Rob Witter, Ph.D.
I conduct geological detective work that uncovers clues about the location, size, and frequency of ancient earthquakes and tsunamis. If we prepare for these hazards we can prevent future earthquakes and tsunamis from becoming future disasters.
I study prehistoric earthquakes along the Pacific-North American plate boundary. I apply aspects of geomorphology, paleoseismology, geodesy, and sea-level studies to decipher the geologic record of ancient earthquakes. Most of my work focuses on great subduction earthquakes capable of generating tsunamis. What I find out contributes to seismic and tsunami hazards assessments used to strengthen building codes and reduce tsunami risk.
Professional Experience
2011 – Present Research Geologist, U.S. Geological Survey, Alaska Science Center, Anchorage, AK
2006 – 2011 Regional Coastal Geologist, Oregon Department of Geology and Mineral Industries, Newport, OR
1999 – 2006 Senior Project Geologist, William Lettis & Associates, Inc., Walnut Creek, CA
Education and Certifications
Ph.D. 1999 University of Oregon, Eugene, OR Geoscience
B.A. 1991 Whitman College, Walla Walla, WA Biology
Science and Products
Filter Total Items: 18
No Result Found
Filter Total Items: 26
No results found.
Filter Total Items: 55
The sedimentary record of the 2018 Anchorage Earthquake in Eklutna Lake, Alaska: Calibrating the lacustrine seismograph The sedimentary record of the 2018 Anchorage Earthquake in Eklutna Lake, Alaska: Calibrating the lacustrine seismograph
The 30 November 2018 Mw 7.1 Anchorage earthquake caused modified Mercalli intensities of V¼ to V½ at Eklutna Lake (south central Alaska). A few hours after the earthquake, a “dirt streak” was observed on the lake surface, followed by a peak in sediment turbidity values (∼80 times normal) at a drinking water facility, which receives water from the lake through a pipe. These observations...
Authors
Maarten Van Daele, Peter J. Haeussler, Robert C. Witter, Nore Praet, Marc De Batist
Ground failure from the Anchorage, Alaska, earthquake of 30 November 2018 Ground failure from the Anchorage, Alaska, earthquake of 30 November 2018
Investigation of ground failure triggered by the 2018 MwMw 7.1 Anchorage earthquake showed that landslides, liquefaction, and ground cracking all occurred and caused significant damage. Shallow rock falls and rock slides were the most abundant types of landslides, but they occurred in smaller numbers than global models that are based on earthquake magnitude predict; this might result...
Authors
Randall Jibson, Alex Grant, Robert C. Witter, Kate Allstadt, Eric Thompson, Adrian Bender
The 30 November 2018 Mw7.1 Anchorage Earthquake The 30 November 2018 Mw7.1 Anchorage Earthquake
The Mw 7.1 47 km deep earthquake that occurred on 30 November 2018 had deep societal impacts across southcentral Alaska and exhibited phenomena of broad scientific interest. We document observations that point to future directions of research and hazard mitigation. The rupture mechanism, aftershocks, and deformation of the mainshock are consistent with extension inside the Pacific plate...
Authors
Michael West, Adrian Bender, Matthew Gardine, Lea Gardine, Kara Gately, Peter J. Haeussler, Wael Hassan, Franz Meyer, Cole Richards, Natalia Ruppert, Carl Tape, John Thornley, Robert Witter
Evidence for frequent, large tsunamis spanning locked and creeping parts of the Aleutian megathrust Evidence for frequent, large tsunamis spanning locked and creeping parts of the Aleutian megathrust
At the eastern end of the 1957 Andreanof Islands magnitude-8.6 earthquake rupture, Driftwood Bay (Umnak Island) and Stardust Bay (Sedanka Island) lie along presently locked and creeping parts of the Aleutian megathrust, respectively, based on satellite geodesy onshore. Both bays, located 200-km apart, face the Aleutian trench and harbor coastal evidence for tsunami inundation in 1957...
