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2012年MW7.8海达瓜伊地震的逆冲震源机制表明该区穿过转换挤压型太平洋-北美板块边界的汇聚受俯冲作用调节,该机制对地震与海啸的灾害分析具有重要意义。本文使用5个陆基地震台的远震记录,通过接收函数非线性反演方法调查了海达瓜伊之下的地壳结构和俯冲范围。在2012年地震后布设了3个台站,将覆盖延伸到了东南部,这些台站在以前还没被分析过。反演估计了莫尔兹比岛很大部分的地下剪切波速度结构。结果表明存在一个深约18~26km的速度正异常,我们将其解释为浅的大陆莫霍面。我们还识别出了一个厚12~17km的剪切波低速带,其深度沿板块汇聚方向从约25km增大到42km,该层被解释为俯冲的海洋物质。这些结果首次提供了俯冲的海洋板块延伸到整个莫尔兹比岛之下的证据。
The thrust mechanism of the MW7.8 Haidaiguai earthquake in 2012 indicates that the convergence of the area through the transitional crustal Pacific-North American plate boundary is regulated by the subduction. This mechanism is of great significance to the earthquake and tsunami disaster analysis. In this paper, the teleseismic records of five ground-based seismic stations are used to investigate the crustal structure and subduction range under Haidagui by nonlinear inversion of receiver function. Three stations were deployed after the 2012 earthquake, extending coverage to the southeast, where these stations have not been analyzed before. Inversion estimates the subsurface shear wave velocity structure of much of the Dolzí Island. The results show that there is a velocity anomaly 18 ~ 26km deep, which we interpret as a shallow Moho. We also identified a 12-17 km thick shear-wave low-velocity zone, whose depth increases from about 25 km to 42 km along the plate convergence direction and is interpreted as a subducted marine mass. For the first time, these results provide evidence that the subducted oceanic plate extends below the entire of the Dolzí Island.