Near Source Tsunami Model Product
Diego Melgar, Scripps Institution of Oceanography
March 24, 2014
Once a model of the geographical extent and size of the earthquake is available (see
fastCMT and finite fault slip products) then we can produce rapid models of what size
tsunami such an earthquake would generate. Furthermore we can predict the inundation
amplitudes in the coastline closest to the earthquake.
The figure below shows the result of such a procedure for the 2011 magnitude 9 Tohokuoki earthquake off-shore Japan. A slip model (a) which depicts the amount of motion at
the fault during the earthquake is used to estimate the uplift and subsidence of the
seafloor (b). This estimate of seafloor motion is used to initiate a model of the tsunami
propagation. One of the deliverables from tsunami modeling is the maximum expected
amplitude of the tsunami (c).
For the Tohoku-oki event this information is available within 30 minutes after the onset
of the earthquake. It is based on land GPS stations (blue triangles in a) and off-shore
buoys and ocean bottom pressure gauges (white triangles in c). If more sea floor
measurements were available closer to the zone of maximum seafloor uplift then such
models could be made available faster, perhaps as soon as 5-10 minutes after the onset of
the earthquake. A more simplified but nevertheless useful model for tsunami early
warning could be generated in as little as three minutes using only land-based GPS data.
The products depicted below have been validated for the Japanese case against 2000+
inundation survey points collected all along the coast by Japanese scientists in 2011.
Product: Near-Source Tsunami Model