal wave that ripped across the Indian Ocean on December 26, 2004, were the Andaman Islands. Located approximately 850 kilometers north of the epicenter of the earthquake that triggered the tsunami, the islands were not only among the first land masses to be swept under the wave, they have also been rattled by a series of aftershocks. Administrated by the Indian government, about 300,000 people live on the remote island chain, including several indigenous tribes. As of January 3, over 6,000 were confirmed dead or missing in the Andaman Islands. This Moderate Resolution Imaging Spectroradiometer (MODIS) image shows the Andaman Islands on January 3, 2005. Compared to previous images of the islands, the beaches along the west side of the islands have been stripped bare, leaving a strip of bright tan land along the coast. The change is most notable on North Sentinel Island, home of the Sentinelese aboriginals, and on Interview Island, where the formerly green coastline has been replaced with an abnormally bright ring of bare sand. The large image reveals additional damage along all the islands of the Andaman chain.
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Gochfeld, Michael; Jeitner, Christian; Burke, Sean; Volz, Conrad D.; Snigaroff, Ronald; Snigaroff, Daniel; Shukla, Tara; Shukla, Sheila
2014-01-01
Levels of mercury and other contaminants should be lower in birds nesting on isolated oceanic islands and at high latitudes without any local or regional sources of contamination, compared to more urban and industrialized temperate regions. We examined concentrations of arsenic, cadmium, chromium, lead, manganese, mercury and selenium in the eggs, and the feathers of fledgling and adult glaucous-winged gulls (Larus glaucescens) nesting in breeding colonies on Adak, Amchitka, and Kiska Islands in the Aleutian Chain of Alaska in the Bering Sea/North Pacific. We tested the following null hypotheses: 1) There were no differences in metal levels among eggs and feathers of adult and fledgling glaucous-winged gulls, 2) There were no differences in metal levels among gulls nesting near the three underground nuclear test sites (Long Shot 1965, Milrow 1969, Cannikin 1971) on Amchitka, 3) There were no differences in metal levels among the three islands, and 4) There were no gender-related differences in metal levels. All four null hypotheses were rejected at the 0.05 level, although there were few differences among the three test sites on Amchitka. Eggs had the lowest levels of cadmium, lead, and mercury, and the feathers of adults had the lowest levels of selenium. Comparing only adults and fledglings, adults had higher levels of cadmium, chromium, lead and mercury, and fledglings had higher levels of arsenic, manganese and selenium. There were few consistent interisland differences, although levels were generally lower for eggs and feathers from gulls on Amchitka compared to the other islands. Arsenic was higher in both adult feathers and eggs from Amchitka compared to Adak, and chromium and lead were higher in adult feathers and eggs from Adak compared to Amchitka. Mercury and arsenic, and chromium and manganese levels were significantly correlated in the feathers of both adult and fledgling gulls. The feathers of males had significantly higher levels of chromium and
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LaDouceur, E E B; Anderson, M; Ritchie, B W; Ciembor, P; Rimoldi, G; Piazza, M; Pesti, D; Clifford, D L; Giannitti, F
2015-11-01
Aleutian disease virus (ADV, Amdovirus, Parvoviridae) primarily infects farmed mustelids (mink and ferrets) but also other fur-bearing animals and humans. Three Aleutian disease (AD) cases have been described in captive striped skunks; however, little is known about the relevance of AD in free-ranging carnivores. This work describes the pathological findings and temporospatial distribution in 7 cases of AD in free-ranging striped skunks. All cases showed neurologic disease and were found in a 46-month period (2010-2013) within a localized geographical region in California. Lesions included multisystemic plasmacytic and lymphocytic inflammation (ie, interstitial nephritis, myocarditis, hepatitis, meningoencephalitis, pneumonia, and splenitis), glomerulonephritis, arteritis with or without fibrinoid necrosis in several organs (ie, kidney, heart, brain, and spleen), splenomegaly, ascites/hydrothorax, and/or encephalomalacia with cerebral microangiopathy. ADV infection was confirmed in all cases by specific polymerase chain reaction and/or in situ hybridization. The results suggest that AD is an emerging disease in free-ranging striped skunks in California. © The Author(s) 2014.
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Development of a Peptide ELISA for the Diagnosis of Aleutian Mink Disease
Wang, Yang; Lu, Rongguang; Hu, Bo; Lv, Shuang; Xue, Xianghong; Li, Xintong; Ling, Mingyu; Fan, Sining; Zhang, Hailing; Yan, Xijun
2016-01-01
Aleutian disease (AD) is a common immunosuppressive disease in mink farms world-wide. Since the 1980s, counterimmunoelectrophoresis (CIEP) has been the main detection method for infection with the Aleutian Mink Disease Virus (AMDV). In this study, six peptides derived from the AMDV structural protein VP2 were designed, synthesized, and used as ELISA antigens to detect anti-AMDV antibodies in the sera of infected minks. Serum samples were collected from 764 minks in farms from five different provinces, and analyzed by both CIEP (a gold standard) and peptide ELISA. A peptide designated P1 (415 aa–433 aa) exhibited good antigenicity. A novel ELISA was developed using ovalbumin-linked peptide P1 to detect anti-AMDV antibodies in mink sera. The sensitivity and specificity of the peptide ELISA was 98.0% and 97.5%, respectively. Moreover, the ELISA also detected 342 early-stage infected samples (negative by CIEP and positive by PCR), of which 43.6% (149/342) were true positives. These results showed that the peptide ELISA had better sensitivity compared with CIEP, and therefore could be preferable over CIEP for detecting anti-AMDV antibodies in serological screening. PMID:27802320
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Nutrition in the Great East Japan Earthquake Disaster.
Amagai, Teruyoshi; Ichimaru, Satomi; Tai, Mayumi; Ejiri, Yutaka; Muto, Atsushi
2014-10-01
The Great East Japan Earthquake Disaster (GEJED) struck the northeast region of Honshu, the main island of Japan, on March 11, 2011. This mega-disaster claimed more than 15,000 lives, with approximately 3000 later deaths being disaster related. The GEJED consisted of a mega-earthquake, tsunami, and nuclear accident. Survivors living in temporary shelters might have received insufficient levels of vitamins, with the exception of vitamin B1, which appeared to be overestimated, and excess levels of sodium. However, scientific data collection and surveys following the GEJED were extremely limited. This experience highlights the need to prepare an “emergency nutrition assessment” system for optimal nutrition in future disasters.
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NASA Astrophysics Data System (ADS)
Kato, T.; Ito, T.; Abidin, H. Z.; Agustan, A.
2006-12-01
A large earthquake along a plate boundary occurred in the south of Java Island on July 17, 2006, whose magnitude was 7.7 (USGS) and caused significant tsunami. We made GPS observations and tsunami heights measurements during the period from July 24 to August 1, 2006. The earthquake seems to be due to an interplate low angle reverse faulting (e.g. Yagi, 2006). Yet, there would be a possibility of high angle faulting within the subducting lithosphere (e.g., Yamanaka, 2006). Crustal deformation distribution due to the earthquake, aided by tsunami heights measurements, might clarify which would be the case. We occupied 29 sites by GPS in the area of southern Java Island encompassing the area from 107.8E to 109.50E. These sites were occupied once before the earthquake so that co-seismic displacements might be seen. If we assume that the slip on the fault surface is as that estimated assuming magnitude to be 7.7, co- seismic displacements would be as small as a few centimeters or less. However, the tsunami heights measurements at 11 sites that were conducted along with the GPS observation were 6-7m along the southern coast of Java Islands and indicates that the observed heights are systematically higher than that estimated from numerical simulations (e.g., Koshimura, 2006). This might suggest that fault offsets have been larger nearly double - than that estimated using seismic analysis. If this is the case, the co-seismic crustal movements might be larger than above estimation. This might lead us to an idea that the rupture was very slow and did not radiate enough seismic energy to underestimate the earthquake magnitude. If this is the case, the earthquake might have been a "tsunami earthquake" that is similar to the one that occurred on June 2, 1994 in the east of the present earthquake.
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Amplitude of foreshocks as a possible seismic precursor to earthquakes
Lindh, A.G.
1978-01-01
In recent years, we have made significant progress in being able to recognize the long-range pattern of events that precede large earthquakes. For example, in a recent issue of the Earthquake Information Bulletin, we saw how the pioneering work of S.A. Fedotov of the U.S.S.R in the Kamchatka-Kurile Islands region has been applied worldwide to forecast where large, shallow earthquakes might occur in the next decades. Indeed, such a "seismic gap" off the coast of Alaska was filled by the 1972 Sitka earthquake. Promising results are slowly accumulating from other techniques that suggest that intermediate-term precursors might also be seen: among these are tilt and geomagnetic anomalies and anomalous land uplift. But the crucial point remains that short-term precursors (days to hours) will be needed in many cases if there is to be a significant saving of lives.
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Detection of large prehistoric earthquakes in the pacific northwest by microfossil analysis.
Mathewes, R W; Clague, J J
1994-04-29
Geologic and palynological evidence for rapid sea level change approximately 3400 and approximately 2000 carbon-14 years ago (3600 and 1900 calendar years ago) has been found at sites up to 110 kilometers apart in southwestern British Columbia. Submergence on southern Vancouver Island and slight emergence on the mainland during the older event are consistent with a great (magnitude M >/= 8) earthquake on the Cascadia subduction zone. The younger event is characterized by submergence throughout the region and may also record a plate-boundary earthquake or a very large crustal or intraplate earthquake. Microfossil analysis can detect small amounts of coseismic uplift and subsidence that leave little or no lithostratigraphic signature.
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NASA Astrophysics Data System (ADS)
Ku, C. S.; You, S. H.; Kuo, Y. T.; Huang, B. S.; Wu, Y. M.; Chen, Y. G.; Taylor, F. W.
2015-12-01
A MW 8.1 earthquake occurred on 1 April 2007 in the western Solomon Islands. Following this event, a damaging tsunami was induced and hit the Island Gizo where the capital city of Western Province of Solomon Islands located. Several buildings of this city were destroyed and several peoples lost their lives during this earthquake. However, during this earthquake, no near source seismic instrument has been installed in this region. The seismic evaluations for the aftershock sequence, the possible earthquake early warning and tsunami warning were unavailable. For the purpose of knowing more detailed information about seismic activity in this region, we have installed 9 seismic stations (with Trillium 120PA broadband seismometer and Q330S 24bit digitizer) around the rupture zone of the 2007 earthquake since September of 2009. Within a decade, it has been demonstrated both theoretically and experimentally that the Green's function or impulse response between two seismic stations can be retrieved from the cross-correlation of ambient noise. In this study, 6 stations' observations which are more complete during 2011/10 ~ 2012/12 period, were selected for the purpose of the cross-correlation analysis of ambient seismic noise. The group velocities at period 2-20 seconds of 15 station-pairs were extracted by using multiple filter technique (MFT) method. The analyzed results of this study presented significant results of group velocities with higher frequency contents than other studies (20-60 seconds in usually cases) and opened new opportunities to study the shallow crustal structure of the western Solomon Islands.
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NASA Astrophysics Data System (ADS)
Becel, A.; Shillington, D. J.; Nedimovic, M. R.; Keranen, K. M.; Li, J.; Webb, S. C.; Kuehn, H.
