VLF/LF Amplitude Perturbations before Tuscany Earthquakes, 2013

作     者：Balaram Khadka Keshav Prasad Kandel Sudikshya Pant Karan Bhatta Basu Dev Ghimire 

作者机构：St. Xavier’s College Kathmandu Nepal Nepalese Center for Research in Physical Sciences (NCRPS) Kathmandu Nepal 

出 版 物：《Natural Science》 (自然科学期刊（英文）)

年 卷 期：2017年第9卷第12期

页      面：437-456页

学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学] 

主　　题：D-Layer VLF/LF Terminator Times SST SRT DLPT DLDT Night Time Fluctuation 

摘      要：The US Navy VLF/LF Transmitter’s NSY signal (45.9 kHz) transmitted from Niscemi, Sicily, Italy, and received at the Kiel Long Wave Monitor, Germany, was analyzed for the period of two months, May and June (EQ-month) of 2013. There were 12 earthquakes of magnitude greater than 4 that hit Italy in these two months,?of which the earthquake of 21st June having magnitude of 5.2?and a shallow focal depth of 5 km was the major one. We studied the earthquake of 21st of June 2013, which struck Tuscany,?Central Italy, (44.1713°N and?10.2082°E) at 10:33 UT, and also analyzed the effects of this earthquake on the?sub-ionos-?pheric VLF/LF signals. In addition, we also studied another earthquake, of magnitude 4.9, which hit the same place at 14:40 UT on 30th of June and had shallow focal depth of 10 km. We assessed the data using terminator time (TT) method and night time fluctuation method and found unusual changes in VLF/LF amplitudes/phases. Analysis of trend, night time dispersion, and night time fluctuation was also carried and several anomalies were detected. Most ionospheric perturbations in these parameters were found in the month?of June, from few days to few weeks prior to the earthquakes. Moreover, we filtered the possible effects due to geomagnetic storms, auroras, and solar activities?using parameters like?Dst index, AE index, and Kp index for analyzing the geomagnetic effects,?and Bz (sigma) index, sunspot numbers, and solar index F10.7 for analyzing the solar activities for the confirmation of anomalies as precursors.