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Richard G. Lahusen

Publications and source records attributed to Richard G. Lahusen.

8 recordsLinked to original sources
USGS2017

Emplacement of a silicic lava dome through a crater glacier: Mount St Helens, 2004-06

The process of lava-dome emplacement through a glacier was observed for the first time after Mount St Helens reawakened in September 2004. The glacier that had grown in the crater since the cataclysmic 1980 eruption was split in two by the new lava dome. The two parts of the glacier were successively squeezed against the crater wall. Photography, photogrammetry and geodetic measurements document glacier deformation of an extreme variety, with strain rates of extraordinary magnitude as compared to normal alpine glaciers. Unlike normal temperate glaciers, the crater glacier shows no evidence of either speed-up at the beginning of the ablation season or diurnal speed fluctuations during the ablation season. Thus there is evidently no slip of the glacier over its bed. The most reasonable explanation for this anomaly is that meltwater penetrating the glacier is captured by a thick layer of coarse rubble at the bed and then enters the volcano's groundwater system rather than flowing through a drainage network along the bed.

Washington↗
USGS2014

Using monitoring and modeling to define the hazard posed by the reactivated Ferguson rock slide, Merced Canyon, California

Rapid onset natural disasters such as large landslides create a need for scientific information about the event, which is vital to ensuring public safety, restoring infrastructure, preventing additional damage, and resuming normal economic activity. At the same time, there is limited data available upon which to base reliable scientific responses. Monitoring movement and modeling runout are mechanisms for gaining vital data and reducing the uncertainty created about a rapid onset natural disaster. We examine the effectiveness of this approach during the 2006 Ferguson rock slide disaster, which severed California Highway 140. Even after construction of a bypass restoring normal access to the community of El Portal, CA and a major entrance to Yosemite National Park, significant scientific questions remained. The most important for the affected public and emergency service agencies was the likelihood that access would again be severed during the impending rainy season and the possibility of a landslide dam blocking flow in the Merced River. Real-time monitoring of the Ferguson rock slide yielded clear information on the continuing movement of the rock slide and its implications for emergency response actions. Similarly, simulation of runout deposits using a physically based model together with volumes and slope steepness information demonstrated the conditions necessary for a landslide dam-forming event and the possible consequences of such an event given the dimensions of potential rock slide deposits.

California↗
USGS2009

Volcano monitoring

Volcanoes are not randomly distributed over the Earth's surface. Most are concentrated on the edges of continents, along island chains, or beneath the sea where they form long mountain ranges. More than half of the world's active volcanoes above sea level encircle the Pacific Ocean (see Fig. 1 ). The concept of plate tectonics explains the locations of volcanoes and their relationship to other large-scale geologic features. The Earth's surface is made up of a patchwork of about a dozen large plates and a number of smaller ones that move relative to one another at <1 cm to ~10 cm/yr (about the speed at which fingernails grow). These rigid plates, with average thickness of ~80 km, are separating, sliding past each other, or colliding on top of the Earth's hot, viscous interior. Volcanoes tend to form where plates collide or spread apart ( Fig. 2 ) but can also grow in the middle of a plate, like the Hawaiian volcanoes ( Fig. 3 ). Of the more than 1,500 volcanoes worldwide believed to have been active in the past 10,000 years, 169 are in the United States and its territories ( Ewert et al., 2005 ) (see Fig. 4 ). As of spring 2007, two of these volcanoes, Kilauea and Mount St. Helens, are erupting, while several others, including Mauna Loa, Fourpeaked, Korovin, Veniaminof, and Anatahan, exhibit one or more signs of restlessness, such as anomalous earthquakes, deformation of the volcano's surface, or changes in volume and composition.

Book chapter↗
USGS2006

Applications of geophysical methods to volcano monitoring

The array of geophysical technologies used in volcano hazards studies - some developed originally only for volcano monitoring - ranges from satellite remote sensing including InSAR to leveling and EDM surveys, campaign and telemetered GPS networks, electronic tiltmeters and strainmeters, airborne magnetic and electromagnetic surveys, short-period and broadband seismic monitoring, even microphones tuned for infrasound. They include virtually every method used in resource exploration except large-scale seismic reflection. By “geophysical ” we include both active and passive methods as well as geodetic technologies. Volcano monitoring incorporates telemetry to handle high-bandwith cameras and broadband seismometers. Critical geophysical targets include the flux of magma in shallow reservoir and lava-tube systems, changes in active hydrothermal systems, volcanic edifice stability, and lahars. Since the eruption of Mount St. Helens in Washington State in 1980, and the eruption at Pu’u O’o in Hawai’i beginning in 1983 and still continuing, dramatic advances have occurred in monitoring technology such as “crisis GIS” and lahar modeling, InSAR interferograms, as well as gas emission geochemistry sampling, and hazards mapping and eruption predictions. The on-going eruption of Mount St. Helens has led to new monitoring technologies, including advances in broadband Wi-Fi and satellite telemetry as well as new instrumentation. Assessment of the gap between adequate monitoring and threat at the 169 potentially dangerous Holocene volcanoes shows where populations are dangerously exposed to volcanic catastrophes in the United States and its territories . This paper focuses primarily on Hawai’ian volcanoes and the northern Pacific and Cascades volcanoes. The US Geological Survey, the US National Park System, and the University of Utah cooperate in a program to monitor the huge Yellowstone volcanic system, and a separate observatory monitors the restive Long Valley caldera in collaboration with the US Forest Service.

Conference Paper↗
USGS1997

Debris-flow mobilization from landslides

Field observations, laboratory experiments, and theoretical analyses indicate that landslides mobilize to form debris flows by three processes: ( a ) widespread Coulomb failure within a sloping soil, rock, or sediment mass, ( b ) partial or complete liquefaction of the mass by high pore-fluid pressures, and ( c ) conversion of landslide translational energy to internal vibrational energy (i.e. granular temperature). These processes can operate independently, but in many circumstances they appear to operate simultaneously and synergistically. Early work on debris-flow mobilization described a similar interplay of processes but relied on mechanical models in which debris behavior was assumed to be fixed and governed by a Bingham or Bagnold rheology. In contrast, this review emphasizes models in which debris behavior evolves in response to changing pore pressures and granular temperatures. One-dimensional infinite-slope models provide insight by quantifying how pore pressures and granular temperatures can influence the transition from Coulomb failure to liquefaction. Analyses of multidimensional experiments reveal complications ignored in one-dimensional models and demonstrate that debris-flow mobilization may occur by at least two distinct modes in the field.

Annual Review of Earth and Planetary Sciences↗
USGS1989

Dynamic pore-pressure fluctuations in rapidly shearing granular materials

Results from two types of experiments show that intergranular pore pressures fluctuated dynamically during rapid, steady shear deformation of water-saturated granular materials. During some fluctuations, the pore water locally supported all normal and shear stresses, while grain-contact stresses transiently fell to zero. Fluctuations also propagated outward from the shear zone; this process modifies grain-contact stresses in adjacent areas and potentially instigates shear-zone growth.

Science↗