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$6 R~ll, ~2, E~I3, ~4, ~5, 1---1 6, ~.7, ..~’8, ..~" 9, l.~’10, ...~11, I]]TI1 12. Fig. 2. Iranian major tectono-sedlmentary units illustrating an inhomogeneous collision region between Arabla and Eurasia (el. Fig. 3). I. Stable areas: Arabian Precambrlan shelf in the ~/ and Turanlan Hercynlan platform in the NE. The low dipping, relatively flat lying beds south and southwest of the Persian Gulf comprise the Arabian shelf over the buried Precambrian stable shield. 2. Neogene-Quaternary foredeeps, transitional from unfolded forelands to marginal fold zones, with strong late-Alpine subsidence. ZF: Zagros foredeep in the ~; KDF: Kopeh Dagh foredeep in the NE. 3. Main sector of the marginal active fold-thrust belt peripheral to the stable areas (Zagros and High Zagros-HZ- in the ~/, and Kopeh Dagh in the NE). ~. Zabol-Baluch (east Iran) and Makran (southeast Iran) post-ophiolite flysch belts. Late Tertiary seaward accretion and landward underthrusting seem to be responsible for the formation of the present Makran ranges. 5. Alborz Mountains, bordering the southern part of the Caspian Sea. 6. Central Iranian Plateau (Central Iran) lying between the two marginal active fold-thrust belts. In northwestern part of the country, Central Iran wedges out and Joins the Transcaucasian early Hercynian median mass (TC), the Sevan-Akera ophlollte belt (SV), and Little Caucasus [A: Armenian (Miskhan-Zangezurian) late Hercynian belt, with a possible continuation tc the Iranian Talesh Mountains (T) along the western part of the Caspian Sea; AA: the BERBERIAN
Araxlan-Azarbaijan zone of Caledonian consolidation, with the Vedi (V) ophiolite belt]. SS: SanandaJ-Slrjan belt, a narrow Intraoratonlc mobile belt (during Paleozolc ) and active continental margin (Mesozoic), forming the southwestern margin of Central Iran in contact with the Main Zagros reverse fault (MZRF). The belt bears the imprints of several major crustal upheavals (severe tectonism, magmatism and metamorphism). The Central Iranian tectonle unit widens eastwards and Joins Central Afghanistan in the east. . Late Cretaeeoua High Zagroa-Oman ophiollteradiolarite (75 Ms) and the Central Iranian ophlollte-melange belta (65 Ma), with outcrops indicated in black. The southeastern parts of the Middle Cretaceous (110 Ma) Sevan-Akera and Vedi ophlolites of the Little Caucasus are sho~m in the NW of the country. The extensive belts of ophlolltes mark the original zone of eonvergenoe between different blocks. The position of ophiolites are modified by post emplacement convergent movements. 8. Major faciea dividing basement faults, bordering different tectono-sedlmentary units. Contrasting tectono-sedimentary regimes, belts of ophiolltes and associated oceanlo sediments, together with paleogeographic contrasts along the Main Zagros (MZRF) and the High Zagros (HZRF) reverse faults in southwest,, the South Kopeh Dagh fault (SKDF) in northeaat, indicate existence of old geosutures along these lines. The Chapedony and Posht-e-Badam faults delineate the possible Preeambrian island-arc in eastern Central Iran. SJMF: South Jaz Murian Fault in SE. 9. Late Alpine fold axes. 10. Active subduetion zone of Makran in the Gulf of Oman. 11. Provlnee boundary. 12. Areas with oeeanle crust (South Caspian Depression and Gulf of Oman). Lambert Conformal Conic Projeetlon. Based on data from Gzovsky et al. [1960], Abu-Bakr and Jackson [196~], Stoeklln [1968a, 1977], Adamla [1968], 3borshchlkov et al. [192], Brown [1972], Tectonle Map of Caucasus [1974], Barberlan [1976a and el, Whlte and Klltgord [1976], Huber [1978], and Shikallbeily and Grigoriants [1980] after modifleatlon and correction. [Berberian 1979a]. A glance at the past geological history of the active mountain-bordering reverse faults shows a history of repeated movements of different character along some of these deepseated sedimentation controlling faults. The Tabas earthquake of 1978.09.16 is an interesting case in point, indicating the activity of