Karachi tides during the 1945 Makran tsunami

Geoscience Letters
By: , and 

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Abstract

This paper extends and detides a Karachi tide-gauge record as an observational basis for assessing Indian Ocean tsunami risk. The extended marigram encompasses the time of the great 1945 Makran earthquake of early November 28, local time, and of the ensuing tsunami, which continued into November 29. The marigram was published previously as a 9-h excerpt that begins 1 h after the earthquake. The full marigram presented here covers most of 17 days from November 15 to December 1. Gaps include a tsunami-induced outage that may help explain why the highest water level gauged is 1 m below the maximum water level reported nearby. The detiding method computes a reference tidal curve that disregards all observations from November 28 and 29. For those 2 days, the reference tide is guided by Admiralty tide tables and, secondarily, by high waters and low waters gauged before and after. As in previous estimates, the detided tsunami crests about 0.5 m above ambient tide, but now with the possibility that the gauge failed to record a higher wave. Anomalies described for the first time include an early one that likely resulted from a recognized problem with the Karachi tide station, but which might instead represent an earthquake precursor.

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Publication type Article
Publication Subtype Journal Article
Title Karachi tides during the 1945 Makran tsunami
Series title Geoscience Letters
DOI 10.1186/s40562-018-0121-z
Volume 5
Year Published 2018
Language English
Publisher Springer
Contributing office(s) Earthquake Science Center
Description 25, 13 p.
Country Pakistan
City Karachi
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