用地震走时反演计算长白山天池火山区二维地壳泊松比  

2-D CRUSTAL POISSON′S RATIO FROM SEISMIC TRAVEL TIME INVERSION IN CHANGBAISHAN TIANCHI VOLCANIC REGION

作　　者：刘志[1] 张先康[1] 王夫运[1] 段永红[1] 赖晓玲[1] 

机构地区：[1]中国地震局地球物理勘探中心,中国郑州450002

出　　处：《地震学报》2005年第3期324-331,共8页Acta Seismologica Sinica

基　　金：中国地震局"九五"重点项目(95110201);科技部社会公益专项资金项目(2001DIA10003)资助

摘　　要：尝试应用一种同时获得地壳二维速度结构和界面形态的地震走时反演算法,通过分别反演P波和S波速度结构,计算深地震测深剖面的泊松比分布的方法,并对长白山天池火山区测深剖面(L1)进行处理解释.计算表明,该方法克服了传统基于正演计算方法的诸多缺陷,是计算测深剖面泊松比分布的行之有效的方法,特别是在对火山岩浆系统及地壳断裂带研究中具有重要意义.研究结果显示,天池火山口下的地壳低速体内有一宽约30km、高约12km的高泊松比异常区,其泊松比值高于周围介质8%左右,应为高温熔融岩石介质,即岩浆囊.在其上方直至上地壳顶部有一高泊松比条带,代表了热物质上移的通道.在其下部高泊松比区域,局部深达莫霍面形成了地幔热物质底侵的可能通道.三维台阵观测的层析成像和大地电磁测深研究结果均与上述结论相印证.Based on the inversion method of 2-D velocity structure and interface, the crustal velocity structures of P-wave and S-wave along the profile L_1 are determined simultaneously with deep seismic sounding data in Changbaishan Tianchi volcanic region, and then its Poisson′s ratio is obtained. Calculated results show that this technique overcomes some defects of traditional forward calculation method, and it is also very effective to determine Poisson′s ratio distribution of deep seismic sounding profile, especially useful for study on volcanic magma and crustal fault zone. Study result indicates that there is an abnormally high Poisson′s ratio body that is about 30 km wide and 12 km high in the low velocity region under Tianchi crater. Its value of Poisson′s ratio is 8% higher than that of surrounding medium and it should be the magma chamber formed from melted rock with high temperature. There is a high Poisson′s ratio zone ranging from magma chamber to the top of crust, which may be the uprise passage of hot substance. The lower part with high Poisson′s ratio, which stretches downward to Moho, is possibly the extrusion way of hot substance from the uppermost mantle. The conclusions above are consistent with the study results of both tomographic determination of 3-D crustal structure and magnetotelluric survey in this region.

关 键 词：地震走时反演 S波 长白山天池火山 岩浆囊 

分 类 号：P313.2[天文地球—固体地球物理学]