Source Parameters and Rupture Characteristics of Earthquakes Occur in Moderate and Deep Depth in Manila-Taiwan-Ryukyu Collision System

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基本資料

Project title

Code/計畫編號

MOST108-2116-M019-007

Translated Name/計畫中文名

馬尼拉-臺灣-琉球碰撞系統之中、深源地震特性研究

Project Coordinator/計畫主持人

Yi-Ling Huang

Funding Organization/主管機關

National Science and Technology Council

Co-Investigator(s)/共同執行人

黃瑞德

Department/Unit

Institute of Earth Sciences

Website

https://www.grb.gov.tw/search/planDetail?id=13118630

Year

2019

Start date/計畫起

01-08-2019

Expected Completion/計畫迄

31-07-2020

Bugetid/研究經費

1225千元

ResearchField/研究領域

地球科學

臺灣位處菲律賓海板塊與歐亞大陸板塊碰撞的位置上，南有馬尼拉碰撞系統，東北銜接琉球碰撞帶，整個區域深淺地震發生頻繁，且不乏中、大規模地震的發生，因此，探討此區域孕震帶地震的震源參數關連十分重要，在學術上可藉此了解整個碰撞帶的孕震特性，在防災上也可以提供對大地震震源歷時、破裂長度等等參數的預估，以及提供震源破裂模擬或地動模擬的依據。震源參數可幫助研究了解地震的破裂行為，而其中，震源時間函數(source time function)是了解震源物理的重要參數之一，其反應地震發生到結束的時間歷程，不僅記錄了震源破裂歷時，也記錄了震源破裂特徵。震源破裂歷時包括了震源上揚時間(rise time)和破裂時間(rupture time)，上揚時間可以用以討論震源的動態破裂(dynamic rupture)行為，也反應出斷層強度的強弱，如動應力降(dynamic stress drop)、滑移速度(slip velocity)的變化等；破裂時間則反應了地震破裂尺度、破裂速度(rupture velocity)、破裂方向性 (rupture directivity)等。此外，震源時間函數也可用來估算震源輻射能量、反演震源破裂過程、分析震源的多重破裂及破裂速度變化等。從前人研究文獻可知，過去在整個馬尼拉-臺灣-琉球碰撞系統內對於震源歷時、破裂速度、破裂長度及震源輻射能量缺少系統性的研究，尤其所有研究成果幾乎都集中在臺灣區域。然而，整個碰撞帶由南到北、甚至更南更北延伸至印尼和日本，孕震系統息息相關，如何建立一套系統性的分析來探討整個碰撞系統內震源參數間的關係是極重要的，特別是震源歷時與地震矩的關係。而震源時間函數即包含了上述這些震源參數的訊息。因此，本計畫利用先前計畫已得之結果結合Hwang et al. (2017b)所開發的非負解平滑化阻尼最小平方時間域解迴旋技術，從遠震P波資料研究馬尼拉-臺灣琉球碰撞系統震矩規模大於5.0之地震的震源時間函數，並依此探討震源歷時、破裂速度、破裂長度及震源輻射能量與地震矩的關係，除探討震源破裂的物理特徵外，也期望能提供在地震防災評估上的參考。結果顯示在深度解和斷層面解上，本研究的結果與USGS和 GCMT的解非常一致，但在震矩的估算上，本研究的結果都偏低。本研究求得的震源歷時與地震矩關係介於前人估算所得的關係式之間，此結果隱含本研究區域的構造十分複雜，非為典型隱沒構造；從震源歷時與深度關係結果顯示，此兩參數沒有顯著的相關性、平均震源歷時大約5秒，這與前人研究結果不甚一致，這也顯示此區域構造的複雜性，此也隱含著即使估算的是平均震源歷時，震源的破裂方向性也仍需要被考量。This study presents the results of an improved method using the depth phases to probe the focal depths and source duration of intermediate-depth Earthquakes (cf. Lin et al., 2006; Hwang et al., 2010; Hwang et al., 2012). In the method, an additional constraint on the direct P-wave fitting was introduced into the inversion procedure and the earthquakes occurring in the region of Manila-Taiwan-Ryukyu collision system were analyzed to show the validation of the proposed method. The analyzing results could be characterized by the following: (1) The derived focal depths for the twenty events through the proposed teleseismic P-wave method under giving a series of focal depths (1-300 km at 1-km interval) and source duration (1- 20 sec at 0.1-sec interval) clearly revealed that the best depth is determined from the global minimum of misfit, not a local minimum. (2) The comparisons between the derived depths and seismic moments from this study with those from the GCMT (Global CMT) and USGS shows that the focal depths and seismic moments estimated from this study were well correlated with the USGS and the GCMT solutions. (3) The fault plane solutions determined from this study are also in agreement with those from the USGS and GCMT. (4) The results also support that the proposed method be efficient for determining the intermediate-depth earthquakes with moderate size. (5) The rupture directivity for the twenty earthquakes from the azimuth-dependent source duration was not estimated in this study, but the average source duration for each earthquake was calculated. However, the average source duration from this study is inconsistent with that from an empirical relationship between the source duration and seismic moment. It may imply that the rupture directivity of source is in need of analysis for obtaining the average source duration.

Keyword(s)

震源時間函數
震源輻射能量
地震矩
source time function
source radiation energy
seismic moment

DSpace CRIS

Source Parameters and Rupture Characteristics of Earthquakes Occur in Moderate and Deep Depth in Manila-Taiwan-Ryukyu Collision System

基本資料

Description