How an earthquake becomes a tsunami

Huge Waves Breaking on the Seashore. Photo Source: Pexels

The complex relationship between earthquakes and tsunamis has long puzzled scientists, particularly in the context of subduction zones where oceanic and continental plates meet. The powerful megathrust earthquakes that occur in these regions have the potential to generate devastating tsunamis, making it crucial to understand the processes that drive this transformation. In a significant breakthrough, an international research team, including Prof. James Foster from the Institute of Geodesy at the University of Stuttgart, conducted groundbreaking research in an underwater-earthquake zone off the coast of Alaska. Their use of cutting-edge technology and innovative autonomous vessels provided unprecedented insights into this natural phenomenon. In this article, we explore how earthquakes evolve into tsunamis and the exciting developments in this field.

The Dynamics of Megathrust Earthquakes

Megathrust earthquakes are among the most powerful seismic events on Earth. These earthquakes occur at subduction zones, where an oceanic tectonic plate is forced beneath a continental plate. The relentless collision and friction between these colossal plates result in a build-up of stress and strain. Eventually, this pent-up energy is released in the form of a massive earthquake.

One such remarkable event was the Chignik earthquake, which rocked the coast of Alaska on July 28, 2021. With a magnitude of 8.2, it became the seventh-strongest earthquake in U.S. history. This seismic tremor occurred 32 kilometers below the ocean floor, underscoring the raw power generated by the incessant movement of tectonic plates.

The Subduction Zone Enigma

Despite our awareness of the destructive potential of megathrust earthquakes in subduction zones, the mechanisms driving these seismic events and their connection to tsunamis have remained a topic of scientific intrigue. The primary challenge lies in the ocean floor's inaccessibility for direct measurements, making it difficult to understand how and when an earthquake can trigger a tsunami.

To address this knowledge gap and enhance our ability to predict the likelihood of an earthquake leading to a tsunami, a dedicated team of researchers, under the leadership of Benjamin Brooks from the United States Geological Survey, embarked on an ambitious expedition. Their mission was to explore the seafloor off the coast of Alaska, focusing on the aftermath of the Chignik earthquake.

Cutting-Edge Technology and Autonomous Vessels

A picture of a wave glider equipped with GNSS
and acoustic measurement tools for seafloor monitoring.
Photo credits: University of Stuttgart https://www.uni-stuttgart.de/
en/university/news/all/How-an-earthquake-becomes-a-tsunami/

A pivotal aspect of this research venture was the deployment of cutting-edge technology and autonomous vessels. These advanced vessels, known as wave gliders, are equipped with state-of-the-art instrumentation, including a global navigation satellite system (GNSS) and acoustic measuring devices. Wave gliders are capable of navigating on the water's surface, making them exceptionally well-suited for the challenging conditions of the open ocean.

One noteworthy contributor to the development of these autonomous vessels was Prof. James Foster from the Institute of Geodesy at the University of Stuttgart. These wave gliders played an indispensable role in collecting invaluable data and observations in the underwater earthquake zone off Alaska.

Precise Measurements to the Nearest Centimeter

Topography and bathymetry of the Alaska subduction zone’s Semidi section.
Image reference: Science Advances
https://www.science.org/doi/10.1126/sciadv.adf9299

The groundbreaking element of this research was the precision of the measurements obtained. The team managed to capture the movements within the subduction zones with unprecedented accuracy, down to the nearest centimeter. This level of precision enabled researchers to focus specifically on the shallow segments of the slip zones, as these regions are particularly crucial in determining whether a tsunami may be generated.

Understanding the Significance of Shallow Zones

Shallow parts of subduction zones are where the magic happens, scientifically speaking. In these regions, the oceanic plate grinds against the continental plate, building up immense pressure and tension. This is the point where the potential for a massive release of energy is at its highest, setting the stage for a tsunami.

The Quest for Deeper Insights

While this research has provided significant insights into the dynamics of subduction zones, there is a yearning for a more profound understanding. Prof. James Foster, a central figure in this research, expressed a desire to measure the movements of the seafloor at even greater depths, specifically at depths ranging from 3,000 to 4,000 meters. These depths are directly above the shallowest part of the fault system, and exploring this uncharted territory represents the next frontier in tsunami research.

Overcoming the Challenges

The primary challenge of obtaining measurements at these extreme depths is the limitation of existing geodetic systems. However, there is optimism on the horizon. Researchers anticipate acquiring a device equipped with sensors capable of taking geodetic measurements at these extreme depths. With this cutting-edge technology, scientists are poised to gain direct access to the deepest sections of tsunamigenic faults, advancing our understanding of the processes that transform earthquakes into tsunamis.

Conclusion

The journey from an earthquake to a tsunami is a complex and intricate process that involves immense geological forces and precise conditions. Recent advancements in technology and international collaboration have provided a significant leap forward in our quest to understand this natural phenomenon.

As researchers continue to push the boundaries of knowledge and as technology evolves, we edge closer to demystifying the intricacies of how an earthquake can lead to a tsunami. This newfound understanding promises not only to enhance our ability to predict and respond to these catastrophic events but also to safeguard lives and reduce the impact of tsunamis on coastal communities worldwide. It is a testament to the relentless pursuit of knowledge and the relentless spirit of exploration that drives scientific progress.

Source: https://www.science.org/doi/10.1126/sciadv.adf9299
https://phys.org/news/2023-06-earthquake-tsunami.html