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1.
基于图形界面的波形相关法拾取远震相对走时残差 总被引：1，自引：0，他引：1
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. 相似文献
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地震体波成像中的几个问题 总被引：3，自引：1，他引：2
本文在论述地震体波成像中速度模型间断面的引入,体波多震相的利用等优越性的同时,利用研究区之处,能改善或分辨地球内部更深处的远震资料,得到研究区平均相对走时残差的分布。结果表明：１．采用相对走时残差消除了模型区域外的地球模型的影响,从而使 远震理论走时计算中,球状分层各向同性参考地球模型的选取是不重要的;２．平均相对走时残差的分布与研究区内构造分区相关;３．研究区中地球形状的椭率对反演结果影响很小。 相似文献
4.
近年来，远震走时层析成像方法有了长足的发展，在地下结构反演的研究中获得了众多成果。针对射线在台站下方覆盖率较差而导致远震反演方法对地壳速度约束不足的问题，本文提出了一种新的地壳异常体改正方法——对同一台站的相对走时残差进行求和平均去均值，消除了地壳中复杂的速度异常体对上地幔速度结构反演的干扰，反演结果具有更优的相对走时残差分布，同时反演得到的速度模型具有更小的数据方差。 相似文献
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选取2010—2020年呼和浩特基准地震台记录的195个6.0级以上极远震事件波形,分析震相特征.按照震中距由小到大的顺序,挑选出9个典型极远震事件作为研究对象,依据AK135走时表,分析波形记录特征,以期提高地震台站的震相分析水平及资料产出质量. 相似文献
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《地球物理学进展》2016,(4)
使用Zelt和Barton的方法,通过一个计算效率高的有限差分求解eikonal方程,正演计算走时和射线路径.使用最小二乘QR分解法,求解稀疏线性系统方程组.使用正则化层析反演,结合用户给定的最小的、最平坦和最平滑的扰动限制,每一个加权因子随深度变化.结合数据残差和模型粗糙度的最小化,为数据残差提供一个最平滑的近似模型.该反演方法为非线性反演,需要一个初始模型,在每一次迭代时,需要计算新的射线路径.使用二维初至走时数据,对某油田二维井间地震实际资料进行无限频率初至走时层析反演.将反演所得到的速度与井的测井速度曲线相比较,二者吻合程度较高,表明该反演方法所得速度的分辨率比较高.证实了二维无限频率初至走时层析反演可以为全波形反演提供一个分辨率较高的长波长速度模型,从而为全波形反演井间地震实际资料提供了一个比较可靠的初始速度模型. 相似文献
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本文系统地研究了宽频带远震体波波形反演的理论与方法 ,发展了较频率域除法运算稳定、精度高、分辨好的 ,从远震 P波波形中提取接收函数的时间域反褶积方法 ;并利用青藏高原中美合作研究计划获得的准确可靠的PASSCAL宽频带数字化远震波形数据 ,得到了可信的台站接收函数 ,反演了青藏高原的岩石圈速度结构 ,获得了对深部构造的新认识 ,为揭示青藏高原的动力学演化过程、建立大陆动力学理论提供了可靠的地球物理证据。主要工作简述如下 :(1 )系统回顾了用天然地震研究地壳上地幔构造的两种主要方法 :即体波走时反演方法和体波波形模拟方… 相似文献
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选取大同地震台记录的2010—2019年531个MS≥5.0地震事件,根据发震区域的不同对其波形走时残差进行分析,得到不同发震区域地震波形的平均走时残差。结果表明,日本、喜马拉雅地区地震波形的走时残差总体为负值,平均残差分别为-1.51 s、-0.70 s;斐济、中国台湾地区、南美洲西海岸地区大多为正值,平均残差为0.79 s、1.83 s、1.86 s。同时发现,在有干扰的情况下参考不同区域平均走时残差计算结果,通过判断实际初至震相与理论初至震相的位置关系,可以更好地开展初至波震相识别工作。 相似文献
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张风雪 吴庆举 李永华 高孟潭 Ulziibat Munkhuu Sukhbaatar Usnikh Demberel Sodnomsambuu 《地球物理学报》2014,57(9):2790-2801
利用中蒙国际科技合作专项项目在蒙古中南部地区布设的69个宽频带地震仪在2011年8月-2013年7月所记录的远震波形数据,采用波形相关方法在0.02~0.1 Hz的频段内拾取了18551个有效的P震相相对走时残差数据,进一步采用有限频走时层析成像的方法,反演获取了蒙古中南部下方深达800 km的P波速度结构.结果显示：肯特山下方的低速异常极有可能是推测中的肯特山地幔柱的反映;呼斯坦瑙鲁和曼达尔戈壁西边的低速异常可能与杭爱山高原下的地幔柱或地幔对流有关联;戈壁滩的低速异常带可能和达里甘嘎火山有相同的热来源,可能是该区火成岩存在的深部原因,也可能是戈壁滩及其周边地区地幔柱或下地幔热物质上涌的表现. 相似文献
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通过区域地震和远震记录的走时残差,测定华北盆地中部和周围山区的三维弹性波速度结构。我们计算了1975年唐山地震的200个余震的P波和S波的走时残差,以及从1976年至1983年间北京台网记录的194个远震的P波走时残差。仅基于余震走时残差,我们完成了地壳和上地幔结构一维和三维的块状反演迭代。我们还基于远震走时残差以及把余震和远震走时残差相结合,完成了对地壳和上地幔的块状反演迭代。我们测定出华北盆地和周围山区的地壳平均厚度接近35km,然而华北盆地沿海岸部分的地壳厚度大约为32～33km。地壳上部大约20km的速度结构与地质露头完全相关,并且相似于表面地形的短波长(几十公里)特点。低地震速度的岩石在盆地之下而高地震速度的岩石存在于山区之下。地幔顶部,也许下地壳在内,好象是上地壳和地幔之间速度结构的过渡带。关于速度结构的相对高低趋势,地幔与地壳几乎完全相反,华北盆地下伏的大部分地幔物质具有比平均地震速度要高的速度,而西部山区之下物质的速度都低于平均速度。地幔速度结构与华北盆地的重力和地形的长波(成十到成百公里)特征显然相应。盆地之下的高速地幔物质或许说明了地幔过程与华北盆地无直接关系。我们推断,短波与长波速度特点之间的过渡带表明了岩石层与软流层无相互影响的范围。尤其是华北地块的岩石层相对软流层正在向东运动。 相似文献
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Source side seismic tomography(3STomo):A novelmethod to image the subsurface structure beneath seismically active region 
