TSUNAMI RESEARCH GROUP
Augustine Volcano Eruption Oct. 6, 1883.
Non-Linear Shallow Water (NLSW) numerical simulations
Description: The tsunami was apparently generated by debris avalanche from the collapse of the northeast face of the peak. The slide consisted of about 0.5 cubic kilometers of material moving down from a peak height of 1300 meters and over a distance of about 6 to 7 kilometers including 2 kilometers of newly created land at Burr Point and 2.4 kilometers further underwater. The Non-Linear Shallow Water (NLSW) numerical model has been used to calculate the characteristics of the tsunami generated by a landslide into Cook Inlet from Augustine Volcano. The modeling predicts travel times of aprox. 50-75 minutes to the nearest populated areas, and indicates that significant wave amplification occurs near Mt. Iliamna on the western side of Cook Inlet, and near the Nanwelak and the Homer-Anchor Point areas on the east side of Cook Inlet. Tsunami deposits on Augustine Island indicate waves near the landslide source were more than 19 m high, while 1883 tsunami deposits in distant sites record waves 6-8 m high. Paleotsunami deposits were found at sites along the coast near Mt. Iliamna, Nanwelak, and Homer, consistent with numerical modeling indicating significant tsunami wave amplification occurs in these areas.
Reference: Beget J. E., Z. Kowalik (2006), Confirmation and calibration of computer modeling of tsunami produced by Augustine volcano, Alaska. Science of Tsunami Hazards,Vol. 24, No. 4, page 257. (Download PDF file, size: 689KB)
COOK INLET MAP
Figure 1. Location of Augustine Volcano within Cook Inlet.
Note: Augustine Volcano is the most active volcano in the Cook Inlet region of Alaska It erupted at least five times during the 20th century, and began erupting again in December 2005. The activity in early 2006 has included multiple episodes of explosive ash and pyroclastic flow eruptions, as well as lava dome eruptions at the summit of the volcano. The steep summit edifice of Augustine Volcano repeatedly collapsed in giant debris avalanches into the sea around Augustine Island during the last 2000 years.
LANDSLIDE ASSUMPTIONS
Figure 2. Slide velocity, thickness and width as a function of the distance for an eastern Augustine Volcano slide.
Note: The numerical model assumes that a portion of Augustine volcano collapsed into the shallow water of Cook Inlet, and is used to calculate a tsunami generated by the landslide from the volcano collapse. The source of debris is assumed to be the northeast side of the volcano's summit. As the slide travelled into Cook Inlet, it's velocity is assumed to diminish from 50m/s to 10m/s, its thickness along the center of the slide also diminished from 30m to 10m, and the slide width increased from approximately 2.5km to 3.5km. The debris avalanche was simulated as progressive flow of the bottom uplift which imparted motion to the water column.
Figure 3. Tsunami arrival time estimated for the modeled slide from Augustine Volcano.
Note: The finite-difference equations are solved in the spherical system of coordinate with the grid spacing of 1 minute along E-W direction and 0.5 minute along N-S direction. Results of numerical computation show isoline of arrival time to various locations around lower Cook Inlet. Tsunami travel time to Homer, the closest major population center to Augustine Volcano, is close to 75min, while travel time to Anchorage is around 4 hours.
Figure 4. . Maximum tsunami amplitudes in centimeters. Abbreviations: APH, Anchor Point -Homer; SEB Seldovia-English Bay; ILV, Iliamna Volcano.
Note: The strongest amplification occurs along the Seldovia-English Bay shoreline, up to approximately 2.5 m above the mean sea level. Amplification of up to 2 m takes place along Anchor Point-Homer shoreline and along the Iliamna Volcano shoreline on the west side of Cook Inlet. This amplification is especially important for the coastal communities along the eastern shore of Lower Cook Inlet as tsunami travels to the Seldovia and English Bay areas in 50 min and to the Anchor Point and Homer areas in about 75 min, so that warning time for these communities is quite short.
VIDEO/ANIMATION
a) Wave propagation
Note: Wave amplitude reaching Anchorage is very small (less than 20 cm). (Download high resolution version. MOV file size: 75.4MB)
b) Maximum Wave Height
Note: Notice tsunami energy concentration along Anchor Point-Homer and Iliamna Volcano shorelines. Plotting maximum wave height in time is convenient for visualizing the delay of the maximum wave. As it can be seen from the animation, arrival time of maximum wave amplitude in these locations does not correspond to the first wave group. (Download high resolution version. MOV file size: 28.5MB)
Modified 4 October 2007. Website questions or comments to Juan J. Horrillo.