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Mechanical properties of shallow fault rock in erosive margins: Influence on earthquake rupture propagation and slow slip events

侵蚀边缘浅断层岩石的力学特性：对地震破裂传播和慢滑移事件的影响

基本信息

批准号：
242236969
负责人：
Dr. Matt Ikari, Ph.D.
金额：
--
依托单位：
Institut für Geophysics
依托单位国家：
德国
项目类别：
Infrastructure Priority Programmes
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2014-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/242236969?language=en
关键词：
Mechanical properties shallow fault rock

项目摘要

Plate boundary thrust faults at convergent margins generate the largest and most destructive earthquakes, and tsunamis. Over half of worldwide subduction zones are erosional margins, inlcuding the Japan Trench and Costa Rica margins. The Mw = 9.0 Tohoku event in the Japan Trench demonstrates that erosive subduction zones are capable of generating great earthquakes and tsunamis. The shallow portions of subduction zones are of great importance for two reasons: (1) they may be prone to earthquake rupture and coseismic slip propagation and (2) they may generate slow earthquakes. Direct observation, monitoring and sampling of fault zones at seismogenic depths in subduction zones has yet to be achieved, but core samples from within and adjacent to major thrust faults have been recovered from shallow depths (~1 km or less). There is also evidence of shallow slow slip events offshore Costa Rica from borehole strainmeters and GPS data. Slow earthquakes also occur in the shallow near-trench region of the Japan Trench. Therefore, available natural samples obtained from well-described subduction zone settings, such as the Japan Trench and Costa Rica, are ideally suited for studying shallow earthquake rupture propagation and slow slip events. Describing the slip behavior of major fault zones relies heavily on the results of laboratory friction experiments. The proposed research intends to use core samples recovered during IODP Expedition 343 (Jfast) to the Japan Trench and ODP Leg 170 and 205 to the Nicoya Peninsula region offshore Costa Rica, in order to measure frictional strength and sliding stability. Measurements will cover lithologic variations in a vertical transect from the overlying sediment prism through the decollement and underthrust sediments in the Japan Trench. Further experiments will examine the effect of spatially varying lithology on the incoming plate in Costa Rica. Low slip velocities (<1 cm/s) will be used, which are critical for predicting the response of a fault zone to earthquake propagation. An important part of the testing program will be measurements of cohesive strength in both fault gouge and wall rock, which remains unexplored by the geophysical community but is a potentially key parameter. Additional experiments will be included which accurately mimic slow earthquakes in nature. Supplemented by detailed analyses of mineralogic composition by XRD and physical characterization of the sheared specimens by WLI, the proposed research will result in a comprehensive set of frictional property measurements revealing the mechanisms behind earthquake propagation and the occurrence of slow slip events in the shallow portions of erosive subduction zones.

在会聚边缘的板块边界逆冲断层产生最大和最具破坏性的地震和海啸。世界上一半以上的俯冲带是侵蚀边缘，包括日本海沟和哥斯达黎加边缘。日本海沟的Mw = 9.0的东北事件表明，侵蚀俯冲带能够产生大地震和海啸。俯冲带的浅部非常重要，原因有二：（1）它们可能易于发生地震破裂和同震滑动传播;（2）它们可能产生慢地震。在俯冲带的孕震深度对断层带进行直接观察、监测和取样尚待实现，但已从较浅的深度（约1公里或以下）采集到主要逆冲断层内部和附近的岩心样本。钻孔应变仪和GPS数据也证明了哥斯达黎加近海的浅层缓慢滑动事件。慢地震也发生在日本海沟的浅海沟附近地区。因此，从日本海沟和哥斯达黎加等俯冲带环境中获得的天然样品非常适合研究浅层地震破裂传播和缓慢滑动事件。描述主要断裂带的滑动行为在很大程度上依赖于实验室摩擦实验的结果。拟议的研究打算使用IODP第343次考察（Jfast）期间在日本海沟和ODP第170和205航次在哥斯达黎加近海的尼科亚半岛地区采集的岩心样本，以测量摩擦强度和滑动稳定性。测量将涵盖从上覆沉积物棱柱体到日本海沟滑脱和下冲断层沉积物的垂直断面中的岩性变化。进一步的实验将研究空间变化的岩性对哥斯达黎加板块的影响。将使用低滑动速度（<1厘米/秒），这对于预测断层带对地震传播的反应至关重要。测试计划的一个重要部分将是测量断层泥和围岩的内聚强度，这一点尚未被地球物理界探索，但却是一个潜在的关键参数。将包括其他实验，准确地模拟自然界中的慢地震。通过XRD对矿物成分的详细分析和WLI对剪切试样的物理表征，拟议的研究将产生一套全面的摩擦性能测量，揭示地震传播背后的机制和侵蚀俯冲带浅层缓慢滑动事件的发生。