2013-12-01
Structure in the overriding plate is one of the parameters that may increase the tsunamigenic potential of a subduction zone but also influence the seismogenic behavior and segmentation of great earthquake rupture. The Alaska-Aleutian margin is characterized by along-strike changes in plate interface coupling over relatively small distances. Here, we present trench normal multichannel seismic (MCS) profiles acquired across the Shumagin gap that has not broken in many decades and appears to be weakly coupled. The high fold, deep penetration (636 channel, 8-km long streamer, 6600 cu.in airgun source) MCS data were acquired as part of the ALEUT project. This dataset gives us critical new constraints on the interplate boundary that can be traced over ~100 km distance beneath the forearc with high variation in its reflection response with depth. These profiles also reveal the detailed upper plate fault structure and forearc morphology. Clear reflections in the overriding plate appear to delineate one or more large faults that cross the shelf and the upper slope. These faults are observed 75 km back from the trench and seem to branch at depth and connect to the plate interface within this gap at ~11 s twtt. We compare the reflective structure of these faults to that of the plate boundary and examine where it intersects the megathrust with respect of the expected downdip limit of coupling. We also compare this major structure with the seismicity recorded in this sector. The imaged fault system is associated with a large deep basin (~6s twt) that is an inherited structure formed during the pre-Aleutian period. Basins faults appear to have accommodated primarily normal motion, although folding of sediments near the fault and complicated fault geometries in the shallow section may indicate that this fault has accommodated other types of motion during its history that may reflect the stress-state at the megathrust over time. The deformation within the youngest sediment also
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USGS contributions to earthquake and tsunami monitoring in the Caribbean Region
NASA Astrophysics Data System (ADS)
McNamara, D.; Caribbean Project Team, U.; Partners, C.
2007-05-01
USGS Caribbean Project Team: Lind Gee, Gary Gyure, John Derr, Jack Odum, John McMillan, David Carver, Jim Allen, Susan Rhea, Don Anderson, Harley Benz Caribbean Partners: Christa von Hillebrandt-Andrade-PRSN, Juan Payero ISU-UASD,DR, Eduardo Camacho - UPAN, Panama, Lloyd Lynch - SRU,Gonzalo Cruz - UNAH,Honduras, Margaret Wiggins-Grandison - Jamaica, Judy Thomas - CERO Barbados, Sylvan McIntyre - NADMA Grenada, E. Bermingham - STRI. The magnitude-9 Sumatra-Andaman Islands earthquake of December 26, 2004, increased global awareness of the destructive hazard posed by earthquakes and tsunamis. In response to this tragedy, the US government undertook a collaborative project to improve earthquake and tsunami monitoring along a major portion of vulnerable coastal regions, in the Caribbean Sea, the Gulf of Mexico, and the Atlantic Ocean. Seismically active areas of the Caribbean Sea region pose a tsunami risk for Caribbean islands, coastal areas along the Gulf of Mexico, and the Atlantic seaboard of North America. Nearly 100 tsunamis have been reported for the Caribbean region in the past 500 years, including 14 tsunamis reported in Puerto Rico and the U.S. Virgin Islands. Partners in this project include the United States Geological Survey (USGS), the Smithsonian Institute, the National Oceanic and Aeronautic Administration (NOAA), and several partner institutions in the Caribbean region. This presentation focuses on the deployment of nine broadband seismic stations to monitor earthquake activity in the Caribbean region that are affiliated with the Global Seismograph Network (GSN). By the end of 2006, five stations were transmitting data to the USGS National Earthquake Information Service (NEIS), and regional partners through Puerto Rico seismograph network (PRSN) Earthworm systems. The following stations are currently operating: SDDR - Sabaneta Dam Dominican Republic, BBGH - Gun Hill Barbados, GRGR - Grenville, Grenada, BCIP - Barro Colorado, Panama, TGUH - Tegucigalpa
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NASA Astrophysics Data System (ADS)
Valenciano, J.; Angenent, J.; Marshall, J. S.; Clark, K.; Litchfield, N. J.
2017-12-01
The Hikurangi subduction margin along the east coast of the North Island, New Zealand accommodates oblique convergence of the Pacific Plate westward beneath the Australian plate at 45 mm/yr. Pronounced forearc uplift occurs at the southern end of the margin along the Wairarapa coast, onshore of the subducting Hikurangi plateau. Along a narrow coastal lowland, a series of uplifted Holocene marine terraces and beach ridges preserve a geologic record of prehistoric coseismic uplift events. In January 2017, we participated in the Research Experience for Undergraduates (REU) program of the NSF SHIRE Project (Subduction at Hikurangi Integrated Research Experiment). We visited multiple coastal sites for reconnaissance fieldwork to select locations for future in-depth study. For the coastline between Flat Point and Te Kaukau Point, we used airborne LiDAR data provided by Land Information New Zealand (LINZ) to create ArcGIS digital terrain models for mapping and correlating uplifted paleo-shorelines. Terrace elevations derived from the LiDAR data were calibrated through the use of Real Time Kinematic (RTK) GPS surveying at one field site (Glenburn Station). Prior field mapping and radiocarbon dating results (Berryman et al., 2001; Litchfield and Clark, 2015) were used to guide our LiDAR mapping efforts. The resultant maps show between four and seven uplifted terraces and associated beach ridges along this coastal segment. At some sites, terrace mapping and lateral correlation are impeded by discontinuous exposures and the presence of landslide debris, alluvial fan deposits, and sand dunes. Tectonic uplift along the southern Hikurangi margin is generated by a complex interaction between deep megathrust slip and shallow upper-plate faulting. Each uplifted Holocene paleo-shoreline is interpreted to represent a single coseismic uplift event. Continued mapping, surveying, and age dating may help differentiate between very large margin-wide megathrust earthquakes (M8.0-9.0+) and
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The Aleutian Islands Campaign: The Strengths and Weaknesses of Its Planning Process and Execution
2014-05-22
Even Major General Simon B. Buckner Jr ., the Alaska Defense Commander (ADC), said in 1941, “we’re not even the second team up here–we’re a sandlot...theater strategy, to support the final assaults on Attu and Kiska. Historians Mark Roehrs and William Renzi assert that the concept of island...United States Army in World War II (Washington, DC: United States Government Printing Office, 1959), 190-96; Mark D. Roehrs and William A. Renzi, World
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Failure of a massive earthquake-induced landslide dam in Papua New Guinea
King, J. P.; Loveday, I. C.; Schuster, R.L.
1987-01-01
This article discusses the recent occurrence of a large earthquake-induced landslide that dammed the Bairaman River in the interior of hte island of New Britian, Papua New Guinea, and the subsequent overtopping and failure of this landslide dam.
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Haeussler, Peter J.; Witter, Robert C.; Wang, Kelin
2015-01-01
The 28 October 2012 Mw 7.8 Haida Gwaii earthquake was a megathrust earthquake along the very obliquely convergent Queen Charlotte margin of British Columbia, Canada. Coseismic deformation is not well constrained by geodesy, with only six Global Positioning System (GPS) sites and two tide gauge stations within 250 km of the rupture area. To better constrain vertical coseismic deformation, we measured the upper growth limits of two sessile intertidal organisms, which are controlled by physical conditions, relative to sea level at 25 sites 5 months after the earthquake. We measured the positions of rockweed (Fucus distichus, 617 observations) and the common acorn barnacle (Balanus balanoides, 686 observations). The study focused on the western side of the islands where rupture models indicated that the greatest amount of vertical displacement, but we also investigated sites well away from the inferred rupture area to provide a control on the upper limit of the organisms unaffected by vertical displacement. We also made 322 measurements of sea level to relate the growth limits to a tidal datum using the TPXO7.2 tidal model, rather than ellipsoid heights determined by GPS. Three methods of examining the data all indicate 0.4–0.6 m subsidence along the western coast of Moresby Island as a result of the 28 October 2012 Haida Gwaii earthquake. Our data are, within the errors, consistent with data from two campaign GPS sites along the west coast of Haida Gwaii and with rupture models that indicate megathrust rupture offshore, but not beneath, the islands.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Ismullah M, Muh. Fawzy, E-mail: mallaniung@gmail.com; Lantu,; Aswad, Sabrianto
Indonesia is the meeting zone between three world main plates: Eurasian Plate, Pacific Plate, and Indo – Australia Plate. Therefore, Indonesia has a high seismicity degree. Sulawesi is one of whose high seismicity level. The earthquake centre lies in fault zone so the earthquake data gives tectonic visualization in a certain place. This research purpose is to identify Sulawesi tectonic model by using earthquake data from 1993 to 2012. Data used in this research is the earthquake data which consist of: the origin time, the epicenter coordinate, the depth, the magnitude and the fault parameter (strike, dip and slip). Themore » result of research shows that there are a lot of active structures as a reason of the earthquake in Sulawesi. The active structures are Walannae Fault, Lawanopo Fault, Matano Fault, Palu – Koro Fault, Batui Fault and Moluccas Sea Double Subduction. The focal mechanism also shows that Walannae Fault, Batui Fault and Moluccas Sea Double Subduction are kind of reverse fault. While Lawanopo Fault, Matano Fault and Palu – Koro Fault are kind of strike slip fault.« less
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Irian Jaya earthquake and tsunami cause serious damage
NASA Astrophysics Data System (ADS)
Imamura, Fumihiko; Subandono, D.; Watson, G.; Moore, A.; Takahashi, T.; Matsutomi, H.; Hidayat, R.
On February 17,1996, at 0559 UT, a major earthquake with moment magnitude (Mw) 7.9 killed 107 people and caused major damage at Biak Island, 30-40 km southwest of the earthquake's epicenter (Figures 1 and 2). A devastating tsunami washed away all of the houses at Korim, a small village located in a narrow bay facing directly towards the incoming wave, and it left behind clear evidence of sand erosion and deposition that indicated how far the tsunami advanced. An unexpectedly large tsunami run-up of 7.7 m was measured at Wardo in western Biak, which faces away from the primary tsunami source. This high run-up may have been caused by a local submarine landslide.
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Listening to the 2011 magnitude 9.0 Tohoku-Oki, Japan, earthquake
Peng, Zhigang; Aiken, Chastity; Kilb, Debi; Shelly, David R.; Enescu, Bogdan
2012-01-01
The magnitude 9.0 Tohoku-Oki, Japan, earthquake on 11 March 2011 is the largest earthquake to date in Japan’s modern history and is ranked as the fourth largest earthquake in the world since 1900. This earthquake occurred within the northeast Japan subduction zone (Figure 1), where the Pacific plate is subducting beneath the Okhotsk plate at rate of ∼8–9 cm/yr (DeMets et al. 2010). This type of extremely large earthquake within a subduction zone is generally termed a “megathrust” earthquake. Strong shaking from this magnitude 9 earthquake engulfed the entire Japanese Islands, reaching a maximum acceleration ∼3 times that of gravity (3 g). Two days prior to the main event, a foreshock sequence occurred, including one earthquake of magnitude 7.2. Following the main event, numerous aftershocks occurred around the main slip region; the largest of these was magnitude 7.9. The entire foreshocks-mainshock-aftershocks sequence was well recorded by thousands of sensitive seismometers and geodetic instruments across Japan, resulting in the best-recorded megathrust earthquake in history. This devastating earthquake resulted in significant damage and high death tolls caused primarily by the associated large tsunami. This tsunami reached heights of more than 30 m, and inundation propagated inland more than 5 km from the Pacific coast, which also caused a nuclear crisis that is still affecting people’s lives in certain regions of Japan.
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The Solomon Islands tsunami of 6 February 2013 field survey in the Santa Cruz Islands
NASA Astrophysics Data System (ADS)
Fritz, H. M.; Papantoniou, A.; Biukoto, L.; Albert, G.
