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Aftershock Sequence of Türkiye Doublet Illuminates Complexity of Fault Structure and Delineates Frictional Heterogeneity

Description: 

Two back-to-back damaging earthquakes hit Türkiye on February 6^th, 2023. A Mw 7.8 earthquake ruptured southwestern part of East Anatolian Fault Zone (EAFZ). And a Mw 7.6 event struck about 10 hours later in Sürgü fault, north of EAFZ. Sadly, this doublet has caused severe structural damage in Türkiye and Syria with more than 55,000 fatalities.

Both events are producing prolific aftershock activity illuminating fault geometry and structures that may have played important roles in earthquake nucleation and rupture propagation. We use 44 broadband stations covering the aftershock region and analyze continuous seismic data for the entire month of February, including 5 days before the mainshocks and 23 days after. We apply a streamlined workflow containing Phase picking, Association, Location and Matched filter (PALM) [Zhou et al., 2021] to produce a high resolution earthquake catalog with increased detectability and relocated events. Overall, this catalog contains about 28,000 events, nearly 3 times more compared to the one produced by the Disaster and Emergency Management Presidency of Türkiye. Aftershock distribution lights up the faults involved in this sequence distinctly with some intriguing features. It varies significantly along strike and dip – both in the EAFZ and the Sürgü fault. Southwestern end of the EAFZ shows relatively low activity and diffuse seismicity while northeastern end is characterized by intense clustered seismicity. In the Sürgü fault, seismicity patterns west and east of the hypocenter are distinctly different with western part being more vigorous with streaks of aftershock activities. Seismicity also delineates significant change in fault strike and smaller branches joining the main, much longer fault lines. By the time we present this work, we plan to use this catalog to train a model based on machine learning, and produce an earthquake catalog applying artificial intelligence. In summary, distribution of aftershocks is defining complexities in the fault structures and frictional variations along the fault that may be controlling the earthquake production in this sequence.

Session: February 2023 Mw 7.8 Earthquake Sequence in Turkey

Type: Oral

Date: 4/19/2023

Presentation Time: 08:15 AM (local time)

Presenting Author: Abhijit Ghosh

Student Presenter: No

Invited Presentation: 

Authors