Collaborative Research: Acquisition of Continuous GPS and Borehole Geophysical Networks for Investigation of Seismogenic Processes at the Costa Rica Subduction Zone

0502488Schwartz这笔赠款将支持在尼科亚半岛购买和安装由9个连续运行的GPS站(CGPS)和3个钻孔宽带地震仪和倾斜仪组成的网络，以调查哥斯达黎加俯冲区的慢滑事件和幕间地震震动。新仪器将补充日本和哥斯达黎加同事部署的3个现有CGPS站，以及德国同事正在安装的6个钻孔地震观测站。这些国际合作将极大地提高该网络解决有关这一危险地区地震过程的基本问题的能力。慢滑事件或“无声地震”是最近观察到的一种应变释放模式，滑动发生在中间时间尺度上，通常是几天到几个月。在少数存在连续GPS或钻孔倾斜仪网络的俯冲带断层上检测到了这种类型的运动。相关的过程知之甚少，但慢滑事件与低频地震震动有关，可能是由于流体通过浅层俯冲系统的迁移造成的。板间断层上流体压力的增加可能会削弱它，使其更接近破裂。因此，慢滑事件可能预示着在大地震发生之前断裂前的断层破裂。尼科亚半岛钻孔地震和CGPS网络将有足够的密度和灵敏度来探测和研究慢滑事件和地震震动，并调查它们产生的过程。*

0502488SchwartzThis grant will support acquisition and installation of a 9 station network of continuously operating GPS stations (CGPS) and 3 boreholes broadband seismometers and tiltmeters on the Nicoya Peninsula to investigate slow slip events and episodic seismic tremor at the Costa Rican subduction zone. The new instrumentation will augment 3 existing CGPS stations deployed by Japanese and Costa Rican colleagues, and 6 borehole seismic observatories, being installed by German colleagues. These international collaborations will greatly enhance the ability of the network to address fundamental questions about earthquake processes in this hazardous region. Slow slip events or "silent earthquakes" are a recently observed mode of strain release where slip occurs over an intermediate time scale, usually days to months. This type of motion has been detected at a few subduction zone faults where continuous GPS or borehole tiltmeter networks exist. The processes responsible are poorly understood but slow slip events have been associated with low frequency seismic tremor, possibly caused by the migration of fluids through the shallow subduction system. Increased fluid pressure on the interplate fault could act to weaken it bringing it closer to failure. As a result, slow slip events may indicate pre-rupture fault breakdown prior to the occurrence of a large earthquake. The Nicoya Peninsula borehole seismic and CGPS networks will have sufficient density and sensitivity to detect and study slow slip events and seismic tremor and investigate the processes responsible for their generation.***