Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the 

U.S. Government

This map was printed on an electronic plotter directly from digital files. Dimensional calibration may vary between electronic plotters 

and between X and Y directions on the same plotter, and paper may change size due to atmospheric conditions; therefore, scale and 

proportions may not be true on plots of this map.

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://pubs.usgs.gov/sim/3281/

Suggested Citation: Johnson, S.Y., Phillips, E.L., Ritchie, A.C., Wong, F.L., Sliter, R.W., Draut, A.E., Conrad, J.E., and Hart, P.E., 2013, 

Local (Offshore of Santa Barbara map area) and regional (offshore from Refugio Beach to Hueneme Canyon) shallow-subsurface 

geology and structure, Santa Barbara Channel, California, sheet 9 in Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, 

E.L., Ritchie, A.C., Greene, H.G., Krigsman, L.M., Kvitek, R.G., Dieter, B.E., Endris, C.A., Seitz, G.G., Sliter, R.W., Erdey, M.D., Gutierrez, 

C.I., Wong, F.L., Yoklavich, M.M., Draut, A.E., Hart, P.E., and Conrad, J.E. (S.Y. Johnson and S.A. Cochran, eds.), California State 

Waters Map Series—Offshore of Santa Barbara, California: U.S. Geological Survey Scientific Investigations Map 3281, pamphlet 45 

p., 11 sheets, scale 1:24,000, http://dx.doi.org/10.3133/sim3281.

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3281

2010 that have inferred or measured magnitudes greater than 2.0 is shown on Map C. 

Fault locations are based on our mapping within California’s State Waters and on a 

generalized compilation of mapping from Heck (1998), Minor and others (2009), and 

Jennings and Bryant (2010). Earthquake data are from the Southern California Earthquake Catalog (Southern California Earthquake Data Center, 2010). Although earthquake locations have been determined by the CalTech network since 1932, 

significantly greater precision began in 1969 with installation of a U.S. Geological 

Survey (USGS) seismographic network (Lee and Vedder, 1973; Southern California 

Earthquake Data Center, 2010). Epicentral data indicate that recent seismicity in the 

eastern and central Santa Barbara Channel is characterized by earthquake swarms, 

relatively frequent minor earthquakes, and infrequent major earthquakes.

REFERENCES CITED

Caldwell, R.J., Taylor, L.A., Eakins, B.W., Carignan, K.S., Grothe, P.R., Lim, E., and 

Friday, D.Z., 2010, Digital elevation models of Santa Monica, California—

Procedures, data sources, and analysis: NOAA Technical Memorandum NESDIS 

NGDC-46, NOAA National Geophysical Data Center, available at 

http://www.ngdc.noaa.gov/dem/squareCellGrid/download/663.

Carignan, K.S., Taylor, L.A., Eakins, B.W., Warnken, R.R., Lim, E., and Medley, P.R., 

2009, Digital elevation model of Santa Barbara, California—Procedures, data 

sources, and analysis: NOAA Technical Memorandum NESDIS NGDC-29, 

NOAA National Geophysical Data Center, available at http://www.ngdc.noaa.gov/

dem/squareCellGrid/download/603.

Heck, R.G., 1998, Santa Barbara Channel regional formline map, top Monterey 

Formation, in Kunitomi, D.S., Hopps, T.E., and Galloway, J.M., eds., Structure 

and petroleum geology, Santa Barbara Channel, California: American Association 

of Petroleum Geologists, Pacific Section, and Coast Geological Society, 

Miscellaneous Publication 46, 1 plate.

Jennings, C.W., and Bryant, W.A., 2010, Fault activity map of California: California 

Geological Survey Geologic Data Map no. 6, scale 1:750,000.

Lee, W.H.K., and Vedder, J.G., 1973, Recent earthquake activity in the Santa Barbara 

Channel region: Bulletin of the Seismological Society of America, v. 63, p. 

1,757–1,773.

Minor, S.A., Kellogg, K.S., Stanley, R.G., Gurrola, L.D., Keller, E.A., and Brandt, 

T.R., 2009, Geologic map of the Santa Barbara coastal plain area, Santa Barbara 

County, California: U.S. Geological Survey Scientific Investigations Map 3001, 

scale 1:25,000, 1 sheet, pamphlet 38 p., available at http://pubs.usgs.gov/

sim/3001/.

