Guam Hazard Mitigation Plan - Western States Seismic Policy Council

SECTIONFIVERisk Assessmentto areas of dense development. Several slopes failed and several slopes were heavily destabilizedalong Marine Corps Drive in an area of commercial buildings. Landslides in this area crushedtwo cars. The steep face of a large quarry pit failed, causing the deformation of a large buildingon the flat ground surface above the slope, which was underlain by fill material. Many of theslide areas were observed to coincide with the location of limestone fault zones.Typhoons also lead to landslides in Guam. Although these events are not highly documented,records show that rain from Typhoon Chata’an resulted in numerous landslides.Mudslide: Similar to landslides, the occurrence of mudslides in Guam is not well documented.However, records indicate that mudslides occurred in the unpopulated mountainous areas ofGuam during Typhoon Chata’an.Post-Fire Debris Flow: Previous occurrences of post-fire debris flows have not beendocumented on Guam to date.Probability of Future EventsLandslide: The probability of future landslides is unknown. However, landslides are likely toresult from large earthquakes felt on Guam (4-5 years) and tropical cyclones and typhoons (onaverage, three tropical cyclones and one typhoon pass within 180 nautical miles of Guam eachyear).Mudslide: The probability of future mudslides is unknown. However, mudslides are likely tooccur after tropical cyclones and typhoons (on average, three tropical cyclones and one typhoonpass within 180 nautical miles of Guam each year), and other prolonged or intense rainstormevents which generally occur during the wet season from June – December.Post-Fire Debris Flow: Post-fire debris flows are most common in the 2 years after a fire; theyare usually triggered by heavy rainfall. Flooding and increased runoff may continue for severalyears after a fire, but it is unusual for post-fire debris flows to be produced beyond the secondrainy season after a wildfire. Some of the largest debris-flow events have been triggered by thefirst intense rainstorm of the storm season. However, because a number of complex factors leadto debris flow (rainfall, wildfire, and slope and soil conditions), the probability of future post-firedebris flows on Guam is unknown.5.3.13 TerrorismNatureNo universally accepted definition of terrorism is available; however, the Code of FederalRegulations defines terrorism as “... the unlawful use of force and violence against persons orproperty to intimidate or coerce a government, the civilian population, or any segment thereof, infurtherance of political or social objectives.” In general, terrorism is seen as violence againstcivilians to achieve a political or ideological objective through fear.Terrorism can occur in various forms: assassinations; kidnappings; hijackings; bomb scares andbombings; cyber attacks (computer-based); and the use of chemical, biological, nuclear, andradiological weapons. Concern is also growing about emerging infectious diseases and thepossibility of a bioterrorism attack.5-43