Yang Shih-Sian, Potirakis Stelios M, Sasmal Sudipta, Hayakawa Masashi
Institute of Space Science, National Central University, 300 Jhongda Rd., Jhongli District, Taoyuan 32001, Taiwan.
Department of Electrical and Electronics Engineering, University of West Attica, 250 Thivon and P. Ralli, Aigaleo, GR-12244 Athens, Greece.
Entropy (Basel). 2020 Jun 17;22(6):674. doi: 10.3390/e22060674.
In order to have further evidence of the atmospheric oscillation channel of the lithosphere-atmosphere-ionosphere coupling (LAIC), we have studied criticality in global navigation satellite system (GNSS) surface deformation as a possible agent for exciting atmospheric gravity waves (AGWs) in the atmosphere and GNSS fluctuations in the frequency range of AGWs with the use of the natural time (NT) method. The target earthquake (EQ) is the 2016 Kumamoto EQ with its main shock on 15 April 2016 (M = 7.3, universal time). As the result of the application of the NT method to GNSS data, we found that for the one-day sampled GNSS deformation data and its fluctuations in two AGW bands of 20-100 and 100-300 min, we could detect a criticality in the period of 1-14 April, which was one day to two weeks before the EQ. These dates of criticalities are likely to overlap with the time periods of previous results on clear AGW activity in the stratosphere and on the lower ionospheric perturbation. Hence, we suggest that the surface deformation could be a possible candidate for exciting those AGWs in the stratosphere, leading to the lower ionospheric perturbation, which lends further support to the AGW hypothesis of the LAIC process.
为了获得岩石圈-大气-电离层耦合（LAIC）大气振荡通道的进一步证据，我们利用自然时间（NT）方法研究了全球导航卫星系统（GNSS）地表形变的临界性，将其作为激发大气中大气重力波（AGW）以及AGW频率范围内GNSS波动的一种可能因素。目标地震是2016年熊本地震，其主震发生在2016年4月15日（震级M = 7.3，协调世界时）。将NT方法应用于GNSS数据的结果表明，对于一日采样的GNSS形变数据及其在20 - 100分钟和100 - 300分钟这两个AGW频段的波动，我们在4月1日至14日期间（即地震前一天至两周）检测到了临界性。这些临界日期可能与之前关于平流层中明显的AGW活动以及较低电离层扰动的结果的时间段重叠。因此，我们认为地表形变可能是激发平流层中那些AGW的一个可能因素，进而导致较低电离层扰动，这进一步支持了LAIC过程的AGW假说。
