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1.
Ashok S. Patwardhan I. M. Idriss John M. Hobgood Ram B. Kulkarni K. Sadigh 《Marine Georesources & Geotechnology》2013,31(3):243-267
Abstract The characterization of earthquake sources in the Gulf of Alaska and the relative significance of earthquake sources for establishing seismic design inputs at a typical site for engineering purposes are discussed. Earthquake sources in the complex tectonic environment can be divided into two groups: (a) a subduction zone that underlies the entire region (maximum magnitude M = 8.5); and (b) individual thrust and strike‐slip faults associated with the plate motions (maximum magnitude M = 6 to 7.5). The sources of either group and individual earthquake events can be represented as planar surfaces for consistency with the physical process and a mathematically tractable computational scheme. Although the area is very active seismically, the degree of activity of individual sources varies significantly. Therefore, even for sources with the same maximum earthquakes, different magnitudes may apply for a selected design return period. The area is considered to be a “seismic gap.”; No great earthquakes have occurred in nearly 80 years. Estimates based on a temporally varying seismic function such as the semi‐Markov model indicate that the probability of occurrence of a great earthquake in the near future is significantly higher than the average probability inferred from a statistical analysis of historical seismicity data of the entire region. Separate attenuation relationships should be used for calculating ground motions due to earthquakes on the dipping subduction zone in the northern portion of the gulf. The dominant earthquake source for almost the entire Gulf of Alaska region is the subduction zone that contributes over 80 percent of the seismic exposure at a typical site. The dominant magnitude range is Ms = 6.5 to 7.5. “Gap filling”; earthquakes (Ms = 7.5 to 8.25) contribute a little over a third of the seismic exposure at a typical site. Deterministic assessments of ground motion values using the maximum earthquake on the subduction zone at the closest distance yield values significantly higher than those calculated for even 500‐year return periods. Estimated 100‐year return period accelerations in the area range from 180 to 340 cm/sec2. 相似文献
2.
In this paper we analyze seismic regime and earthquake depth distribution and correlation of seismicity and mud volcanism in the Azerbaijan and the Caspian Sea region. For the present region we have calculated accurate source locations, seismic activity, earthquake repetition and released earthquake energy parameters. It is shown that the active tectonic processes in the region are concentrated within the thick sedimentary cover that we consider as a general source of contemporary stress and a main structural element responsible for the origin of regional earthquakes. The correlation of seismicity and mud volcanism is of paragenetic character. 相似文献
3.
At present, the problem of predicting tsunamis with source earthquakes near the shoreline remains practically unresolved. It is shown that, in the Pacific region, 87% of tsunamigenous earthquake epicenters are located closer than 100 km to the shoreline and 67% are closer than 50 km. For a more detailed analysis, the area of the Pacific Ocean was divided into ten subregions: Kamchatka, the Kuril Islands, Japan, Indonesia, Australia and Oceania, South and Central America, Alaska, and the Aleutian Islands. Each subregion was analyzed individually. All the earthquakes from 1950 to 2003 with Ms >= 6.0 causing tsunamis with intensities I > 0 were processed. The ITDB/PAC 2004 database was used as the data source. For each subregion, mean and minimal travel times were calculated. The minimal travel times for all the regions except for a single one are less than 10 min. It is shown that, in the near earthquake zone, no tsunami alert based sea-level gauge data is possible. One probable solution could be based on detecting hydroacoustic signals that precede strong earthquakes in the near-shore zone. 相似文献
4.
