Hydrogeochemical Earthquake Precursors (On the Example of Areas of the Kamchatka Peninsula, Russia, and the Republic of Uzbekistan)

Abstract

Hydrogeochemical precursors of the earthquakes (HGCP) in changes of ion-salt and gas composition of underground waters from self-discharging wells and springs on the territory of Petropavlovsk-Kamchatsky test site, Kamchatka Peninsula, Russia and Tashkent test site, Republic of Uzbekistan are considered. There has been analyzed the connection of HGCP with parameters of earthquakes — with correlation between magnitudes and epicentral distances, as well as with values of specific density of seismic energy in the wave, intensity of ground shaking and other parameters of earthquake impact in the regions of observation. In Kamchatka wells HGCP were revealed before the earthquakes with Mw = 6.5 to 7.8 at epicentral distances de = 100 to 310 km at relatively narrow ranges of values of seismic energy density in the wave (0.1 to 0.3 J/m3), volumetric coseismic deformation of water-containing rocks (one to tens 10-9) and maximal velocities of seismic waves (3.5–7.7 cm/sec). HGCP took place in the zones with intensity of the earthquakes not less than 4 to 6 by MSK-64 scale and were confined to the intermediate zones of sources of future earthquakes. Duration of HGCP development and their appearance before the following earthquakes amount to 1 to 9 months, which allows using such precursors for prediction of time of strong earthquakes.

Preseismic Groundwater Ion Content Variations: Observational Data in Flowing Wells of the Kamchatka Peninsula and Conceptual Model

“…Hydrogeochemical anomaly in water from well M-1 manifested in increase of water mineralization by 30% and in change of hydrogeochemical water type due to relative increase of SO4 2− and decrease of HCO3 − concentrations (Figure 3b; blue rectangle). The chemical composition of water corresponded to Formulas: M0.19 (SO4 78 HCO3 20)/(Ca 56 Na 44)-in background conditions, that is, before precursor anomaly; M0.25 (SO4 87 HCO3 11)/(Ca 55 Na 45)-at extreme stage of precursor anomaly; anion and cation concentrations are expressed in %-mmol/dm 3 , M0.19 is water mineralization, g/dm 3 . Errors in chemical analyzes of individual water samples were O = 1-6%.…”

“…= 120 days, τ0 = 350 days and postseismic anomaly at t0 = 90 days, τ0 = 200 days according to (3). Blue line-observational data; blue dashed lines-intervals of Clconcentration changes, taking into account the determination error of ΔCl = 2% according to (1); solid lines-calculated changes of Clconcentration at precursory anomaly (red color) and postseismic anomaly (blue color); brown dashed line-the total effect of two processes at postseismic stage.…”

“…Observations of ion-salt groundwater composition in wells to search for hydrogeochemical earthquake precursors (HGCP) have been carried out for more fifty years in seismically active regions of the Earth, including Russia [1,2], Uzbekistan [3], China [4], India [5], Japan [6], Italy [7], Iceland [8] and other countries [9]. Such studies are carried out to obtain data on spatiotemporal manifestations of HGCP, depending on parameters of earthquakes and to assess the prospects for using HGCP for earthquake prediction.…”