Hermann M. Fritz

Sri Lanka Field Survey after the December 2004 Indian Ocean Tsunami

In August 2005, a team surveyed the effects of the December 2004 Indian Ocean tsunami on the southern coast of Oman. Runup and inundation were obtained at 41 sites, extending over a total of 750 km of shoreline. Measured runup ranged from 3.25 m in the vicinity of Salalah to a negligible value at one location on Masirah Island. In general, the largest values were found in the western part of the surveyed area. Significant incidents were documented in the port of Salalah, where a 285-m-long vessel broke its moorings and drifted inside and outside the port, and another ship struck the breakwater while attempting to enter the harbor. The general hazard to Oman from tsunamis may be greatest from the neighboring Makran subduction zone in western Pakistan.

The 2010 Mw 7.8 Mentawai earthquake: Very shallow source of a rare tsunami earthquake determined from tsunami field survey and near-field GPS data

[1] The Mw 7.8 October 2010Mentawai, Indonesia, earthquake was a“tsunami earthquake,” a rare type of earthquake that generates a tsunami much larger than expected based on the seismicmagnitude.Itproducedalocallydevastatingtsunami,withrunupcommonlyinexcess of 6 m. We examine this event using a combination of high-rate GPS data, from instruments located on the nearby islands, and a tsunami field survey. The GPS displacement time series are deficient in high-frequency energy, and show small coseismic displacements ( 16 m. Our modeling results show that the combination of the small GPS displacements and large tsunami can only be explained by high fault slip at very shallow depths, far from the islands and close to the oceanic trench. Inelastic uplift of trench sediments likely contributed to the size of the tsunami. Recent results for the 2011 Mw 9.0 Tohoko-Oki earthquake have also shown shallow fault slip, but the results from our study, which involves a smaller earthquake, provide much stronger constraints on how shallow the rupture can be, with the majority of slip for the Mentawai earthquake occurring at depths of <6 km. This result challenges the conventional wisdom that the shallow tips of subduction megathrusts are aseismic, and therefore raises important questions both about the mechanical properties of the shallow fault zone and the potential seismic and tsunami hazard of this shallow region.

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.

PROPAGATION AND INUNDATION CHARACTERISTICS OF THE 2011 TOHOKU TSUNAMI ON THE CENTRAL SANRIKU COAST

Propagation and inundation characteristics of the 2011 Tohoku tsunami on the central Sanriku coast are investigated through field surveys and numerical simulations using offshore wave recordings as incident wave conditions. The numerical model successfully reproduces the extent of flood areas as well as the distribution of tsunami heights along the intricate coastline except for run-up of extreme heights over steep slopes. The survey and computed results suggest significant variations of tsunami heights along the coastline. Their positive dependency on topographic slopes implies that the incoming tsunami propagates in standing wave mode to precipitous sites while in progressive wave mode accompanied by wave breaking over gentle slopes. Temporal-spatial analysis of wave properties in different bays reveals that the inner bay topography provides a clear contrast to inundation characteristics. The impacting waves have extreme heights due to the funnel effect and local wave resonances causing highly transient flooding in narrow V-shaped bays whereas tsunami surges over longer periods across innermost shores of U-shaped bays to produce large horizontal velocities during both run-up and backwash phases.

Hurricane Disaster Assessments With Image-Driven Data Mining in High-Resolution Satellite Imagery

Detection, classification, and attribution of high-resolution satellite image features in nearshore areas in the aftermath of Hurricane Katrina in Gulfport, MS, are investigated for damage assessments and emergency response planning. A system-level approach based on image-driven data mining with sigma-tree structures is demonstrated and evaluated. Results show a capability to detect hurricane debris fields and storm-impacted nearshore features (such as wind-damaged buildings, sand deposits, standing water, etc.) and an ability to detect and classify nonimpacted features (such as buildings, vegetation, roadways, railways, etc.). The sigma-tree-based image information mining capability is demonstrated to be useful in disaster response planning by detecting blocked access routes and autonomously discovering candidate rescue/recovery staging areas

Madagascar Field Survey after the December 2004 Indian Ocean Tsunami

The effects of the 26 December 2004 Indian Ocean tsunami on the island of Madagascar were surveyed in July and August of 2005. Runup and inundation were obtained at 52 sites, covering most of the eastern coast of the country, ranging from a maximum runup of 5.4 m in the south to locations where the tsunami was not observed by eyewitnesses present on the day of the event. The data set is characterized by significant heterogeneity, suggesting the importance of local factors in controlling runup. The report of a 50-m vessel breaking its moorings in the port of Toamasina several hours after the maximum visible activity of the wave underscores the complexity of harbor responses and the need to re-evaluate civil defense policies in port environments. Important factors are how the Malagasy population responded to the warning issued during the Nias earthquake, on 28 March 2005, and the hazard posed to Madagascar by possible future mega-earthquakes in south Sumatra.

