科研之友
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摘要
On 2016 February 6 the South Taiwan earthquake (M-w 6.4) occurred in the Meinong District of Kaohsiung, southern Taiwan, at a depth of 17 km. It caused 117 fatalities and widespread damage to infrastructures, especially in the Tainan city. To clarify the generating mechanism of this damaging earthquake, we determined high-resolution 3-D images of P- and S-wave velocity (V-P, V-S) and Poisson's ratio (sigma) in the epicentral area. We used 105 712 P-and 61 250 S-wave arrival times of 8279 local earthquakes (1.5 <= M <= 6.4) recorded at 41 seismic stations in South Taiwan during 2000-2011. In the upper crust (depth <= 10 km), the most remarkable feature is low-VP, low-VS and high-s anomalies in areas with known active faults in the southwestern and easternmost parts of Taiwan. In contrast, high-VP, high-VS and low-s anomalies become dominant in the lower crust. The hypocentre of the 2016 South Taiwan earthquake is located in a boundary zone where seismic velocity and Poisson's ratio change drastically in both the horizontal and vertical directions. Furthermore, the hypocentre is underlain by a vertically elongated high-s anomaly at depths of 23-40 km, which may reflect ascending fluids from the upper (or uppermost) mantle. The low-V and high-sigma anomalies in the upper crust coincide with areas of low heat flow, negative Bouguer gravity anomaly, and low magnetotelluric resistivity, which may reflect crustal fluids contained in the young fold-and-thrust belt. These results suggest that the 2016 South Taiwan earthquake was triggered by ascending fluids from dehydration of the subducting Eurasian slab, invading into active faults with a high loading rate.
- 出版日期2016-10
