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://dx.doi.org/10.3133/ofr20151191

Suggested Citation: Johnson, S.Y., Hartwell, S.R., and Sliter, R.W., 2015, Seismic-reflection profiles, Offshore of Scott Creek map area, 

California, sheet 8 in Cochrane, G.R., Dartnell, P., Johnson, S.Y., Greene, H.G., Erdey, M.D., Dieter, B.E., Golden, N.E., Endris, C.A., 

Hartwell, S.R., Kvitek, R.G., Davenport, C.W., Watt, J.T., Krigsman, L.M., Ritchie, A.C., Sliter, R.W., Finlayson, D.P., and Maier, K.L. (G.R. 

Cochrane and S.A. Cochran, eds.), California State Waters Map Series—Offshore of Scott Creek, California: U.S. Geological Survey 

Open-File Report 2015–1191, pamphlet 40 p., 10 sheets, scale 1:24,000, http://dx.doi.org/10.3133/ofr20151191.

ISSN 2331-1258 (online) 

http://dx.doi.org/10.3133/ofr20151191

DISCUSSION

This map sheet shows seismic-reflection profiles from three different surveys of the Offshore of 

Scott Creek map area, providing imagery of the subsurface geology. The offshore part of the map area 

consists of gently (about 0.6° to 0.8°) offshore-dipping nearshore, inner shelf, and midshelf areas, 

extending to water depths of about 70 m at the limit of California’s State Waters. Most of the shelf is 

underlain by flat, sandy and muddy sediment; bedrock forms moderate-relief outcrops that locally 

extend from the shoreline out to water depths of as much as 45 m (see sheet 10). The seismicreflection profiles provide the data for interpreting subbottom stratigraphy, sediment thickness, and 

geologic structure (see sheets 9, 10).

Most profiles displayed on this sheet (figs. 1, 2, 3, 4, 6, 7, 9, 10) were collected in 2009 on U.S. 

Geological Survey (USGS) cruise S–N1–09–MB. The single-channel seismic-reflection data were 

acquired using a SIG 2Mille minisparker that used a 500-J high-voltage electrical discharge fired 2 

times per second, which, at normal survey speeds of 4 to 4.5 nautical miles per hour, gives a data 

trace every 1.0 to 1.5 m of lateral distance covered. The data were digitally recorded in standard 

SEG-Y 32-bit floating-point format, using Triton Subbottom Logger (SBL) software that merges 

seismic-reflection data with differential GPS-navigation data. After the survey, a short-window (20 

ms) automatic gain control algorithm was applied to the data, along with a 160- to 1,200-Hz bandpass 

filter and a heave correction that uses an automatic seafloor-detection window (averaged over 30 m of 

lateral distance covered). These data can resolve geologic features a few meters thick (hence, are 

considered “high-resolution”), down to subbottom depths of as much as 400 m. 

Figures 5 and 8 show migrated, deep-penetration, multichannel seismic-reflection profiles 

collected in 1976 and 1982 by WesternGeco on cruises W–14–76–SF and W–34–82–MB, respectively. These profiles and other similar data were collected in many areas offshore of California in the 

1970s and 1980s when these areas were considered a frontier for oil and gas exploration. Much of 

these data have been publicly released and are now archived at the USGS National Archive of Marine 

Seismic Surveys (U.S. Geological Survey, 2009). These data were acquired using a large-volume 

air-gun source that has a frequency range of 3 to 40 Hz and recorded with a multichannel hydrophone 

streamer about 2 km long. Shot spacing was about 30 m. These data can resolve geologic features that 

are 20 to 30 m thick, down to subbottom depths of about 4 km.

