Creating a Libyan Earthquake Archive: from Classical Times to the Present

Open Journal of Earthquake Research, 2020, 9, 367-382 https://www.scirp.org/journal/ojer ISSN Online: 2169-9631 ISSN Print: 2169-9623 Creating a Libyan Earthquake Archive: From Classical Times to the Present Somaia S. Suwihli1,2*, Thomas R. Paradise1 1Department of Geosciences, University of Arkansas, Fayetteville, USA 2Department of Geography, University of Benghazi, Benghazi, Libya How to cite this paper: Suwihli, S.S. and Abstract Paradise, T.R. (2020) Creating a Libyan Earthquake Archive: From Classical Times Libya’s seismicity has been considered relatively minor, however, several to the Present. Open Journal of Earthquake earthquakes of magnitude larger than 5.0 have occurred since Roman times. Research, 9, 367-382. The scope of this study is to identify and chronicle past seismic frequency and https://doi.org/10.4236/ojer.2020.94021 magnitude in Libya by translating, analyzing, and compiling historical sources Received: July 1, 2020 and archaeological data of Libya’s seismic history. The earliest references to Accepted: August 17, 2020 earthquakes have been found in historic records and archaeological data since Published: August 20, 2020 262 AD. Archaeological evidence was found to support Latin records that stated that the shock destroyed much Cyrene also affecting most of the Province of Copyright © 2020 by author(s) and Cyrenaica. In 704 AD, a large shock destroyed towns and villages across the Scientific Research Publishing Inc. This work is licensed under the Creative Sebha region. While in 1183, a violent tremor shook Tripoli. In 1935 and Commons Attribution International 1939, a series of large earthquakes struck the Hun Graben area, including one License (CC BY 4.0). of magnitude 7.1 on April 19, 1935—considered the strongest earthquake in http://creativecommons.org/licenses/by/4.0/ Libyan history. The coast of northeastern Libya in Al-Jabal Al-Akhdar areas Open Access continues to be a seismically active region. In 1963, the Roman outpost of Barca (modern Al-Marj) was razed by an earthquake of moderate magnitude (5.6 Ml). Offshore earthquakes with magnitudes of 5.6 and 4.9 occurred in Tripoli in 1974 and 1976. In addition, several tremors of 4 to 5.6 magnitude were recorded in northeastern and northwestern Libya between 1990 and 2019. With little previous knowledge of Libya’s quake history, an estimate of seismic periodicity and event consequences is problematic. Such an archive of seismic hazards (frequency, location, magnitude) is fundamental to estimat- ing seismic risk (future events, consequences). Keywords Libya Earthquake, Seismic Activity, Frequency, Magnitude, Richter, North Africa 1. Introduction The seismic activities in Libya have been considered relatively minor [1], how- DOI: 10.4236/ojer.2020.94021 Aug. 20, 2020 367 Open Journal of Earthquake Research S. S. Suwihli, T. R. Paradise ever, several earthquakes of magnitude larger than 5.0 have been documented in different areas in the country [2] [3] [4]. Though its history is relatively less seismically active and damaging than some other sites, nevertheless, a series of relatively recent earthquakes with magnitudes (Richter) up to 7 occurred on April 19, 1935; it has been described as the strongest earthquake in Libya’s history, and one of the largest earthquakes in Africa’s history [5] [6]. The ancient and recent history, of earthquakes in a region located on the Mediterranean boundary of the African Shield, is particularly interesting. The complicated geologic structures between Eurasia and Africa, the corresponding plate movement, and the underlying driving forces, lead to strong variations in seismic hazard throughout the area. Libya, located on the Mediterranean foreland at the north- central margin of the African continent, has experienced considerable tectonic activities, especially along its northern coast [7]. An understanding of the regional seismicity related to this seismo-tectonic setting mostly depends on the data from instrumental records, so many historical earthquakes of the past are rarely known or recorded. Identifying prehistoric and historic earthquake hazards and history is an important component of predicting the causes and effects of future earthquakes and the assessment of risk (i.e. deaths, injury, and eco- nomic loss) because past earthquakes suggest the location, magnitude, and size of future earthquakes [8]. To better understand earthquake hazards, regional tectonics, and the present- day evolution of Libya’s seismicity, this study addresses the region’s earthquakes from Roman records, to the monitoring of modern national geophysical centers and global seismic data, to create a comprehensive earthquake archive. This earthquake archive can be used to 1) create Libya’s first national earthquake pol- icies for effective mitigation (i.e. planning, policy, engineering, education), 2) a foundation to create structural construction standards, and to 3) assist in the preparation for future hazardous events and risk assessment. These findings are expected to contribute to the greater understanding of the earthquake activity in Libya, and to advance knowledge of regional earthquakes in Libya, across North Africa, and the Mediterranean Basin. 