Arabia-Eurasia convergence is accommodated in the Zagros Mountains of southwestern Iran and in the seismic belts of the central Caspian, Alborz, and Kopeh Dagh of northern Iran. The Zagros is a NW-trending fold-and-thrust belt made up of a 6–15-km-thick sedimentary pile, which overlies the Precambrian metamorphic basement. During the Zagros orogeny, some of the Precambrian basement and Lower Paleozoic strata were exhumed from depth and are now exposed in the Golpayegan region in the northwestern part of the Zagros Mountains. The tectonic evolution of the Golpayegan region and the exhumation of the old rocks are interpreted as the product of three major sequential geotectonic events. (1) Major thrusts formed during shortening and exposure of the basement rocks in the Aligudarz block. The rock units are strongly imbricated and sheared, which suggest a high amount of cumulative shortening in the northern Zagros. (2) NE-SW–trending extensional faults (e.g., Eastern Mute, Western Mute, and Mahallat faults) formed during lateral extensional movement after middle Miocene time. In this event, a set of NE-SW–trending horsts and grabens was formed. In the horsts (e.g., Hassan-Robat, Mute, and Mahallat horsts), the Precambrian basement rocks and Lower Paleozoic strata are exposed. (3) Strike-slip movements began that remain active today. Strike-slip motions are well documented for the late Pliocene–Quaternary period. In the Golpayegan region, the Shazand and Dehagh faults cut through the NE-trending normal faults and through Quaternary deposits. Drainages are displaced by ~4 km of dextral movement along the Shazand fault and near the city of Golpayegan.

ABSTRACT We present the first critical examination of the > 1300 yr history of the Borujerd old congregational mosque by means of scrutinizing ancient historical chronicles, archaeology, architecture, historical and modern seismicity, geology, and regional active faults. Our study resulted in recognition of at least four major phases of destruction, rebuilding, and renovations of the megastructure located 4 km to the northeast of the Zagros Main Recent fault in western Iran. The grand structure shows significant paleo-architectural and archaeological evidence of destruction and damage. Although some damage events, recorded in seven phases since the seventh century C.E., could have been due to the poor construction of early periods and their decay, there is strong evidence of at least one extensive, simultaneous, and abrupt destruction and damage pattern of mosque III (ca. post–1090/pre–1139 C.E.) in the early fourteenth century. We suggest that the poorly known 1316 C.E. strong earthquake (which destroyed more than 20 villages in the general area, with erroneous epicentral location in the historical seismic catalogues) was possibly responsible for the simultaneous sudden collapse of the Borujerd congregational mosque lofty dome chamber and its tall free-standing minaret; we infer that this earthquake occurred with intensity > VIII + (modified Mercalli intensity scale) conceivably along a seismic gap zone of the Zagros Main Recent fault. No pre–1316 C.E. monument exists in the epicentral region, and no strong earthquake has occurred along that segment of the Zāgros Main Recent fault for the last seven centuries. Retrospectively, apparent indigenous paleo-architectural renovations were utilized during construction of the new congregational mosque (mosque IV: ca. post–1405/pre–1447 C.E.) to enhance the coherency and elasticity of the rigid brick structure to withstand future earthquake shear stress. The hazard-reducing efforts included: (1) retrofitting the surviving load-bearing structural elements; (2) avoiding grandeur and majesty and implementing simplicity by reducing the size, height, and shape of the dome chamber; (3) avoiding free-standing minarets; (4) minimizing the size and reducing the light/ventilation openings; and (5) utilizing several levels of timber bracings to neutralize earthquake strong ground motion. Our research reveals that the return period of large-magnitude earthquakes along the two major segments of the fault is in the range of 1000 and 2000 yr, thus making historical earthquakes unrecognizable through routine historical research. It also shows how the use of archaeoseismology and paleo-architectural investigations on deformed monuments may improve our knowledge of long-term seismicity and seismic hazards of a region. This kind of study permits us to hypothesize the occurrence of strong earthquakes in an area for which historical seismicity does not show significant earthquakes. Finally, based on the described historic seismic damage and destruction, the regional national monuments should be properly retrofitted to withstand future earthquake hazards.

