2016年2月6日3點57分26秒(當地時間GMT+8)發生高雄美濃地震，震央位在高雄市美濃區，深度為14.6 km，芮氏規模為6.6，最大震度7級位在台南新化、左鎮一帶，造成多處房屋倒塌及117人死亡，是繼921大地震後，傷亡最嚴重的地震。我們收集距離震央40 km以內的17個連續記錄的地震測站，採用每兩個測站的環境噪訊計算其交互相關函數(cross-correlation function, CCF)，透過三年的資料疊加，建立兩站之間的經驗格林函數(empirical Green's function, EGF)，應用在估算地震波波速的變化以及三維速度模型。
我們計算17個測站共136對每日的CCF與參考相關函數(reference correlation function, REF)的時間延遲，在2014至2016三年內，從0.01 Hz至2 Hz共分析6個頻帶，得到相對地震波波速變化，再利用曲線擬合方程式，估算同震(co-seismic)速度變化量，發現在新化斷層以北以及距震央20 km西側分別有約0.463%及0.206%的速度下降量，在震後恢復(post-seismic recovery)上，前者波速並未恢復至震前(pre-seismic)速度，而後者在6個月內恢復至震前值。將兩站之間的EGF，採用環境噪訊層析成像法(ambient noise tomography)，得到三維剪切波速度模型，結果顯示，在新化斷層以北，S波波速呈現相對高速，對應到古地壘構造(佳里古脊)，而S波低速區分佈在高屏平原，對應到由西南外海延伸至陸地的泥貫入體(mud diapir)及泥火山(mud volcano)。
從震後6個月的GPS位移場來看，在新化斷層以南，朝西南向位移約30 mm，但新化斷層以北卻無顯著的震後位移量，將GPS觀測量與波速變化、速度構造及震測剖面綜觀討論下，新化斷層鄰近台南盆地與泥質陸棚的邊界，新化以北的高速帶可對應到佳里古脊，南段的塊體則位在大陸斜坡上。我們認為由地震造成的強烈地表晃動，使得同震波速下降，是由於鬆軟的土質受到強烈晃動後，液壓增加，其岩體間的孔隙率及透水性上升、既有的裂隙被擴張，使得震波波速下降。新化以南較短時間的震後波速恢復，是由於南段塊體的推擠，使得應力上升與微小破裂的癒合，岩體透水性下降，達成震波波速回升。由此推論，新化斷層扮演著屏障的角色，阻擋美濃地震震後滑移向北的延伸。

The 6 February 2016 Mw 6.5 Meinong earthquake with a focal depth of 14.6 km produced widespread strong shaking in the 30-km-away Tainan city and caused about 10 buildings collapsed and 117 death. We collected seismic waveforms from 17 broadband stations within 40 km epicentral distances and reconstruct the Green’s functions from cross-correlation function of ambient seismic noise between two stations. We analyzed seismic data for six different frequency ranges from 0.01 to 2 Hz, which yielded time series for different station pairs from January 2014 to December 2016. We found coseismic velocity drops of about 0.463% mostly in 0.5 to 1 Hz at the north of the Hsinhua fault and 0.206% at the south part, however postseismic velocity variation differs between these two regions. The time series of velocity change presented a non-recovery trend at the north area, however the south region is indicated by a recovering trend three months after the Meinong earthquake. For the surface wave tomography results in southwestern Taiwan, the regional geological structures are recognizable in the estimated phase-velocity dispersion maps. The 3D velocity model displays low velocity in the alluvial plain, but indicates high velocity in the north of the Hsinhua fault. During the six months of the postseismic period, based on the GPS observations in the Hsinhua fault area, the block south of the fault continuously moved ~30 mm along the southwest direction while the north of the fault remained stationary. The Hsinhua fault is located near the boundary between the Tainan basin and the muddy continental shelf, and where the block south of the fault is on the continental slope. We suggest that the coseismic velocity drop was caused by the earthquake shaking in the soft deposited materials with increase of permeability, corresponding to soil liquefaction. The shorter recovery time and thus velocity increase in the block south of the Hsinhua fault was resulted from the afterslip of the Meinong earthquake, which resulted in the stress increases and the closure of the micro-fracture. Apparently, the Hsinhua fault acts as a barrier blocked the afterslip south of the fault.

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