TSUNAMI SEISMIC INFORMATION STATEMENT NUMBER 1
NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI
1035 AM HST MON JUL 29 2013
TO – CIVIL DEFENSE IN THE STATE OF HAWAII
SUBJECT – LOCAL TSUNAMI INFORMATION STATEMENT
THIS STATEMENT IS FOR INFORMATION ONLY. NO ACTION REQUIRED.
AN EARTHQUAKE HAS OCCURRED WITH THESE PRELIMINARY PARAMETERS
ORIGIN TIME – 1031 AM HST 29 JUL 2013
COORDINATES – 21.3 NORTH 157.6 WEST
LOCATION – OFF THE WINDWARD COAST OF OAHU
MAGNITUDE – 3.5
NO TSUNAMI IS EXPECTED. REPEAT. NO TSUNAMI IS EXPECTED.
THIS WILL BE THE ONLY STATEMENT ISSUED FOR THIS EVENT UNLESS
ADDITIONAL DATA ARE RECEIVED.
USGS: How large does an earthquake have to be to cause a tsunami?
Magnitudes below 6.5
Earthquakes of this magnitude are very unlikely to trigger a tsunami.
Magnitudes between 6.5 and 7.5
Earthquakes of this size do not usually produce destructive tsunamis. However, small sea level changes may be observed in the vicinity of the epicenter. Tsunamis capable of producing damage or casualties are rare in this magnitude range but have occurred due to secondary effects such as landslides or submarine slumps.
Magnitudes between 7.6 and 7.8
Earthquakes of this size may produce destructive tsunamis especially near the epicenter; at greater distances small sea level changes may be observed. Tsunamis capable of producing damage at great distances are rare in the magnitude range.
Magnitude 7.9 and greater
Destructive local tsunamis are possible near the epicenter, and significant sea level changes and damage may occur in a broader region.
Note that with a magnitude 9.0 earthquake, the probability of an aftershock with a magnitude exceeding 7.5 is not negligible. To date, the largest aftershock recorded has been magnitude 7.1 that did not produce a damaging tsunami.