The Red Sea is regarded as a part of the continental rift system that stretches from the Dead Sea to Mozambique. Numerous geologists who have mapped its different sections have referred to it as the “Afro-Arabian Rift System” [1] - [3] . In conjunction with the Gulf of Aden, the Red Sea has been demonstrated to signify oceanic rifts at divergent plate boundaries, featuring a triple junction in the Afar Depression ( Figure 1 ) [4] - [7] . Since that time, the utilization of plate tectonics has emerged as a key focus in the research of the Red Sea ( Figure 1 ), as it illustrates a divergent tectonic boundary.

In 2007, a marked increase in seismic activity was observed in the southern Red Sea, prior to a volcanic eruption at Jabal Jazirat al-Tair. In addition, the Zubair Archipelago, located about 50 kilometers to the southeast on the southern Red Sea ridge, has experienced similar magma intrusions accompanied by earthquake swarms over the past few decades [8] . At least six earthquake swarms have occurred over the past 20 years, likely caused by separate magma intrusions. Three of these, in 2007, 2011, and 2013, were followed by volcanic eruptions within a single year. The Zubair Archipelago nowadays consists of ten volcanic islands and several rocks located in the central part of the southern Red Sea ridge, between Yemen and Eritrea. These islands and rocks are approximately 100 meters high, 30 km long, and 10 km wide, and lie parallel to the Red Sea Mountain range [9] .

Some volcanic eruptions are known to have occurred in the southern Red Sea on Jebel al-Tair Island and within the Zubair Archipelago in the 18th and 19th centuries. However, this activity was followed by more than a century of apparent calm until volcanic eruptions occurred at Jebel al-Tair in 2007 and 2008, and a few years later (2011) at Zubair Island, creating a new island (Al Jadid Island) [4] [9] . This island originated from an undersea eruption in December 2011, near Yemen’s coast. The activity, located on the northern edge of the Zubair Islands, was captured by satellites and witnessed by Yemeni Navy helicopters, revealing violent explosions typical of shallow submarine eruptions [10] . Table 1 represents the most recent and historical volcanic activities occurred in Southern Red Sea region.

This study analyzes a recent volcanic seismic swarm in the southern Red Sea, specifically west of the Farasan Islands, southwest of Saudi Arabia. From July 29 to August 4, 2025, the Saudi National Seismic Network recorded over 300 minor earthquakes with local magnitudes ranging from 1.65 to 4.7. The swarm occurred vertically at depths ranging from 4.5 to 30 km, including two earthquakes with local magnitudes of 4.33 and 4.7, respectively. By analyzing the data of this swarm, we conclude that this recent swarm is associated with volcanic activity, specifically a new magmatic intrusion that occurred beneath the middle of the southern Red Sea region. Thus, the possibility of the beginning of the formation of a new volcanic island is raised.

Seismic activity manifested as a swarm of earthquakes between July 29 and August 4, located to the west of the Farasan Islands in the southern Red Sea, southwest of Saudi Arabia. This swarm resulted in over 300 earthquakes, with magnitudes varying from 1.65 to 4.7 on the Richter scale ( Figure 2 ). Among this seismic activity,

two notable earthquakes occurred on the evening of Tuesday, July 29, with average magnitudes of 4.33 and 4.7 on the Richter scale. The first earthquake struck at 11:30 GMT (14:30 Saudi local time), followed by the second at 12:04 GMT (15:04 Saudi local time), occurring at depths of approximately 10 and 13 kilometers, respectively. Figure 3 illustrates a recording from a seismic station belonging to the Saudi National Seismic Network (SNSN), (Farasan Island Station) pertaining to the second earthquake.

Shortly after the occurrence of these two earthquakes, the Saudi Geological Survey (SGS) was notified by several individuals who felt the earthquakes, with no reported losses or damage to the Farasan Islands. The appropriate authorities were alerted regarding the timing and magnitude of the earthquake, including the Saudi Civil Defense, which verified that there were no local damage reports in the immediate vicinity of the events, specifically the Farasan Islands, located very near this seismic activity.

The analysis of the seismic swarm showed that the activity extended in a near-vertical direction at different depths, with the deepest being at 30 km, and the shallowest occurring at approximately 4.5 km, as shown in Figure 4 . The daily analysis during the period from July 29 to August 4 confirmed that the seismic swarm occurred in an almost uniform pattern, taking a vertical direction, as shown in Figure 5 . The analysis may indicate that there is a reason behind the occurrence of this activity in this region, which is likely a volcanic magma intrusion into the southern Red Sea region, as this region is considered a volcanically active area, as occurred recently in the years 2007, 2011, and 2013, Figure 6 .

