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Entropy Approach to the 2021 Alaska 8.2 Earthquake

Description: 

The year 2021 was abundant in large earthquakes worldwide and the most important was the one of Alaska, Mw 8.2, which generated important aftershock activity. In this paper, we use Tsallis Entropy, Shannon Entropy, and Mutability to categorize the various stages of the phenomenon: a) random seisms; b) increase (decrease) of Tsallis entropy (mutability) years/months before the big earthquake; c) several seisms with magnitude close or over 7.0; d) a long aftershock regime lasting to present days. From the entropy point of view, we find similarities and differences in this behavior compared to that of the recently reported analysis of the Mw 8.1 earthquake of Iquique on April 1, 2014 [1].

We mainly conducted the analysis on the magnitude sequence from 2000-01-01 to 2023-12-31 obtained from the USGS web page. It is clearly appreciated how Tsallis entropy raises during 2019 in parallel to the decrease in mutability. Then, they abruptly reverse this behavior on the occurrence of the large earthquakes of 2020. However, Tsallis entropy (mutability) quickly increases (decreases) its value to the levels previous to this earthquake within a matter of months, only to sharply collapse (raise) for the 8.2 earthquake of 2021. It soon recovers, reaching the levels previous to the 2020 seisms, which is a worrisome sign. Shannon entropy heels the results for mutability, which is preferred because of its clearer results in perfect agreement with those got by Tsallis entropy. We can also do the analysis using the interval sequence (time between successive seisms) which is complementary to the one based on magnitudes. The combination of these results define a powerful technique able to shine light on the seismic activity years prior to major quakes and could be a potential indicator for categorizing seismic risk areas.

[1] Tsalllis Entropy and Mutability to Characterize Seismic Sequences: The Case of 2017-2014 Northern Chile Earthquakes. Denisse Pasten, Eugenio E. Vogel, Gonzalo Saravia, Antonio Posadas, and Oscar Sotolongo, Entropy 25 (2023) 1417 (https://doi.org/10.3390/e25101417).

Session: Numerical Modeling in Seismology: Developments and Applications - III

Type: Oral

Date: 5/1/2024

Presentation Time: 02:30 PM (local time)

Presenting Author: Eugenio

Student Presenter: No

Invited Presentation: 

Authors