University of Central Asia's video: Online Public Lecture: Sensitivity of Rockfall Frequency-Magnitude

October 16th 2020, 5:00 pm (Khorog time, GMT+5) Sensitivity of Rockfall Frequency-Magnitude and Wall Retreat Rates to Observation Duration from TLS Measurements Solmaz Mohadjer Assistant Professor, Earth and Environmental Sciences, UCA-Khorog Abstract Rockfalls are common in steep valleys produced by glaciation. They contribute to valley erosion and pose substantial hazard to people, properties and infrastructure. In this lecture, we investigate the temporal variation in rockfall activity in the 5.2 km2 calcareous cliffs of the deglaciated Lauterbrunnen Valley located in the Bernese Oberland, Switzerland. This was done based on time series of repeat terrestrial laser scan (TLS) measurements collected over a 5.2-year period, power-law predicted behaviour from extrapolation of the TLS-derived frequency-magnitude relationship, and estimates of long-time-scale (∼11 k.y.) activity based on the volume of preserved postglacial rockfall talus. Short-term average cliff retreat rates indicate no statistically significant difference between TLS observations averaging over 1.5 vs. 5.2 years, and range between 0.03 and 0.08 mm/yr. In contrast, the power-law predicted rock-wall retreat rates are 0.14–0.22 mm/yr, and long-term rates from talus volumes are 0.27–0.38 mm/yr. These results suggest (1) short (1.5 yr) TLS inventories of rockfalls provide similar frequency-magnitude relationships as longer (5.2 yr) inventories, and (2) higher rock-wall retreat rates over long time scales may reflect debuttressing and stress relaxation effects after glacial retreat, and/or enhanced rockfall activity under periglacial (climatic) conditions. Biography Solmaz Mohadjer investigates how mountain hazards are linked to mountain building processes, continental deformation and erosion rates. She uses many different tools including GPS geodesy, geochronology and remote sensing. Prior to joining UCA, she was a postdoctoral researcher at the University of Tübingen (Germany), where she studied erosion rates using cosmogenic isotopes in the western Tian Shan, developed a geohazards database for Central Asia, and created educational videos for sharing geoscience with schools. For more information about her current projects, see: http://solmazmohadjer.com/. Moderator Prof. Mohssen Moazzen, EES, UCA-Khorog. Language¬¬¬ The online lecture will be in English. Past online lectures are available on the University of Central Asia's YouTube channel at http://www.youtube.com/ucentralasia. Ideas presented in this lecture reflect the personal opinion of the speaker and do not necessarily represent the views of the University of Central Asia and/or its employees.