GNSS-seismology for anthropogenic earthquakes

The high-rate GNSS has been proven to be an effective tool to describe moderate and strong natural earthquakes, whereas the much less addressed application is monitoring anthropogenic earthquakes, such as mining tremors, where the noise and displacements have similar values. Although the anthropogenic events have small magnitudes (usually below 4.5), they also have much shallower epicentres (depths up to 1-2 km). Therefore, the vibrations they cause are often felt and may have a dangerous impact on the ground, structures and infrastructure nearby.

Here we show that with the high-rate multi-constellation GNSS observations (GPS+Galileo), we can reliably detect the low-magnitude shallow anthropogenic earthquakes and characterise them in terms of displacements and velocities. Our filtering procedure is based on multiresolution analysis and successfully retrieves the small signal of ground vibrations. We analysed five mining tremors with magnitudes of 3.4-4.0 and presented the results from high-rate GNSS position changes calculated parallel with the PPP and variometric approach. The accuracy was very few millimetres for displacements and 1-2 cm/s for velocities. We obtained satisfying correlations with seismological data in correlation, peak values comparison and earthquake first epoch determination. Finally, considering the high-rate GNSS positioning noise level, we demonstrate the capacity to resolve the dynamic displacements from high-rate GNSS at the epicentral distance of about 7-8 km.