阿德朗达克-西魁北克地震带地壳三维速度结构成像

根据在阿德朗达克-西魁北克地震带及其邻近地区的59台短周期数字地震仪记录的直达P波走时观测值,用地震层析成像方法反演了该地区地壳三维速度结构.结果表明,地壳上层（0-5km）在阿德朗达克穹隆山的中南部地区出现正速度异常;第二层（5-10km）及第三层（10-15km）的速度横向变化较小,介质相对比较均匀;第四层（15-25km）出现显著的速度异常,一个是位于地震带中部的正速度异常（+4％）,它与布格重力正异常一致;另一个是位于阿德朗达克穹隆山下的负速度异常（-4％）.结合已有的地质及地球物理资料进行对比,可以认为阿德朗达克是一个正在发展的穹隆上升山,但其热源前锋尚未到达地面的大陆热点.

IMAGING THREE DIMENSIONAL CRUSTAL VELOCITY STRUCTURE ALONG THE ADIRONDACK-WESTERN QUEBEC SEISMIC ZONE

Based on seismic tomographic technique, the three dimensional crustal velocity structure has been inverted along the Adirondack-western Quebec seismic zone, the data of the first P arrival from local earthquakes are collected from 59 shortperiod digital seismographic stations which located in the seismic zone and its adjacent area.The results of invertion indicate that the positive velocity anomaly is appeared in the first layer of the crust (0-5km in depth); and the velocity varies weakly showing lateral homogeneous relatively in the second layer (5-10 km) and the third layer (10-15km); and the contemporary anomalous velocity structure has found in the fourth layer (15-25 km), in which positive velocity anomaly ( + 4%) is coincided with the centre of the Bouguer gravity positive anomaly, and a negative velocity anomaly ( - 4%) is beneath the mid-south part of Adirondack uplift. Comparing with the geological and geophysical evidences the Adirondack mountain can be explained an undergoing domical uplift and hot spot as the mechanism of doming but the front of the thermal pulse has not arrived at surface in the continent.