Abstract New structural, sedimentological, petrological and palaeomagnetic data collected in the region of Nakhlak–Anarak provide important constraints on the Cimmerian evolution of Central Iran. The Olenekian–Upper Ladinian succession of Nakhlak was deposited in a forearc setting, and records the exhumation and erosion of an orogenic wedge, possibly located in the present-day Anarak region. The Triassic succession was deformed after Ladinian times and shows south-vergent folds and thrusts unconformably covered by Upper Cretaceous limestones following the Late Jurassic Neo-Cimmerian deformation. Palaeomagnetic data obtained in the Olenekian succession suggest a palaeoposition of the region close to Eurasia at a latitude around 20°N. In addition, the palaeopoles do not support large anticlockwise rotations around vertical axes for central Iran with respect to Eurasia since the Middle Triassic, as previously suggested. The Anarak Metamorphic Complex (AMC) includes blueschist-facies metabasites associated with discontinuous slivers of serpentinized ultramafic rocks and Carboniferous greenschist-facies ‘Variscan’ metamorphic rocks, including widespread metacarbonates. The AMC was formed, at least partially, in the Triassic. Its erosion is recorded by the Middle Triassic Bāqoroq Formation at Nakhlak, which consists of conglomerates and sandstones rich in metamorphic detritus. The AMC was repeatedly deformed during post-Triassic times, giving origin to a complex structural setting characterized by strong tectonic fragmentation of previously formed tectonic units. Based on these data, we suggest that the Nakhlak–Anarak units represent an arc–trench system developed during the Eo-Cimmerian orogenic cycle. Different tectonic scenarios that can account for the evolution of the region and for the occurrence of this orogenic wedge in its present position within Central Iran are critically discussed, as well as its relationships with a presumed ‘Variscan’ metamorphic event.

ABSTRACT This is an in-depth review and analysis of the long and untold history of development of earth science, geological thinking, research, and exploration on the Iranian Plateau within its historical, political, and socioeconomic context. Widespread mineral resources and ancient civilization helped in exploration, excavation, smelting, and usage of different metals, precious stones, and minerals since the Neolithic Period. Extant ancient Avestan and Middle Iranian Pahlavi Zoroastrian texts, as well as the classic Greek and Roman scholars, clearly demonstrate the Iranian geological activity through the Median (ca. 615 BCE), Achaemenid (550–330 BCE), Parthian (250 BCE–224 CE), and Sassanid (224–642 CE) Dynasties, interrupted by disrupting periods of socioeconomic and political problems, followed by foreign invasions and devastation in 330 BCE–250 CE and 637–652 CE, when the Iranians could no longer make scientific advancements. Long after the invasion of Alexander III of Macedon (330 BCE), scientific activity culminated in the establishment of the academies of Gundishāpur, Ctesiphon, and Resaina, the three higher educational centers of the Sassanid Dynasty that focused on comprehensive observation, painstaking research, and advanced education during the sixth and seventh centuries CE. Careful observation, research, and experiment by brilliant and genius scholars such as Karaji, Biruni, and Avicenna took place during a period of great activity and growth in science, engineering, medicine, literature, art, architecture, and philosophy in the tenth and eleventh centuries CE in Iran. This Iranian two-century “intermezzo intellectual zenith,” with a stable state and economic prosperity, was nurtured by the vast heritage of the ancient Iranian, Mesopotamian, Indian, and Egyptian civilizations and elements of the ancient Avestan, Sanskrit, and Pahlavi writings since ca. 1200 BCE. Social, economic, and political conflicts followed by invasions by Central Asian nomadic tribe warlords and their accompanying hordes in 1000–1040 CE (Saljuqs), 1218–1231 CE, and 1256 CE (Mongols), and 1370 CE (Timurids), and their occupation caused the process of irreversible decay, retrogression, and general intellectual decadence until the Safavids (1491–1772 CE). During this relatively long dark period, there was a drastic decline in interest in geological research and writing, though some old mining efforts were active. Throughout the eighteenth to the mid-twentieth centuries, foreign travelers made some contributions to the geology and mineral resources of Iran. It was during the second half of the twentieth century when once again earth science research blossomed in Iran with the help of European geologists. This ushered in a new period of modern geologic studies of Iran by native geologists. In memory of Emil Tietze (1845–1931), Alexander von Stahl (b. 1850), Setrāk Ābdāliān ( 1894–1963), Eugène Rieben (1899–1972), Heinrich Martin Huber (1917–1992), Jovan Stöcklin ( 1921–2008), Ricardo Assereto (1939–1976), and all pioneers in the past, who enthusiastically and rigorously intruded ever deeper into virtually unexplored territories in difficult and uncomfortable circumstances, extremely devoted to scientific pursuits, and shaped our understanding of the geology, tectonics, mineral resources, earthquakes, and seismotectonics of the Iranian Plateau .