华北地区上地幔速度结构

本文选用了北京台网记录的来自不同方位并通过华北地区的140个地震,使用平滑法和dT/d△法,得到P波慢度曲线;采取走时和慢度结合使用的方法,得到走时曲线;从Gerver-Markushevich公式出发,导出一个易于计算的简捷形式,并由此反演初始速度模型;通过模型理论走时曲线的计算,选出与实测数据符合得较好的模型。平均模型中,低速层出现的深度较浅,约60公里;在360-420公里和660-680公里深处,存在两个速度急剧增加的梯度层;500公里处可能还有一个较小的梯度层。华北的东南和西南方向上,相当于660公里梯度层的深度的差异还较为显著。     

Joint analysis of seismological data by the USSO and DSS stations in the Caucasus region

This paper deals with a procedure of a joint analysis of seismic data from earthquakes and those obtained by DSS. The DSS data are used as a first approximation to construct a two-dimensional model of the medium made up of individual blocks. These models serve as a basis when constructing specific three-dimensional travel-time curves. These travel-time curves are further used for the calculation of hypocenter parameters in a laterally inhomogeneous block medium.The hypocenter field and the travel times obtained are input data for the computation of three-dimensional fields of velocities in earthquake focal zones. Results of applying the proposed procedure to the Caucasus region are presented.     

On the Use of Calibration Explosions at the Former Semipalatinsk Test Site for Compiling a Travel-time Model of the Crust and Upper Mantle

—?Two chemical calibration explosions, conducted at the former Semipalatinsk nuclear test site in 1998 with charges of 25 tons and 100 tons TNT, have been used for developing travel-time curves and generalized one-dimensional velocity models of the crust and upper mantle of the platform region of Kazakhstan. The explosions were recorded by a number of digital seismic stations, located in Kazakhstan at distances ranging from 0 to 720?km. The travel-time tables developed in this paper cover the phases P, Pn, Pg, S, Sn, Lg in a range of 0–740?km and the velocity models apply to the crust down to 44?km depth and to the mantle down to 120?km. A comparison of the compiled travel-time tables with existing travel-time tables of CSE and IASPEI91 is presented.     

Anisotropy and large-scale lateral inhomogeneity of the upper mantle

An investigation of travel-time residuals of P waves as compared to an average global travel-time curve with a base-line determined shows that about 400–500 km of the upper mantle at the boundary with the crust and a similar thickness of the lower mantle at the boundary with the core are laterally inhomogeneous. The upper mantle both under continents and under oceans consists of crust-mantle blocks distinguished by longitudinal wave velocity, surface tectonics and intensity of the heat flow. It has been revealed that within individual crust-mantle blocks there is an azimuthal relationship of P-wave travel-time indicative of possible anisotropy of upper mantle elastic properties down to depths of the order of several hundred kilometers.     

Results of deep seismic soundings along international profile VII in Czechoslovakia and poland

Summary The paper deals with the results of DSS measurements along international profile VII, carried out by Czechoslovak and Polish geophysicists in 1970 – 71. The profile situation is shown in Fig. 1. By 1971 part of the profile in the region of the Bohemian Massif between points 1 and 3 and in Poland between points 5 and 7 had been surveyed (Fig. 2). The seismograms were used to construct the travel-time curves of the fundamental types of waves P^K, P^M, P_n (Fig. 4). The mean velocities were computed from the travel-time curves of the reflected waves (P^M and P^K) and the refracted waves (P_g). Isolines of the mean velocities could be constructed for the region of the Bohemian Massif (Fig. 6). The velocity data found were used for the depth interpretation of the travel-time curves of the principal types of waves and to construct a seismic section (Fig. 8). In the region of the Pre-Sudeten block the thickness of the crust was found to be 34–37 km, and in the Sudeten it increased to 40 km. Towards the south the thickness of the crust gradually reduces to 30 km in the system of the Luice faults. In the Bohemian Cretaceous the thickness of the crust is about 30 km. Further to the south, in the region of the Moldanubicum, the thickness of the Earth's crust increases rapidly, and at the southern border of the Central Bohemian pluton it reaches values of about 42 km.     

