【摘要】 利用长白山天池火山区三维空间深地震测深观测系统所采集的反射P波走时资料 ,采用层析成像技术 ,重建了该区地壳界面构造形态和速度分布图像 .界面成像结果表明 :研究区地壳界面总体上显示了由北西向东南加深的趋势 ;马鞍山—三道白河断裂和富尔河—红旗河断裂是本区两条主要的深部构造 ,尤其是马鞍山—三道白河断裂 ,北北东向穿越天池火山口 ,其两侧的地壳界面存在明显的错断 ,预示了该处地壳厚度陡变带或深大断裂带的存在 .速度成像结果显示在 10km深度 ,明显的P波低速异常分布在天池周围 ;15km深度上它表现为一个近南北向的P波低速异常条带 ,其延展尺度南北向为 80～ 90km ,东西向 30～ 4 0km ;随着深度的增加 ,P波低速异常分布在天池西侧 ,其尺度有明显的缩小 ,分布范围更加集中 ,而且低速扰动幅度更大 .这种P波速度异常的变化图像在一定程度上反映了天池火山口下方壳内岩浆系统的空间分布状况 .更多还原

【Abstract】 Using reflection traveltimes of P wave from the 3-D spatial deep seismic sounding experiment carried out in the Changbai—Tianchi volcanic region, we have reconstructed 3-D crustal interfaces and crustal velocity distribution images by the seismic tomography technique. The interface images show that the crustal depth increases from NW to SE in general. The Ma’anshan—Sandaobaihe and Fu’erhe-Hongqihe faults are two main deep structures of this region, especially in both sides of Ma’anshan—Sandaobaihe fault, where the change of crustal thickness is obvious, implying there is a crustal thickness variation belt or deep crustal fault at this position. The velocity images show that an obvious low-velocity anomaly of P-wave exists around the Tianchi at the depth of 10 km. It becomes a low-velocity anomalous strip of nearly SN direction at the 15 km depth, which extends about 80～90km in NS direction and 30～40km in EW direction. With the increase of depth, the low-velocity anomalous strip is distributed on the west side of the Tianchi, but with a smaller scale, and it distributes more concentrated and presents higher perturbation. This change image of the P-wave velocity anomaly illustrates the spatial distribution state of the magma system under the Tianchi volcano to certain extent.更多还原