台湾海峡OBS地震记录中二次Ps震相的特征及应用

doi:10.11978/2021178

摘要/Abstract

摘要：

在海底地震仪(ocean bottom seismometer, OBS)广角地震记录剖面上, 经常可以见到震相清晰且连续的多次波信号, 多次波和初至波是由相同的震源信号产生的, 也是地壳真实结构的反映。但是在通常的OBS数据处理过程中, 经常将多次波作为无效信号剔除掉, 对其属性及应用的研究比较少。文章通过对台湾海峡南部OBS探测测线HXN01数据的处理, 对多个台站记录到的二次震相进行了识别与拾取, 并以OBS0106台站为例, 对识别出的二次Ps震相进行了系统的研究分析, 发现二次Ps震相的波形特征和质点运动轨迹与初至震相相似, 但波形最大振幅值明显大于初至震相。通过Rayinvr射线追踪方法模拟, 确定了二次Ps震相的主要反射层, 并发现加入二次震相后, 台站下方浅部沉积层射线覆盖密度有显著提升, 射线覆盖的区域也明显增加, 为沉积层精细结构的反演提供了更为丰富的数据基础。另外, 对理论模型的地壳结构进行加入二次Ps震相前后的反演测试, 结果显示加入二次Ps震相数据后, 沉积层的界面深度误差得到明显的改善。

关键词: 海底地震仪, 二次Ps震相, 台湾海峡, 地壳结构

Abstract:

On the ocean bottom seismometer (OBS) wide-angle seismic record section, multiple signals with high energy and good continuity can often be detected. As same as the first arrival phases, multiple phases also can be real reflections of subsurface interfaces, they are generated by the same source signal. However, in the conventional OBS data processing, multiple signs are often deleted as invalid signals, just a few studies are concerned with their properties and applications. By processing the OBS data acquired from Line HXN01 in the southern Taiwan Strait, the secondary phases are identified and picked on eight seismic recording sections. Analysis of the measured data from OBS0106 station reveals that the waveform characteristics and particle motion trajectory of these two phases are very similar, the amplitude of the secondary Ps phases is greater than that of the first arrival phases. Then we determined that the secondary reflecting interface corresponds to the secondary Ps phases by Rayinvr ray tracing simulation. The fitting results of travel time shows that after adding the secondary phases, the ray-coverage density of the shallow sedimentary layer under the station is significantly increased, and the ray-coverage area is also significantly increased, which provides more information for the inversion of sedimentary structure. In addition, the inversion test before and after the addition of the secondary Ps phase was performed on the crustal structure of the theoretical model, and it was found that after the addition of the secondary Ps phase data, the interface depth error of the sedimentary layer improved significantly.

Key words: ocean bottom seismometer (OBS), secondary Ps phases, Taiwan Strait, crustal structure

中图分类号:

P712.83

郭晓然, 刘善虎. 台湾海峡OBS地震记录中二次Ps震相的特征及应用[J]. 热带海洋学报, 2022, 41(5): 57-63.

GUO Xiaoran, LIU Shanhu. Characteristics of secondary Ps phases recorded by ocean bottom seismometer in the Taiwan Strait and its application[J]. Journal of Tropical Oceanography, 2022, 41(5): 57-63.

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