Shedding New Light on Earthquake that Killed 9,000 people

For decades, scientists have debated the structure of the Main Himalayan Thrust -- the fault responsible for a 2015 earthquake that killed nearly 9,000 people, injured 22,000, and destroyed 600,000 homes in Gorkha, Nepal. This fault is a direct result of ongoing collision between two tectonic plates -- the Indian and Eurasian -- that gives rise to the Himalayas. A team of researchers has determined a new geometric model for the fault that will allow officials to better prepare for future shakers.

Following the quake, Ghosh, a UCR associate professor of geophysics, and his collaborators rushed to Nepal to operate a network of 45 seismometers in the ground. Their journey was complicated by the difficulty of traveling in that high-altitude, rocky region as well as the timing of the quake during monsoon season.

"The geometry of the fault also matters," Ghosh said. "It's critical to look at smaller earthquakes and aftershocks to determine where the stress points are in a fault. Fault geometry plays a major role in earthquake generation."

It is also critical to learn the shape of a fault, as well as earthquake "style," meaning the ways in which a block of rock moves relative to other rocks during an earthquake.

The team found that the Himalayan Thrust, which runs more than 1,000 kilometers from Pakistan to Myanmar, is built in a shape known as a duplex in the area where the magnitude 7.8 earthquake occurred in 2015.

The team concluded the fault is still accumulating stress, and that the 2015 event may have increased the likelihood of another big earthquake nearby. This last point may be of interest to Californians.

Those residing anywhere near major fault lines should always have an emergency plan and supplies on hand because earthquakes are inevitable.



https://www.sciencedaily.com/releases/2019/11/191112073557.htm