In both locations, upper-mantleīodies of high P velocity are observed extending from near the Moho to more than 200-km depth. This decollement allows upper crust to escape collision laterally and vertically, but forces the lower crust to form crustal roots, reaching maximum depths of 44 km (South Island) and 36 km (southern California). In both locations, a midcrustal decollement is observed that connects the plate-boundary fault to thrust faults farther south in the PAC. Away from the LARSE transects, the dip of the The LARSE transects, the SAF dips vertically to steeply northeastward toward the North American plate (NAM). Along the SIGHT transects, the AF appears to dip moderately southeastward (~50 deg.), toward the Pacific plate (PAC), but along The crustal structure surrounding the AF and SAF was investigated with active and passive seismic sources along transects known as South Island Geophysical Transect (SIGHT) and Los Angeles Region SeismicĮxperiment (LARSE), respectively. There are also notable differences, including the dips of the faults and their plate-tectonic histories. Both systems are transpressional, with similar right slip and convergence rates, similar onset ages (for the current traces), and similar total offsets. There are clear similarities in structure and tectonics between the Alpine Fault system (AF) of New Zealand’s South Island and the San Andreas Fault system (SAF) of southern California, USA.
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