2013-12-01
On February 6, 2013 at 01:12:27 UTC (local time: UTC+11), a magnitude Mw 8.0 earthquake occurred 70 km to the west of Ndendo Island (Santa Cruz Island) in the Solomon Islands. The under-thrusting earthquake near a 90° bend, where the Australian plate subducts beneath the Pacific plate generated a locally focused tsunami in the Coral Sea and the South Pacific Ocean. The tsunami claimed the lives of 10 people and injured 15, destroyed 588 houses and partially damaged 478 houses, affecting 4,509 people in 1,066 households corresponding to an estimated 37% of the population of Santa Cruz Island. A multi-disciplinary international tsunami survey team (ITST) was deployed within days of the event to document flow depths, runup heights, inundation distances, sediment and coral boulder depositions, land level changes, damage patterns at various scales, performance of the man-made infrastructure and impact on the natural environment. The 19 to 23 February 2013 ITST covered 30 locations on 4 Islands: Ndendo (Santa Cruz), Tomotu Noi (Lord Howe), Nea Tomotu (Trevanion, Malo) and Tinakula. The reconnaissance completely circling Ndendo and Tinakula logged 240 km by small boat and additionally covered 20 km of Ndendo's hard hit western coastline by vehicle. The collected survey data includes more than 80 tsunami runup and flow depth measurements. The tsunami impact peaked at Manoputi on Ndendo's densely populated west coast with maximum tsunami height exceeding 11 m and local flow depths above ground exceeding 7 m. A fast tide-like positive amplitude of 1 m was recorded at Lata wharf inside Graciosa Bay on Ndendo Island and misleadingly reported in the media as representative tsunami height. The stark contrast between the field observations on exposed coastlines and the Lata tide gauge recording highlights the importance of rapid tsunami reconnaissance surveys. Inundation distance and damage more than 500 m inland were recorded at Lata airport on Ndendo Island. Landslides were
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Long- and short-term triggering and modulation of mud volcano eruptions by earthquakes
NASA Astrophysics Data System (ADS)
Bonini, Marco; Rudolph, Maxwell L.; Manga, Michael
2016-03-01
Earthquakes can trigger the eruption of mud. We use eruptions in Azerbaijan, Italy, Romania, Japan, Andaman Islands, Pakistan, Taiwan, Indonesia, and California to probe the nature of stress changes that induce new eruptions and modulate ongoing eruptions. Dynamic stresses produced by earthquakes are usually inferred to be the dominant triggering mechanism; however static stress changes acting on the feeder systems of mud volcanoes may also play a role. In Azerbaijan, eruptions within 2-10 fault lengths from the epicenter are favored in the year following earthquakes where the static stress changes cause compression of the mud source and unclamp feeder dikes. In Romania, Taiwan, and some Italian sites, increased activity is also favored where the static stress changes act to unclamp feeder dikes, but responses occur within days. The eruption in the Andaman Islands, and those of the Niikappu mud volcanoes, Japan are better correlated with amplitude of dynamic stresses produced by seismic waves. Similarly, a new island that emerged off the coast of Pakistan in 2013 was likely triggered by dynamic stresses, enhanced by directivity. At the southern end of the Salton Sea, California earthquakes increase the gas flux at small mud volcanoes. Responses are best correlated with dynamic stresses. The comparison of responses in these nine settings indicates that dynamic stresses are most often correlated with triggering, although permanent stress changes as small as, and possibly smaller than, 0.1 bar may be sufficient to also influence eruptions. Unclamping stresses with magnitude similar to Earth tides (0.01 bar) persist over time and may play a role in triggering delayed responses. Unclamping stresses may be important contributors to short-term triggering only if they exceed 0.1-1 bar.
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NASA Astrophysics Data System (ADS)
Paris, Raphael; Wassmer, Patrick; Roger, Jean; Loevenbruck, Anne
2010-05-01
Significant earthquakes occur along the north Algerian and Carboneras faults (e.g. Djijelli 1865, Zemmouri 2003) and they may generate tsunamis in the western Mediterranean Basin and Alboran Sea, where tsunami hazard are poorly documented. The coast of southern Spain and Balearic Islands are densely populated, with touristic areas and important harbors. The 2003 event generated a small tsunami in the Balearic Islands (ships were moved by oscillations during more than 2 hours in some harbors). Reicherter et al. (2009) found evidences of two past tsunamis in lagoon of the Cabo de Gata (near Almeria), which they ascribed to the 1522 earthquake and an earlier event (< 850 BP). Field surveys along the coasts of Mallorca and Menorca islands revealed few evidences of past tsunamis. Thin sandy layers with marine bioclasts, possibly deposited by tsunamis, were found in three areas at altitudes always lower than 2m. Boulder clusters were found along the southern coast of Mallorca, but they could have been deposited by storms as well. These investigations are realized in the framework of the MAREMOTI project, funded by the French ANR and leaded by the CEA - DASE. Reicherter, K., Becker-Heidmann, P., 2009. Tsunami deposits in the western Mediterranean: remains of the 1522 Almeria earthquake? Geological Society Special Publications, London, 316, 217-235.
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Burger, Joanna; Gochfeld, Michael; Pletnikoff, Karen
2009-05-01
Increasingly managers and scientists are recognizing that solving environmental problems requires the inclusion of a wide range of disciplines, governmental agencies, Native American tribes, and other stakeholders. Usually such inclusion involves communication at the problem-formulation phase, and at the end to report findings. This paper examines participatory research, the differences between the traditional stakeholder involvement method of communication (often one-way, at the beginning and the end), compared to full collaboration, where parties are actively involved in the scientific process. Using the Department of Energy's (DOE) Amchitka Island in the Aleutians as a case study, we demonstrate that the inclusion of Aleut people throughout the process resulted in science that was relevant not only to the agency's needs and to the interested and affected parties, but that led to a solution. Amchitka Island was the site of three underground nuclear tests from 1965 to 1971, and virtually no testing of radionuclide levels in biota, subsistence foods, or commercial fish was conducted after the 1970s. When DOE announced plans to close Amchitka, terminating its managerial responsibility, without any further testing of radionuclide levels in biota, there was considerable controversy, which resulted in the development of a Science Plan to assess the potential risks to the marine environment from the tests. The Consortium for Risk Evaluation with Stakeholder Participation (CRESP) was the principle entity that developed and executed the science plan. Unlike traditional science, CRESP embarked on a process to include the Alaskan Natives of the Aleutian Islands (Aleuts), relevant state and federal agencies, and other stakeholders at every phase. Aleuts were included in the problem-formulation, research design refinement, the research, analysis of data, dissemination of research findings, and public communication. This led to agreement with the results, and to developing a
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Talbot, S. S.; Talbot, S.L.; Walker, L.R.
2010-01-01
We studied the vegetation of Kasatochi Island, central Aleutian Islands, to provide a general field assessment regarding the survival of plants, lichens, and fungi following a destructive volcanic eruption that occurred in 2008. Plant community data were analyzed using multivariate methods to explore the relationship between pre- and post-eruption plant cover; 5 major vegetation types were identified: Honckenya peploides beach, Festuca rubra cliff shelf, Lupinus nootkatensisFestuca rubra meadow, Leymus mollis bluff ridge (and beach), and Aleuria aurantia lower slope barrens. Our study provided a very unusual glimpse into the early stages of plant primary succession on a remote island where most of the vegetation was destroyed. Plants that apparently survived the eruption dominated early plant communities. Not surprisingly, the most diverse post-eruption community most closely resembled a widespread pre-eruption type. Microhabitats where early plant communities were found were distinct and apparently crucial in determining plant survival. Comparison with volcanic events in related boreal regions indicated some post-eruption pattern similarities. ?? 2010 Regents of the University of Colorado.
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Living on Active Volcanoes - The Island of Hawai'i
Heliker, Christina; Stauffer, Peter H.; Hendley, James W.
1997-01-01
People on the Island of Hawai'i face many hazards that come with living on or near active volcanoes. These include lava flows, explosive eruptions, volcanic smog, damaging earthquakes, and tsunamis (giant seawaves). As the population of the island grows, the task of reducing the risk from volcano hazards becomes increasingly difficult. To help protect lives and property, U.S. Geological Survey (USGS) scientists at the Hawaiian Volcano Observatory closely monitor and study Hawai'i's volcanoes and issue timely warnings of hazardous activity.
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NASA Astrophysics Data System (ADS)
Kobayashi, Akio; Yoshida, Akio; Yamamoto, Takeyasu; Takayama, Hiromi
2005-06-01
Transient crustal deformation occurred in the regions of Kanto and Tokai during the seismo-volcanic event in the northern Izu Islands in 2000. In our investigation of the observed deformation, we constructed an optimum-source model of the event between Miyake and Kozu Islands. We then made an inversion analysis of the differences between the observed displacement field and the calculated displacement field from the optimum model, assuming that the differences were caused by the changes in the interplate coupling beneath the Tokai region. From the inversion analysis of data for each of three-month periods, May to August, June to September, and July to October, we found decreased interplate coupling in the early stages of the 2000 event. In the first stage, either a slow slip or a temporary suspension of the plate subduction occurred in the focal region of the anticipated Tokai earthquake. The area then extended to the west and, finally, a slow slip exceeded the secular convergence velocity on the plate interface near Lake Hamana in the fall of 2000. We believe this ongoing slow slip began in August or early September 2000.
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Subduction dynamics: From the trench to the core-mantle boundary
NASA Astrophysics Data System (ADS)
Kincaid, Chris
1995-07-01
Subduction occurs along convergent plate boundaries where one of the colliding lithospheric plates descends into the mantle. Subduction zones are recognized where plates converge at ˜2-15 cm/yr, although well developed trenches and volcanic arcs (e.g. the line of active volcanoes lying parallel to most ocean trenches, such as the Aleutian Islands in the North Pacific) occur when convergence rates are higher, 4-10 cm/yr. This report is meant to provide a brief review on the general topic of subduction dynamics. A recent spin on subduction studies is the growing realization that the need to understand this global Earth process may be argued not only on purely scientific grounds, but also in terms of societal relevance. While subducting slabs of oceanic lithosphere clearly provide the dominant driving force for mantle dynamics and plate tectonics, over half of the Earth's present 40,000 km of subduction zones are associated with continental margins where a large and rapidly increasing percentage of the Earth's population resides. Subductioninduced hazards along active continental margins include those associated with volcanic hazards (Blong, 1984; Tilling, 1989) such as lava flows, pyroclastic flows and ash fallout and tectonic processes, such as faulting, tsunamis and earthquakes. With regards to earthquake hazards, all of the great (magnitude >9) earthquakes in recorded history have occurred at subduction zones, with 50% of all energy released since 1900 being in four events (1964-Alaska; 1960-Chile; 1957- Aleutians; 1952-Kamchatka). Subduction zone hazards have significant impact on long time scales, such as contributions to global climate change (Robock, 1991; Simarski, 1992; Johnson, 1993; Bluth et al., 1993) and short time scales such as airline safety (Casadevall, 1992). Moreover, accretionary wedges are important in terms of resource potential and trenches have occasionally been suggested as nuclear waste disposal sites.
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Aseismic blocks and destructive earthquakes in the Aegean
NASA Astrophysics Data System (ADS)
Stiros, Stathis
2017-04-01
Aseismic areas are not identified only in vast, geologically stable regions, but also within regions of active, intense, distributed deformation such as the Aegean. In the latter, "aseismic blocks" about 200m wide were recognized in the 1990's on the basis of the absence of instrumentally-derived earthquake foci, in contrast to surrounding areas. This pattern was supported by the available historical seismicity data, as well as by geologic evidence. Interestingly, GPS evidence indicates that such blocks are among the areas characterized by small deformation rates relatively to surrounding areas of higher deformation. Still, the largest and most destructive earthquake of the 1990's, the 1995 M6.6 earthquake occurred at the center of one of these "aseismic" zones at the northern part of Greece, found unprotected against seismic hazard. This case was indeed a repeat of the case of the tsunami-associated 1956 Amorgos Island M7.4 earthquake, the largest 20th century event in the Aegean back-arc region: the 1956 earthquake occurred at the center of a geologically distinct region (Cyclades Massif in Central Aegean), till then assumed aseismic. Interestingly, after 1956, the overall idea of aseismic regions remained valid, though a "promontory" of earthquake prone-areas intruding into the aseismic central Aegean was assumed. Exploitation of the archaeological excavation evidence and careful, combined analysis of historical and archaeological data and other palaeoseismic, mostly coastal data, indicated that destructive and major earthquakes have left their traces in previously assumed aseismic blocks. In the latter earthquakes typically occur with relatively low recurrence intervals, >200-300 years, much smaller than in adjacent active areas. Interestingly, areas assumed a-seismic in antiquity are among the most active in the last centuries, while areas hit by major earthquakes in the past are usually classified as areas of low seismic risk in official maps. Some reasons
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Bakun, William H.; Flores, Claudia H.; ten Brink, Uri S.