Authors
Robert C. Witter, Richard Briggs, Simon Engelhart, Guy Gelfenbaum, Richard Koehler, Alan Nelson, SeanPaul La Selle, Reide Corbett, Kristi Wallace
Wetland stratigraphic evidence for variable megathrust earthquake rupture modes at the Cascadia subduction zone Wetland stratigraphic evidence for variable megathrust earthquake rupture modes at the Cascadia subduction zone
Although widespread agreement that the Cascadia subduction zone produces great earthquakes of magnitude 8 to 9 was reached decades ago, debate continues about the rupture lengths, magnitudes, and frequency of megathrust earthquakes recorded by wetland stratigraphy fringing Cascadia’s estuaries. Correlation of such coastal earthquake evidence along the subduction zone has largely relied...
Authors
Alan Nelson, Robert C. Witter, Simon Englehart, Andrea Hawkers, Benjamin Horton
New constraints on coseismic slip during southern Cascadia subduction zone earthquakes over the past 4600 years implied by tsunami deposits and marine turbidites New constraints on coseismic slip during southern Cascadia subduction zone earthquakes over the past 4600 years implied by tsunami deposits and marine turbidites
Forecasting earthquake and tsunami hazards along the southern Cascadia subduction zone is complicated by uncertainties in the amount of megathrust fault slip during past ruptures. Here, we estimate slip on hypothetical ruptures of the southern part of the megathrust through comparisons of late Holocene Cascadia earthquake histories derived from tsunami deposits on land and marine...
Authors
George Priest, Robert C. Witter, Yinglong Zhang, Chris Goldfinger, Kelin Wang, Jonathan Allan
Microfossil measures of rapid sea-level rise: Timing of response of two microfossil groups to a sudden tidal-flooding experiment in Cascadia Microfossil measures of rapid sea-level rise: Timing of response of two microfossil groups to a sudden tidal-flooding experiment in Cascadia
Comparisons of pre-earthquake and post-earthquake microfossils in tidal sequences are accurate means to measure coastal subsidence during past subduction earthquakes, but the amount of subsidence is uncertain, because the response times of fossil taxa to coseismic relative sea-level (RSL) rise are unknown. We measured the response of diatoms and foraminifera to restoration of a salt...
Authors
B. Horton, Yvonne Milker, T. Dura, Kelin Wang, W.T. Bridgeland, Laura Brophy, M. Ewald, Nicole Khan, S.E. Engelhart, Alan Nelson, Robert C. Witter
Sculpted by water, elevated by earthquakes—The coastal landscape of Glacier Bay National Park, Alaska Sculpted by water, elevated by earthquakes—The coastal landscape of Glacier Bay National Park, Alaska
Within Glacier Bay National Park in southeastern Alaska, the Fairweather Fault represents the onshore boundary between two of Earth’s constantly moving tectonic plates: the North American Plate and the Yakutat microplate. Satellite measurements indicate that during the past few decades the Yakutat microplate has moved northwest at a rate of nearly 5 centimeters per year relative to the...
Authors
Robert C. Witter, Adam LeWinter, Adrian Bender, Craig Glennie, David Finnegan
Evidence for shallow megathrust slip across the Unalaska seismic gap during the great 1957 Andreanof Islands earthquake, eastern Aleutian Islands, Alaska Evidence for shallow megathrust slip across the Unalaska seismic gap during the great 1957 Andreanof Islands earthquake, eastern Aleutian Islands, Alaska
We reassess the slip distribution of the 1957 Andreanof Islands earthquake in the eastern part of the aftershock zone where published slip models infer little or no slip. Eyewitness reports, tide gauge data, and geological evidence for 9–23 m tsunami runups imply seafloor deformation offshore Unalaska Island in 1957, in contrast with previous studies that labeled the area a seismic gap...
Authors
D. J. Nicolsky, J.T. Freymueller, Robert C. Witter, E. Suleimani, R.D. Koehler
Differences in coastal subsidence in southern Oregon (USA) during at least six prehistoric megathrust earthquakes Differences in coastal subsidence in southern Oregon (USA) during at least six prehistoric megathrust earthquakes
Stratigraphic, sedimentologic (including CT 3D X-ray tomography scans), foraminiferal, and radiocarbon analyses show that at least six of seven abrupt peat-to-mud contacts in cores from a tidal marsh at Talbot Creek (South Slough, Coos Bay), record sudden subsidence (relative sea-level rise) during great megathrust earthquakes at the Cascadia subduction zone. Data for one contact are...