The features of the seismic regime before the strongest earthquakes of Taiwan in the late 20th (Chi-Chi on September 21, 1999, Mw = 7.6) and the early 21st century (March 31, 2002, Mw = 7.4) are analyzed. Based on 1990–1999 and 1994–2002 data, respectively, retrospective analysis of three seismic regime parameters are studied: the total annual number of earthquakes NΣ in the range of ML = 2.5–5.5 and Mw = 3.0–7.0; the total annual quantity of released seismic energy ΣE, J; and angular coefficient b of earthquake recurrence graphs. Two explicit subperiods are revealed in the course of the seismic regime: quiescence in 1990–1996 before the Chi-Chi earthquake and in 1994–1997 before the March 2002 earthquake; in 1997–1999 and 1998–2002, respectively, seismic activation is observed. Due to the predominance of weak earthquakes during the Chi-Chi earthquake preparation, factor b appeared relatively higher (–1.16 on average); in contrast, before the March 2002 earthquake, due to the occurrence of foreshocks with Mw = 6.8–7.0, the factor b values appeared relatively lower (–0.55 and–0.74 for the quiescence and activation subperiods, respectively). Despite the fundamental difference in the seismotectonic situation between the domains where two mainshocks occurred and significantly difference energy ranges of the initial seismic events, the analysis results are similar for both earthquakes. In both cases, the mainshock occurred at the peak of released energy, which can be considered a coincidence. Solid verification of this positive tendency requires the accumulation of seismological statistics. 相似文献
5.
Seismicity characteristics in the areas of Sarez Lake and the Nurek water reservoir are studied. Ring-shaped seismicity structures in two depth ranges (0–33 and 34–70 km) formed prior to the Pamir earthquake of December 7, 2015 (M w = 7.2). Seismicity rings cross each other near the Usoi Dam, which formed after the strong earthquake in 1911 and led to the formation of Sarez Lake, and near the epicenter of the Pamir earthquake. In addition, three out of the four strongest events (М ≥ 6.0) recorded in the Pamir region at depths of more than 70 km since 1950 have occurred near Sarez Lake. An aggregate of the data allows us to conclude that the Pamir earthquake, despite its very large energy, refers to events related to induced seismicity. Ring-shaped seismicity structures in two depth ranges also formed in the Nurek water reservoir area. It is supposed that the formation of ring-shaped structures is related to the self-organization processes of a geological system, which result in the ascent of deep-seated fluids. In this respect, the lithosphere is gradually adapting to the additional load related to the filling of the water reservoir. The difference between Nurek Dam (and many other hydroelectric power stations as well) and Usoi Dam is the permanent vibration in the former case due to water falling from a height of more than 200 m. Such an effect can lead to gradual stress dissipation, resulting in the occurrence of much weaker events when compared to the Pamir earthquake of December 7, 2015, in the areas of artificial water reservoirs. 相似文献
6.
A 2D variant of the inversion method for determining velocities within the Benioff zone of Kamchatka is developed with respect to the time of seismic wave travel from the foci group to Shipunskii station located in the region where the zone outcrops at the ocean bottom. The method is based on the idea of seismic tomography on the relationship between travel time discrepancies along the focus–station path and the value of seismic slowness, which is inverse to the velocity and corresponds to the gradient of the time field or the derivative of a hodograph with respect to the distance dt/dl. From this viewpoint, the field of discrepancies observed is the difference between the experimental and theoretical values of slowness. Its averaging with respect to depth and epicentral distance in 50 × 50 km rectangular windows and subsequent inversion make it possible to obtain a discrete velocity field using the GoldenSoftware Surfer program. Resmoothing with the same software leads to a variant of continuous velocity distribution = in the axial plane of the Benioff zone. The described procedure was used to calculate the velocities in this zone of the southern Kuril Islands and southern and central Kamchatka. The principal result in the latter case is identification of a sharp jump in the velocities of body waves in the upper mantle (up to 1.3 km/s for P-waves and up to 0.8 km/s for S-waves) beneath the Kronotskii Peninsula in the 7 years before the catastrophic Kronotskii earthquake that occurred in 1997 (M = 7.9) with an upthrow focal mechanism. This jump reflects the concentration of stresses in the epicentral zone of the earthquake. This result is important for medium-term forecasting of strong earthquakes. 相似文献
7.
The great Japanese earthquake (GJE) of March 11, 2011, was a megaevent. The conditions under which such seismic catastrophes
occurred are discussed. The regime of the aftershocks of this megaevent is compared with the data on the aftershock sequences
which accompanied the Simushir earthquakes (2006 and 2007) and the Andaman earthquake (2004) and with the seismicity behavior
in the generalized vicinity of a strong earthquake. The aftershock sequences of the abovementioned strong earthquakes are
shown to represent the sets of trend changes in the postshock activity and specific outbursts of seismic activity. Activity
outbursts are characterized not only by an increase in the number and energy of events, but also by a decrease in the recurrence
plot slope (b value) and the average earthquake depth. Some such outbursts correspond to the occurrence of strong repeated shocks. A possible
mechanism for outbursts of seismic activity is proposed. The possibility of a stronger repeated shock in the vicinity of the
megaearthquake of March 11, 2011, is discussed. 相似文献
8.
