Samuel Y Johnson

Seafloor Mapping - Geologic framework, hazards, and habitats


Sam Johnson is a Research Geologist in the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), an organization of about 100 research and support staff based in Santa Cruz and Menlo Park, CA.  He served as PCMSC Center Director from 2003 to 2008. He currently designs, coordinates, and conducts research projects that focus on seafloor and benthic habitat mapping, coastal and marine geomorphology and geologic framework, coastal evolution, and coastal earthquake and tsunami hazards.  He helped plan and is the USGS lead for the multi-agency California Seafloor Mapping Program. His present research is focused on active tectonics and hazards offshore central California (Santa Barbara Channel to Cape Mendocino).

Recent Accomplishments


  • B.A. (1975) University of California, Santa Cruz (Earth Sciences)
  • M.S. (1978) University of Washington (Geological Sciences)
  • Ph.D. (1982) University of Washington Geological Sciences

Professional Studies/Experience

  • 1982-1984 - Assistant Professor, Washington State University
  • 1984 to 2003 - Research Geologist, USGS Energy and Earthquake Hazards Programs
  • 2003 to 2008 - Center Director, USGS Pacific Coastal and Marine Science Center
  • 2008 to 2019 - Research Geologist, USGS Pacific Coastal and Marine Science Center
  • 2019 to present - Research Geologist Emeritus, USGS Pacific Coastal and Marine Science Center


Research Interests

  • Sea floor mapping and geomorphology
  • Coastal and marine sedimentology and stratigraphy
  • Active Tectonics
  • Geologic framework and hazards

Professional societies/affiliations/committees/editorial boards

  • Geological Society of America (Fellow) 
  • American Geophysical Union 
  • Society for Sedimentary Geology 
  • Seismological Society of America

Honors, awards, recognition, elected offices

  • Department of Interior Distinguished Service Award (2019)

Scientific/Oral Presentations, Abstracts

Selected publications:

Johnson, S.Y., Beeson, J.W., Watt, J.T., Sliter, R.W., and Papesh, A., 2020, Controls on sediment distribution in the coastal zone of the Central California Transform Continental Margin, USA: Marine Geology, v. 420, 29 p.,

Johnson, S.Y., and Beeson, J.W., 2019, Shallow Structure and Geomorphology Along the Offshore Northern San Andreas Fault, Tomales Point to Fort Ross, California: Bulletin of the Seismological Society of America, v. 109, 22 p.  

Johnson, S.Y., Watt, J.T., Hartwell, S.R., and Kluesner, J.W., 2018, Neotectonics of the Big Sur Bend, San Gregorio-Hosgri fault system, central California: Tectonics, 25 p. DOI: 10.1029/2017TC004724

Johnson, S.Y., Hartwell, S.H., Sorlien, C.C., Dartnell, P., and Ritchie, A.R., 2017, Shelf evolution along a transpressive transform margin, Santa Barbara Channel, California: Geosphere, v. 13, p. 2041-2077.

Maier, K., Johnson, S.Y., and Hart, P., 2018,  Controls on submarine canyon head evolution: Monterey Canyon, offshore central California: Marine Geology, v. 404, 24-40.

Johnson, S.Y., Cochrane, G.R., Golden, N.E., Dartnell, P., Hartwell, S.R., Cochran, S.A., and Watt, J.T., 2017, The California Seafloor Mapping Program - Providing science and geospatial data for California’s State Waters: Ocean and Coastal Management, v. 140, p. 88-104.

Beeson, J.W., Johnson, S.Y., Goldfinger, C., 2017, The transtensional offshore section of the northern San Andreas fault: fault zone geometry, Late-Pleistocene to Holocene sediment deposition, shallow deformation patterns, and asymmetric basin growth: Geosphere, v, 13, p. 1173-1206.

Johnson, S.Y., Hartwell, S.R., and Dartnell, P., 2014, Offset of latest Pleistocene shoreface reveals slip rates on the Hosgri strike-slip fault, offshore central California: Bulletin of the Seismological Society of America, p. 1650-1652.