2012-01-01
Historical records indicate frequent seismic activity along the north-east Caribbean plate boundary over the past 500 years, particularly on the island of Hispaniola. We use accounts of historical earthquakes to assign intensities and the intensity assignments for the 2010 Haiti earthquakes to derive an intensity attenuation relation for Hispaniola. The intensity assignments and the attenuation relation are used in a grid search to find source locations and magnitudes that best fit the intensity assignments. Here we describe a sequence of devastating earthquakes on the Enriquillo fault system in the eighteenth century. An intensity magnitude MI 6.6 earthquake in 1701 occurred near the location of the 2010 Haiti earthquake, and 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 18 October 1751 MI 7.4–7.5 earthquake, probably located near the eastern end of the fault in the Dominican Republic, followed by the 21 November 1751 MI 6.6 earthquake near Port-au-Prince, Haiti, and the 3 June 1770 MI 7.5 earthquake west of the 2010 earthquake rupture. The 2010 Haiti earthquake may mark the beginning of a new cycle of large earthquakes on the Enriquillo fault system after 240 years of seismic quiescence. The entire Enriquillo fault system appears to be seismically active; Haiti and the Dominican Republic should prepare for future devastating earthquakes.
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Rapid estimate of earthquake source duration: application to tsunami warning.
NASA Astrophysics Data System (ADS)
Reymond, Dominique; Jamelot, Anthony; Hyvernaud, Olivier
2016-04-01
. and Reymond, D. (2014). New Tsunami Forecast Tools for the French Polynesia Tsunami Warning System. Pure Appl. Geophys, 171. DUPUTEL, Z., RIVERA, L., KANAMORI, H. and HAYES, G. (2012). Wphase source inversion for moderate to large earthquakes. Geophys. J. Intl.189, 1125-1147. Kanamori, H. (1972). Mechanism of tsunami earthquakes. Phys. Earth Planet. Inter. 6, 246-259. Kanamori, H. and Rivera, L. (2008). Source inversion of W phase : speeding up seismic tsunami warning. Geophys. J. Intl. 175, 222-238. Newman, A. and Okal, E. (1998). Teleseismic estimates of radiated seismic energy : The E=M0 discriminant for tsunami earthquakes. J. Geophys. Res. 103, 26885-26898. Ni, S., H. Kanamori, and D. Helmberger (2005), Energy radiation from the Sumatra earthquake, Nature, 434, 582. Okal, E.A., and H. Hébert (2007), Far-field modeling of the 1946 Aleutian tsunami, Geophys. J. Intl., 169, 1229-1238. Vallée, M., J. Charléty, A.M.G. Ferreira, B. Delouis, and J. Vergoz, SCARDEC : a new technique for the rapid determination of seismic moment magnitude, focal mechanism and source time functions for large earthquakes using body wave deconvolution, Geophys. J. Int., 184, 338-358, 2011.
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Sedimentology and geochemistry of surface sediments, outer continental shelf, southern Bering Sea
Gardner, J.V.; Dean, W.E.; Vallier, T.L.
1980-01-01
Present-day sediment dynamics, combined with lowerings of sea level during the Pleistocene, have created a mixture of sediments on the outer continental shelf of the southern Bering Sea that was derived from the Alaskan Mainland, the Aleutian Islands, and the Pribilof ridge. Concentrations of finer-grained, higher-organic sediments in the region of the St. George basin have further modified regional distribution patterns of sediment composition. Q-mode factor analysis of 58 variables related to sediment size and composition - including content of major, minor, and trace elements, heavy and light minerals, and clay minerals - reveals three dominant associations of sediment: 1. (1) The most significant contribution, forming a coarse-grained sediment scattered over most of the shelf consists of felsic sediment derived from the generally quartz-rich rocks of the Alaskan mainland. This sediment contains relatively high concentrations of Si, Ba, Rb, quartz, garnet, epidote, metamorphic rock fragments, potassium feldspar, and illite. 2. (2) The next most important group, superimposed on the felsic group consists of andesitic sediment derived from the Aleutian Islands. This more mafic sediment contains relatively high concentrations of Na, Ca, Ti, Sr, V, Mn, Cu, Fe, Al, Co, Zn, Y, Yb, Ga, volcanic rock fragments, glass, clinopyroxene, smectite, and vermiculite. 3. (3) A local group of basaltic sediment, derived from rocks of the Pribilof Islands, is a subgroup of the Aleutian andesite group. Accumulation of fine-grained sediment in St. George basin has created a sediment group containing relatively high concentrations of C, S, U, Li, B, Zr, Ga, Hg, silt, and clay. Sediment of the Aleutian andesite group exhibits a strong gradient, or "plume", with concentrations decreasing away from Unimak Pass and toward St. George basin. The absence of present-day currents sufficient to move even clay-size material as well as the presence of Bering submarine canyon between the Aleutian
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Earthquake design criteria for small hydro projects in the Philippines
DOE Office of Scientific and Technical Information (OSTI.GOV)
Martin, P.P.; McCandless, D.H.; Asce, M.
1995-12-31
The definition of the seismic environment and seismic design criteria of more than twenty small hydro projects in the northern part of the island of Luzon in the Philippines took a special urgency on the wake of the Magnitude 7.7 earthquake that shook the island on July 17, 1990. The paper describes the approach followed to determine design shaking level criteria at each hydro site consistent with the seismic environment estimated at that same site. The approach consisted of three steps: (1) Seismicity: understanding the mechanisms and tectonic features susceptible to generate seismicity and estimating the associated seismicity levels, (2)more » Seismic Hazard: in the absence of an accurate historical record, using statistics to determine the expected level of ground shaking at a site during the operational 100-year design life of each Project, and (3) Criteria Selection: finally and most importantly, exercising judgment in estimating the final proposed level of shaking at each site. The resulting characteristics of estimated seismicity and seismic hazard and the proposed final earthquake design criteria are provided.« less
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NASA Astrophysics Data System (ADS)
Kobayashi, T.; Ohminato, T.; Fujita, E.; Ida, Y.
2002-12-01
The volcanic activity of Miyake-jima started at 18:30 (JST) on June 26, 2000 with large ground deformation and earthquake swarms. The seismic activity started at the southern part of the island. The hypocenter distribution migrated northwestward and slipped away out of the island by early in the morning, June 27. Low frequency (LF) earthquakes with dominant frequencies of 0.2 and 0.4 Hz were first observed in the afternoon of June 27. The LF activity lasted till the first summit eruption on July 8. Earthquake Research Institute of Tokyo University and National Research Institute for Earth Science and Disaster Prevention deployed 3 CMG-3T and 4 STS-2 broadband seismometers in the island. More than 300 LF earthquakes are detected during the period from June 27 to July 8. Most of the LF events whose dominant frequency is 0.2Hz occurred before July 1, while LF events with dominant frequency of 0.4Hz mainly occurred after July 2. We determine hypocenters of these LF events by using the following technique. For each LF event, we assume a source location on a grid point in a homogeneous half-space. A reference station is chosen among all the stations. The cross correlation coefficients are computed between the waveform of the reference station and those of other stations. Then, the coefficients for all the stations are summed. In the same manner, summations of the coefficients are computed grid by grid. A grid point that gives the maximum value of the sum of the coefficients is regarded as the best estimate of the source location of the LF event under consideration. The result shows that hypocenters of LF events are spread over the southern to western part of the island and they migrate from south to the west day by day. Hypocenter migrations associated with volcanic activity have been often reported but usually for short period events. This is one of remarkable cases in which a migration of earthquakes with dominant frequencies as low as 0.2 and 0.4Hz are clearly
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NASA Astrophysics Data System (ADS)
Kent, T.
2011-12-01
The goal of this study is to constrain the most recent thermal alteration of two drill cores (HSB2/HSB4) from the Island of Akutan in the Aleutian Islands of Alaska. These cores are characterized by identifying mineralogy using x-ray diffraction spectra, energy dispersive spectroscopy with a scanning electron microscope and optical mineralogy. This is then compared with the coincident thermal data gathered on site in order to help constrain the most recent thermal activity of this dynamic resource. Using multiple temperature diagnostic minerals and their paragenesis, a relative thermal history is produced of expansive propylitic alteration. When combined with the wireline temperature gradients of the cores a model of downward migration emerges. Shallow occurrences of high temperature minerals that lie above the boiling point to depth curve indicate higher hydrostatic pressures in the past which can be attributed to a combination of glacial effects, including a significant amount of glacial erosion that is recognized due to a lack of significant clay cap to the geothermal resource.
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Repeated Seafloor Geodetic Observation west off Miyake-jima volcanic island
NASA Astrophysics Data System (ADS)
Mochizuki, M.; Sato, M.; Fujita, M.; Katayama, M.; Yoshida, Z.; Yabuki, T.; Asada, A.
2003-12-01
An intensive earthquake swarm started under Miyake-jima island, 180 km south off Japan main island, on June 26, 2000. The earthquake swarm migrated towards northwest off Miyake-jima island, where numerous earthquakes, more than 100,000, were detected within about two months and an extensive crustal deformation was observed by on-land geodetic observations. Inst. of Industrial Science, Univ. of Tokyo and Hydrographic and Oceanographic Dept, Japan Coast Guard deployed three seafloor geodetic reference stations (St.A, St.B & St.C) in triangle area surrounded by three islands, Miyake-jima, Nii-jima and Kouzu-jima islands, in November and December, 2000, and have been conducting observations using these three stations to monitor seafloor deformation for the better understandings of underground magmatic activities. The observations have been conducted thirteen times until present. Fast and quickly varying ocean current in this area prevented us from stable observation. The surface current makes the pole, which connects the GPS antenna and the ship-board transducer, bend. This bending of the pole gave uncertainty to the analyses of locating the positions of the seafloor geodetic reference stations. The pole was replaced new, more rigid pole to overcome the problem in August 2002. The first observation with this new system was conducted at the reference station in the Sagami-bay. Smaller amount of bending with the new pole than that with the old one against both roll and pitch components could be seen in the data from this observation. This shows that the replacement of the pole provided stability to the observation system. We started to adopt the new system to the observation at the three stations west-off Miyake-jima island area, too. Station C, that is located nearest one to the Miyake-jima island, is one where we had most frequent observation after improvement of the system. The observations with the new system have been conducted four times in September, December 2002
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Transformation of tsunami waves passing through the Straits of the Kuril Islands
NASA Astrophysics Data System (ADS)
Kostenko, Irina; Kurkin, Andrey; Pelinovsky, Efim; Zaytsev, Andrey
2015-04-01
Pacific ocean and themselves Kuril Islands are located in the zone of high seismic activity, where underwater earthquakes cause tsunamis. They propagate across Pacific ocean and penetrates into the Okhotsk sea. It is natural to expect that the Kuril Islands reflect the Okhotsk sea from the Pacific tsunami waves. It has long been noted that the historical tsunami appeared less intense in the sea of Okhotsk in comparison with the Pacific coast of the Kuril Islands. Despite the fact that in the area of the Kuril Islands and in the Pacific ocean earthquakes with magnitude more than 8 occur, in the entire history of observations on the Okhotsk sea coast catastrophic tsunami was not registered. The study of the peculiarities of the propagation of historical and hypothetical tsunami in the North-Eastern part of the Pacific ocean was carried out in order to identify level of effect of the Kuril Islands and Straits on them. Tsunami sources were located in the Okhotsk sea and in the Pacific ocean. For this purpose, we performed a series of computational experiments using two bathymetries: 1) with use Kuril Islands; 2) without Kuril Islands. Magnitude and intensity of the tsunami, obtained during numerical simulation of height, were analyzed. The simulation results are compared with the observations. Numerical experiments have shown that in the simulation without the Kuril Islands tsunamis in the Okhotsk sea have higher waves, and in the Central part of the sea relatively quickly damped than in fact. Based on shallow-water equation tsunami numerical code NAMI DANCE was used for numerical simulations. This work was supported by ASTARTE project.