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下载免费PDF全文 We propose a novel seismic tomography method,Source Side Seismic Tomography(3STomo),which is designed particularly to image the subsurface structure beneath seismically active regions.Unlike the teleseismic tomography,in which the data are relative traveltime residuals between closely spaced stations for each teleseismic event,3STomo uses relative traveltime shifts between earthquakes within the study region for each distant station.Given the relatively evener distribution of global seismic stations,this method has unique advantages for imaging the structure beneath regions that have numerous earthquakes but lack of dense seismic stations,for example,some subduction zones and spreading ridges in the ocean.In addition,3STomo has potentially better vertical resolution at shallow depths than the traditional teleseismic tomography.The effect of the inaccurate source parameters on its resolution can be minimized by using depth phases and the technique of joint source and structure inversion.Numerical experiments and application to Luzon Island,Philippines show that 3STomo can be a valuable tool to investigate the subsurface structure beneath some areas where the traditional method cannot be applied to,or at least it can be used as a complementary component of conventional teleseismic tomography to obtain better back-azimuth coverage and achieve higher resolution at shallow depths in the inversion. 相似文献
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Improving Regional Seismic Event Location in China 总被引：1，自引：0，他引：1
L.K. Steck A.A. Velasco A.H. CogbillL H.J. Patton 《Pure and Applied Geophysics》2001,158(1-2):211-240
—?In an effort to improve our ability to locate seismic events in China using only regional data, we have developed empirical propagation path corrections and applied such corrections using traditional location routines. Thus far, we have concentrated on corrections to observed P arrival times for crustal events using travel-time observations available from the USGS Earthquake Data Reports, the International Seismic Centre Bulletin, the preliminary International Data Center Reviewed Event Bulletin, and our own travel-time picks from regional data. Location ground truth for events used in this study ranges from 25?km for well-located teleseimic events, down to 2?km for nuclear explosions located using satellite imagery. We also use eight events for which depth is constrained using several waveform methods. We relocate events using the EvLoc algorithm from a region encompassing much of China (latitude 20°–55°N; longitude 65°–115°E). We observe that travel-time residuals exhibit a distance-dependent bias using IASPEI91 as our base model. To remedy this bias, we have developed a new 1-D model for China, which removes a significant portion of the distance bias. For individual stations having sufficient P-wave residual data, we produce a map of the regional travel-time residuals from all well-located teleseismic events. Residuals are used only if they are smaller than 10?s in absolute value and if the seismic event is located with accuracy better than 25?km. From the residual data, correction surfaces are constructed using modified Bayesian kriging. Modified Bayesian kriging offers us the advantage of providing well-behaved interpolants and their errors, but requires that we have adequate error estimates associated with the travel-time residuals from which they are constructed. For our P-wave residual error estimate, we use the sum of measurement and modeling errors, where measurement error is based on signal-to-noise ratios when available, and on the published catalog estimate otherwise. Our modeling error originates from the variance of travel-time residuals for our 1-D China model. We calculate propagation path correction surfaces for 74 stations in and around China, including six stations from the International Monitoring System. The statistical significance of each correction surface is evaluated using a cross-validation technique. We show relocation results for nuclear tests from the Balapan and Lop Nor test sites, and for earthquakes located using interferometric synthetic aperture radar. These examples show that the use of propagation path correction surfaces in regional relocations eliminates distance bias in the residual curves and significantly improves the accuracy and precision of seismic event locations. 相似文献
