台湾海峡及其邻区重力异常小波多尺度分析

(武汉大学 测绘学院,湖北 武汉 430070)

台湾海峡; 小波多尺度分析; 重力异常; 地壳构造

Study on the Gravity Anomalies in the Taiwan Straits and Its Vicinity Based on Wavelet Multi-scale Analysis
CHEN Lingqian,XU Xinyu,ZHAO Yongqi,TIAN Zihan,ZHAO Simin

(School of Geodesy and Geomatics,Wuhan University,Wuhan 430070,Hubei,China)

the Taiwan Straits; the multi-scale wavelet analysis; gravity anomaly; Crustal structures

DOI: 10.20015/j.cnki.ISSN1000-0666.2025.0057

备注

介绍了小波多尺度分析方法的基本原理,利用bior3.5小波对理论模型的浅部和深部异常进行了有效分离,初步验证了该方法的有效性。利用SGG-UGM-2模型和Earth2014地形模型计算了台湾海峡及其邻区的布格重力异常,并基于小波多尺度分析方法对其进行5阶分解和近似场源深度的计算,得到不同深度的重力异常。结果显示:研究区的布格重力异常值由台湾海峡中心向西北侧华南大陆逐渐降低,异常幅值为-20~580 mGal,陆地异常明显低于海洋异常,其中最低值位于扬子板块,最高值位于菲律宾板块。小波多尺度分解得到的1~5阶重力异常细节场可以反映出研究区的断裂带由不同深度构造运动产生。小波分解的4、5阶重力异常细节场在马尼拉海沟区域和加瓜海脊的异常特征反映了研究区板块俯冲生热使得下地壳高温熔融物质向上涌的动力学过程; 对比分析各阶重力异常细节场和断层分布的特征发现研究区的断裂带由不同深度构造运动产生。3、4阶重力异常细节场说明研究区的强震发生在板块边界处、次级地块的边界活动带以及高重力梯度带区域,且震源深部的地壳结构影响浅部强震的发生。
Firstly,the basic principle of the multi-scale wavelet analysis is introduced.The shallow anomaly and deep anomaly of the theoretical model are separated by bior3.5 wavelet,and the feasibility of this method is verified.Then,the Bouguer gravity anomaly in the Taiwan Straits of China and its vicinity is calculated by using the SGG-UGM-2 model and the Earth2014 terrain model.The 5th-order decomposition and approximate field source depth are calculated based on the multi-scale wavelet analysis to obtain gravity anomalies at different depths.The results show that the anomalous Bouguer gravity values in the study area gradually decrease from the center of the Taiwan Straits to the northwest side of the South China continent,and the anomalous amplitudes lie in-20~580 mGal.The anomalous values in land are significantly lower than the anomalous values in the ocean:the lowest value is appeared in the Yangtze Plate,and the highest value appeared in the Philippine Plate.The detailed 1st to 5th order anomalous gravity field obtained through multi-scale wavelet decomposition can reflect that the fault zones are generated by the tectonic movement at different depths in the study area.The abnormal characteristics of the detailed 4th and 5th order anomalous gravity field decomposed through wavelet in the Manila Trench area and the Jagua Ridge reflect the dynamic process of the heat generation through plate subduction in the study area,which causes the high-temperature molten material in the lower Crust to surge upward.The comparative analysis of the characteristics of each detailed order of anomalous gravity field and fault distribution shows that the fault zones in the study area are generated by the tectonic movement at different depths.The detailed 3rd and 4th order anomalous gravity field show that the strong earthquakes in the study area occur at the plate boundaries,the active boundary zones of the secondary blocks,and the high gravity gradient zones.The Crustal structures deep in the source have an effect on the occurrence of strong earthquakes in the shallow Crust.
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