2021 Alaska Earthquake: entropy approach to its precursors and aftershock regimes

Abstract. For the first time, an entropy analysis has been made in Alaska, a seismic-rich region located in a subduction zone that shows a nontrivial behavior: the subduction arc changes the seismic activity from the eastern zone to the western zone, showing a decrease in this activity along the subduction. We analyze this zone through the Tsallis entropy and the mutability (or dynamic entropy). The data set used for this analysis was measured between 2000 and 2023, considering 19549 seismic events. We have found an agreement between the results for the two entropies. We have followed the value of the q parameter of the Tsallis entropy, finding values between 1.70 and 1.85, in concordance with values previously found in other seismic regions of the planet. Also, the values of the q-parameter tend to decrease over time but show an increase before the main earthquakes. Mutability also shows a tendency to decrease over time and an increase previous to the main earthquakes. To deeply analyze this zone, we divided the region into four sub-zones. The results show how mutability can identify the seismic activity in each zone. This study shows how an entropy approach can shed light on understanding the seismicity in subduction zones.