蒙古中南部地区的上地幔P波速度结构

The P wave velocity structure of the upper mantle beneath the Central and Southern Mongolia area

利用中蒙国际科技合作专项项目在蒙古中南部地区布设的69个宽频带地震仪在2011年8月—2013年7月所记录的远震波形数据,采用波形相关方法在0.02-0.1 Hz的频段内拾取了18551个有效的P震相相对走时残差数据,进一步采用有限频走时层析成像的方法,反演获取了蒙古中南部下方深达800 km的P波速度结构.结果显示：肯特山下方的低速异常极有可能是推测中的肯特山地幔柱的反映;呼斯坦瑙鲁和曼达尔戈壁西边的低速异常可能与杭爱山高原下的地幔柱或地幔对流有关联;戈壁滩的低速异常带可能和达里甘嘎火山有相同的热来源。可能是该区火成岩存在的深部原因,也可能是戈壁滩及其周边地区地幔柱或下地幔热物质上涌的表现.

We picked 18551 relative traveltime residuals from the teleseismic waveform data by waveform correlation method in the band of 0.02-0.1 Hz.The teleseismic waveform data were recorded by the temporary seismic networks in the Mongolia from August 2011 to July 2013,supported by international science and technology cooperation project between China and Mongolia.The total number of the station is 69.We imaged the P-wave velocity structure beneath the Central and Southern Mongolia area down to 800 km depth by finite-frequency traveltime tomography.The results reveal that：The low velocity anomaly beneath the Hentiy Mountain is very likely related to the conjectured Hentiy Plume.The low velocity anomaly to the west of Khustain Nuruu and Mandalgovi has some relationship to the Hangay Plume or mantle flow beneath the Hangay Plateau.Maybe the low velocity anomaly zone beneath the Gobi Desert has the same origin of Dariganga volcano,and maybe this deep low velocity anomaly could account for the existence of igneous rocks in this area.Maybe this low velocity is also the manifestation of another mantle plume or mantle hot material upwelling from the lower mantle.