The Source Parameters and Rupture Characteristics of Large Earthquakes Occur in Moderate and Deep Depth (Ii)

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Project title

Code/計畫編號

MOST106-2116-M019-001

Translated Name/計畫中文名

大規模之中、深源地震震源參數與斷層破裂特性研究(II)

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=12240525

Year

2017

Start date/計畫起

01-08-2017

Expected Completion/計畫迄

01-07-2018

Bugetid/研究經費

1008千元

ResearchField/研究領域

地球科學

"震源參數可幫助研究了解地震的破裂行為，其中，震源深度(focal depth)提供了關於孕震構造、板塊邊界運動及碰撞型態等的重要訊息，而震源時間函數(source time function)是了解震源物理的重要參數之一，其反映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。傳統上，震源深度可用一已知模型與P 波到時資料去順推(forward)求取，也可用波形逆推(inversion)從震矩張量(moment tensor inversion)的演算求得，這兩種方式得到的震源深度意義不同，數值上通常有差異。除了以上方式，地震學家尚發展出其它方法利用深度波相去定出震源深度、並改善計算過程中會存在的誤差，而這些方法中大部份皆須已知地震的斷層面解。震源時間函數的歷時包括了震源上揚時間(rise time)和破裂時間(rupture time)，這兩個時間反映出地震不同的破裂特徵。上揚時間可用以討論震源的動態破裂(dynamic rupture)行為，也反映出斷層強度的強弱，如動應力降(dynamic stress drop)、滑移速度(slip velocity)的變化等；破裂時間則反映了地震破裂尺度、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。本研究的目標在於將不須先已知地震斷層面解之遠場P 波逆推方法改進推展，嘗試使用於中、深源震源深度的計算及其它震源參數的推求，演算所得之參數再做為下一步演算工作的基礎，進而再推求時間函數、斷層破裂方向性及多重破裂演算等，以探討中、深源地震的複雜發震機制與斷層特性，更進而可探討不同類型板塊隱沒過程中所引發的地震特性。本研究將分階段逐步進行，首先應用已證實於淺源地震的參數推求上有良好及穩定結果的P 波逆推法於中、深源地震震源參數的推求，以改進並確定程式的可行性與所得結果的穩定性；接著，有系統的將中亞地區震矩規模6.0 以上之地震做完分析以探討此特殊隱沒構造的發震特性；最後，將對各種不同類型隱沒區的資料做分析比對，歸結出不同隱沒構造的地震與斷層破裂特徵。" "Source parameters imply the important information of fault rupture. Focal depth is one of them and supplies the messages about seismogenic structure, plate boundary activity and collision pattern. Another important source parameter is source time function. It supplies the information of fracture history and records not only the rupture duration but also the feature of rupture. Traditionally, focal depth can be estimated by forward or inversion. In forward method, an known velocity model and P wave arrival times are needed for the estimation. In inversion method, focal depth finally been decided from the calculation of moment tensor inversion. The significances of focal depths estimated from forward and inversion are different, and the values are usually discrepant. Furthermore, some other methods are developed for estimating the and improving the precision of focal depth by using deep phases. However, most of those methods need the known focal mechanism for calculation. The duration of source time function includes rise time and rupture time, they imply different features of fault rupture. Rise time implies the strength of fault material and can supply the information for discussing the dynamic rupture behavior of source, for instance, dynamics stress drop, slip velocity variation. Rupture time involves the rupture scale, rupture velocity and rupture directivity of fault. Source time function also can be used to study the source energy radiation, rupture process, multiple fracture and rupture velocity variation of fault. The aims of this project are: to improve and apply a far-field P wave inversion method which does not need an known focal mechanism to estimate the focal depth and some other source parameters of moderate and deep events; taking the results above-mentioned to be the basic information for estimating the source time function, rupture directivity and multiple fracture of fault; discussing the complicated characteristics of seismogenic mechanism and probe into the cases from different subduction system."

Keyword(s)

震源參數
破裂方向性
多重破裂
source parameter
rupture directivity
multiple fracture

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The Source Parameters and Rupture Characteristics of Large Earthquakes Occur in Moderate and Deep Depth (Ii)

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