摘要
根据波茨坦地磁场模型(POMME6.2),研究喜马拉雅东构造结周围地区地壳磁异常的空间分布、磁异常随高度的衰减特征.利用二维小波变换方法对地表磁异常进行分解,分析小波细节组合和逼近信号的异常特点.讨论磁异常与地质构造的联系.结果表明,研究区内地壳磁异常分布相当不均匀.喜马拉雅—东构造结—龙门山—大巴山地区分布着较强的负磁异常;四川盆地为正磁异常,其他地区磁异常较弱.东构造结对周围地区磁异常有重要影响,它及其周围地区的地壳磁异常都是在负磁或弱磁异常背景上,叠加着中短波长的正负磁异常.这些中小尺度磁异常由中、上层地壳磁性物质产生,走向与地质构造基本一致.沿金沙江、红河断裂带分布着清晰的弱磁异常带.龙门山断裂带、丽江—小金河断裂带和红河断裂带是磁异常强弱过渡带.青蒇高原中部东西向的磁异常,在东构造结弧顶地区呈弧形分布.青藏高原中部和滇中地块带状、团状磁异常具有相同的衰减规律.
Based on Potsdam Magnetic Model of the Earth （POMME6.2）, the spatial distribution of crustal magnetic anomalies around eastern Himalayan syntaxis and their decay with altitude were studied. The two-dimensional wavelet transform method was employed to decompose ground magnetic anomalies and analyze combination of wavelet details and anomalies of approximation signal. The relationship between magnetic anomaly and geological structure was discussed. The results show that the distribution of crustal magnetic anomalies over the study area is considerably non-uniform. Relatively strong negative magnetic anomalies were distributed over Himalaya-Eastern syntaxis-Longmen mountains-Daba mountains, whereas positive magnetic anomaly is present over Sichuan Basin, with weaker magnetic anomalies over other regions. The eastern syntaxis had important impact on magnetic anomalies around. All crustal magnetic anomalies over eastern syntaxis and the surrounding regions were medium- and short-wavelength positive/negative ones superposed onto a negative or weak magnetic anomaly setting. These meso- and micro-scale magnetic anomalies were generated from magnetic materials in the upper and middle crust, with strikes basically consistent with geological structures. Along Jinshajiang- Honghe Fault Belt, there is a sharp weak magnetic anomaly belt. Longmenshan Fault Belt, Lijiang-Xiaojinhe Fault Belt and Honghe Fault Belt are transitional zones between strong and weak magnetic anomalies. The east-west magnetic anomalies in the central Tibetan Plateau exhibited arc shape in the dome of Eastern Syntaxis. The banded lumpy magnetic anomalies over the central Tibetan Plateau and Central Yunnan massif had the same decay rule.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第11期3877-3886,共10页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(41264003)
云南省教育厅自然科学基金重点项目(2012Z048)资助
关键词
地磁场模型
地壳磁异常
小波分解
东构造结地区
Geomagnetic field model, Crustal magnetic anomaly, Wavelet decomposition, Eastern syntaxis area
