多源數據聯合反演權比確定及玉樹地震同震斷層滑動分布反演研究

溫揚茂++許才軍++何平++江國焰++劉洋

摘 要：為了更好地研究重力場對地殼形變、活動斷層、地震等動力學過程的時變響應，需要建立動態地殼形變模型，研究重力、形變與地震波數據聯合反演活動斷層參數的相關理論及方法，進行活動斷層潛在地震的危險性評估，探討強震發生的動力學背景。該報告主要介紹兩個方面的研究內容：一方面是如何表述反演數據中多源數據的權矩陣，通過引入虛擬觀測方程將斷層滑動的連續性約束一并納入觀察方程，采用Helmert方差分量估計確定各類觀測數據的權比，推導了相關理論公式。另一方面，利用InSAR和GPS資料提取了Iwaki和Kita-Ibarake兩個余震區典型余震的同震形變場，以及結合InSAR干涉圖形狀和方位向偏移量法對發震斷層的幾何參數進行約束。在此基礎上，采用彈性半空間矩形位錯模型對這兩個強余震的同震滑動分布進行反演，得到的最大滑動量分別為3.28 m和0.98 m。最后利用余震的斷層作為接收斷層，計算了Mw 9.0 Tohoku-Oki靜態庫侖應力對余震作用的大小，結果顯示Iwaki和Kita-Ibarake研究區的余震近似為純正斷層類型的淺源地震，靜態庫侖應力在兩個研究區的最大值分別為1.1 MPa和0.7 MPa，表明Mw 9.0 Tohoku-Oki地震對研究區的余震觸發是有促進作用的。

關鍵詞：多源數據 反演 活動斷層 地震波數據 同震形變場

Abstract：In order to understand the time-dependent gravity response from crustal deformation， active fault， earthquakes and other dynamic processes， we need to estimate the kinematic crustal deformation model， to study theory and method of active fault parameters joint inversion from gravity， deformation and seismic data， to do the potential earthquake hazard assessment of active faults and to explore the dynamic background of strong earthquakes. This report focuses on the following two aspects： on one hand， we introduce the fault slip continuity constraint as a virtual observation function to observation functions， and determine the relative weight of various kinds of observation using Helmert variance component estimation. On the other hand， we derive the coseismic deformation of Iwaki and Kita-Ibarake aftershocks from InSAR and GPS data， and obtain the preliminary location of the fault traces combing InSAR deformation pattern with azimuth-offset measurements. The fault location and geometry of these two earthquakes are constrained by a rectangular dislocation model in a multilayered elastic half-space， which indicates that the maximum slips for the two earthquakes are 3.28 m and 0.98 m， respectively. The Coulomb stress changes are calculated for the faults following the 2011 Mw 9.0 Tohoku-Oki earthquake based on the modeled slip along the fault planes. The resulting Coulomb stress changes indicate that the stresses on the faults increased by up to 1.1 MPa and 0.7 MPa in the Iwaki and Kita-Ibarake regions， respectively， suggesting that the Tohoku-Oki earthquake triggered the two aftershocks， supporting the results of seismic tomography.

Key Words：Multi-source data；Inversion；Weight ratio；Dislocaiton model；Earthquake；InSAR

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