2. Geologic Setting of Libya Libya is located in the Northeast African Tectonic Zone which is bordered by the Gulf of Aqaba and Red Sea to the East. The northeastern portion of the African Continent represents the contact between the African, Arabian, and Eura- sian/Anatolian Plates (Figure 1). These plates are involved in the geodynamic reconstructions of the south part of the east of Mediterranean [9]. The models of plate tectonic suggest the African plate is moving northward relative to the Eu- rasian plate at a rate of ~6 mm/year [10] [11] while the Arabian plate is moving north-northwest toward Eurasia at a rate of about ~18 mm/year [12]. Due to these movements, crustal spreading is occurring along the axis of the Red Sea and left-lateral slip along the Dead Sea Transform Zone. The different rates of DOI: 10.4236/ojer.2020.94021 368 Open Journal of Earthquake Research S. S. Suwihli, T. R. Paradise movement between Africa and Arabia (~12 mm/year) is taken-up by a left-lateral motion along the Dead Sea Transform Fault [6] [13] [14]. Corti et al. [15] sug- gested that the Red Sea Rift is transferring compressional stress to Libya and west- ern Egypt, generating significant earthquakes along the southeastern Mediterranean where earthquakes are widely felt and have caused widespread damage [12] [16]. 3. Methodology This archive developed a baseline of past and current seismic inventory in Libya, and that is by providing the dates, locations, and magnitudes of seismic events Figure 1. Tectonic map of Central Mediterranean Sea and Tripolitania-Sirte Basin, Libya [17]. Cartography by authors, 2020. DOI: 10.4236/ojer.2020.94021 369 Open Journal of Earthquake Research S. S. Suwihli, T. R. Paradise (when possible). In order to incorporate both quantitative and qualitative me- thods, this study used multimedia records, documents, and past archives of Libya’s earthquake history (i.e. written records, newspapers, film, images). By translating Latin codices, records and texts, and Arabic, French, Italian, and English records, oral histories, newsreels, and news sources, the authors created an archive representing the earliest earthquake activity in Libya from the Clas- sical period (262 AD) to our modern times from varied multi-lingual sources. The collection of historical and ancient seismic events relied upon a combina- tion of historical records, and archaeological data when recorded information was not extant. Seismic records were rare in ancient times, so the archive relies upon archaeological data. Guidoboni [18] with the collaboration of Comastri and Traina, as well as Ambraseys et al. [16] published catalogues of earthquakes in which Libya events were included. Dating of early earthquakes was derived from the archaeological chronological evidence provided by dated artifacts of known/estimated age (i.e. ceramics, coins) excavated above and below the ruins— a conventional technique [19]. For example, in the cities of Sabratha (NW Libya) and Cyrene (NE Libya), the dates of their razing by earthquakes was dated by 1) Greek Christian inscriptions [18] [20] and 2) excavated coins unearthed in the quake-related rubble and ruins [21] [22] [23]. Excavation and dating of artifacts related to structural collapse and debris is widely used and has proven itself valuable and quite accurate when records are subsequently discovered that corroborate the dates of the temblors, and the estimated intensity and magnitudes of the events. In the early 20th century, Sieberg [24] discussed Libyan historical earthquakes in his comprehensive tome of earthquakes of the region, Erdbebengeographi. Such descriptive catalogues, known for their in-depth classical compilations, are often the only primary works and translations used to identify these early quakes (i.e. Tripolitania 1183). However, in this research, it was the lacunae of these early catalogues that required updating from antiquity to into the 20th Century [4] [24]. Dates, information, and narratives from 20th Century earthquakes were col- lected and revised from varied sources including compilations from Rudolph [25] in addition to French findings from Critikos [26], Italian research from Ca- vasino [27] and Lipparini [28], data from U.S National Geophysical Center and Solar-Terrestrial Data Center in Kebeasy’s study [29], Ambraseys’ work [2] [16],

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