The Offshore of Scott Creek map area straddles the right-lateral San Gregorio Fault Zone, an 

important structure in the distributed transform boundary between the North American and Pacific 

plates (see, for example, Dickinson and others, 2005). This fault zone is part of a fault system that is 

present predominantly in the offshore for about 400 km from Point Conception in the south (where it 

is known as the Hosgri Fault; Johnson and Watt, 2012) to Bolinas and Point Reyes in the north (Bruns 

and others, 2002; Ryan and others, 2008). The San Gregorio Fault Zone in the map area is part of a 

90-km-long offshore segment that extends northward from Point Sur (about 75 km south of the map 

area), across outer Monterey Bay to Point Año Nuevo (1 km north of the map area) (see sheet 9; see 

also, Weber and Lajoie, 1980; Brabb and others, 1998; Wagner and others, 2002). Offshore parts of 

this fault zone are identified in seismic-reflection profiles on the basis of the abrupt truncation or 

warping of reflections and (or) the juxtaposition of reflection panels that have differing seismic 

parameters, such as amplitude, frequency, geometry, continuity, and vertical sequence. In this map 

area, the San Gregorio Fault forms a distributed shear zone about 2 km wide that includes two main 

fault strands (figs. 2, 3, 4, 6, 7, 9; see also, sheet 10). The nearshore east strand, known as the Coastways Fault, partly coincides with a prominent bathymetric lineament on the outer flank of nearshore 

bedrock outcrops present between Davenport and the mouth of Waddell Creek (see sheets 1, 2). The 

west strand, known as the Frijoles Fault, cuts across the flat, sediment-covered shelf. Cumulative 

lateral slip on the San Gregorio Fault Zone is thought to range from 4 to 10 mm/yr, on the basis of 

field observations at Point Año Nuevo (Weber, 1994; U.S. Geological Survey and California Geological Survey, 2010).

The high-resolution seismic-reflection profiles (figs. 1, 2, 3, 4, 6, 7, 9, 10) show a lower unit of 

deformed Neogene bedrock and one or two upper units (pink and blue shading) that consist of upper 

Quaternary sediments. Bedrock is characterized by folded and faulted, moderate- to high-amplitude, 

variably continuous, parallel to subparallel reflections (terminology from Mitchum and others, 1977). 

Underlying strata east of the Coastways Fault consist of the upper Miocene Santa Cruz Mudstone; 

west of the fault, underlying strata are inferred to consist of a mix of Neogene rocks that include the 

Monterey Formation (middle and upper Miocene), the Purisima Formation (upper Miocene and 

Pliocene; Powell and others, 2007), and possibly the Santa Cruz Mudstone (upper Miocene). 

Throughout the map area, the contact between the Neogene bedrock and the overlying upper 

Quaternary sediments is an angular unconformity. Two upper Quaternary units are recognized in the 

profiles. The lower unit (pink shading; figs. 2, 4, 7), which is present only in the south half of the map 

area, notably consists of low-amplitude, low-angle (1° to 3°), offshore-dipping clinoforms 

(Catuneanu, 2006) that are as thick as 15 m. The upper unit (blue shading; figs. 1, 2, 3, 4, 6, 7, 9, 10) 

typically is characterized by low-amplitude, continuous to moderately continuous, diffuse, subparallel 

reflections, and it has a maximum thickness of about 12 m. 

Our preferred hypothesis is that the clinoforms in the lower (pink shading in profiles) of the two 

upper Quaternary units represent a progradational shoreface that formed between about 30,000 and 

21,000 years ago during the sea-level regression of marine-isotope stage 2 (Waelbroeck and others, 

2002). The overlying upper unit (blue shading in profiles) represents shelf deposits that formed during 

the sea-level transgression of the last about 21,000 years. In this interpretation, the surface at the base 

of the upper unit throughout the map area is a transgressive surface of erosion that formed as the 

shoreface migrated landward. Alternatively, Grossman and others (2006) suggested that both of these 

units were deposited in the last about 21,000 years, during the latest Pleistocene and Holocene 

sea-level rise.