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Reduction of earthquake risk in the united states: Bridging the gap between research and practice
Hays, W.W.
1998-01-01
Continuing efforts under the auspices of the National Earthquake Hazards Reduction Program are under way to improve earthquake risk assessment and risk management in earthquake-prone regions of Alaska, California, Nevada, Washington, Oregon, Arizona, Utah, Wyoming, and Idaho, the New Madrid and Wabash Valley seismic zones in the central United States, the southeastern and northeastern United States, Puerto Rico, Virgin Islands, Guam, and Hawaii. Geologists, geophysicists, seismologists, architects, engineers, urban planners, emergency managers, health care specialists, and policymakers are having to work at the margins of their disciplines to bridge the gap between research and practice and to provide a social, technical, administrative, political, legal, and economic basis for changing public policies and professional practices in communities where the earthquake risk is unacceptable. ?? 1998 IEEE.
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Presumed drowning of Aleutian Canada geese on the Pacific coast of California and Oregon
Springer, Paul F.; Lowe, Roy W.; Stroud, Richard K.; Gullett, Patricia A.
1989-01-01
Carcasses of 42 and 17 Aleutian Canada geese (Branta canadensis leucopareia), a federally listed endangered species, were found on ocean beaches near Crescent City, California, and near Pacific City, Oregon, respectively, following severe storms. Necropsies and other information suggest that the birds were flushed during the storms and somehow entered the water where they were washed into the surf and drowned.
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NASA Astrophysics Data System (ADS)
Yun, S.; Koketsu, K.; Aoki, Y.
2014-12-01
The September 4, 2010, Canterbury earthquake with a moment magnitude (Mw) of 7.1 is a crustal earthquake in the South Island, New Zealand. The February 22, 2011, Christchurch earthquake (Mw=6.3) is the biggest aftershock of the 2010 Canterbury earthquake that is located at about 50 km to the east of the mainshock. Both earthquakes occurred on previously unrecognized faults. Field observations indicate that the rupture of the 2010 Canterbury earthquake reached the surface; the surface rupture with a length of about 30 km is located about 4 km south of the epicenter. Also various data including the aftershock distribution and strong motion seismograms suggest a very complex rupture process. For these reasons it is useful to investigate the complex rupture process using multiple data with various sensitivities to the rupture process. While previously published source models are based on one or two datasets, here we infer the rupture process with three datasets, InSAR, strong-motion, and teleseismic data. We first performed point source inversions to derive the focal mechanism of the 2010 Canterbury earthquake. Based on the focal mechanism, the aftershock distribution, the surface fault traces and the SAR interferograms, we assigned several source faults. We then performed the joint inversion to determine the rupture process of the 2010 Canterbury earthquake most suitable for reproducing all the datasets. The obtained slip distribution is in good agreement with the surface fault traces. We also performed similar inversions to reveal the rupture process of the 2011 Christchurch earthquake. Our result indicates steep dip and large up-dip slip. This reveals the observed large vertical ground motion around the source region is due to the rupture process, rather than the local subsurface structure. To investigate the effects of the 3-D velocity structure on characteristic strong motion seismograms of the two earthquakes, we plan to perform the inversion taking 3-D velocity
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-05-04
... University of Wisconsin, Madison, WI. The human remains were removed from Umnak Island, AK. This notice is... Island, located in the Fox Island group of the eastern Aleutian Islands, AK. These sites included the... probably removed at the direction of the late Dr. William Laughlin from Umnak Island as they were later...
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Burger, Joanna; Gochfeld, Michael; Pletnikoff, Karen
2014-01-01
Increasingly managers and scientists are recognizing that solving environmental problems requires the inclusion of a wide range of disciplines, governmental agencies, Native American tribes, and other stakeholders. Usually such inclusion involves communication at the problem-formulation phase, and at the end to report findings. This paper examines participatory research, the differences between the traditional stakeholder involvement method of communication (often one-way, at the beginning and the end), compared to full collaboration, where parties are actively involved in the scientific process. Using the Department of Energy’s (DOE) Amchitka Island in the Aleutians as a case study, we demonstrate that the inclusion of Aleut people throughout the process resulted in science that was relevant not only to the agency’s needs and to the interested and affected parties, but that led to a solution. Amchitka Island was the site of three underground nuclear tests from 1965 to 1971, and virtually no testing of radionuclide levels in biota, subsistence foods, or commercial fish was conducted after the 1970s. When DOE announced plans to close Amchitka, terminating its managerial responsibility, without any further testing of radionuclide levels in biota, there was considerable controversy, which resulted in the development of a Science Plan to assess the potential risks to the marine environment from the tests. The Consortium for Risk Evaluation with Stakeholder Participation (CRESP) was the principle entity that developed and executed the science plan. Unlike traditional science, CRESP embarked on a process to include the Alaskan Natives of the Aleutian Islands (Aleuts), relevant state and federal agencies, and other stakeholders at every phase. Aleuts were included in the problem-formulation, research design refinement, the research, analysis of data, dissemination of research findings, and public communication. This led to agreement with the results, and to developing
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Abercrombie, R.E.; Webb, T.H.; Robinson, R.; McGinty, P.J.; Mori, J.J.; Beavan, R.J.
2000-01-01
The 1994 Arthur's Pass earthquake (Mw6.7) is the largest in a recent sequence of earthquakes in the central South Island, New Zealand. No surface rupture was observed the aftershock distribution was complex, and routine methods of obtaining the faulting orientation of this earthquake proved contradictory. We use a range of data and techniques to obtain our preferred solution, which has a centroid depth of 5 km, Mo=1.3??1019 N m, and a strike, dip, and rake of 221??, 47??, 112??, respectively. Discrepancies between this solution and the Harvard centroid moment tensor, together with the Global Positioning System (GPS) observations and unusual aftershock distribution, suggest that the rupture may not have occurred on a planar fault. A second, strike slip, subevent on a more northerly striking plane is suggested by these data but neither the body wave modeling nor regional broadband recordings show any complexity or late subevents. We relocate the aftershocks using both one-dimensional and three-dimensional velocity inversions. The depth range of the aftershocks (1-10 km) agrees well with the preferred mainshock centroid depth. The aftershocks near the hypocenter suggest a structure dipping toward the NW, which we interpret to be the mainshock fault plane. This structure and the Harper fault, ???15 km to the south appear to have acted as boundaries to the extensive aftershock zone trending NNW-SSE Most of the ML???5 aftershocks, including the two largest (ML6.1 and ML5.7), clustered near the Harper fault and have strike slip mechanisms consistent with motion on this fault and its conjugates. Forward modeling of the GPS data suggests that a reverse slip mainshock, combined with strike slip aftershock faulting in the south, is able to match the observed displacements. The occurrence of this earthquake sequence implies that the level of seismic hazard in the central South Island is greater than previous estimates. Copyright 2000 by the American Geophysical Union.
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NASA Astrophysics Data System (ADS)
García, Alicia; De la Cruz-Reyna, Servando; Marrero, José M.; Ortiz, Ramón
2016-05-01
Under certain conditions, volcano-tectonic (VT) earthquakes may pose significant hazards to people living in or near active volcanic regions, especially on volcanic islands; however, hazard arising from VT activity caused by localized volcanic sources is rarely addressed in the literature. The evolution of VT earthquakes resulting from a magmatic intrusion shows some orderly behaviour that may allow the occurrence and magnitude of major events to be forecast. Thus governmental decision makers can be supplied with warnings of the increased probability of larger-magnitude earthquakes on the short-term timescale. We present here a methodology for forecasting the occurrence of large-magnitude VT events during volcanic crises; it is based on a mean recurrence time (MRT) algorithm that translates the Gutenberg-Richter distribution parameter fluctuations into time windows of increased probability of a major VT earthquake. The MRT forecasting algorithm was developed after observing a repetitive pattern in the seismic swarm episodes occurring between July and November 2011 at El Hierro (Canary Islands). From then on, this methodology has been applied to the consecutive seismic crises registered at El Hierro, achieving a high success rate in the real-time forecasting, within 10-day time windows, of volcano-tectonic earthquakes.
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Seismotectonics of the 6 February 2012 Mw 6.7 Negros Earthquake, central Philippines
NASA Astrophysics Data System (ADS)
Aurelio, M. A.; Dianala, J. D. B.; Taguibao, K. J. L.; Pastoriza, L. R.; Reyes, K.; Sarande, R.; Lucero, A.
2017-07-01
At 03:49 UTC on the 6th of February 2012, Negros Island in the Visayan region of central Philippines was struck by a magnitude Mw 6.7 earthquake causing deaths of over 50 people and tremendous infrastructure damage leaving hundreds of families homeless. The epicenter was located in the vicinity of the eastern coastal towns of La Libertad and Tayasan of the Province of Negros Oriental. Earthquake-induced surface deformation was mostly in the form of landslides, liquefaction, ground settlement, subsidence and lateral spread. There were no clear indications of a fault surface rupture. The earthquake was triggered by a fault that has not been previously recognized. Earthquake data, including epicentral and hypocentral distributions of main shock and aftershocks, and focal mechanism solutions of the main shock and major aftershocks, indicate a northeast striking, northwest dipping nodal plane with a reverse fault mechanism. Offshore seismic profiles in the Tañon Strait between the islands of Negros and Cebu show a northwest dipping reverse fault consistent in location, geometry and mechanism with the nodal plane calculated from earthquake data. The earthquake generator is here proposed to be named the Negros Oriental Thrust (NOT). Geologic transects established from structural traverses across the earthquake region reveal an east-verging fold-thrust system. In the latitude of Guihulngan, this fold-thrust system is represented by the Razor Back Anticline - Negros Oriental Thrust pair, and by the Pamplona Anticline - Yupisan Thrust pair in the latitude of Dumaguete to the south. Together, these active fold-thrust systems are causing active deformation of the western section of the Visayan Sea Basin under a compressional tectonic regime. This finding contradicts previous tectonic models that interpret the Tañon Strait as a graben, bounded on both sides by normal faults supposedly operating under an extensional regime. The Negros Earthquake and the active fold
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10. Elevation of iconostas at Chapel of St. Sergius of ...
10. Elevation of iconostas at Chapel of St. Sergius of Radonezh; Elevation of iconostas at Chapel of St. Innocent of Irkutsk - Holy Ascension Russian Orthodox Church, Unalaska Island, Unalaska, Aleutian Islands, AK
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The Earthquake Early Warning System in Japan (Invited)
NASA Astrophysics Data System (ADS)
Mori, J. J.; Yamada, M.
2010-12-01
In Japan, the earthquake early warning system (Kinkyu Jishin Sokuhou in Japanese) maintained by the Japan Meterological Agency (JMA) has been in operation and sending pubic information since October 1, 2007. Messages have been broadcast on television and radio to warn of strong shaking to the public. The threshold for broadcasting a message is an estimated intensity of JMA 5 lower, which is approximately equivalent to MM VII to VIII. During the period from October 2007 through August 2010, messages have been sent 9 times for earthquakes of magnitude 5.2 to 7.0. There have been a few instances of significantly over-estimating or under-estimating the predicted shaking, but in general the performance of the system has been quite good. The quality of the detection system depends on the dense network of high-quality seismometers that cover the Japanese Islands. Consequently, the system works very well for events on or close to the 4 main islands, but there is more uncertainty for events near the smaller and more distant islands where the density of instrumentation is much less The Early Warning System is also tied to an extensive education program so that the public can react appropriately in the short amount of time given by the warning. There appears to be good public support in Japan, where people have become accustomed to a high level of fast information on a daily basis. There has also been development of a number of specific safety applications in schools and industry that work off the backbone information provided in the national system.
