潮汕沿海地震带三维岩石圈结构与震源构造研究

Coastal Shantou seismic zone is the seismically most active zone in the coast of the south China. Two historic earthquakes with magnitude over 7 hit this area. Earthquakes of small magnitude occur frequently and closely clustered in this area in nowadays, putting the industries and population of the coastal south China in a risk of disastrous earthquake. As an intraplate seismic zone, only research with respects to the seismic geology and study of a deep seismic profile were carried out. Few work regarding three-dimensional (3D) structure and crustal movement survey were performed. This led to the insufficient understanding on the respects of tectonic driving force, seismogenic structure, and risk of potential strong earthquake. This project utilizes the seismic data acquired by a network constituted of a densely-deployed onshore seismometer stations and offshore ocean bottom seismometer (OBS) to perform tomography inversion in order to obtain the 3D velocity model of this area. On this basis, weak zone and its origin will be analyzed. Meanwhile, crustal movement of this area will be studied with global positioning system (GPS) survey, aiming to obtain the crustal deformation feature. Then stress field will be analyzed in combination with focal mechanism solutions. Based on these results, the coupling model between the 3D structure and the stress field will be studied, the reason why this area is seismically active and the seismogenic structure of strong earthquake will be found, and the risk of potential strong earthquake will be evaluated.

潮汕沿海地震带是华南沿海地震最活跃的区域。该区域有历史纪录以来曾发生多次7级强震，而且至今仍然小震频繁密集发生，对华南沿海的经济和社会发展有着现实的地震灾害威胁。作为一个板内地震带，目前对该区只开展了地震地质方面的研究，以及一条主动源的二维剖面研究，而缺少三维深部结构和地壳运动测量等方面的工作。这导致对该地震带的发震机制、震源构造与潜在强震风险等方面的认识存在诸多不确定性。本项目以该区密集的陆上地震台网和海域布放的海底地震仪组成联合观测台阵，利用接收的天然地震波形数据对该区的三维岩石圈结构进行研究，分析其中的构造薄弱带及其成因。同时利用GPS观测对该区的地壳运动进行研究，通过分析该区的地壳运动与地壳变形，并结合震源机制解结果揭示该区的应力场特征。在此基础上分析该区三维结构中的构造薄弱带与区域应力场之间的耦合模式，揭示该区地震活跃的原因，确定强震发生的震源构造，并对潜在的强震风险进行评估。

潮汕沿海地震带是华南沿海地震最活跃的区域。该区域有历史纪录以来曾发生多次7级强震，而且至今仍然小震频繁密集发生，对华南沿海的经济和社会发展有着现实的地震灾害威胁。本项目以该区密集的陆上地震台网和海域布放的海底地震仪组成联合观测台阵，利用接收的天然地震波形数据对该区的三维岩石圈结构进行研究，分析其中的构造薄弱带及其成因。同时利用GPS观测对该区的地壳运动进行研究，通过分析该区的地壳运动与地壳变形，并结合震源机制解结果揭示该区的应力场特征。通过本项目的实施，（1）揭示了潮汕沿海的发震构造特征；（2）获得了广东省及周边区域的相对地壳运动信息；（3）潮汕沿海地震带的b-value分布特征；（4）获得了南澳外海地震震源区三维地壳结构。本项目研究认为，潮汕沿海地震的发生与研究区域内的上侵高速体和中地壳低速带有着紧密的耦合关系。另外，该研究地壳运动信息和b-value分布的获取，为今后开展地壳稳定性评价提供了科学依据。