Seismogenesis of megathrust earthquakes at the Costa Rican erosive continental margin

2011年9.0级的日本东北地震破坏了侵蚀性大陆边缘，出乎意料地到达了海沟轴线。因此，我们目前的理解受到了挑战，因为物质和逆冲断层的性质本应造成负应力降，从而很好地阻止了海沟向陆地方向的破裂。2002年发生在哥斯达黎加近海的里氏6.4级地震可能也表现出了类似的行为。然而，全球事件定位与太大的误差和温度估计有关，温度估计对评估大型逆冲构造的摩擦状态至关重要，受到与上板块热性质有关的不确定性的影响。我们将使用一套独特的当地地震学数据，这些数据来自奥萨地震的破裂区，并确定一个三维速度模型，这将使我们能够获得主震和余震的精确震源参数，这些参数可以根据地震测量和钻探的结构信息进行评级。此外，哥斯达黎加地震成因项目（CRISP）旨在研究在侵蚀性俯冲带控制大地震成核和地震破裂传播的过程，IODP钻探提供了去年的leg 334和今年的leg 344独特数据，以约束地震带的热结构。地震学数据将与来自IODP钻探探险的热数据和钻井数据一起进行解释，以完善侵蚀收敛边缘温度和地震发生之间的联系。

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.