Effects of Seismic Waves in Water Level Changes in a Well: Empirical Data and Models

Abstract

The high-precision water level measurements with a sampling interval of 5-10 min were carried out in 1996-2017 in the YuZ-5 well, Kamchatka. In the obtained time series, water level variations caused by the passage of seismic waves (hydrogeoseismic variations-HGSV) during 19 earthquakes with М w = 6.8-9.1 which occurred at epicentral distances of 80-14.6 thousand km are revealed. Based on the HGSV morphological features, four main types of these variations are distinguished: oscillations (I); short (up to tens of hours) water level rises (II) superimposed on oscillations; short rises (III); and long (1.5-3 months) drawdowns (IV). The dependence of the occurrence of the revealed GHSV types on earthquake parameters (magnitude and distance), specific energy density and maximum seismic wave velocity, and the amplitude-frequency content of ground motion is analyzed based on the records at a nearest seismic station. Based on several case studies, hydrogeodynamic processes of HGSV formation are investigated using numerical modeling. It is shown that the forced and free amplitude fluctuations in the water level (types I and II) can arise due to the enhancement of groundwater pressure variations in the well-water-bearing rock system during the passage of surface seismic waves with periods corresponding to the resonant frequency of the well (τ = 44.6 s). The rise in the water level in well lasting for tens minutes to hours (types II and III of HGSV variation) is caused by the short increase in pressure under violation of the steady water flow in the direct vicinity of the well; strong local earthquakes accompanied by ground shaking with intensity I msk-64 ≥ 5 cause sustained drawdowns (type IV) due to pressure drop with the amplitudes up to 0.1 bar within a radius of up to a few hundred meters from the well.

Hydrogeological Earthquake Precursors: A Case Study From the Kamchatka Peninsula

“…The e values were estimated by the formula logd e 0.48M w −0.33loge−1.4 (Wang, 2007;Wang and Chia, 2008) and used to evaluate the range of e variations for the earthquakes preceded by the HGPs in the wells of the Kamchatka Peninsula. Previously in (Wang, 2007;Wang and Chia, 2008;Wang and Manga, 2010;Kopylova and Boldina, 2020), the e values were applied to assess co-and postseismic phenomena in ground-and surface waters. In this work, the e values are used to assess the possible seismic impact of earthquake in the observation area with manifestations of hydrogeological precursors.…”

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

“…Figure 5 from paper [2] demonstrates the relationship between preseismic hydrogeochemical anomalies and magnitude and epicentral distance to wells of subsequent earthquakes. Distribution of specific density of seismic energy e [9,11,22,23] depending on earthquake parameters also shows in Figure 5. The e value is considered as a parameter of earthquake impact in area of a well with preseismic hydrogeochemical anomaly.…”

“…[20]. (ii) -e values were estimated by the formula logd e = 0.48M w − 0.33loge − 1.4 [2,[21][22][23]. (iii) -Medvedev-Sponheuer-Karnik scale, also known as 12-points MSK-64, is a macroseismic intensity scale used for evaluating shaking of Earth's surface based on observed effects in the earthquake area; the values of points are given for Petropavlovsk-Kamchatsky city.…”

Seismo-Hydrogeodynamic Effects in Groundwater Pressure Changes: A Case Study of the YuZ-5 Well on the Kamchatka Peninsula

“…The results of such studies were summarized in monographs [1,2]. In these monographs and in many other works [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], it was shown that during observations in piezometric wells equipped with level gauges or pressure sensors, various changes in the groundwater level and pressure were detected, mainly influenced by the seismic waves from the earthquakes. To a lesser degree, such studies investigated the changes in the groundwater pressure before the earthquakes (hydrogeodynamic precursors, HPs) as well as the effects of changes in the static stress state of water-bearing rocks during the ruptures in the earthquake sources (coseismic effects, CSEs).…”