Comparison of the low-cost MEMS accelerometers used by the Quake-Catcher Network and traditional strong motion seismic sensors

Accelerometers based on low-cost micro-electro-mechanical systems (MEMS) have improved swiftly, making the rapid deployment of dense seismic arrays possible. For example, the Quake-Catcher Network (QCN) makes use of MEMS-based tri-axial sensors installed in homes and businesses to record earthquakes, with almost 2000 participants worldwide. QCN utilizes an open-source distributed-computing system, called the Berkeley Open Infrastructure for Network Computing (BOINC), to retrieve waveforms from continuous or triggered recordings back to the QCN server. Furthermore, the QCN approach can also be used to augment existing seismic networks for rapid-earthquake detection purposes, as well as studies on seismic source- and site-related phenomena. Following the 3 September 2010 Mw7.1 Darfield earthquake, 192 QCN stations were installed in a dense array to record the on-going aftershock sequence in and around the city of Christchurch. We examine the peak ground motions recorded during a M5.1 aftershock and find that peak ground acceleration (PGA) is spatially variable, but with a clear decay in amplitude with distance. In general, closely located GeoNet and QCN stations report similar PGA. Several QCN stations were located within 1 km of existing GeoNet stations, providing an opportunity to compare time series and amplitude spectra. For these closely spaced pairs of stations, the amplitude spectra observed from the horizontal components are highly correlated with average cross-correlation coefficients of 0.9 or higher. In addition, we find the correlation coefficient decreases with increasing distance between station pairs. In future work we will compare the instrumental sensitivity between traditional and MEMS-based sensors by conducting shake table tests of five different types of MEMS sensors at the Albuquerque Seismic Lab.