Seismic instruments: article

On problems of detecting blasts in earthquake catalogs using Turkey and Iran as an example
Schmidt Institute of Physics of the Earth, Russian Academy of Sciences
Journal: Seismic instruments
Tome: 57
Number: 1
Year: 2021
Pages: 69-82
UDK: 550.34
DOI: 10.21455/si2021.1-5
Аnnotation file
Bibliographic list
Keywords: earthquake catalog, blast catalog, discrimination between earthquakes and blasts, diurnal periodicity of earthquakes, weekly periodicity of earthquakes, Turkey earthquakes, Iran earthquakes
Аnnotation: The catalogs of weak seismic events (M<4) in Turkey and Iran were analyzed to identify signs of their contamination by blasts. A well-pronounced predominance of the number of seismic events and a decrease in their average magnitude in the period from 10:00 to 17:00 local time were found. The epicenters of seismic events that occurred in this time interval at depths of less than 3 km are located much more compactly than other seismic events. Such factors can be considered as evidence of contamination of earthquake catalogs by road, mine and quarry blasts. The presence of such an anthropogenic effect in the catalogs of earthquakes is also confirmed by the presence of a well-defined weekly periodicity of seismic events. It manifests itself in the form of a significant weakening of the discussed daytime extremum on Saturday and Sunday in Turkey and on Friday in Iran. Using the example of Turkey, where the observation service attempted to separate blasts and earthquakes in the catalog of seismic events, it is shown that in the thus cleared earthquake catalog, the prevalence of seismic events in the daytime over their number at night is still observed. The opposite effect was also revealed - the presence of earthquakes in the blast catalog, i.e. there is a mutual contamination of the catalogs of earthquakes and explosions. However, it cannot be ruled out that the relative increase in the number of earthquakes in the daytime is only partly due to the presence of unidentified explosions due to imperfect algorithms for discriminating blasts and earthquakes. The daytime extremum of the number of earthquakes can be partially conditioned by the occurrence of additional weak earthquakes excited by relatively strong blasts, i.e. the triggering effect of explosions on the natural process of seismogenesis. The results obtained show that when working even with those catalogs of earthquakes that are designated by their authors as cleared of blasts, it is necessary to carry out preliminary studies of catalogs in order to assess their contamination by blasts.