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

地震静止和地震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一种假设，即一个地区的破裂或无声滑动所传递的应力变化可以引起其他地区的地震变化。然而，地震的聚类特征使得我们无法探测到其他区域传递的应力变化引起的地震活动性变化，因为在非均质分形介质下，连续地震是由复杂的机制触发的。然而，我们可以使用统计经验规律作为预测地震群的实用方法。因此，本研究的目的是证明基于流行病型余震序列（ETAS）模型拟合区域地震活动性的诊断分析有助于检测外源应力的变化。特别是，无声滑动引起的变化通常非常微小，以至于人们几乎无法识别系统异常……更多的是在没有ETAS模型帮助的情况下的地震活动性。利用ETAS触发地震模型可以很好地预测某一地区地震的一般短期发生率。任何异常地震活动，如静止和激活，都可以通过识别与预测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，在2004年日本中部发生6.8级中越地震之前的三年时间里，发现了这种异常现象。在库仑破坏应力负增量区和正增量区分别发生静止和激活，可能是由于震源断面的无声滑动或其较低倾角向深部延伸所致。这种滑动进一步受到震源周围瞬态地壳运动的支持。许多永久GPS台站间基线距离的时间序列记录与预测的线性趋势有明显偏差，其偏差大多与中越地震引起的GPS台站同震水平位移一致。此外，与理论位移相比，主震断裂面延伸较深，倾角较低，可以解释观测到的基线偏差较多的情况。累积的前兆滑动估计大致相当于m6的矩量级。少

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