Earthquake Off the Coast of Lisbon, Portugal: A Wake-Up Call from the North Atlantic Ocean

In the early hours of Monday, August 26, 2023, residents of Lisbon and surrounding areas were jolted awake by a 5.4-magnitude earthquake that struck off the coast of Portugal. This seismic event, the strongest in the region in 15 years, has reignited discussions about earthquake preparedness and the geological dynamics of the North Atlantic Ocean. The earthquake was centered approximately 64 kilometers southwest of Sesimbra, a coastal town south of Lisbon, and occurred at a depth of 17 kilometers beneath the seabed. The U.S. Geological Survey (USGS) and Portugal’s seismological agency, IPMA, reported slightly different magnitudes for the quake, with the USGS recording it as 5.4 and the IPMA as 5.3.

The tremors were felt not only in Lisbon but also in other nearby cities and as far away as Morocco, including the Casablanca area. The shaking, described as light to moderate, lasted for about 3-5 seconds, enough to wake many residents and disturb pets, particularly dogs. Despite the widespread sensation, there were no reports of serious damage or injuries, and experts confirmed that there was no threat of a tsunami. This incident has been a stark reminder of the region’s vulnerability to seismic activities, even though such events are relatively rare compared to more seismically active areas like California or Japan.

Historically, Portugal has experienced significant earthquakes, the most devastating being the Great Lisbon Earthquake of 1755, which had an estimated magnitude of 8.5-9.0 and resulted in widespread destruction and loss of life. The 1755 earthquake and the subsequent tsunami and fires profoundly impacted the city and its architecture, leading to the reconstruction of Lisbon with more earthquake-resistant buildings. While Monday’s earthquake was much less severe, it serves as a poignant reminder of the potential dangers lurking beneath the ocean floor.

The epicenter of this recent quake was located near the CNN Portugal studios, where journalists were covering a special report on the Middle East. Video footage captured the reactions of the journalists as they felt the tremors, providing a real-time glimpse into the human response to such natural events. This footage has since gone viral, highlighting the immediacy and unpredictability of earthquakes. For many residents, the early morning quake was a disorienting experience, with some initially unsure if they were dreaming or experiencing a real event until their family members confirmed it.

In the aftermath of the earthquake, experts have been closely monitoring the region for any aftershocks or further seismic activity. The USGS received over 1,358 reports from people who felt the earthquake, indicating its wide-reaching impact. While the immediate threat has passed, the event has sparked renewed interest in earthquake preparedness and the importance of having an emergency plan in place. For a country with a rich history of seismic activity, this recent quake is a reminder that vigilance and preparedness are crucial.

Comparatively, the earthquake in Portugal occurred just hours after a 6.1-magnitude earthquake in Tonga, centered in Pangai with a depth of 106.7 kilometers. This juxtaposition of seismic events across the globe underscores the interconnectedness of Earth’s tectonic systems and the need for a global approach to understanding and mitigating the risks associated with earthquakes. While the Tonga earthquake was significantly stronger, its greater depth likely mitigated its impact on the surface, unlike the shallower quake off the coast of Portugal.

Seismologists have pointed out that the shallow depth of the Portuguese earthquake made it more likely to be felt by people on the surface. Shallow earthquakes, typically those occurring at depths of less than 70 kilometers, tend to cause more noticeable shaking and can be more destructive than deeper quakes. In this case, the 17-kilometer depth of the quake meant that its energy was concentrated closer to the Earth’s surface, amplifying the shaking felt by residents in Lisbon and surrounding areas.

Despite the lack of serious damage, the psychological impact of the earthquake on the residents cannot be understated. Many people reported feeling scared and anxious, particularly those who were abruptly awakened from sleep. The suddenness and unpredictability of earthquakes can be deeply unsettling, leading to heightened awareness and concern about future seismic events. This is especially true for older residents who may have memories of previous significant earthquakes in the region.

The earthquake has also prompted discussions about the need for improved building codes and infrastructure resilience in Portugal. While modern buildings in Lisbon are constructed to withstand seismic activity, there are still many older structures that may not be as resilient. Ensuring that all buildings, particularly schools, hospitals, and other critical infrastructure, are retrofitted to meet current earthquake safety standards is essential for minimizing the risk of casualties and damage in future events.

In addition to physical preparedness, public education about earthquake safety is crucial. Residents need to be aware of what to do during an earthquake, such as taking cover under sturdy furniture, staying away from windows, and knowing how to turn off utilities like gas and electricity to prevent fires. Regular earthquake drills and public information campaigns can help ensure that people are ready to respond effectively when an earthquake strikes.

Looking ahead, scientists continue to study the tectonic activity in the North Atlantic Ocean to better understand the mechanisms driving these earthquakes. The region is influenced by the complex interactions between the Eurasian, African, and North American tectonic plates. By analyzing data from recent earthquakes, researchers hope to improve their ability to predict future seismic events and develop more effective strategies for mitigating their impact.

Ultimately, the 5.4-magnitude earthquake off the coast of Lisbon serves as a timely reminder of the ever-present threat posed by natural disasters. While it was not a catastrophic event, it has highlighted the importance of preparedness, resilience, and ongoing research in safeguarding communities against the unpredictable forces of nature. As the people of Lisbon and surrounding areas return to their daily lives, the lessons learned from this earthquake will undoubtedly contribute to a safer and more resilient future.