Earthquake statistical performance due to increasing of the seismic network around Opak Fault, Yogyakarta

The seismic event in May 2006 underscored the critical necessity of continuous earthquake
monitoring. Observational enhancement through adding more stations is very crucial to obtain a more
refined data quality. From January 2009 to September 2019, BMKG PGR (Pusat Gempa Regional/Regional
Earthquake Centre) VII documented approximately 1847 seismic events with magnitudes from 0.9 to 4.9.
With the integration of additional seismic station into the array by December 2022, there was a notable
increase of 1418 recorded events in the same magnitude interval. The earthquake observation average is
increasing as well, from 15.4 events in a month to 20.5 events in a month. This study leverages this data to
assess the impact of augmenting seismic stations proximal to the Opak Fault on seismicity parameters within
that region. Employing ZMAP 6.0, a comparative analysis of seismicity parameters was conducted between
the earthquake catalog from January 2009 to September 2019 and the expanded catalog from January 2009
to December 2022. Declustering process result 1790 and 3141 main earthquake events in each catalog. This
research indicate that the inclusion of more stations significantly influences the Mc value and earthquake
density, however, it does not have a significant effect on the b and a-value.