Philippine archipelago(PA) has strong background seismicity, but there is no systematic study of earthquake triggering in this region. There are six earthquakes(M_w 6) occurred between 2018/12/29 and 2019/09/29 in PA,which provides an excellent opportunity to investigate the triggering relationship among these events. We calculate the static Coulomb stress changes of the first five events, and find that the local seismicity after the2018/12/29 M_w 7.0 earthquake is mostly associated with positive Coulomb stress changes, including the2019/05/31 M_w 6.1 event, suggesting a possible triggering relationship. However, we cannot rule out the dynamic triggering mechanism, due to increased microseismicity in both positive and negative stress change regions, and an incomplete local catalog, especially right after the first M_w 7.0 mainshock. The dynamic stresses from these M_w 6 events are large enough(from 5 kPa to 3 532 kPa) to trigger subsequent events, but a lack of seismicity and waveform evidence does not support delayed dynamic triggering among these events, even the shortest time interval is less than 24 hours. In the past 45 years, the released seismic energy shows certain peaks every 5–10 years. However, earthquakes with M_w 6.0 were relatively infrequent between 2004 and 2018 at PA. Hence, it is possible that several regions are relatively late in their earthquake cycles, which would enhance their susceptibility of being triggered by earthquakes at nearby and regional distances. 相似文献
9.
本文根据１９９４年９月１６日台湾海峡７．３级强震序列的空间活动图象变化特征，结合历史地震资料，比较分析了台湾海峡区域史今地震活动的总体演变过程，表明该区强震发生与周边地区的台湾，日本及菲律宾大地地震，在时间进程，强度变化和地域分布关系上存在关地球物理场变化的影响。 相似文献
10.
L. I. Lobkovsky A. B. Rabinovich E. A. Kulikov A. I. Ivashchenko I. V. Fine R. E. Thomson T. N. Ivelskaya G. S. Bogdanov 《Oceanology》2009,49(2):166-181
Major earthquakes occurred in the region of the Central Kuril Islands on November 15, 2006 (M w = 8.3) and January 13, 2007 (M w = 8.1). These earthquakes generated strong tsunamis recorded throughout the entire Pacific Ocean. The first was the strongest trans-Pacific tsunami of the past 42 years (since the Alaska tsunami in 1964). The high probability of a strong earthquake (M w ≥ 8.5) and associated destructive tsunami occurring in this region was predicted earlier. The most probable earthquake source region was investigated and possible scenarios for the tsunami generation were modeled. Investigations of the events that occurred on November 15, 2006, and January 13, 2007, enabled us to estimate the validity of the forecast and compare the parameters of the forecasted and observed earthquakes and tsunamis. In this paper, we discuss the concept of “seismic gaps,” which formed the basis for the forecast of these events, and put forward further assumptions about the expected seismic activity in the region. We investigate the efficiency of the tsunami warning services and estimate the statistical parameters for the observed tsunami waves that struck the Far Eastern coast of Russia and Northern Japan. The propagation and transformation of the 2006 and 2007 tsunamis are studied using numerical hydrodynamic modeling. The spatial characteristics of the two events are compared. 相似文献
11.
Due to the initiation of the Hellenic Unified Seismic Network (HUSN) in late 2007, the quality of observation significantly improved by 2011. For example, the representative magnitude level considerably has decreased and the number of annually recorded events has increased. The new observational system highly expanded the possibilities for studying regularities in seismicity. In view of this, the authors revisited their studies of the diurnal periodicity of representative earthquakes in Greece that was revealed earlier in the earthquake catalog before 2011. We use 18 samples of earthquakes of different magnitudes taken from the catalog of Greek earthquakes from 2011 to June 2016 to derive a series of the number of earthquakes for each of them and calculate its average diurnal course. To increase the reliability of the results, we compared the data for two regions. With a high degree of statistical significance, we have obtained that no diurnal periodicity can be found for strongly representative earthquakes. This finding differs from the estimates obtained earlier from an analysis of the catalog of earthquakes at the same area for 1995–2004 and 2005–2010, i.e., before the initiation of the Hellenic Unified Seismic Network. The new results are consistent with the hypothesis of noise discrimination (observational selection) explaining the cause of the diurnal variation of earthquakes with different sensitivity of the seismic network in daytime and nighttime periods. 相似文献
12.