REFERENCES CITED

Brabb, E.E., Graymer, R.W., and Jones, D.L., 1998, Geology of the onshore part of San Mateo 

County, California—A digital database: U.S. Geological Survey Open-File Report 98–137, scale 

1:62,500, available at http://pubs.usgs.gov/of/1998/of98-137/.

Bruns, T.R., Cooper, A.K., Carlson, P.R., and McCulloch, D.S., 2002, Structure of the submerged San 

Andreas and San Gregorio Fault zones in the Gulf of Farallones as inferred from high-resolution 

seismic-reflection data, in Parsons, T., ed., Crustal structure of the coastal and marine San 

Francisco Bay region, California: U.S. Geological Survey Professional Paper 1658, p. 77–117, 

available at http://pubs.usgs.gov/pp/1658/.

Catuneanu, O., 2006, Principles of sequence stratigraphy: Amsterdam, Elsevier, 375 p.

Dickinson, W.R., Ducea, M., Rosenberg, L.I., Greene, H.G., Graham, S.A., Clark, J.C., Weber, G.E., 

Kidder, S., Ernst, W.G., and Brabb, E.E., 2005, Net dextral slip, Neogene San Gregorio–Hosgri 

fault zone, coastal California—Geologic evidence and tectonic implications: Geological Society 

of America Special Paper 391, 43 p.

Grossman, E.E., Eittreim, S.L., Field, M.E., and Wong, F.L., 2006, Shallow stratigraphy and 

sedimentation history during high-frequency sea-level changes on the central California shelf: 

Continental Shelf Research, v. 26, p. 1,217–1,239, doi:10.1016/j.csr.2006.04.001.

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. 1,632–1,656, doi:10.1130/GES00830.1.

Mitchum, R.M., Jr., Vail, P.R., and Sangree, J.B., 1977, Seismic stratigraphy and global changes of 

sea level, part 6—Stratigraphic interpretation of seismic reflection patterns in depositional 

sequences, in Payton, C.E., ed., Seismic stratigraphy—Applications to hydrocarbon exploration: 

Tulsa, Okla., American Association of Petroleum Geologists, p. 117–133.

Powell, C.L., II, Barron, J.A., Sarna-Wojcicki, A.M., Clark, J.C., Perry, F.A., Brabb, E.E., and Fleck, 

R.J., 2007, Age, stratigraphy, and correlations of the late Neogene Purisima Formation, central 

California Coast Ranges: U.S. Geological Survey Professional Paper 1740, 32 p., available at 

http://pubs.usgs.gov/pp/2007/1740/.

Ryan, H.F., Parsons, T., and Sliter, R.W., 2008, Vertical tectonic deformation associated with the San 

Andreas fault zone offshore of San Francisco, California: Tectonophysics, v. 429, p. 209–224, 

doi:10.1016/j.tecto.2008.06.011.

U.S. Geological Survey, 2009, National Archive of Marine Seismic Surveys: U.S. Geological Survey 

database, accessed April 5, 2014, at http://walrus.wr.usgs.gov/NAMSS/.

U.S. Geological Survey and California Geological Survey, 2010, Quaternary fault and fold database 

of the United States: U.S. Geological Survey database, accessed April 4, 2013, at 

http://earthquake.usgs.gov/hazards/qfaults/.

Waelbroeck, C., Labeyrie, L., Michel, E., Duplessy, J.C., McManus, J.F., Lambeck, K., Balbon, E., 

and Labracherie, M., 2002, Sea-level and deep water temperature changes derived from benthic 

foraminifera isotopic records: Quaternary Science Reviews, v. 21, p. 295–305.

Wagner, D.L., Greene, H.G., Saucedo, G.J., and Pridmore, C.L., 2002, Geologic map of the Monterey 

30' × 60' quadrangle and adjacent areas, California: California Geological Survey Regional 

Geologic Map Series, scale 1:100,000, available at http://www.quake.ca.gov/gmaps/RGM/

monterey/monterey.html.

