意大利埃特纳火山的三维速度结构与地震活动性

Three Dimensional Velocity Structure and Seismicity of Etna Volcano, Italy

本文的研究工作，得到了埃特纳火山下面的一组新的三维速度模型。作者们用１９８０年以来地方性地震在永久和临时地震台网在４个或更多台记录到的１２４９次地震的Ｐ和Ｓ波，被选来作走时反演。选择了几种判别标志与参数化办法以显示其类似的基本特征。表明在火山的东南象限在浅层，有Ｐ波的高速分怖，它同布格重力高异常有密切关系。在该区存在低的Ｖｐ／Ｖｓ比值；沿着中央火山管道，分布有高速Ｐ波和高的Ｖｐ／Ｖｓ比值；建议该处存在有稠密的侵入的岩浆体，延伸到２０千米左右的深度，该区附近有低速的Ｐ波速度。对震源的重新定位也显示出向外倾斜的易碎区，与中央火山管道延伸出一段Ｐ波高速异常区，位于中央火山口的附近。沿着中央火山口附近，有Ｐ波的低速区，它同次生的火山锥的分布有关，与部份熔融的深部岩浆库有联系。

A new set of three dimensional velocity models beneath Etna volcano is derived in the present work. We have used P and S wave arrivals from local earthquakes recorded at permanent and temporary seismic networks installed since 1980.A set of 1,249 earthquakes recorded at more than 4 seismic stations was selected for travel time inversion. The velocity models obtained by using different data selection criteria and parametrization display similar basic features,showing a high P wave velocity at shallow depth in the SE quadrant, in close connection with a high gravimetric Bouguer anomaly. This area share a low Vp/Vs ratio.High P wave velocities and high Vp/Vs ratios are obtained along the central conduits,suggesting the presence of dense,intrusive magmatic bodies extending to a depth of about 20 km.This region is surrounded by lower P wave velocities.The relocated earthquake hypocenters also display the presence of outward dipping brittle region,away from the central conduite, surrounding a ductile zone spatially related to the high P wave velocity anomalies located in the proximity of central craters.The distribution of parasitic cones, suggesting the location of partial meltlinked to deep magmatic reservoirs.