Three-dimensional P-velocity structure in the region of the MS = 6.9 Irpinia, Italy, normal faulting earthquake

摘要: Abstract We have calculated the three-dimensional velocity structure in epicentral region of 1980 Irpinia (southern Italy) earthquake using Thurber's inversion technique for hypocenter and parameters. Particular care was given to evaluation resolution models, because poor reading accuracy analog stations operating at that time. analyzed averaging vector each node model, order estimate degree smearing within final tomographic image. This approach is suitable determining best parametrization use (i.e. minimum grid spacing) evaluating where computed velocities are meaningful. The results show main rupture occurred along a sharp NW-SE trending contrast, which probably reflects crustal discontinuity. variations fault, due lithological heterogeneities, account complex character this earthquake. Based on distribution depth, secondary started about 40 s after mainshock interpreted be result reactivation an old thrust as normal fault.