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Joint Typhoon Warning Center (JTWC)

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Tsunami Frequently Asked Questions

  • What is the Joint Typhoon Warning Center’s (JTWC) role involving earthquake reporting?
    • Constantly monitors the world-wide seismic network for earthquake activity.
    • Provides continuous updates and liaison functions via telephone, chat, and classified/unclassified web-sites.
  • What are the criteria for a tsunami response? Earthquakes meeting the following conditions initiate a response:
    • ≥ 6.5 (Moment Magnitude Scale)
    • < 100 kilometers deep
    • coastal or offshore
  • How quickly does JTWC begin warning on an Earthquake meeting warning criteria for a tsunami?
    • JTWC’s initial notification will be posted within 15 minutes of an earthquake meeting warning criteria’s occurrence.
  • What information does JTWC include in their initial notification?
    • Initial notifications include: location, depth, magnitude, time of occurrence, and a preliminary assessment of tsunami potential.
  • Who does JTWC notify?
    • Notifications are sent to tactical elements via classified chat, unclassified emergency management assets via the CNIC C4I suite, the general DOD community via JTWC classified and unclassified web-sites.  Naval staffs and METOC entities are also notified via classified and unclassified email.
  • If Tsunami Centers like PTWC and NTWC warn on all Tsunami’s that affect the Pacific Ocean and North America, why is JTWC’s Tsunami mission important?
    • JTWC monitors worldwide tsunami activity and conveys messages directly to DoD assets through classified and unclassified means in order to ensure that all potentially affected DoD assets, even ships underway, are aware of potential dangers.
    • Repackages PTWC and NTWC warnings to ensure delivery and awareness to all DoD assets that could be impacted.
  • Once an earthquake meeting warning criteria occurs, what websites does JTWC post to?
  • What products are initially posted to the JTWC Websites?
    • Warning Texts
    • Asset Impact Table depicting arrival times and both forecast and observed heights.
    • Tsunami Time Travel map depicting tsunami travel time from epicenter with estimated tsunami arrival times at points downstream.
  • What products are posted to JTWC Websites following the initial notification?
    • JTWC disseminates bulletin information from the Pacific Tsunami Warning Center (PTWC) or the National Tsunami Warning Center (NTWC) to predetermined DOD decision nodes and installations.
    • Updated Asset Impact Table
    • Additional data from repackaged from PTWC/NTWC can include the following:
      • Fine Resolution Predicted Wave Amplitude and Energy Propagation Maps
      • Coastal hazard and localized forecast flood risk and amplitude maps for 74 specific areas (54 Pacific U.S. West Coast and U.S. Territories) of concern.
  • When does JTWC update the Asset Impact Table?
    • JTWC issues near real-time updates to Asset Impact Table.
    • Update sources include tidal gauges and DART buoys as well as higher resolution model data from NOAA to assess and update potential hazards and impacts.