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2001年日本西南兵库县北部地区发生的一次地震(Mw5．2),一些余震群沿着不同于主震走向的方向发生。首先,我们通过近源强地面运动波形反演对此次事件的破裂过程进行研究。虽然这是一次5级地震,但高密度强震观测台网记录到了高质量的波形数据。为了取得震源反演的精确格林函数,我们通过对小事件实测波形数据的前向模拟来标定地壳结构模型。从0．4至2．0Hz波形数据反演得出的破裂过程似乎较为简单。较大的滑动区位于破裂成核点周围。其次,我们还研究了主震和大余震造成的静态应力变化对后续地震活动的影响。我们利用波形反演得到的主震断层面上的不均匀滑动分布,并考虑到随后大余震的影响,对库仑破裂函数(△CFF)变化进行了计算。因此, 我们得出了震源区库仑破裂函数复杂的时空分布。大多数偏离主震断层的余震都发生在正库仑破裂函数区域内。这种结果表明,这些余震强烈地受到由主震和大余震引起的库仑破裂函数的影响。
In 2001, an earthquake (Mw 5.2) occurred in the northern Hyogo area of southwestern Japan. Some aftershocks occurred in a direction different from the direction of the main shock. First of all, we study the rupture process of this event by inversion of near-surface-strong ground motion waveform. Although this is a magnitude 5 earthquake, high-intensity strong earthquake observation network recorded high-quality waveform data. In order to obtain the accurate Green’s function of the source inversion, we calibrate the crustal structure model by forward modeling the measured waveform data of small events. The rupture process, which is inversed from 0.4 to 2.0 Hz waveform data, appears to be simpler. Larger sliding zone is located around the nucleation point of rupture. Secondly, we also study the influence of the static stress change caused by the main shock and the aftershock on the subsequent seismic activity. We use the inversed slip distribution on the fault plane of the main shock obtained from the waveform inversion, and calculate the change of the Coulomb failure function (ΔCFF) considering the effect of the subsequent aftershock. Therefore, we conclude the complex spatial-temporal distribution of Coulomb rupture in the focal region. Most of the aftershocks deviated from the main shock fault occurred in the area of positive Coulomb failure function. This result shows that these aftershocks are strongly affected by the Coulomb failure function caused by the main and major aftershocks.