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High-resolution Aftershock Catalog of the 2023 Kahramanmaraş Earthquake Sequence Reveals Detailed Fault Structures in Southeastern Türkiye

Description: 

On February 6^th 2023, two magnitude larger than 7.5 earthquakes struck Southeastern Türkiye, causing widespread casualties and heavy damages. They also triggered widespread aftershocks along the East Anatolian Fault and surrounding areas within the complex Maraş triple junction. To better understand the ongoing aftershock sequence, we deployed more than 200 SmartSolo nodal stations across and along both rupture zones, focusing on major clusters and high-risk areas throughout more than 100 days beginning in May 2023. In this study, we built a high-resolution earthquake catalog using machine-learning-based phase-picking and association techniques. Although the nodal stations were recorded at 500-Hz sampling rate, the absence of labeled datasets and pre-trained models for 500-Hz signals forced our previous studies to downsample the data to 100 Hz first, resulting in reduced accuracy and resolution. To overcome this challenge, we developed a deep learning-based 500-Hz phase-picking model capable of directly processing the high-sampling-rate waveforms. Firstly, we constructed a dataset derived from the Türkiye Disaster and Emergency Management Authority (AFAD) catalog, ensuring rigorous quality control. Using this dataset, we trained a 500-Hz phase-picking model based on a revised PhaseNet architecture. After retraining, the model was applied to 100 days of data, resulting in approximately 100 million picks corresponding to over 50,000 events. Compared to 100-Hz models, the 500-Hz model achieved higher accuracy and detected a greater number of seismic phases. Subsequently, we performed phase association, event location, and double-difference relocation to produce a high-resolution aftershock catalog. Based on the new high-resolution catalog, we constructed a detailed fault structure map from a 3D fault attribute volume, revealing the main and subsidiary splay faults along the East Anatolian Fault and adjacent regions. This enhanced structural resolution can help improve our understanding of the relationship between structural properties and earthquake behaviors, and overall seismic hazards in this region.

Session: Building and Decoding High-resolution Earthquake Catalogs With Statistical and Machine-learning Tools [Poster]

Type: Poster

Date: 4/15/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Xu

Student Presenter: No

Invited Presentation: 

Poster Number: 39

Authors