Abstract. A train of tsunami waves, by resembling a swift series of tides, can produce damaging currents even where wave heights are modest. At Karachi Port, the 1945 Makran tsunami moved boats and damaged a rock groyne without exceeding 3 m in height above ambient tide. A newspaper account mentions an ebb current of 4 to 5 knots. We obtained ebb currents in this range by means of computer simulations with GeoClaw, an open-source code. The simulations, which use bathymetry and shorelines mapped before 1945, presuppose for simplicity a purely tectonic source for the 1945 tsunami. The simulations were tested mainly against an incomplete marigram from the Karachi tide gauge. Runs with modern bathymetry and shorelines show weaker currents, probably because of a post-1945 extension of a breakwater. Using a damage index previously developed from tsunami-current measurements in other harbours, we asked whether the currents simulated for 1945 were fast enough to cause the reported damage to the groyne. Those currents were found fast enough to have caused damage termed "Minor/Moderate" in seaward parts of Karachi Harbour.
Keywords. tsunami; current speeds; Makran; Karachi Port
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