理學院: 海洋研究所指導教授: 張翠玉; 雷蒂夏鄭厚昇Cheng, Hou-ShengHou-ShengCheng2017-03-032018-06-282017-03-032018-06-282016http://ntur.lib.ntu.edu.tw//handle/246246/274085花東縱谷是菲律賓海板塊及歐亞板塊的縫合帶，在縱谷的北端是板塊間碰撞及菲律賓海板塊向歐亞板塊隱沒的交接點，在此處觀察到密集的地震活動。根據中央氣象局地震目錄，在1990至2012年間花東縱谷北段有四個明顯的地震序列，我們針對其中兩個有明顯餘震活動的地震序列來了解在板塊擠壓下的破裂行為，分別是發生在1990年12月13日的雙主震 (ML 6.5和6.7) 和在2012年6月14日主震規模ML 5.3的地震序列，位置重疊於1990年地震序列的南段，可能是同一段層面的重複破裂。1990年地震序列所使用的資料是主震發生後三天所部署的花蓮臨時地震測站網，共有15個加速度型地震測站紀錄震後約兩個月間所發生的餘震事件，而在2012年資料來自中央氣象局地球物理資料管理系統的自由場強震觀測網所記錄到約1個月的餘震事件。 我們通過近場站所記錄到在1990年地震序列和2012年地震序列中的50個和37個中小型規模地震事件 (ML 2.5-5.0) 透過FMNEAR的修改版本以點震源模式來做波形反演，並透過兩階段格點搜尋法來解算震源機制解參數，且利用震源深度調整及給定每個測站的一維速度模式進行波形優化，FMNEAR的修改版本已被證明能夠有效的利用數量有限的地震測站解算中小型規模地震的震源機制解。 對於這兩個地震序列，解算的震源深度平均比中央氣象局地震目錄還要深10公里。我們根據發震機制和P- 和T- 軸方向，將所得1990年和2012年地震序列的震源機制解各分為三組。兩個地震序列分別有一組震源機制解與主震相似且皆為逆衝斷層，這組事件較多，震源機制解其中一個破裂面與花東縱谷的走向平行，呈現向東傾的破裂面，為1990年及2012年地震序列的主要破裂行為，而其它組則顯示與縱谷主要逆衝走向不同的斷層分支。我們透過觀察兩個地震序列的破裂行為結論出縱谷斷層北段，有斷層分段及地震活動度的變化，本研究的結果顯示在板塊聚合邊緣不同發震機制的斷層系統，其時間跟空間的關係。The Longitudinal Valley (LV) is the suture zone between the Eurasian plate (EUP) and the Philippine Sea plate (PSP). The northern tip of the LV (near Hualien city) is the junction point where the collision evolves northward to a subduction of the PSP under the EUP. As a result, a high seismic activity is observed along the LV. In the northern tip of the LV, we identified four distinct seismic clusters since 1990 based on the Central Weather Bureau (CWB). We restrict our effort on two of them that distributed on most of the northern part of the LV. The first seismic crisis is triggered by a doublet of events (ML 6.5 and 6.7) on 13rd December, 1990, and the second crisis occurs in 2012 with a main shock of ML 5.3 on 14th June. The 2012 seismic crisis may be re-activated at the southern segment of the 1990 earthquake sequence. For the seismic crisis in 1990, a campaign seismic network of 15 accelerometers – the Hualien Temporary Seismic Network (HTSN) is deployed 3 days after the first main shock during 2 months to detect the aftershocks. For the seismic crisis in 2012, the data set is recorded by Free Field Strong Earthquake Observation Network from Geophysical Database Management System, CWB. We retrieved focal mechanism solutions (FMS) of 50 aftershocks in 1990 and 37 earthquakes in 2012 with local magnitude ranging from 2.5 to 5.0 by waveform inversion using the near-field component of seismic waveforms. A modified version of the Program FMNEAR is adopted in this study. In this method, a double grid-search is applied upon determining FMS parameters while rake value is lately tuned by a simulated annealing algorithm. Waveform adjustments are improved by depth optimization and a specific 1D velocity model for each station. A modified version of the FMNEAR has been proven efficiently to retrieve FMS for the small-to-moderate earthquakes with a limited number of stations. For both of the earthquake sequences, focal depths are in average 10 km deeper than the depth provided by the CWB catalog. Both FMS from 1990 and 2012 clusters can be classified into three groups according to their mechanisms and P- and T-axis. The main groups (with a higher number of events) display homogeneous FMS, mostly reverse in type that we believe illustrate the behavior of the main-fault that generate both the doublet of 1990 and the 2012 events. FMS of these main group displays a similar strike as the valley and one of the nodal planes dip eastward as the plate boundary between the EUP and the PSP. For the other groups, show variety amongst FMS, are the fault branches of the main-fault. We conclude that the Longitudinal Valley Fault, the effective plate boundary, displays a variety FMS came from additional fault systems from North to South despite its segmentation and variation of activity.214874972 bytesapplication/pdf論文公開時間: 2017/7/4論文使用權限: 同意有償授權(權利金給回饋學校)花蓮花東縱谷震源機制解地震序列近場波波形反演HualienLongitudinal ValleyFocal mechanism solutionEarthquake sequenceNear-field waveform inversionthesis10.6342/NTU201600438http://ntur.lib.ntu.edu.tw/bitstream/246246/274085/1/ntu-105-R03241301-1.pdf