Evelyn Roeloffs
Evelyn Roeloffs is a Scientist Emeritus in the Earthquake Hazards Program.
Science and Products
Filter Total Items: 21
Widespread groundwater-level offsets caused by the Mw 5.8 Mineral, Virginia, earthquake of 23 August 2011
Groundwater levels were offset in bedrock observation wells, measured by the U.S. Geological Survey or others, as far as 553 km from the Mw 5.8 Mineral, Virginia (USA), earthquake on 23 August 2011. Water levels dropped as much as 0.47 m in 34 wells and rose as much as 0.15 m in 12 others. In some wells, which are as much as 213 m deep, the water levels recovered from these deviations in...
Authors
Evelyn A. Roeloffs, David L. Nelms, Rodney A. Sheets
Earthquake forewarning in the Cascadia region
This report, prepared for the National Earthquake Prediction Evaluation Council (NEPEC), is intended as a step toward improving communications about earthquake hazards between information providers and users who coordinate emergency-response activities in the Cascadia region of the Pacific Northwest. NEPEC charged a subcommittee of scientists with writing this report about forewarnings...
Authors
Joan S. Gomberg, Brian F. Atwater, Nicholas M. Beeler, Paul Bodin, Earl Davis, Arthur Frankel, Gavin P. Hayes, Laura McConnell, Tim Melbourne, David H. Oppenheimer, John G. Parrish, Evelyn A. Roeloffs, Gary D. Rogers, Brian Sherrod, John Vidale, Timothy J. Walsh, Craig S. Weaver, Paul M. Whitmore
Re‐estimated effects of deep episodic slip on the occurrence and probability of great earthquakes in Cascadia
Mazzotti and Adams (2004) estimated that rapid deep slip during typically two week long episodes beneath northern Washington and southern British Columbia increases the probability of a great Cascadia earthquake by 30–100 times relative to the probability during the ∼58 weeks between slip events. Because the corresponding absolute probability remains very low at ∼0.03% per week, their...
Authors
Nicholas M. Beeler, Evelyn A. Roeloffs, Wendy McCausland
Working with strainmeter data
The Plate Boundary Observatory (PBO), the geodetic component of the U.S. National Science Foundation–funded Earthscope program, includes 75 borehole and 6 laser strainmeters (http://pbo.unavco.org). The strainmeters are installed at several locations: on the Cascadia forearc in Washington state and on Vancouver Island, Canada; in arrays of two to nine instruments along the North American...
Authors
Kathleen M. Hodgkinson, Duncan Agnew, Evelyn A. Roeloffs
Tidal calibration of Plate Boundary Observatory borehole strainmeters: Roles of vertical and shear coupling
A multicomponent borehole strainmeter directly measures changes in the diameter of its cylindrical housing at several azimuths. To transform these measurements to formation strains requires a calibration matrix, which must be estimated by analyzing the installed strainmeter's response to known strains. Typically, theoretical calculations of Earth tidal strains serve as the known strains...
Authors
Evelyn Roeloffs
Improved constraints on the estimated size and volatile content of the Mount St. Helens magma system from the 2004–2008 history of dome growth and deformation
The history of dome growth and geodetic deflation during the 2004–2008 Mount St. Helens eruption can be fit to theoretical curves with parameters such as reservoir volume, bubble content, initial overpressure, and magma rheology, here assumed to be Newtonian viscous, with or without a solid plug in the conduit center. Data from 2004–2008 are consistent with eruption from a 10–25 km3...
Authors
Larry G. Mastin, Mike Lisowski, Evelyn Roeloffs, Nick Beeler
Science and Products
Filter Total Items: 21
Widespread groundwater-level offsets caused by the Mw 5.8 Mineral, Virginia, earthquake of 23 August 2011
Groundwater levels were offset in bedrock observation wells, measured by the U.S. Geological Survey or others, as far as 553 km from the Mw 5.8 Mineral, Virginia (USA), earthquake on 23 August 2011. Water levels dropped as much as 0.47 m in 34 wells and rose as much as 0.15 m in 12 others. In some wells, which are as much as 213 m deep, the water levels recovered from these deviations in...
Authors
Evelyn A. Roeloffs, David L. Nelms, Rodney A. Sheets
Earthquake forewarning in the Cascadia region
This report, prepared for the National Earthquake Prediction Evaluation Council (NEPEC), is intended as a step toward improving communications about earthquake hazards between information providers and users who coordinate emergency-response activities in the Cascadia region of the Pacific Northwest. NEPEC charged a subcommittee of scientists with writing this report about forewarnings...
Authors
Joan S. Gomberg, Brian F. Atwater, Nicholas M. Beeler, Paul Bodin, Earl Davis, Arthur Frankel, Gavin P. Hayes, Laura McConnell, Tim Melbourne, David H. Oppenheimer, John G. Parrish, Evelyn A. Roeloffs, Gary D. Rogers, Brian Sherrod, John Vidale, Timothy J. Walsh, Craig S. Weaver, Paul M. Whitmore
Re‐estimated effects of deep episodic slip on the occurrence and probability of great earthquakes in Cascadia
Mazzotti and Adams (2004) estimated that rapid deep slip during typically two week long episodes beneath northern Washington and southern British Columbia increases the probability of a great Cascadia earthquake by 30–100 times relative to the probability during the ∼58 weeks between slip events. Because the corresponding absolute probability remains very low at ∼0.03% per week, their...
Authors
Nicholas M. Beeler, Evelyn A. Roeloffs, Wendy McCausland
Working with strainmeter data
The Plate Boundary Observatory (PBO), the geodetic component of the U.S. National Science Foundation–funded Earthscope program, includes 75 borehole and 6 laser strainmeters (http://pbo.unavco.org). The strainmeters are installed at several locations: on the Cascadia forearc in Washington state and on Vancouver Island, Canada; in arrays of two to nine instruments along the North American...
Authors
Kathleen M. Hodgkinson, Duncan Agnew, Evelyn A. Roeloffs
Tidal calibration of Plate Boundary Observatory borehole strainmeters: Roles of vertical and shear coupling
A multicomponent borehole strainmeter directly measures changes in the diameter of its cylindrical housing at several azimuths. To transform these measurements to formation strains requires a calibration matrix, which must be estimated by analyzing the installed strainmeter's response to known strains. Typically, theoretical calculations of Earth tidal strains serve as the known strains...
Authors
Evelyn Roeloffs
Improved constraints on the estimated size and volatile content of the Mount St. Helens magma system from the 2004–2008 history of dome growth and deformation
The history of dome growth and geodetic deflation during the 2004–2008 Mount St. Helens eruption can be fit to theoretical curves with parameters such as reservoir volume, bubble content, initial overpressure, and magma rheology, here assumed to be Newtonian viscous, with or without a solid plug in the conduit center. Data from 2004–2008 are consistent with eruption from a 10–25 km3...
Authors
Larry G. Mastin, Mike Lisowski, Evelyn Roeloffs, Nick Beeler