New average global P and PcP travel times

This paper deals with the construction procedure for regional travel-time curves and the new average global curve for P times. This paper also presents new average global values for PcP times constructed from observed travel times.     

测井声波时差反演重构技术研究及应用

利用测井声波时差、自然电位和伽玛重构声波时差,分析了以上3种曲线结果对地质体响应方面的机制差异,给出了这些曲线的深度相对移动校正的方法。研究了多条测井曲线去噪的协方差矩阵特征向量滤波方法。在此基础上,利用小波多尺度分解技术进行声波时差曲线重构。在分析这3种测井曲线不同尺度小波分解结果的信号和噪音特点后,利用相邻分解尺度相关滤波技术,对各种曲线的小尺度(高频)分解结果进行滤波处理。为保证重构声波曲线的真实性,深入分析了多曲线、多尺度分解结果的冗余性(相关性)问题;利用特征值技术,对高频多尺度分解分量进行了非相关(正交)分析,最后实现了声波时差曲线的重构,并对重构结果与钻井岩心录井资料进行了对比验证,重构后的声波曲线在区分砂、泥岩性分辨率方面具有明显的提高     

Computation of diffracted rays in inhomogeneous media with curved interfaces

Summary A method for computing certain types of diffracted rays and corresponding travel-time curves in laterally inhomogeneous media with slightly curved interfaces is suggested. Numerical examples are presented.Dedicated to Academician Alois Zátopek on His 65th Birthday     

Analysis of the IMS Location Accuracy in Northern Eurasia and North America Using Regional and Global Pn Travel-time Tables

—?Joint Research Program of Seismic Calibration of the International Monitoring System (IMS) in Northern Eurasia and North America has been signed by the Nuclear Treaty Programs Office (NTPO), Department of Defense USA, and the Special Monitoring Service (SMS) of the Ministry of Defense, Russian Federation (RF). Under the Program historical data from nuclear and large chemical explosions of known location and shot time, together with appropriate geological and geophysical data, has been used to derive regional Pn/P travel-time tables for seismic event location within the lower 48 States of the USA and the European part of the RF. These travel-time tables are up to 5?seconds faster in shields than the IASPEI91 tables, and up to 5?seconds slower in the Western USA. Relocation experiments using the regional Pn travel-time curves and surrogate networks for the IMS network generally improved locations for regional seismic events. The distance between true and estimated location (mislocation) was decreased from an average of 18.8?km for the IASPEI91 tables to 10.1?km for the regional Pn travel-time tables. However, the regional travel-time table approach has limitations caused by travel-time variations inside major tectonic provinces and paths crossing several tectonic provinces with substantially different crustal and upper mantle velocity structure.¶The RF members of the Calibration Working Group (WG): Colonel Vyacheslav Gordon (chairman); Dr. Prof. Marat Mamsurov, and Dr. Nikolai Vasiliev. The US members of the WG: Dr. Anton Dainty (chairman), Dr. Douglas Baumgardt, Mr. John Murphy, Dr. Robert North, and Dr. Vladislav Ryaboy.     

地震定位研究及应用综述

地震定位是地震学中最经典、最基本的问题之一，提高定位精度也一直是地震学应用研究的重要课题之一。本文就目前各种地震定位方法进行了大体分类并概述了基本原理及其应用，介绍了目前在国内各实时地震观测系统中应用的台网定位方法，同时将部分台网方法应用于黑龙江省绥棱爆破的定位。     

Seismic velocity structure using array data

The fine structure of regional travel-time curves is investigated. About 200 events from the region north of Australia, recorded at the Warramunga array, are analysed to give the P-wave velocity structure for that region. The events were confined to a very narrow azimuth range. Results show that the 20° discontinuity is more complicated than a single velocity increase near 400 km depth, and that there are regions of rapid or discontinuous velocity increase at depths below 650 km.     