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Yang Pan Shaolin Liu Dinghui Yang Wenshuai Wang Xiwei Xu Wenhao Shen Mengyang Li 《地震科学（英文版）》2023,36(3):228-253
Teleseismic traveltime tomography is an important tool for investigating the crust and mantle structure of the Earth. The imaging quality of teleseismic traveltime tomography is affected by many factors, such as mantle heterogeneities, source uncertainties and random noise. Many previous studies have investigated these factors separately. An integral study of these factors is absent. To provide some guidelines for teleseismic traveltime tomography, we discussed four main influencing factors: the method for measuring relative traveltime differences, the presence of mantle heterogeneities outside the imaging domain, station spacing and uncertainties in teleseismic event hypocenters. Four conclusions can be drawn based on our analysis. (1) Comparing two methods, i.e., measuring the traveltime difference between two adjacent stations (M1) and subtracting the average traveltime of all stations from the traveltime of one station (M2), reveals that both M1 and M2 can well image the main structures; while M1 is able to achieve a slightly higher resolution than M2; M2 has the advantage of imaging long wavelength structures. In practical teleseismic traveltime tomography, better tomography results can be achieved by a two-step inversion method. (2) Global mantle heterogeneities can cause large traveltime residuals (up to about 0.55 s), which leads to evident imaging artifacts. (3) The tomographic accuracy and resolution of M1 decrease with increasing station spacing when measuring the relative traveltime difference between two adjacent stations. (4) The traveltime anomalies caused by the source uncertainties are generally less than 0.2 s, and the impact of source uncertainties is negligible. 相似文献
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远震层析成像是研究一个地区上地幔三维速度结构的有力手段.但由于远震射线在地壳内的交叉较差,因此无法准确约束地壳内的三维速度结构.为了消除地壳内横向不均匀性对深部速度成像产生的影响,必须进行地壳校正.本文详细描述了地壳校正的基本原理和步骤,主要包括三维地壳模型的选取、地壳内走时差的计算以及校正后的相对走时差的计算.以勘察加地区为例,通过计算各台站的平均相对走时差和远震层析成像结果分析了地壳校正的实际效果,同时验证了该方法的实用性. 相似文献
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在台网比较稀疏的情况下,台站走时标定是提高低震级事件定位、识别能力的重要手段．为了提高稀疏台网的定位精度,首先利用标定事件和IASPEI1991走时表以及中国大陆走时表,计算了初至P波和Lg波到AAK,MAKZ,NIL,TLG以及WMQ等5个台站的走时残差;接着,采用非平稳贝叶斯克里金方法和走时残差数据构造上述台站的走时校正曲面;最后,通过加入和不加入走时校正定位一系列位置准确的发生在新疆地区的地震事件评估克里金走时校正的有效性．结果表明,克里金走时校正能够较大地提高稀疏台网的定位精度,同时有效地缩小误差椭圆的面积． 相似文献
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微地震监测难以拾取准确初至,为了提高反演定位精度和减小多解性,研究了微地震贝叶斯差分进化反演方法.从分析讨论理论模型反演残差及其协方差分布特征出发,结合对比不加噪音和加入不同程度的噪音后残差协方差极小点位置移动、分布梯度变化特征,提出了先验信息解估计方法.针对后验估计中,由于难以获得先验信息解的方差估计致使无法计算加权系数问题,通过分析残差变化特征和解的变化关系,研究了利用残差求取加权系数的方法.为了加快寻优速度,讨论了差分进化反演方法,在变异操作方面使用差分策略,即利用种群中个体间的差分向量对个体进行扰动,实现个体变异,充分有效利用群体分布特性,提高算法的搜索能力,避免遗传算法中变异方式的不足.通过理论模型测试本方法的反演效果,并且和搜索方法反结果进行比较.测试结果证明本反演方法,对于不同程度初至干扰,反演结果向准确解逼近程度比搜索方法要好得多,实际资料的反演结果也好于搜索方法. 相似文献
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采用快速行进法正演计算了西藏西部地区的远震P波理论走时,随后基于该地区台阵提取到的相对到时残差利用子空间迭代算法反演得到该地区的地壳上地幔速度相对分布。层析成像结果显示:西藏西部地区在下地壳深度显示高速异常,上地幔深度该地区内部的高速异常范围从西往东逐渐减小,且研究区域东部存在高低速异常相间分布。据此认为印度板块在青藏高原内部近水平俯冲,西部俯冲范围较大,且俯冲过程中存在板块撕裂现象,撕裂的印度板块拆沉进入上地幔,而撕裂产生的间隙由于应力释放导致了西藏西部地区新生代裂谷的形成。 相似文献
