A Critical Review of Ground Based Observations of Earthquake Precursors

Abstract

We aim at giving a short review of the seismo-associated phenomena detected on ground that in recent years have been investigated as possible earthquake precursors. The paper comes together with a companion article–published on this same volume by Picozza et al., 2021–devoted to summarize the space-based observation of earthquake–precursors by satellites missions. In the present work, we give an overview of the observations carried out on ground in order to identify earthquake precursors by distinguishing them from the large background constituted by both natural non-seismic and artificial sources. We start discussing the measurements of mechanical parameters and variations of geochemical fluids detected before earthquakes; then we review thermal and atmospheric oscillations; finally, observations of electromagnetic and ionospheric parameters possibly related to the occurrence of impeding earthquakes are discussed. In order to introduce a so large field of research, we focus only on some main case studies and statistical analyses together with the main hypotheses and models proposed in literature in order to explain the observed phenomenology.

Looking for Earthquake Precursors From Space: A Critical Review

“…One of the most debated issue in the physics of earthquake precursors includes the role of the seismo-induced radon exhalation in the generation of electromagnetic disturbances (Wakita et al, 1980;Teng et al, 1981;Cicerone et al, 2009). It has been proposed that the enhancement of total rock surface due to failure would increase the emissions of radon and other gases from grains and migration (Conti et al, 2021). This would be in agreement with: 1) the enhancement of radon concentration observed in aftershocks and 2) some laboratory experiments (Koike et al, 2015) aimed at verifying the growth of radon emissions of granites under compressional stress.…”

“…Anyway, the radon exhalation seems cannot explain a direct generation of electromagnetic anomalies at higher frequency. We address the interested reader to the paper (Conti et al, 2021) published in this same issue, that provides a short review of models and ground based observations. In this framework, candidate precursor analyses have been performed on data from dedicated missions (DEMETER, CSES), multi-payload spacecraft (such as NOAA 14,15,16,17, other Sun-synchronous LEO missions, weather and Earth observation satellites), Swarm satellites and for ionospheric sounding (as those of the FORMOSAT series).…”

“…For the observations from ground of ionospheric preseismic phenomena, see Conti et al, 2021. For observations from space, in this section we just cite some of the earliest studies of plasma disturbances and observations from experiments different from DEMETER and CSES. Results from these latter missions will be discussed in the devoted DEMETER Satellite Observations and First Analyses From the CSES Satellite Mission.…”

“…Several authors [see Tronin (2006), Conti et al (2021) and references therein] have suggested that the earthquake preparation process can generate variation of temperature (induced by flow/exhalation of geochemical fluids in the deep lithosphere and/or by secondary effects of the friction and displacement along the seismic faults) that can affect the energy budget in the LAIC in seismic sequences (Qin et al, 2021). Only relatively few test campaigns have been carried out on ground and articles published about measurements of temperature variations before earthquakes that explains the small amount of this type of data and the large uncertainty on the subject (Cicerone et al, 2009).…”

“…In this framework, this article presents a review of the main observations, hypotheses and models about the phenomenology of earthquake precursors observed in space, which, in our opinion, are valuable insights -that deserve to be investigated with the utmost precision and highest statistical accuracy -of the coupling mechanism existing between the lithosphere and the near-Earth environment (De Santis et al, 2015). For a review about the main earthquake precursors observed on ground (and further references about groundspace multi-parametric analyses) the interested reader is addressed to the twin article of Conti et al (2021) in this same issue. The layout of the article is as follow.…”