Weber, G.E., 1994, Late Pleistocene slip rates on the San Gregorio fault zone at Point Año Nuevo, 

San Mateo County, California, in Lettis, W.R., ed., Field trip guidebook—Transpressional 

deformation in the San Francisco Bay region: Friends of the Pleistocene, Pacific Southwest Cell, 

Guidebook, 1994 fall field trip, Sept. 30–Oct. 2, 1994, 101 p.

Weber, G.E., and Lajoie, K.R., 1980, Map of Quaternary faulting along the San Gregorio fault zone, 

San Mateo and Santa Cruz Counties, California: U.S. Geological Survey Open-File Report 

80–907, 3 sheets, scale 1:24,000, available at http://pubs.er.usgs.gov/publication/ofr80907.

37°

36°40'

122°20' 122°

SANTA CRUZ

MONTEREY

MOSS 

LANDING

PIGEON

POINT

Limit of California’s

State Waters

Area of

Map

CALIF.

MAP LOCATION

0 5 10 Kilometers

0 5 10Nautical Miles

121°40'

Monterey

Bay

Seismic-Reflection Profiles, Offshore of Scott Creek Map Area, California

by

Samuel Y. Johnson, Stephen R. Hartwell, and Ray W. Sliter

2015

Two-way travel time, in seconds

0

0.1

0.2

SOUTHWEST

0.3

Figure 1. USGS high-resolution minisparker seismic-reflection profile MBS–33 (collected in 2009 on survey S–N1–09–MB), which crosses shelf west of mouth of Waddell Creek; see trackline map for location. Profile 

highlights faulted and folded strata beneath continental shelf, west of San Gregorio Fault Zone. Dashed red lines show faults. Magenta symbols show fold axes (diverging arrows, anticline; converging arrows, syncline). Blue 

shading shows inferred uppermost Pleistocene and Holocene strata, deposited since last sea-level lowstand about 21,000 years ago. Underlying reflectors image deformed Neogene strata. Dashed purple line shows 

unconformity. Dashed green lines highlight some continuous reflections that reveal structure (not distinctive stratigraphic markers). Dashed yellow line is seafloor multiple (echo of seafloor reflector). Purple triangle shows 

location of California’s State Waters limit (yellow line on trackline map).

1 km

VERTICAL EXAGGERATION ~ 12.5

bedrock (Monterey Formation)

NORTHEAST

160

0 

Approximate depth, in meters

80

240

Figure 2. USGS high-resolution minisparker seismic-reflection profile MBS–30 (collected in 2009 on survey S–N1–09–MB), which crosses shelf west of mouth of Scott Creek; see trackline map for location. Profile 

highlights faulted and folded strata beneath continental shelf, including San Gregorio Fault Zone. Dashed red lines show faults. Magenta symbols show fold axes (diverging arrows, anticline; converging arrows, 

syncline). Blue and pink shading shows two units of inferred uppermost Pleistocene and Holocene strata, deposited in last about 30,000 years during final stages of sea-level fall and subsequent sea-level rise. 

Underlying reflectors are of inferred Neogene age. Dashed green lines highlight some continuous reflections that reveal structure (not distinctive stratigraphic markers). Dashed purple lines show unconformities. 

Dashed yellow line is seafloor multiple (echo of seafloor reflector). Purple triangle shows location of California’s State Waters limit (yellow line on trackline map).

1 km

VERTICAL EXAGGERATION ~ 12.5

Two-way travel time, in seconds

0

0.1

0.2

SOUTHWEST

0.3

NORTHEAST

160

0 

Approximate depth, in meters

80

240

clinoforms

San Gregorio Fault Zone

Fig. 8

Coastways

 Fault

Frijoles

 Fault

Two-way travel time, in seconds

0

0.1

0.2

SOUTHWEST

0.3

Figure 3. USGS high-resolution minisparker seismic-reflection profile MBS–45 (collected in 2009 on survey S–N1–09–MB), which crosses shelf southwest of mouth of Waddell Creek; see trackline map for location. Profile 

highlights faulted and folded strata beneath continental shelf, including San Gregorio Fault Zone. Dashed red lines show faults. Magenta symbols show fold axes (diverging arrows, anticline; converging arrows, syncline). 