C. Riedel A. Tryggvason B. Brandsdottír T. Dahm R. Stéfansson M. Hensch R. Böðvarsson K. S. Vogfjord S. Jakobsdottír T. Eken R. Herber J. Holmjarn M. Schnese M. Thölen B. Hofmann B. Sigurdsson S. Winter 《Marine Geophysical Researches》2006,27(4):267-281
Between June 2004 and September 2004 a temporary seismic network was installed on the northern insular shelf of Iceland and onshore in north Iceland. The seismic setup aimed at resolving the subsurface structure and, thus, the geodynamical transition from Icelandic crust to typical oceanic crust along Kolbeinsey Ridge. The experiment recorded about 1,000 earthquakes. The region encloses the Tjörnes Fracture Zone containing the Husavik–Flatey strike-slip fault and the extensional seismic Grimsey Lineament. Most of the seismicity occurs in swarms offshore. Preliminary results reveal typical mid-ocean crust north of Grimsey and a heterogeneous structure with major velocity anomalies along the seismic lineaments and north–south trending subsurface features. Complementary bathymetric mapping highlight numerous extrusion features along the Grimsey Lineament and Kolbeinsey Ridge. The seismic dataset promises to deliver new insights into the tectonic framework for earthquakes in an extensional transform zone along the global mid-ocean ridge system. 相似文献
13.
Nai-Chi Hsiao Tzu-Wei Lin Shu-Kun Hsu Kai-Wei Kuo Tzay-Chyn Shin Peih-Lin Leu 《Marine Geophysical Researches》2014,35(3):327-336
In order to improve the locating capability for offshore earthquakes and tsunamis monitored off northeastern Taiwan, a cable-based ocean bottom seismographic observatory named “Marine Cable Hosted Observatory” (MACHO) was constructed and began operation at the end of 2011. The installed instruments of the observatory include a broadband seismometer, a strong-motion seismometer and a pressure gauge. In addition, various scientific instruments could be deployed for other purposes as well. At present, the seismic data are transmitted in real-time via a fiber cable, and integrated into the current inland seismographic network in Taiwan. The ocean bottom station has contributed to provide high quality seismic data already. According to observations from January 2012 to June 2013, there were a total of 15,168 earthquakes recorded by the system. By using the data from the ocean bottom station, the number of relocated earthquakes with an azimuth gap less than 180 degrees substantially increase about 34 %. Meanwhile, the root–mean–square of the time residual, the error in epicenter, and the error in depth of the earthquake locations decrease. Therefore, the implementation of MACHO has the advantage of extending the coverage of existing the Taiwan seismic network to the offshore, providing more accurate and real-time seismic data for offshore earthquakes monitoring. The results show that MACHO is crucial and necessary for monitoring seismic activities in northeastern Taiwan. 相似文献
14.
The seismicity of the northeastern part of the Indian Ocean in connection with the general structural peculiarities of the
main tectonic structures of the bottom is presented. The three main ranges of higher seismic activity at the depths of 0–17,
20–27, and 32–35 km divided by aseismic layers are revealed. The seismic activity at depths of more than 35 km is almost not
detected both for the ocean and for the Indian peninsula. The nature of the distribution of the seismicity as such in the
lithosphere is discussed. Using the results of anomalous au]gravitational field transformations, the prolongation of the East
Indian Ridge structure is revealed to 19 degrees north, while the relationship of the Afanasy Nikitin Rise and the 85th Degree
Ridge is not reflected at the tranforms. In the Cocos Basin, the mutually perpendicular disturbance zones of northeastern
and northwestern strike, as well as the point of their crossing, where the maximal number of earthquake foci are concentrated,
are distinguished. A conclusion concerning the substantial disturbance of the strength properties of the lithosphere in this
zone as a consequence of the geodynamical processes, which are accompanied by fracture tectonics, is reached. 相似文献
15.
