An appraisal on the aftershock characteristics of the July 4, 2018 earthquake, ML=5.1, near Durres, Albania

Abstract

Statistical properties of the aftershock sequence of July 4, 2018 earthquake, ML=5.1, near Durrës, Albania are here described in time, space and magnitude by means of pvalue, Dc-value and b-value, respectively. We used 151 aftershocks with local magnitude ML1.3 between the time span of July 4, 2018 and September 29, 2018. Aftershock catalog has a time period of about 90 days. A probability model of aftershock sequence based on the combination of Gutenberg-Richter and Modified Omori laws is here described. In addition, fractal analysis was used to investigate spatial properties of the aftershock sequence. Mc-values were taken as 1.8 and bvalue was computed as 0.68±0.06 by maximum likelihood method. Temporal decay parameters of sequence were estimated asp=0.94±0.06, c=0.022±0.019, K=15.55±2.09 by considering the aftershocks with MLMc=1.8 and elapse time since mainshock as 0.0048 day. The smaller than 1.0 b-value might show a higher stress release to be built up over time and be released by next earthquakes. Also, the relatively small p-value might be due to the slow decay rate of the aftershock activity. Dc-value was estimated as 1.86±0.03 and it means that aftershocks show homogeneous distribution. Also, we estimated the number of large aftershocks that might follow the mainshock and we evaluated the probability of specific magnitude of aftershock. Probability for magnitude level of 4.3 was estimated as 67.88 % and the expected numbers of aftershocks for magnitude level of 2.5 was calculated as 19.66. Consequently, we suggested that aftershock hazard evaluation to be developed by considering the space-time-magnitude evaluations of aftershocks in this part of Albania