California Seafloor Mapping Program data collection

Science Center Objects

Here we describe the data collection methods and techniques of the California Seaflor Mapping Program: mapping, video and photography ground-truthing, and seismic profiling data collection.

Mapping

Sonar mapping of the California State Waters has been completed for the California mainland and is partially complete around California's offshore islands. Please check the Progress page for the latest information.

State-of-the-art multibeam and bathymetric sidescan sonar systems are collecting high-resolution bathymetry and acoustic backscatter data. These data are the foundation on which most of the groundtruthing and derivative products are based.

Image show the shape of the seafloor based on depth, one looking at an angle and one in map view or overhead.

Figures 1 and 2 [click image for larger version]

Image shows a sonar representation of the seafloor, photo shows man sitting at a computer and keyboard.

Figures 3 and 4 [click image for larger version]

Bathymetry data (figures 1 and 2) display the shape of the seafloor including rough terrain (possibly rock outcrops), smooth terrain (possibly sedimented), canyons, and anthropogenic features. Acoustic backscatter data (figure 3) show the intensity of the acoustic pulse off the seafloor and back to the ship. Brighter tones indicate a strong intensity (possibly harder seafloor), while darker ones indicate a weaker intensity (possibly softer seafloor). Many seafloor physical parameters influence backscatter intensity but these data are helpful in determining the distribution of seafloor geology (i.e. rock, sand, mud).

Typically, these data are processed on the ship (figure 4) allowing for almost real-time quality control and filling of data gaps.

Video and photography ground-truthing

Video and photography ground-truthing of the California State Waters has also been completed for California's mainland waters. Please check the Progress page for the latest information, and visit the CSMP Video and Photograph Portal, which hosts 550 kilometers (km) of trackline video and 87,000 photographs.

Video, photographs, and real-time observations of seafloor geology and biological cover recorded from a towed camera sled help develop and verify derivative products based on the swath bathymetry and backscatter data.

These data are collected using a camera sled towed about one meter over the seafloor at speeds around one nautical mile/hour. The sled is approximately one-by-one-by-two (1x1x2) meters in size and houses two digital video cameras (one pointing at an angle and one pointing vertically), a 7-megapixel still camera, a high-definition video camera, and paired lasers used for scale. Figure 5 shows the deployment of the camera sled while figure 6 shows its recovery.

A large metal frame holding instruments is lowered off a ship and into the water with a crane and cables.

Figure 5 [click image for larger version]

People wearing safety gear lean over the gunwale of a ship to help guide a large metal frame holding instruments.

Figure 6 [click image for larger version]

Figures 7 and 8 show examples of seafloor video and photographs collected within California State Waters. Figure 7 (top photo) is an example of a seafloor video showing boulders and cobbles, and red gorgonia. The green lights are the paired lasers used to scale features on the seafloor. Figure 8 (bottom photo) is an example of a seafloor photograph showing an almost vertical rock face covered with strawberry anemones.

The video is fed up to TV monitors on the ship and real-time observations are recorded into a database using programmable key-pads. Over 90 possible geological and biological observations can be recorded during any observation period, which occur once per minute for a length of 10 seconds. Geologic observations include composition (i.e. rock, sand), complexity, and local slope. Biological observations include biological complexity, cover, and a variety of invertebrate species, and demersal fish. The observations can quickly be added to a GIS and compared with the swath bathymetry and backscatter data.

The towed camera sled video, photographs, and real-time observations are being used to collect presence/absence data of macro-invertebrates and their associated sediment types, depth, and latitude. At the National Marine Fisheries Service (NMFS) this information is entered into programs like PRIMER and R to determine habitat associated community structures and to develop multivariate models using logistic regression to predict the distribution of key species (including some deep-sea coral species). Coupling these results with a seafloor character map with spatial information on sediment type and depth, we hope to map the probability of occurrence of these important communities on a coast-wide scale. These maps will provide managers, policy makers, and the public with information that can be used in the conservation and management of sustainable marine resources. Current analysis is being done on data collected from the Santa Barbara Channel.

Two underwater photographs, one with two lasers aimed on a rocky seafloor, one shows rocky outcrop, flora, and fauna.

Figures 7 and 8 [click image for larger version]

Two ollage with one map of seafloor texture and two underwater photos with pointers to where they were taken, with location map.

Figures 9 and 10 [click image for larger version]

Figure 9 is an example of video observations over shaded relief bathymetry and corresponding seafloor photographs. The red dots on the map indicate observations of sediment (sand or mud), while blue dots indicate observations of hard ground (rock, boulder). The photograph taken at the hard ground observation (top) over a pinnacle shows an almost vertical rock wall. The photograph taken over a flat seafloor with a sediment observation (bottom) shows a seafloor covered in coarse sands.

Figure 10 is an example of video observations over backscatter imagery and corresponding seafloor photographs. The red dots on the map indicate observations of sediment (sand or mud), while blue dots indicate observations of hard ground (rock, boulder). The photograph taken at the hard ground observation (top) with high backscatter shows a seafloor of boulders and red gorgonia. The photograph taken at a sediment observation (bottom) with lower backscatter shows a seafloor covered in sands with white sea urchins and an octopus.

In specific areas of interest, video mosaics can be generated from videos that often show transition between sandy and rocky seafloor. The mosaic is generated from seafloor video using software developed at the University of New Hampshire. Figure 11 is an example of video mosaic showing a transition between sediment-covered seafloor and rock outcrop.

Mosaic of underwater photos showing the plants and seafloor surface.

Figure 11 [click image for larger version]

Seismic Profiling

Seismic profiling provides the information to understand subsurface geologic framework, including distribution and thickness of sediment, active faults and folds, submarine landslides, and other geologic features. The CSMP effort is using high-resolution, single-channel seismic profiles (e.g., Sliter and others, 20082009, and 2013) as well as archived multichannel seismic-reflection profiles from the USGS National Archive of Marine Seismic Surveys (NAMSS). Since CSMP began in 2007, USGS has collected new high-resolution profiles at approximately 1 Kilometers line spacing for about 65 percent of California's mainland State Waters.  USGS has also compiled maps showing publicly available, pre-2009, seismic-reflection data for the entire state on a block-by-block basis at the USGS California State Waters Quads (map blocks) website.

Figure 12 shows an example of a recently collected high-resolution seismic-reflection profile collected by the USGS offshore of Point Sal. The profile shows a cross section of the earths crust down to about 240 meters. The dashed red lines show the Hosgri Fault Zone, part of a strike-slip fault system that extends for about 400 kilometers along the California coast from Point Arguello to Bolinas. The thin magenta lines show layers in sedimentary deposits that are flat northeast of the fault zone and folded southwest of the zone. The yellow layer at the top of the profile consists of unconsolidated sediment, about 17 meters thick, deposited in approximately the last 20,000 years after the last sea-level lowstand. The blue line is the seafloor "multiple," an echo of the seafloor.

Figure 13 shows an example of a deep-penetration multichannel seismic reflection profile collected offshore of San Mateo County, from the USGS National Archive of Marine Seismic Surveys (NAMSS). The profile shows a cross section of the earth's crust from the surface down to a depth of about 3 kilometers. The layers show sedimentary deposits that have been variably folded and truncated, deformation associated with the San Gregorio fault zone (faults shown by yellow lines). This data was collected in the 1970's when offshore California was considered a frontier petroleum province.

A cross-section of earth's crust reveals the layered sediment and features of earthquake faults.

Figure 12 [click image for larger version]

A cross-section of earth's crust reveals the layered sediment and features of earthquake faults.

Figure 13 [click image for larger version]