Public Lecture: Can Past Earthquakes Affect Contemporary Rainfall-Initiated Landslide Hazards? - Evidence from Central Asia and Japan
11 April March 2017, 11:00
Professor Roy C. Sidle
Sustainability Research Centre
University of the Sunshine Coast
Much of Central Asia and most parts of Japan have experienced major earthquakes, and many landslides are triggered by earthquakes in both regions. However, a larger number of landslides are triggered by rainfall, especially in Japan. Rainfall-initiated landslides tend to occur on hillslope positions where subsurface water accumulates – e.g., concave slopes and areas downslope of ridgelines so that subsurface water can accumulate. In contrast, earthquake-initiated landslides typically occur near ridgelines and on convex or planar slopes, sites where seismic waves amplify.
Although landslides in Kyrgyzstan have not been as intensely investigated as earthquakes and tectonics, it appears that of most types of landslides occur in the rugged Tien Shan terrain. These are often triggered by earthquakes, but many initiate during rain events and snowmelt. However, due to sparse habitation, people and property are rarely affected, with the exception of landslides along the major north-south highway. The more populated Fergana Valley nestled within the Tien Shan has experienced devastating landslides, which have destroyed on average seven homes and killed 10 people each year in the eastern (Kyrgyzstan) region alone, despite the much gentler topography.
Although this hilly region with soft sediments has not been directly affected by large (M > 7) earthquakes, periodic smaller earthquakes and large earthquakes in the Tien Shan have caused fissues to develop near ridgelines and on convex slopes. Many of the landslides in this part of the Fergana Valley initiate on such slope positions. However, they have been attributed largely to accumulated rainfall and snowmelt. These ridgelines and convex slopes are common sites for earthquake-initiated landslides, but not landslides triggered by rainfall or snowmelt. Herein, I propose that there is a connection between these earthquake-initiated fissures, developed years or decades before slope failure, with preferential transport of rainwater and runoff deep into the soil that may initiate landslides.
Further evidence of this mechanism is emerging from research near Kumamoto, Japan, which was struck by major, shallow earthquakes in April 2016. In the areas where the most intense ground shaking occurred, many landslides initiated along ridgelines or on convex and planer slopes. In addition, large fissures appeared along ridgelines during the earthquakes, which could later preferentially route rain water and runoff into the soil mantle, thus triggering landslides during future storms. Additionally, landslide sediment stored in headwater channels due to the limited mobility of most earthquake-initiated failures poses a risk for future debris flows. These scenarios represent cascading sequences of events that may generate future environmental and human risks, including impacts to water quality, sediment disasters in rural communities, and damage to buildings and infrastructure.
Professor Sidle has 40 years of experience in research and team leadership in the areas of catchment hydrology, geohazards, and environmental science. Currently he is Professor of Geography and Associate Director of the Sustainability Research Centre at University of the Sunshine Coast in Queensland, Australia, where he is examining sources and movement of sediments in managed coastal catchments and landslide processes.
During the past two decades he has held academic and research appointments in USA, Japan, Singapore, Canada, and Europe, including at the Geological Survey of Denmark and Greenland, IGBP-LOICZ (Holland), University of British Columbia, National University of Singapore, Kyoto University, Appalachian State University, and Director of US EPA’s Ecosystem Research Division. He has published more than 165 papers in refereed journals and is senior author of two books on landslides. In 2010 he was elected as a Fellow in American Geophysical Union and in 2014 he received the International Award from Japan Society of Hydrology and Water Resources.
University of Central Asia
138 Toktogul Street
Bishkek, Kyrgyz Republic
2nd Floor Conference Room
The presentation will be conducted in English.
* Views presented in the lecture reflect personal views of the lecturer and do not necessarily reflect the ideas of the University of Central Asia and its employees.