Fig. 6: High-frequency seismic radiation and rupture front migration: kinematic model.

a Section of the accelerograms (EW component) recorded at the along-fault stations displayed in (b). x- and y-scale show, respectively the time from OT and the distance from NPF-EAF junction point. The green line marks the NE propagation of the rupture along the EAF at times around 10 s from OT, and the blue dotted line shows the propagation (with a speed close to the S-wave velocity) of the radiation mostly from the junction between NPF and EAF at similar times, the red line shows the SW rupture propagation at about 30 s from OT; b map of the along-strike stations. The star and the square show respectively the earthquake epicenter and the NPF-EAF junction point. c Sketch of the rupture dynamics: during the first about 10 s, the rupture propagates along the NPF. Between about 10 s and 30 s from the OT, the rupture propagates NE and emits high-frequency radiation mostly at times 10–15 s from OT when it reaches the junction between NPF and EAF, where moreover large co-seismic slip and high rupture speed have been estimated. At later times, the rupture starts propagating southwestwards from the junction.