Tsunami Warning at PTWC
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This document provides information about tsunamis and the work of the Pacific Tsunami Warning Center (PTWC). The PTWC monitors for earthquakes, landslides, and volcanic eruptions that could trigger tsunamis in the Pacific Ocean and issues warnings. The document outlines the four main steps of the PTWC's operations: 1) seismic analysis to determine earthquake details, 2) message dissemination through various channels, 3) tsunami forecasting using modeling, and 4) sea level monitoring with sensors. The goal is to detect potential tsunamis as quickly as possible and provide warnings to save lives.
Tsunami Warning at PTWC
- 1. Brian Shiro NOAA Pacific Tsunami Warning Center SOI R/V Falkor 22 May 2014 Tsunami Warning at PTWC
- 2. Japan – 11 March 2011
- 3. The word “tsunami” Sometimes tsunamis are incorrectly called “tidal waves” or “seismic sea waves.” “tsu” = harbor “nami” = wave
- 4. What is a tsunami? A tsunami is a series of long-period waves created by an abrupt disturbance that displaces a large amount of water. Caused by: 72% 2% 10% 11% 5% Earthquakes Landslides Volcanoes Atmosphere Other/Unknown source: NOAA NGDC Iceberg calving, Asteroid impact (no recorded history)
- 5. 59% 12% 25% 4% Pacific Mediterranean Atlantic Indian Where do tsunamis occur? Whole Historical Record 77% 10% 9% 4% Pacific Mediterranean Atlantic Indian Just 1900-present (no Mediterranean bias) source: NOAA NGDC
- 7. Local/Regional tsunamis with deaths <1000 km from source source: USGS NEIC
- 8. Ocean-wide tsunamis with deaths >1000 km from source source: USGS NEIC
- 9. Ring of Fire Subduction zones produce Earthquakes, Volcanoes, & Tsunamis.
- 10. Normal vs. Tsunami waves Normal Waves: • Movement of uppermost layer of water only, motion diminishes with depth • Caused by wind or storm surge • Wavelength: 30-200 m, Period: 1-30 s • Speed: 15-115 km/h (function of wave period à dispersive) Tsunami Waves: • Movement of entire water column down to sea floor • Caused by tides or tsunamis • Wavelength: 80-500 km, Period: 5-60 m • Speed: 50-900 km/h (function of depth only) h Called “Deep Water Waves” because h > L/2 L h h Called “Shallow Water Waves” because h < L/20 L h
- 11. Tsunami waves are fast … about 900 km/hr The deeper the water, the faster the tsunami. V = sqrt(g*h)
- 12. but seismic waves are faster! Seismic waves travel at the speed of sound in rock: • about 16-25,000 km/hr Tsunami waves are much slower than seismic waves: • about 50-900 km/hr Therefore, it is possible to issue a warning for a tsunami ahead of its arrival!
- 13. Pacific Tsunami Warning Center • Established in 1949 (following 1946 tsunami) • International center for Pacific Ocean since 1969 (following 1960 tsunami) • Interim center for Indian Ocean 2005-2013 (following 2004 tsunami) • Interim center for Caribbean Sea since 2007 PTWC Scientific Staff tripled from 4-12 in 2005. (2 watchstanders on duty 24x7) PTWC is moving to its new home on Ford Island, Pearl Harbor in 2014.
- 14. PTWC AOR as of 2014
- 15. Alarm!
- 16. PTWC Operations 1. Seismic Analysis 2. Message Dissemination 3. Tsunami Forecasting 4. Sea Level Monitoring
- 17. Step 1: Seismic Analysis Determine: Location, Origin time Depth, and Magnitude
- 18. Sources: IRIS, USGS, IMS, etc. Seismic Network
- 19. Earthquake Magnitude 1 magnitude change = 32 times of energy increase
- 20. PTWC Operations 1. Seismic Analysis 2. Message Dissemination 3. Tsunami Forecasting 4. Sea Level Monitoring
- 21. Step 2: Message Dissemination If the earthquake is in PTWC’s AOR, shallow (< 100 km), and meets a magnitude threshold, PTWC will issue a tsunami message. Magnitude (MW) Message Type 6.5-7.5 Tsunami Information Bulletin 7.6-7.8 Fixed Regional Tsunami Warning ≥7.9 Expanding Regional Tsunami Watch/Warning Large tsunami confirmed Pacific Ocean-wide Tsunami Warning Pacific Ocean Warning Criteria
- 22. Message PathwaysAFTN airports worldwide GTS/NMC international NWW USA & Canada Telex Chile IDN Hawaii HAWAS Hawaii NAWAS USA & Canada Telephone warning points FAX warning points Website anyone Email anyone RSS Feeds anyone EMWIN warning points SMS RANET text phone internet
- 23. PTWC Operations 1. Seismic Analysis 2. Message Dissemination 3. Tsunami Forecasting 4. Sea Level Monitoring
- 24. Step 3: Tsunami Forecasting Computing tsunami arrival time is easy. • Analytical calculation Estimating tsunami amplitude at the shore is harder. • Numerical computation
- 25. Scenario: M9 in Kuril Islands Hypothetical Scenario Illustrates PTWC’s new RIFT model- based products coming in late 2014
- 26. Example: M8.3 Kuril Islands, 15 Nov 2006
- 29. PTWC Operations 1. Seismic Analysis 2. Message Dissemination 3. Tsunami Forecasting 4. Sea Level Monitoring
- 30. Step 4: Sea Level Monitoring Measure and record ocean height at a sea level gauge (often called “tide gauge”. Transmission delays vary from near real time to up to an hour. Different styles: • Float-operated • Pressure sensor • Radar
- 31. Sources: GLOSS, NOAA, UHSLC, etc. Sea Level Network
- 32. DART System Deep-ocean Assessment and Reporting of Tsunamis 44 worldwide (34 in Pacific) Operated by NOAA NDBC
- 33. The future (Smith et al 2005) (Occhipinti et al 2008) satellite altimetry ionospheric TEC GPS, over-the-horizon radar, infrasound, and …
- 34. Tsunami Safety for Boaters
- 35. Pau Brian Shiro brian.shiro@noaa.gov Pacific Tsunami Warning Center http://ptwc.weather.gov
- 36. Extra Slides
- 37. Tsunami Warning Products Tsunami Warning. A damaging tsunami is expected. Coastal evacuation is necessary. (Forecasted tsunami amplitude is >1 m) Tsunami Advisory. A tsunami is expected, but it is not expected to be large enough to cause more than minor flooding. Evacuation is not necessary, but stay off the beach and out of the water. (Forecasted tsunami amplitude is 0.3-1 m) Tsunami Watch. An earthquake has occurred which may have generated a damaging tsunami. The tsunami is at least three hours away. Tsunami Information Bulletin. A large earthquake has occurred but no tsunami is expected.
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