华北克拉通西部块体北缘及邻区地壳厚度与泊松比分布特征

收集了2010—2011年华北克拉通西部块体北缘及邻区布设的36个流动地震台和2009—2016年内蒙古自治区数字地震台网17个宽频带固定地震台站的远震事件波形数据, 采用接收函数H-κ算法分析获得了53个基岩台站下方的地壳厚度和泊松比结果。 此外, 结合已有的81个台站的研究成果, 给出华北克拉通西部块体北缘及邻区地壳厚度与泊松比分布特征。 综合分析认为, 研究区地壳厚度在整体上呈现自东向西渐变的特征, 最厚的地方出现在华北克拉通西端的阿拉善地块(～48.7±3.0 km)。 研究区平均泊松比为0.27, 泊松比高值异常出现在河套断陷带, 意味着可能具有较高的地壳温度或者存在壳内部分熔融。 研究区内不同构造单元呈现出显著的地壳厚度和泊松比分布特征的差异性, 意味着在华北克拉通构造演化过程中, 不同地区经历了不同的地壳改造过程。

Distribution of Crustal Thickness and Poisson's Ratio beneath the Northern Margin of the Western Part of North China Craton and Adjacent Areas

We collect waveform data of worldwide teleseismic events by 17 broadband seismic stations from the Inner Mongolia Autonomous Region Digital Seismic Network and 36 temporary seismic stations distributed in northern margin of the western part of North China Craton and adjacent areas during different periods of 2009—2016 and 2010—2011, respectively. Using the receiver functions of H-κ method, we calculated the crustal thickness and Poisson's ratio beneath 53 stations constructed on bedrocks. We present the crustal thickness and Poisson's ratio distribution characteristic of the northern margin of the western part of North China Craton and adjacent areas based on a compilation of 81 seismic stations for receiver function H-κ analysis published in the literature and our results. Comprehensively analyzing the fine crustal constrains distribution information in this study lead to the following conclusions. The crustal thickness of the study area gradually increases from east to west overall. The thickest crust is found in the Alxa block located in the western part of North China Craton (～48.7±3.0 km). The average crustal Poisson's ratio is about 0.27. The highest Poisson's ratio is found in the Hetao rift, indicating high ambient crustal temperatures or wide-spread intra-crustal melting. There is significant difference of crustal thickness and Poisson's ratio on the different tectonic units, they may reflect that those areas experience distinct processes of crustal modification in the tectonic evolution process of the North China Craton.