Seismic hazard in western Canada from GPS strain rates versus earthquake catalog
Seismic hazard in western Canada from GPS strain rates versus earthquake catalog
复制标题
DOI：
10.1029/2011jb008213
复制
发表时间：
2011-12
影响因子：
--
通讯作者：
S. Mazzotti;L. Leonard;J. Cassidy;G. Rogers;S. Halchuk
中科院分区：
文献类型：
--
作者：
S. Mazzotti;L. Leonard;J. Cassidy;G. Rogers;S. Halchuk
[1]概率地震危险性分析（PSHA）通常基于50-100年地震目录的频率-震级统计数据，假设这些统计数据代表了大地震的长期频率。我们在加拿大西部大陆测试了另一种PSHA方法，包括美国西北部的邻近地区，使用来自179个全球定位系统（GPS）水平速度的区域应变率。GPS应变率转换为地震统计，地震矩率，地震震源区的地面震动概率，使用逻辑树方法的不确定性传播。基于GPS的矩速率和震动估计中值与仅两个区域（普吉湾和温哥华岛中部）的地震目录中得出的结果一致。在大多数其他地区，基于GPS的矩率中值比从地震目录中得出的矩率大6-150倍（震动估计大2-5倍），尽管基于GPS和目录的估计通常在67%的不确定性范围内一致。这种差异可能代表了长期矩率和地震目录在某些地区震动的采样不足，但是在我们整个研究区域不太可能有系统的采样不足。尽管没有以高置信度进行证明，但长期区域非地震变形可能是GPS/目录差异的重要组成部分，并且在某些地区，占总变形预算的90%。为了将GPS应变率整合到PSHA模型中，需要根据潜在的力学过程对长期变形的地震与抗震分区进行量化和理解。
[1] Probabilistic seismic hazard analyses (PSHA) are commonly based on frequency - magnitude statistics from 50–100 yearlong earthquake catalogs, assuming that these statistics are representative of the longer-term frequency of large earthquakes. We test an alternative PSHA approach in continental western Canada, including adjacent areas of northwestern U.S.A., using regional strain rates derived from 179 Global Positioning System (GPS) horizontal velocities. GPS strain rates are converted to earthquake statistics, seismic moment rates, and ground shaking probabilities in seismic source zones using a logic-tree method for uncertainty propagation. Median GPS-based moment rates and shaking estimates agree well with those derived from earthquake catalogs in only two zones (Puget Sound and mid-Vancouver Island). In most other zones, median GPS-based moment rates are 6–150 times larger than those derived from earthquake catalogs (shaking estimates 2–5 times larger), although the GPS-based and catalog estimates commonly agree within their 67% uncertainties. This discrepancy may represent an under-sampling of long-term moment rates and shaking by earthquake catalogs in some zones; however a systematic under-sampling is unlikely over our entire study area. Although not demonstrated with a high confidence level, long-term regional aseismic deformation may account for a significant part of the GPS/catalog discrepancy and, in some areas, represent as much as 90% of the total deformation budget. In order to integrate GPS strain rates in PSHA models, seismic versus aseismic partitioning of long-term deformation needs to be quantified and understood in terms of the underlying mechanical processes.