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  • 學位論文

2006年Mw 6.1台東地震引起淺層地殼速度隨時間變化和其成因探討

Temporal Variations of Crustal Seismic Velocities Associated with the 2006 Mw 6.1 Taitung Earthquake in the Arc-Continent Collision Suture Zone of Southeast Taiwan

指導教授 : 洪淑蕙

摘要


假設在均質的散射場中,兩測站的連續紀錄(噪訊)進行交互相關函數(CCF)運算,所得到的波形為近似於這兩測站之間的格林函數,亦稱為噪訊干涉法。相較於傳統地震學,雜訊即是震源的觀念將會提供更多有利於分析的資料,進而量測重建經驗格林函數(EGF)的相對速度變化、隨時間演變情形、以及探討其變化量對應物理介質的改變。由於菲律賓海板塊傾斜碰撞歐亞大陸板塊,造成台灣東部地震活動頻繁,2006 年4 月Mw 6.1的淺層地震發生在東台灣南段縱谷斷層,造成台東附近有顯著的同震變形現象。為了觀察震前與震後的地殼內部應變變化分布的情形,分別由自我相關函數(ACF)和CCF運算重建出EGF,在計算EGF之前先將連續記錄作正歸化處理。接下來,採用疊加方式來提高格林函數波相的一致性(coherence),分別為長期和短期平均的格林函數(Reference GF and Current GF),再使用拉張和移動視窗方法來量測他們尾波的相對速度值。高頻(2-8 Hz)ACF的量測結果只有距離震央南方約7公里的測站在主震後量測值突然下降,根據大地測量和地震定位的結果指出該站位處於斷層破裂帶附近,兩條斷層互相垂直滑移,造成該站附近有大量的同震地表位移和餘震分布,因此介質的速度擾動極有可能受到兩條斷層交界處具有岩性碎裂和滑移量分布集中的情形;低頻(0.1-0.9 Hz)測站對之間的結果顯示更短間距的測站通過震央南方和東南方也有同震相對速度變慢的情形,我們推測其背後機制極可能與靜態體積應變呈現拉張狀態有關。此外,震後的觀測值(十月份後)也逐漸增加到震前的狀態(四月份前),與區域性降雨量呈現正相關。

並列摘要


The empirical Green’s function (EGF) which approximately corresponds to an impulse response can simply be retrieved from cross-correlation functions of seismic noises between two receivers in the assumption of diffusive wave field. It will increase much more available data than the traditional seismology underlying the view point that the noise is either source or receiver and is known as Passive Imaging Interferometry. In the study, we measure relative velocity variations from the coda part of recovered EGF, observe the temporal evolution, and have discussion on possible mechanisms leading to the changes of physical properties in the crust. The 2006 Mw6.1 Taitung earthquake occurred in the southern Longitudinal Valley and the collision suture zone between the Eurasian plate and the Philippine Sea plate and caused significant coseismic deformation. To detect potential variations in subsurface seismic velocities associated with internal strain change before and after the quake, we construct the GF from auto-correlation function (ACF) and cross-correlation function (CCF) from one-day long seismic noise after normalization. The stacking is applied to produce the long-term GF (Reference GF, RGF) and short-term GF (Current GF, CGF), respectively, for enhancing the coherent phases in EGFs. We use both stretch and moving-window cross-spectrum analysis to detect the relative time shifts of the late-arriving coda waves between CGF and RGF. A sudden drop in relative velocity perturbations is observed in the high –frequency (2-8 Hz) ACFs for the station about 7 km south of the epicenter where the two perpendicular faults may intersect and result in locally maximum coseismic slip deformation and widely-distributed aftershocks. The sustained damage in the regions of fault junction and slip concentration probably cause such a significant velocity disturbance. The CCFs (0.1-0.9 Hz) between pairs of stations also show moderate velocity decrease for the shorter interstation paths traversing the south and southeast of the epicenter, the area subject to the static volumetric strain with coseismic dilatational deformation. Plus, the post-seismic estimation (after October) increase to the pre-seismic value (before April), which shows positive relations between the regional precipitation.

參考文獻


Aki, K., and B. Chouet (1975), Origin of coda waves: source, attenuation, and scattering effects, J. Geophys. Res., 80, 3322-3342
Brenguier, F., M. Campillo, C. Hadziioannou, N. M. Shapiro, R. M. Nadeau, and E. Larose (2008b), Postseismic relaxation along the San Andreas Fault at Parkfield from continuous seismological observations, Science, 321, 1478-1481, doi: 10.1126/science.1160943.
Brenguier, F., N. M. Shapiro, M. Campillo, V. Ferrazzini, Z. Duputel, O. Coutant, and A. Nercessian (2008a), Towards forecasting volcanic eruptions using seismic noise, Nat. Geosci., 1, 126-130, doi: 10.1038/ngeo104.
Campillo, M. (2003), Long-range correlations in the diffuse seismic coda, Science, 299, 547-549, doi: 10.1126/science.1078551.
Chen, C. H., J. Y. Liu, H. Y. Yen, X. Zeng, and Y. H. Yeh (2004), Geomagnetic total field and occurrences of earthquakes in Taiwan, Terr. Atmo. Ocean. Sci., 15, 361-370

被引用紀錄


吳欣玫(2014)。台灣中央山脈地區地震所引起淺層地殼速度與靜態體積應變擾動之相關性〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2014.02122

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