[A-HW28] Hydrology and Water Environment

[AHW28-08] Dating of tsunami deposits found in different sedimentary environments along the southern Java coast, Indonesia

★Invited Papers

Rinta Ogawa¹, Januar Ridwan¹, Eko Yulianto², Purna Sulastya Putra², Ryan Dwi Wahyu Ardi², Kazumasa Miura¹, Shinya Ochiai¹, Kota Katsuki³, *Noriko Hasebe¹ (1.Kanazawa University, 2.National Research and Innovation Agency, Indonesia, 3.Shimane University)

Keywords:OSL dating, sediment core, Indonesia

Optically stimulated luminescence (OSL) dating was applied to date and characterize past tsunami deposits in sediment samples collected from two sites with different sedimentary environments in southern Java, Indonesia. One site is located along the river, and the other site is within the rice field. The river-side site ia around 0.5 km inland from the coast, and is expected to preserve the deposit carried by run-up tsunami along the river. While the rice field, around 1 km inland, preserves deposits by the tsunami reached behind the topographic high. In addition to the OSL measurements, grain size analysis was carried out in an attempt to identify tsunami deposits.
The lineally modulated (LM) -OSL analysis showed the predominance of medium and slow luminescence components and the less fast component in the measured quartz due to its volcanic origin, not perfectly suitable for OSL dating. However, the dose recovery test was at an acceptable level, promising more or less reliable dating results.. The OSL dating at the river-side site resulted in ages of 100-400 years ago, consistent with the recorded tsunami events. Tsunami samples from rice field show ages of 400-1200 years ago. This suggests the Java has experienced bigger tsunami events in the past. The chronological data also suggest that tsunamis may occur in the region with a 50–100 year cycle.