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2015 Volcanic activity in Alaska—Summary of events and response of the Alaska Volcano Observatory
Dixon, James P.; Cameron, Cheryl E.; Iezzi, Alexandra M.; Wallace, Kristi
2017-09-28
The Alaska Volcano Observatory (AVO) responded to eruptions, volcanic unrest or suspected unrest, and seismic events at 14 volcanic centers in Alaska during 2015. The most notable volcanic activity consisted of continuing intermittent ash eruptions from Cleveland and Shishaldin volcanoes in the Aleutian Islands. Two eruptive episodes, at Veniaminof and Pavlof, on the Alaska Peninsula ended in 2015. During 2015, AVO re-established the seismograph network at Aniakchak, installed six new broadband seismometers throughout the Aleutian Islands, and added a Multiple component Gas Analyzer System (MultiGAS) station on Augustine.
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Connecting slow earthquakes to huge earthquakes.
Obara, Kazushige; Kato, Aitaro
2016-07-15
Slow earthquakes are characterized by a wide spectrum of fault slip behaviors and seismic radiation patterns that differ from those of traditional earthquakes. However, slow earthquakes and huge megathrust earthquakes can have common slip mechanisms and are located in neighboring regions of the seismogenic zone. The frequent occurrence of slow earthquakes may help to reveal the physics underlying megathrust events as useful analogs. Slow earthquakes may function as stress meters because of their high sensitivity to stress changes in the seismogenic zone. Episodic stress transfer to megathrust source faults leads to an increased probability of triggering huge earthquakes if the adjacent locked region is critically loaded. Careful and precise monitoring of slow earthquakes may provide new information on the likelihood of impending huge earthquakes. Copyright © 2016, American Association for the Advancement of Science.
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Tectonic and Magmatic Implications of the Off-Nicobar Earthquake Swarm, Andaman Sea
NASA Astrophysics Data System (ADS)
Kattoju, K. R.; Ray, D.; Mudholkar, A.; Gollu, M. P.; Mathew, R.; Paropkari, A. L.; Kalathil, B.; Ramachandran, R.
2008-12-01
The off Nicobar earthquake swarm, considered as the most energetic earthquake swarm ever observed globally occurred during January 2005 in the Andaman Sea. The swarm was broadly associated with the aftershock effects of the great Mw 9.3 Sumatra - Andaman earthquake of 26 December 2004 that ruptured 1600 kilometres long stretch of the megathrust zone, the longest of any recorded earthquake. The swarm is located within the rupture area that roughly coincides with the after shock distribution and consisted of more than 150 events of magnitude 5 and above, the intense burst of events occurred in a span of 48 hours during 27-28 January 2005. The fault plane solutions indicate both strike-slip and normal fault events. Usually volcanic eruptions precede or accompany the earthquake swarms. The initial reports suggested absence of any volcanic activity associated with the unusual energy release east of Nicobar Islands in the Andaman Sea. A multidisciplinary voyage conducted to the region revealed a cratered seamount located at the center of the most intense burst of events. Unconsolidated aggregates recovered from the flank of the seamount by the TV-guided grab consist of globules with 66 to 97% manganese oxide, indicative of hydrothermal manganese precipitation as a consequence of recent pulses of hydrothermal activity. Evidences from seismicity, morphology, video footage of the seafloor, geochemical analysis of the seabed samples, and the preliminary findings from a sediment core in the vicinity suggest that the cratered seamount has a history of episodic volcanism. The findings are the first documented report of recent submarine volcanism in the Andaman Sea. We infer that the volcano is in a dormant state at present and is connected to the sub-aerial volcanoes of Sumatra and the Barren-Narcondam Island volcanoes of the Andaman Sea.
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NASA Astrophysics Data System (ADS)
Arisa, D.; Heki, K.
2014-12-01
The Izu-Bonin islands lies along the convergent boundary between the subducting Pacific plate (PA) and the overriding Philippine Sea plate (PH) in the western Pacific. Nishimura (2011) found that the back-arc rifting goes on behind the Izu arc by studying the horizontal velocities of GNSS stations on the Izu islands. Here we show that this rifting has accelerated in 2004 using GNSS data at Aogashima, Hachijoujima, and Mikurajima stations. The back-arc rifting behind the Izu islands can be seen as the increasing distance between stations in the Izu-Bonin islands and stations located in the stable part of PH. We found that their movement showed clear acceleration around the third quarter of 2004. Obtaining the Euler vector of the PH is necessary to analyzed the movement of each stations relative to the other stations on the same plate. The analyzing of GPS timeseries leads us to one initial conclusion that some accelerated movement started to occur in the third quarter of 2004. This event was closely related to the earthquake on May 29, 2004 in Nankai Trough and September 5, 2004 earthquake near the triple junction of Sagami Trough. The analyzing process help us to understand that this accelerated movement was not the afterslip of any of these earthquakes, but it was triggering these area to move faster and further than it was. We first rule out the best possible cause by constraining the onset time of the accelerated movement, and correlating it with the earthquakes. May 29, 2004 earthquake (M6.5) at the PA-PH boundary clearly lacked the jump which should mark the onset of the eastward slow movement. Moreover, additional velocity vectors do not converge to the epicenter, and onset time that minimizes the post-fit residual is significantly later than May. We therefore conclude that accelerated movement started in 2004 was not due to the afterslip of interplate earthquake in May 29. On the next step we found that the onset time coincides with the occurrence of
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50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas
Code of Federal Regulations, 2011 CFR
2011-10-01
... Statistical and Reporting Areas 1 Figure 1 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND... Islands Statistical and Reporting Areas ER15NO99.000 b. Coordinates Code Description 300 Russian waters... statistical area is the part of a reporting area contained in the EEZ. [64 FR 61983, Nov. 15, 1999; 65 FR...
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50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas
Code of Federal Regulations, 2010 CFR
2010-10-01
... Statistical and Reporting Areas 1 Figure 1 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND... Islands Statistical and Reporting Areas ER15NO99.000 b. Coordinates Code Description 300 Russian waters... statistical area is the part of a reporting area contained in the EEZ. [64 FR 61983, Nov. 15, 1999; 65 FR...
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Unusually large earthquakes inferred from tsunami deposits along the Kuril trench
Nanayama, F.; Satake, K.; Furukawa, R.; Shimokawa, K.; Atwater, B.F.; Shigeno, K.; Yamaki, S.
2003-01-01
The Pacific plate converges with northeastern Eurasia at a rate of 8-9 m per century along the Kamchatka, Kuril and Japan trenches. Along the southern Kuril trench, which faces the Japanese island of Hokkaido, this fast subduction has recurrently generated earthquakes with magnitudes of up to ???8 over the past two centuries. These historical events, on rupture segments 100-200 km long, have been considered characteristic of Hokkaido's plate-boundary earthquakes. But here we use deposits of prehistoric tsunamis to infer the infrequent occurrence of larger earthquakes generated from longer ruptures. Many of these tsunami deposits form sheets of sand that extend kilometres inland from the deposits of historical tsunamis. Stratigraphic series of extensive sand sheets, intercalated with dated volcanic-ash layers, show that such unusually large tsunamis occurred about every 500 years on average over the past 2,000-7,000 years, most recently ???350 years ago. Numerical simulations of these tsunamis are best explained by earthquakes that individually rupture multiple segments along the southern Kuril trench. We infer that such multi-segment earthquakes persistently recur among a larger number of single-segment events.
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2014-01-01
We investigated the seismicity patterns associated with an M = 4.8 earthquake recorded in the Aeolian Archipelago on 16, August, 2010, by means of the region-time-length (RTL) algorithm. This earthquake triggered landslides at Lipari; a rock fall on the flanks of the Vulcano, Lipari, and Salina islands, and some damages to the village of Lipari. The RTL algorithm is widely used for investigating precursory seismicity changes before large and moderate earthquakes. We examined both the spatial and temporal characteristics of seismicity changes in the Aeolian Archipelago region before the M = 4.8 earthquake. The results obtained reveal 6-7 months of seismic quiescence which started about 15 months before the earthquake. The spatial distribution shows an extensive area characterized by seismic quiescence that suggests a relationship between quiescence and the Aeolian Archipelago regional tectonics. PMID:24511288
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Space geodetic observations of repeating slow slip events beneath the Bonin Islands
NASA Astrophysics Data System (ADS)
Arisa, Deasy; Heki, Kosuke
2017-09-01
The Pacific Plate subducts beneath the Philippine Sea Plate along the Izu-Bonin Trench. We investigated crustal movements at the Bonin Islands, using Global Navigation Satellite System and geodetic Very Long Baseline Interferometry data to reveal how the two plates converge in this subduction zone. These islands are located ∼100 km from the trench, just at the middle between the volcanic arc and the trench, making these islands suitable for detecting signatures of episodic deformation such as slow slip events (SSEs). During 2007-2016, we found five SSEs repeating quasi-periodically with similar displacement patterns. In estimating their fault parameters, we assumed that the fault lies on the prescribed plate boundary, and optimized the size, shape and position of the fault and dislocation vectors. Average fault slip was ∼5 cm, and the average moment magnitude was ∼6.9. We also found one SSE occurred in 2008 updip of the repeating SSE in response to an M6 class interplate earthquake. In spite of the frequent occurrence of SSEs, there is no evidence for long-term strain accumulation in the Bonin Islands that may lead to future megathrust earthquakes. Plate convergence in Mariana-type subduction zones may occur, to a large extent, episodically as repeating SSEs.
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NASA Astrophysics Data System (ADS)
Merz, D. K.; Caplan-Auerbach, J.; Thurber, C. H.
2013-12-01
The Island of Hawai';i is home to the most active volcanoes in the Hawaiian Islands. The island's isolated nature, combined with the lack of permanent offshore seismometers, creates difficulties in recording small magnitude earthquakes with accuracy. This background offshore seismicity is crucial in understanding the structure of the lithosphere around the island chain, the stresses on the lithosphere generated by the weight of the islands, and how the volcanoes interact with each other offshore. This study uses the data collected from a 9-month deployment of a temporary ocean bottom seismometer (OBS) network fully surrounding Lo';ihi volcano. This allowed us to widen the aperture of earthquake detection around the Big Island, lower the magnitude detection threshold, and better constrain the hypocentral depths of offshore seismicity that occurs between the OBS network and the Hawaii Volcano Observatory's land based network. Although this study occurred during a time of volcanic quiescence for Lo';ihi, it establishes a basis for background seismicity of the volcano. More than 480 earthquakes were located using the OBS network, incorporating data from the HVO network where possible. Here we present relocated hypocenters using the double-difference earthquake location algorithm HypoDD (Waldhauser & Ellsworth, 2000), as well as tomographic images for a 30 km square area around the summit of Lo';ihi. Illuminated by using the double-difference earthquake location algorithm HypoDD (Waldhauser & Ellsworth, 2000), offshore seismicity during this study is punctuated by events locating in the mantle fault zone 30-50km deep. These events reflect rupture on preexisting faults in the lower lithosphere caused by stresses induced by volcano loading and flexure of the Pacific Plate (Wolfe et al., 2004; Pritchard et al., 2007). Tomography was performed using the double-difference seismic tomography method TomoDD (Zhang & Thurber, 2003) and showed overall velocities to be slower than
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Updating the USGS seismic hazard maps for Alaska
Mueller, Charles; Briggs, Richard; Wesson, Robert L.; Petersen, Mark D.
