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We evaluate potential tsunami hazards for the Kodiak Island communities of Akhiok, Chiniak, Old Harbor, Ouzinkie, and Port Lions, Alaska, by numerically modeling the extent of inundation from tsunami waves generated by hypothetical earthquakes. Worst-case inundation scenarios are defined by analyzing the tsunami dynamics related to various plausible earthquake slip distributions along the Alaska-Aleutian megathrust. Potential worst-case tsunami sources include megathrust earthquakes in the Kodiak Island region. A hypothetical earthquake near Kodiak Island with maximum slip distributed at depths between 10 and 20 km (6.2-12.4 mi) with a splay fault dipping 60° in the Albatross fault zone results in "worst case" tsunami inundation for Akhiok, and an earthquake with maximum slip distributed at depths between 0 and 10 km (0-6.2 mi) with a splay fault dipping 30° in the backstop splay zone is the "worst case" scenario for the remaining communities. The maximum predicted overland flow depths in the communities ranges from 10 to 25 m (33 to 82 ft), and the currents in community harbors could be as strong as 8.4 m/sec (16.3 knots). Dangerous wave activity is expected to last for at least 12 hours after the hypothetical worst-case earthquakes. Results presented here are intended to provide guidance to local emergency management agencies for tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami damage. [ABSTRACT FROM AUTHOR]

We assess potential tsunami hazards for six communities in Southeast Alaska: Kasaan, Klawock, Metlakatla, Pelican, Point Baker, and Port Protection. These communities have no high-resolution bathymetry or topography, therefore we conduct tsunami hazard assessments for these areas at the regional scale. The regional approach is a suitable, costeffective approximation and replacement for high-resolution tsunami inundation maps. The primary tsunami hazard considered for these communities originates from tsunamigenic earthquakes along the Alaska-Aleutian subduction zone across the Gulf of Alaska. We numerically model tsunami waves generated by four different megathrust earthquakes and develop approximate tsunami hazard maps for the six communities. The hypothetical tsunami scenarios that we examined include variations of an extended 1964 rupture, megathrust earthquakes in the Prince William Sound and Alaska Peninsula regions, and a Cascadia megathrust earthquake. We do not include impacts of subaerial or submarine landslide tsunami sources, as that is beyond the scope of this study. The maximum runup heights from tectonically-generated tsunamis are 1.4 m (4.6 ft) in Kasaan, 4 m (13 ft) in Klawock, 1 m (3.3 ft) in Metlakatla, 5 m (16 ft) in Pelican, 1.3 m (4.3 ft) in Point Baker, and 2.6 m (8.5 ft) in Port Protection. Results presented here are intended to provide guidance to local emergency management agencies in initial tsunami inundation assessment, evacuation planning, and public education for mitigation of future tsunami hazards. [ABSTRACT FROM AUTHOR]

We assess potential tsunami hazards for the communities of Dillingham, Nelson Lagoon, and Platinum in Bristol Bay, and St. Paul and St. George on the Pribilof Islands. The Bristol Bay communities have no high-resolution bathymetry or topography, therefore we conduct tsunami hazard assessments for these areas at the regional scale. The regional approach is a suitable, cost-effective approximation and replacement for high-resolution tsunami inundation maps. The Pribilof Islands communities do have the high-resolution baseline data necessary to produce high-resolution maps. The primary tsunami hazard considered for communities in this report originate from tsunamigenic earthquakes along the Alaska-Aleutian subduction zone and from underwater slope failures in the Bering Sea. Volcanic tsunamis are known to have generated waves up to 12 m in Bristol Bay about 3,500 years ago, but we do not model them in this study due to insufficient data on locations and volumes of these potential hazards. We numerically model tsunamis generated by eight different megathrust earthquakes and two landslide sources, analyze tsunami wave dynamics, and develop tsunami hazard maps. The tectonic tsunami scenarios that we examined simulate Mw 9.2 megathrust earthquakes with a slip distribution in the 5-35 km (3-22 mi) depth range along the Aleutian megathrust. The landslide tsunami scenarios include submarine mass failures on both sides of Umnak Plateau. The maximum assumed runup heights are 1.4 m (4.6 ft) for Dillingham, 3.5 m (11.5 ft) for Nelson Lagoon, and 4.9 m (16 ft) for Platinum. The maximum calculated tsunami runup in St. Paul is 16 m (52.5 ft); it is 5m (16 ft) in St. George, and 11 m (36 ft) near the St. George airport. Results presented here are intended to provide guidance to local emergency management agencies in initial tsunami inundation assessment, evacuation planning, and public education for mitigation of future tsunami hazards. [ABSTRACT FROM AUTHOR]

We assess potential tsunami hazard for three coastal communities in Southeast Alaska: Port Alexander, Craig, and Ketchikan. The primary tsunami hazard for these communities is considered to be far-field, with the major threat originating from tsunamigenic earthquakes along the Alaska-Aleutian subduction zone across the Gulf of Alaska. We numerically model tsunami waves generated by four different megathrust earthquakes and develop approximate tsunami hazard maps for the three communities. The hypothetical tsunami scenarios that we examined include variations of an extended 1964 rupture, megathrust earthquakes in the Prince William Sound and Alaska Peninsula regions, and a Cascadia megathrust earthquake. The maximum runup heights are 4 m (13.1 ft) in Port Alexander, 3.2 m (10.5 ft) in Craig, and 1 m (3.3 ft) in Ketchikan. Results presented here are intended to provide guidance to local emergency management agencies in initial tsunami inundation assessment, evacuation planning, and public education for mitigation of future tsunami hazards. [ABSTRACT FROM AUTHOR]

We re-evaluate the potential tsunami hazard for the communities of Homer and Seldovia by numerically modeling the extent of inundation from tsunami waves generated by earthquakes and submarine landslides. Hypothetical worst-case scenarios are defined by analyzing the tsunami dynamics related to various plausible earthquake slip distributions along the Alaska-Aleutian megathrust. Potential tsunami sources include megathrust earthquakes in the Prince William Sound, Kenai Peninsula, and Kodiak Island regions. We consider scenarios similar to that of the 2011 Tohoku earthquake in Japan, with maximum slip located on a shallow portion of the plate interface close to the seafloor trench. We also consider local underwater slope failure scenarios for Kachemak Bay. The maximum predicted wave height from a tectonic tsunami is 10-12 m (33-40 ft) in Homer and 10-11 m (33-36 ft) in Seldovia, while the maximum landslide-generated tsunami may reach an elevation of up to 4 m (13 ft) on Homer Spit. Results presented here are intended to provide guidance to local emergency management agencies for tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards. This report updates the previous assessment of tsunami hazard for Homer and Seldovia published in 2005. [ABSTRACT FROM AUTHOR]

In this report we evaluate potential tsunami hazards for the southeastern Alaska communities of Skagway and Haines and numerically model the extent of inundation from tsunami waves generated by tectonic and submarine landslide sources. We calibrate our tsunami model by numerically simulating the 2011 Tohoku, Japan tsunami at Skagway and comparing our results to instrument records. Analysis of calculated and observed water level dynamics for the 2011 event in Skagway reveals that the model underestimates the observed wave heights in the city by a factor of 1.5, likely due to complex tsunami-tide interactions. We compensate for this underestimation numerically by increasing the coseismic slip of the hypothetical tsunami sources in our models. Potential hypothetical maximum credible tsunami sources include variations of the extended 1964 rupture and megathrust earthquakes in the Prince William Sound and Alaska Peninsula regions. Local underwater landslide events in Taiya, Chilkoot, and Chilkat inlets are also considered as possible tsunamigenic scenarios. The results show that the maximum predicted wave height resulting from a tectonic tsunami is 2-3 m (7-10 ft) in Skagway and Haines, while the maximum landslide-generated tsunami may cause a runup of 15-16 m (49-52 ft). Results presented here are intended to provide guidance to local emergency management agencies in tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards. [ABSTRACT FROM AUTHOR]

In this report we evaluate potential tsunami hazards for the southeastern Alaska community of Juneau and numerically model the extent of inundation from tsunami waves generated by tectonic and submarine landslide sources. We calibrate our tsunami model by numerically simulating the 2011 Tohoku tsunami at Juneau and comparing our results to instrument records. Analysis of calculated and observed water level dynamics for the 2011 event in Juneau reveals that the model underestimates the observed wave heights in the city by a factor of two, likely due to complex tsunami-tide interactions. We compensate for this numerical underestimation by doubling the coseismic slip of the hypothetical tsunami sources in our models. Potential hypothetical maximum credible tsunami sources include variations of the extended 1964 rupture and megathrust earthquakes in the Prince William Sound and Alaska Peninsula regions. Local underwater landslide events in Lynn Canal, in Favorite, Saginaw, and Gastineau channels, and in Taku Inlet are also considered as possible tsunamigenic scenarios. The results show that the maximum predicted wave height in the Juneau area resulting from a tectonic tsunami is 2-3 m (6-10 ft), while a landslide-generated tsunami may cause a run-up of 15-16 m (49-52 ft) along the Fritz Cove shoreline and potentially flood portions of the airport. Results presented here are intended to provide guidance to local emergency management agencies in tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards. [ABSTRACT FROM AUTHOR]

The authors evaluated potential tsunami hazard for the communities of Kodiak, Womens Bay, and for the U.S. Coast Guard base on Kodiak Island by numerically modeling the extent of inundation from tsunami waves generated by hypothetical earthquake sources. Worst-case hypothetical scenarios are defined by analyzing results of a sensitivity study of the tsunami dynamics related to various slip distributions along the Alaska-Aleutian megathrust. The worst-case scenarios for the Kodiak communities are thought to be the subduction zone earthquakes offshore Kodiak Island with their greatest slip at 5-35 km (3.1-22 mi) depth. We also consider earthquakes as large as the 2011 Tohoku earthquake in Japan with the greatest slip located close to the trench area. The results show that the maximum predicted flow depth in downtown Kodiak could reach 13 m (42.6 ft), and the currents in Kodiak's Inner Harbor could be as strong as 3.7 m/sec (7.2 knots). The dangerous wave activity is expected to last for at least 10 hours after the earthquake. Results presented here are intended to provide guidance to local emergency management agencies in tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards. This report updates the previously published assessment of tsunami hazard for the Kodiak Island communities. [ABSTRACT FROM AUTHOR]

Potential tsunami hazard for the Alaska Peninsula communities of Chignik and Chignik Lagoon is evaluated by numerically modeling the extent of inundation from tsunami waves generated by hypothetical earthquake sources. Worst-case hypothetical scenarios are defined by analyzing results of a sensitivity study of the tsunami dynamics related to various slip distributions along the Alaska-Aleutian megathrust. The worst-case scenarios for Chignik area communities are thought to be thrust earthquakes along the Alaska Peninsula with their greatest slip at 5-35 km (3.1-22 mi) depth. We also consider Tohoku-type ruptures and an outer-rise rupture along the Alaska Peninsula. The maximum predicted water depth on Anderson Street in Chignik Bay is about 31 m (102 ft), while the water depth on Henry Street in Chignik Lagoon is about 11 m (36ft). Maximum current velocity in the ocean could exceed 9 m/s (17 kt) and significant wave action could continue for at least 8 hours after the earthquake. Results presented here are intended to provide guidance to local emergency management agencies in tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards. [ABSTRACT FROM AUTHOR]

Potential tsunami hazard for the Umnak Island community of Nikolski is evaluated by numerically modeling the extent of inundation from tsunami waves generated by hypothetical earthquake sources. Worst-case hypothetical scenarios are defined by analyzing results of a sensitivity study of the tsunami dynamics related to various slip distributions along the Aleutian megathrust. The worst-case scenarios for Nikolski are thought to be thrust earthquakes in the Umnak Island region with their greatest slip at 10-30 km (6.2-19 mi) depth. We also consider Tohoku-type ruptures and an outer-rise rupture in the area of Umnak Island. The maximum predicted water depth on Main Street is about 15 m (49 ft), while the maximum current velocity in Mueller Cove could exceed 8 m/s (15 kt) and significant wave action could continue for at least 8 hours after the earthquake. Results presented here are intended to provide guidance to local emergency management agencies in tsunami inundation assessment, evacuation planning, and public education to mitigate future tsunami hazards. [ABSTRACT FROM AUTHOR]

In this report we evaluate potential tsunami hazards for the southeastern Alaska community of Yakutat and numerically model the extent of inundation from tsunami waves generated by tectonic and landslide sources. We use numerical modeling of historical tsunami events at Yakutat, such as the tsunami triggered by the 1964 Great Alaska Earthquake, and the tsunami waves generated by the recent 2011 Tohoku earthquake, to verify the tsunami model. Potential hypothetical tsunami sources include variations of the extended 1964 rupture, megathrust earthquakes in the Prince William Sound and Alaska Peninsula regions, and earthquakes in the Yakataga-Yakutat area, including the historical September 10, 1899, earthquake. Local underwater landslide events in Monti Bay are also considered as possible tsunamigenic scenarios. Numerical modeling results, combined with historical observations in the region, are intended to provide guidance to local emergency management in tsunami hazard assessment, evacuation planning, and public education for the reduction of future tsunami hazard. [ABSTRACT FROM AUTHOR]

In this report, we evaluate potential tsunami hazards for southeastern Alaska communities of Elfin Cove, Gustavus, and Hoonah and numerically model the extent of inundation from tsunami waves generated by tectonic and landslide sources. We perform numerical modeling of historic tsunami events, such as the tsunami triggered by the 1964 Great Alaska Earthquake, and the tsunami waves generated by the recent 2011 Tohoku and 2012 Haida Gwaii earthquakes. Hypothetical tsunami scenarios include variations of the extended 1964 rupture, megathrust earthquakes in the Prince William Sound and Alaska Peninsula regions, and a Cascadia megathrust earthquake. Local underwater landslide events in Taylor Bay and Port Frederick, and a rockslide in Tidal Inlet are also considered as possible tsunamigenic scenarios. Numerical modeling results, combined with historical observations in the region, are intended to provide guidance to local emergency management in tsunami hazard assessment, evacuation planning, and public education for the reduction of future tsunami risk. [ABSTRACT FROM AUTHOR]

Potential tsunami hazards for the community of Chenega Bay, located on Evans Island between Sawmill and Crab bays, were evaluated by numerically modeling the extent of inundation from tsunami waves generated by earthquakes. Tsunami scenarios include a repeat of the tsunami triggered by the 1964 Great Alaska Earthquake, as well as tsunamis generated by a hypothetically extended 1964 rupture, a hypothetical Cascadia megathrust earthquake, a hypothetical earthquake in the Kodiak asperity of the 1964 rupture, and a hypothetical Tohoku-type rupture in the Gulf of Alaska region. Results of numerical modeling are verified by simulations of the tectonic tsunami observed in Chenega Cove during the 1964 earthquake. The results presented here are intended to provide guidance to local emergency management agencies in tsunami-hazard assessment, evacuation planning, and public education, to reduce damages from future tsunami hazards. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate tsunami hazard for the community of Seward and northern Resurrection Bay area, Alaska. This report will provide guidance to local emergency managers in tsunami hazard assessment. We used a numerical modeling method to estimate the extent of inundation by tsunami waves generated from earthquake and landslide sources. Our tsunami scenarios included a repeat of the tsunami of the 1964 Great Alaska Earthquake, as well as tsunami waves generated by two hypothetical Yakataga Gap earthquakes in northeastern Gulf of Alaska, hypothetical earthquakes in Prince William Sound and Kodiak asperities of the 1964 rupture, and local underwater landslides in Resurrection Bay. Results of numerical modeling combined with historical observations in the region are intended to help local emergency officials with evacuation planning and public education for reducing future tsunami risk. [ABSTRACT FROM AUTHOR]