Blue shading shows inferred uppermost Pleistocene and Holocene strata, deposited since last sea-level lowstand about 21,000 years ago. Underlying reflectors are of inferred Neogene age. Dashed purple line shows 

unconformity. Dashed green lines highlight some continuous reflections that reveal structure (not distinctive stratigraphic markers). Dashed yellow line is seafloor multiple (echo of seafloor reflector). Purple triangle shows 

location of California’s State Waters limit (yellow line on trackline map).

1 km

VERTICAL EXAGGERATION ~ 12.5

San Gregorio

 Fault Zone

NORTHEAST

160

0 

Approximate depth, in meters

80

240

Fig. 10

Coastways 

 Fault Frijoles

 Fault

Figure 4. USGS high-resolution minisparker seismic-reflection profile MBS–25 (collected in 2009 on survey S–N1–09–MB), which crosses shelf west of Davenport; see trackline map for location. Profile highlights faulted and 

folded strata beneath continental shelf, including San Gregorio Fault Zone. Dashed red lines show faults. Magenta symbols show fold axes (diverging arrows, anticlines; converging arrows, synclines). Blue and pink shading 

shows inferred uppermost Pleistocene and Holocene strata, deposited in last about 30,000 years during final stages of sea-level fall and subsequent sea-level rise. Underlying reflectors are of inferred Neogene age. Dashed 

green lines highlight some continuous reflections that reveal structure (not distinctive stratigraphic markers). Dashed purple lines shows unconformities. Dashed yellow line is seafloor multiple (echo of seafloor reflector). 

Purple triangle shows location of California’s State Waters limit (yellow line on trackline map).

1 km

VERTICAL EXAGGERATION ~ 12.5

Two-way travel time, in seconds

0

0.1

0.2

SOUTHWEST

0.3

NORTHEAST

160

0 

Approximate depth, in meters

80

240

San Gregorio Fault Zone

clinoforms

Coastways 

 Fault Frijoles

 Fault

bedrock (Santa 

Cruz Mudstone) 

Two-way travel time, in seconds

0

1

2

Figure 5. Migrated, deep-penetration industry, 2-D, multichannel air-gun seismic-reflection profile WS82–600 (collected in 1982 on survey W–34–82–MB; from USGS National Archive of Marine Seismic 

Surveys [U.S. Geological Survey, 2009]), which crosses shelf west-southwest of mouth of Scott Creek; see trackline map for location. Note that vertical scale and exaggeration are significantly different 

than that of high-resolution seismic-reflection profiles shown in figures 1, 2, 3, 4, 6, 7, 9, and 10. Dashed yellow lines show faults. Magenta symbols show fold axes (diverging arrows, anticlines; 

converging arrows, synclines). Profile highlights faults and folds beneath continental shelf west of nearby San Gregorio Fault Zone, including Ascension Fault Zone. Purple triangle shows location of 

California’s State Waters limit (yellow line on trackline map). 

NORTHEAST

1 km

SOUTHWEST VERTICAL EXAGGERATION ~ 2

Fig. 10

0 

Approximate depth, in kilometers

1

> 2

Ascension Fault

 Zone

Figure 6. USGS high-resolution minisparker seismic-reflection profile MBS–48 (collected in 2009 on survey S–N1–09–MB), which crosses shelf west-northwest of mouth of Scott Creek; see trackline map for location. Profile 

highlights faulted and folded strata beneath continental shelf, including San Gregorio Fault Zone. Dashed red lines show faults. Magenta symbols show fold axes (diverging arrows, anticlines; converging arrows, synclines). 

