马尼拉海沟俯冲带板缘地震特征及衰减关系研究

俯冲带通常位于陆地板块与海洋板块或者海洋板块之间的交界处,地质构造复杂,地震活动频繁.在南海海域,马尼拉海沟俯冲带对中国海洋战略及近海重大工程的实施位置至关重要.在缺少实际地震数据的前提下,为分析马尼拉海沟俯冲带地震动及其衰减关系特征,通过采用随机有限断层法模拟该俯冲带地震动,分析地震动加速度时程及反应谱特点,同时分别...     

Stochastic Finite Fault Modeling of Subduction Zone Earthquakes in Northeastern India

In this article, a stochastic finite fault source model is calibrated to estimate ground motion in northeastern India for intermediate depth events originating in the Indo-Burmese tectonic domain. A total of 47 three-component accelerograms from eight events with magnitudes ranging from M _w 4.8–6.4 are used to estimate the input source and site parameters of the finite fault source model. Key seismic parameters such as stress drop (Δσ) and site amplification function are determined from the recorded strong motion data. The obtained stress drop of the eight recorded events lies in between 105 and 165 bars.     

基于广义帕累托分布的马尼拉海沟俯冲带地震危险性估计

选取马尼拉海沟俯冲带作为潜源区, 基于广义帕累托分布, 通过对一定时段内超过某一阈值的震级数据进行拟合, 建立该潜源区地震危险性估计模型, 估计强震重现水平和震级上限, 并对估计结果的不确定性进行了分析, 得到马尼拉海沟俯冲带震级上限为9.0级, 10 a、 50 a、 100 a、 200 a马尼拉海沟俯冲带的震级重现水平期望值分别为7.1级、 7.6级、 7.7级、 7.9级。     

Comparison of Depth Dependent Fault Zone Properties in the Japan Trench and Middle America Trench

—Spatial variations in mechanical properties of the interplate thrust faults along the Japan and Middle America subduction zones are examined using teleseismic broadband earthquake recordings. Moment-normalized source duration is used to probe rigidity variations along the interface. We invert body waves to estimate source depth and source duration for 40 events in the Japan subduction zone and 38 events in the Middle America subduction zone. For both areas, there is a systematic decrease in source duration with increasing depth along the subduction zone interface. This is most likely a result of variation in properties of sediments on the plate contact. Variations in source duration are greatly reduced at depths greater than 18 km in both regions. Enhanced spatial heterogeneity at shallow depth may reflect variations in plate roughness, sediment distribution, permeability of the fault zone, and stress.     

Simulations of Seismic Hazard for the Pacific Northwest of the United States from Earthquakes Associated with the Cascadia Subduction Zone

-- We investigate the impact of different rupture and attenuation models for the Cascadia subduction zone by simulating seismic hazard models for the Pacific Northwest of the U.S. at 2% probability of exceedance in 50 years. We calculate the sensitivity of hazard (probabilistic ground motions) to the source parameters and the attenuation relations for both intraslab and interface earthquakes and present these in the framework of the standard USGS hazard model that includes crustal earthquakes. Our results indicate that allowing the deep intraslab earthquakes to occur anywhere along the subduction zone increases the peak ground acceleration hazard near Portland, Oregon by about 20%. Alternative attenuation relations for deep earthquakes can result in ground motions that differ by a factor of two. The hazard uncertainty for the plate interface and intraslab earthquakes is analyzed through a Monte-Carlo logic tree approach and indicates a seismic hazard exceeding 1 g (0.2 s spectral acceleration) consistent with the U.S. National Seismic Hazard Maps in western Washington, Oregon, and California and an overall coefficient of variation that ranges from 0.1 to 0.4. Sensitivity studies indicate that the paleoseismic chronology and the magnitude of great plate interface earthquakes contribute significantly to the hazard uncertainty estimates for this region. Paleoseismic data indicate that the mean earthquake recurrence interval for great earthquakes is about 500 years and that it has been 300 years since the last great earthquake. We calculate the probability of such a great earthquake along the Cascadia plate interface to be about 14% when considering a time-dependent model and about 10% when considering a time-independent Poisson model during the next 50-year interval.     

Microseismic Noise before and after Strong Earthquakes: Case Study of Chilean Subduction Zone

Izvestiya, Physics of the Solid Earth - Abstract—In this work, we study the parameters of microseismic noise in the vicinity of the Chilean subduction zone in order to detect oscillations of...     

