Characteristics of Earthquakes Near Plate Interfaces

这项提议寻求对一个为期两年的项目的支持，该项目旨在调查瓦达蒂-贝尼奥夫地区板块界面附近地震活动的复杂但系统的变化。特别是，我们计划描述大量主要是正常的断层事件的性质，这些事件不能用板间逆冲带上的滑动来解释。通过对远震距离的长周期P波和SH波的反演以及对短周期地震记录地表反射的识别，将精确地确定主要俯冲带中浅于100公里的大约100次中等地震的深度和机制。我们预计会更详细地圈定板块界面的位置和附近的地震活动。然后，结果将与外部隆起区事件和从界面向下倾斜的板内地震活动的震源参数汇编结合在一起。我们试图阐明板块界面附近逆冲断层事件和正断层事件的可能联系，中等深度板间地震活动向板内地震活动过渡的性质，以及外隆起区、板块界面下方和界面外向下倾方向的板内地震活动之间的联系。综合的最终目标是确定地震震源参数可以对板块界面和俯冲岩石圈的应力状态施加的限制。我们认为，拟议的研究将提供足够的数据，至少定性地解决几个重要问题。例如，如果板块界面以下的事件的发生和机制可以与被认为控制板间带地震耦合的板块构造参数相关联，那么这些事件可以提供关于这两个区域都发生的信息，将研究板内应变场从岩石圈向海沟弯曲到中等深度不弯曲的转变。

This proposal seeks support for a two-year project to investigate the complex but systematic variation of earthquake activities near plate interfaces in Wadati-Benioff zones. In particular, we plan to characterize the nature of a notable number of predominantly normal faulting events that cannot be accounted for by slip on the interplate thrust zone. The depth and mechanism of approximately 100 moderate- sized earthquakes that are shallower than 100 km in major subduction zones will be precisely determined by inverting the long-period P and SH waves at teleseismic distances and by identification of surface reflections from short-period seismograms. We anticipate delineating the position of the plate interface and the seismicity near it in some detail. The results will then be combined with a compilation of source parameters for events in the outer-rise region and intraplate seismicity downdip from the interface. We seek to clarify the possible association of thrust and normal faulting events near the plate interface, the nature of the transition from interplate to intraplate seismicity at intermediate depths, and the connection between intraplate seismicity in the outer-rise region, beneath the plate interface, and beyond the interface in the downdip direction. The ultimate goal of the synthesis is to identify constraints that can be placed upon the state of stress both on the plate interfaceand the subducted lithosphere by the source parameters of earthquakes. We believe that the proposed study would provide enough data to at least qualitatively address several important questions. For instance, if the occurrence and mechanism of events below the plate interface can be correlated with plate tectonic parameters that are believed to control the seismic coupling of the interplate zone, then these events might provide information about the zone both occur, the transition of the strain field within the slab from lithospheric bending seaward of trenches to unbending at intermediate depths will be investigated.