中天山和塔里木盆地下方地幔转换带顶部P波速度结构探测

本文基于中国数字地震台网记录到的2016年1月12日发生于兴都库什—帕米尔地区的中源地震P波宽频带波形资料,利用P波三重震相方法研究了中天山和塔里木盆地北部410 km间断面起伏形态及间断面附近P波速度结构.通过波形拟合,我们发现中天山和塔里木盆地北部410 km间断面下沉约10 km;410 km间断面上方存在由塔里木盆地向中天山P波速度异常逐渐减小的约70 km厚的低速层(-3%~-1%).该低速层可能是地幔转换区物质上涌并部分脱水熔融及热效应共同作用的结果.另外我们发现中天山东北部约10~100 km深度范围内存在局部低速异常(约-6%),其很可能是上涌的软流圈物质.

Seismic detection of P-wave velocity structure atop MTZ beneath the Central Tian Shan and Tarim Basin

The broadband P waveforms from an intermediate-focus earthquake on January 12th, 2016 at Hindu Kush-Pamir, were used to study the topography of the 410 km discontinuity and velocity structure near the discontinuity beneath the central Tian Shan and the northern Tarim basin via P-wave triplications. These were recorded by the China Digital Seismograph Network. Through waveforms modeling, we find an approximate 10 km depression of the 410 km discontinuity beneath central Tian Shan and northern Tarim basin. A low-velocity layer was also revealed atop this discontinuity with a thickness of approximately 70 km, where the P-wave velocity decreased by 3% to 1% from Tarim Basin to central Tian Shan. The low-velocity layer may be attributed to the dehydration partial melting of ascending MTZ material and the heat effect of upwelling material. We also detected a local P-wave low-velocity anomaly (approximately -6%) at a depth between 10 and 100 km approximately beneath the north-eastern part of central Tian Shan. This low-velocity anomaly may be the upwelling material of the asthenosphere.