论文部分内容阅读
从2008—2011年,分别在中国大陆东南缘沿海和内陆两条NE向剖面上进行了宽频地震观测,利用记录到的远震波形资料提取得到1446个远震P波接收函数,用H-κ叠加扫描和CCP偏移叠加方法研究了中国大陆东南缘地壳及上地幔过渡带的结构及其变化特征.结合固定台网25个台站的H-κ结果,获得中国大陆东南缘(福建地区)地壳厚度从内陆到沿海逐渐减薄的图像:地壳从闽西北山区的33km减薄到厦门沿海一带的29km以下,平均地壳厚度为31.3km,具有陆地向洋壳过渡的特征;地壳泊松比从内陆到沿海显示出分带特征,闽中西部内陆地区小于0.26,沿海地带高于0.26,且在断裂带的交汇区域表现为相对异常高值.地壳上地幔顶部(0~200km)的CCP偏移叠加成像结果显示闽江断裂等NW向断裂深切Moho界面,在断裂两侧Moho面急剧抬升或下沉,产状改变,这些特征向内陆地区逐渐变得不明显.闽江等NW向断裂对研究区地壳厚度、地震等有明显控制作用.上地幔尺度(300~700km)的CCP偏移叠加成像,未见410km和660km速度间断面突变和起伏异常,其绝对深度略大于IASP91模型的,上地幔转换带厚度正常(250±5km),表明中国大陆东南缘上地幔转换带未受欧亚与菲律宾板块碰撞的明显影响,推断中国大陆东南缘及台湾海峡下方不存在俯冲板块,或俯冲前缘未扰动到410km的深度.
From 2008 to 2011, broadband seismic observations were conducted on two NE-trending sections along the southeastern margin of the mainland China respectively. Using the recorded teleseismic waveform data, 1,446 teleseismic P-wave receiver functions were obtained, and the H- κ superposition method and CCP migration superposition method were used to study the structure and variation characteristics of the crust and upper mantle transitional zone in the southeastern margin of China.According to the H-κ results of 25 stations on the fixed network, ) Image of crustal thickness decreasing from the inland to the coast: the crust has been reduced from 33km in the mountainous area of northwestern Fujian to 29km below the coastal area of Xiamen, with an average crustal thickness of 31.3km, with the characteristics of land transition to the oceanic crust; Poisson’s ratio From the inland to the coast, the zonation characteristics are shown, which are less than 0.26 in the hinterland of the central and western Fujian and 0.26 in the coastal zone, and are relatively abnormally high in the confluence area of the fault.At the top of the upper crust (0 ~ 200km) The results of offset superposition imaging show that the Moho interface at the NW trending fault such as the Minjiang fault ruptures rapidly uplifting or sinking at the Moho plane on both sides of the fault and its shape changes, which gradually becomes insignificant to the inland areas. To break the pair The crustal thickness and earthquakes in the study area have significant control effects.The CCP offset superposition imaging of the upper mantle scale (300 ~ 700km) shows no abrupt change and undulation anomalies between the 410km and 660km velocities, and its absolute depth is slightly larger than that of the IASP91 model The normal mantle transitional zone (250 ± 5km) shows that the upper mantle transitional zone on the southeastern margin of China is not significantly affected by the Eurasian-Philippine plate collision. It is inferred that there is no subduction plate beneath the southeastern margin of China and the Taiwan Strait, Not disturbed to a depth of 410km.