One of the first scientists to enter Nepal following the April 25 Gorka earthquake, University of Nevada, Reno seismologist and professor Steve Wesnousky has been on the ground in the Himalayas searching for geophysical signs of the magnitude 7.8 earthquake.
Wesnousky, a geoscientist in the College of Science and director of the University's Center for Neotectonic Studies, has been studying the Himalayan Frontal Thrust Fault since 1999. He and two of his doctoral students, Ian Pierce and Steve Angster, have spent the past six days in the area south of Kathmandu looking for ground ruptures, following leads from villagers and residents as well as visiting various other sites studied in the past.
They saw damaged buildings and areas hit by landslides, and were surprised by the amount of damage.
"For a city of four million built out of primarily lightly reinforced masonry to survive an earthquake of this size with fewer than 3,000 deaths was very fortunate," they reported in an update posted to the University website. "At the same time it is a great tragedy for those who did lose their homes or family members."
The team, accompanied by Deepak Chamlagain, a professor at Tribhuvan University in Kathmandu, has not yet observed any obvious evidence of surface rupture along one of the world's longest earthquake faults that affects one of the most populous areas of the Earth.
Even so, they wrote, "we are learning more about this earthquake and realize how unique this event is. During our search, we were led by locals to a large landslide triggered by shaking from the earthquake. After crawling around on the large blocks and assessing the landslide, we were able to educate the villagers on how it happened and, thanks to Dr. Chamlagain, assist them in receiving future aid for the potential danger this slide poses."
"We were very worried about the village below, as during the coming monsoons, the slide will likely reactivate and take out the village," Pierce said. "We explained this to them, and hopefully they will pay attention to this slide. Unfortunately for us, this was not the surface rupture we were looking for."
Wesnousky a member of the Nevada Seismological Laboratory, received a grant from the National Science Foundation in September to continue his studies. His work centers on the foothills south of Kathmandu, just over the border in India but he is expanding his study area following the historic quake, the first large quake in that area since 1930.
Wesnousky and colleagues have conducted paleoseismic studies to define both the timing and magnitude of prehistoric earthquakes along the Himalayan Frontal Thrust. He has six peer-reviewed scientific papers about the Himalayan fault. The observations are working to define the seismic hazard of the region as well as the mechanics of fault rupture along major continental thrust faults.
What the team finds in the next few weeks may help scientists to calibrate results from earlier studies and to quantify what the potential is for additional earthquakes in the magnitude 8 or magnitude 9 range. The team plans to be there for two weeks, possibly longer if they are successful in finding ground ruptures.