Matthew J. Hornbach Research Associate PhD., The University of Wyoming, 2004 A.B., Hamilton College, 1998 Telephone: (512) 636-5030 FAX: (512) 471-0348 email: matth@utig.ig.utexas.edu

Primary Research Interests:

My research focuses on using high-resolution 2D/3D seismic imaging techniques and geophysical models to link shallow geological structure with sediment stress-states and fluid flow. This research is broadly applicable to an array of current geophysical and cross-disciplinary scientific problems including understanding (1) fluid-pressures, slope-failure, and the structure and evolution of continental margins, (2) methane mobilization and its potential impact on climate, (3) the role of seeps and vents in heat/fluid transport and in sustaining diverse chemosynthetic biological seafloor communities and (4) geohazards, with particular emphasis on tsunami generation/propagation.

Examples of my research:
EXAMPLE #1: 3D Seismic Imaging and Fluid Flow Analysis of the Blake Ridge Gas Hydrate Province:
Gas hydrates are frozen methane and water molecules that form at high pressures and low temperatures. Methane hydrates are generally found in permafrost regions, or beneath continental margins where high pressures and cool bottom water temperatures exist. Although most folks have never seen (or heard) of methane hydrates, this frozen form of methane represents one of the largest reservoirs of methane – a potent greenhouse gas – on Earth. Some studies suggest that the destabilization of methane hydrates and release of methane into the atmosphere may be responsible for some of Earth’s most severe global warming events. Some of the key questions researchers studying methane hydrates are trying to address are:

(1) How much methane hydrate truly exists?
(2) How might methane hydrates destabilize and impact Earth’s climate?
(3) Are methane hydrates unstable, and will destabilization generate additional geohazards, such as slope failure?

Much of my Ph.D work at the University of Wyoming focused on addressing these questions by studying the Blake Ridge Gas Hydrate Province. The Blake Ridge a large sediment drift located off the US eastern seaboard happens to be the location of one of the largest methane hydrate reservoirs on Earth. Below is a link to a movie that shows in 3D the seafloor (blue), the base of the hydrate stability zone signified by a bottom-simulating reflector, or BSR (yellow), and areas thought to consist of concentrated hydrate (red) at the Blake Ridge. The green surfaces mark the location of eroded buried sediment waves—these features appear to control the gas distribution on the ridge (see Holbrook et al., 2002). The colored surfaces in the image were created from the migrated 3D volume by using Paradigm Geophysical Software; the movie file was developed with Matlab. For more information on hydrate concentrations, 3D data results, and fluid pressure analysis, see Hornbach et al., GEOPHYSICS, 2003; Hornbach et al., JGR, 2008, and Hornbach et al, Nature, 2004).

Blake_Ridge_3D_surfaces_movie

EXAMPLE #2: Geophysical Analysis of Fluid Flow and Gas Migration at the Blake Ridge Diapir:
Methane gas also acts as an invaluable source of energy for diverse chemosynthetic communities that survive at the seafloor in the deep ocean. Understanding how these chemosynthetic communities exist requires a detailed understanding of methane fluid-flow. Unfortunately for us, fluid flow at these sites is extremely complex and constantly evolving and accurately modeling the fluid-flow at seeps is a difficult task that requires multiple datasets, and plenty of (ie. read “too many”!) assumptions. One of the projects I worked on was constraining fluid flow at the Blake Ridge Diapir where an active methane seep and evolving chemosynthetic community exists. This study, which involved a fantastic multi-disciplinary group of scientists, made use of the Alvin submersible, 2D and quasi-3D chirp and seismic data, and sediment cores to improved constraints on fluid flow and flow evolution at the site. Below is a 2D pre-stack depth migrated seismic image of sediments above the Blake Ridge Diapir that I created. The strong reflector that cross-cuts strata represent the gas hydrate/free-gas phase boundary, and the vertical “wipe-out” zone in the middle of the section indicates the main region where gas migrates to the seafloor, supplying methane to the chemosynthetic community directly above. We have also a very high-resolution quasi-3D chirp image of the conduit system that reveals dendritic flow paths below the seep. To learn more about this work, see Hornbach et al., GRL, 2005. For a shallow 3D image of the shallow subsurface above the diapir and the fluid conduits that breach the surface and sustain chemosynthetic communities at the seafloor, see Hornbach et al., GRL, 2007.

