Groundwater Ion Content Precursors of Strong Earthquakes in Kamchatka (Russia)

Abstract

The Kamchatka peninsula, located in the far east of Russia, is a geologically active margin where the Pacific plate subducts beneath the North American and Eurasia plates. This area is characterised by frequent and strong seismic activity (magnitudes reaching 8.6) and epicentres are generally distributed offshore along the eastern coast of the peninsula. For many years, hydrogeochemicals have been sampled with a mean interval of three days to measure the most common ions in the groundwater of five deep wells in the southern area of the Kamchatka peninsula. In the last decade, five earthquakes with M\ 6.5 have occurred at distances less than 250 km from these wells. These earthquakes were powerful enough for them to be considered as potential originators of precursors. In order to reveal possible precursors of these earthquakes, we analysed the groundwater ion contents. The quasi-periodic annual variation was filtered out, together with other slow trends, and then we smoothed out the high frequency fluctuations that arise from errors in a single measurement. When examining the data, we labelled each signal with an amplitude greater than three times the standard deviation as an irregularity and we made a first attempt at defining an anomaly as an irregularity occurring simultaneously in more than one parameter at each well. In a second definition we used the existence of an irregularity occurring simultaneously in each ion at more than one well. Then, on the basis of past results worldwide and the time interval between the earthquakes observed, we chose 158 days as the maximum temporal window between a possible anomaly and the subsequent earthquake. With the first anomaly definition we identified 6 anomalies with 4 possible successes and 2 failures. For the five earthquakes considered capable of producing precursors we obtained precursors in three cases. With the second anomaly definition we identified 10 anomalies with 7 possible successes and 3 failures and we obtained precursors in four of the five earthquakes. A schematic model explaining aspects of the complex relationship linking earthquakes and ion content anomalies is also presented.

Retrospective analysis for detecting seismic precursors in groundwater argon content

“…This case matches with the increase in the Argon content during June-July 1996 pointed out previously for W 3 (Fig. 2) and in Biagi et al (1999) for W 2 .…”

“…For many years, samples for hydrogeochemical analyses have been collected, with a mean sampling frequency of three days, in the form of the most common ions and gases in the groundwater of some deep wells and springs located in the southern area of the Kamchatka peninsula, where the capital city Petropavlovsk is located. The presence of possible precursors in the groundwater ions content on the occasion of the strongest earthquakes occurred in the area has been reported in Biagi et al (2000). On 21 June 1996 a shallow (1 km) earthquake with M=7.1 occurred at a distance of about 200 km from Petropavlovsk ( Fig.…”

Groundwater chemical anomalies connected with the Kamchatka earthquake (M=7.1) on March 1992

“…5c) can be considered middle term precursors of the March 1992 earthquake. In a previous study (Biagi et al, 2000b), more evident precursors of this type were pointed out at W 2 in the groundwater contents of some ions. It was proposed that some modification in the micro-fracturing processes or in the changes of the existing fissures, during the final stage of the preparatory phase of the earthquake, brought about the temporary mixing of different waters.…”

“…1 a single mark is used. In the past, different analyses were performed in order to reveal possible correlations between anomalous variations of the hydro-geochemical parameters and the seismic activity ( Bella et al, 1998;Biagi et al, 1999Biagi et al, , 2000aBiagi et al, , b, 2001aBiagi et al, , b, 2003Biagi et al, , 2004aKingsley et al, 1999Kingsley et al, , 2001). On this subject here we present a further investigation that has pointed out clear groundwater chemical anomalies on the occasion of the March 1992 earthquake (M=7.1).…”

Effects of seismic activity on the fluorescence signal of groundwater

“…Pre-seismic events such as thermal infrared emissions, surface temperature anomalies, radon irregularities and changes in physical and chemical properties of groundwater prior to major earthquakes have been reported (Tramutoli et al, 2005;Piroddi et al, 2014;Guangmeng, 2008, Ouzounov et al, 2006Singh et al, 2016;Biagi et al, 2000;Fidani et al, 2017). Anomalies in pH, conductivity or variations in ion content of groundwater can be explained through the interaction between positive holes and water (Grant et al, 2011).…”