Earthquake Safe Communities in Nepal

Training on 'Earthquake Hazard Assessment and Aftershock Forecasting' held in Kathmandu

A training on "Earthquake Hazard Assessment and Aftershock Forecasting" held in Kathmandu during April 9-12, 2019. The main objective has been to enhance knowledge on earthquake hazard and forecasting aftershock in Nepal. A total 35 participants from government agencies, academia, NSET and ESS participated. A team of facilitators including experts and senior professionals from Nepal Government, Academia, NSET and USGS conducted the course.

The course covered various topics and issues: Hazard in Nepal, Sources, Paleoseismology and Historical Earthquake; Nepal earthquakes, catalogue and processing; Site characteristics: Experience of Gorkha Earthquake; Site effects from analysis of spectral ratio and numerical simulation; Comparison of observed and predicted ground motion; Seismic microzonation; PSHA: How it is prepared?; and Aftershock forecasting.

The four-day training was jointly organized by Nepal Government’s Department of Mines and Geology (DMG), United States Geological Survey (USGS), National Society for Earthquake Technology-Nepal (NSET) and Earthquake Safety Solutions (ESS) with the support from Office of U.S. Foreign Disaster Assistance (USAID/OFDA). The training is a part of ongoing collaborative effort of organizing partners in association with various academic institutions and agencies.

Also, as a part, a half -day seminar on “Aftershock Forecasting” organized on April 11, 2019 targeting for the participants from media, government offices, academia and DRR community. The seminar was focused on basics of aftershock forecasting, principles, methods and tools. During the seminar, Dr. Susan Hough, Seismologist from USGS clarified the concept of aftershock, its basic features, past experiences in relation to various major earthquake events in the world including 2015 Gorkha Earthquake and subsequent aftershocks.

Claiming that the sequence of earthquake that occurred after the 2015 Gorkha Earthquake as unusual as it was too many in comparison to other earthquake events around the world, Dr. Hough remarked, "overall phenomenon of aftershock was within the boundary of USGS forecast that was done right after the 2015 Gorkha Earthquake."

On the occasion, Dr. Anne Wein, Operations Research Analyst from USGS shared her research about trends and ways of media reporting about aftershock events in USA and Nepal. Dr. Wein mentioned, "I found Nepali media done exemplary job in term of communicating information about the series of aftershocks that Nepal underwent after the 2015 Gorkha Earthquake."

In floor discussion, participants from diverse fields put forth their queries in regard to the aftershock forecasting techniques on which the experts shared their knowledge and ideas. Some of useful information shared during the seminar regarding the aftershock forecasting are as follows:

• After studying and analyzing the aftershocks of the past events statistically, sequence of aftershocks of new event can be forecasted.
• Every individual earthquake is an earthquake.
• Aftershock sequence can continue for years.
• Aftershock do not necessarily occur on the same fault that produced the initial main shock but may occur close to the fault that moved in the main shock.
• Most of the aftershocks will be small but few may be relatively large.
• On an average, largest aftershock is about 1 magnitude unit smaller than the main shock (the May 12 aftershock with epicenter in Dolakha, however, was an exception as it was less than 1 magnitude unit smaller).
• The frequency of Aftershocks decreases gradually as the time passes by. But that does not mean magnitude also decreases as per time.
• The rate of aftershocks of Gorkha Earthquake is higher than earthquakes around the world.
• After four years of the Gorkha Earthquake, the rate of aftershock is still six time higher than the normal.

After the 2015 Gorkha Earthquake and subsequent aftershocks, earthquake phenomena have been much discoursed in public, academic and scientific communities in Nepal. There is a felt need of building better scientific understanding and enhanced civic education on seismic phenomena in Nepal. With the prime objective to enhance knowledge on earthquake hazard in Nepal, in the guidance of DMG, NSET and USGS had jointly organized a training workshop on "PSHA, Seismic Microzonation and Monitoring" during 25-27 April 2016. Later, NSET and USGS organized "Training Workshop on Earthquake Engineering" in collaboration with California Institute of Technology (CalTech) and Earthquake Safety Solutions (ESS), Nepal during September 19-22, 2016 in Kathmandu. This event is the continuation of the collaborative effort.


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