俯冲带板缘与板内地震长周期地震动参数预测模型研究

对海域地震区划中涉及的我国海域有影响的俯冲带地震动参数预测模型研究进展与阶段性成果进行介绍,基于资料、回归方法等,对地震动参数预测模型建立过程进行说明。依托可靠的强震加速度记录与宽频带速度记录,采用使结果更稳定的分步回归方法,考虑俯冲带深大地震断层尺度与震源深度影响选取新的预测模型。针对我国海域实际地震环境,新的预测模型重点关注了对俯冲带长周期地震动的估计。     

Regularities in the Spatiotemporal Variations of Deformation Processes in the Region of Japan Subduction Zone

Izvestiya, Physics of the Solid Earth - The approach is proposed for modeling deformations in the subduction zones from the surface displacement data recorded by the methods of satellite geodesy....     

马尼拉俯冲带热结构数值模拟与地震意义

研究马尼拉俯冲带地震分布的成因机制,根据马尼拉俯冲带最新的莫霍面深度和地壳厚度等地质与地球物理资料,选取3条典型剖面,模拟俯冲带热结构。结果表明:1俯冲带热结构主要受俯冲角度、俯冲速度和俯冲板块本身地质条件等因素影响;2 BB′剖面和CC′剖面属于热俯冲;3当洋壳俯冲至软流圈边界时,俯冲板块温度迅速升高,容易形成地震活动。BB′剖面的俯冲角度和俯冲速度比CC′剖面小,使得BB′剖面发生地震的深度更浅。俯冲洋壳底部温度比顶部低,地震活动也持续到更大的深度。     

对俯冲带深震成因的探讨

根据一种准动力学计算方案,用有限元方法计算了不同模型俯冲带的热结构．在此基础上计算了俯冲带的密度分布和P波速度异常．通过与地震波探测结果和实验室破裂实验结果的对比,指出400 km以下俯冲带的地震可能由反裂纹机制所控制．     

Structure of the Hellenic Subduction Zone from Gravity Gradient Functions and Seismology

The Normalized Full Gradient (NFG) method has widespread applications in the analysis of potential fields, especially the gravity and magnetic fields. This method is used to identify the lateral and horizontal density variations in the crust and lithosphere. In this study, the NFG method was applied to the gravity data of the Cretan Arc and its surroundings. Because of the tectonic features of the eastern Mediterranean, the Cretan Arc and the neighboring areas are seismically very active. Especially the subduction zone and the complicated crustal features have been defined applying many different geophysical methods. In this study, first the NFG method is tested with synthetic prisms (two cubes). After that, the NFG method was applied to the Bouguer gravity data of the Cretan Arc and its subduction zone (Hellenic subduction zone) and Hellenic subduction zone was defined with the foci depth data (USGS) along the south–north direction. Thus, geometry of the focal depth distribution has been created to determine probable media depths and their localizations. According to the NFG results, vertical structural transitions were observed at a depth ranging between 10 and 180?km. Also, these results were compared with the foci depth model and the other results of the related publications. Finally, some considerations in vertical solution with the NFG method have been presented and locations of the different structures at horizontally have been defined with application of the NFG method.     

Source Investigation and Comparison of the 1939, 1946, 1949 and 1965 Earthquakes,Cascadia Subduction Zone,Western Washington

Over the past ~65 years intraslab earthquakes have caused the most significant damage in the western Washington region. This study examines regional and teleseismic seismograms for four historic, suspected intraslab events of M > 5.5 occurring within the Cascadia Subduction zone in 1939 (South Seattle), 1946 (Puget Sound), 1949 (Olympia) and 1965 (Sea-Tac) to better determine the source locations, mechanisms and rupture histories of these events. Our study is aided by digital seismograms of post-1990 intraslab events with well-determined focal depths and focal mechanisms that were recorded in the same locations as the historic events. Thus the recent events were used as empirical Greens functions to study the historic events. Our results suggest that the 1946 earthquake is not an intraslab event, that the 1939 event closely resembles the 1965 event, and that the 1949 event is similar to the 2001 Nisqually earthquake, although the 1949 event appears to have ruptured toward the south, causing significantly more damage than the Nisqually event. These results suggest that earthquakes periodically rupture along the same or similarly oriented faults within the subducting slab.     

