1993年11月13日堪察加大地震的破裂过程及其构造意义

RUPTURE PROCESS OF THE NOVEMBER 13,1993,GREAT KAMCHATKA EARTHQUAKE FROM BROADBAND WAVEFORM ANALYSIS AND ITS TECTONICS IMPLICATIONS

用宽频带波型拟合方法研究了１９９３年１１月１３日堪察加东部沿海Ｍｓ＝７．１大地震的破裂过程．宽频带垂直向Ｐ＋ｐＰ＋ｓＰ波组的波形拟合和震源时间函数的分析表明，发震断层面走向１８４°，倾角３３°，滑动角７３°．破裂过程分为３个阶段：首先破裂成核并向北扩展，继而转向北东东方向扩展；然后又转向北东方向，形成一个更大的破裂，破裂由深向浅发展．这种复杂的破裂图像与该区的地壳结构和构造应力场具有直接的联系．

The rupture history of the November 13, 1993,eastern off coast of Kamchatka (Ms 7.1)earthquake was studied using broadband data of global seismograph network.Teleseismic broadband P+pP+sP waveforms from 20 stations were modelled.For each station,the depths and source time functions of subevents were obtained by trail-and-error modelling.By analysing the source time functions it can be deduced that the earthquake contains three steps of rupture propagation: first the rupture nucleates and propagates northward,then turns NEE and finally propagates in the NE direction,forming a larger rupture and then stops.The NS or NNE oriented nodal is the preferred fault plane seen from broadband analysls. By comparison with the seismicity,earthquake mechanism and volcanic activity in this region it can be found that the main tectonic cause of this stress release event comes from the subduction of Pacific plate under the Eurasian plate.