Seismicity In Saudi Arabia And The Red Sea Literature Review Sample

Abstract

Most earthquakes in Saudi Arabia are a result of the separation along the mid-rift of the Red Sea and the Gulf of Aden in the South, which have caused an extensive movement along the Gulf of Aqaba in the North. This movement has created what are known as transform fault systems along the Dead Sea toward the Gulf of Aqaba. In addition, numerous seismic tremors also occur because of the impact in the subduction zone along the Zagros Mountain located in the northeast of the Arabian plate. Moreover, a percentage of the Cenozoic volcanic regions located along the western part of the Arabian shield are still conceivably dynamic, and some seismicity remains connected with this low-level Volcanism. As far as Saudi Arabia is concerned, the most dynamic seismicity ranges along the Gulf of Aqaba, where the left lateral movement with respect to the Gulf of Sinai has been measured at 4 to 5 mm every year. The location of the Gulf of Aqaba has dynamic sinistral change deficiencies, with related force causing separation along the mid-rift of the Gulf of Aqaba, making it a territory where extensive and harmful seismic tremors frequently occur. In this review, Saudi Arabia is divided into four regions: the North, South, West and East. The earthquake activities reviewed and discussed come from available articles for all the regions. Earthquakes that occurred in the Red Sea, the Gulf of Aqaba and close to the Arabian edge are also mentioned in this review. This paper demonstrates that most of the regions in Saudi Arabia suffer seismic risks, with the exception of a central area that lacks volcanic fields. The North, West and Southwest areas, however, are still considered seismically hazardous due to regional volcanic activity that causes earthquake swarms with magnitudes measuring between 3.0 and 5.1. Earthquakes with a magnitude of 6 occur primarily along the spreading zone of the Red Sea. They are not, for the most part, felt inland and seem to be of little risk to the Arabian plate as a whole.

Introduction

The world has many geological hazards that affect people's lives and properties. Earthquakes are one of these causes of disaster as they occur suddenly and can cause great destruction and loss of life. Earthquakes occur in what are known as seismic zones or seismic belts and especially along the edge of the tectonic plates of the Earth's crust, where most of the active faults and volcanic fields are located.
Faults are created by pressure on the rocks and particularly in the Earth's crust that allow for the occurrence of sudden movements along cracks or fissures. These cracks lead to the release of pressure in the form of seismic waves, which can result in the loss of life or property damage. Most of the damage arises from tectonic earthquakes, which are mainly concentrated on the edges of the plates of Earth’s crust. However, earthquakes can also result from the eruption of igneous rocks due to volcanic activity. Therefore, studying the seismicity and the volcanic activity in any given area is essential to either avoiding or predicting some of these disasters. Saudi Arabia is one region where the number of earthquakes has increased dramatically over the past few years.
Saudi Arabia has experienced numerous earthquakes throughout its history, especially in the cities along the Red Sea coast and those near volcanic fields. Gutenberg and Richter reported an earthquake with a magnitude of 6.25 that occurred on January 11, 1941, about 30 km to the east of the city of Jizan, near the town of Abu Arish. Jizan's citizens had felt this event but no damage had been reported at the time. That same year, another big shock with a magnitude of 6.25 occurred in the Western part of the shield (Gutenberg and Richter, 1965). Rothe also reported a 5.5 magnitude earthquake that took place on October 17, 1965 near the Saudi-Yemeni border to the east of Abu Arish. Fortunately, no distressing damaged occurred (Rothe, 1969). Bigger earthquakes were yet to come. In 1967, a 6.9 magnitude earthquake occurred in the Red Sea, nearly 200 km SW of Jeddah. An equally powerful quake had already struck the Southern region of the Red Sea back in 1955 (El-Isa, and Al Shanti, 1989). In 1982, more earthquake activity with magnitudes ranging from 4 to 5 were recorded in the north of Yemen, close to the Saudi border - both of which caused much distress and damage (Roth, 1969). Between 1983 and 1984, 244 earthquake swarms occurred in the Haql region near the Gulf of Aqaba, each with magnitudes ranging between 2 to 4.9 (El-Isa and Al Shanti, 1989).
Cataloguing and then studying the seismic activity in any given area can provide a general overview of that area's seismic risk. In this review, information about the seismicity of Saudi Arabia and the Red Sea will be explained and put into historical context. First, a brief description of the tectonic structure of Saudi Arabia will be addressed. Saudi Arabia will then be divided into the Northern, Southern, Western and Eastern regions. The seismicity in the Red Sea, the Gulf of Aqaba and the Gulf of Aden will also be examined.