Crustal structure of the Caucasus from the Stepnoe-Bakuriani and Volgograd-Nakhichevan DSS profiles (reinterpretation of the primary data)

This work presents the results of reinterpretation of the deep seismic sounding (DSS) data for the Stepnoe-Bakuriani profile and the southern part of the Volgograd-Nakhichevan profile, carried out using new processing methods. Both the profiles cut the trend of the Greater Caucasus. They were acquired in the 1960s by multichannel continuous profiling, which provided high-quality records; however, only the travel-time curves for the main wave types have survived till now. The waves recorded on these profiles have a rather complex origin and their processing by the methods existing at that time was a challenge. At present, the modern computer technologies allowed us to invert the preserved travel-time curves for the velocity models of the Earth??s crust and the very tops of the mantle down to 80 km. It is shown that the crustal thickness increases under the Greater Caucasus up to 50?C60 km and this increase is not gradual, as implied in the previous reconstructions, but occurs through a system of deep dislocations. Traced by the oblique reflections and sharply contrasting seismic velocities, these dislocations extend into the crust. An extended, north-dipping boundary is revealed at a depth of 50?C80 km. The velocity model of the Greater Caucasian crust exhibits slightly decreased velocities compared to the surrounding platform regions. At the same time, the velocities sharply increase in the middle and even upper parts of the crust in the Kura depression.     

槽波层析成像方法在煤田勘探中的应用——以河南义马矿区为例

在地下煤田的开发中,工作面内的小构造、异常体、煤层厚度变化等是需要解决的关键问题,而槽波探测则为这些问题的解决提供了重要的物探方法.本文对河南义马矿区11061工作面进行槽波透射法测量,在巷道显示的煤层厚度变化为1.5~8 m,从理论频散曲线分析速度与厚度关系,确定125 Hz频率槽波主要用于观测厚度约为2~5 m的煤层厚度变化;有效提取了684个频散曲线,并分别拾取了125 Hz时槽波群速度与走时,采用走时层析成像方法获得工作面内煤层速度、厚度以及高应力区分布特征,回采验证了结果的正确性.     

随钻斯通利波测井反演地层渗透率的理论、方法及应用

针对孔隙渗透地层的随钻声波测井问题,用Biot-Rosenbaum孔隙弹性波测井理论推导了孔隙地层的随钻井孔声场表达式.据此考察了随钻条件下井中斯通利波的波形、相速度频散、衰减以及相速度对渗透率的灵敏度,并与电缆测井中的情况进行了对比.数值模拟结果表明,随钻条件下斯通利波对地层渗透率的灵敏度相对于电缆测井有明显增加,更有利于用来反演地层渗透率.为快捷有效地处理现场测井数据和反演计算,采用简化Biot-Rosenbaum理论和钻铤的等效模型,对随钻斯通利波的频移和时滞进行联合反演.结果表明,随钻斯通利波反演的渗透率与核磁渗透率和岩心覆压测试渗透率符合较好,并且与常规测井曲线所反映的储层性质具有较好的一致性,证明了利用随钻斯通利波评价地层渗透率的有效性.     

Estimation of PKP times from ISC data

The International Seismological Centre (ISC) treats reports of the earliest observed core phase arrivals from earthquakes as PKIKP observations and provides residuals based on Jeffreys-Bullen PKIKP times. An analysis of some 30 000 such data from ISC bulletins for the year 1967 has shown that the data include, in addition to PKIKP, many observations of PKP₁ and precursors to PKP. By the use of simple truncation and trimming techniques, travel-time curves (expressed as differences from JB), with standard errors, have been obtained for PKIKP in the ranges 110 to 139° and 152 to 173°, and for PKP₁ in the range 144 to 154°. The PKIKP curve in these ranges agrees quite closely with the curve obtained by Cleary and Hales, and with one derived from model 1066B of Gilbert and Dziewonski, except that the Cleary-Hales curve is up to 0.7 s earlier at distances below 120°, and the 1066B curve is up to 1 s later beyond 152°. The PKP₁ curve is in good agreement with that derived from 1066B.A plot of the number of observations in each 1° distance interval has been used to estimate the positions of the cusps B, C and D on the PKP curve as 144, 152.5 and 115°, again in reasonable agreement with 1066B.     