The results of monitoring radon emanations in the territory of Gorno-Altaisk due to seismic activity and their influence on human health are considered. It is shown that the level of activity of subsoil radon in the vicinity of the fault zone in the territory of Gorno-Altaisk exceeds such a level recorded in Moscow by 3–4 times. There is ambiguity in the behavior of radon as a precursor of a seismic event. Some radon anomalies are synchronous with moments of earthquakes and others correspond to quiet periods. The radon activity is more closely associated with the earthquakes localized in the aftershock zone of the Chuya earthquake. This is assumed to be caused by the network of fluid-conducting channels within the active fault between this region and the observation station. 相似文献
16.
渤海海域地震海啸灾害概率性风险评估 总被引：1，自引：0，他引：1
渤海作为我国地震活动性最为活跃的近海，其地震海啸风险不可忽视。本文应用概率性海啸风险评估方法对渤海周边区域的海啸风险进行评估。根据历史地震目录建立了渤海区域的震级-频率关系，基于蒙特卡洛算法随机生成了一套10万年的地震目录，最终通过对地震事件的海啸数值模拟及最大波幅的统计分析给出了环渤海区域典型重现期的最大波幅分布以及重点城市的海啸波幅曲线。评估结果表明，渤海地区海啸风险主要集中在渤海湾和莱州湾周边，波幅可达到1~3 m，辽东湾地区海啸风险较低。 相似文献
17.
Weina Zhao Zhiqiang Wu Fanghui Hou Xunhua Zhang Tianyao Hao Hanjoon Kim Yanpeng Zheng Shanshan Chen Huigang Wang 《海洋学报(英文版)》2023,42(2):104-119
The South Yellow Sea basin is filled with Mesozoic–Cenozoic continental sediments overlying pre-Palaeozoic and Mesozoic–Palaeozoic marine sediments. Conventional multi-channel seismic data cannot describe the velocity structure of the marine residual basin in detail, leading to the lack of a deeper understanding of the distribution and lithology owing to strong energy shielding on the top interface of marine sediments. In this study, we present seismic tomography data from ocean bottom seismogra... 相似文献
18.
A. Ya. Sidorin 《Izvestiya Atmospheric and Oceanic Physics》2013,49(7):760-764
Peculiarities of the intra-annual distribution of strong earthquakes in the Garm region (energetic class K > 9.0) are considered. An increase in such earthquakes in spring has been found during a period of intense transport of thawed water into the soil. The number of weak earthquakes during this period decreases. We discuss the possible reasons for nonuniformity in the intra-annual distribution of seismicity, including those generated by a hydroseismic mechanism. 相似文献
19.
L. B. Slavina N. B. Pivovarova S. L. Senyukov 《Izvestiya Atmospheric and Oceanic Physics》2012,48(7):696-705
The results of a calculation of the P-wave (V P ) velocity fields are presented on the basis of the method of the reversible wave and the TAU parameter characterizing the V P /V S ratio of seismic waves from the local volcanic earthquakes that occurred at the northern group of Kamchatka volcanoes in 2005–2007. The 3D velocity cross sections were constructed along the SW-NE-trending volcanic group from the Ploskii Tolbachik volcano in the southwest up to the Shiveluch volcano in the northeast. The change of velocity field in time and depth is found. The problems of relating these changes to volcanic activity is reviewed. 相似文献
20.
台湾海峡及其西边地区正常地震动态及危险性特征 总被引：1，自引：2，他引：1
本文从地震的时，空分布特征，区域应力场动态，能量释放方式，ｂ值及震群特征６个方面研究了台湾海峡及其西边地区地震活动的正常动态及异常特征。结果表明，具有前兆意义的变化模式表现为区域地震活动在时间，空间及功能方面的有序性变化，即：（ａ）地震空间分布由分散转为集中，形成条带或空区；（ｂ）断裂活动由多组转为单一，应力场趋向一致；（display status 相似文献