Figure 2
(a) The injection volume of the UGS during the study period. The red dashed line indicates the start of the Hutubi UGS operation (June 2013). The operation was divided into five complete cycles and half of a sixth cycle (I–V and VIi) spanning the capacity expansion and stable operation stages. Each cycle includes two periods: the injection period (with subscript i, gray area) and extraction period (with subscript e, white area). (b) An M–t diagram of detected (gray dots) and relocated catalog (black dots) events. The cumulative number of the detected and relocated catalogs are represented by the black and gray lines, respectively. The red stars indicate the template events. An M–t diagram (c) and monthly seismic rates (d) for two clusters. The cumulative number and the average wellhead pressure are represented by the red (c) and green (d) lines, respectively. The M–t diagram (e) and monthly seismic rate (f) for the seismic events excluding the two clusters. The cumulative number is represented by the red curve.