Authors
Yvonne Milker, Alan Nelson, Benjamin Horton, Simon Engelhart, Lee-Ann Bradley, Robert C. Witter
Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust
Current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust. Here we report geological evidence for large tsunamis, occurring on average every 300–340 years, near the source areas of the 1946 and 1957 Aleutian tsunamis. These areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate...
Authors
Robert C. Witter, G. Carver, Richard Briggs, Guy Gelfenbaum, R.D. Koehler, SeanPaul M. La Selle, Adrian Bender, S.E. Engelhart, E. Hemphill-Haley, Troy Hill
Variability of intertidal foraminferal assemblages in a salt marsh, Oregon, USA Variability of intertidal foraminferal assemblages in a salt marsh, Oregon, USA
We studied 18 sampling stations along a transect to investigate the similarity between live (rose Bengal stained) foraminiferal populations and dead assemblages, their small-scale spatial variations and the distribution of infaunal foraminifera in a salt marsh (Toms Creek marsh) at the upper end of the South Slough arm of the Coos Bay estuary, Oregon, USA. We aimed to test to what extent
Authors
Yvonne Milker, Benjamin Horton, Alan Nelson, Simon Engelhart, Robert C. Witter
Non-USGS Publications**
Engelhart, S. E., Horton, B. P., Nelson, A. R., Hawkes, A. D., Witter, R. C., Wang, K., Wang P.-L., and Vane, C. H., 2013, Testing the use of microfossils to reconstruct great earthquakes at Cascadia, Geology, doi:10.1130/G34544.1.
Engelhart, S. E., B. P. Horton, C. H. Vane, A. R. Nelson, R. C. Witter, S. R. Brody, and A. D. Hawkes, 2013, Modern foraminifera, δ13C, and bulk geochemistry of central Oregon tidal marshes and their application in paleoseismology, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2013.02.032.
Kelson, K., R. C. Witter, A. Tassara, I. Ryder, C. Ledezma, G. Montalva, D. Frost, N. Sitar, R. Moss, and L. Johnson, 2012, Coseismic tectonic surface deformation during the 2012 Maule, Chile, Mw 8.8 earthquake, Earthquake Spectra, v. 28, n. S1, p. 39-54.
Pilarczyk, J. E., Horton, B. P., Witter, R. C., Vane, C. H., Chagué-Goff, C., Goff, J., 2012, Sedimentary and foraminiferal evidence of the 2011 Tohoku-oki tsunami on the Sendai coastal plain, Japan. Sedimentary Geology. doi:10.1016/j.sedgeo.2012.08.011.
Richmond, B., W. Szczucinski, C.Chague-Goff, K. Goto, D. Sugawara, R. Witter, D.R. Tappin, B. Jaffe, S. Fujino, Y. Nishimura, and J. Goff, 2012, Erosion, deposition and landscape change on the Sendai coastal plain, Japan, resulting from the March 11, 2011 Tohoku-oki tsunami, Sedimentary Geology, doi:10.1016/j.sedgeo.2012.08.005.
Witter, R.C., Y.J. Zhang, K. Wang, C. Goldfinger, and G.R. Priest, 2012, Coseismic slip on the southern Cascadia megathrust implied by tsunami deposits in an Oregon lake and earthquake-triggered marine turbidites, Journal of Geophysical Research, 117, B10303, doi:10.1029/2012JB009404.
Allan, J., P. Komar, P. Ruggiero, and R.C. Witter, 2012, The March 2011 Tohoku tsunami and its impacts along the U.S. West Coast, Journal of Coastal Research, Journal of Coastal Research, v. 28, n. 5, p. 1142-1153, doi:10.2112/jcoastres-d-11-00115.1.
Witter, R. C., B. Jaffe, Y. Zhang, and G. R. Priest, 2012, Reconstructing Hydrodynamic Flow Parameters of the 1700 Tsunami at Cannon Beach, Oregon, USA, Natural Hazards, doi:10.1007/s11069-011-9912-7.