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为压制伪随机多频电磁信号中的强干扰、提高数据质量,本文提出一种基于灰色判别准则和有理函数滤波的数据处理方法.首先通过灰色判别准则剔除各个频点频谱数据中的明显异常值,然后进行有理函数滤波得到充分接近真实值的圆滑数据曲线,进而约束数据的二次优化处理,剔除残余噪声的影响.为验证本文方法的处理效果,在实测无明显噪声数据中加入几种不同类型的强噪声,然后用本文方法进行处理.仿真处理结果表明,本文方法能高精度逼近原始数据,处理后数据误差低达8.09%.最后,将本文方法应用于重庆某工区实测伪随机多频电磁数据处理.结果表明,本文方法可以有效压制干扰,在频谱数据个数少、干扰幅值大（高达有效信号幅值的几个数量级）的情况下,仍可有效压制强干扰.处理后的数据相对误差显著下降,视电阻率曲线形态平滑,达到提高信噪比,改善实测数据质量的目的. 相似文献
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—?In order to improve on the accuracy of event locations at teleseismic distances it is necessary to adequately correct for lateral variations in structure along the ray paths, either through deterministic model-based corrections, empirical path/station corrections, or a combination of both approaches. In this paper we investigate the ability of current three-dimensional models of mantle P-wave velocity to accurately locate teleseismic events. We test four recently published models; two are parameterized in terms of relatively long-wavelength spherical harmonic functions up to degree 12, and two are parameterized in terms of blocks of constant velocity which have a dimension of a few hundreds of km. These models, together with detailed crustal corrections, are used to locate a set of 112 global test events, consisting of both earthquakes and explosions with P-wave travel-time data compiled by the Internation al Seismological Centre (ISC). The results indicate that the supposedly higher resolution block models do not improve the accuracy of teleseismic event locations over the longer wavelength spherical harmonic models. For some source locations the block models do not predict the range of observed travel-time residuals as well as the longer wavelength models. The accuracy of the locations largely varies randomly with geographic position although events in central Asia are particularly well located. We also tested the effect of reduced data sets on the locations. Multiple location iterations using 30 P-wave travel times indicate that teleseismic events may be located within an area of 1000?km2 of the true location 66% of the time with only the model-based corrections, and increasing to 75% if calibration information is available. If as few as 8 phases are available then this is possible only 50% of the time. Further refinement in models and/or procedure, such as the addition of P n phases, azimuth data, and consideration of P-wave anisotropy may provide further improvement in the teleseismic location of small events. 相似文献
20.
Automatic phase picking is a critical procedure for seismic data processing, especially for a huge amount of seismic data recorded by a large-scale portable seismic array. In this study is presented a new method used for automatic accurate onset phase picking based on the proporty of dense seismic array observations. In our method, the Akaike＇s information criterion （AIC） for the single channel observation and the least-squares cross-correlation for the multi-channel observation are combined together. The tests by the seismic array observation data after triggering with the short-term average/long-term average （STA/LTA） technique show that the phase picking error is less than 0.3 s for local events by using the single channel AIC algorithm. In terms of multi-channel least-squares cross-correlation technique, the clear teleseismic P onset can be detected reliably. Even for the teleseismic records with high noise level, our algorithm is also able to effectually avoid manual misdetections. 相似文献