The Tectonic structure and the Geology of the Arabian plate

Saudi Arabia is geographically located in southwest Asia and made up of a land area of about 2.25 million km2 (Al-Shanti, 2003). Tectonically speaking, the Arabian Peninsula first started to form some 25 to 30 million years ago as a result of the fault line that occurred between the African Plate and the Arabian Plate, which drove magma from the Earth’s mantle to the surface, as displayed in the figure below.
Figure 1. Shows what the magma looked like under Arabian shield and how it rose to the surface (Al-Amri, 2009)
The Arabian Plate meets the Zagros and Makran Mountains along Iran's Eastern and Northern borders and also borders the Taurus Mountains to the south of Turkey (Saudi Geological Survey, 2010). These geological boundaries form the convergent zone where the Arabian plate eventually collided with the Eurasian plate. This crack occurred along the Red Sea and the Gulf of Aden, which forced the Arabian Peninsula to shift in the Northeast direction, as shown in Figure 2. This is what caused the Arabian plate to collide with the Makran, Zagros and Taurus Mountains in the South and North, respectively (Al-Amri and Rodgers, 2013).
The Arabian Peninsula consists of a Precambrian continental crust that is about 870-550 million years old and has a thickness of about 40-45 km. The younger Phanerozoic sedimentary rocks that make up the topmost layer date from the Cambrian to the Pleistocene, with a thickness ranging from 0 to 10 km (Gettings, 1986). As the Red Sea parted, new magma emerged to cover the Phanerozoic rocks. Erosion then helped to create what we currently refer to as the Arabian Shield, which today makes up a third of Western Saudi Arabia. It currently spans between 50 to 100 kilometers in the North, bulges to 700 km down the middle and then narrows to about 200 km at its Southern-most extreme (Saudi Geological Survey, 2010).
Figure 2. The map represents the plates' tectonic movement. The red line represents the mid rift and the arrows show the direction of the plates (Johnson and Stern, 2010).
Figure 3. A map shows the sedimentary rocks in Saudi Arabia (Saudi Geological Survey, 2010).
Before reviewing the seismicity in each of Saudi Arabia's regions, a brief description of the national seismograph network station will be discussed in the next paragraph.

The Saudi Geological Survey Seismograph Network

Crucial to studying earthquakes and volcanoes is determining why and where they occur. Establishing an appropriate database to evaluate their risks is equally important. The Saudi Geological Survey (USGS) currently monitors and analyzes all the seismic activities within the Kingdom of Saudi Arabia. In 2005, the Saudi Geological Survey established the National Center for earthquakes and volcanoes to fulfill this mandate. The Saudi Geological Survey has since upgraded its seismograph network by using a full range of tools via satellite, with stations concentrated in the Western part of Saudi Arabia, where most of the seismic activity occurs (Al-Amri and Al-Amri. M., 1999). It is also important to note the concentration of stations located to the north of the city of Yanbu, near the Lonyerr Volcano, which was created in 2009 in order to detect the volcanic activity in this region (SGS, 2010).
Figure 4. The Seismic Stations in Saudi Arabia. The red circles represent the volcanism, while the blue triangles represent the seismic stations (King Abdullah University of Science and Technology, 2015).

