Preliminary Evaluation of Ground Motions from Earthquakes in Alberta

Abstract

Between 9 September 2013 and 22 January 2015, more than 900 seismic events in local magnitude ( M L) range 1–4 were detected and located in near‐real time by the new TransAlta/Nanometrics network in western Alberta, which commenced operation in the fall of 2013. The network comprises 27 three‐component broadband seismograph stations, located as shown in Figure 1, which act in cooperation with other real‐time seismograph stations operated by the Alberta Geological Survey (AGS) (Stern et al. , 2011) and the Geological Survey of Canada (GSC). There are additional campaign‐mode stations in the Canadian Rockies and Alberta Network (CRANE) network operated by the University of Alberta (Gu et al. , 2011). Figure 1. Locations of stations and study events in Alberta. Events that are considered to be blasts are designated by an x within the magnitude symbol. Note that the deformation front that marks the boundary of the Rocky Mountains is distinguishable by topography. In this study, we compile and analyze a ground‐motion database of 5% damped pseudospectral acceleration (PSA) from the signals recorded on the TransAlta/Nanometrics stations in order to gain an initial understanding of overall ground‐motion source, attenuation, and site characteristics in the region. A catalog of events is provided on www.inducedseismicity.ca (last accessed May 2015); the locations and initial magnitudes of events were obtained by Nanometrics (www.nanometrics.ca; last accessed May 2015). We processed the recorded time series as described in Assatourians and Atkinson (2010). Briefly, the velocity time series are corrected for glitches and trends, then filtered and corrected for instrument response in the frequency domain. Differentiation to generate acceleration time series is done in the frequency domain before conversion back to the time domain. Horizontal and vertical peak ground velocity and peak ground acceleration values are computed from peak amplitudes of instrument‐corrected time series, and 5% damped …