Estimating slip rates and recurrence intervals for strong earthquakes along an intracontinental fault: example of the Pambak–Sevan–Sunik fault (Armenia) Herve ´ Philip a, * , Ara Avagyan a , Arcadi Karakhanian b , Jean-Franc ßois Ritz a , Samira Rebai a a Laboratoire de Ge ´ophysique, Tectonique et Se ´dimentologie, UMR 5573, Universite ´ Montpellier II, Place Euge `ne Bataillon, 34095 Montpellier Ce ´dex 05, France b ‘‘Georisk’’ Scientific Research Company, 24a Bagramyan, Yerevan 375019, Armenia Received 25 February 2000; accepted 24 October 2001 Abstract North of the Arabian plate, active tectonics is characterised by both N – S compression and E – W extension associated with strike-slip faults. The Pambak – Sevan – Sunik fault (PSSF) zone in Armenia is one of the major active structures of the region. The fault is comprised of four main segments and it displays morphological evidence for dextral movement during the Holocene. However, no large earthquake (M > 7) has occurred in the northern or central parts of the fault during the last 2000 years. We undertook a geomorphological and paleoseismological investigation along the Pambak– Sevan– Sunik fault with the aim of estimating the long-term slip rate and recurrence interval of strong earthquakes. Trenches were excavated at three sites. Detailed studies of trench cross sections and dating (radiocarbon and ceramics) show three faulting events that occurred in the Vanadzor– Artanih segment (Fioletovo and Semionovka areas), whereas a single event took place in the Artanish – Sunik segment (Khonarhasar area). In both areas, we estimated the average slip rate using (i) the offset of rivers along the Vanadzor– Artanish segment (2.24 ± 0.96 mm/year over an interval of 120– 300 ka), and (ii) the offset of volcanic cones along the Artanish – Sunik segment (0.53 ± 0.04 mm/year over an interval of 1.4 Ma). These results suggest that a greater slip rate characterises the Vanadzor –Artanish segment (Fioletovo site) from the Artanish –Sunik (Khonarhasar site) segment. Division of the Pambak – Sevan – Sunik fault zone into two main branches, east of the Artanish peninsula (Sevan Lake) could explain the difference in slip rate. In addition to its segmented seismic behaviour, the Pambak – Sevan – Sunik fault is a well-documented example of a fault that generates strong earthquakes with long recurrence time intervals (about 3000 – 4000 years). D 2001 Elsevier Science B.V. All rights reserved. Keywords: Active tectonics; Paleoseismology; Earthquakes; Caucasus; Armenia 1. Introduction The Great and Lesser Caucasus Mountain ranges and the highly elevated region of the Armenian up- land constitute a segment of the Alpine fold belt. 0040-1951/01/$ - see front matter D 2001 Elsevier Science B.V. All rights reserved. PII:S0040-1951(01)00258-X * Corresponding author. E-mail address: philip@dstu.univ-montp2.fr (H. Philip). www.elsevier.com/locate/tecto Tectonophysics 343 (2001) 205 – 232