Characterizing Tsunamis from Paleotsunami Deposits in Queule, South-Central Chile Based on Forward (GeoClaw) and Inverse (TSUFLIND) Numerical Simulations.
Abstract
Understanding tsunamigenic earthquake ruptures in a subduction zone requires an extensive record of past tsunamis. This study extends such record in the area of the largest earthquake ever recorded: the Mw 9.5 1960 Chile earthquake. Near the town of Queule (39.3˚S, 73.2˚W), we found two sand layers interpreted as tsunami deposits interbedded with dark, organic-rich soils. We studied the sand layers in core transects, pits, and tidal-channel outcrops landward of a sand spit capped by eolian sand dunes. The upper sand sheet was found near the surface, and being widespread, is attributed to the 1960 tsunami. The deposit was mapped and described in the field and compared with 1961 aerial photographs. A deeper sand layer consistently occurs 20 cm below the upper deposit in areas that are protected from tidal erosion by a bedrock ridge. Pending radiocarbon ages will determine whether the older deposit is associated with one of the large historical tsunamis in 1575 or 1837. The presence or absence of a tsunami deposit from either of these historical events in Queule would further constrain their latitudinal extent.
For further analysis of these findings, we compute numerical simulations of the 1960 tsunami in Queule using GeoClaw finite-slip hydrodynamic model using published earthquake source parameters. In conjunction with the forward model, we also use the inverse sediment transport model (TSUFLIND) to estimate tsunami wave height and flow speed necessary to produce the observed deposits. The results from both simulations are compared with the distribution of the sand sheets, the 1961 aerial photographs, and the 1960 tsunami effects reported by interviewed survivors. Ultimately, these results will be used to constrain earthquake ruptures and further understanding of tsunami hazards in the region.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMNH32A..06M
- Keywords:
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- 4315 Monitoring;
- forecasting;
- prediction;
- NATURAL HAZARDSDE: 4333 Disaster risk analysis and assessment;
- NATURAL HAZARDSDE: 4341 Early warning systems;
- NATURAL HAZARDSDE: 4564 Tsunamis and storm surges;
- OCEANOGRAPHY: PHYSICAL