Acquisition of Long-Baseline Tiltmeters for Cascadia Slow Earthquakes

0320782墨尔本卡斯卡迪亚的周期性慢震是迄今为止通过对俯冲带的连续GPS监测发现的最具历史意义的信号之一。 然而，GPS测量是有限的，他们可以解决有关的瞬态蠕变过程的基本物理。特别是，垂直形变与GPS解决不好，每日GPS解决方案平均超过几天不能约束是否发生滑动离散，短命的情节预测的非均质滑动制度的故障。这项主要研究仪器拨款支持安装五个长基线倾斜仪，以补充太平洋西北大地测量阵列（PANGA）内正在进行的GPS测量。 这些仪器的空间和时间分辨率比全球定位系统高出近三个数量级，将能够捕捉到细微的垂直运动和伴随缓慢断层事件的变形的任何时间变化。 长基线倾斜仪将部署在北方普吉湾地区，并与现有的PANGA全球定位系统站位于同一地点，在那里，慢事件平均每14个月成核一次，误差为1个月。第一台倾斜仪预计将于2003年秋季安装，随后两年内再安装四台。 结合正在进行的GPS测量，增加倾斜仪将提高我们在位置和滑动持续时间方面的分辨能力，从约50公里和几天分别增加到不到1公里和几十分钟。

0320782MelbournePeriodic slow earthquakes in Cascadia constitute one of the most geophysically interesting signals detected to date with continuous GPS monitoring of subduction zones. However, the GPS measurements are limited in what they can resolve about the underlying physics of the transient creep process. In particular, the vertical deformation is poorly resolved with GPS; daily GPS solutions averaged over several days cannot constrain whether slip occurs in discrete, short-lived episodes predicted by heterogeneous slip regimes on faults. This Major Research Instrumentation grant supports installation of five long baseline tiltmeters in order to supplement ongoing GPS measurements within the Pacific Northwest Geodetic Array (PANGA). These instruments have almost three orders of magnitude higher spatial and temporal resolution than GPS, and will be able to capture fine scale vertical motion and any temporal variations in deformation that accompany the slow faulting episodes. The long baseline tiltmeters are to be deployed within the Northern Puget Sound region and co-located with existing PANGA GPS stations, where the slow events are known to be nucleating on average every 14 months, give or take 1 month. The first tiltmeter is expected to be deployed in the autumn of 2003, followed by four additional installations over the following two years. In conjunction with ongoing GPS measurements, the addition of the tiltmeters will increase our resolving power in location and duration of slip from ~50 km and several days to less than a km and tens of minutes, respectively.