Identifying anthropogenic seismic events generated in western Romania using statistical approaches and novel waveform processing techniques

Seismicity in western Romania is the result of tectonic processes that continuously shaped the landscape generating a fractured crust, which showed significant movements as a result of overall tectonic stress in the area as well as secondary effects such as erosion or lateral density fluctuations. At the same time, this region has an important natural resource, being identified here various deposits that have been intensively explored lately. The exploitation of these resources, as well as the development of the infrastructure in the region, led to the generation of anthropogenic seismic events. Due to the recent improvement of the Romanian Seismic Network, the coverage with seismic stations increased and these events were detected and located as natural tectonic events, contaminating the Romanian earthquakes (ROMPLUS) catalog.

To eliminate anthropogenic event contamination in the ROMPLUS catalog, we ran a complex statistical approach on the catalog data. In addition, to build a robust discriminant, we further applied cross-correlation and spectral analysis algorithms on the seismic waveforms recorded between 2014 and 2021 by the Surduc (SURR) and Gura Zlata (GZR) stations, which are located in the proximity of the major clusters of seismic events.

Our results showed a good distinction between tectonic and anthropogenic events and revealed that most of the clustered events are located near the explorations sites. We also noted that most of the events occurred during working hours. At the same time, the high similarity among these events indicates the existence of repetitive seismic sources.