Multifractal and monofractal characteristics of ULF magnetic fields in Kachchh region, Gujarat, India: Prospects for earthquake precursor detection

IF 1.9 4区地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS

Journal of Atmospheric and Solar-Terrestrial Physics Pub Date : 2025-02-19 DOI:10.1016/j.jastp.2025.106478

Sushanta Kumar Sahoo, Madhusudhanarao Katlamudi, Chandra Sekhar Pedapudi

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引用次数: 0

Abstract

Understanding electromagnetic emissions linked to earthquakes is critical for advancing precursor studies, yet research remains limited in seismically active regions like Kachchh, Gujarat, India. This study investigates Ultra-Low Frequency (ULF) magnetic field variations recorded over eight months (January 1–August 13, 2012) at the Multi-parametric Geophysical Observatory (MPGO) in Desalpar (23.742°N, 70.686°E). The analysis focuses on their connection to a magnitude 5.1 earthquake near the observatory on June 20, 2012. Data from a Digital Fluxgate Magnetometer (DFM) were analyzed using Detrended Fluctuation Analysis (DFA) and Multifractal Detrended Fluctuation Analysis (MFDFA) to explore scaling properties in the 0.001–0.1 Hz frequency range. Periodogram analysis identified diurnal and semi-diurnal periodicities, removed using Empirical Mode Decomposition (EMD) to isolate aperiodic signals. DFA results showed non-uniform fluctuation functions with scaling exponent variations prior to the earthquake on June 20, 2012. Notably, the instability index (β) increased in the H-component six days before the event (June 14, 2012), in the D-component on June 17–18, 2012, and in the Z-component one day before (June 19, 2012). MFDFA revealed long-range power-law correlations, with differences in multifractal spectra between observed and shuffled time series, indicating long-range correlations drive multifractality. Surrogate analyses confirmed these correlations while reducing Gaussian characteristics. The multifractal spectrum of H, D, and Z components widened during seismically active phases compared to quiet phases, emphasizing the utility of multifractal analysis in detecting ULF magnetic field instabilities. Abnormal time dynamics in the multifractal characteristics of the H- and Z-components were observed shortly before the earthquake on June 20, 2012. This research highlights the potential of such methods for earthquake monitoring and early-warning systems in active seismic regions.

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印度古吉拉特邦Kachchh地区ULF磁场的多重分形和单分形特征：地震前兆探测的前景

了解与地震有关的电磁辐射对于推进前兆研究至关重要，然而在印度古吉拉特邦的Kachchh等地震活跃地区，研究仍然有限。本文研究了迪萨帕尔（23.742°N, 70.686°E）多参数地球物理观测站（MPGO）在8个月内（2012年1月1日至8月13日）记录的超低频（ULF）磁场变化。分析的重点是它们与2012年6月20日天文台附近发生的5.1级地震的联系。采用去趋势波动分析（DFA）和多重分形去趋势波动分析（MFDFA）对数字磁通门磁强计（DFM）数据进行了分析，探讨了0.001 ~ 0.1 Hz频率范围内的标度特性。周期图分析确定了日周期和半日周期，使用经验模式分解（EMD）去除非周期信号。DFA结果显示，2012年6月20日地震前的波动函数不均匀，呈标度指数变化。值得注意的是，h分量（2012年6月14日）、d分量（2012年6月17-18日）和z分量（2012年6月19日）的不稳定指数（β）分别在事件发生前6天、6月14日和6月19日有所增加。MFDFA显示了长期幂律相关性，观测和洗牌时间序列之间的多重分形谱存在差异，表明长期相关性驱动多重分形。替代分析证实了这些相关性，同时降低了高斯特征。H、D和Z分量的多重分形谱在地震活跃阶段比安静阶段变宽，强调多重分形分析在超低频磁场不稳定性检测中的实用性。在2012年6月20日地震发生前不久，观测到H分量和z分量多重分形特征的异常时间动态。这项研究突出了这种方法在地震活跃区的地震监测和预警系统中的潜力。

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来源期刊

Journal of Atmospheric and Solar-Terrestrial Physics 地学-地球化学与地球物理

CiteScore

4.10

自引率

5.30%

发文量

审稿时长

6 months

期刊介绍： The Journal of Atmospheric and Solar-Terrestrial Physics (JASTP) is an international journal concerned with the inter-disciplinary science of the Earth''s atmospheric and space environment, especially the highly varied and highly variable physical phenomena that occur in this natural laboratory and the processes that couple them. The journal covers the physical processes operating in the troposphere, stratosphere, mesosphere, thermosphere, ionosphere, magnetosphere, the Sun, interplanetary medium, and heliosphere. Phenomena occurring in other "spheres", solar influences on climate, and supporting laboratory measurements are also considered. The journal deals especially with the coupling between the different regions. Solar flares, coronal mass ejections, and other energetic events on the Sun create interesting and important perturbations in the near-Earth space environment. The physics of such "space weather" is central to the Journal of Atmospheric and Solar-Terrestrial Physics and the journal welcomes papers that lead in the direction of a predictive understanding of the coupled system. Regarding the upper atmosphere, the subjects of aeronomy, geomagnetism and geoelectricity, auroral phenomena, radio wave propagation, and plasma instabilities, are examples within the broad field of solar-terrestrial physics which emphasise the energy exchange between the solar wind, the magnetospheric and ionospheric plasmas, and the neutral gas. In the lower atmosphere, topics covered range from mesoscale to global scale dynamics, to atmospheric electricity, lightning and its effects, and to anthropogenic changes.