Blue shading shows inferred uppermost Pleistocene and Holocene strata, deposited since last sea-level lowstand about 21,000 years ago. Underlying reflectors are of inferred Neogene age. Dashed green lines highlight 

some continuous reflections that reveal structure (not distinctive stratigraphic markers). Dashed yellow line is seafloor multiple (echo of seafloor reflector). Purple triangle shows location of California’s State Waters limit 

(yellow line on trackline map).

Two-way travel time, in seconds

0

0.1

0.2

SOUTHWEST

0.3

1 km

VERTICAL EXAGGERATION ~ 12.5 NORTHEAST

160

0 

Approximate depth, in meters

80

240

San Gregorio 

 Fault Zone

Fig. 10

Coastways

 Fault

Frijoles

 Fault

Figure 7. USGS high-resolution minisparker seismic-reflection profile MBS–22 (collected in 2009 on survey S–N1–09–MB), which crosses shelf south-southwest of Davenport; see trackline map for location. 

Profile highlights faulted and folded strata beneath continental shelf, including San Gregorio Fault Zone. Dashed red lines show faults. Magenta symbols show anticline axes. Blue and pink shading shows 

inferred uppermost Pleistocene and Holocene strata, deposited in last about 30,000 years during final stages of sea-level fall and subsequent sea-level rise. Underlying reflectors are of inferred Neogene age. 

Dashed green lines highlight some continuous reflections that reveal structure (not distinctive stratigraphic markers). Dashed yellow line is seafloor multiple (echo of seafloor reflector). Purple triangle shows 

location of California’s State Waters limit (yellow line on trackline map).

1 km

VERTICAL EXAGGERATION ~ 12.5

Two-way travel time, in seconds

0

0.1

0.2

SOUTHWEST

0.3

NORTHEAST

160

0 

Approximate depth, in meters

80

240

clinoforms

San Gregorio Fault Zone

Coastways

 Fault Frijoles

 Fault

Figure 8. Migrated, deep-penetration industry, 2-D, multichannel air-gun seismic-reflection profile WSF–028 (collected in 1976 on survey W–14–76–SF; from USGS National Archive of Marine Seismic 

Surveys [U.S. Geological Survey, 2009]), which crosses shelf west-southwest of Davenport; see trackline map for location. Note that vertical scale and exaggeration are significantly different than that 

of high-resolution profiles shown in figures 1, 2, 3, 4, 6, 7, 9, and 10. Dashed yellow lines show faults. Magenta symbol shows anticline axis. Profile highlights faults and fold beneath continental shelf 

west of San Gregorio Fault Zone, including Ascension Fault Zone. Purple triangle shows location of California’s State Waters limit (yellow line on trackline map). 

NORTHEAST

Two-way travel time, in seconds

0

1

2

1 km

SOUTHWEST VERTICAL EXAGGERATION ~ 2

San Gregorio

 Fault Zone

Fig. 2

0 

Approximate depth, in kilometers

1

> 2

Ascension 

Fault Zone

Figure 3. High-resolution minisparker profile MBS-51, collected by the USGS in 2009 (cruise S-N1-09-MB), highlighting faulted and folded strata west beneath continental shelf, including the San Gregorio Fault Zone. Dashed 

red lines show faults. Pink symbols show fold axes (diverging arrows for anticline, converging arrows for syncline). Blue shading shows inferred uppermost Pleistocene and Holocene strata, deposited since last sea-level 

lowstand about 21,000 years ago. Underlying reflectors are of inferred Neogene age. Dashed purple line shows unconformity. Dashed green lines highlight some continuous reflections that reveal structure (not distinctive 

stratigraphic markers). Dashed yellow line shows seafloor multiple (echo of seafloor reflector). 

