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首页> 外文期刊>Journal of geodynamics >Observational signatures of unusual outgoing longwave radiation (OLR) and atmospheric gravity waves (AGW) as precursory effects of May 2015 Nepal earthquakes
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Observational signatures of unusual outgoing longwave radiation (OLR) and atmospheric gravity waves (AGW) as precursory effects of May 2015 Nepal earthquakes

机译：不寻常的长波辐射（OLR）和大气重力波（AGW）作为2015年5月尼泊尔地震的先兆效应的观测特征

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摘要

Earthquake preparation processes may start 1-30 days before its actual occurrence. Measurements of outgoing longwave radiation (OLR) and detection of the presence of atmospheric gravity waves (AGW) in very low frequency (VLF) radio signals can be used as tools to identify such processes. We studied these signals monitored prior to a recent major earthquake that occurred in Nepal at southeast of Kodari on May 12, 2015 at 12:50 pm local time (07:05 UTC) with Richter scale magnitude of M = 7.3 and depth 10 kin (6.21 miles). It was preceded by another major earthquake on April 25, 2015 with magnitude M = 7.9. First, to study the effects of seismic events on OLR, we used NOAA/IR daily (two degree gridded) data from April 16 to May 30, 2015 and followed the method of Eddy field calculation mean to find pre-seismic anomalies. We found singularities in Eddy field OLR curves around the earthquake epicenter starting 3 days prior to the earthquake days and disappearance of such singularities after the events. Such singularities can be associated with a large amount of energy released by the earthquakes. Second, we analyzed very low frequency (VLF) data recorded at Ionospheric and Earthquake Research Centre (IERC) of Indian Centre for Space Physics transmitted from JJI (22.2 kHz) station of Japan. We looked for the presence of atmospheric gravity waves in the ionosphere which can be considered as an important factor in finding seismo-ionospheric correlations. We performed both fast Fourier transform (FFT) and wavelet analysis on the signal and found significant presence of such waves (periods of almost 1 h) four days before the earthquake.
机译：地震准备过程可能在实际发生之前的1-30天开始。可以将发出的长波辐射（OLR）的测量和非常低频（VLF）无线电信号中大气重力波（AGW）的存在检测用作识别此类过程的工具。我们研究了在2015年5月12日当地时间12:50 pm（07:05 UTC）发生在尼泊尔Kodari东南部的一次大地震之前监测到的这些信号，里氏震级为M = 7.3，深度为10 kin（ 6.21英里）。在此之前，于2015年4月25日再次发生了M = 7.9级的地震。首先，为了研究地震事件对OLR的影响，我们使用了2015年4月16日至5月30日的每日NOAA / IR（两度网格化）数据，并按照涡流场计算的方法寻找地震前异常。我们在地震发生前3天开始，在震中附近的涡流场OLR曲线中发现了奇点，并在事件发生后这种奇点消失了。这种奇异性可能与地震释放的大量能量有关。其次，我们分析了从日本JJI（22.2 kHz）站发射的印度空间物理中心电离层和地震研究中心（IERC）记录的极低频（VLF）数据。我们寻找了电离层中大气重力波的存在，可以将其视为发现地震-电离层相关性的重要因素。我们对信号进行了快速傅里叶变换（FFT）和小波分析，并在地震发生前四天发现了此类波的大量存在（近1小时的周期）。

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