Johnson, S.Y. and Watt, J.T., 2012, Influence of fault trend, bends, and convergence on shallow structure and geomorphology of the Hosgri strike-slip fault, offshore Central California: Geosphere, v. 8, p. 1632-1656

Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Kvitek, R.G., Greene, H.G., Krigsman, L.M., Endris, C.A., Clahan, K.B., Sliter, R.W., Wong, F.L., Yoklavich, M.M., and Normark, W.R. (S.Y. Johnson, ed.), 2012, California State Waters Map Series—Hueneme Canyon and vicinity, California: U.S. Geological Survey Scientific Investigations Map 3225, 41 p., 12 sheets,

NOTE: Between 2012 and 2018, 25 publications similar to USGS SIM 3225 (above citation) have now been published by USGS for the California Seafloor Mapping Program, covering ~32% of California’s coast. See:

Fisher, M.A., Hyndman, R.D., Johnson, S.Y., Brocher, T., Crosson, R.S., Wells, R.E., Calvert, A.J., and ten Brink, U.S., 2005, Crustal structure and earthquake hazards of the subduction zone in southwestern British Columbia and western Washington:  U.S. Geological Survey Professional Paper 1661-C, 28 p., 3 plates.

Johnson, S.Y., Blakely, R.J., Stephenson, W.J., Dadisman, S.V., and Fisher, M.A., 2004, Active shortening of the Cascadia forearc and implications for seismic hazards of the Puget Lowland: Tectonics, v. 23, 27 pages, TC1011, doi:10.1029/2003TC001507

Johnson, S.Y., Nelson A.R., Personius, S.F., Wells, R.E., Kelsey, H.M., Sherrod, B.L., Okumura, K., Koehler, R. III., Witter, R., Bradley, L.A., and Harding, D.J., 2004, Evidence for late Holocene earthquakes on the Utsalady Point fault, northern Puget Lowland, Washington. Seismological Society of America Bulletin, v. 94, p. 2219-2316.

Johnson, S.Y., Stephenson, W.J., Morgan, L.A., Shanks, W.C., and Pierce, K.L., 2003, Hydrothermal and tectonic activity in northern Yellowstone Lake, Wyoming: Geological Society of America Bulletin, v. 115, p. 954-971.

Nelson, A.R., Johnson, S.Y., Kelsey, H.M., Wells, R.E., Sherrod, B.L., Pezzopane, S.K., Bradley, L., and Koehler, R.D., III, 2003, Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Washington: Geological Society of America Bulletin, v. 115, p. 1388-1403.

Blakely, R.J., Wells, R.E., Weaver, C.S., and Johnson, S.Y., 2002, Location, structure, and seismicity of the Seattle fault, Washington:  Geological Society of America Bulletin, v. 114, p. 169-177.

Bourgeois, J., and Johnson, S.Y., 2001, Geologic evidence of earthquakes at the Snohomish delta, Washington, in the past 1200 years: Geological Society of America Bulletin, v. 113, p. 482-494.

Johnson, S.Y., Dadisman, S.V., Mosher, D.C., Blakely, R.J., and Childs, J.R., 2001, Active tectonics of the Devils Mountain fault and related structures, northern Puget Lowland and eastern Strait of Juan de Fuca region, Pacific Northwest:  U.S. Geological Survey Professional Paper 1643, 45 p., 2 plates.

Mosher, D.C., and Johnson, S.Y. (eds.), Rathwell, G.J., Kung, R.B., and Rhea, S.B. (compilers), 2001, Neotectonics of the eastern Strait of Juan de Fuca; a digital geological and geophysical atlas: Geological Survey of Canada Open File Report D3931 (CD digital product), 18 maps and accompanying text and figures.

Johnson, S.Y., Dadisman, S.V., Childs, J.R., and Stanley, W.D., 1999, Active tectonics of the Seattle fault and central Puget Lowland - Implications for earthquake hazards:  Geological Society of America Bulletin, v. 111, p. 1042-1053 and oversize insert.

Johnson, S.Y., Potter, C.J., Armentrout, J.M., Miller, J.J., Finn, C., and Weaver, C.S., 1996, The southern Whidbey Island fault: An active structure in the Puget Lowland, Washington:  Geological Society of America Bulletin, v. 108, p. 334-354 and oversize insert.

Johnson, S.Y., Potter, C.J., and Armentrout, J.M., 1994, Origin and evolution of the Seattle fault and Seattle basin: Geology, v. 22, p. 71-74 and oversize insert.

Johnson, S.Y., and Alam, A.M.N., 1991, Sedimentation and tectonics of the Sylhet trough, Bangladesh: Geological Society of America Bulletin, v. 103, p. 1513-1527.