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Development for Statistical Earthquake forecasting. Seismic and geodetic anomalies preceding the rupture around the focal region detected by statistical models

统计地震预报的发展。

基本信息

批准号：
17200021
负责人：
OGATA Yosihiko
金额：
$ 22.88万
依托单位：
The Institute of Statistical Mathematics
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

Seismic quiescence and activation, as the precursors to large earthquakes, have attracted much attention among seismologists. Of particular interest is the hypothesis that the stress-changes transferred from a rupture or silent slip in one region can cause seismic changes in other regions. However, the clustering feature of earthquakes prevents us from detecting the seismicity change due to stress change transferred from other region because successive earthquakes are triggered by complex mechanisms under heterogeneous fractal media. Nevertheless, we can use the statistical empirical laws as a practical method for predicting earthquake clusters. Thus, the objective of this research is to demonstrate that diagnostic analysis based on fitting the Epidemic Type Aftershock Sequence (ETAS) model to regional seismicity can be helpful in detecting exogenous stress changes there. In particular, the changes due to silent slips are usually so slight that one can barely recognize systematic anoma … More lies in seismicity without the aid of the ETAS model.The ordinary short-term occurrence rate of earthquakes in a region is well predicted using the ETAS model of triggering earthquakes. Any anomalous seismic activity, such as quiescence and activation, can be quantified by identifying significant deviation from the predicted rate. Thus we have successfully made a number of case studies. For example, such anomalies are revealed to have occurred during the three year period leading up to the 2004 Chuetsu Earthquake of Magnitude 6.8, central Japan. The quiescence and activation, which took place in the region of negative and positive increments of the Coulomb Failure Stress, respectively, were possibly caused by silent slip on the focal fault plane, or its deeper extension with a lower dip angle.Such slip is further supported by transient crustal movement around the rupture source. The time series records of many baseline distances between the permanent GPS stations significantly deviated from the predicted linear trends, mostly with the deviations consistent with the coseismic horizontal displacements of the GPS stations due to the Chuetsu Earthquake. Furthermore, a deeper extension of the mainshock fault plane, with a lower dip angle, can explain the more cases of the observed baseline deviations in comparison with the theoretical displacement. The cumulated precursory slip is estimated to be roughly equivalent to M6in the moment magnitude. Less

地震活动的平静和激活作为大地震的前兆，一直受到地震学家的关注。特别令人感兴趣的是这样一种假设，即从一个地区的破裂或无声滑动转移的应力变化可以引起其他地区的地震变化。然而，地震的丛集性特征使我们无法检测到由于来自其他区域的应力变化而引起的地震活动性变化，因为连续的地震是在非均匀分形介质下由复杂的机制触发的。然而，统计经验规律可以作为预测地震群的一种实用方法。因此，本研究的目的是证明诊断分析的基础上拟合的流行型余震序列（ETAS）模型区域地震活动性可以帮助检测外源应力变化。特别是，由于无声滑动的变化通常是如此轻微，人们几乎不能识别系统性异常 ...更多信息用ETAS触发地震模型较好地预测了一个地区地震的一般短期发生率。任何异常的地震活动，如平静和激活，都可以通过识别与预测速率的显著偏差来量化。因此，我们成功地进行了一些案例研究。例如，这样的异常被揭示在导致2004年日本中部的6.8级地震的三年期间发生。分别发生在库仑破裂应力负增量和正增量区域的平静和活化，可能是由于震源断层面上的无声滑动或其较低倾角的更深延伸造成的，这种滑动还得到了震源附近地壳瞬时运动的进一步支持。许多永久GPS站之间基线距离的时间序列记录明显偏离预测的线性趋势，大多数偏离与由于中越地震引起的GPS站的同震水平位移一致。此外，主震断层面的延伸更深，倾角更小，可以解释更多的情况下，观察到的基线偏差与理论位移相比。累积的地震滑动估计大致相当于M6的矩震级。少