| 青藏高原东缘地震活动与居里点深度之间的相关性 |
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| 引用本文： | 王健,张广伟,李春峰,梁姗姗.青藏高原东缘地震活动与居里点深度之间的相关性[J].地球物理学报,2018,61(5):1840-1852. |
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| 作者姓名： | 王健 张广伟 李春峰 梁姗姗 |
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| 作者单位： | 1. 中国地震局地壳应力研究所(地壳动力学重点实验室), 北京 100085;2. 浙江大学海洋科学系, 浙江舟山 316021;3. 青岛海洋科学与技术国家实验室海洋矿产资源评价与探测技术功能实验室, 山东青岛 266237;4. 中国地震台网中心, 北京 100045 |
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| 基金项目： | 国家自然科学基金（41704086，41776057）和中央级公益性科研院所基本科研专项（ZDJ2016-01和ZDJ2017-04）联合资助. |
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| 摘 要： | 本文选取不同的地壳速度分区模型，应用双差定位法对2008—2017年发生在青藏高原东缘的地震进行了重新定位，共得到4921个精确定位结果.重定位后的地震更加集中分布于龙门山断裂带、鲜水河断裂以及四川盆地南缘，震源深度多为5~20 km.根据NGDC-720地磁场模型计算了青藏高原东缘的三分量磁异常及其梯度张量，重定位后的大多数地震位于负磁异常区域以及四川盆地西南缘的强-弱磁异常边界.基于三维分形磁化模型获得了青藏高原东缘的居里点深度，并计算了磁性层的平均地温梯度，进而利用一维稳态热传导方程获得了其地壳温度结构.结果显示青藏高原东缘大多数地震均发生在居里点深度较大、地温梯度较低的区域.大多数M≥2.0地震震源区温度为100~500℃，M≥4.0地震震源区温度多为200~400℃.2008年汶川MS8.0、2013岷县MS6.6、2014年鲁甸MS6.5以及2017九寨沟MS7.0地震震源区温度均为300℃左右，而2013年芦山MS7.0地震震源区温度接近约400℃，更多地受控于龙门山断裂带与鲜水河断裂交汇处的局部构造应力场异常.
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| 关 键 词： | 双差定位法 地震活动 NGDC-720磁异常 居里点深度 地壳温度结构 青藏高原 四川盆地 |
| 收稿时间： | 2018-03-06 |
Correlating seismicity to Curie-point depths in the eastern margin of the Tibetan Plateau |
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| WANG Jian,ZHANG GuangWei,LI ChunFeng,LIANG ShanShan.Correlating seismicity to Curie-point depths in the eastern margin of the Tibetan Plateau[J].Chinese Journal of Geophysics,2018,61(5):1840-1852. |
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| Authors: | WANG Jian ZHANG GuangWei LI ChunFeng LIANG ShanShan |
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| Affiliation: | 1. Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China;2. Department of Marine Sciences, Zhejiang University, Zhejiang Zhoushan 316021, China;3. Laboratory of Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Shandong Qingdao 266237, China;4. China Earthquake Networks Center, Beijing 100045, China |
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| Abstract: | We relocate 4921 earthquakes in the eastern margin of the Tibetan Plateau during 2008 to 2017 using two different crustal velocity models and the double-difference relocation algorithm. Our relocated earthquakes are more concentrated around the Longmenshan, Xianshuihe fault zones and southern Sichuan Basin, with most focal depths ranging 5 and 20 km. We calculate the vector and gradient tensor magnetic anomalies based on the NGDC-720 model and find that most earthquakes are located in the regions of negative anomalies, and along the southwestern margin of the Sichuan Basin as a strong-weak anomaly boundary. Curie-point depths are estimated using the centroid spectral approach based on 3D fractal magnetization model, and the average thermal gradients of the magnetic layer are calculated. Crustal temperature structures are then calculated using the 1D steady thermal conduction equation. The results show that most of the earthquakes occurred in the regions with large Curie depths and low thermal gradients. The evaluated crustal temperatures for most earthquakes hypocenters with M≥2.0 and M≥4.0 are between 100 and 500 ℃ and between 200 and 400 ℃, respectively. The 2008 MS8.0 Wenchuan, 2013 MS6.6 Minxian, 2014 MS6.5 Ludian and 2017 MS7.0 Jiuzhaigou earthquakes all occurred in the regions with estimated hypocenter temperature of about 300 ℃, whereas the hypocenter's temperature estimated for the 2013 MS7.0 Lushan earthquake is ca. 400 ℃, more controlled by regional tectonic stress anomalies in the junction area of the Longmenshan and Xianshuihe fault zones. |
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| Keywords: | Double-difference earthquake relocation Seismicity NGDC-720 magnetic anomaly Curie-point depth Crustal temperature structure Tibetan Plateau Sichuan Basin |
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