Robert Weiss

Hybrid modeling of the mega-tsunami runup in Lituya Bay after half a century

The largest mega-tsunami dates back half a century to 10 July 1958, when almost unnoticed by the general public, an earthquake of M w 8.3 at the Fairweather Fault triggered a rockslide into Lituya Bay. The rockslide impact generated a giant tsunami at the head of Lituya Bay resulting in an unprecedented tsunami runup of 524 m on a spur ridge in direct prolongation of the slide axis. A forest trim line and erosion down to bedrock mark the largest runup in recorded history. While these observations have not been challenged directly, they have been largely ignored in hazard mitigation studies, because of the difficulties of even posing ― much less solving - a well-defined physical problem for investigation. We study the mega-tsunami runup with a hybrid modeling approach applying physical and numerical models of slide processes of deformable bodies into a U-shaped trench similar to the geometry found at Lituya Bay. C.

Slip Distribution of the 1952 Kamchatka Great Earthquake Based on Near-Field Tsunami Deposits and Historical Records

We explore the magnitude and slip distribution of the 1952 Kamchatka earthquake (Mw 8.8-9.0) using constraints from the 1952 Kamchatka tsunami. Our new field data provide more comprehensive coverage of the near-field tsunami than had been available to date. We examine the effects of internal slip distribution within complex earthquake ruptures on near-field tsunami runup and evaluate some of the limitations of this approach. Our approach compares tsunami-deposit distribution with simulated runup from tsunamis generated by different configurations of seafloor deformation from hypothetical earthquakes resembling that of the 1952 Kamchatka earthquake. We identify areas of high slip because different distributions of seafloor deformation result in variations in tsunami runup in the near field. Mapped deposits and local observations of the 1952 Kamchatka tsunami indicate that near-field runup in central Kamchatka was consistently less than 10 m (averaging 6 m), while south Kamchatka to the northern Kuril Islands had more variability and higher average runup (8 m runup in South Kamchatka and 10 m runup in the northern Kuril Islands). Our simulations show that in order to produce the distribution of runup indicated by tsunami deposits and historical observations, the 1952 earthquake had regions of high slip off the coast of southern Kamchatka, and the location of high slip is shallower in the subduction zone than previously interpreted. Online Material: Sedimentary methodology, model inputs, and simulation results.

“Chevrons” are not mega-tsunami deposits—A sedimentologic assessment

Since the introduction of the term “chevron” for large v- or u-shaped bed forms in Egypt and the Bahamas, others have adopted the term to describe large-scale coastal bed forms in Australia, Madagascar, and elsewhere. These authors interpret “chevron” bed forms as deposits of mega-tsunamis resulting from Holocene oceanic asteroid impacts. We reason that chevron-type bed forms are common and are present far enough from the coast to preclude tsunami genesis. Moreover, we argue that “chevrons” are not mega-tsunami deposits by modeling tsunami behavior and evaluating sediment-transport conditions under which such features formed. We model the southern Madagascar case, with an impact source in the Indian Ocean, and show that a modeled wave approach is inconsistent with “chevron” orientation. We then evaluate sediment-transport conditions under which these “chevron” bed forms could persist, i.e., bed-load transport. In our analysis, no conditions specified generate pure bed-load transport, and most result in pure suspended-load transport.

Temporal and Spatial Evolution of Potential Energy, Kinetic Energy, and Momentum Flux in Tsunami Waves during Breaking and Inundation

AbstractA plethora of studies in the last decade described tsunami hazards and studied their evolution from the source to the target coastline but mainly focused on coastal inundation and maximum r...

Observations and Modeling of the 27 February 2010 Tsunami in Chile

Chile; Coastal bluffs; Coastal uplift; Loss of life; Pacific islands; Regional scale; Survey data; Tsunami flow; Disasters; Earthquakes; Surveys; Tsunamis

A Case Study on Landslide-Generated Tsunami and Its Impact on the U.S. Atlantic Coast

Recent studies suggested that the potential eruption of Cumbre Vieja Valcano on La Palma Island may cause catastrophic failure of the west flank and generate a tsunami that threats the American coasts (e.g. Ward and Day, 2001; Lovholt et al., 2008). In the present study, we revisit this problem with a credible worst case scenario and advanced numerical approaches.Copyright