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Preliminary Results on the Main Rupture Properties, Aftershock Activities and Remotely Triggered Seismicity Associated with the M7.7 Sagaing Fault Earthquake in Myanmar

A devastating Mw 7.7 earthquake struck near Mandalay, Myanmar, on March 28, 2025, causing extensive damage and casualties across Myanmar and neighboring regions. The mainshock rupture propagated approximately 500 km southward along the 1400-km-long right-lateral Sagaing Fault. This fault connects the divergent plate boundaries in the Andaman Sea and the active collision fronts near the eastern Himalayan syntax in the Tibetan Plateau, and hosted multiple Mw ≥ 6 earthquakes over the past centuries. The 2025 event occurred in a well-recognized seismic gap and was the largest strike-slip earthquake ever occurred in this region in the past 100 years. Here we present preliminary results on the mainshock rupture properties based on back-projection of teleseismic P waves and analysis of near-field seismic recordings. We detect and locate additional early aftershocks that are buried in the coda waves of the mainshock and large aftershocks. We find that the ~500 km mainshock rupture can be fully revealed within about 1 hours by both early aftershock locations and the back-projection of teleseismic P waves from multiple broadband arrays. The rupture speed went supershear after the initial slower ruptures, as expected for large strike-slip earthquakes of such sizes. In addition, earthquake catalogs from Thailand national seismic network and Yunnan and Guangdong provincial seismic network in China have shown a significant increase of seismic activity in selected regions from the mainshock rupture zone, suggesting a widespread triggering by dynamic stresses from the mainshock in these regions. While no immediate foreshocks were found from several nearby stations, we show that the mainshock occurred when the tidal stresses reached its maximum on the right-lateral strike-slip fault, indicating that the timing of the mainshock is modulated by the solid earth tides. Our analyses demonstrate the importance of rapid analysis on openly available seismic data and catalog to better understand the mainshock rupture properties and triggered seismicity in the surrounding regions. Updated results will be presented at the meeting.

Session: Late-breaking on Recent and Future Large Earthquakes [Poster]

Type: Poster

Room: Exhibit Hall

Date: 4/15/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Zhigang Peng

Student Presenter: No

Invited Presentation: 

Poster Number: 150

Additional Authors