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Brune Stress Drop, b-Value, and Modeling Through Finite Element Models (FEM) of Earthquakes that Occurred close to the 30 October 2016, Mw 6.3 Norcia Earthquake

Description: 

Previous investigations on the relationship between b-value and Brune stress drop often lead to opposite conclusions, going from a clear dependence of b-value on stress regime to a complete independence among b-value, fault mechanism and stress drop, suggesting that this issue deserves further investigation. The interaction between large events and aftershocks is also studied through finite element models (FEM): aftershocks of major earthquakes are considered to occur in response to stress variations caused by the main shock. The finite element method is useful to build a complex crustal model and provides a more comprehensive relationship between stress drop, stress regime and b-value. From the analysis of the earthquakes occurred close to the 30th October 2016, Mw 6.3 Norcia earthquake, we found that: (i) b-values estimated in the epicentral zone are greater than the estimated reference b-value for the same area; (ii) the correlation analysis between the main rupture propagation direction and the seismicity migration direction indicates that the maximum number of events with positive correlations are observed in the Norcia area, with 100% against 91% of the events located in the area affected by the Amatrice-Visso-Norcia 2016-2017 seismic sequence; (iii) for 82% (9 of 11) of the events that occurred in the Norcia area, 1 to 9 aftershocks of magnitude greater than 3.5 occurred along the main rupture propagation direction; (iv) the events located in the Norcia area show a stronger dependence of stress drop on seismic moment. These results suggest that in the Norcia area the correlation between the main direction of the rupture propagation and the direction of migration of the seismicity implies a possible increase of the degree of fracturing. The consequent decrease of stress drop correlates with the b-value observed in the area.

Session: Earthquake Source Parameters: Theory, Observations and Interpretations [Poster]

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Giovanna Calderoni

Student Presenter: No

Invited Presentation: 

Authors