Investigating Earthquake Source Scaling Laws in the Akhisar Seismic Zone

Abstract

Spectral earthquake source parameters like corner frequency, fmax, stress drop and source radius are important parameters in terms of an earthquake’s source properties. In this study, the source parameters of 40 local earthquakes (3.5≤M≤5.0) were calculated using Matlab-based codes. From 2011 to 2017 a database belonging to broadband earthquake stations for earthquakes occured near the location of the 12 September 2016 Akhisar (Manisa) earthquake was created from the Kandilli Observatory and Earthquake Research Institute seismic station network. Displacement and acceleration spectra including P and SH waves were analysed with a Brune ω-2 source model. A total of 40 earthquakes had 1097 waveforms investigated and parameters belonging to each earthquake were manually calculated. For each source parameter, mean values were calculated according to the number of seismic stations used for each earthquake. Observational spectra had damping effect removed using the Qs quality factor previously determined for the region. Seismic moment values obtained for the earthquakes varied from 0.19×1015 and 36.19 ×1015 Nm (3.5 ≤ Mw ≤ 5) with corner frequency values from 1.01 Hz to 5.07 Hz for P phase and 0.69 Hz to 2.63 Hz for SH phase. Additionally, calculations for SH phase in a circular fracture area varied from 0.72 km2 to 11.12 km2, with analyses of P phase calculated from 0.4 km2 to 9.42 km2. Noting the two phase calculations, the stress drop of the sources appeared to vary from 0.02 Mpa to 1.37 Mpa. In conclusion, these source parameters calculated at local scale revealed empirical relation functions with great importance to represent the region and as input for other scientific studies and were compared with results obtained from other similar studies in the literature.