Interpretation of seismic data and numerical modelling of fault reactivation at El Teniente, Reservas Norte sector

Abstract

Reservas Norte (RENO) is one of the panel caving sectors of El Teniente mines, owned by Codelco Chile. The sector has experienced mine induced seismicity for many years. The work presented in this paper focuses on seismic activity recorded between the period from January 2004 to July 2008. The interpretation of the seismic data revealed that the sources of elevated seismic hazard (large events) at RENO during this period could be attributed to four major geological structures: Falla G, Falla F, Falla C, Falla N1. In particular, the seismic response of the four structures to undercut blasting activities is examined in detail. The use of numerical modelling has shown that it is possible to simulate this response after calibrating the model against the cumulative seismic moment released by the faults, as mining advances towards them. This calibrated numerical model can then be used to forecast future seismic responses. The main product of this work is a tool that can be used to rank different undercutting rates and geometries in terms of seismic hazard.

Dynamic modelling of a mining-induced fault slip

“…It is admittedly ideal to develop a numerical model encompassing a fault on which asperities as shown in Figure 6-1 are modelled, and to conduct numerical analysis with a numerical simulation technique that can allow for the dynamic motion of the asperities colliding and moving apart. However, shear rupture due to fault-slip in underground mines extends to large areas (Hofmann & Scheepers, 2011;Ortlepp, 2000;Swanson, 1992), and the occurrence of fault-slip is strongly dependent upon mininginduced stress state (Alber et al, 2009;Potvin et al, 2010;Sjoberg et al, 2012) as well as in-situ stress state. Thus, constructing a mine-wide scale model is essential in order to simulate fault-slip induced by mining activities.…”

“…In the field of geophysics, Oglesby and Mai (2012) simulates dynamic shear rupture as a source of an earthquake that could occur on the North Anatolian Fault system in the Sea of Marmara, Turkey with a large-scale numerical model by means of numerical analysis software into which FEM is implemented. Potvin et al (2010) and Sjoberg et al (2012) use numerical analysis software, which employs a distinct element method (DEM), in order to simulate fault-slip that occurs along geological structures in underground mines.…”

“…Seismic source parameters are widely used to evaluate the magnitude of 67 mining-induced seismicity, and the seismic source parameters calculated from the data obtained by seismic network installed on the ground surface or in underground are compared with those computed from numerical analysis (Hofmann & Scheepers, 2011;Potvin et al, 2010;Sjoberg et al, 2012). In the present study, the following seismic parameters were adopted to investigate dynamic sliding behaviour: seismic moment, Mo, moment magnitude, Mw, and energy released during fault slip, Es.…”

“…It is the classical Mohr-Coulomb criterion that is used the most widely for the stability analysis of faults in underground mines (Alber et al, 2009;Hofmann & Scheepers, 2011;Potvin, Jarufe, & Wesseloo, 2010;Sjoberg et al, 2012;Sneilling et al, 2013) because of its simplicity. The failure criterion is expressed as follows:…”

“…Many studies have been conducted in order to examine an effect of mining activities, such as extraction of stopes, on the behaviour of faults or shear zones (Alber et al, 2009;Hofmann & Scheepers, 2011;Potvin et al, 2010;Sneilling et al, 2013). The studies have elucidated a relation between the progress of mining sequence and the occurrence of seismic events in terms of cumulative seismic moment, locations and areas of seismic events.…”