TSUNAMI INFORMATION STATEMENT NUMBER 2 NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI 0136 UTC TUE OCT 31 2017 ...PTWC TSUNAMI SUPPLEMENT STATEMENT... PRELIMINARY EARTHQUAKE PARAMETERS --------------------------------- * MAGNITUDE 7.0 * ORIGIN TIME 0042 UTC OCT 31 2017 * COORDINATES 21.7 SOUTH 169.0 EAST * DEPTH 15 KM / 9 MILES * LOCATION SOUTHEAST OF LOYALTY ISLANDS EVALUATION ---------- * AN EARTHQUAKE WITH A PRELIMINARY MAGNITUDE OF 7.0 OCCURRED SOUTHEAST OF THE LOYALTY ISLANDS AT 0042 UTC ON TUESDAY OCTOBER 31 2017. * SMALL TSUNAMI WAVES HAVE BEEN OBSERVED. * 9 CM AMPLITUDE AT LIFOU NEW CALEDONIA 13 CM AMPLITUDE AT MARE NEW CALEDONIA 10 CM AMPLITUDE AT LENAKEL VANUATU RECOMMENDED ACTIONS ------------------- * PERSONS ALONG COASTAL AREAS NEAR THE EARTHQUAKE SHOULD BE OBSERVANT AND EXERCISE NORMAL CAUTION. OTHERWISE... NO ACTION IS REQUIRED. NEXT UPDATE AND ADDITIONAL INFORMATION -------------------------------------- * THIS WILL BE THE FINAL STATEMENT ISSUED FOR THIS EVENT UNLESS NEW INFORMATION IS RECEIVED OR THE SITUATION CHANGES. * AUTHORITATIVE INFORMATION ABOUT THE EARTHQUAKE FROM THE U.S. GEOLOGICAL SURVEY CAN BE FOUND ON THE INTERNET AT EARTHQUAKE.USGS.GOV/EARTHQUAKES -ALL LOWER CASE-. * FURTHER INFORMATION ABOUT THIS EVENT MAY BE FOUND AT PTWC.WEATHER.GOV AND AT WWW.TSUNAMI.GOV. * COASTAL REGIONS OF HAWAII... AMERICAN SAMOA... GUAM... AND CNMI SHOULD REFER TO PACIFIC TSUNAMI WARNING CENTER MESSAGES SPECIFICALLY FOR THOSE PLACES THAT CAN BE FOUND AT PTWC.WEATHER.GOV. * COASTAL REGIONS OF CALIFORNIA... OREGON... WASHINGTON... BRITISH COLUMBIA AND ALASKA SHOULD ONLY REFER TO U.S. NATIONAL TSUNAMI WARNING CENTER MESSAGES THAT CAN BE FOUND AT NTWC.ARH.NOAA.GOV.
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.