High-resolution sea-floor image offshore San Diego

Just a quick post today to show you one of the latest multibeam bathymetric images released by the US Geological Survey. Go to this page to view and download the large-format PDFs.

If you'd like to know more about the technical details of the concept, design, and acquisition of multibeam sonar data, check out resources here and here.

This one is definitely worth clicking on to see the high-res version. The densely populated onshore area to the right is San Diego, California. For a more regional context of southern California geologic provinces, check out this page. The San Andreas fault is 10s of km inland from this location, but subsidiary strike-slip faults dominate the tectonic fabric.

The major submarine canyon cutting into the narrow continental shelf is called La Jolla Canyon. The head of that canyon comes very close to the pier at Scripps Institute of Oceanography if any of you have been there. Note the transition from the deeply incised submarine canyon to a submarine channel system as you go into deeper water. Also note the meandering nature of the individual channel "threads" within the belt. This submarine channel eventually empties into the elongate San Diego Trough basin, which is off the image to the left and in even deeper water.

A paper that i'm a co-author on is coming out in Geology next month and deals with this canyon-channel system in more detail and its history over the last 40,000 years. I will post about that soon, so stay tuned.

The USGS page also has some great perspective views....here is the link again, check it out.

Americans moving to areas with greater seismic hazard

The lower map shows the population change from 1990 to 2000 for the lower 48 of the United States. The brown colors are areas of net loss and the purple areas of net gain. The upper map shows seismic hazards. Clearly, people are moving from the central United States, and area of low seismic hazard to other areas (especially in the Colorado Plateau and Basin and Range regions) that have higher seismic hazard. But why? More excitement in their life?

A great mapping website, called the National Atlas (nationalatlas.gov), allows you to make outrageous and spurious claims like this with very little effort. It's great fun.

For example you could see if there's a spatial correlation between mudpuppy distribution and number of aggravated assaults. Or, maybe the range of the Greater Bonneted Bat has a relationship with impact crater distribution!

Seriously though....this is pretty dang cool that the feds put this together. They have so many categories of information. And to be able to interactive show them on a map is just fantastic.

Here is just a sampling of what you can map:

• Agriculture
• crop type
• land usage
• livestock
• Biology
• amphibians (that's what a mudpuppy is, apparently)
• bat ranges
• butterflies
• invasive species
• ecoregions
• Climate
• average precipitation
• tornadoes
• sea-surface temperature
• Environment
• superfund sites (that one's a little scary)
• toxic release inventory
• water discharge permits
• GEOLOGY
• People
• crime
• unemployment
• population density
• median age
• energy consumption
• Transportation
• railways
• airports
• interstates

and so on....

Really an incredible resource. Have fun!