The application of MEMS seismometers to regional-scale passive seismology: a case study of the Sercel WiNG nodes.

Micro ElectroMechanical Systems (MEMS) accelerometers have become increasingly common in geophysical studies. Despite this, no work has been done to assess the suitability of an array of MEMS sensors to low-frequency, regional-scale passive seismic studies. Consequently, a month’s-long deployment of twenty MEMS-based Sercel WING nodes, two Güralp CMG-ESPCDS and one 4.5 Hz geophone-Reftek system was undertaken to assess the performance of MEMS accelerometers in comparison to conventional seismometers. We show that the WiNG nodes reliably record over 100 Hz to 0.03 Hz, with a -136 dB broadband noise-floor between 100 – 1 Hz, and a 1/f noise-floor at frequencies below 1 Hz. The nodes accurately recorded earthquakes with epicentral distances ranging from 72° to 40 km. In particular, the low-period (c. 10 - 30s) surface waves of two teleseismic earthquakes were clearly resolved above the WiNG node’s noise floor. A set of three WiNG nodes deployed in a 3-component configuration provided an estimate of the crustal thickness beneath Oxford of 39.0 ± 2.0 km using the H-k stacking technique. This compares favourably with the estimate provided by the conventional 3-component ESPCD (37.9 ± 1.3 km) and aligns well with previous results in the literature. The MEMS-based systems have a number of clear advantages over conventional systems, including speed of deployment, cost, small size. The strong performance of the WiNG nodes during this study shows that these MEMS-based accelerometers are well-suited for passive seismology at a local, regional, and potentially larger scale.