2015 年 4 月 25 日和 5 月 12 日尼泊尔地震前的大气和电离层异常观测

IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
C. P. Simha, K. M. Rao, R. K. Dumka
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引用次数: 0

摘要

摘要确定震前大气层和电离层异常具有重要的研究意义,但也会遇到困难,特别是对于震级、震源深度和震源机制不同的地震。本文利用大气和电离层参数研究了与尼泊尔地震(2015 年 4 月 25 日,M = 7.8 和 2015 年 5 月 12 日,M = 7.3)相关的大气和电离层扰动。电离层(垂直电子总含量 (VTEC))和大气层(外向长波辐射 (OLR)、云掩蔽、垂直温度梯度 (VTG))参数来自印度政府地球科学部印度气象局 (IMD) 的 IGS GPS 站和 INSAT 3D 数据。异常的 VTEC 信号在 2015 年 4 月 25 日事件发生前 3 天和 10 天以及 2015 年 5 月 12 日事件发生前 2 天和 6 天被发现。在尼泊尔地震的 51 天期间,确定了一天内的四分位数间范围(IQR)和相关的运行中值,作为 VTEC 信号的上限参考,可以清楚地观察到,与 IISC、HYDE、SGOC 和 URUM 等远距离台站相比,LCK-4、LHAZ 等最靠近震中的台站的总电子含量(TEC)从 UB(上限)的限制范围内有所增加。在这些地震之前,UB 观测到 VTEC 的相对振幅增加了 54-60%。利用 51 天期间的全球行星指数(Kp)和风暴时间扰动指数(Dst),对整个地磁暴状况进行了深入研究。采用 IQR 范围法分析其异常正负信号。我们没有发现地震期间地磁暴引起的地磁特征。垂直温度梯度在 4.3 至 23.2 K 之间变化。51 天的 OLR 日变化显示了地震前几天大气的良好异常响应。浅层地震提供了最佳耦合,从地震带释放出大量能量,可能是 VTEC 模式异常增强的一个原因。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Observation of Atmospheric and Ionospheric Anomalies before the Nepal Earthquakes on 25th April and 12th May 2015

Observation of Atmospheric and Ionospheric Anomalies before the Nepal Earthquakes on 25th April and 12th May 2015

Abstract

Identifying pre-seismic atmospheric and ionospheric anomalies is of research importance but also meets difficulties, especially for earthquakes with varying magnitudes, focal depths and focal mechanisms. In this paper, atmospheric‒ionospheric disturbances associated with earthquakes in Nepal (April 25, 2015, M = 7.8 and May 12, 2015, M = 7.3) are investigated using atmospheric and ionospheric parameters. Ionospheric (vertical total electron content (VTEC)) and atmospheric (outgoing long wave radiation (OLR), cloud mask, vertical temperature gradient (VTG)) parameters are archived from IGS GPS stations and INSAT 3D data from Indian Meteorological Department (IMD) of Ministry of Earth Sciences, Government of India. The abnormal VTEC signal was noticed 3 days and 10 days prior to April 25, 2015 event and 2 days and 6 days prior to the May 12, 2015 event. Inter-quartile range (IQR) and associated running median over one day were determined as the upper limit reference to a signature of VTEC for the 51-days period of the Nepal earthquake, it can be clearly observed that the total electron content (TEC) has increased from the limits of UB (upper bound) at the stations closest to the earthquake epicentre such as LCK-4, LHAZ than the far stations such as IISC, HYDE, SGOC and URUM. Prior to these earthquakes, UB observed a 54‒60% increase in relative amplitude of VTEC. The overall geomagnetic storm condition was thoroughly examined using the global planetary index (Kp) and storm time disturbance index (Dst) over the 51-days period. The IQR range method was used to analyse its abnormal positive and negative signals. We found no geomagnetic signatures caused by geomagnetic storms during the seismic regime The OLR varied from 240 to 340 watts/m2 observed 4 days before the event. The vertical temperature gradient varied from 4.3 to 23.2 K. Daily variations of 51 days for the OLR showed good anomalous atmospheric responses a few days before the event. The shallow depth of the earthquake gives the best coupling, releasing a large amount of energy from the seismic zones, and could be a causal factor in the enhancement of anomalous VTEC patterns.

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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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