摘要
堪察加半岛位于太平洋板块的西北边缘处。太平洋板块沿堪察加海沟俯冲进入地幔,而在板块边缘处,其俯冲特征是否有不同?本研究从IRIS网站下载76个固定台站记录到的来自2239个近震事件和75个远震事件的77141条P波到时数据,利用近震-远震联合层析成像方法(TOMOG3D)获得堪察加地区壳幔内的三维P波速度结构。成像结果显示,研究区域下方上地幔内存在非常明显的高速异常块体,且与深源地震的空间分布高度一致。分析认为,该高速异常体为俯冲的西太平洋板块,俯冲角度和深度沿堪察加海沟由北向南均逐渐增加。地幔过渡带和下地幔顶部存在明显的高速异常块体,可能是因为堪察加半岛下方的太平洋俯冲板块在边缘或深部发生岩石圈熔融或拆沉现象,该高速异常块体即为拆沉的岩石圈。本文的成像结果中还可清晰地观察到2个板块窗口。堪察加地区浅部火山前线下方出现大范围的低速异常,可能是由于俯冲板块脱水或流经板块窗口的地幔流热物质导致。
Kamchatka is located at the northwestern edge of the Pacific plate.The Pacific slab is subducting into the mantle along the Kamchatka trench.Are there any differences in subduction features near the edge?To answer this question,seismic tomography was applied to 77,141 P-wave arrival times of 2239 local earthquakes and 75 teleseismic events recorded at 76 permanent stations to study the three-dimensional velocity structure to a depth of 700 km below Kamchatka.A clear high-velocity anomaly was evident beneath the study region,which is consistent with the distribution of intermediate-depth and deep-focus earthquakes.This high-velocity anomaly was interpreted as the subducting Pacific slab with its subduction angle and depth gradually increasing from the north to south along the Kamchatka trench.Another high-velocity anomaly appeared in the mantle transition zone and the uppermost lower mantle,which may reflect a piece of detached oceanic lithosphere due to melting of the subducting slab near the slab edge.Two slab windows were also found,through which hot mantle materials flowed from the subslab to the upper-mantle wedge.Large-scale low-velocity anomalies exist under the volcanic front,which reflect hot and wet upwelling flow in the mantle wedge due to the slab dehydration.
作者
刘晏廷
钟成城
江国明
赵大鹏
LIU Yanting;ZHONG Chengcheng;JIANG Guoming;ZHAO Dapeng(Key Laboratory of Intraplate Volcanoes and Earthquakes Ministry of Education/China University of Geosciences(Beijing),Beijing 100083,China;School of Geophysics and Information Technology,China University of Geosciences(Beijing),Beijing 100083,China;Department of Geophysics,Graduate School of Science,Tohoku University,Sendai 9808578,Japan)
出处
《CT理论与应用研究（中英文）》
2024年第2期135-148,共14页
Computerized Tomography Theory and Applications
基金
国家自然科学基金(西太平洋俯冲板块内橄榄石亚稳态楔的结构研究(40904021))。
