Seismogenesis of megathrust earthquakes at the Costa Rican erosive continental margin

2011年日本东北部发生的Mw=9.0的地震破坏了侵蚀性大陆边缘，并意外地到达了海沟轴。因此，我们目前的理解受到了挑战，因为材料和逆冲断层的性质应该引起负应力下降，阻止破裂以及向陆的沟槽。2002年奥萨6.4级地震在哥斯达黎加近海可能也表现出类似的行为。然而，全球事件本地化与太大的误差和温度估计-关键评估的摩擦状态的巨型逆冲断层-遭受的不确定性有关的上板的热性能。我们将使用一套独特的当地地震数据，从奥萨地震的破裂区，并确定一个3-D速度模型，使我们能够产生精确的震源参数的主要和余震，可以根据地震勘测和钻井的结构信息进行评级。此外，哥斯达黎加地震成因项目旨在研究控制侵蚀俯冲带大地震成核和地震破裂传播的过程，IODP钻探提供了去年第334航次和今年第344航次的独特数据，以限制地震成因带的热结构。地震学数据将与IODP两次钻探考察的热数据和钻探数据一起进行解释，以确定侵蚀会聚边缘温度与地震成因之间的联系。

The Mw=9.0 2011 Tohoku earthquake ruptured an erosive continental margin and reached unexpectedly the trench axis. Our current understanding is thus challenged as the material and thrust fault properties should have caused a negative stress drop, stopping rupture well landward of the trench. In 2002 the Mw=6.4 Osa earthquake may have shown a similar behavior offshore of Costa Rica. However, global event localization is associated with too large errors and temperature estimates – critical to assess the frictional state of the megathrust – suffer from uncertainties related to the thermal properties of the upper plate. We will use a unique suite of available local seismological data from the rupture area of the Osa earthquake and determine a 3-D velocity model that will allow us to yield precise source parameters of the main and aftershocks that can be rated against structural information from seismic surveying and drilling. Further, the Costa Rica Seismogenesis Project (CRISP) was designed to study the processes that control nucleation and seismic rupture propagation of large earthquakes at erosive subduction zones and IODP drilling provides with last year’s leg 334 and this year’s leg 344 unique data to constraint the thermal structure of the seismogenic zone. The seismological data will be interpreted jointly with thermal and drilling data from both IODP drilling expeditions to refine the link between temperature and seismogenesis at erosive convergent margins.