Southern California Earthquake Data Center, 2010, Southern California Earthquake 

Catalog: Southern California Earthquake Data Center database, available at 

http://www.data.scec.org/eq-catalogs/index.html. 

Wong, F.L., Phillips, E.L., Johnson, S.Y, and Sliter, R.W., 2012, Modeling of depth to 

base of Last Glacial Maximum and seafloor sediment thickness for the California 

State Waters Map Series, eastern Santa Barbara Channel, California: U.S. 

Geological Survey Open-File Report 2012–1161, 16 p., available at 

http://pubs.usgs.gov/of/2012/1161/.

DISCUSSION

This sheet includes maps that show the thickness and the depth to base of uppermost Pleistocene and Holocene (in other words, post–Late Glacial Maximum) deposits 

for the Offshore of Santa Barbara map area (Maps A, B), as well as for a larger area 

that extends about 115 km along the coast from Hueneme Canyon to Refugio Beach 

(Maps D, E) to establish a regional context. To make these maps, water bottom and 

depth to base of the post–Last Glacial Maximum horizons were mapped from seismicreflection profiles. The difference in the two horizons was exported for every shot 

point as XY coordinates (UTM zone 11) and two-way travel time (TWT). The thickness of the post–Last Glacial Maximum unit (Maps B, E) was determined by applying 

a sound velocity of 1,600 m/sec to the TWT. The thickness points were interpolated to 

a preliminary continuous surface, overlaid with zero-thickness bedrock outcrops (sheet 

10 of this report), and contoured (Wong and others, 2012). Data within Hueneme 

Canyon were excluded from the contouring because the seismic-reflection data are too 

sparse to adequately image the highly variable changes in sediment thickness that 

characterize the canyon (Maps A, B, D, E).

Several factors required manual editing of the preliminary thickness maps to 

make the final products. The Red Mountain Fault Zone (RMFZ), Pitas Point Fault 

(PPF), and Oak Ridge Fault (ORF) disrupt the sediment sequence in the region (Maps 

D, E). The data points also are dense along tracklines (about 1 m apart) and sparse 

between tracklines (1–2 km apart), resulting in contouring artifacts. To incorporate the 

effect of the faults, to remove irregularities from interpolation, and to reflect other 

geologic information and complexity, the resulting interpolated contours were modified. Contour modifications and regridding were repeated several times to produce the 

final regional sediment-thickness map (Wong and others, 2012). 

 Data to determine the depth to base of the post–Last Glacial Maximum unit was 

similarly processed and contoured. However, this preliminary data set was set aside in 

favor of a surface determined by subtracting the modified thickness data from multibeam bathymetry collected separately (see sheet 1). The depth of this surface in the 

Hueneme Canyon to Refugio Beach area ranges from 12 to 190 m (Map D; see also, 

Wong and others, 2012).

 Five different “domains” of sediment thickness, which are bounded either by 

faults or by Hueneme Canyon, are recognized on the regional maps (Maps D, E): (1) 

Refugio Beach to the south strand of the Red Mountain Fault Zone (RMFZ); (2) 

between the south strand of the Red Mountain Fault Zone and the Pitas Point Fault 

(PPF); (3) between the Pitas Point Fault and the Oak Ridge Fault (ORF); (4) between 

the Oak Ridge Fault and Hueneme Canyon; and (5) south of Hueneme Canyon. These 

data highlight the contrast among three general zones of sediment thickness: (1) the 

uplifted, sediment-poor Santa Barbara shelf (domain 1; mean sediment thickness of 3.5 

m); (2) a transitional zone (domain 2; mean sediment thickness of 18.0 m); and (3) the 

subsiding, sediment-rich delta and shelf offshore of the Ventura and Santa Clara Rivers 

and Calleguas Creek (domains 3, 4, and 5; mean sediment thicknesses of 39.3, 38.9, 

and 28.3 m, respectively).

In the Offshore of Santa Barbara map area, sediment thickness ranges from 0 to 

18 m, with a mean thickness of 3.4 m. The thickest sediment accumulations are in 

three nearshore to inner-shelf depocenters, which have positive seafloor relief characterized by relatively flat upper surfaces and steeper seaward-dipping slopes. These 

features are correlated with steep onland coastal watersheds and, thus, are interpreted 

as delta-mouth bars. Sediment is notably lacking or forms only a thin veneer over 

bedrock outcrops in much of the midshelf to outer shelf area.