Horton, B. P., Sawai, Y., Hawkes, A. D., and Witter, R. C., 2011, Sedimentology and paleontology of a tsunami deposit accompanying the great Chilean earthquake of February 2010: Marine Micropaleontology, v. 79, no. 3-4, p. 132–138, doi:10.1016/j.marmicro.2011.02.001
Zhang, Y. J., R. C. Witter, and G. R. Priest, 2011, Tsunami-tide interaction in 1964 Prince William Sound tsunami, Ocean Modelling, v. 40, p. 246–259, doi:10.1016/j.ocemod.2011.09.005
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
Filter Total Items: 18
No Result Found
Filter Total Items: 26
No results found.
Filter Total Items: 55
The sedimentary record of the 2018 Anchorage Earthquake in Eklutna Lake, Alaska: Calibrating the lacustrine seismograph The sedimentary record of the 2018 Anchorage Earthquake in Eklutna Lake, Alaska: Calibrating the lacustrine seismograph
The 30 November 2018 Mw 7.1 Anchorage earthquake caused modified Mercalli intensities of V¼ to V½ at Eklutna Lake (south central Alaska). A few hours after the earthquake, a “dirt streak” was observed on the lake surface, followed by a peak in sediment turbidity values (∼80 times normal) at a drinking water facility, which receives water from the lake through a pipe. These observations...
Authors
Maarten Van Daele, Peter J. Haeussler, Robert C. Witter, Nore Praet, Marc De Batist
Ground failure from the Anchorage, Alaska, earthquake of 30 November 2018 Ground failure from the Anchorage, Alaska, earthquake of 30 November 2018
Investigation of ground failure triggered by the 2018 MwMw 7.1 Anchorage earthquake showed that landslides, liquefaction, and ground cracking all occurred and caused significant damage. Shallow rock falls and rock slides were the most abundant types of landslides, but they occurred in smaller numbers than global models that are based on earthquake magnitude predict; this might result...
Authors
Randall Jibson, Alex Grant, Robert C. Witter, Kate Allstadt, Eric Thompson, Adrian Bender
The 30 November 2018 Mw7.1 Anchorage Earthquake The 30 November 2018 Mw7.1 Anchorage Earthquake
The Mw 7.1 47 km deep earthquake that occurred on 30 November 2018 had deep societal impacts across southcentral Alaska and exhibited phenomena of broad scientific interest. We document observations that point to future directions of research and hazard mitigation. The rupture mechanism, aftershocks, and deformation of the mainshock are consistent with extension inside the Pacific plate...
Authors
Michael West, Adrian Bender, Matthew Gardine, Lea Gardine, Kara Gately, Peter J. Haeussler, Wael Hassan, Franz Meyer, Cole Richards, Natalia Ruppert, Carl Tape, John Thornley, Robert Witter
Evidence for frequent, large tsunamis spanning locked and creeping parts of the Aleutian megathrust Evidence for frequent, large tsunamis spanning locked and creeping parts of the Aleutian megathrust
At the eastern end of the 1957 Andreanof Islands magnitude-8.6 earthquake rupture, Driftwood Bay (Umnak Island) and Stardust Bay (Sedanka Island) lie along presently locked and creeping parts of the Aleutian megathrust, respectively, based on satellite geodesy onshore. Both bays, located 200-km apart, face the Aleutian trench and harbor coastal evidence for tsunami inundation in 1957...
Authors
Robert C. Witter, Richard Briggs, Simon Engelhart, Guy Gelfenbaum, Richard Koehler, Alan Nelson, SeanPaul La Selle, Reide Corbett, Kristi Wallace
Wetland stratigraphic evidence for variable megathrust earthquake rupture modes at the Cascadia subduction zone Wetland stratigraphic evidence for variable megathrust earthquake rupture modes at the Cascadia subduction zone
Although widespread agreement that the Cascadia subduction zone produces great earthquakes of magnitude 8 to 9 was reached decades ago, debate continues about the rupture lengths, magnitudes, and frequency of megathrust earthquakes recorded by wetland stratigraphy fringing Cascadia’s estuaries. Correlation of such coastal earthquake evidence along the subduction zone has largely relied...
