The Seismic Source Characteristics in the Alaska Subduction Zone Determined by the Cluster Event Method

• Main Authors: Chung-Hung Lo, 羅仲宏
• Other Authors: 郭本垣
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/44hvhh

碩士 === 國立臺灣大學 === 海洋研究所 === 106 === The Alaska subduction zone is known as an active subduction zone where earthquakes occur at high rate and widespread along the trench and down dip of the slab. In recent years, increasing numbers of seismic arrays have been installed in Alaska region that significantly increased aperture of observations. It provides an opportunity to systematically investigate depth-varying seismic source characteristics in subduction zone. The source characteristics can reflect the rupture behaviors of fault, but the differences in rupture behaviors as a function of depth are still notably debated. In this study, we employed a cluster-event method (CEM) to constrain the source parameters as well as along-path attenuation in the Alaska subduction zone. Neighborhood algorithm is applied to solve the nonlinear inverse problem. Using 40 stations from IRIS data management center, we analyzed 144 Alaska local earthquakes spreading over a depth range from surface to several hundred kilometers and a seismic magnitude range from 3 to 5 in 2012~2017. These source parameters are then converted to stress drop and radiated energy at different depths. The fc’s satisfy a self-similar scaling relationship with seismic moment of f_c∝〖M_0〗^(-3) with a mean stress drop of 18.34 ± 1.10 MPa in Madariaga’s form (Vs model). The lower radiation efficiency and higher stress drop might imply the shear heating instability and dehydration embrittlement as the same important faulting mechanisms for intermediate-depth earthquakes.