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A powerful 7.7-magnitude earthquake struck the Sagaing region of Myanmar near the city of Mandalay on Friday, causing extensive damage across the country and shaking neighboring Thailand.
Myanmar and its Seismic Vulnerability
Myanmar sits along the boundary of two tectonic plates, making it one of the world’s most seismically active nations. However, large and destructive earthquakes have been relatively rare in the Sagaing region.
The plate boundary between the India Plate and Eurasia Plate runs approximately north-south, cutting through the middle of the country.
These plates move past each other horizontally at different speeds, leading to “strike-slip” quakes. While such quakes are typically less powerful than those in subduction zones—where one plate slides under another, as seen in Sumatra—they can still reach magnitudes of 7 to 8.
Why Was Myanmar Earthquake So Destructive?
The Sagaing region has experienced several earthquakes in recent years, including a 6.8-magnitude tremor in 2012 that resulted in at least 26 fatalities and numerous injuries. However, Friday’s earthquake was likely “the biggest” to hit Myanmar’s mainland in over 75 years.
The United States Geological Survey (USGS) reported that the epicenter was just 10 km (6.2 miles) deep.
“This is very damaging because it has occurred at a shallow depth, so the shockwaves are not dissipated as they travel up to the surface,” an earthquake expert explained to Monneycontrol.
The expert also pointed out that it is crucial not to focus solely on the epicenter. “The seismic waves don’t just radiate from the epicenter—they spread from the entire fault line,” he added.
The Sagaing Fault: A Major Earthquake Threat For Myanmar
A primary factor contributing to Myanmar’s earthquake risk is the Sagaing Fault, a significant continental right-lateral transform fault between the Indian Plate and the Sunda Plate. Spanning approximately 1,200 km through Myanmar, this fault has been associated with numerous earthquakes, underscoring the region’s seismic activity.
The Sagaing Fault features two landmasses moving sideways past each other, with movement rates estimated between 11 mm and 18 mm per year. This continuous shifting builds up stress, eventually releasing it as earthquakes. The slip rate of up to 18 mm annually indicates substantial movement, suggesting significant energy accumulation that could trigger future quakes.
Understanding Earthquakes: Causes and Measurement
Earthquakes occur when Earth’s tectonic plates move against each other, creating friction. This sudden movement along a fault line results in violent ground shaking and can sometimes trigger landslides, flooding, and even tsunamis.
Despite appearing stable, the Earth’s interior is highly active. It consists of four layers: a solid crust, a hot, semi-solid mantle, a liquid outer core, and a solid inner core. The lithosphere, which includes the crust and part of the mantle, is broken into large tectonic plates that constantly shift on the underlying viscous mantle layer.
As these plates move, stress builds up in the Earth’s crust. When the stress exceeds the rock’s ability to withstand it, fractures—known as faults—form. The movement of tectonic plates along these faults leads to seismic activity. The point where an earthquake originates is called the epicenter, with the most intense shaking typically occurring near this location, though vibrations can be felt hundreds or even thousands of miles away.
How Are Earthquakes Measured?
Scientists assess earthquakes using both magnitude and intensity. Magnitude quantifies the energy released during an earthquake and is measured using a seismograph. Historically, the Richter scale—developed by Charles Richter in the 1930s—was used for this purpose. However, it has since been replaced by more advanced methods.
The USGS now primarily uses the Moment Magnitude Scale (Mw) to report earthquake magnitudes, though other scales exist for research and comparative purposes. Unlike the Richter scale, which measures only the largest amplitude of seismic waves, modern magnitude scales evaluate different aspects of an earthquake’s energy release.
Meanwhile, intensity gauges the level of shaking and damage caused by an earthquake. Unlike magnitude, which is consistent for a given event, intensity varies based on location, soil conditions, and building structures in the affected area.
Also Read: Myanmar Earthquake Death Toll Reaches 144, About 732 Injured, Numbers Expected To Rise
