The fault that struck Myanmar in March tore through hundreds of miles of the earth’s surface, highly efficient in transferring energy from deep underground to the surface.
In many earthquakes, the underground moves more than the surface. But the earthquake on the Sagaing Fault was different, a new study shows, because it moved the surface as much as the rock at depths of several miles. This is likely because the origin of the Saiko Fault dates back 14 to 28 million years ago.
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When the magnitude 7.7 earthquake struck on March 28, it destroyed about 300 miles (500 kilometers) of the ground. This was a surprisingly long surface break. Earthquake destruction is typically around 19 to 37 miles (30 to 60 km) away, Lindsey said. The destruction was accompanied by extremely violent shaking, and more than 5,400 people were killed.
Because of the infrastructure damage caused by the earthquake and the continuing armed conflict in Myanmar, Lindsay and his colleagues turned to satellite imagery to study the event. They used both optical imagery and radar data from the European Space Agency’s Sentinel 2 satellite to track ground movement down to a fraction of an inch.
Their findings, published Dec. 8 in the journal Nature Communications, showed that earthquakes transferred their energy to the surface very efficiently. Earthquakes occur deep underground. In the case of the Myanmar earthquake, destruction began at a depth of about 6 miles (10 km). In most cases, underground movements are not completely transmitted to the surface. This is a phenomenon called “shallow slippage”. (Slip is the movement of one side of a fault relative to the other.) In the Myanmar earthquake, there was no shallow slip deficit.
“The massive amount of slip that occurred several miles underground was transmitted 100 percent to the surface,” Lindsey said.
The ground surface on one side of the fault moved 10 to 15 feet (3 to 4.5 meters) relative to the other side. The movement was caught on camera in the first video of its kind.
Because of the efficiency with which energy is transferred from deep underground to the surface, earthquakes on mature faults, such as the one that struck Myanmar, can cause more ground shaking than those on more jagged faults, Lindsey explained.
“The key is safety,” he said. “This earthquake showed that mature faults can transfer energy to the surface much more efficiently than younger faults. This has direct implications for how we build infrastructure to withstand ‘mega-faults’ in the United States.”
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