{"title":"Seismic magnitude homogenization by unified regression method and its effect on seismicity parameters","authors":"Rohit Singh Patel, Ajay Kumar Sinha","doi":"10.1007/s10950-024-10197-5","DOIUrl":null,"url":null,"abstract":"<div><p>A homogeneous earthquake catalogue is necessary to conduct a thorough seismological investigation and improve seismic hazard assessment. Therefore, the present study intends to determine the influence of magnitude homogenization based on different regression methods on the seismicity parameters. The earthquake catalog of the Bihar, India region has been used for the study. An events data catalogue consisting of 4001 events has been compiled over the period 1911–2023. The data is primarily sourced from international and local databases have been assembled to provide a comprehensive overview of seismic activity within the study area. Empirical relationships have been derived between moment magnitude and commonly used local and global magnitude scales by performing non-linear regressions using chi-square regression method (CSQ) and ordinary least-square regression method (OLS). Measurement error for both dependent and independent variables of various data sets was calculated for the CSQ process. In order to address the non-linear nature of the correlations, we used curvilinear models, namely, the exponential model (EXP), which was recently introduced by the authors of the global catalogue supported by the global earthquake model (GEM) foundation. The use of CSQ method reduces the bias created by OLS method for defining the nonlinearity of the relationship. Seismicity parameters, including the magnitude of completeness (<i>M</i><sub><i>c</i></sub>) and <i>a</i> and <i>b</i> values of the Gutenberg-Richter recurrence model, have been calculated for homogenised undeclustered and declustered catalogue spanning five specific time periods. Declustering has been performed to isolate the foreshocks and aftershocks from the mainshocks. The observed changes in the <i>M</i><sub><i>c</i></sub> and <i>b</i> values are found to be dependent on the introduction of more recent data over time. The study area has been divided into eight seismogenic zones based on the geographic variations in earthquake occurrence and the prevailing tectonic conditions. The estimation of <i>M</i><sub><i>c</i></sub>, <i>b</i>, and <i>a</i> values has been conducted for each zone, and the analysis has been performed to examine the variations in these parameters. Derived equations serve as valuable tools for assessing and analysing seismic hazards in the north India and the central Himalayas region.</p></div>","PeriodicalId":16994,"journal":{"name":"Journal of Seismology","volume":null,"pages":null},"PeriodicalIF":1.6000,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Seismology","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s10950-024-10197-5","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
A homogeneous earthquake catalogue is necessary to conduct a thorough seismological investigation and improve seismic hazard assessment. Therefore, the present study intends to determine the influence of magnitude homogenization based on different regression methods on the seismicity parameters. The earthquake catalog of the Bihar, India region has been used for the study. An events data catalogue consisting of 4001 events has been compiled over the period 1911–2023. The data is primarily sourced from international and local databases have been assembled to provide a comprehensive overview of seismic activity within the study area. Empirical relationships have been derived between moment magnitude and commonly used local and global magnitude scales by performing non-linear regressions using chi-square regression method (CSQ) and ordinary least-square regression method (OLS). Measurement error for both dependent and independent variables of various data sets was calculated for the CSQ process. In order to address the non-linear nature of the correlations, we used curvilinear models, namely, the exponential model (EXP), which was recently introduced by the authors of the global catalogue supported by the global earthquake model (GEM) foundation. The use of CSQ method reduces the bias created by OLS method for defining the nonlinearity of the relationship. Seismicity parameters, including the magnitude of completeness (Mc) and a and b values of the Gutenberg-Richter recurrence model, have been calculated for homogenised undeclustered and declustered catalogue spanning five specific time periods. Declustering has been performed to isolate the foreshocks and aftershocks from the mainshocks. The observed changes in the Mc and b values are found to be dependent on the introduction of more recent data over time. The study area has been divided into eight seismogenic zones based on the geographic variations in earthquake occurrence and the prevailing tectonic conditions. The estimation of Mc, b, and a values has been conducted for each zone, and the analysis has been performed to examine the variations in these parameters. Derived equations serve as valuable tools for assessing and analysing seismic hazards in the north India and the central Himalayas region.
要进行全面的地震学调查和改进地震灾害评估,就必须有一个同质的地震目录。因此,本研究旨在确定基于不同回归方法的震级同质化对地震参数的影响。本研究使用了印度比哈尔地区的地震目录。地震事件数据目录包括 1911-2023 年间的 4001 次地震事件。这些数据主要来源于国际和本地数据库,已汇集成研究区域内地震活动的综合概览。通过使用卡方回归法(CSQ)和普通最小二乘法(OLS)进行非线性回归,得出了矩震级与常用的地方和全球震级标度之间的经验关系。在 CSQ 过程中,计算了不同数据集的因变量和自变量的测量误差。为了解决相关性的非线性问题,我们使用了曲线模型,即指数模型(EXP),该模型是最近由全球地震模型(GEM)基础支持的全球目录的作者提出的。CSQ 方法的使用减少了 OLS 方法在定义非线性关系时产生的偏差。地震参数,包括完整度大小(Mc)以及古腾堡-里克特复发模型的 a 值和 b 值,已针对跨越五个特定时间段的同质化无聚类和去聚类目录进行了计算。去聚类是为了将前震和余震从主震中分离出来。观测到的 Mc 值和 b 值的变化取决于随着时间推移引入的最新数据。根据地震发生的地理差异和当时的构造条件,将研究区域划分为八个地震带。对每个地震带的 Mc、b 和 a 值进行了估算,并对这些参数的变化进行了分析。推导出的方程可作为评估和分析印度北部和喜马拉雅山中部地区地震灾害的宝贵工具。
期刊介绍:
Journal of Seismology is an international journal specialising in all observational and theoretical aspects related to earthquake occurrence.
Research topics may cover: seismotectonics, seismicity, historical seismicity, seismic source physics, strong ground motion studies, seismic hazard or risk, engineering seismology, physics of fault systems, triggered and induced seismicity, mining seismology, volcano seismology, earthquake prediction, structural investigations ranging from local to regional and global studies with a particular focus on passive experiments.