与 2020 年 6 月 14 日印度古吉拉特邦卡奇地区地震(M = 5.3)有关的超低频地磁异常现象

IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Geotectonics Pub Date : 2024-06-21 DOI:10.1134/s001685212470016x
C. P. Simha, K. M. Rao
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引用次数: 0

摘要

摘要古吉拉特邦地区(印度)于 2020 年 6 月 14 日 14 时 43 分(世界协调时)在古吉拉特邦 Kachchh 县 Bhachau 市附近发生 5.3 级地震,震源深度 20 千米,震中位于北纬 23.38 度,东经 70.36 度。为了研究此次地震的前兆,我们分析了安装在 Badargadh 多参数地球物理观测站(MPGO)的感应线圈磁强计(LEMI-30)在 2020 年 1 月 1 日至 6 月 16 日期间的数据。该观测站距离此次地震的震中约 20 公里。我们观察到,在这次地震之前,LEMI-30 数据中的 Bx 和 By 分量的原始数据中出现了明显的地磁幅射。地震前 6 至 18 天和地震前 2 天分别出现了频率为 0.01 至 0.02 Hz 的地磁幅值脉冲。极化比(PR)分析显示,2020 年 6 月 11 日出现异常信号,极化比值增至 1.4。2020 年 6 月 10 日至 16 日,由于日地相互作用产生的行星指数(Kp)和扰动风暴时间指数(Dst)也非常低(Kp = 0.3 和 Dst = -6 nT)。为了了解地震过程的动态,还对磁数据进行了分形维度分析。分形维度值也与 PR 分析结果相吻合,后者显示 2020 年 6 月 11 日出现了类似的异常。对超短波地磁数据进行了进一步分析,在 10 至 45 秒的周期范围内应用带通滤波数据代替原始数据,得出了 Pc3 波段的 Z/X 振幅比。我们发现从 2020 年 6 月 10 日开始,Z/X 振幅比呈上升和下降趋势。在使用 EMD 技术重建的成分中检测到增强的极化比率,这与本次地震有关。研究清楚地表明,EMD 方法可用于隔离噪声,从而改进对同时出现的短期地磁变化/异常的识别。因此,在我们的研究中,我们明确区分了它们的来源,是外部的(日地相互作用)还是内部的(制备区域导电性的局部变化)。
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Anomalous ULF Geomagnetic Anomalies Associated with the June 14, 2020 Earthquake (M = 5.3) in Kachchh, Gujarat Region (India)

Abstract

Gujarat region (India) was struck by an earthquake of magnitude 5.3 on June 14, 2020 at 14:43 UTC near Bhachau city in Kachchh district in the state of Gujarat, with a depth of 20 km at the epicentre of 23.38° N, 70.36° E. In order to study the earthquake precursors for this event, data from the Induction Coil Magnetometer (LEMI-30) installed at the Badargadh Multi-Parameter Geophysical Observatory (MPGO) was analyzed for the period from January 1 to June 16, 2020. This station is located ~20 km from the epicentre of this earthquake. We observed that a clear geomagnetic burst was identified in the raw data of the Bx and By components in the LEMI-30 data before this earthquake. Geomagnetic amplitude bursts were identified 6 to 18 days and 2 days before this earthquake with a frequency of 0.01 to 0.02 Hz. Polarization ratio (PR) analysis revealed an anomalous signal on June 11, 2020 with PR values increasing to 1.4. The planetary index (Kp) and disturbance storm time index (Dst) due to the Sun‒Earth interaction are also very low (Kp = 0.3 and Dst = –6 nT) from June 10 to 16, 2020. In order to understand the dynamics of seismic processes, fractal dimensional analysis is also applied to magnetic data. Fractal dimension values also corroborate with the results of PR analysis, which showed a similar anomaly on June 11, 2020. The ULF geomagnetic data was further analyzed by applying the band-pass filtered data instead of the raw data in the period range from 10 to 45 seconds and derived the Z/X amplitude ratio in the Pc3 band. We found an upward trend and a downward trend from June 10, 2020. Enhanced polarization ratios were detected in the reconstructed components using the EMD technique which are linked to the current earthquake. It has been clearly demonstrated that the EMD method can be used to isolate noise and thus improve the identification of simultaneous short-term geomagnetic variations/anomalies. Therefore, in our study, we have clearly differentiated their origin, whether external (the Sun‒Earth interactions) or internal (local changes in conductivity in the area of the preparation).

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来源期刊
Geotectonics
Geotectonics 地学-地球化学与地球物理
CiteScore
1.90
自引率
9.10%
发文量
28
审稿时长
3 months
期刊介绍: Geotectonics publishes articles on general and regional tectonics, structural geology, geodynamics, and experimental tectonics and considers the relation of tectonics to the deep structure of the earth, magmatism, metamorphism, and mineral resources.
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