地震反演成像中的Hessian算子研究

总结了牛顿类地震反演方法中Hessian算子的作用,对其在地震反演成像中的数学物理含义进行了分析.Hessian算子是误差泛函对模型参数的二阶导数,反映了误差泛函对模型变化的二次型特征.分析声波方程下的Hessian算子的格林函数表达形式,发现其表达了整个观测系统和子波频带等因素对地震数据空间到模型空间投影过程的影响.提出了两种分别适用于最小二乘偏移和全波形反演的Hessian算子简化格式.平面波Hessian算子应用于最小二乘偏移能够得到相对保真的成像结果,改善了地震偏移成像的精度.地下偏移距Hessian算子应用于全波形反演能够加快反演迭代的计算效率.最后,对Hessian算子在地震反演成像中的价值进行了讨论和评价.     

基于图形界面的波形相关法拾取远震相对走时残差

利用图形界面操作集成两种波形相关法(多道互相关和自适应叠加)拾取远震走时残差,在该软件包中地震学研究者通过轻松点击鼠标等基本操作即可实现数据的预处理、地震波形的质量控制、走时残差结果的显示及对比分析等操作,提高远震震相走时残差的拾取效率和准确度.     

The variable projection method for waveform inversion with an unknown source function

This paper compares three alternative algorithms for simultaneously estimating a source wavelet at the same time as an earth model in full‐waveform inversion: (i) simultaneous descent, (ii) alternating descent and (iii) descent with the variable projection method. The latter is a technique for solving separable least‐squares problems that is well‐known in the applied mathematics literature. When applied to full‐waveform inversion, it involves making the source wavelet an implicit function of the earth model via a least‐squares filter‐estimation process. Since the source wavelet becomes purely a function of medium parameters, it no longer needs to be treated as a separate unknown in the inversion. Essentially, the predicted data are projected onto the measured data in a least‐squares sense at every function evaluation, making use of the fact that the filter estimation problem is trivial when compared to the full‐waveform inversion problem. Numerical tests on a simple 1D model indicate that the variable projection method gives the best result; actually producing results in quality that are very similar to control experiments with a known, correct wavelet.     

近零能耗建筑碳排放及影响因素分析

基于全生命周期评价理论,建立了建筑全生命周期碳排放计算模型,以严寒地区某近零能耗建筑为例,开展了建筑全生命周期碳排放核算.同时,选取了建筑保温材料类型、保温材料厚度、窗户类型、窗墙面积比、供暖系统形式以及建筑使用寿命等影响因素,开展了建筑碳排放影响因素研究.结果表明:近零能耗建筑全生命周期内建材生产运输、建筑施工、建筑...     

内蒙古中西部地区小震震源机制解分析

利用P、S最大振幅比数据反演中小震震源机制方法,选取2001—2008年发生在内蒙古中西部的中小地震的数字波形数据,反演得到130个地震震源机制。研究结果表明,震源机制存在NWW-SEE向和NE-SW向的两组节面,受近NEE-SWW方位的压应力和NNW-SSE方位的张应力作用,NWW-SEE向的破裂面产生右旋走向滑动,NNW-SSE向的破裂面产生左旋走向滑动。系统聚类分析显示,内蒙古中西部中小地震以直立节面、走滑型震源机制解为主。通过对杭锦旗、托克托两次4级以上地震震源机制与背景场对比,认为均不是前兆地震。通过对震源机制的一致性参数分析,内蒙古中西部震源机制一致性参数出现低值区,对地震预测具有一定的指示意义。     

A multi-subwaveform parametric retracker of the radar satellite altimetric waveform and recovery of gravity anomalies over coastal oceans

The quality of satellite radar altimetric data is very important in studies of geodesy,geophysics,and oceanography.Over coastal oceans,altimeter waveforms are contaminated by the terrain and physical environments so that the accuracy of altimeter data is lower than that over open oceans.Here we develop a new multi-subwaveform parametric retracker(MSPR) to improve the quality of altimeter data for the recovery of gravity anomaly in coastal oceans.The least squares collocation method is used to recover the residual gravity anomaly over the coastal water from altimetric data.The waveform data records from Geosat/GM around Taiwan Island are practically retracked with MSPR.When compared with the Taiwan geoid height,the results retracked by MSPR are more accurate than those retracked by the well-known β-5-parmeter method and from the geophysical data records(GDRs).The gravity anomalies over Taiwan coastal waters are calculated from the retracked altimeter data with the least squares collocation.When we compared gravity anomalies computed using altimeter GDRs with the ship-borne gravity data over Taiwan coastal ocean,we found that the results from retracked data are more accurate than those from GDRs.     

基于粒子群优化的双力偶模型振幅谱反演方法及应用

发展了一种基于全波形振幅谱的频率域双力偶震源机制反演方法. 通过理论振幅谱与观测振幅谱的拟合搜寻断层面参数, 基于粒子群优化算法可以在较短的时间内得到稳定可靠的解． 数值试验表明, 在定位误差较大, 以及台站布局较差的情况下, 振幅谱反演仍可较为准确地得到震源机制, 并且由此计算得到的最优震源深度仍比较接近真实的震源位置． 使用该方法用2010年5月17日渤海ML4.0地震的震源机制进行了检验, 结果与加权P波初动解非常一致． 应用该方法对山东半岛及近海地区2003——2010年14次MLge;4.0地震震源机制进行了估计．      

省级测震台网系统维护新方法的研究

从服务器的硬盘管理、数据库的台站参数备份、连续波形数据的清理和数据库连接用户的管理4个方面,介绍了省级测震台网数据处理系统运行中经常出现的问题和解决的方法,并对故障产生的原因进行了阐述和解释。     

Study of full waveform inversion based on L-BFGS algorithm

Full waveform inversion is mainly used to obtain high resolution velocity models of subsurface. The size of full waveform inversion will lead to a gigantic computation cost. Under the available computer resource and the limitation of full waveform inversion,the authors propose L-BFGS algorithm as the optimization method to solve this problem. In order to demonstrate the flexibility of the method,three different numerical experiments have been done to analyze the properties of full waveform inversion based on L-BFGS.     

测震仪器定向方法探讨

测震仪器架设前须确定符合规范精度要求的NS向方位线,由于条件制约,以前NS向方位线基本借助罗盘确定,受磁偏角及外界干扰因素影响,定向精度较差。对目前使用的罗盘、寻北仪及波形相关性定向方法进行对比分析,探讨实际操作中各种定向方法的实用性。