How do scientists know if a tsunami is coming after an undersea earthquake?

After a large offshore earthquake, warning centers rapidly estimate the quake's magnitude, depth, and whether the fault motion could have displaced the seafloor vertically. If the event looks tsunamigenic, they use DART buoys — Deep-ocean Assessment and Reporting of Tsunamis — to detect pressure changes from passing waves. Coastal tide gauges then help confirm the wave's size and timing. This system reduces false alarms and gives emergency agencies better information for evacuations. Tsunami warning networks exist in the Pacific, Indian Ocean, and other vulnerable regions.