Ionosperic anomaly due to seismic activities – Part 1: Calibration of the VLF signal of VTX 18.2 KHz station from Kolkata and deviation during seismic events
Ionosperic anomaly due to seismic activities – Part 1: Calibration of the VLF signal of VTX 18.2 KHz station from Kolkata and deviation during seismic events
复制标题
地震活动引起的电离层异常 - 第 1 部分：加尔各答 VTX 18.2 KHz 站 VLF 信号的校准和地震事件期间的偏差
DOI：
10.5194/nhess-9-1403-2009
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发表时间：
2009
影响因子：
4.6
通讯作者：
S. Chakrabarti
中科院分区：
文献类型：
--
作者：
S. Sasmal;S. Chakrabarti
抽象的。长期以来，甚低频信号被认为提供了有关岩石层-电离层耦合的重要信息。为了建立电离层活动和地震之间的相互关系，如果有的话，我们需要了解全年的参考信号是什么。最好的机会是在太阳活动最小的时期，耀斑和太阳黑子的数量可以忽略不计，数据将主要受太阳的影响，变化将是由于正常的日落和日出效应。本文给出了太阳活动非常低的2005-2008年这四年中日出和日落终止点随一年中某一天变化的结果。这些终结器是位于加尔各答的印度空间物理中心接收站观测到的印度海军的18.2 khz VTX信号。总共使用了624天的数据来获得平均样地。如果观测偏离这一所谓的标准校准曲线，就会受到陆地(如地震)和地外事件(如太阳活动)的影响。我们给出了在16个月的周期内发生的偏差的例子，并表明与地震事件的相关性是显著的，通常最高偏差发生在地震事件之前的几天。对不止一个台站的这种偏差进行同时观测，可以提高地震的预报性。
Abstract. VLF signals are long thought to give away important information about the lithosphere-ionosphere coupling. In order to establish co-relations, if any, between the ionospheric activities and the earthquakes, we need to understand what the reference signals are, throughout the year. The best opportunity to do this is during the period of solar minimum where the number of flares and sunspots are negligible and the data would be primarily affected by the sun and variation would be due to normal sunset and sunrise effects. In this paper, we present the result of the sunrise and sunset terminators as a function of the day of the year for a period of four years, viz, 2005–2008 when the solar activity was very low. The terminators are for the 18.2 KHz VTX signal of the Indian Navy as observed from Indian Centre for Space Physics receiving station located in Kolkata. A total of 624 days of data have been used to obtain the mean plot. Any deviation of observations from this so-called the standardized calibration curve would point to influences by terrestrial (such as earthquakes) and extra-terrestrial events (such as solar activities). We present examples of deviations which occur in a period of 16 months and show that the correlation with seismic events is significant and typically the highest deviation takes place up to a couple of days prior to the seismic event. Simultaneous observations of such deviations from more than one station could improve the predictability of earthquakes.