A seismic hazard study and analysis of the megathrust source off the west coast of North Sumatra, Indonesia, were conducted based on estimated horizontal crustal strain using the surface displacement data. This area was selected due to the availability of pre- and co-seismic GPS data for the 2005 Nias-Simeulue Mw 8.6 event. This study aims to estimate the Seismic Hazard Function (SHF), which is expressed as Peak Ground Acceleration (PGA) versus Probability of Exceedance (PE), for a 500-year return period using GPS data. The source area model of the Mw 8.6 is determined based on the co-seismic GPS data. The horizontal crustal’s strain of the source area is estimated using least square prediction employing local covariance functions based on the horizontal displacement data. The Mw 8.6 return period is estimated by dividing the sum of the coseismic seismic moment by the pre-seismic seismic moment based on GPS data. The seismicity rate model above a magnitude of completeness is then estimated assuming the b-value of 1 obtained on the previous study's earthquake catalog data in the region. We show that the SHF based on the study area's horizontal crustal strain is higher than the one based on earthquake catalogs and estimated geological slip-rate data. This discrepancy is associated with the static stress increase (CFS) of about a 0.25 bar imparted by the 2004 Aceh Mw 9.1 event that occurred in the north of the study region. We interpreted that the increasing the SHF was due to the increase in the region's stress load, which was well documented by the GPS data.

中文翻译：

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使用估计的西苏门答腊北部沿海水平地壳应变的地震危险函数映射

基于估计的水平地壳应变，利用地表位移数据，对印度尼西亚北苏门答腊岛西海岸的巨型推力源进行了地震危险性研究和分析。选择该区域是因为可获得2005年Nias-Simeulue Mw 8.6事件的地震前和同震GPS数据。这项研究的目的是使用GPS数据估算500年返回期的地震危险函数（SHF），表示为峰值地面加速度（PGA）与超标概率（PE）。Mw 8.6的震源区模型是根据同震GPS数据确定的。使用最小二乘预测法，根据水平位移数据，使用局部协方差函数来估算源区域的水平地壳应变。Mw 8。通过基于GPS数据将同震地震矩之和除以震前地震矩，可以估算出6个返回周期。然后，假设在先前研究的该地区的地震目录数据中获得的b值为1，则可以估算出完整度以上的地震速率模型。我们表明，基于研究区域水平地壳应变的SHF高于基于地震目录和估计的地质滑移率数据的SHF。这种差异与研究区域北部发生的2004年Aceh Mw 9.1事件引起的静应力增加（CFS）约0.25 bar有关。我们解释说，SHF的增加是由于该地区应力负荷的增加，而GPS数据已充分证明了这一点。