Shortening and thickening of metropolitan Los Angeles measured and inferred by using geodesy

Geodetic observations using the Global Positioning System (GPS) and other t echniques record a high rate of north-south shortening in an east-southeast -trending, 5-40-km-wide belt in northern metropolitan Los Angeles, Californ ia. Downtown Los Angeles is observed to be converging upon the southern San Gabriel Mountains at 6 mm/yr. Aside from the elastic strain that will be r eleased during earthquakes rupturing the san Andreas and San Jacinto faults , east-west lengthening across northern metropolitan Los Angeles is minor, <2.5 mm/yr. Therefore north-south shortening is accommodated mainly by vert ical crustal thickening.