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Study of prediction of volcanic eruptions at Taal, Philippine

菲律宾塔尔火山喷发预测研究

基本信息

批准号：
05041062
负责人：
ANDO Masataka
金额：
$ 6.4万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05041062/
关键词：
The Philippines Taal volcano Seismic exploration Magma chamber Regional stress field Volcanic eruption Artificial seismic source Seismi arvay observation 人工地震探査カルデラ反射面溶融体レシーバー関数地下構造

项目摘要

Taal Volcano is strato-volcano which is composed of a 15*22km^2north-south trending caldera lake and a volcanic island with extent of about 5*5km^2 centered in the lake and known as one of the most active volcanoes in Philippines, though no eruption has occured since 1977. We carried out seismic explosion surveys two times, for the first time in Philippines, at Taal Volcano. In March, 1993, two explosions were executed on the west shore of the caldera lake and seismic waves that passed beneath the volcano were recorded by 30 digital event recorders installed on the east shore along the fan-shooting survey line. Next, in February, 1994, one explosion was made on southeast shore and wave signals were recorded by 27 event recorders on the west to north shore. We noticed significant differences between the seismic waves that passed just below the main crater and those traveled outside of the crater. The former waves attenuate more strongly and propagate more slowly than the latter waves, a … More nd the former waves are followed by reflected phases with large amplitude which show faster apparent velocity than initial P arrivals. The P velocity structure is derived from the direct and refracted P waves that passed outside of the main crater by using the time-term method. The result is as follows ; the surface layr, 1.8 km/s with thickness of 0.1 to 1km, the second layr, 3.6km/s with thickness of 0.3 to 2km, and the third layr, 5.6km/s. The delay of P arrivals that passed beneath the main crater is 0.2 to 0.4sec, which cannot be explained in terms of the time-terms beneath the stations. These results show the existence of low-velocity and low-Q region at about 2 km depth and the region is located within the horizontal extent of 2*2km^2 and about 5 km east of the main crater by the two surveys. The result of normal-moveout-correction shows that the reflection phases mentioned above come from about 7 km depth and 5 km east of the main crater. This reflector may suggest the top surface of magma chamber, and in this case, the low-velocity and low-Q zone should be restricted only shallower part of the third layr because of large amplitude of the reflected phases. Less

塔尔火山是一座层状火山，由一个15* 22平方公里的南北走向的破火山湖和一个以湖为中心的面积约5* 5平方公里的火山岛组成，是菲律宾最活跃的火山之一，但自1977年以来没有发生过喷发。我们进行了两次地震爆炸调查，第一次是在菲律宾的塔尔火山。1993年3月，在破火山口湖的西海岸进行了两次爆炸，通过火山下面的地震波被安装在东海岸沿着扇形发射测量线的30个数字事件记录仪记录下来。1994年2月，在东南海岸发生了一次爆炸，西至北岸的27个事件记录仪记录到了波浪信号。我们注意到在主火山口下方通过的地震波和在火山口外部传播的地震波之间存在显着差异。前一种波比后一种波衰减更强，传播更慢， ...更多信息前一波之后是振幅较大的反射波相，其视速度比P波初至快。用时间项方法，由主火山口外的直达波和折射波得到了P波速度结构。结果如下：第二层为3.6km/s，厚度为0.3 ~ 2km;第三层为5.6km/s。P波到达主陨坑下方的延迟为0.2 ~ 0.4秒，这不能用测站下方的时间项来解释。结果表明，在约2 km深度处存在低速低Q区，该区域位于2* 2 km^2的水平范围内，距离主撞击坑以东约5 km。动校正结果表明，上述反射波相位来自主火山口以东约5 km处的7 km深度。这种反射层可能代表岩浆房的顶面，在这种情况下，由于反射相位振幅较大，低速低Q带应仅限于第三层的较浅部分。少