EXAMPLE #3: Submarine slide and tsunami modeling:
Much of my ongoing research focuses on using seismic data to constrain the shape, volume, and dynamics of submarine landslides, and from this, back-calculate the possible tsunami generated by these events. Tsunamis have long been recognized as one Earth’s most powerful and dangerous geohazards, however, the cause and frequency of tsunamis are often poorly understood. For example, although underwater earthquakes are generally considered the primary cause of tsunamis, evidence continues to mount that submarine slides and flank collapses may be responsible for some of the world’s most devastating tsunamis (For examples, see papers on the Storegga Slide, or Tappin’s work on the 1998 Papua New Guinea tsunami, Ward’s work on Atlantic tsunamis, as well as my own examples below). Much of my tsunami research involves using high resolution seafloor and sub-surface images in conjunction with tsunami models to determine (1) the source of historic tsunamis and (2) the tsunamigenic potential of past (and possibly future) submarine slides.

Below are two movies and a series of tsunami research examples. The links below show a simplified mudflow (3D Gaussian beam) moving down an idealized continental slope, and the resulting tsunami this slide generates (program and images were created in my lab at Texas using Matlab). Besides developing our own numeric tsunami simulations, we’ve integrated our dataset into FUNWAVE and other tsunami models and used these models to estimate tsunamis generated by slope failure events (see Examples 3A, 3B, and 3C). We also are currently building an experimental wave tank to compare numeric and analytic tsunami models and test the accuracy of results. Our wave tank will be fully operational by spring 2009.

idealized_mudslide.mpeg

resulting_tsunami.mpeg

(Example #3A) The Cape Fear Slide. Located a few hundred kilometers east of North Carolina coast, the Cape Fear slide is perhaps the largest submarine slide complex along the US eastern seaboard. Here we present seafloor multibeam images and model results showing the potential tsunami generated if this slide occurred again today. Map view images show wave model results for 5, 15, and 30 min after slide initiation for two different slide events and the change in sea level over time created at hypothetical buoys ‘‘Hatt’’ (for Cape Hatteras) and ‘‘Fear’’ (for Cape Fear) by each tsunami (Figures c and d). As shown in Figures a and c, the sea surface amplitudes generated by the smaller slide are significantly less than those for the larger slide (Figures b and d). These amplitudes may increase as the wave approaches shore, but slower wave speeds over the extensive western Atlantic shelf will promote viscous wave dampening and dispersion. For more information on this research, See Hornbach et al., G-Cubed 2007).

 

(Example #3B) The 1918 Puerto Rico Tsunami. The great 1918 tsunami that inundated northwest Puerto Rico with up to 6 m waves has been attributed to seafloor faulting associated with the 1918 Mona Canyon earthquake. During the earthquake, however, a series of submarine cable breaks occurred directly off the northwest coast of Puerto Rico where the largest tsunami waves came ashore, and these cable breaks were attributed to a possible submarine slide. Here, we use a recently compiled geophysical data set to reveal that a 9 km long landslide headwall exists in the region where cable breaks occurred during the 1918 earthquake. We incorporate our interpretations into a near-field tsunami wave model to evaluate whether the slide may have triggered the observed 1918 tsunami. Our analysis indicates that this slide could generate a tsunami with phase, arrival times, and run-ups similar to observations along the northwest coast of Puerto Rico. We therefore suggest that a submarine slide offers a plausible alternative explanation for generation of this large tsunami. For further information on this event, See Hornbach et al, 2008 and LópezVenegas et al., 2008.

Above: Multibeam and seismic images with interpretation, showing location of possible slide that triggered the 1918 tsunami.

Above: Results of our tsunami wave model, which closely match eye-witness observations.

 

(Example #3C) Huge Erratic Boulders deposited on Tonga by Volcanically-Generated Tsunami
—Images and Models COMING SOON!!

 

Currently Funded Projects:
“Ultra high resolution 3D seismic surveying of active Hydrate Ridge vents to compliment proposed CORKing,” $420,000 granted by NSF-OCE Ocean Drilling Program for a two-year study, starting summer 2008

“Assessing Slope Stability and Tsunami Generation in Caracas Bay, Curacao, The Netherlands Antilles,” $113,000 granted via a private company. Project duration: August 9^th, 2007 – August 8^th, 2009.

 

Students & Postdocs (past/present)

Publications

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