The Northern part of Saudi Arabia

The Northern region of Saudi Arabia consists of Tabuk and Al-Jouf province, both of which are considered to be relatively inactive seismic zone as compared to the Gulf of Aqaba and the Gulf of Sinai (Al Shanti, 1988). Standing in stark contrast, the Gulf of Aqaba has a high rate of seismicity and has experienced earthquake swarms for the last 2000 years (Klinger, Rivera, Haessler, and Maurin, 1999). In 1995, the Gulf of Aqaba had a large earthquake with a magnitude of 7.3, which caused some damage in the area surrounding its epicenter (Klinger, and Rivera, 1999). The cause of this earthquake was the Dead Sea fault, located in the Southern part of the Gulf. One of the nation's most impressive tectonic features, the Dead Sea fault extends from the African plate to the Arabian plate. As Figure 5 illustrates, the fault extends for about 1000 km and links the sprawling center of the Red Sea until it collides with the Eastern part of Turkey. It has been active since the Miocene (Garfunkel, 1981; Garfunkel and Ben-Avraham, 1996).
Figure 5. The Dead Sea fault and the location of the 1995 earthquake (Klinger and Rivera, 1999).
According to Karaki, these earthquake swarms first started in 1983, with nearly 1000 events, and went on for nearly three months (Abou Karaki, 1993; E1-Isa, 1984). Three high-magnitude events (greater than 5) were detected among these sequences, each located in the Northern part of the Gulf of Aqaba near the Elat Basin. Smaller and less powerful swarms also occurred in April 1990 in the center of the Gulf of Aqaba, between the Elat and the Aragones Basin, with the largest of theses sequences measuring 4.3 M (Abou Karaki, 1993). In 1993, a third swarm occurred in the Southern part of the Gulf of Aqaba. These swarms were much more powerful than their predecessors. In fact, the majority measured more than 3 M and some as much as 6.1 M (Shamir and Shapira, 1994; Fattah, 1997). It can also be concluded that between 1983 and 1993, the epicenter of these different swarms moved from the North to the South of the Gulf of Aqaba, as is displayed in Figure 6.
Figure 6. The locations of the earthquake sequences that occurred in 1983, 1990, and 1993 (Abou Karaki et al., 1993). Also the basins that distributed along the Gulf of Aqaba.
Researchers insist that the earthquakes in the Gulf of Aqaba should be characterized as earthquake swarms that can occur for months or weeks (El-Isa, Merghelani, and Bazzari, 1984). Historical data recorded between the years 1068 to 1964 indicates that the 244 earthquake swarms that occurred had magnitudes ranging from moderate to large (El-Isa, 1984). In 2012, researchers S. Nassir and A. Aref found that these earthquake sequences had in fact migrated from the Southern to the Northern part of the Gulf. They then studied the sequences that occurred in 1993 and 1995 using HYPO71 software (Lee and Valdes, 1985) and discovered that the new location of the aftershocks of both earthquakes occurred in the same fault zone. The focal mechanism revealed that the earthquake migration in question was caused by the shifting of the Dead Sea Fault (Al-Arifi, 1996).
It was also determined that the main shocks of both the 1993 and 1995 sequences, as well as their aftershocks, came from different sources. The locations of these swarms supported the idea that the earthquakes migrated from the South to the North. Thus, the earthquake swarms that occurred in the Gulf of Aqaba migrated from the North to the South between 1983 and 1993 and then migrated again in 1995. Swarm records leading up to the last large earthquake in 1995 support the idea that the Gulf of Aqaba may still experience a significant and disastrous shock in the future, which could very well impact surrounding regions including the Northern part of Saudi Arabia. (Klinger, 1999).

The Western region of the Saudi Arabia

The Western region of Saudi Arabia, which consists of the Arabian Shield as well as several volcanic fields including the Rahat, Lunyyir, and Al-Madina volcanoes, is considered to be seismically active. Figure 8 shows how these volcanoes are distributed along the Northern and Southern Arabian Shield, referred to locally as Harrats (Al-Shanti, 1988). The volcanism of Harrat Lunayyir, meanwhile, is driven by an intrusive dike of about 10 km long (Pallister, 2010). Besides the volcanoes, the shield is also dominated by complex geological structures called Najd Fault systems (Brown and Coleman 1972). Earthquakes in this region - especially those measuring M 5 on the Richter scale - are considered very likely. The Saudi Geological Survey reported nearly 30.000 events in the region. The most recent earthquake occurred in April 2009 and affected Al-Ays city, nearly 40 km southeast of the epicenter near the Lunayyir lava flow area, as displayed in Figure 7. This earthquake reached a moment magnitude of 5.7.
There are two types of earthquake swarms. The first is the volcanic tremor, which is caused by magma activity. The second type is the volcano tectonic (VT), which is caused when magma breaks through the rocks and shoots through to the surface (Sparks, 2003). The Harrat Rahat's area, the biggest volcanic flow in the Kingdom, experienced a micro earthquake in 1999. Theese swarms included around 500 events with magnitudes ranging from M 1.5 to M 3.0 from depths ranging between 30 and 40 km. While these swarms may not have been felt, they demonstrate that the area remains a seismic risk (Lindsay, and Rashad, 2014) But these were not the only earthquake swarms to hit the area. In 2007, the area experienced an earthquake swarm with a maximum magnitude of 3.2 (Al-Zahrani, Al-Amri, 2013). The swarms of 2009, by contrast, were of volcano-tectonic type. (Kenedi and Runge, 2013) The VT type therefore indicates that the tectonic activity in the area is a direct result of the parting of the Red Sea.
Figure 7. Local map shows the locations of the three main volcanoes (harrats) in Saudi Arabia (Kenedi, C. L., Runge, M, 2013).

