27 FEB 2010 Earthquake and , GPS, and GREAT Project

Dailin Wang and Vindell Hsu

Pacific Tsunami Warning Center 27 FEB 2010 M 8.8

Fifth(?) largest earthquake recorded

One of few basin crossing in recent history

Fatality:577; 80% due to tsunami

PTWC operation

• : magnitude

• Waterlevel: Tsunami wave height modeling

Model Results of the 2010 Chile Tsunami Forecast models used at PTWC during the event:

1. SIFT (Short-term Inundation Forecasting of Tsunamis) With SIM (standby inundation models, high resolution run-up models for selected US communities (, US E/W coast, and ) SIFT is a database of pre-computed scenarios. DART data are used for inversion in real time. Inverted results are fed to SIMs. Retrieving the database results takes 10-20 seconds. Each SIM takes about 6-min. to run.

2. ATFM (Alaska Tsunami Forecast Model, developed at ATWC) Database of pre-computed scenarios (with fewer sources than in SIFT). Much finer resolution than used in SIFT database. Scaling with observed tide and/or DART observations to refine forecast. Retrieving the database results from the ATFM model takes only a couple of seconds, almost instantaneously.

3. RIFT (Real-time Inundation Forecasting of Tsunamis) A propagation model developed in house at PTWC, completely computed in real-time using real time EQ parameters (including CMT solutions). A forecast for the entire Pacific takes less than 7 minutes. DART observations and model results obtained at various times during the event RIFT results, obtained 104 min. after the origin matched observation the best

The over predictions from SIFT at 1033Z and ATFM at 1510Z were due to incorrect inversion and scaling. The results from these two runs were not used in PTWC’s forecast during the event.

Model results (near field results from RIFT, Pacific results from SIFT and ATFM) were not included. Coastal forecast: 1. The over prediction from ATFM was due to error in how scaling with DARTs was performed. 2. Most of the results agreed with observations pretty well. 3. Warning was based on the 1 m threshold, thus Hawaii was placed in warning. Maximum wave amplitude recorded at tide gauges was close to 1 m (=0.97 m). There was evidence that waves of more than 1 m occurred at other parts of the Hawaii Islands where there were no tide gauges.

These two runs were rejected (not used) as forecast during the event RIFT Coastal forecast at locations where there were no SIFT and ATFM forecasts. RIFT tends to over predict in near field but forecast in the far field were almost right on, given the fact no scaling or inversion of any kind was used. The RIFT results were obtained 104 min. into the event, from a run using USGS CMT parameters.

Hawaii was outside the energy beam

RIFT correctly predicted relatively high wave heights in and Conclusion • The Chile earthquake generated one of the largest basin-crossing tsunamis in recorded history, save perhaps, 1946 Aleutians, 1960 Chile, 1964 Alaska, and 2004 Sumatra tsunamis.

• The model forecast (included in PTWC’s bulletins) during the event were not very different from what was observed later. For Hawaii, the maximum observed wave amplitude was 0.97m vs the predicted 1.25 m.

• Wide-spread warning was clearly warranted based on the 1-m criterion. The observed wave amplitude at Hiva Marquesas was 1.85 m vs. the 1.80 m predicted from RIFT. There were reports of significant damage at Hiva , 7,200 km from the epicenter. The observed wave amplitude in New Zealand was 0.9 m vs the predicted 0.95 m from RIFT, close to the warning threshold. The maximum wave amplitude in Japan was 0.8 m, same as predicted by RIFT, also close the warning threshold.

• Clearly, closet to 1-m wave did not cause any damage in Hawaii, New Zealand, and Japan. Namely, a 1-m wave might not call for an all out evacuation, which happened in Hawaii. Authorities should take this into account for future events. Tiered responses might be needed to avoid unnecessary over evacuation. For example, the response to a 1-m wave and a 2-m wave should be different.

• Disclaimer: the opinions expressed here are not necessarily the official opinions of NOAA, NWS, and PTWC. T

What can GPS data tell us?

GREAT project

All the underlying earth science models and GPS data types have been validated with actual data from past events. Using a rapid prototyping approach we will build a prototype GREAT Alert System within the first year, enhancing the current USGS and PTWC damage assessment and alert systems. We will refine it and perform quantitative benchmarking during the second year with input from our partner agencies, and pursue transition to operations during the third year.