Seismic phase picking in China Seismic Array using a deep convolutional neuron network*

Seismic phase picking is the preliminary work of earthquake location and body-wave travel time tomography. Manual picking is considered as the most accurate way to access the arrival times but time consuming. Many automatic picking methods were proposed in the past decades, but their precisions are not as high as human experts especially for events with low ratio of signal to noise and later arrivals. As the increasing deployment of large seismic array, the existing methods can not meet the requirements of quick and accurate phase picking. In this study, we applied a phase picking algorithm developed on the base of deep convolutional neuron network (PickNet) to pick seismic phase arrivals in ChinArray-Phase III. The comparison of picking error of PickNet and the traditional method shows that PickNet is capable of picking more precise phases and can be applied in a large dense array. The raw picked travel-time data shows a large variation deviated from the traveltime curves. The absolute location residual is a key criteria for travel-time data selection. Besides, we proposed a flowchart to determine the accurate location of the single-station earthquake via dense seismic array and phase arrival picked by PickNet. This research expands the phase arrival dataset and improves the location accuracy of single-station earthquake.     

一种基于层析成像技术提高浅地表面波勘探水平分辨率的方法

在高频面波方法中,水平分辨率是指水平方向上分辨异常体的能力.异常体在水平方向上的长度可用水平方向上横波速度的异常尺度来确定.面波多道分析（MASW）方法被广泛应用于浅地表横波速度结构的探测,然而该方法确定的横波速度是整个检波器排列的平均计算结果,因此水平分辨率较差.另外,采用共中心点（CMP）多次覆盖的方式采集数据亦增加了野外的工作量.我们在MASW方法的基础上,应用面波层析成像方法,提出一套提高面波勘探水平分辨率的完整方法的技术流程.首先,利用波场分离技术获得准确的基阶或高阶模式面波,采用相位扫描的互相关方法测量多道面波记录中任意两道之间的面波走时;然后根据面波层析成像方法,获得高分辨率的各目标网格内的纯路径相速度频散曲线;最后反演所有目标网格内的纯路径相速度频散曲线,得到研究区域的拟二维横波速度结构.这套方法具有一定的抗噪能力,理论上它可以准确地提取相邻两道之间面波的相速度频散曲线;同时由于该方法最少只需要1个排列就可以获得拟二维横波速度结构,因此它显著减小了野外工作量.理论模型和实际资料都证实了这套方法可有效提高面波勘探的水平分辨率.     

Mapping of upper mantle structure from differential (PP — P) travel-time residuals

P and PP travel-time residuals have been collected from 23 quarters of the regional catalog of earthquakes of the International Seismological Centre (ISC). The difference in travel-time residuals between PP and P are used as an indicator of the P-delay time near the PP reflection point. Global maps of these differential travel-time residuals are used to study lateral heterogeneity in the crust and upper mantle. Two of the regions studied have mean differential travel-time residuals significantly different (at greater than the 95% confidence level) from the global mean of the differential travel-time residuals. In the central Pacific, southeast of Hawaii, differential PP — P travel-time residuals of ? 3.8 ± 0.36 s are observed. These observations imply an average P-delay time of ? 1.1 ± 0.38 s. Average P-delay times of 0.67 ± 0.20 s are observed beneath the Tibetan Plateau and the western portion of the People's Republic of China. These travel-time variations basically agree in location and sign with the surface wave results of Tanimoto and Anderson.     

Improving Regional Seismic Event Location in China

—?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.     

Travel times ofP-waves for the Swedish-Finnish seismograph network

Summary About 360 seismic events from almost all directions recorded at 13 seismological observatories in Sweden and Finland have been investigated. The depths of these events vary from the surface to 650 km and the epicentral distances from 9° to 119° with fairly even coverage. The two most separated stations in this array are about 15° apart (Karlskrona in Sweden and Kevo in Finland). Comparison of observed travel-time curves and their slope with those ofJeffreys-Bullen andHerrin are made. Generally, the observed travel times are earlier than theJeffreys-Bullen times and later than theHerrin ones. Path and depth effects on residuals with respect to the two given tables are studied, and station corrections and source corrections are estimated. Global and regional travel-time tables of theP-wave have been constructed for this network of stations.On leave from Geophysical Institute, Tehran University, Tehran, Iran