The regional pattern of faults and of earthquakes occurring between 1932 and 

120° 119°40' 119°20' 119°

34°

34°20'

Kilometers 0 5 10

0 4 8 Nautical Miles

Santa Barbara Channel

 Santa 

Barbara

Ventura

CALIF.

MAP LOCATION

Limit of California’s

 State Waters

Santa Cruz Island Santa Rosa Island

Area of

 Map

Anacapa

 Island

Local (Offshore of Santa Barbara Map Area) and Regional (Offshore from Refugio Beach to Hueneme Canyon) 

Shallow-Subsurface Geology and Structure, Santa Barbara Channel, California

By

Samuel Y. Johnson, Eleyne L. Phillips, Andrew C. Ritchie, Florence L. Wong, Ray W. Sliter, Amy E. Draut, James E. Conrad, and Patrick E. Hart

2013

ONE MILE = 0.869 NAUTICAL MILES

20 10 0 20 KILOMETERS

80000 60000 40000 20000 0 80000 FEET

20 10 0 20 MILES

SCALE 1:300 000

ONE MILE = 0.869 NAUTICAL MILES

10 5 0 10 KILOMETERS

40000 30000 20000 10000 0 40000 FEET

10 5 0 10 MILES

SCALE 1:200 000

ONE MILE = 0.869 NAUTICAL MILES

1 0.5 0 1 KILOMETER

7000 3500 0 7000 FEET

2 1 0 2 MILES

SCALE 1:50 000

APPROXIMATE MEAN

DECLINATION, 2013 

13°

MAGNETIC NORTH

TRUE NORTH

MAGNETIC NORTH

TRUE NORTH

APPROXIMATE MEAN

DECLINATION, 2013 

13°

APPROXIMATE MEAN

DECLINATION, 2013

MAGNETIC NORTH

12 / ° 1 2

TRUE NORTH

Onshore elevation data from NOAA Coastal Services 

Center (data collected by EarthData International in 

2002-2003). California's State Waters limit from NOAA 

Office of Coast Survey 

Universal Transverse Mercator projection, Zone 11N

Depth and thickness mapped by Samuel Y. 

Johnson and Eleyne L. Phillips, 2010-2011

GIS database and digital cartography by Eleyne 

L. Phillips, Andrew C. Ritchie, and Florence L. 

Wong

Onshore elevation data from NOAA Coastal Services 

Center (data collected by EarthData International in 

2002-2003) and from National Elevation Dataset, 2011. 

California's State Waters limit from NOAA Office of Coast 

Survey

Universal Transverse Mercator projection, Zone 11N

Compiled by Andrew C. Ritchie and Samuel Y. 

Johnson, 2011

Onshore elevation data from NOAA Coastal Services Center (data collected by EarthData International in 2002-2003). 

Shaded-relief bathymetry from data collected by Monterey Bay Aquarium Research Institute in 1998, by U.S. 

Geological Survey in 2006, by California State University, Monterey Bay, Seafloor Mapping Lab in 2006-2007, and by 

Fugro Pelagos for U.S. Army Corps of Engineers in 2009; data compiled in NOAA Tsunami Inundation Project 1/3 

arc-second DEMs for Santa Barbara, CA (Carignan and others, 2009), and Santa Monica, CA (Caldwell and others, 

2010). California's State Waters limit from NOAA Office of Coast Survey

Universal Transverse Mercator projection, Zone 11N

NOT INTENDED FOR NAVIGATIONAL USE

Depth and thickness mapped by Samuel Y. Johnson and 

Eleyne L. Phillips, 2010-2011

GIS database and digital cartography by Andrew C. 

Ritchie, Eleyne L. Phillips, and Florence L. Wong

Edited by Taryn A. Lindquist 

Manuscript approved for publication December 12, 2013

RMFZ

PPF

ORF

34°30'

34°15'

34°

119°

119°45'

119°30'

119°15'

120°

120°15'

34°30'

34°15'

34°

119°

119°45'

119°30'

119°15'

120°

120°15'

Santa Barbara

Ventura

Goleta

Hueneme

 Canyon

Oxnard

 Refugio

 Beach

Mugu

Canyon

Offshore of Santa

Barbara map area

Map E

0 – 0.1

0.1 – 2.5

2.5 – 5

5 – 7.5

7.5 – 10

10 – 12.5

12.5 – 15

15 – 17.5

17.5 – 20

20 – 22.5

22.5 – 25

25 – 27.5

27.5 – 30

30 – 32.5

32.5 – 35

35 – 37.5

37.5 – 40

40 – 42.5

42.5 – 45

45 – 47.5

47.5 – 50

50 – 52.5

52.5 – 55

55 – 57.5

EXPLANATION

Thickness of uppermost Pleistocene

and Holocene sediment, in meters 

Thickness contours

Index (10-m intervals)

