Addendum A: Regional tsunami hazard assessment for Pasagshak, Alaska

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What does this data set describe?

Title:
Addendum A: Regional tsunami hazard assessment for Pasagshak, Alaska
Abstract:
Report of Investigation 2019-6A, Addendum A: Regional tsunami hazard assessment for Pasagshak, Alaska, provides an estimated extent of the tsunami hazard zone in the community of Pasagshak, Alaska. Pasagshak is a small community on Kodiak Island, about 70 km (44 mi) south of Kodiak. The highest resolution bathymetric grid that covers this community is the level 3 grid with a grid size of about 45x82 m. We estimate the extent of the tsunami hazard zone in Pasagshak by running all nine tsunami scenarios described in the main report (Report of Investigation 2019-6). Each model run was performed for 12 hours of tsunami propagation to account for all waves in the wave train, including any secondary (reflected) waves. The maximum value of the tsunami height based on a composite of all scenarios, multiplied by a safety factor of 1.3, results in a maximum estimated runup height of 39 m (128 ft) for the community of Pasagshak. We illustrate the maximum estimated tsunami runup on land by drawing an elevation contour on the 5-m (16-ft) resolution community topographic map that corresponds to the maximum modeled wave height offshore. The complete report and digital data are available from the DGGS website: http://doi.org/10.14509/30763.
Supplemental_Information:
hazard-boundary:    Shapefile(s) depicting maximum assumed runup heights with an included safety factor. These lines are intended to be utilized as a basis for local tsunami hazard planning and the development of evacuation maps.
  1. How might this data set be cited?
    Suleimani, E.N., Salisbury, J.B., and Nicolsky, D.J., 2022, Addendum A: Regional tsunami hazard assessment for Pasagshak, Alaska: Report of Investigation RI 2019-6A, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 4 p., 2 sheets
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -152.508201
    East_Bounding_Coordinate: -152.410671
    North_Bounding_Coordinate: 57.513033
    South_Bounding_Coordinate: 57.421956
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2019
    Ending_Date: 2020
    Currentness_Reference:
    publication date
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: report, and, digital, data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a vector data set.
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest .000001. Longitudes are given to the nearest .000001. Latitude and longitude values are specified in decimal degrees. The horizontal datum used is WGS84.
      The ellipsoid used is WGS 84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257223563000025.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: Mean Higher High Water
      Depth_Resolution: 1
      Depth_Distance_Units: meter
      Depth_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    ri2019-6a-hazard-boundary-pasagshak.shp
    Shapefile(s) depicting maximum assumed runup heights with an included safety factor. These lines are intended to be utilized as a basis for local tsunami hazard planning and the development of evacuation maps. File format: shapefile (Source: Alaska Earthquake Center, Geophysical Institute, University of Alaska, this report)

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
  2. Who also contributed to the data set?
    This report was funded by the U.S. Department of Commerce/National Oceanic and Atmospheric Administration (NOAA) through National Tsunami Hazard Mitigation Program Award NA20NWS4670057 to the Alaska Division of Homeland Security and Emergency Management. This does not constitute an endorsement by NOAA. Numerical calculations for this work were supported by High Performance Computing (HPC) resources at the Research Computing Systems unit at the Geophysical Institute, University of Alaska Fairbanks.
  3. To whom should users address questions about the data?
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.

Why was the data set created?

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.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2011 (process 1 of 4)
    Model validation - The numerical model that we used for simulation of tsunami wave propagation and runup was validated through a set of analytical benchmarks and tested against laboratory data. The model solves water equations using a finite-difference method on a staggered grid. See the accompanying report for more detail and additional model information.
    Date: 2019 (process 2 of 4)
    Development of nested grids - To support inundation modeling of coastal areas in Alaska, we used a series of nested telescoping grids, or digital elevation models (DEMs), as input layers for tsunami inundation modeling and mapping. These grids of increasing resolution allowed us to propagate waves generated by various sources to Pasagshak. In order to propagate a wave from its source to various coastal locations, we used embedded grids, placing a large, coarse grid in deep water and coupling it with smaller, finer grids in shallow water areas. The extent of each grid used for our tsunami inundation mapping is listed in the accompanying report.
    Date: 2020 (process 3 of 4)
    Numerical simulations of hypothetical tsunami scenarios - We assessed hazards related to tectonic tsunamis in Pasagshak by performing model simulations for each hypothetical source scenario. For each tsunami scenario, we first calculate the maximum tsunami wave heights in the highest-resolution grid over the course of the entire model run in the following way: at each grid point, the tsunami wave height is computed at every time step during the tsunami propagation time and the maximum value is kept. Then we compute the composite maximum tsunami wave height from all considered scenarios by again choosing the maximum value for each grid point among all scenarios, and plot the results.
    Date: 2021 (process 4 of 4)
    Tsunami hazard boundary - After calculating the maximum tsunami height for every grid point in the vicinity of a community, we multiply each highest value grid point by a safety factor of 1.3 (30%) and define it as the maximum runup height. Then we find an elevation contour on the DCRA community map that corresponds to this maximum runup height. This contour is the tsunami hazard boundary.
  3. What similar or related data should the user be aware of?
    Suleimani, E.N., Nicolsky, D.J., and Koehler, R.D., 2017, Updated tsunami inundation maps of the Kodiak area, Alaska: Report of Investigation RI 2017-8, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 38 p., 10 sheets, scale 1:30,000
    Suleimani, E.N., Salisbury, J.B., and Nicolsky, D.J., 2021, Tsunami inundation maps for Akhiok, Chiniak, Old Harbor, Ouzinkie, and Port Lions on Kodiak Island, Alaska: Report of Investigation RI 2021-6, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 73 p., 5 sheets