Assessment of Energy Production Potential from Tidal Streams in the United States

Tidal stream energy is one of the alternative energy sources that are renewable and clean. With the constantly increasing effort in promoting alternative energy, tidal streams have become one of the more promising energy sources due to their continuous, predictable and spatially-concentrated characteristics. However, the present lack of a full spatial-temporal assessment of tidal currents for the U.S. coastline down to the scale of individual devices is a barrier to the comprehensive development of tidal current energy technology. This project created a national database of tidal stream energy potential, as well as a GIS tool usable by industry in order to accelerate the market for tidal energy conversion technology. Tidal currents are numerically modeled with the Regional Ocean Modeling System and calibrated with the available measurements of tidal current speed and water level surface. The performance of the model in predicting the tidal currents and water levels is assessed with an independent validation. The geodatabase is published at a public domain via a spatial database engine and interactive tools to select, query and download the data are provided. Regions with the maximum of the average kinetic power density larger than 500 W/m2 (corresponding to a current speed of ~1 m/s), surface area larger than 0.5 km2 and depth larger than 5 m are defined as hotspots and list of hotspots along the USA coast is documented. The results of the regional assessment show that the state of Alaska (AK) contains the largest number of locations with considerably high kinetic power density, and is followed by, Maine (ME), Washington (WA), Oregon (OR), California (CA), New Hampshire (NH), Massachusetts (MA), New York (NY), New Jersey (NJ), North and South Carolina (NC, SC), Georgia (GA), and Florida (FL). The average tidal stream power density at some of these locations can be larger than 8 kW/m2 with surface areas on the order of few hundred kilometers squared, and depths larger than 100 meters. The Cook Inlet in AK is found to have a substantially large tidal stream power density sustained over a very large area.

Repeat Storm Surge Disasters of Typhoon Haiyan and Its 1897 Predecessor in the Philippines

AbstractOn 8 November 2013, Typhoon Haiyan impacted the Philippines with estimated winds of approximately 314 km h-1 and an associated 5–7-m-high storm surge that struck Tacloban City and the surrounding coast of the shallow, funnel-shaped San Pedro Bay. Typhoon Haiyan killed more than 6,000 people, superseding Tropical Storm Thelma of November 1991 as the deadliest typhoon in the Philippines. Globally, it was the deadliest tropical cyclone since Nargis hit Myanmar in 2008. Here, we use field measurements, eyewitness accounts, and video recordings to corroborate numerical simulations and to characterize the extremely high velocity flooding caused by the Typhoon Haiyan storm surge in both San Pedro Bay and on the more open Pacific Ocean coast. We then compare the surge heights from Typhoon Haiyan with historical records of an unnamed typhoon that took a similar path of destruction in October 1897 (Ty 1897) but which was less intense, smaller, and moved more slowly. The Haiyan surge was about twice the heig...

PIV applied to landslide generated impulse waves

Large scale digital particle image velocimetry (PIV) and laser speckle velocimetry (LSV) are applied to landslide generated impulse waves. The challenges posed to the measurement techniques in an extremely unsteady three phase flow consisting of granular matter, air and water are considered. Areas of interest up to 0.8 m by 0.8 m are investigated in the impulse wave generation zone. The complex flow phenomena present in the first stage of impulse wave initiation are: High speed granular slide impact, impulse flux transfer, flow separation and reattachement, cavity formation and collapse, slide deformation and penetration into fluid. During this first stage the three phases are separated along sharp interfaces changing significantly within time and space. A combined analysis method for PIV in water flow and LSV on the corona of the landslide surface is presented. Digital masking techniques are applied to distinguish between phases thereafter allowing phase separated image processing. The combination of PIV and LSV reveals insight into the impulse transfer mechanism. Applicability of PIV at large scale as well as to flows with large velocity gradients due to the presence of a strong shock are highlighted.

Pneumatic Landslide Generator

Abstract A pneumatic landslide generator was developed specifically for the investigation of landslide generated impulse waves in reservoirs, lakes, bays or oceans in a two-dimensional physical laboratory model. The landslides were successfully modelled with an artificial granulate. The pneumatic landslide generator was designed to control the slide impact characteristics and enable exact reproduction and independent variation of single dynamic slide parameters. The two pneumatic linear drives catapulted the landslides to velocities up to 7.3 m/s on an acceleration distance of less than 0.9 m. The operation of linear drives 3.6 times beyond their certified velocity range is highlighted. Total masses of up to 174 kg were accelerated. The slotted cylinders enabled a compact mechanical design and a stroke length equal to 70 % of the overall cylinder length. The pneumatic deceleration by temporary airflow and pressure gradient reversal is presented. Real time valve response problems in high-speed applications are discussed and solved with preset trigger signals programmed to the pneumatics control unit. The behaviour of the whole pneumatic system was successfully simulated with the computer aided cylinder optimisation system software (CACOS). The measurements and numerical simulations are compared.