Authors
Alan Nelson, Robert C. Witter, Simon Englehart, Andrea Hawkers, Benjamin Horton
New constraints on coseismic slip during southern Cascadia subduction zone earthquakes over the past 4600 years implied by tsunami deposits and marine turbidites New constraints on coseismic slip during southern Cascadia subduction zone earthquakes over the past 4600 years implied by tsunami deposits and marine turbidites
Forecasting earthquake and tsunami hazards along the southern Cascadia subduction zone is complicated by uncertainties in the amount of megathrust fault slip during past ruptures. Here, we estimate slip on hypothetical ruptures of the southern part of the megathrust through comparisons of late Holocene Cascadia earthquake histories derived from tsunami deposits on land and marine...
Authors
George Priest, Robert C. Witter, Yinglong Zhang, Chris Goldfinger, Kelin Wang, Jonathan Allan
Microfossil measures of rapid sea-level rise: Timing of response of two microfossil groups to a sudden tidal-flooding experiment in Cascadia Microfossil measures of rapid sea-level rise: Timing of response of two microfossil groups to a sudden tidal-flooding experiment in Cascadia
Comparisons of pre-earthquake and post-earthquake microfossils in tidal sequences are accurate means to measure coastal subsidence during past subduction earthquakes, but the amount of subsidence is uncertain, because the response times of fossil taxa to coseismic relative sea-level (RSL) rise are unknown. We measured the response of diatoms and foraminifera to restoration of a salt...
Authors
B. Horton, Yvonne Milker, T. Dura, Kelin Wang, W.T. Bridgeland, Laura Brophy, M. Ewald, Nicole Khan, S.E. Engelhart, Alan Nelson, Robert C. Witter
Sculpted by water, elevated by earthquakes—The coastal landscape of Glacier Bay National Park, Alaska Sculpted by water, elevated by earthquakes—The coastal landscape of Glacier Bay National Park, Alaska
Within Glacier Bay National Park in southeastern Alaska, the Fairweather Fault represents the onshore boundary between two of Earth’s constantly moving tectonic plates: the North American Plate and the Yakutat microplate. Satellite measurements indicate that during the past few decades the Yakutat microplate has moved northwest at a rate of nearly 5 centimeters per year relative to the...
Authors
Robert C. Witter, Adam LeWinter, Adrian Bender, Craig Glennie, David Finnegan
Evidence for shallow megathrust slip across the Unalaska seismic gap during the great 1957 Andreanof Islands earthquake, eastern Aleutian Islands, Alaska Evidence for shallow megathrust slip across the Unalaska seismic gap during the great 1957 Andreanof Islands earthquake, eastern Aleutian Islands, Alaska
We reassess the slip distribution of the 1957 Andreanof Islands earthquake in the eastern part of the aftershock zone where published slip models infer little or no slip. Eyewitness reports, tide gauge data, and geological evidence for 9–23 m tsunami runups imply seafloor deformation offshore Unalaska Island in 1957, in contrast with previous studies that labeled the area a seismic gap...
Authors
D. J. Nicolsky, J.T. Freymueller, Robert C. Witter, E. Suleimani, R.D. Koehler
Differences in coastal subsidence in southern Oregon (USA) during at least six prehistoric megathrust earthquakes Differences in coastal subsidence in southern Oregon (USA) during at least six prehistoric megathrust earthquakes
Stratigraphic, sedimentologic (including CT 3D X-ray tomography scans), foraminiferal, and radiocarbon analyses show that at least six of seven abrupt peat-to-mud contacts in cores from a tidal marsh at Talbot Creek (South Slough, Coos Bay), record sudden subsidence (relative sea-level rise) during great megathrust earthquakes at the Cascadia subduction zone. Data for one contact are...
Authors
Yvonne Milker, Alan Nelson, Benjamin Horton, Simon Engelhart, Lee-Ann Bradley, Robert C. Witter
Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust
Current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust. Here we report geological evidence for large tsunamis, occurring on average every 300–340 years, near the source areas of the 1946 and 1957 Aleutian tsunamis. These areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate...