Basically, volcanic earthquakes typically result from the sudden opening of conduits in the Earth’s crust, as well as rapid changes in magma flow, excessive buildup of gas pressure in the crust, and the collapse of the roofs of magma-expelling underground conduits. According to [12] , volcanic earthquakes are classified into three groups: type A earthquakes, with epicenters between 1 and 10 km deep;

type B earthquakes, with epicenters at a depth of 1 km or less; and explosive earthquakes, which occur on the Earth’s surface. Another classification of volcanic earthquakes can be found in [13] . Near active volcanoes, we also observe what is known as volcanic tremors, which results from long-lasting and fairly continuous volcanic vibrations. While volcanic earthquakes are clearly isolated events, separated by time intervals, volcanic tremors exhibit rather jerky or harmonic behavior. These tremors are associated with subterranean magma flow, magma reservoir fluctuations, volcanic gas eruptions, etc., and are likely to be consistent with recent volcanic tremors that occurred west of the Farasan Islands during July-August 2025. Thus, we believe the recent swarm aligns with type A, as detailed by [12] .

In the southern region of the Red Sea, particularly located approximately 55 - 60 km west of the Farasan Islands, southwest of Saudi Arabia, an earthquake swarm occurred between July 29 and August 4, 2025. The depths of these events varied from about 4.5 to 30 km, with magnitudes ranging from 1.65 to 4.7, respectively. This swarm included two earthquakes that occurred on 29 July with a moderate magnitude exceeding 4 on the Richter scale, the first measuring ML = 4.33, and the second measuring ML = 4.7. The mechanisms of their occurrence were studied to understand their causes, and delineated normal movements trending typically in the same orientation as the Red Sea (northwest-southeast). The frequency contents of the seismic waves generated by some of these earthquakes were determined and measured at low frequency, less than 1 Hz.

A scenario was developed to predict a volcanic eruption at the site of the recent seismic swarm west of the Farasan Islands in the Red Sea, using the ASH3D (USGS) software. The scenario results showed the direction and spread of light and deposited ash, as well as the area expected to be covered by this ashfall, both in the Farasan Islands and in remote areas. The Farasan Islands, along with certain regions in the southwestern part of Saudi Arabia, may be influenced by light ash, while remaining distant from the deposited ash. This indicates that the affected area is facing a “low risk of ash deposition.” However, there may be a risk due to the spread of light volcanic ash, which could disrupt maritime navigation in the Jizan region of southwestern Saudi Arabia. Additionally, it may impact the marine environment surrounding the Farasan Islands, as well as pose health risks to the residents of those islands, such as respiratory issues and other related problems.

Following the examination of the recent seismic swarm, which includes 1) the vertical propagation of the seismic swarm; 2) the analysis of source mechanisms that indicated a normal movement trend along the trajectory of the Red Sea extension; 3) the identification of lower frequencies for certain selected events (below 1 Hz); and 4) the positioning of the swarm along the extension of the last eruptions that occurred in 2007, 2011, and 2013, it can be inferred that the primary cause of this recent seismic swarm is volcanic activity. This activity is linked to the intrusion of volcanic magma beneath the central Red Sea, which directly manifests as rifts that have ascended through the crust of the Red Sea, potentially leading to the formation of new islands in the future, similar to what happened in Jabal Jazirat At-Tair in 2007 and at the Zubair Archipelago between 2011 and 2013.

1. Expanding the quantity of seismic monitoring stations, ground acceleration measurement stations, and crustal deformation observation stations across the Red Sea islands to guarantee the surveillance of any seismic or volcanic occurrences and to evaluate their intensity. This, in turn, will contribute to the accurate monitoring of any seismic or volcanic activity that may occur in the Red Sea.

2. It is essential to exchange seismic data with countries on the west side of the Red Sea, from Egypt in the north to Eritrea in the south. This will help identify the locations of any seismic or volcanic activity that may occur in the Red Sea region, along the entire Red Sea from north to south, thus enhancing assessments of the severity of such activity and ways to mitigate these risks. Furthermore, enhancements in the study of seismic source mechanisms will be achieved.

3. Updating strategic emergency plans to mitigate the effects of volcanic activity is not limited to the Red Sea islands only, but also includes areas containing active volcanic lava fields within the Kingdom of Saudi Arabia.

The authors wish to express their gratitude to all personnel of the National Program for Earthquakes and Volcanoes (NPEV), Geohazard Centre, Saudi Geological Survey (SGS), for their dedication in analyzing and processing the seismological data utilized in the execution of the present study.

Recent volcanic-seismic swarm in the southern Red Sea.

New magmatic intrusion.

Potential of the newly created volcanic Island.