Japan Trench and tectonics of the Japanese Island Arcs

Abstract Seven chronostratigraphic stages were established based on the correlation of magneto‐biostratigraphic marker horizons within the Deep Sea Drilling Project and Ocean Drilling Program cores from the forearc of the Japan Trench. Because the stages are coeval with changes in the rate of sedimentation, lithofacies, magnetic intensity and composition of fossil assemblages, they probably reflect the tectonic situation in the Japan Trench forearc and also in the arc–trench system. The stages correlate to the tectonic events of the Japanese Island Arcs; for example, evolution of the Boso triple junction, initiation of Philippine Sea Plate subduction and the Japan Sea opening.     

Overview of Recent Coastal Tectonic Deformation in the Mexican Subduction Zone

Holocene and Pleistocene tectonic deformation of the coast in the Mexico subudction margin is recorded by geomorphic and stratigraphic markers. We document the spatial and temporal variability of active deformation on the coastal Mexican subduction margin. Pleistocene uplift rates are estimated using wave-cut platforms at ca. 0.7?C0.9?m/ka on the Jalisco block coast, Rivera-North America tectonic plate boundary. We examine reported measurements from marine notches and shoreline angle elevations in conjunction with their radiocarbon ages that indicate surface uplift rates increasing during the Holocene up to ca. 3?±?0.5?m/ka. In contrast, steady rates of uplift (ca. 0.5?C1.0?m/ka) in the Pleistocene and Holocene characterize the Michoacan coastal sector, south of El Gordo graben and north of the Orozco Fracture Zone (OFZ), incorporated within the Cocos-North America plate boundary. Significantly higher rates of surface uplift (ca. 7?m/ka) across the OFZ subduction may reflect the roughness of subducting plate. Absence of preserved marine terraces on the coastal sector across El Gordo graben likely reflects slow uplift or coastal subsidence. Stratigraphic markers and their radiocarbon ages show late Holocene (ca. last 6?ka bp) coastal subsidence on the Guerrero gap sector in agreement with a landscape barren of marine terraces and with archeological evidence of coastal subsidence. Temporal and spatial variability in recent deformation rates on the Mexican Pacific coast may be due to differences in tectonic regimes and to localized processes related to subduction, such as crustal faults, subduction erosion and underplating of subducted materials under the southern Mexico continental margin.     

祁连山构造带地震迁移活动特征分析

祁连山构造带地震迁移活动研究表明,存在不同震级层次的地震迁移现象:①大震顺构造带迁移由东而西震级衰减;②中强地震沿构造带东、中、西段交替发生;③横构造带地震跳迁会影响顺构造带地震的有序迁移;④祁连山中东段—东段存在发生破坏性地震的背景。     

Identification of High Frequency Pulses from Earthquake Asperities Along Chilean Subduction Zone Using Strong Motion

The Chilean subduction zone is one of the most active of the world with M?=?8 or larger interplate thrust earthquakes occurring every 10?years or so on the average. The identification and characterization of pulses propagated from dominant asperities that control the rupture of these earthquakes is an important problem for seismology and especially for seismic hazard assessment since it can reduce the earthquake destructiveness potential. A number of studies of large Chilean earthquakes have revealed that the source time functions of these events are composed of a number of distinct energy arrivals. In this paper, we identify and characterize the high frequency pulses of dominant asperities using near source strong motion records. Two very well recorded interplate earthquakes, the 1985 Central Chile (Ms?=?7.8) and the 2007 Tocopilla (Mw?=?7.7), are considered. In particular, the 2007 Tocopilla earthquake was recorded by a network with absolute time and continuos recording. From the study of these strong motion data it is possible to identify the arrival of large pulses coming from different dominant asperities. The recognition of the key role of dominant asperities in seismic hazard assessment can reduce overestimations due to scattering of attenuation formulas that consider epicentral distance or shortest distance to the fault rather than the asperity distance. The location and number of dominant asperities, their shape, the amplitude and arrival time of pulses can be one of the principal factors influencing Chilean seismic hazard assessment and seismic design. The high frequency pulses identified in this paper have permitted us to extend the range of frequency in which the 1985 Central Chile and 2007 Tocopilla earthquakes were studied. This should allow in the future the introduction of this seismological result in the seismic design of earthquake engineering.