中国东北诺敏河火山岩石圈变形:来自剪切波分裂的证据

中国东北新生代板内火山广泛发育,其中诺敏河火山由于上地幔结构研究的匮乏,火山成因尚不明确.利用布设在诺敏河火山周围的40个流动台站所记录到的远震剪切波数据,测量得到82对各向异性参数和219个无效分裂结果.结果表明,研究区快慢波延迟时间变化范围为0.4～1.4s,平均0.78±0.21s;各向异性快波方向范围为N77°W—N18°E,绝大多数快波方向集中在N6.9°W±9.87°,平行于中生代晚期岩石圈伸展变形方向,推测由残留在岩石圈中的化石各向异性所引起.同时,在火山中心及周边部分台站,只观测到无效分裂而没有观测到有效分裂结果,可能是由于残存在岩石圈内的古老形变被上涌的热地幔物质所侵蚀.

Lithospheric deformation of the Nuomin River volcano in Northeast China: Evidence from shear wave splitting

Cenozoic intraplate volcanoes are widely present in Northeast China, among which the Nuomin River volcano's causative mechanism is poorly understood due to the lack of detailed constraints on the upper mantle structure beneath this region. A total of 82 pairs of shear wave splitting measurements and 219 null measurements are obtained at 40 temporary seismic stations. These data suggest that delay times vary from 0.4 s to 1.4 s with an average value of 0.78±0.21 s; while fast directions trending N77°W to N18°E with a mean value of N6.9°W±9.87° at most of stations. Fossil anisotropy within lithosphere is considered to be the main origin of anisotropy since the fast directions are in line with extensional orientation of the Late Mesozoic lithosphere in this area. Meanwhile, solely null measurements are measured at 19 stations, implying possible lithospheric thermal erosion by hot mantle upwelling.