NORTHEAST

160

0 

Approximate depth, in meters

80

240

Two-way travel time, in seconds

0

0.1

0.2

SOUTHWEST

0.3

1 km

VERTICAL EXAGGERATION ~ 12.5

Figure 9. USGS high-resolution minisparker seismic-reflection profile MBS–51 (collected in 2009 on survey S–N1–09–MB), which crosses shelf west of mouth of Scott Creek; see trackline map for location. Profile highlights 

faulted and folded strata beneath continental shelf, including San Gregorio Fault Zone. Dashed red lines show faults. Magenta symbols show fold axes (diverging arrows, anticlines; converging arrows, syncline). Blue 

shading shows inferred uppermost Pleistocene and Holocene strata, deposited since last sea-level lowstand about 21,000 years ago. Underlying reflectors are of inferred Neogene age. Dashed purple lines show unconformities. Dashed green lines highlight some continuous reflections that reveal structure (not distinctive stratigraphic markers). Dashed yellow line is seafloor multiple (echo of seafloor reflector). Purple triangle shows location of 

California’s State Waters limit (yellow line on trackline map).

San Gregorio Fault Zone

Fig. 10

Coastways

 Fault

Frijoles

 Fault

bedrock (Santa 

Cruz Mudstone) 

Figure 10. USGS high-resolution minisparker seismic-reflection profile MBS–28A (collected in 2009 on survey S–N1–09–MB), which crosses shelf roughly parallel to coastline, between mouths of Waddell and 

Scott Creeks; see trackline map for location. Profile highlights folded strata beneath continental shelf, west of San Gregorio Fault Zone. Magenta symbols show fold axes (diverging arrows, anticline; 

converging arrows, synclines). Blue shading shows inferred uppermost Pleistocene and Holocene strata, deposited since last sea-level lowstand about 21,000 years ago. Underlying reflectors are of inferred 

Neogene age. Dashed green lines highlight some continuous reflections that reveal structure (not distinctive stratigraphic markers). Dashed yellow line is seafloor multiple (echo of seafloor reflector).

Two-way travel time, in seconds

0

0.1

0.2

NORTHWEST

0.3

1 km

VERTICAL EXAGGERATION ~ 12.5 SOUTHEAST

160

0 

Approximate depth, in meters

80

240

Fig. 3

Fig. 6

Fig. 5

Fig. 9

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, 2015

MAGNETIC NORTH

13 / ° 1 2

TRUE NORTH

GIS database and digital cartography by Peter Dartnell 

and Stephen R. Hartwell 

Manuscript approved for publication September 30, 2015

Onshore elevation data from California Coastal 

Conservancy (available from National Oceanic and 

Atmospheric Administration [NOAA] Coastal Service 

Center’s Digital Coast at http://www.csc.noaa.gov/

digitalcoast/data/coastallidar/) and from U.S. Geological 

Survey’s National Elevation Dataset (available at 

http://ned.usgs.gov/). California's State Waters limit from 

NOAA Office of Coast Survey

Universal Transverse Mercator projection, Zone 10N

NOT INTENDED FOR NAVIGATIONAL USE

122°20' 122°15'

37°05'

37°

122°20' 122°15'

37°

37°05'

Waddell

Creek

Scott

Creek

Davenport

Fig. 1

Fig. 10

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9

Trackline Map

EXPLANATION

Tracklines of select seismic-reflection 

surveys—Thick lines show locations 

of profile lines depicted in figures; 

thin lines show full extent of surveys

Survey S–N1–09–MB (USGS)

Survey W–34–82–MB (WesternGeco)

Survey W–14–76–SF (WesternGeco)

3-nautical-mile limit of California’s State 

Waters

Area of “no data”—Areas near shoreline 

not mapped owing to insufficient 

high-resolution seafloor mapping 

data; areas beyond 3-nautical-mile 

limit of California’s State Waters were 

not mapped as part of California 

Seafloor Mapping Program

Figure 8

Figure 1

Figure 5

Open-File Report 2015–1191

Sheet 8 of 10

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey