Nahavand (Firuzabad) Earthquake of 16 August 1958 Mw.6.6
During this earthquake sequence, about 170 villages were destroyed or damaged, more than 130 people were killed, and more than 200 people were injured in the Nahavand area. After the 13 December 1957 Farsinaj earthquake and its aftershocks, the 16 August 1958 Mw 6.6 earthquake, preceded by two strong and damaging shocks of 14 August 1958 [11:27 UTC, Ms 5.7; and 15:26 UTC, Ms 5.5] took place on the Zagros Main Recent fault to the southeast of the 1957 earthquake. The timing and overlap of the meizoseismal areas of the 1957 and 1958 earthquakes indicate temporal clustering and loading of the adjacent fault segments, with the earthquake sequence propagating to the southeast. The 1957 and the 1958 events were part of the earthquake sequence that began on 23 January 1909 Mw7.4 Silakhor earthquake along the Zagros Main Recent fault (Berberian and Yeats, 2001). Unfortunately, the meizoseismal areas of the three 1958 earthquakes, as well as the ground deformations associated with them, were not documented immediately afterward. Furthermore, teleseismic data with large location errors cannot be used to separate the areas of the three 1958 events. All the reports address the accumulated impacts of the damaging events as foreshocks and the mainshock (Montandon, 1957; Hagiwara and Naito, 1959; Rothe, 1969; Nabavi, 1972; Ambraseys and Moinfar, 1974; Tchalenko and Braud, 1974). Based on information provided by local villagers in 1971 (Tchalenko and Braud, 1974) and 1973 (Ambraseys and Moinfar, 1974), both authors reported three sets of surface faulting, as follows (two sets by the former and three sets by the latter):
- SE of Larehkuh [Cheshmeh Mahi to Givaki] in the SW: This is a NW–SE trending ground fracture of 15-km long with maximum vertical displacement of 2 m (southeastern side downthrown). The southeastern part of the reported faulting coincides with the Garrin fault segment, and the northwestern part of the reported fault is along the southeastern part of the Sahneh fault segment of the Zagros Main Recent fault.
- NE of Larehkuh [Firuzabad; Barreh Farakh to Kariz and Leylan] in the NE: On either side of Firuzabad, a 20-km-long NW–SE trending surface rupture with southwestern block downthrown by a few tens of centimeters was developed. This surface rupture coincides with the Nahavand segment of the Zagros Main Recent fault.
- SW of larehkuh [Dehkohneh–Kaladeh] in the SW: A NW–SE ground rupture about 8 km long with the northeast block downthrown. The ground rupture is located along the southeastern part of the Sahneh segment of the Main Recent fault (Figure 12.12).
It seems that the Nahavand-Kahriz, Garrin, and southern tip of the Sahneh segments of the Zagros Main Recent fault were reactivated during the 1958 three-earthquake sequence (Berberian, 2014).