复杂地壳接收函数H-κ叠加——以安纳托利亚板块为例

本文理论分析了具有不同沉积层和壳幔过渡带结构的接收函数及其相关的H-κ叠加结果,然后采用接收函数H-κ叠加和波形反演方法获得了具有复杂构造演化历史的中北安纳托利亚板块的地壳厚度(H)、V_P/V_S(κ)和V_S结构.理论分析表明:厚的沉积层或沉积层和厚的壳幔过渡带共存都会使H-κ叠加失效;渐变型壳幔过渡带导致H-κ叠加的H位于过渡带中间,且随着频率增大逐渐靠近过渡带上方;倒转型壳幔过渡带导致H-κ叠加具有多极值,其结果可能反应过渡带内最大波阻抗界面上的地壳结构;1km·s~(-1)的V_P变化会导致H-κ叠加的H变化7km,而κ变化较小.实际资料分析表明:中北安纳托利亚H,κ和V_S具有强烈的横向不均匀性,大部分区域沉积层厚度0.5km,局部地区壳幔过渡带厚度3km;北安纳托利亚断层切穿地壳,在局部地区可能存在流体;研究区存在残留古老的小陆块体.本文研究表明,仔细分析接收函数波形和其随方位角的变化特征且用其他地震学方法进行约束,有助于采用H-κ叠加方法获取复杂地壳结构信息.

Analysis of H-κ stacking of receiver functions beneath crust with complex structure: taking the Anatolia Plate as an example

We calculated the synthetic receiver functions and their H-κ stacking results for crust with different sediments and crust-mantle transition zones, and then inverted the crustal thickness (H) and V_P/V_S ratio (κ) and S-wave velocity beneath the Anatolia plate with complex tectonic evolution history by H-κ stacking and waveform inversion of receiver functions. The synthetic tests show:H-κ stacking method is invalid in cases of existence of thick sediment or coexistence of sediment and crust-mantle transition zone; H obtained by H-κ stacking is located in the transition zone and close to the top of transition zone with the increase of frequency in gradual crust-mantle transition zone; multiple extreme values exist in the H-κ stacking and the last result is probably related to the crustal structure above the biggest wave impedance interface for inverted crust-mantle transition zone; the change of 1 km·s^-1 of P velocity results in 7 km variation of H but has little impact on κ. The real data analysis show:prominent lateral inhomogeneity in H and k and S-wave velocity were observed beneath the north Anatolian plate, with sediment of <0.5 km thick in most of the region and >3 km thick crust-mantle transition zone in local area; the north Anatolia fault extends to the mantle with existence of fluid in local area; residual old blocks may exist in the crust of the study region. Based on this study, we propose that the careful analysis of the waveform and changing trend along the azimuth of the receiver functions and the combination with other seismic methods can help to obtain reliable structural information for crust with complex structure by the H-κ stacking method.