Authors
Robert C. Witter, G. Carver, Richard Briggs, Guy Gelfenbaum, R.D. Koehler, SeanPaul M. La Selle, Adrian Bender, S.E. Engelhart, E. Hemphill-Haley, Troy Hill
Variability of intertidal foraminferal assemblages in a salt marsh, Oregon, USA Variability of intertidal foraminferal assemblages in a salt marsh, Oregon, USA
We studied 18 sampling stations along a transect to investigate the similarity between live (rose Bengal stained) foraminiferal populations and dead assemblages, their small-scale spatial variations and the distribution of infaunal foraminifera in a salt marsh (Toms Creek marsh) at the upper end of the South Slough arm of the Coos Bay estuary, Oregon, USA. We aimed to test to what extent
Authors
Yvonne Milker, Benjamin Horton, Alan Nelson, Simon Engelhart, Robert C. Witter
Non-USGS Publications**
Engelhart, S. E., Horton, B. P., Nelson, A. R., Hawkes, A. D., Witter, R. C., Wang, K., Wang P.-L., and Vane, C. H., 2013, Testing the use of microfossils to reconstruct great earthquakes at Cascadia, Geology, doi:10.1130/G34544.1.
Engelhart, S. E., B. P. Horton, C. H. Vane, A. R. Nelson, R. C. Witter, S. R. Brody, and A. D. Hawkes, 2013, Modern foraminifera, δ13C, and bulk geochemistry of central Oregon tidal marshes and their application in paleoseismology, Palaeogeography, Palaeoclimatology, Palaeoecology, doi:10.1016/j.palaeo.2013.02.032.
Kelson, K., R. C. Witter, A. Tassara, I. Ryder, C. Ledezma, G. Montalva, D. Frost, N. Sitar, R. Moss, and L. Johnson, 2012, Coseismic tectonic surface deformation during the 2012 Maule, Chile, Mw 8.8 earthquake, Earthquake Spectra, v. 28, n. S1, p. 39-54.
Pilarczyk, J. E., Horton, B. P., Witter, R. C., Vane, C. H., Chagué-Goff, C., Goff, J., 2012, Sedimentary and foraminiferal evidence of the 2011 Tohoku-oki tsunami on the Sendai coastal plain, Japan. Sedimentary Geology. doi:10.1016/j.sedgeo.2012.08.011.
Richmond, B., W. Szczucinski, C.Chague-Goff, K. Goto, D. Sugawara, R. Witter, D.R. Tappin, B. Jaffe, S. Fujino, Y. Nishimura, and J. Goff, 2012, Erosion, deposition and landscape change on the Sendai coastal plain, Japan, resulting from the March 11, 2011 Tohoku-oki tsunami, Sedimentary Geology, doi:10.1016/j.sedgeo.2012.08.005.
Witter, R.C., Y.J. Zhang, K. Wang, C. Goldfinger, and G.R. Priest, 2012, Coseismic slip on the southern Cascadia megathrust implied by tsunami deposits in an Oregon lake and earthquake-triggered marine turbidites, Journal of Geophysical Research, 117, B10303, doi:10.1029/2012JB009404.
Allan, J., P. Komar, P. Ruggiero, and R.C. Witter, 2012, The March 2011 Tohoku tsunami and its impacts along the U.S. West Coast, Journal of Coastal Research, Journal of Coastal Research, v. 28, n. 5, p. 1142-1153, doi:10.2112/jcoastres-d-11-00115.1.
Witter, R. C., B. Jaffe, Y. Zhang, and G. R. Priest, 2012, Reconstructing Hydrodynamic Flow Parameters of the 1700 Tsunami at Cannon Beach, Oregon, USA, Natural Hazards, doi:10.1007/s11069-011-9912-7.
Horton, B. P., Sawai, Y., Hawkes, A. D., and Witter, R. C., 2011, Sedimentology and paleontology of a tsunami deposit accompanying the great Chilean earthquake of February 2010: Marine Micropaleontology, v. 79, no. 3-4, p. 132–138, doi:10.1016/j.marmicro.2011.02.001
Zhang, Y. J., R. C. Witter, and G. R. Priest, 2011, Tsunami-tide interaction in 1964 Prince William Sound tsunami, Ocean Modelling, v. 40, p. 246–259, doi:10.1016/j.ocemod.2011.09.005
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.