台湾台东外海“ V”字形地震震源带问题刍议

A DISCUSSION ON THE 'V-SHAPED' FOCAL ZONE BENEATH THE OUTSIDE SEA OF TAIDONG, TAIWAN

根据震源深度的分布,在台湾台东县东南部海域,即东经120°—120°30′、北纬22°—23°范围,存在一个“V”字形地震震源带底面.这种特异构造,引发了一系列强震,造成花莲以外另一个强震集中区,同时形成了台湾地区为数不多的中源地震(深度70—170km)区.“V”字震源在平面上的特征是:中源地震的震源等深度线呈南北走向的三个同心椭圆圈闭;而剖面特征显示震源带的底界面为“V”字形形态.震源倾斜的方向关系到对未来震害的预测,作者根据台东地区的震源主要向外倾斜,即向东倾斜,震中大多位于远离陆地的海上,再结合台东人口较少,基本没有大型建设项目,认为可不列为防震减灾的重点地区.

Based on the distribution of focal depths, there is a 'v - shaped'focal zone bottom beneath southeastern sea area of Taidong county, Taiwan, that is, in the area of 123°30- 123°00E, 22° -23°N. Such kind of particular structure caused a series of strong earthquakes, forming another concentration area of strong earthquakes besides Hualian, and formed an intermediate focus (70-170km deep) area which is race in Taiwan Region.The characteristics of the 'v -shaped' focal zone in plane are that the focal isobaths of intermediate focus earthquakes form three SN striking oval traps at the same center, and its sectional characteristics show that the bottom of the focal zone is a 'v - shape'.The direction of focal dip affects prediction of future earthquake disasters. Basing on that foci in Taidong area are dip to outside principally, that is, to the east, so the epicenters mainly lie on the sea area, that is distant from the land.Combining with small population and race large construction projects, authors think that it can be classified as anon -priority arsa of earthquake prevention and disaster reduction.