冲绳海槽北部火山岩三维位场统计学联合反演及多属性聚类成像

Volcanic activity closely related to tectonic movement, is an important window to study tectonic movement. Mud diapir and mud volcano, with similar seismic reflection characteristics of volcanic rocks, widely developed in Okinawa trough. And low density, weak magnetic volcanic rocks are also development. As a result, it is difficult to identify volcanic rocks accurately utilizing the single geophysical method..The problem restricted the further study of regional tectonic evolution and mineral resources research. Therefore, the project carrying out the integrated geophysical recognition research of volcanic rocks in the northern of Okinawa trough utilizing the latest geophysics data in the area. First, on the basis of petrophysical parameter analysis, 2.5D forward models were constructed using gravity, magnetic and seismic data. And then, 3D geostatistical joint inversion of gravity and magnetic will be carried out restricted on forward models. Finally, we will obtain distribution of volcanic rocks in the northern Okinawa trough different periods based on the subspace clustering analysis of many kinds of seismic and potential attributions. Combined with results of the research, discuss the distribution regularity of volcanic rocks in the northern of Okinawa trough. Research results not only help determing the quantitative relationship between volcanic rock and geophysical properties, improve the reliability of geological understanding, can also be proved the distribution of volcanic rocks in the northern of okinawa trough and provide theoretical basis to the study of tectonic activities and the thermal evolution, exploration of mineral resources and avoiding geological disasters.

火山活动与构造运动紧密相关，是研究构造运动的重要窗口。冲绳海槽广泛发育泥底辟和泥火山，具有与火山岩相似的地震反射特征，且低密度、弱磁性火山岩较发育，单一地球物理手段难以准确识别，制约了本区构造演化和矿产资源研究的深入。因此，本申请拟利用冲绳海槽北部最新采集的地球物理资料，开展火山岩综合地球物理识别研究。首先，通过岩石物性分析，开展2.5D重磁震联合正演模拟，建立三维位场反演约束模型，在此基础上进行基于地质统计学的三维重磁联合反演，最后采用子空间聚类分析算法，对多种地震属性和位场属性组成的高维数据空间聚类成像，获得冲绳海槽北部不同时期火山岩的分布，并结合地震反射特征研究火山岩的发育年代及分布规律。研究成果不但有助于确定冲绳海槽北部火山岩与地球物理属性的定量关系，提高地质认识的可靠性，还能够探明火山岩分布规律，为该区构造运动与热演化研究、矿产资源勘查以及规避地质灾害研究提供理论依据。

冲绳海槽广泛发育泥底辟和泥火山，具有与火山岩相似的地震反射特征，且低密度、弱磁性火山岩较发育，单一地球物理手段难以准确识别，制约了本区构造演化和矿产资源研究的深入。因此，本项目利用冲绳海槽北部最新采集的地球物理资料，开展火山岩综合地球物理识别研究。通过岩石物性分析，开展2.5D重磁震联合正演模拟，建立了无井约束的三维位场反演初始模型。研究了基于协同克里金的地质统计学重磁联合反演算法，由此获得了冲绳海槽北部位场物性参数。该算法与无约束黄金分割反演算法相比，具有较高的反演精度。对冲绳海槽北部地震剖面进行了地震属性计算，获得了36种地震属性，并利用相关分析法优选出瞬时振幅、绝对振幅、瞬时频率、加权频率、瞬时相位、响应相位、瞬时Q值等7个火山岩敏感地震属性。研究了基于子空间学习的多属性聚类分析算法，对多种地震属性和位场属性组成的高维数据空间聚类成像，获得冲绳海槽北部火山岩的分布，并结合地震反射特征研究了火山岩的发育年代及分布规律。冲绳海槽岩浆活动具有以下特征：1. 自西向东，从浙闽隆起区，经东海陆架盆地，到琉球岛弧，岩浆活动带有逐渐变新的趋势；2. 岩浆岩的分布受断层的影响，明显受控于NNE向断裂；3. 岩浆活动在空间上自西向东侵入活动逐渐减弱，喷发活动逐渐增强4. 岩浆活动具有多期次的特点。研究成果不但有助于确定冲绳海槽北部火山岩与地球物理属性的定量关系，提高地质认识的可靠性，还能够探明火山岩的分布规律，为该区构造活动与热演化、矿产资源勘查以及规避地质灾害提供理论依据。