Intermediate

Fault—ORF, Oak Ridge Fault; PPF, 

Pitas Point Fault; RMFZ, Red 

Mountain Fault Zone

3-nautical-mile limit of California’s 

State Waters

RMFZ

PPF

ORF

34°30'

34°15'

34°

119°

119°45'

119°30'

119°15'

120°

120°15'

34°30'

120°15'

120°

119°45'

119°30'

119°15'

119°

34°15'

34°

Santa Barbara

Ventura

Goleta

Oxnard

Hueneme

Canyon

 Refugio

 Beach

Offshore of Santa

Barbara map area

Map D

-190 – -185

-185 – -180

-180 – -175

-175 – -170

-170 – -165

-165 – -160

-160 – -155

-155 – -150

-150 – -145

-145 – -140

-140 – -135

-135 – -130

-130 – -125

-125 – -120

-120 – -115

-115 – -110

-110 – -105

-105 – -100

-100 – -95

-95 – -90

-90 – -85

-85 – -80

-80 – -75

-75 – -70

-70 – -65

-65 – -60

-60 – -55

-55 – -50

-50 – -45

-45 – -40

-40 – -35

-35 – -30

-30 – -25

-25 – -20

-20 – -15

-15 – -10

EXPLANATION

Depth to base of uppermost Pleistocene

and Holocene sediment, in meters 

Depth-to-base contours

Index (20-m intervals)

Intermediate

Fault—ORF, Oak Ridge Fault; PPF, 

Pitas Point Fault; RMFZ, Red 

Mountain Fault Zone

3-nautical-mile limit of California’s 

State Waters

120°30' 120° 119°30' 119°

120°30' 120° 119°30'

34°30'

34°

34°30'

34°

Offshore of Santa Barbara

map area and area of Maps A, B

Map C

2.0 – 2.49

2.5 – 2.99

3.0 – 3.49

 3.5 – 3.99

4.0 – 5.5

3-nautical-mile 

limit of California’s 

State Waters

Fault

EXPLANATION

Regional faults and 

earthquake epicenters, 

1932 – 2010

MAGNITUDE

Ventura

Refugio

Beach

Goleta Santa

Barbara

Area of Maps D, E

119°45' 119°40'

119°45' 119°40'

34°25'

34°20'

Santa Barbara

Montecito

0 – 0.1

0.1 – 2.5

2.5 – 5

5 – 7.5

7.5 – 10

10 – 12.5

12.5 – 15

15 – 17.5

17.5 – 20

20 – 22.5

22.5 – 25

25 – 27.5

EXPLANATION

Thickness of uppermost Pleistocene 

and Holocene sediment, in meters

Thickness contours

Index (10-m intervals)

Intermediate

Fault—Dashed where inferred; dotted 

where concealed

Antiform—Dotted where concealed

Synform—Dotted where concealed

3-nautical-mile limit of California’s 

State Waters

Area of “no data”—Areas where data are 

insufficient for contouring

Rincon Creek Fault

Red Mountain Fault (north strand)

119°45' 119°40'

119°45' 119°40'

34°25'

34°20'

34°25'

34°20'

Map A

Map B

Montecito

-100 – -95

-95 – -90

-90 – -85

-85 – -80

-80 – -75

-75 – -70

-70 – -65

-65 – -60

-60 – -55

EXPLANATION

Depth to base of uppermost Pleistocene 

and Holocene sediment, in meters

Depth-to-base contours

Index (20-m intervals)

Intermediate

Fault—Dashed where inferred; dotted 

where concealed

Antiform—Dotted where concealed

Synform—Dotted where concealed

3-nautical-mile limit of California’s 

State Waters

Area of “no data”—Areas where data are 

insufficient for contouring

Santa Barbara

-55 – -50

-50 – -45

-45 – -40

-40 – -35

-35 – -30

-30 – -25

-25 – -20

-20 – -15

-15 – -10

Rincon Creek Fault

Red Mountain Fault (north strand)

Scientific Investigations Map 3281

Sheet 9 of 11

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey