RAPID: Extensometers to Measure Afterslip on the Sagaing Fault Following the M7.7 March 2025 Mandalay Earthquake

This project aims to measure ongoing slip along the Sagaing Fault in Myanmar, near and south of the epicenter of the magnitude 7.7 earthquake that struck on March 28,2025, killing more than 3,600 people. While the fault near Mandalay slipped by about 15 feet (5 m), the southern end moved only a few feet. Thus, it remains unclear whether the southern segment is now locked or if it continues to slip slowly, raising concerns about future earthquakes near Yangon, a megacity of over 8 million residents.

Using highly sensitive instruments called creepmeters, the team will monitor surface fault movement with 1/10,000 inch (2.5 μm) precision, recording the information every minute. These measurements will help determine whether the fault is still moving silently (afterslip), which can precede future ruptures. A similar reduction in slip was seen during the 1906 San Andreas Fault earthquake, though such detailed monitoring was not possible then.

Project data will help assess ongoing seismic hazard in one of Southeast Asia's most densely populated regions as well as to test instrumentation that may be used when similar type earthquakes occur in the U.S..

Following the Mw 7.7 Mandalay earthquake, segments of the Sagaing Fault are expected to be slipping slowly through the process of afterslip. This silent fault motion typically occurs near and beyond rupture terminations and may persist for over a year before decaying to negligible rates. Measuring the evolution of this slip will allow the team to assess how frictional properties of the fault were altered by the mainshock.

An increase in slip rate may signal elevated seismic hazard, including the possibility of future triggered earthquakes. The team will deploy highly sensitive creepmeters capable of resolving 2.5 μm to record fault motion continuously once-per-minute. These instruments can detect both dextral (horizontal) slip and fault dilation.

Singapore-based collaborators, already active in Myanmar, will host and operate the devices as part of a new, instrument-based afterslip study. This project focuses on the southern segment of the rupture, where slip during the earthquake was significantly less than further north. Southward propagation of afterslip into this area poses a direct threat to Yangon, a city of over 8 million.

Unlike satellite-based geodetic methods, which offer only weekly resolution and far lower sensitivity, the ground-based data will provide high-resolution insight into near-field fault deformation. This study will fill a critical observational gap in understanding the evolution of afterslip and its role in post-seismic hazard. It also provides a rare opportunity to study fault mechanics in near-real time, in a region of high vulnerability and limited prior instrumentation.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.