a multirole basement fault during different orogenic movements [see Berberian 1979a and 1981a for discussion]. ~ -Type Earthquakes (i.e., earthquakes along faults) Allen [1975] emphasized the importance of employing geological evidence of late Quaternary movement to determine the sites of future seismic slip. This is valid where the seismic faults are not covered by ductile sediments. However, in the Zagros (the active fold-thrust mountain belt of southern-southwestern Iron, northern Iraq, northern Syria and southern Asia-Minor; Fig. 2) the earthquakes can not generally be correlated with the known surface faults, because of the special salt-tectonics character of the region [Berberian and Tchalenko 1975, Berberian 1976c, Berberian and Papastamatiou 1978]. The apparent lack of agreement between earthquakes and surface faults in the Zagros may arise from two factors: deficiency of seismic data and lack of knowledge of the relation between the Precambrian metamorphosed basement at depth (where most earthquakes occur) and the top of the sedimentary cover, where the geological structures are observed. In the Zagros belt the metamorphosed Precambrian basement is covered by 8 to 14 kilometers of sedimentary rocks which were folded during late Miocene-Pleistocene time. A highly plastic salt layer (the Hormoz salt) [Stocklin 1968b] of late Precambrian age (Fig. 6), acts as a ’zone slippage’, disconnecting the sedimentary cover structures fromthose in the basement. Hovements along basement faults can cause earthquakes in the Zagros active fold-thrust belt without producing surface faulting in the overlying sedimentary cover, presumably due to the presence of the plastic Hormoz deposits [Berberian 1976c]. Usually the aftershock distribution of large magnitude earthquakes in the Zagros active foldthrust belt spreads out over 40 km [NEIS, ISC, Dewey and Grantz 1973, North 1973, 1974, Jackson and Fitch 1979]. It is unlikely that faulting of this dimension associated with large magnitude earthquake ’(Fig. 7) reactivates in the top sedimentary covet without surface faulting. Within the sedimentary cover are plastic layers other than the Hormoz salt (Fig. 6): Permian evaporltes (Nat member) of the Dalan Formation, Lower Triassic Dashtak evaporites, Lower Jurassic Adaiyah and Alan anhydrite, Upper Jurassic Gotnia and Hith anhydrite, Lower Eocene Kashkan-Sachun gypsum, Lower Miocene Kalhur gypsum and finally the Miocene salt-gypsum layers of the Gachsaran Formation (Lower Fats in Iraq and Kuwait) [James and Wynd 1965, Setudehnta 1972, Szabo and Kheradpir 1978]. Each of these incompetent evaporlte horizons, together with other semiductile beds (such as the Jurassic Neyrlz and the Eocene Pabdeh Formations), mechanically decouples the overlying structures from the underlying ones, behaving as zones of decollement. These tectonically incompetent units, characterized by extreme mobility, are responslble for remarkable structural changes and compllcatlons: synclines at the surface correspond to anticllnes at one ACTIVE FAULTING AND TECTONICS OF IRAN 57
Page 1 and 2: Reprinted from Zagros ¯ Hindu Kush
Page 3: Inset left: Dlstrlbutlon ofeplcentr
Page 7 and 8: GULF OF OMAN Fig. ~. Fault Hap of I
Page 9 and 10: 2. Segments of the High Zagros deep
Page 11 and 12: TABLE I. Cont. F~_U~LT # ~L~ME FT F
Page 13 and 14: 11Ambraseys 1974 24 A=braseys 1963
Page 15 and 16: ~ U.PRECAMBRIAN HORMOZ SALT TECTONI
Page 17 and 18: TABLE II - Seismic trends (buried h
Page 19 and 20: Indicating that the reglon ls asets
Page 21 and 22: |Taba s J J Khaf Sabzevar Kuh Banan
Page 23 and 24: CASPIAN SEA 0 200 km 1979 38’ AFG
Page 25 and 26: CASPIAN SEA GULF OF OMAN Fig. 12. E
Page 27 and 28: Dominance of 170 My or 210 My of An
Page 29 and 30: 1977, Sykes 1978] and the deformati
Page 31 and 32: the fact that the cruat consists of
Page 33 and 34: western Alpine system, In: Biju-Duv
Page 35 and 36: Nabavi, M.S., Selsmicity o£ Iran,
Page 37: Wowroo zi, Seismological and geolog

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