Pacific Coastal & Marine Science Center
California Seafloor Mapping Program
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Sonar mapping of the California State Waters is currently underway. 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 ground-truthing and interpreted products are based.
Bathymetry data (Figure 2, Figure 3 ) display the shape of the sea floor including rough terrain (possibly rock outcrops), smooth terrain (possibly sedimented), canyons, and anthropogenic features. Acoustic backscatter data (Figure 4 ) show the intensity of the acoustic pulse off the sea floor and back to the ship. Brighter tones, indicate a strong intensity (possibly harder seafloor), while darker one 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 5 ) allowing for almost real-time quality control and filling of data gaps.
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Video and photography ground-truthing of the California State Waters is also currently underway. Please check the Progress page for the lastest information.
Video, photographs, and real-time observations of sea floor geology and biological cover recorded from a towed camera sled help develop and varify derivative products based on the swath bathymetry and backscatter data.
These data are collected using a camera sled towed about 1 m over the seafloor at speeds around 1 knot. The sled is approximately 1x1x2m in size and houses two digital video cameras, one oblique and one vertical, a 7-megapixel still camera, a high-definition video camera, and paired lasers used for scale. Figure 6 shows the deployment of the camera sled while Figure 7 shows its recovery.
Figure 8 and Figure 9 show examples of sea floor video and photographs collected within California State Waters. Figure 8 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 9 is an example of a seafloor photograph showing an almost vertical rock face covered with strawberry anenomes.
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 compostion (i.e. rock, sand), complexity, and local slope. Biological observations include biological complexity, cover, and a varity 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 deepsea 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 predicting the 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 work is being done on data collected from around the Santa Barbara area.
Figure 10 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 11 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 the video that often show transition between sandy and rocky sea floor. The mosaic is generated from sea floor video using software developed at the University of New Hampshire.
Figure 12 is an example of video mosaic showing a transition between sedimented seafloor and rock outcrop.
Seismic profiling provides the information to understand geologic framework, including distribution and thickness of sediment, active faults and folds, and other geologic features. The State Mapping Project is imaging the area beneath the seafloor using several types of sub-bottom profilers, which produce seismic reflection profiles of bedrock and sediment at depth.
The project is using archived multichannel seismic reflection profiles from the USGS National Archive of Marine Seismic Surveys as well as collecting new high resolution data. Figure 13 is a trackline map offshore the San Mateo Coast that shows both archived and recently collected seismic profiles. USGS has compiled maps showing publicly available seismic-reflection data for the entire state on a block-by-block basis at the USGS CMG State Waters Mapping KML’s website.
Figure 14 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. The profile shows a cross section of the earths crust from the surface down to a depth of about 3 km. 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
Figure 15 shows an example of a recently collected high-resolution seismic-reflectiona profile collected by the USGS offshore the San Mateo coast. The profile shows a cross section of the earths crust down to 150 m. The layers show sedimentary deposits that have been variably folded and truncated, deformation associated with the San Gregorio and San Pedro fault zones (faults shown by yellow lines). The blue highlighted area at the top of the profile shows the sandy layer deposited during the last ~15,000 years, after the last sea-level lowstand.