Guam experiences some of the most intense tropical cyclones (typhoons) in the world. Guam is exposed to substantial typhoon risk due to its location in the southern end of the Mariana Island chain. Typhoons in this region pose a threat all year long, but are most frequent between the months of June and December. During the past 57 years, 19 storms have passed over Guam, and many more have passed nearby. Because the diameter of a typhoon can measure over 100 miles, typhoons do not have to pass directly over Guam to cause damage.
One of the most intense typhoons to ever strike Guam was typhoon Karen, which passed over the southern part of the island in 1962. Wind gusts estimated near 185 mph destroyed 95% of all homes on the island.
Other notable typhoons impacting Guam include Super Typhoon Pongsonga in 2002 with measured wind gusts up to 184 mph
Earthquake risk in Guam is caused by the island’s proximity to the Mariana Trench, where the subduction of the Pacific Plate beneath the Philippine Plate occurs. This motion leads to earthquakes throughout the Mariana Island chain.
The 1849 Guam earthquake and tsunami caused extensive damage to Agana, the largest city on Guam, as did the 1902, 1975, and 1978 earthquakes. The 1993 Guam earthquake measured Mw7.8, which was larger than the maximum event estimated by most scientists for that area at the time. Several high-rise buildings in Tumon Bay, mostly hotels, sustained enough damage to warrant demolition, while liquefaction and lateral spreading resulted in an estimated $8-10 million in repair costs to the main port for Guam.