CHARACTERISTICS OF EARTHQUAKE CLUSTER ACTIVITY IN TENGCHONG VOLCANIC AREA
CHARACTERISTICS OF EARTHQUAKE CLUSTER ACTIVITY IN TENGCHONG VOLCANIC AREA
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发表时间：
2003
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通讯作者：
Ye Jian-qing
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作者：
Ye Jian-qing
从腾冲火山区移动的数字地震台网1998、1999和2002年的观测资料中，选取了30个与岩浆活动有关的地震事件。这些事件主要集中在集群中发生。根据地震群的时空分布、地震波特征、震源参数和震源机制，分析了火山地震群活动与岩浆房位置的关系。特定事件的S波记录异常表明腾冲南部火山区下方存在岩浆体或岩浆通道;震源机制解表明，发震应力方向与区域构造应力方向有较好的对应关系。地震裂缝以水平走滑为主，但部分地震裂缝表现出较大的倾滑分量。推测火山地震群是在区域构造应力作用下，热介质活动导致岩浆房附近围岩剪切破裂的结果。研究表明，腾冲火山区存在两个岩浆体，一个位于2 5 0°~ 2 5 1°N，98 42°~98 48°E，埋深4~ 6 km;另一个位于2 4 9°~ 2 5 0 5 °N，98 45°~98 55°E，埋深8~ 14 km。地震活动主要在岩浆体周围，与岩浆活动密切相关。岩浆体控制着腾冲火山区的地热活动和微破裂。
Thirty seismic events related to magmatic activities have been selected from observation data of the mobile digital seismic network disposed in Tengchong volcanic area in 1998, 1999 and 2002. These selected events mainly occurred in cluster. The relations between the activities of volcanic earthquake clusters and the locations of magma chambers are analyzed on the basis of space-time-magnitude distributions of earthquake clusters, seismic wave characteristics, focal parameters and focal mechanisms. The anomalies of S wave records of specific event show that there are magma bodies or magma channels beneath the southern Tengchong volcanic area; focal mechanisms display that the orientation of earthquake-generating stress corresponds well with that of the regional tectonic stress. Seismic fractures are dominated mainly by horizontal strike-slip, but some seismic fractures display relatively large dip-slip components. It is inferred that the volcanic earthquake clusters are the results of shear-fracturing of the wall rocks in the vicinity of the magma chamber caused by the activities of heat medium under the action of regional tectonic stress. This study shows there are two magma bodies beneath Tengchong volcanic area: one is located at 25 0°～25 1°N, 98 42°～98 48°E and 4～6km depth, the other is located at 24 9°～25 05°N, 98 45°～98 55°E and 8～14km depth. The activities of earthquakes are mainly around the magma bodies and greatly related to magmatic activities. Magma bodies control the geothermal activity and micro-fracturing in Tengchong volcanic area.