Investigation of the earth's crustal structure using earthquake and deep seismic sounding data obtained for the Carpathians

The joint analysis performed for the Carpathian region from seismological data (three-dimensional fields of velocities, areas of concentration of earthquake foci in the Vrancea focal zone) and interpretation of DSS data and those of other geophysical fields have permitted to obtain new evidence for the earth's crust and mantle structure in this region.     

The structure of the Baltic Shield region on the basis of DSS and earthquake data

The lithospheric models obtained for the Baltic Shield by using deep seismic soundings are discussed and results from different parts of the shield are compared with models achieved by the investigation of surface waves and of P to S converted waves. The results are found to agree rather well with each other particularly with regard to the first interface (at a depth of 10–15 km) and the whole thickness of the crust (c. 40 km). The macroseismic focal depth determinations of regional earthquakes are correlated with lithospheric structure. The main maximum in the focal depth distributions of Finnish earthquakes occur at a depth of 10–12 km. The geographical distribution of the earthquake epicentres suggests several seismo-active zones in the northern Baltic Shield. One new finding in this field concerns the Lapland zone, which runs in a north-westerly direction.     

ADAPT区域数字地震台网数据汇集与处理软件包

已经开发了一种区域数字地震台网处理软件包，称作ADAPT(Adaptive Data Acquisition and Processing Tools）。ADAPT软件系统适用于安装在区域遥测数字地震台网中心的Windows NT计算机网络，用于汇集和处理来自台网所属台站的数字地震波形数据，其主要功能包括在线自动处理和人机交互处理两个方面。本文将介绍ADAPT系统的基本功能，分析该系统的特点，并着重说明系统中采用的地震定位方法。     

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.     

大高加索山脉冰川反照率时空分布及与物质平衡的关系

利用MOD10A1和MYD10A1冰雪反照率数据, 分析了大高加索山脉地区加拉巴西冰川和德扬库特冰川的反照率时空分布特征, 并使用五种反照率聚合方法, 对这两条冰川2002—2019年夏季反照率与物质平衡关系开展相关性研究.结果表明, 加拉巴西冰川和德扬库特冰川反照率随年份增加而明显减小, 两条冰川在夏季都出现了最低反照率, 加拉巴西冰川在冬季出现最高反照率, 而德扬库特冰川则出现在春季; 加拉巴西冰川夏季高海拔和低海拔区域的反照率差异较德扬库特冰川更为明显; 两条冰川夏季反照率均与夏季物质平衡表现出一定的正相关性, 其中加拉巴西冰川的相关性更加显著, 使用平均最小反照率方法时两者相关系数最大可达0.874(p＜0.05), 德扬库特冰川使用加权平均反照率方法时两者相关系数最大为0.765(p＜0.05).德扬库特冰川反照率与物质平衡相关性较低的原因可能是坡向和低海拔导致了其更易受暖湿气流影响, 冰川消融中短波辐射能占比较低, 反照率对其消融的影响小.

     

青海省新增地震台波形数据质量评价

为了进一步提升青藏高原地震监测能力,中国地震局在青海、西藏和新疆3个地区建设地震台站。为确保高质量产出地震数据,以青海地区新增16个地震台站为例,围绕观测数据的完整性和可靠性,基于数据连续率、台基噪声水平和事件波形记录质量,对地震观测数据质量进行评价,结果发现：青海地区新增地震台站观测环境较好,总体运行稳定,数据连续率较高,适合进行宽频带数字地震观测;地震台站空间分布更加均匀,青海省中西部地区理论地震监测能力从约M_S 4.5提升到M_S 2.0,地震监测能力提升。本项工作的开展,为我国青藏高原地震监测能力提升提供了业务化支撑。     

国家地震台数据断记统计及批量补数自动处理

在VS2015开发环境下,使用C#语言编写国家地震台断记统计和批量补数自动处理程序,实现数据中断统计查询、数据采集器波形数据文件下载和上传波形数据文件至远程服务器的自动化。该自动处理程序在部分地震台使用以来,运行良好,数据完整率、连续率得到保障。     

南极地震学研究进展

归纳总结了在南极开展地震学研究中的各种主要方法及其研究成果,较全面地介绍了南极地震学研究的现状与进展．首先对南极地震活动性作了简单的介绍,然后分别介绍了利用面波和体波研究地壳上地幔结构的主要成果,最后从地震各向异性的角度归纳介绍了南极大陆部分区域面波方位各向异性及剪切波分裂研究的主要成果．研究表明,南极大陆地震活动性较低、地震强度较小,仅在横贯南极山脉区域、维多利亚地、阿黛利地、威尔克斯地等有较明显的地震活动; 横贯南极山脉将南极大陆分为东南极和西南极两个不同的地质构造区域,东南极地壳和上地幔地震波速度偏高,西南极则偏低;上地幔各向异性较为明显并普遍存在,且西南极各向异性强度稍高于东南极克拉通．     

基于测震观测的波形分析应用软件WAVE2005

首先概述了数字地震波形分析的重要性及该领域一些主要波形分析软件的概况,然后介绍了《数字地震波形分析-WAVE Version 2005》软件的设计目标、研制思路、系统特点、框架结构、操作界面、技术特点、方法功能等;最后给出了一个应用的实例.     

永安地震台钻孔体应变地震响应能力评估

本文从永安地震台现状、观测手段布设、科普宣传工作和应急经验体会等方面就2018年明溪3.9级地震与2018年11月26日台湾海峡6.2级地震震后应急工作进行思考。为台站工作者提供应对突发事件时应该采取的具体工作流程和应对措施,具有一定的实践意义,对其他台站具有一定参考作用。     

火山区台站观测的地震波分析与应用

以长白山天池台记录的地震Ｐ、Ｓ波及腾冲台记录的地脉动资料为基础，分析研究了火山区台站观测的地震波在微震监测与分析、火山地震类型判别、火山区介质非均匀性与各向异性分析以及地震预报与火山喷发监测在预报中的应用．     

Bayesian estimation of strong earthquakes in the Inner Messiniakos fault zone, southern Greece, based on seismological and geological data

Statistical estimates of earthquake magnitudes are unreliable when based onvery few historical data. Additional sources of information, such asgeological data, are then necessary to update estimates of seismicityparameters. The Bayesian probability theory is a tool to combine priorinformation of seismicity obtained from geological data with historicalobservations. This theory is tested in the case of the Inner Messiniakosfault zone, southern Greece, for the estimation of the probability ofoccurrence of strong earthquakes. Prior estimates of seismicity aredeveloped from slip rate measurements, obtained from offsets of geologicalformations, on the basis of both onshore and offshore neotectonic data.The analysis emphasizes the importance of the input seismicity parameters,particularly the significance of the upper bound magnitude in the estimationof the seismic potential of active faults.     

Extracting rotational components of earthquake ground motion using data recorded at multiple stations

Rotational components of earthquake ground motion have not been considered for seismic analysis, design and performance assessment because recordings of these components are unavailable. A number of procedures have been proposed to extract rotational components of ground motion from translational time series recorded at multiple, closely spaced recording stations. In this paper, a new procedure that is capable of capturing higher frequency content in rotational time‐series is presented. The frequencies at which numerical errors are introduced in the solution, which are a function of apparent wave velocity and array dimension, are identified. Results are presented for the proposed procedure, the widely accepted geodetic method, and a single‐station procedure developed by the authors, all using data recorded at the Lotung array in Taiwan. Copyright © 2012 John Wiley & Sons, Ltd.     

Attenuation in the uppermost inner core from PKP recordings at African seismological stations

The attenuation factor Q_P at the top of the inner core is evaluated by using the amplitude spectral ratio of PKPdf and PKPbc phases observed at African stations (BGCA mostly), from strong deep earthquakes in the Pacific Ocean area. The maximum depth of penetration of the PKPdf phase into the inner core (IC) is roughly 377 km, and the sampled region of IC is centered beneath the Southern Indian Ocean. The derived mean value of Q_P is 249 ± 31 (95% confidence level) in the frequency range 0.2–2 Hz, where no frequency dependence of attenuation has been reliably observed. By using Student’s t-test, we show that the value is statistically significantly different (with a probability greater than 95%) from other mean values of Q derived by using the same method, for both the western (180 °W to 40 °E) and eastern (40 °E to 180 °E) hemispheres of the IC. The decrease of Q with the radius of the turning point (denoted by r^TP), according to Q_P = 840 − 0.62 r^TP, has a moderate statistical support (the R-squared value is 38%). A slightly increase of Q as a function of the angle of the PKPdf path within the inner core with respect to the Earth’s spin axis is observed, in agreement with various investigations performed in the time domain. However, the value of the anisotropy, if any, is suggested to be around 3%.     

地震科普中易被误解的几个地震学概念问题

解读了地震科普中易被误解的一些地震学概念问题:①地震来了,真的是纵波(P波)先到,感觉上下振动,然后横波(S波)到,感觉左右或前后水平方向振动吗?②震级是按地震波能量分级来刻画地震大小的吗?③地震波能量就是地震释放的总能量吗?④宏、微观地震参数有时为什么相差那么大?是误差问题,还是参数定义就有差异?⑤汶川地震地震动衰减的方向性那么强,成都市区遭受破坏相对较轻的主要原因是什么?     

Three-dimensional electrical structure of the northwestern margin of the Karamay region,China, revealed by magnetotelluric data

In order to investigate the three-dimensional structures of intrusive granite and the deep structure of the Darbut fault in the northwestern margin of the Karamay region, western Junggar Basin, China, new magnetotelluric data were collected along six profiles across the Darbut fault. The magnetotelluric data were processed using a robust estimation technique to obtain the magnetotelluric impedance. Then the off-diagonal components of the impedance tensor were inverted using a three-dimensional nonlinear conjugate gradient inversion technique, which was performed using open-source three-dimensional electromagnetic inversion software. The final three-dimensional model includes two major low-resistivity anomalies and two major high-resistivity anomalies. The first low-resistivity anomaly corresponds to the location of the Darbut fault, which indicates that metallic elements are abnormally enriched there. The second one is located beneath the Darbut fault, and it is most likely a magma channel in the middle crust. The two major high-resistivity anomalies are distributed on either side of the Darbut fault. We interpret them as Karamay rocks and Akebasitao rocks and suggest that they were formed in an extensional setting. The cross sections of three-dimensional magnetotelluric inversion result reveal that the Darbut fault has been reformed by the later magmatism, leading to the variation of its downward extent along its strike. Moreover, our inversion result also indicates that a magma channel exists in the middle crust of the region.     

新疆地区地震目录最小完整性震级和台网科学布局研究

地震目录的最小完整性震级M.是地震学中最基础、最重要的研究内容之一,也是地震观测台网效能评估的关键.本文对构造活动剧烈、地震活动水平高、台站地理分布复杂的新疆地区开展M研究,试图为该地区的地震危险性评估和台站科学布局等研究提供参考资料.基于新疆地震台网发展的5个阶段划分,采用基于G-R关系的交互式分析方法,研究了M.的...     

IASPEI91实用震相走时表及计算方法

解析了美国ASL提供ISPEI91走时表的存储结构。自己研制的方法与美方提供方法相结合，根据需要可以随意计算各种地震震相的到时或该震相与初至波的到时差。本软件在功能上完全满足目前台站的工作要求。将计算理论震相、震相到时差和汇编走时表功能集成在一个界面下，有利于台站工作，可以提高工作效率，为台站人员的地震监测和分析工作提供了方便。     

Construction and development of China digital seismological observation network

The seismological observation system in China has experienced rapid development over the Tenth Five-year Plan period. China Earthquake Administration (CEA) has completed the establishment of China digital seismological observation network. CEA has accomplished analog-to-digital conversion of the existing seismological observation systems and set up a number of new digital seismic stations. This indicates full digitization of seismological ob-servation in China. This paper presents an overview of the scale,layout principle and major functions of the up-dated national digital seismograph network,regional digital seismograph network,and digital seismograph net-work for volcano monitoring and mobile digital seismograph networks in China.     

海南地震应急数据共享与应用

从数据共享、数据处理、数据应用等方面分析了海南省地震应急数据共享服务的全过程,讨论了数据共享与应用在海南地震应急联动服务工作中的重要性。