Calculating Skempton constant of aquifer from volume strain and water level response to seismic waves at Changping seismic station

Abstract

Based on linear poroelastic theory of ideal poroelastic media, we apply the mathematic expression between pore pressure and volume strain for well-aquifer system to analyzing the observed data of water level and volume strain changes aroused by Sumatra M S 8.7 (determined by China Seismic Networks Center) seismic waves at Changping, Beijing, station on December 26, 2004 from both time and frequency domain. The response coefficients of water level fluctuation to volume strain are also calculated when seismic waves were passing through confined aquifer. A method for estimating Skempton constant B is put forward, which provide an approach for understanding of the characteristics of aquifer.

Reaearch on Skempton’s coefficient B based on the observation of groundwater of Changping station

“…As calculated above, the value of B of Changping station is 0.850 5, it is approximately identical with 0.804, which is calculated through the relationship between the water level and the volume strain with the high frequency domain data when the Sumatra earthquake happened (Yan et al, 2008). If we choose different lengths of time to calculate the Skempton's coefficient B in a relatively stable state, the results will be almost the same ( Figure 5).…”

“…Barometric pressure data are observed in Changping station via barometer once a day. Tidal strain data are calculated via Mapsis software (Wu et al, 2006;Zhang, 2005;Yan et al, 2008).…”

“…Yan et al (2008) got the Skempton's coefficient B of Changping station with this method based on the data of the Sumatra earthquake, and the correlativity between the water level and the volume strain in the high frequency domain at the time of the Sumatra earthquake is fairly well. They achieved that the value of B in Changping station is 0.804.…”

“…Generally, the value of B was measured via experiment of rock physics and was considered as a constant for a specific rock type (Rice and Cleary, 1976;Roeloffs and Rudnicki, 1984;Roeloffs, 1996). Recently, scientists calculated the value of B by using water level observation data as well as barometric pressure and volume strain in well confined aquifer system under the undrained condition (Chadha et al, 2008;Sil, 2006;Kano and Yanagidani, 2006;Yan et al, 2008).…”

Electric and Electromagnetic Signals Under, on, and Above the Ground Surface at the Arrival of Seismic Waves

“…Based on early observations and theoretical work, a close coupling dynamics is well known to exist between the seismic acceleration and the pore pressure or water level (Muire-Wood and King, 1993; Kano and Yanagidani, 2006;Yan et al, 2008). This coupling dynamics must be valid in our geohydraulic system presented in Figure 16a.…”