Micronesia

The Federated States of Micronesia encompasses four states — Pohnpei, Chuuk, Yap, and Kosrae — spread across the western-central Pacific, with significant variation in seismic hazard depending on proximity to active plate boundaries. Yap State, in the westernmost position, lies closest to the Yap Trench, where the Pacific Plate subducts beneath the Caroline microplate, generating moderate seismicity in the Yap subduction system. The Caroline microplate itself is bounded to the north by the Mariana [[subduction-zone]] and to the south and east by complex transform and spreading boundaries. Chuuk and Pohnpei sit on the Pacific Plate interior and are further from active boundaries, experiencing more distant seismicity. Kosrae in the east is closest to the Pacific Plate's relatively stable interior. The entire Micronesian archipelago faces [[tsunami]] exposure from great earthquakes in the surrounding Pacific Ring of Fire systems, particularly the Japan-Mariana arc, the Tonga system, and the Aleutian arc.

Historical earthquake records for the Federated States of Micronesia primarily capture felt events from regional sources rather than locally generated damaging earthquakes. The 1993 Guam earthquake (magnitude 8.1) was felt across Micronesia and generated a regional [[tsunami]] warning. Events from the Mariana [[subduction-zone]] periodically produce felt shaking in Yap and the Caroline Islands. The 2011 Tohoku earthquake and tsunami generated wave heights that were recorded at FSM tide gauge stations, though without significant inundation. Yap has experienced several locally felt events from the Yap subduction system, including a magnitude 6.9 earthquake in 2011 that caused felt shaking but limited damage. The FSM participates in the Pacific Tsunami Warning System through the Pacific Community (SPC) regional disaster risk coordination framework.

The geological diversity of the Federated States of Micronesia reflects the different origins of its component island groups. Yap's main islands are composed of metamorphic and igneous rocks — remnants of the Philippine Sea Plate basement, making it geologically distinct from other Micronesian islands. The Truk (Chuuk) Lagoon islands are remnants of a large shield volcano that has largely subsided below sea level, leaving a fringing reef around the volcanic remnants. Pohnpei and Kosrae are younger shield volcanoes still above sea level, built on the Pacific Plate during the passage of hotspot plumes. The Caroline Plate on which parts of FSM sit is a small oceanic microplate bounded by complex transform faults and slow spreading centres; its tectonic activity is generally low but not negligible. [[seismic-wave]]s from the active Mariana arc and Yap trench are routinely recorded on seismometers across the FSM.