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    The hydrodynamic model used to calculate propagation and runup of tectonic tsunamis is a nonlinear, flux-formulated, shallow-water model and has passed the required tests for official use in producing tsunami inundation maps. Most of the uncertainties in the numerical calculations originate from the tsunamigenic earthquake sources used in the models. Uncertainties in the earthquakes, such as the precise location, magnitude, and slip distribution, are the largest sources of error. The direction, amplitude, and arrival times of incoming waves are determined by the initial ocean surface conditions immediately following the earthquake. Therefore, the modeling results are particularly sensitive to the details of the tsunamigenic earthquake rupture, and when the earthquake occurs close to a community, discrepancies can be exacerbated. Furthermore, our assessment of potential earthquake scenarios is by no means exhaustive but represents the best estimate of the locations and sizes of potential tsunami-generating events. It is possible that other unrecognized earthquake scenarios could present hazards to these communities. This DGGS Report of Investigations is a final report of scientific research. Several scientists familiar with the subject matter provided technical reviews. Uncertainties associated with the depiction or interpretation of various features are discussed in the accompanying report.
  2. How accurate are the geographic locations?
    We provide an estimation of the tsunami hazard zone by extrapolating the maximum composite tsunami wave height onto land according to the tsunami scenarios described accompanying report. We account for uncertainties inherent in this method by applying a safety scaling factor of 30 percent to the estimated hazard zone.
  3. How accurate are the heights or depths?
    The vertical accuracy of the inundation modeling is dependent on the accuracy and resolution of the digital elevation models (DEMs) and tidal datum values that were used to compile the computational grid. Prior to scenario modeling, bathymetric data were shifted to use Mean Higher High Water (MHHW) as the vertical datum. The highest resolution grid that covers this community is the level 3 grid with the grid size of about 45x82 m. The spatial resolution of this grid satisfies the National Oceanic and Atmospheric Administration's minimum recommended requirements for estimation of the tsunami hazard zone. The depths of inundation shown should be used only as a guideline for emergency planning and response action. Actual inundation water depth will depend on specifics of the earth deformations, on-land construction, and tide level, and they may differ from areas shown by this data. The information is intended to permit state and local agencies to plan emergency evacuation and tsunami response actions in the event of a major tsunamigenic earthquake. These results are not intended for land-use regulation or building-code development. We provide additional details about DEM and grid development in the accompanying report.
  4. Where are the gaps in the data? What is missing?
    The results of our modeling have been completed using the best information available and are believed to be accurate; however, their preparation required many assumptions and actual conditions during a tsunami event may vary from those considered.
  5. How consistent are the relationships among the observations, including topology?
    Not applicable

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints:
This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).
Use_Constraints:
This dataset includes results of numerical modeling of earthquake-generated tsunami waves for a specific community. Modeling was completed using the best information and tsunami modeling software available at the time of analysis. They are numerical solutions and, while they are believed to be accurate, their ultimate accuracy during an actual tsunami will depend on the specifics of earth deformations, on-land construction, tide level, and other parameters at the time of the tsunami. Actual areas of inundation may differ from areas shown in this dataset. Landslide tsunami sources may not be included in the modeling due to unknown potential impact of such events on a given community; please refer to accompanying report for more information on tsunami sources used for this study. The limits of inundation shown should only be used as a general guideline for emergency planning and response action in the event of a major tsunamigenic earthquake. These results are not intended for any other use, including land-use regulation or actuarial purposes. Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
  1. Who distributes the data set? (Distributor 1 of 1)
    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK
    USA

    (907)451-5020 (voice)
    (907)451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.
  2. What's the catalog number I need to order this data set? RI 2019-6A
  3. What legal disclaimers am I supposed to read?
    The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 30-Mar-2022
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
3354 College Road
Fairbanks, AK
USA

(907)451-5020 (voice)
(907)451-5050 (FAX)
dggspubs@alaska.gov
Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

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