岩浆泡破裂引发地震的模式——以吉林松原2013年地震群为例  

Earthquake Triggered by“Magma Bubble”Bursting:2013 Songyuan Earthquake Cluaters in Jilin as an Example

作　　者：薛林福[1] 祝铭[1] 李文庆[1] 刘文玉 刘正宏[1] 刘泽宇 Xue Linfu;Zhu Ming;Li Wenqing;Liu Wenyu;Liu Zhenghong;Liu Zeyu(College of Earth Sciences,Jilin University,Changchun 130061,China;Wuhan Geological Survey Center,China Geological Survey,Wuhan 430205,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]中国地质调查局武汉地质调查中心,武汉430205

出　　处：《吉林大学学报（地球科学版）》2018年第6期1865-1875,共11页Journal of Jilin University：Earth Science Edition

基　　金：国家地质调查局项目(1212011220247)~~

摘　　要：2013年10月31日,吉林省松原前郭尔罗斯蒙古族自治县(44.60°N,124.18°E)发生震级为5.5级地震,此后的40d内发生了700多次地震,其中5级以上地震5次。松原地区近年来地震活动频繁,2014年1月以来又发生4级以上地震9次、5级以上地震1次,震中处于松辽盆地油气田开采区,地震活动序列十分特殊。为了揭示松原地震的发震机制与发震模式,研究深部地质过程与地震的关系,根据此次实测的通过震中25km长的大地电磁测深剖面,结合地热梯度、He同位素比值(~3 He/~4 He)、CO_2碳同位素、地震序列等资料的综合分析,发现震中地区存在两个位于不同深度的低阻体,地震发生与地幔深部岩浆活动有关;据此提出了一种新的地震发生模式——岩浆泡破裂发震模式,描述了来自地幔的基性岩浆通过向上侵入、在脆-韧性转换带附近聚集形成岩浆泡、岩浆泡破裂及岩浆泡上覆岩层中聚集能量引发岩层破裂产生地震的过程,并使来自地幔的无机成因的CO_2气在储层中形成CO_2气藏。该模式可以解释许多发生在大陆内部地震和深源地震的发生机制。An unusual M 5.5 earthquake occurred on October 31st,2013 in Songyuan City(44.60°N,124.18°E),Northeastern China,and about 700 shocks were recorded in the following 40 days(5 times earthquakes above M 5.0).In the Songyuan area,earthquake activities have been frequent in recent years.Since January 2014,there have been nine times earthquakes with magnitude above 4.0 and one time with magnitude above 5.0.The epicenter is located in the oil-gas exploration area of Songliao basin,and the seismic sequence is very special.In order to reveal the earthquake mechanism,earthquake model and the relationship between deep geological processes and earthquakes,the magnetotelluric(MT)depth sounder was used to record a NW-SE 25-km-long profile with 23 MT survey points across the epicenter.On the basis of the MT profile,geothermal gradient,gas-phase hydrocarbons yield,3 He/4 He ratio,carbon isotope analyses of CO 2 gas and the seismic sequence,two low-resistance bodies were recognized at different depths in the epicentral area.The earthquakes are related to the deep mantle magmatism.We propose a new model that the earthquakes are triggered by“magma bubble”bursting.A“magma bubble”is a magma body formed by gradual accumulation of melts at a certain depth below the surface and rises at a certain speed.Magma gathers into magma bubble near the brittle-ductile transition zone.The energy stores in the magma-bubbles,and the strain energy stores in the overlying strata.Earthquakes occur as a result of the sudden energy release from the magma bubble bursting and the consequent overlying strata fracturing.Deep reservoirs of mantle-derived CO 2 can be formed as a result of such long-term seismic activity.This model can explain the occurrence mechanism of many intraplate and deep-seated earthquakes.

关 键 词：发震模式 岩浆泡破裂 幔源CO2气 大地电磁测深 松原 

分 类 号：P631.4[天文地球—地质矿产勘探]