探究2023年2月6日土耳其7.8级双震的成因

doi:10.12196/j.issn.1000-3274.2024.03.001

摘要/Abstract

摘要： 为了促进地震预测和揭示地震成因奥秘, 依据地壳结构、地震地质、地球物理、地热流体地球化学资料和地震序列发生的时空特征, 综合研究了2023年2月6日土耳其南部7.8级双震的成因。 2023年2月6—17日土耳其南部发生7.8级双震, 伴随了几十次M≥5.0强余震和数千次M<5.0的余震。地震震源深度分布范围为5~22 km, 在大约500 km×300 km的范围内震中分布形成一条NE向、宽约40 km、长约300 km和另一条近EW向、宽约50 km、长约240 km的震中分布密集带。研究区下存在地壳内的低速高导层, 大地热流密度高值异常, 布格重力负异常、航磁异常以及深大断裂带, 表明该区岩石圈内存在地幔流体聚集、形成超高压流体的条件。地幔流体局部聚集形成超高压流体的过程可视为孕震过程。 2023年2月6—17日不同时段的地震震源空间分布的阶段性集中和深度变化表明, 地幔高能密流体的持续供给或者供给量增大形成了孕震体。当孕震体内流体压力大于围岩束缚强度(围岩抗压强度+静水压力)时发生流体隐爆, 产生地震。流体通过运移—聚集—爆炸—运移—聚集—爆炸……的循环方式运移, 同时产生7.8级双震及其余震。这从能量来源和产生地震波的角度较合理地解释了在有限的范围内非连续、非弹性地体中连续产生7.8级双震和M≥4.0余震的现象。

关键词: 7.8级双震, 隐爆作用, 地幔流体, 地热流体孕震, 地震成因, 土耳其

Abstract: Generation of the double M_S7.8 earthquakes of 6 February 2023 in southern Türkiye was comprehensively studied based on the crust structure and seismogeologic, geophysical and geothermal fluid geochemistry data as well as the spatial-temporal characteristics of the seismic sequence occurrences, in order to improve earthquake prediction and earthquake generation research. The double M7.8 earthquakes took place on 6 February 2023 in southern Türkiye, companying dozens of M≥5.0 earthquakes and several thousands of M<5.0 aftershocks in the duration of 6—17 February. Depths of the earthquakes focus range from 5 km to 22 km. The earthquake epicenters predominantly distributed in two belts in an area of about 500 km×300 km. One belt of NE trending has a length of 300 km and width of 40 km, another belt of EW trending has a length of 240 km and width of 50 km. Existences of low velocity and resistivity zone in the crust, high heat flow anomaly, negative Bouguer gravity anomaly, aeromagnetic anomaly and the deep-cut fault zones in the study area indicate that there are the necessary requirements for mantle-derived fluid accumulation and formation of super-pressure fluid bodies in the lithosphere of the area. The process of locally mantle-derived fluid accumulation to build super-pressure fluid bodies can be considered as the process of seismogenesis. The periodical accumulation of earthquake hypocenters in space and variations of the hypocenter depths during 6—17 February indicated that increasing supplement of high-energy-density fluids derived from the mantle to the earthquake source bodies, resulted in repeated increases of fluid pressure. Cryptoexplosion occurred when the fluid pressure in the source bodies exceeded the strength of the surrounding rocks (compressive strength + hydrostatic pressure), producing earthquakes. The high-energy-density fluids migrated in the way of the inflate-explosion-deflate-inflate-explosion-deflate cycle, which produced the M7.8 double earthquakes and aftershocks. Therefore, the M7.8 double earthquakes and M≥4.0 aftershocks occurring in the discontinuous inelastic source bodies in the small region can be reasonably explained from the view of energy source and seismogenesis of geothermal fluid explosion.

Key words: Double M7.8 earthquakes, Cryptoexplosion, Mantle-derived fluids, Seismopregnant process of geothermal fluids, Seismogenesis, Türkiye

中图分类号:

P594.1

郭贵娟, 孙凤霞, 杜建国. 探究2023年2月6日土耳其7.8级双震的成因[J]. 地震, 2024, 44(3): 1-20.

GUO Gui-juan, SUN Feng-xia, DU Jian-guo. Investigating Generation of the February 6, 2023 M7.8 Double Earthquakes in Türkiye[J]. EARTHQUAKE, 2024, 44(3): 1-20.

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