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Detection and localization of acoustic signals from fluid ascent channels near CO2 degassing sites in the Cheb basin (West-Bohemia)

切布盆地（西波希米亚）二氧化碳脱气点附近流体上升通道的声学信号的检测和定位

基本信息

批准号：
252784381
负责人：
Professor Dr. Michael Korn
金额：
--
依托单位：
Institut für Erdsystemwissenschaft und Fernerkundung
依托单位国家：
德国
项目类别：
Infrastructure Priority Programmes
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/252784381?language=en
关键词：
Detection localization acoustic signals fluid

项目摘要

The West Bohemia/Vogtland region is a place of presently ongoing geodynamic processes which result in the occurrence of repeated earthquake swarms, mantle-derived fluid exhalations, mofettes, among others. The PIER-ICDP (Probing of intra-continental magmatic activity: drilling the Eger Rift) initiative aims at establishing a scientific drilling program in that region to create an observatory at depth for the long-term study of earthquake swarms and related phenomena. Most of the seismicity is released at the Novy Kostel epicentral area at depths below 6 km, the main fluid escapement centers at the surface, however, are located in the Cheb basin, some 10 km to the south. Fluid migration paths in between are unknown. Gas flux at the surface is partly concentrated in wet or dry mofettes, but another part is more diffusive. Hypotheses are that fluids preferably migrate along existing faults in the crystalline basement and more diffusive flow takes place in the sedimentary cover of the Cheb basin. It is well known from volcanic and geothermal areas that fluid flow acts as permanent source of seismic vibrations. Detecting and locating these sources can therefore help to delineate more precisely the conduit paths of upwelling fluids and to pin down preferred places for drill holes as monitoring sites. We have successfully tested the Matched Field Processing (MFP) method to localize continuous seismic noise sources in the mofette fields of South Hartousov and Dolní Cástkov in the Cheb basin with the help of small seismic array deployments, and obtained source images within a subsurface volume of several 10 m edge length. Now, we will extend the data acquisition to more mofette sites, and will do repeated measurements at one site to search for time variations in the degassing strength and location of fluid pathways. We will also increase the aperture of the arrays to obtain mages of larger subsurface volumes. The data acquisition and analysis will be complemented by enhancements of the MFP method, and by numerical modelling to synthetically study the resolution power and uncertainties of the imaging process. The detailed imaging of fluid ascent paths down to several 100m depth, together with their correlation with seismic and conductivity structures as well as lithology will be of great benefit for the selection of drill sites for establishing a long-term monitoring laboratory within the fram of ICDP.

西波希米亚/沃格特兰地区目前正在发生地球动力学过程，导致反复发生地震群、地幔流体喷出、莫菲特等。 PIER-ICDP（大陆内岩浆活动探测：埃格尔裂谷钻探）计划旨在在该地区建立科学钻探计划，建立一个深度观测站，用于长期研究地震群和相关现象。大部分地震活动发生在新科斯特震中区，深度低于 6 公里，但地表的主要流体逃逸中心位于以南约 10 公里的切布盆地。两者之间的流体迁移路径未知。表面的气体通量部分集中在湿或干莫菲特中，但另一部分则更加扩散。假设流体优选沿着结晶基底中的现有断层迁移，并且在切布盆地的沉积盖层中发生更多的扩散流。众所周知，火山和地热地区的流体流动是地震振动的永久来源。因此，检测和定位这些源可以帮助更精确地描绘上升流体的管道路径，并确定钻孔的首选位置作为监测点。我们成功测试了匹配场处理（MFP）方法，借助小型地震台阵部署，对切布盆地南哈尔图索夫和多尼卡斯特科夫莫菲特场进行连续地震噪声源定位，并在数个10 m边长的地下体积内获得了源图像。现在，我们将把数据采集扩展到更多的mofette地点，并在一个地点进行重复测量，以寻找脱气强度和流体路径位置的时间变化。我们还将增加阵列的孔径以获得更大地下体积的图像。数据采集和分析将通过增强MFP方法来补充，并通过数值建模来综合研究成像过程的分辨率和不确定性。深至数百米深度的流体上升路径的详细成像，及其与地震和电导结构以及岩性的相关性，对于在ICDP框架内建立长期监测实验室的钻探地点的选择将大有裨益。