[S08-1] Paleoseismology and paleotsunami studies: Their potential and limitation I

[S08-1-05] Paleoseismology of the Himalayan Frontal Zones

^○Koji Okumura¹, Javed Malik² (1.Hiroshima University, Higashihiroshima, Japan, 2.Indian Institute of Technology Kanpur, Kanpur, India)

invited

The damages of the April 25 2015 Gorkha earthquake aroused much concern about seismic risks along the Himalayan front though the rupture occurred only in a deeper part of the megathrust. 20 years of paleoseismological research have brought a lot of information on time and space of past earthquakes. However, we are still far from confidence on our ability to assess sesismic risks owing to the lack of information on both inter-plate and intra-plate earthquakes. From 2010 to 2014 within a JICA-JST SATREP* project in India, we have conducted paleoseismological studies on frontal and upper-plate faults at 7 sites. A few strike-slip faults in the upper plate were newly recognized and one of them, the Kangra Valley fault is supposed to be the source of the 1905 earthquake instead of the frontal fault. This indicates a possibly near future frontal earthquake in NW India. The last large event from the central seismic gap is still controversial, but one big event in 15 century or 1505 is being confirmed in one of our trenches. The next earthquake in the gap will be the most serious issue for India and Nepal. In order to know more about the future 1505 type earthquake, we need further studies in Nepal, where there is no consensus on the rupture sequence in space and time in the last millennium. (*Science and Technology Research Partnership for Sustainable Development by Japan International Cooperation Agency and Japan Science and Technology Agency)