2015-01-01
The U.S. Geological Survey makes probabilistic seismic hazard maps and engineering design maps for building codes, emergency planning, risk management, and many other applications. The methodology considers all known earthquake sources with their associated magnitude and rate distributions. Specific faults can be modeled if slip-rate or recurrence information is available. Otherwise, areal sources are developed from earthquake catalogs or GPS data. Sources are combined with ground-motion estimates to compute the hazard. The current maps for Alaska were developed in 2007, and included modeled sources for the Alaska-Aleutian megathrust, a few crustal faults, and areal seismicity sources. The megathrust was modeled as a segmented dipping plane with segmentation largely derived from the slip patches of past earthquakes. Some megathrust deformation is aseismic, so recurrence was estimated from seismic history rather than plate rates. Crustal faults included the Fairweather-Queen Charlotte system, the Denali–Totschunda system, the Castle Mountain fault, two faults on Kodiak Island, and the Transition fault, with recurrence estimated from geologic data. Areal seismicity sources were developed for Benioff-zone earthquakes and for crustal earthquakes not associated with modeled faults. We review the current state of knowledge in Alaska from a seismic-hazard perspective, in anticipation of future updates of the maps. Updated source models will consider revised seismicity catalogs, new information on crustal faults, new GPS data, and new thinking on megathrust recurrence, segmentation, and geometry. Revised ground-motion models will provide up-to-date shaking estimates for crustal earthquakes and subduction earthquakes in Alaska.
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Recent damaging earthquakes in Japan, 2003-2008
Kayen, Robert E
2008-01-01
During the last six years, from 2003-2008, Japan has been struck by three significant and damaging earthquakes: The most recent M6.6 Niigata Chuetsu Oki earthquake of July 16, 2007 off the coast of Kashiwazaki City, Japan; The M6.6 Niigata Chuetsu earthquake of October 23, 2004, located in Niigata Prefecture in the central Uonuma Hills; and the M8.0 Tokachi Oki Earthquake of September 26, 2003 effecting southeastern Hokkaido Prefecture. These earthquakes stand out among many in a very active period of seismicity in Japan. Within the upper 100 km of the crust during this period, Japan experienced 472 earthquakes of magnitude 6, or greater. Both Niigata events affected the south-central region of Tohoku Japan, and the Tokachi-Oki earthquake affected a broad region of the continental shelf and slope southeast of the Island of Hokkaido. This report is synthesized from the work of scores of Japanese and US researchers who led and participated in post-earthquake reconnaissance of these earthquakes: their noteworthy and valuable contributions are listed in an extended acknowledgements section at the end of the paper. During the Niigata Chuetsu Oki event of 2007, damage to the Kashiwazaki-Kariwa nuclear power plant, structures, infrastructure, and ground were primarily the product of two factors: (1) high intensity motions from this moderate-sized shallow event, and (2) soft, poor performing, or liquefiable soils in the coastal region of southwestern Niigata Prefecture. Structural and geotechnical damage along the slopes of dunes was ubiquitous in the Kashiwazaki-Kariwa region. The 2004 Niigata Chuetsu Earthquake was the most significant to affect Japan since the 1995 Kobe earthquake. Forty people were killed, almost 3,000 were injured, and many hundreds of landslides destroyed entire upland villages. Landslides were of all types; some dammed streams, temporarily creating lakes threatening to overtop their new embankments and cause flash floods and mudslides. The numerous
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Feasibility study of earthquake early warning (EEW) in Hawaii
Thelen, Weston A.; Hotovec-Ellis, Alicia J.; Bodin, Paul
2016-09-30
when using a regional network of seismometers. Given the current network, a single-station approach provides more warning for damaging earthquakes that occur close to the station, but it would have limited benefit compared to a fully implemented ShakeAlert system. For Honolulu, for example, the single-station approach provides an advantage over ShakeAlert only for earthquakes that occur in a narrow zone extending northeast and southwest of O‘ahu. Instrumentation and alarms associated with the single-station approach are typically maintained and assessed within the target facility, and thus no outside connectivity is required. A single-station approach, then, is unlikely to help broader populations beyond the individuals at the target facility, but they have the benefit of being commercially available for relatively little cost. The USGS Hawaiian Volcano Observatory (HVO) is the Advanced National Seismic System (ANSS) regional seismic network responsible for locating and characterizing earthquakes across the State of Hawaii. During 2014 and 2015, HVO tested a network-based EEW algorithm within the current seismic network in order to assess the suitability for building a full EEW system. Using the current seismic instrumentation and processing setup at HVO, it is possible for a network approach to release an alarm a little more than 3 seconds after the earthquake is recorded on the fourth seismometer. Presently, earthquakes having M≥3 detected with the ElarmS algorithm have an average location error of approximately 4.5 km and an average magnitude error of -0.3 compared to the reviewed catalog locations from the HVO. Additional stations and upgrades to existing seismic stations would serve to improve solution precision and warning times and additional staffing would be required to provide support for a robust, network-based EEW system. For a critical facility on the Island of Hawaiʻi, such as the telescopes atop Mauna Kea, one phased approach to mitigate losses
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Seismicity of the Earth 1900-2013 offshore British Columbia-southeastern Alaska and vicinity
Hayes, Gavin P.; Smoczyk, Gregory M.; Ooms, Jonathan G.; McNamara, Daniel E.; Furlong, Kevin P.; Benz, Harley M.; Villaseñor, Antonio
2014-01-01
The tectonics of the Pacific margin of North America between Vancouver Island and south-central Alaska are dominated by the northwest motion of the Pacific plate with respect to the North America plate at a velocity of approximately 50 mm/yr. In the south of this mapped region, convergence between the northern extent of the Juan de Fuca plate (also known as the Explorer microplate) and North America plate dominate. North from the Explorer, Pacific, and North America plate triple junction, Pacific:North America motion is accommodated along the ~650-km-long Queen Charlotte fault system. Offshore of Haida Gwaii and to the southwest, the obliquity of the Pacific:North America plate motion vector creates a transpressional regime, and a complex mixture of strike-slip and convergent (underthrusting) tectonics. North of the Haida Gwaii islands, plate motion is roughly parallel to the plate boundary, resulting in almost pure dextral strike-slip motion along the Queen Charlotte fault. To the north, the Queen Charlotte fault splits into multiple structures, continuing offshore of southwestern Alaska as the Fairweather fault, and branching east into the Chatham Strait and Denali faults through the interior of Alaska. The plate boundary north and west of the Fairweather fault ultimately continues as the Alaska-Aleutians subduction zone, where Pacific plate lithosphere subducts beneath the North America plate at the Aleutians Trench. The transition is complex, and involves intraplate structures such as the Transition fault. The Pacific margin offshore British Columbia is one of the most active seismic zones in North America and has hosted a number of large earthquakes historically.
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NASA Astrophysics Data System (ADS)
Kázmér, Miklós; Major, Balázs; 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
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USGS research on geohazards of the North Pacific: past, present, and future
NASA Astrophysics Data System (ADS)
McNutt, M. K.; Eichelberger, J. C.
2012-12-01
The disastrous earthquakes and tsunamis of Sumatra in 2004 and Tohoku in 2011 have driven re-examination of where and how such events occur. Particular focus is on the North Pacific. Of the top 30 earthquakes recorded instrumentally worldwide, 50% occurred along the line of subduction from the Kuril Islands to the southern Alaska mainland. This region has seen monstrous volcanic eruptions (Katmai-Novarupta, 1912), destructive tsunamis (Severo-Kurilsk, 1952), and one of Earth's largest instrumentally-recorded earthquakes (M9.2 Alaska, 1964). Only the modest populations in these frontier towns half a century ago kept losses to a minimum. Impact of any natural disaster to population, vital infrastructure, and sea and air transportation would be magnified today. While USGS had a presence in Alaska for more than a century, the great Alaska earthquake of 1964 ushered in the first understanding of the area's risks. This was the first mega-thrust earthquake properly interpreted as such, and led to re-examination of the 1960 Chilean event. All modern conceptions of mega-thrust earthquakes and tsunamis derive some heritage from USGS research following the 1964 event. The discovery of oil in the Alaska Arctic prompted building a pipeline from the north slope of Alaska to the ice-free port of Valdez. The USGS identified risks from crossing permafrost and active faults. Accurate characterization of these hazards informed innovative designs that kept the pipeline from rupturing due to ground instability or during the M7.9 Denali earthquake of 2002. As a large state with few roads, air travel is common in Alaska. The frequent ash eruptions of volcanoes in the populous Cook Inlet basin became a serious issue, highlighted by the near-crash of a large passenger jet in 1989. In response, the USGS and its partners developed and deployed efficient seismic networks on remote volcanoes and initiated regular satellite surveillance for early warning of ash eruptions. Close collaboration
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High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand
NASA Astrophysics Data System (ADS)
Gouramanis, Chris; Switzer, Adam D.; Jankaew, Kruawun; Bristow, Charles S.; Pham, Dat T.; Ildefonso, Sorvigenaleon R.
2017-03-01
The 26th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified and compared to the known tsunami sandsheets. The proximity of the newly-recognised sandsheets to the palaeo-coastline of Phra Thong Island does not preclude the impacts of localised storms in sandsheet emplacement or that tsunamigenic earthquake recurrence may have been more frequent in the past.
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High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand
Gouramanis, Chris; Switzer, Adam D.; Jankaew, Kruawun; Bristow, Charles S.; Pham, Dat T.; Ildefonso, Sorvigenaleon R.
2017-01-01
The 26th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified and compared to the known tsunami sandsheets. The proximity of the newly-recognised sandsheets to the palaeo-coastline of Phra Thong Island does not preclude the impacts of localised storms in sandsheet emplacement or that tsunamigenic earthquake recurrence may have been more frequent in the past. PMID:28276445
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High-frequency Coastal Overwash Deposits from Phra Thong Island, Thailand.
Gouramanis, Chris; Switzer, Adam D; Jankaew, Kruawun; Bristow, Charles S; Pham, Dat T; Ildefonso, Sorvigenaleon R
2017-03-09
The 26 th December 2004 Indian Ocean Tsunami (IOT) emanated from an Mw 9.2 earthquake that generated a 1600 km-long rupture along the Sumatran Megathrust and generated tsunami waves up to 30 m high. The IOT directly impacted the Bay of Bengal and east Africa, with over 283,000 people perishing. At the time, this catastrophic event was considered unprecedented and sparked intense investigations to test this claim. It is now believed that four pre-2004 IOT events have occurred in the last 2500 years, recurring every 550 to 700 years. Much of this information comes from Phra Thong Island, Thailand, where a sequence of four stacked sandsheets separated by organic units has been recognised and compared to the 2004 IOT event. Recently, ground-penetrating radar on Phra Thong Island identified a region that could not be explained by the known stratigraphy. The stratigraphy of the area was investigated from auger cores and pits, and several previously-unrecognised sandsheets were identified and compared to the known tsunami sandsheets. The proximity of the newly-recognised sandsheets to the palaeo-coastline of Phra Thong Island does not preclude the impacts of localised storms in sandsheet emplacement or that tsunamigenic earthquake recurrence may have been more frequent in the past.
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The 2007 Mentawai earthquake sequence on the Sumatra megathrust
NASA Astrophysics Data System (ADS)
Konca, A.; Avouac, J.; Sladen, A.; Meltzner, A. J.; Kositsky, A. P.; Sieh, K.; Fang, P.; Li, Z.; Galetzka, J.; Genrich, J.; Chlieh, M.; Natawidjaja, D. H.; Bock, Y.; Fielding, E. J.; Helmberger, D. V.