The Eastern part of Saudi Arabia

Unlike its Northern and Western counterparts, the Eastern region of Saudi Arabia is relatively inactive. In the last ten years, the Eastern province of Saudi Arabia experienced only minor earthquake activity ranging between 1.5 and 4.2 in magnitude. Citizens felt these events and reported them to the firefighter department (Saudi Geological Survey, 2005). The largest earthquake in recent history occurred in 2005. It had a magnitude of 4.2 (Saudi Geological Survey, 2005). Despite its relative seismic calm, it is widely believed that the Eastern region of Saudi Arabia could experience more earthquakes in the future, due in part to the separating of the Red Sea and the Gulf of Aden in the South, which is forcing the Arabian plate to collide with the Eurasian plate moving toward the Northeast. Figure 8 shows how the convergent margin between the Arabian plate and the Iranian or Eurasian plate actually induced what is known as Zagros' folded mountains, where the majority of the earthquake swarms occur (Jackson and Fitch, 1981). Studies show that the result of this movement will lead to more seismic activity in Iran and certain portions of Eastern Saudi Arabia (Al-Amri, 1999). However, for the moment, large earthquakes in this region remain rare.
Figure 8. The figure shows the movement of the Arabian plate toward the Eurasian plate, which created a convergent boundary. The arrows on the figure indicate the direction the respective plates are moving in relation to adjoining plates (after van Eck & Hofstetter 1990).

The Southern part of Saudi Arabia

Although not nearly as remarkable as Saudi Arabia's Western region, seismic activity in the South of the country continues to be strong. More than 300 earthquakes are thought to have occurred in the Southern region between 1900 and 2006, with magnitudes ranging between 3 and 6.6 on the Richter Scale. An earthquake that originated in the Southern Arabian plate and was subsequently felt by Jizan citizens hit Yemen in 1941. Another two earthquakes occurred to the east of Jizan City in 1993 and 1995 with a magnitude of 4.5 and 4.7 respectively. The area around Al Birk Volcano aside, the south of Saudi Arabia doesn't experience many land-based earthquakes. The Southern part of the Red Sea, on the other hand, is considered seismically active due to the separating of the Arabian and African plates (Al-Shanti, 1988). Just as recently as 2014, a micro earthquake (3.0 < M ≤ 5.1) occurred in the Southern region of Saudi Arabia. The epicenter was located some 50 km away from Jizan city at a source about 10 km in depth (Zahran, 2014). According to the Saudi Geological Survey (SGS), the earthquake occurred because the area in question rested on a Quaternary active NW fault trend, as shown in Figure 9. It has also been recently discovered that the Southwestern corner of the Arabian Shield has a volcanic trend near Jizan city, which is responsible for most of the micro earthquakes in the area (SGS, 2014). These tectonic developments mean seismologists are bracing for more earthquake sequences in the South - perhaps even a large one with a magnitude greater than 6.
Figure 9. The sketch shows the fault trends in the Arabian plate. The red circle represent the NW fault, which caused the 2014 earthquake swarms near Jizan city. The sketch map modified from Al-Husseini (2000), Ziegler (2001) and Pollastro (2003).

Conclusion

For the greater part of Saudi Arabia, the risks and dangers associated with seismic tremors remains relativelylow. The primary danger zones remain those close to the Gulf of Aqaba and Jizan, with the West and Center of the country being least vulnerable. The seismicity in the West related to volcanic activities, including the Lunyyir and Rahat volcanos and Birk Harrat, remain areas of particular concern. Moreover, researchers continue to expect more seismic hazards in the Kingdom's Northern and Eastern regions due to the shifting of the Dead Sea fault and the continued Northeastern march of the Arabian plate.

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