Effects of nearby large earthquakes on the occurrence time of the Tokai earthquake—An estimation based on a 3-D simulation of plate subduction—

Abstract. We analyze variations of the LF subionospheric signal amplitude and phase from JJY transmitter in Japan (F=40 kHz) received in Petropavlovsk-Kamchatsky station during seismically quiet and active periods including also periods of magnetic storms. After 20 s averaging, the frequency range of the analysis is 0.28–15 mHz that corresponds to the period range from 1 to 60 min. Changes in spectra of the LF signal perturbations are found several days before and after three large earthquakes, which happened in November 2004 (M=7.1), August 2005 (M=7.2) and November 2006 (M=8.2) inside the Fresnel zone of the Japan-Kamchatka wavepath. Comparing the perturbed and background spectra we have found the evident increase in spectral range 10–25 min that is in the compliance with theoretical estimations on lithosphere-ionosphere coupling by the Atmospheric Gravity Waves (T>6 min). Similar changes are not found for the periods of magnetic storms.

Download Full-text

Investigation of Pre-Earthquake Ionospheric and Atmospheric Disturbances for Three Large Earthquakes in Mexico

Geosciences ◽

10.3390/geosciences11010016 ◽

2020 ◽

Vol 11 (1) ◽

pp. 16

Author(s):

Christina Oikonomou ◽

Haris Haralambous ◽

Sergey Pulinets ◽

Aakriti Khadka ◽

Shukra R. Paudel ◽

...

Keyword(s):

Chemical Potential ◽

Atmospheric Model ◽

Satellite System ◽

Seismic Events ◽

Electron Content ◽

Total Electron ◽

Atmospheric Disturbances ◽

Global Ionospheric Maps ◽

Global Navigation Satellite ◽

Large Earthquakes

The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 September 2017 and 21 January 2016 respectively), while ionospheric variations during the entire year 2017 prior to 37 earthquakes are also examined. In particular, Total Electron Content (TEC) retrieved from Global Navigation Satellite System (GNSS) networks and Atmospheric Chemical Potential (ACP) variations extracted from an atmospheric model are analyzed by performing statistical and spectral analysis on TEC measurements with the aid of Global Ionospheric Maps (GIMs), Ionospheric Precursor Mask (IPM) methodology and time series and regional maps of ACP. It is found that both large and short scale ionospheric anomalies occurring from few hours to a few days prior to the seismic events may be linked to the forthcoming events and most of them are nearly concurrent with atmospheric anomalies happening during the same day. This analysis also highlights that even in low-latitude areas it is possible to discern pre-earthquake ionospheric disturbances possibly linked with the imminent seismic events.

Download Full-text

Eastern China continental lithosphere thinning is a consequence of paleo-Pacific plate subduction: A review and new perspectives

Earth-Science Reviews ◽

10.1016/j.earscirev.2021.103680 ◽

2021 ◽

pp. 103680

Author(s):

Pu Sun ◽

Pengyuan Guo ◽

Yaoling Niu

Keyword(s):

Eastern China ◽

Pacific Plate ◽

Continental Lithosphere ◽

Lithosphere Thinning ◽

Pacific Plate Subduction ◽

Plate Subduction

Download Full-text

Stress relaxation arrested the mainshock rupture of the 2016 Central Tottori earthquake

Communications Earth & Environment ◽

10.1038/s43247-021-00231-6 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Yoshihisa Iio ◽

Satoshi Matsumoto ◽

Yusuke Yamashita ◽

Shin’ichi Sakai ◽

Kazuhide Tomisaka ◽

...

Keyword(s):

Stress Relaxation ◽

Focal Mechanism ◽

Large Earthquake ◽

Static Stress ◽

Focal Mechanism Solutions ◽

Large Earthquakes

AbstractAfter a large earthquake, many small earthquakes, called aftershocks, ensue. Additional large earthquakes typically do not occur, despite the fact that the large static stress near the edges of the fault is expected to trigger further large earthquakes at these locations. Here we analyse ~10,000 highly accurate focal mechanism solutions of aftershocks of the 2016 Mw 6.2 Central Tottori earthquake in Japan. We determine the location of the horizontal edges of the mainshock fault relative to the aftershock hypocentres, with an accuracy of approximately 200 m. We find that aftershocks rarely occur near the horizontal edges and extensions of the fault. We propose that the mainshock rupture was arrested within areas characterised by substantial stress relaxation prior to the main earthquake. This stress relaxation along fault edges could explain why mainshocks are rarely followed by further large earthquakes.

Download Full-text

A Methodology of Workshops to Explore Mutual Assistance Activities for Earthquake Disaster Mitigation

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18073814 ◽

2021 ◽

Vol 18 (7) ◽

pp. 3814

Author(s):

Kazuki Karashima ◽

Akira Ohgai

Keyword(s):

Disaster Management ◽

Quantitative Evaluation ◽

Management Plan ◽

Suggested Method ◽

Disaster Mitigation ◽

Earthquake Disaster ◽

Support Tool ◽

Mutual Assistance ◽

Large Earthquakes

To minimize the damage caused by large earthquakes, mutual assistance activities between residents and rescue victims (i.e., to support residents who cannot evacuate individually) are important. To enhance these activities, the technologies and methods for creating a Community Disaster Management Plan (CDMP), based on the quantitative evaluation of mutual assistance abilities, are required. However, the lack of a method for it is a key issue. This study aims to develop a methodology of workshops for making CDMPs by using the developed support tool by the authors to explore and promote mutual assistance activities. Through the demonstration and examination of a Community Disaster Management Plan on actual districts, the findings mentioned in this article were obtained. Moreover, the usability of this method is shown. In particular, this method is effective at revising CDMPs, and raising resident awareness on the importance of mutual assistance. The suggested method can also improve the lack of techniques involved in promoting mutual assistance.

Download Full-text