| 利用P波“影区”特征探测青藏高原东部岩石层内低速层 |
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| 引用本文： | 焦煜媛,沈旭章,马克博,钱银苹,王静波.利用P波“影区”特征探测青藏高原东部岩石层内低速层[J].地震学报,2016,38(6):824-834. |
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| 作者姓名： | 焦煜媛 沈旭章 马克博 钱银苹 王静波 |
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| 作者单位： | 1.中国兰州 730000 中国地震局兰州地震研究所 |
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| 基金项目： | 中国地震局地震预测研究所基本科研业务专项(2014IESLZ03)和国家自然科学基金(41274093, 41574077)共同资助国家自然科学基金41274093中国地震局地震预测研究所基本科研业务专项2014IESLZ03国家自然科学基金41574077 |
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| 摘 要： | 选用我国西藏及其周边地区测震台网35个台站宽频带数字地震仪记录到的2014年10月7日云南普洱MS6.1地震的波形资料，分析了垂直向分量初至P波的幅度特征.结果表明:在震中距处于5°-18°之间的P波初动幅度相对较小，存在“影区”特征，推测该“影区”是由青藏高原下方岩石层内低速层所引起的；通过试错法，多次对比不同模型的理论波形与观测波形的P波初动振幅随震中距的变化形态，最终确定在78 km深处存在一厚度为24 km的低速层，层内速度梯度约为-0.05/s.
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| 关 键 词： | 岩石层 低速层 地震波影区 理论地震图 青藏高原 |
| 收稿时间： | 2015-12-04 |
Exploration of the low-velocity layer within the lithosphere beneath the eastern Qinghai-Xizang Plateau using the P wave shadow zone |
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| Affiliation: | 1.Lanzhou Institute of Seismology, China Earthquake Administration, Lanzhou 730000, China2.Lanzhou Base of Institute of Earthquake Science, China Earthquake Administration, Lanzhou 730000, China |
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| Abstract: | This paper analyzed the first arrivals of vertical P waveforms of the Pu'er MS6.1 earthquake in Yunnan Province on October 7, 2014 recorded by 35 broadband digital seismic instruments that belong to seismic networks of Xizang (Tibet) and its surrounding areas. The result shows that amplitudes of P wave onsets are relatively weak in the epicentral distance of 5°-18°, which is consis-tent with the characteristics of shadow zone. Therefore, it is deduced that the low-velocity layer within lithosphere beneath the Qinghai-Xizang Plateau might be the most possible reason for the shadow zone. Based on the numerical tests of trial and error method and comparison of the observed amplitudes with synthetic ones of P wave onsets predicted by the reflectivity method, the model with a low-velocity layer of 24 km thick at the depth about 78 km can well explain the observations, and the velocity gradient within the low-velocity layer is -0.05/s. |
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