2019-01-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/710557摘要：尾波是指地震直達波之後到達一連串持續振盪且振幅逐漸衰減的訊號，一般被視為在傳遞介質當中隨機分佈的不均質點散射來回多次之後的能量，其波場較直達波更趨近於能量均分的狀態。由於具備對介質的速度構造和散射性質的微弱變化非常敏感，近年來尾波干涉法，利用兩兩測站所記錄的連續週遭噪訊進行交互相關函數計算得到隨時演進的經驗格林函數，然後量測其中尾波部分相對到時偏移量和波形退相干性程度隨時間的變化，用以偵測天然災害事件，如地震，火山噴發和塊體滑坡發生前後，引起附近地殼應力狀態或岩層組成物質性質改變的分佈情況及其成因。本研究計劃提出結合週遭噪訊和地震尾波干涉法分析台灣自1999年集集地震以來規模大於6.0以上的地震事件前後，於震央附近地殼速度和散射性質所發生的微小變化是否引起顯著的尾波到時和波形改變。量測的到時和波形變化將作為觀測數據，利用輻射轉移理論所推導其對地殼速度構造和散射結構的敏感度算核，進行尾波層析成像，逆推出地殼彈性速度構造和散射性質隨時間的動態分佈，藉以用來了解造成這些時空變化的物理成因。<br> Abstract: Coda waves are often considered as multiply-scattered energy which bounces many times between heterogeneous point scatterers distributed randomly in the propagation medium and nearly achieves a diffuse field with the property of modal equipartition. Because of their extreme sensitivity to weak changes in the properties of the medium, coda wave interferometry has become a powerful tool used to detect small temporal variations of seismic properties in the earth’s crust impacted by earthquake, volcanic, and landslide hazards. In this study, we propose to apply this technique to mapping spatiotemporal variations in seismicvelocity and scattering properties around the epicentral regions before and after large earthquakes (Mw>6.0) that hit Taiwan since 1999 Mw7.6 Chi-Chi Earthquake. We will measure the time-lapse changes in traveltime shifts and waveform decorrelation of the coda extracted from the empircal Green`s functions between two stations calculated by cross correlation functions (CCFs) of continuous ambient noise and S-wave coda of earthquakes. With the sensitivity functions for the measured codawave observables derived from the radiative transfer theory, we will carry out coda wave tomographic imaging towards simultaneously monitoring the time-evolving and spatially-varying perturbations in the mechanical (rigidity) and scattering properties of the crust in response to possible stress changes, rock failure, or fault zone damages caused by earthquake activities.尾波干涉法多重散射週遭噪訊交互相關函數經驗格林函數輻射轉移理論敏感度算核尾波層析成像coda wave interferometrymultiple scatteringambient noisecross correlation functionempirical Green`s functionradiative transfer theorysensitivity functionscoda wave tomography