2008-12-01
The Sumatra Megathrust has recently produced a flurry of large interplate earthquakes starting with the giant Mw 9.15, Aceh earthquake of 2004. All of these earthquakes occurred within the area monitored by the Sumatra Geodetic Array (SuGAr), which provided exceptional records of near-field co-seismic and postseismic ground displacements. The most recent of these major earthquakes, an Mw 8.4 earthquake and an Mw 7.9 earthquake twelve hours later, occurred in the Mentawai islands area where devastating historical earthquakes had happened in 1797 and 1833. The 2007 earthquake sequence provides an exceptional opportunity to understand the variability of the earthquakes along megathrusts and their relation to interseismic coupling. The InSAR, GPS and teleseismic modeling shows that 2007 earthquakes ruptured a fraction of the strongly coupled Mentawai patch of the megathrust, which is also only a fraction of the 1833 rupture area. It also released a much smaller moment than the one released in 1833, or than the deficit of moment that has accumulated since. Both earthquakes of 2007 consist of 2 sub-events which are 50 to 100 km apart from each other. On the other hand, the northernmost slip patch of 8.4 and southern slip patch of 7.9 earthquakes abut each other, but they ruptured 12 hours apart. Sunda megathrust earthquakes of recent years include a rupture of a strongly coupled patch that closely mimics a prior rupture of that patch and which is well correlated with the interseismic coupling pattern (Nias-Simeulue section), as well as a rupture sequence of a strongly coupled patch that differs substantially in the details from its most recent predecessors (Mentawai section). We conclude that (1) seismic asperities are probably persistent features which arise form heterogeneous strain build up in the interseismic period; and (2) the same portion of a megathrust can rupture in different ways depending on whether asperities break as isolated events or cooperate to produce
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Lessons from the Tōhoku tsunami: A model for island avifauna conservation prioritization.
Reynolds, Michelle H; Berkowitz, Paul; Klavitter, John L; Courtot, Karen N
2017-08-01
Earthquake-generated tsunamis threaten coastal areas and low-lying islands with sudden flooding. Although human hazards and infrastructure damage have been well documented for tsunamis in recent decades, the effects on wildlife communities rarely have been quantified. We describe a tsunami that hit the world's largest remaining tropical seabird rookery and estimate the effects of sudden flooding on 23 bird species nesting on Pacific islands more than 3,800 km from the epicenter. We used global positioning systems, tide gauge data, and satellite imagery to quantify characteristics of the Tōhoku earthquake-generated tsunami (11 March 2011) and its inundation extent across four Hawaiian Islands. We estimated short-term effects of sudden flooding to bird communities using spatially explicit data from Midway Atoll and Laysan Island, Hawai'i. We describe variation in species vulnerability based on breeding phenology, nesting habitat, and life history traits. The tsunami inundated 21%-100% of each island's area at Midway Atoll and Laysan Island. Procellariformes (albatrosses and petrels) chick and egg losses exceeded 258,500 at Midway Atoll while albatross chick losses at Laysan Island exceeded 21,400. The tsunami struck at night and during the peak of nesting for 14 colonial seabird species. Strongly philopatric Procellariformes were vulnerable to the tsunami. Nonmigratory, endemic, endangered Laysan Teal ( Anas laysanensis ) were sensitive to ecosystem effects such as habitat changes and carcass-initiated epizootics of avian botulism, and its populations declined approximately 40% on both atolls post-tsunami. Catastrophic flooding of Pacific islands occurs periodically not only from tsunamis, but also from storm surge and rainfall; with sea-level rise, the frequency of sudden flooding events will likely increase. As invasive predators occupy habitat on higher elevation Hawaiian Islands and globally important avian populations are concentrated on low-lying islands
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Lessons from the Tōhoku tsunami: A model for island avifauna conservation prioritization
Reynolds, Michelle H.; Berkowitz, Paul; Klavitter, John; Courtot, Karen
2017-01-01
Earthquake-generated tsunamis threaten coastal areas and low-lying islands with sudden flooding. Although human hazards and infrastructure damage have been well documented for tsunamis in recent decades, the effects on wildlife communities rarely have been quantified. We describe a tsunami that hit the world's largest remaining tropical seabird rookery and estimate the effects of sudden flooding on 23 bird species nesting on Pacific islands more than 3,800 km from the epicenter. We used global positioning systems, tide gauge data, and satellite imagery to quantify characteristics of the Tōhoku earthquake-generated tsunami (11 March 2011) and its inundation extent across four Hawaiian Islands. We estimated short-term effects of sudden flooding to bird communities using spatially explicit data from Midway Atoll and Laysan Island, Hawai'i. We describe variation in species vulnerability based on breeding phenology, nesting habitat, and life history traits. The tsunami inundated 21%–100% of each island's area at Midway Atoll and Laysan Island. Procellariformes (albatrosses and petrels) chick and egg losses exceeded 258,500 at Midway Atoll while albatross chick losses at Laysan Island exceeded 21,400. The tsunami struck at night and during the peak of nesting for 14 colonial seabird species. Strongly philopatric Procellariformes were vulnerable to the tsunami. Nonmigratory, endemic, endangered Laysan Teal (Anas laysanensis) were sensitive to ecosystem effects such as habitat changes and carcass-initiated epizootics of avian botulism, and its populations declined approximately 40% on both atolls post-tsunami. Catastrophic flooding of Pacific islands occurs periodically not only from tsunamis, but also from storm surge and rainfall; with sea-level rise, the frequency of sudden flooding events will likely increase. As invasive predators occupy habitat on higher elevation Hawaiian Islands and globally important avian populations are concentrated on low-lying islands
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The HayWired Earthquake Scenario—Earthquake Hazards
Detweiler, Shane T.; Wein, Anne M.
2017-04-24
The HayWired scenario is a hypothetical earthquake sequence that is being used to better understand hazards for the San Francisco Bay region during and after an earthquake of magnitude 7 on the Hayward Fault. The 2014 Working Group on California Earthquake Probabilities calculated that there is a 33-percent likelihood of a large (magnitude 6.7 or greater) earthquake occurring on the Hayward Fault within three decades. A large Hayward Fault earthquake will produce strong ground shaking, permanent displacement of the Earth’s surface, landslides, liquefaction (soils becoming liquid-like during shaking), and subsequent fault slip, known as afterslip, and earthquakes, known as aftershocks. The most recent large earthquake on the Hayward Fault occurred on October 21, 1868, and it ruptured the southern part of the fault. The 1868 magnitude-6.8 earthquake occurred when the San Francisco Bay region had far fewer people, buildings, and infrastructure (roads, communication lines, and utilities) than it does today, yet the strong ground shaking from the earthquake still caused significant building damage and loss of life. The next large Hayward Fault earthquake is anticipated to affect thousands of structures and disrupt the lives of millions of people. Earthquake risk in the San Francisco Bay region has been greatly reduced as a result of previous concerted efforts; for example, tens of billions of dollars of investment in strengthening infrastructure was motivated in large part by the 1989 magnitude 6.9 Loma Prieta earthquake. To build on efforts to reduce earthquake risk in the San Francisco Bay region, the HayWired earthquake scenario comprehensively examines the earthquake hazards to help provide the crucial scientific information that the San Francisco Bay region can use to prepare for the next large earthquake, The HayWired Earthquake Scenario—Earthquake Hazards volume describes the strong ground shaking modeled in the scenario and the hazardous movements of
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The 2016 Mw7.0 Kumamoto, Japan earthquake: the rupture propagation under extensional stress
NASA Astrophysics Data System (ADS)
Zhang, Y.; Shan, X.; Zhang, G.; Gong, W.
2016-12-01
On April 16, 2016, the Kumamoto city was hit by an Mw7.0 earthquake, the largest earthquake since 1900 in the central part of Kyushu Island in Japan. It is an event with two foreshocks and rather complex source faults and surface rupture scarps. The Mw7.0 Kumamoto earthquake and its foreshocks and aftershocks occurred on the Futagawa and Hinagu faults, which are previously mapped and formed the southwest portion of the median tectonic line on Kyushu Island. These faults are mainly controlled by extensional and right-lateral shear stress. In this study, we obtained the deformation filed of the Kumamoto earthquake using both of descending and ascending Sentinel-1A data. We then invert the fault slip distribution based on the displacements obtained by InSAR. A three-segment fault model is established by trial and error. We analyze the rupture propagation and the conclusions are listed as following: The Mw 7.0 earthquake is a right-lateral striking event with a slight normal component. Most of the slip distributed on the Futagawa fault segment, with a maximum slip of 4.9 m at 5 km depth below the surface. The energy released on this Futagawa fault segment is equivalent to an Mw6.9 event. The slip distribution on the Hinagu fault segment is also right-lateral, but with a maximum slip of 2 m. Compared to the southern two segments, the northern source fault segment has the steepest dipping segment, which is almost vertical, with a dip as high as 80°; The normal component of the Kumamoto event is controlled by extensional stress due to the tectonic background. The Beppu-Shimabara half graben is the largest extensional structure on Kyushu Island and its formation could strongly be affected by Philippine Sea slab (PHS) convergence and Okinawa Trough extension, so we argue the Kumamoto event maybe exhibits the concrete manifestation of Okinawa Trough extension to Kyushu Island; Continuous surface rupture trace is observed from InSAR coseismic deformation and field
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ERIC Educational Resources Information Center
National Oceanic and Atmospheric Administration (DOC), Rockville, MD.
This activity is designed to introduce to students the processes of plate tectonics and volcanism that resulted in the formation of the Hawaiian Islands and the difference between S waves and P waves. Students are expected to explain how seismic data recorded at different locations can be used to determine the epicenter of an earthquake, infer a…
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Plate-boundary deformation associated with the great Sumatra-Andaman earthquake.
Subarya, Cecep; Chlieh, Mohamed; Prawirodirdjo, Linette; Avouac, Jean-Philippe; Bock, Yehuda; Sieh, Kerry; Meltzner, Aron J; Natawidjaja, Danny H; McCaffrey, Robert
2006-03-02
The Sumatra-Andaman earthquake of 26 December 2004 is the first giant earthquake (moment magnitude M(w) > 9.0) to have occurred since the advent of modern space-based geodesy and broadband seismology. It therefore provides an unprecedented opportunity to investigate the characteristics of one of these enormous and rare events. Here we report estimates of the ground displacement associated with this event, using near-field Global Positioning System (GPS) surveys in northwestern Sumatra combined with in situ and remote observations of the vertical motion of coral reefs. These data show that the earthquake was generated by rupture of the Sunda subduction megathrust over a distance of >1,500 kilometres and a width of <150 kilometres. Megathrust slip exceeded 20 metres offshore northern Sumatra, mostly at depths shallower than 30 kilometres. Comparison of the geodetically and seismically inferred slip distribution indicates that approximately 30 per cent additional fault slip accrued in the 1.5 months following the 500-second-long seismic rupture. Both seismic and aseismic slip before our re-occupation of GPS sites occurred on the shallow portion of the megathrust, where the large Aceh tsunami originated. Slip tapers off abruptly along strike beneath Simeulue Island at the southeastern edge of the rupture, where the earthquake nucleated and where an M(w) = 7.2 earthquake occurred in late 2002. This edge also abuts the northern limit of slip in the 28 March 2005 M(w) = 8.7 Nias-Simeulue earthquake.
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Tao-Rusyr Caldera, Onekotan Island, Kuril Islands
2017-12-08
More than 9,000 years ago, a catastrophic volcanic eruption created a huge caldera on the southern end of Onekotan Island, one of the Kuril Islands, located off the southern tip of Russia’s Kamchatka Peninsula. Today, the ancient Tao-Rusyr Caldera is filled by the deep blue waters of Kal’tsevoe Lake. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite acquired this true-color image of southern Onekotan on June 10, 2009. In this late-spring shot, snow or ice lingers on the land, forming white streaks on a brown-and-green land surface. In the northwest quadrant of the caldera is Krenitzyn Peak, which rises to a height of 1,325 meters (4,347 feet). Like the other Kuril Islands, Onekotan lies along the Pacific “Ring of Fire.” The Kuril Island volcanoes are fueled by magma generated by the subduction of the Pacific Plate under the Eurasian Plate, which takes place along a deep trench about 200 kilometers (120 miles) to the islands’ east. The only historical eruption at Krenitzyn Peak occurred in 1952, a week after a magnitude 9.0 earthquake along the subduction fault. NASA Earth Observatory image created by Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Michon Scott and Rebecca Lindsey. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
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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