Los Angeles, Calif., is one of the world’s largest metropolitan areas with a population of about 15 million people. The urban areas mostly cover the coastal plains and lie within the inland valleys. The intervening and adjacent mountains are generally too rugged for much urban development. This is in large part because the mountains are #8220;young,” meaning they are still building (and eroding) in this seismically active (earthquake prone) region.
Earthquake faults commonly lie between the mountains and the lowlands. The San Andreas fault, the largest fault in California, likewise divides the very rugged San Gabriel Mountains from the low-relief Mojave Desert, thus forming a straight topographic boundary between the top center and lower right corner of the image. We present this perspective image from NASA’s Shuttle Radar Topography Mission (SRTM) with a graphic overlay that maps faults that have been active in Late Quaternary times (white lines). The fault database was provided by the U.S. Geological Survey.
The Landsat image used here was acquired on May 4, 2001, about seven weeks before the summer solstice, so natural terrain shading is not particularly strong. It is also not especially apparent given a view direction (northwest) nearly parallel to the sun illumination (shadows generally fall on the backsides of mountains). Consequently, topographic shading derived from the SRTM elevation model was added to the Landsat image, with a false sun illumination from the left (southwest). This synthetic shading enhances the appearance of the topography.
View width 134 kilometers (83 miles); view distance 150 kilometers (93 miles)
Location: 34.3 degrees North latitude, 118.4 degrees West longitude
Orientation: View west-northwest, 1.8 X vertical exaggeration
Image Data: Landsat Bands 3, 2+4, 1 as red, green, blue, respectively
Original Data Resolution: SRTM 1 arcsecond (30 meters or 98 feet), Landsat 30 meters (98 feet)
Graphic Data: Earthquake faults active in Late Quaternary times Date Acquired: February 2000 (SRTM), May 4, 2001 (Landsat).