分量式钻孔应变仪监测的附加应变场面应变分析

根据钻孔加衬模型和应变理论,得出分量式钻孔应变仪观测值不等于实际的线应变,但相互垂直的应变元件观测值之和与面应变成正比例.利用四分量钻孔应变仪的“自检”功能,对观测数据进行校正.以漳州地震台分量式钻孔应变仪资料为例,计算校正系数.校正前后的残差分析结果表明,校正效果明显.     

山西忻州地区YRY-4分量钻孔应变仪典型干扰因素分析

YRY-4分量钻孔应变仪具有高分辨力特点,在实际运行过程中能够记录到多种类型的外界干扰,表现为观测曲线突变或趋势异常。选取山西忻州地区5套四分量钻孔应变仪自运行以来的观测资料,基于各类干扰因素特征进行分析,结果表明：在日常运行中,影响钻孔应变观测的典型干扰因素主要有观测系统、自然环境、场地环境、人为干扰等;观测系统运行稳定,映震效能良好。     

3种钻孔应变仪记录的玛多MS7.4地震同震响应特征对比分析

针对2021年5月22日青海玛多MS7.4地震,采用3种型号的钻孔应变仪观测到的应变资料对比分析同震应变波,结果表明3种仪器记录同震的初动时间、波动幅度和持续时间等存在一定差别:在震中距相当的情况下,TJ型体应变仪和RZB型四分量钻孔应变仪存在波动幅度变化小、持续时间短的问题,难以从背景变化中区分同震响应,影响钻孔仪器同震规律研究; YRY?4型四分量钻孔应变仪波动幅度变化大,持续时间长,在映震效果上表现较为突出。     

四川四分量钻孔应变观测数据精度评价

利用邱泽华等给出的观测数据和回归分析方法,计算钻孔应变仪四分量元件的相对标定系数,并根据偏差计算自检内精度等指标,对观测数据进行质量评价。选取2017年四川四分量钻孔应变观测台网记录资料,结合四分量钻孔应变仪观测特点,计算并分析应变观测仪相对标定自检内精度,客观评价观测数据精度,结果发现,2017年仁和台四分量钻孔应变数据各月及全年相对标定系数K_i最大,偏差s最小,自检内精度数值最小,表明该台钻孔应变观测数据精度最高。分析认为,相对标定自检内精度可如实反映台站记录资料的可信度,可以更好、更客观地评价台站四分量钻孔应变观测资料质量。     

利用不同倾斜仪和应变仪检测地球自由振荡的对比与分析

中国地震局地壳形变观测台网布设有垂直摆倾斜仪、钻孔倾斜仪、洞体应变仪、分量式钻孔应变仪与体应变仪等地形变观测仪器。这些观测仪器均记录到了2011年日本M_W9.0大地震激发的自由振荡信号。本文分别利用单台数据和多台数据叠积,检测到_0S_3~_0S_(30)全部的球型自由振荡基频振型和_0T_3~_0T_(20)全部的环型自由振荡基频振型及部分谐频振型。此外,通过对这些检测结果的对比,分析了它们对不同自由振荡类型、不同频段的振型检测能力。分析发现垂直摆倾斜仪对球型自由振荡的检测结果最佳,且由于在低频段有较高的噪声干扰,钻孔倾斜仪无法检测到低阶的球型自由振荡。对于环型自由振荡的检测,分量式钻孔应变仪检测结果最佳。     

青海钻孔应变映震效能研究

利用青海省6套YRY-4分量钻孔应变仪2007—2015年的观测资料,将该地区符合扫描范围的地震从震前异常和同震特征两方面进行研究。结果显示:湟源、德令哈分量钻孔应变差应变曲线地震前大多有短期超差异常;分量钻孔应变仪的同震响应幅度与震级、震中距都有关。同一地震,多台仪器多数情况同震响应幅度与震中距成反比,少数成正比;一般单台仪器同震响应幅度与地震震级成正比关系,震级越大同震响应幅度越大;分量钻孔应变仪的同震响应延迟时间大多与地震震中距成正比,震中距越远同震响应延迟时间越长;分量钻孔应变仪同震响应持续时间与震级基本成正比,震级越大同震持续时间越长。     

高台地震台钻孔应变观测资料的分析

对高台地震台2008—2012年的YRY-4分量钻孔应变观测资料进行处理与分析,结果显示:高台台YRY-4分量钻孔应变仪运行良好,产出的观测数据连续、稳定、可靠;各个分量应变潮汐因子及相位变化相对稳定,相对误差较小,符合地壳形变观测技术规范要求;各个分量应变观测数据具有明显的周期特性和同向漂移变化。     

青海省钻孔应变资料典型干扰特征分析

分析了青海省境内6套YRY-4型分量钻孔应变仪观测资料的可靠性,详细研究了每套资料的干扰因素及特征,结果认为地下水和气压等因素是YRY-4型分量钻孔应变仪的主要干扰因素,但由于各观测点气候及地质水文条件的不同造成了干扰程度的差异.     

榆树沟分量钻孔应变资料可靠性检验与分析

利用固体潮调和分析和分量应变自检公式,对榆树沟地震台分量钻孔应变观测资料的可靠性进行检验分析。分析结果显示:(1)榆树沟分量应变仪两组互相正交的分量应变之和S_1+S_3、S_2+S_4的自检相关性达到0.999 1;(2)各分量(除东西向)观测精度均小于0.05,达到中国地震局形变I类台的标准。分析认为,除春季融雪对观测精度有影响外,该台分量钻孔应变资料有较高的可靠性。     

江宁地震台YRY-4型四分量钻孔应变仪可靠性检验

江宁地震台YRY-4型四分量钻孔应变仪于2006年12月安装运行,多年来积累了大量应变观测数据。采用Venedikov调和及相对标定等方法,从观测数据年变幅度、连续率及稳定性等方面,检验该台钻孔应变可靠性,结果表明,2009年以来,江宁地震台分量钻孔应变观测变仪器运行稳定、可靠,观测资料连续,符合地壳形变观测技术规范要求。     

乾陵地震台钻孔体应变观测资料分析

选取乾陵地震台2018—2020年钻孔体应变观测资料,进行完整性、年零漂和观测资料精度分析,通过采样调和分析,评价观测数据质量,并对自然环境变化、仪器系统故障和人为干扰对观测数据的影响进行分析,探讨该台钻孔体应变观测映震能力,认为： ①乾陵地震台体应变测项运行良好,观测数据质量较高; ②降雨、气压是影响体应变观测数据的主要干扰因素; ③体应变对全球7级以上、中国6级以上地震同震响应较明显,震级越大,同震响应持续时间越长。     

易县地震台分量钻孔应变观测数据分析

选取易县地震台YRY-4型分量式钻孔应变仪2012—2020年观测数据,进行Venedikov调和分析,并对2015—2020年四分量数据S₁、S₂、S₃、S₄进行自洽检验,发现应变观测数据连续性、可靠性较高。选取该台2018—2019年钻孔应变原始数据S₁、S₂、S₃、S₄,利用面应变S₁ + S₃、S₂ + S₄相关系数,分析河北省3次M_L≥4.0地震前数据异常变化,并利用剪应变S₁ - S₃、S₂ - S₄的大小,分析受抽水干扰的NE分量主应力方位角,判断干扰源方位,结果发现：①面应变与剪应变在地震发生前均会出现异常变化,且剪应变异常变化幅度较大,应与震中相对于观测井的位置有关;②对于受抽水干扰的钻孔应变NE分量,利用剪应变固体潮数据推算主应力方位角,可得干扰源在钻孔应变观测室NW80.96°方位,与实际位置存在一定偏差。     

钻孔差应变仪观测的苏门答腊大地震激发的地球环型自由振荡

我们率先用钻孔应变仪观测资料研究了地球自由振荡. 泰安地震台有差应变和体应变两种钻孔应变观测仪器,都观测到2004年12月26日苏门答腊大地震激发的地球自由振荡. 体应变仪观测到地球的球型振荡,而差应变仪观测到地球的环型振荡. 两种观测还记录到环型振荡与球型振荡相互的耦合作用. 观测也记录到明显的一些振型的谱线分裂现象. 用直接观测到的高质量的环型振荡资料求解了0T8～0T19等主要振型的Q值. 根据两个方向的剪应变观测数据,求解了环型振荡的最大剪应变方向,发现这个方向是相当稳定的. 这种研究表明,高精度钻孔应变观测仪是一种理想的地壳形变观测仪器,可以为地球自由振荡研究提供更丰富的信息.     

YRY-4型钻孔应变仪观测的P波剪应变

传统地震仪观测的是一个点的位移随时间的变化, 而应变仪观测的是位移的空间导数随时间的变化。 在四川姑咱台用YRY-4型四分量钻孔应变仪进行的每秒100次采样观测实验, 记录到三次地方震。 在这样高的采样率下, YRY-4型四分量应变仪观测数据保持了令人满意的自洽和足够高的信度。 观测表明, P波的应变不仅有面应变成分, 而且有剪应变成分。 这为澄清P波的性质, 给出了直接的观测证据。 根据弹性波理论, P波无旋转, 可以有体应变和剪应变成分。     

Observations of remote coseismic stress step-changes

The study on stress triggering and stress shadow is a frontier subject of current seismologic research. One of the problems presently encountered is the lack of reliable observation of real coseismic stress changes at locations remote to the epicenter. At Changping Station near Beijing, coseismic step-changes were recorded for the Mw6.3 Zhangbei quake on 10 January, 1998 and the Mw5.8 Zhangbei quake on 11 March, 1999, by a RZB borehole component strainmeter. Based on analyses of these recordings, this paper shows observed coseismic step-changes of the horizontal component of strain tensor. The strain step-changes reach the order of 10?8 and, correspondingly, stress step-changes reach as high as 10?4 MPa. The results are significantly higher than linear elastic theoretical values. However, as self-checking can be carried out with the 4 groups of data recorded by the 4-component strainmeter, it has proved that the results are reliable.     

Observations of remote coseismic stress step-changes

The study on stress triggering and stress shadow is a frontier subject of current seismologic research. One of the problems presently encountered is the lack of reliable observation of real coseismic stress changes at locations remote to the epicenter. At Changping Station near Beijing, coseismic step-changes were recorded for the M_w6.3 Zhangbei quake on 10 January, 1998 and the M_w5.8 Zhangbei quake on 11 March, 1999, by a RZB borehole component strainmeter. Based on analyses of these recordings, this paper shows observed coseismic step-changes of the horizontal component of strain tensor. The strain step-changes reach the order of 10^?8 and, correspondingly, stress step-changes reach as high as 10^?4 MPa. The results are significantly higher than linear elastic theoretical values. However, as self-checking can be carried out with the 4 groups of data recorded by the 4-component strainmeter, it has proved that the results are reliable.     

美国PBO计划:钻孔应变仪台网遭遇挑战

PBO(Plate Boundary Observatory)计划专门设计了一批钻孔应变仪台.网,在数百米距离内,安装2～3台仪器,以研究钻孔应变仪如何响应构造活动的信号,以及局部因素会造成何种干扰.本文收集了6个这样的台网的资料,给出了所有仪器数年的记录曲线,并对观测结果显示的地壳应变场做了简要的分析对比,发现6个试...     

一种新型分量式钻孔应变仪数据采集单元的设计及应用

本文根据新一代RZB型分量式钻孔应变仪的信号特点,设计了一种新型数据采集器.本设计采用了基于32位ARM的工控核心板以及嵌入式Windows CE操作系统作为软硬件平台,集成了总线数字信号与多通道高精度模拟信号的数据记录单元,实现了分量式钻孔应变观测系统的数据采集、存储、传输以及远程监控.实际测试表明,本采集系统具有高分辨率、低功耗等特点,主要参数指标达到了新型RZB型分量式钻孔应变观测系统信号采集要求.实际台站应用表明,本系统具有较高的可靠性和稳定性,可满足实际台站观测要求.     

INFLUENCE OF PUMPING ON FOUR-COMPONENT BOREHOLE STRAIN AT TAI'AN SEISMIC STATION AND ITS INTERFERENCE MECHANISM

Four-component borehole strainmeter (FCBS) is one kind of high-precision borehole strain observation instruments invented in China. As a kind of near-surface deformation observation instrument, FCBS is also easily disturbed by the external environment factors. As a common factor, pumping has significant influence on FCBS observation. Existing studies mostly identify the pumping interference from the perspective of observation curve morphology, relatively few studies focus on its interference mechanism. In order to truly capture earthquake precursor information, it is necessary to study the interference mechanism. In recent years, RZB-3 type FCBS at Tai'an seismic station has been seriously affected by pumping, so it is necessary and also feasible to study the interference mechanism of pumping. Since the influence of pumping interference on borehole strainmeter is common, this work would be very practical and be used for reference by other borehole strain observation stations. We find that the original observation curves and observed surface strain, shear strain from RZB-3 type FCBS at Tai'an seismic station have the characteristics of synchronous change with the borehole water level, in which the linear correlation coefficient between the two observed shear strain curves and borehole water level reached 0.70 and 0.82 respectively. We further find that the principal strain direction of borehole and borehole water level after normalization meet the nonlinear function as y=1.217arctan(x)^0.224-0.284. The above phenomenon indicates that the observation of RZB-3 type FCBS at Tai'an seismic station is significantly affected by the borehole water level, and the influence is more obvious and the gradient is larger at the stage of low water level. Pumping interference often appears in low water level stage and changes the rock pore pressure state. Statistics show that pumping interference affects the borehole strain state. To investigate the interference mechanism of pumping to RZB-3 type FCBS at Tai'an seismic station, we take a known pumping as an example, in which we study the principal strain state of the borehole in three periods of normal pumping, interruption of pumping and resuming pumping respectively. During each period, we solve 3 parameters of the principal plane strain state, i.e. the maximum principal strain rate, the minimum principal strain rate and the maximum principal strain direction from four observation equations of FCBS by nonlinear iterative least squares algorithm. On the other hand, concentrated load model (CLM) is used to simulate the mechanical mechanism of pumping. Firstly, the depth of FCBS relative to pumping source and the concentrated load at pumping source are inversed, then, the strain state surrounding the pumping well, including the state at RZB-3 borehole, is simulated by forward modeling. By comparing these results, we find that: (1)The concentrated load at pumping source inversed by CLM during periods of normal pumping and resuming pumping are both located at or near the bottom of the pumping well, which is consistent with the actual situation, indicating that mechanism and degree of the influence of pumping on borehole strain are well simulated by CLM. (2)The observed strain state is consistent with the simulation result of pumping interference by forward modeling, indicating that the principal strain state of borehole calculated based on observation of FCBS reflects the true strain state of borehole under different pumping states.(3)The inversed concentrated load at pumping source during pumping periods is significant greater than the load of the pumped water, indicating that the pumping process has more significant influence on the pore pressure of rocks than the load of the pumped water. Even though CLM is an approximate simulation since it's based on some elastic assumptions, the interference mechanism of pumping on RZB-3 type FCBS at Tai'an seismic station is well explained, which is maybe very helpful for studying the influence of pumping interference on other deformation instruments, locating the unknown pumping source and studying the characteristics of pore pressure of rocks.