When a tremor occurs in the Southern California area, everyone’s attention shifts toward Caltech’s Seismological Laboratory, commonly referred to as Seismo Lab.
For more than a century, the Seismo Lab has led the way in geological and geophysical studies, providing insights on seismic events to the public—detailing where they happen, their magnitude, and the probability of aftershocks, for instance. Indeed, local news vehicles are often spotted stationed outside the lab, situated in the South Mudd building, just minutes following a quake in Southern California.
Professor of Geophysics Zhongwen Zhan (PhD ’14) has embarked on a five-year tenure as the Clarence R. Allen Leadership Chair and head of the Caltech Seismo Lab. Zhan succeeds Mike Gurnis, the John E. and Hazel S. Smits Professor of Geophysics and director of the Schmidt Academy for Software Engineering, who managed the Seismo Lab for the last 15 years.
Zhan engaged with us regarding his aspirations for the Seismo Lab’s future.
What functions does the Seismo Lab serve?
The Seismo Lab boasts a rich legacy. Our aim is to comprehend the dynamics of significant earthquakes and seismic phenomena globally, operating some of the most advanced seismic networks worldwide. We utilize the data from these networks to disseminate information about earthquakes—when, where, and their magnitude. Particularly following major quakes, we often provide crucial information to both the public and emergency personnel regarding locations of significant damage and so forth.
What types of innovative technologies can we expect to see at the Seismo Lab in the coming years?
In addition to community engagement, we delve into the physics underlying earthquakes while operating some of the finest seismic networks globally. The Southern California Community Seismic Network (SCSN) spans across the region and features over 500 seismometers. We are planning to enhance networks like these with even more precise tools for detecting seismic waves. For instance, my lab is developing techniques to adapt telecommunications fibers into a dense array of seismic sensors. This approach will enable us to augment the accuracy of earthquake measurements.
We are also leveraging AI to rapidly extract information about seismic events to better understand their patterns. Additionally, we are improving satellite observations and computational tools to glean more insights from our data. These are the pathways through which we will continue to advance our methodologies.
Although we have administered a seismic network for over a century, this network consistently evolves over time; thus, every few decades, we innovate and redefine the structure of the seismic network, and this process is ongoing today.
Can you elaborate on the SCSN?
The Southern California network, initially established in 1921, represents one of the earliest seismic networks in existence. It began with fewer than twelve seismometers spread across Southern California. According to today’s standards, those were not particularly effective instruments. Following the initial quantitative assessments of earthquakes, the network expanded considerably. We continuously integrate new technology, and many other regions around the globe have initiated their own seismic networks. Numerous networks now participate in larger national or even global seismic systems. Nevertheless, the Southern California network remains at the cutting edge concerning network construction, technological choices, and data utilization.
While predicting earthquakes is not feasible, what information do we seek about them? What insights can they provide?
Earthquakes occur consistently, with most being so minor that they go unnoticed. However, our seismic sensors can detect even the smallest tremors. By tracing, locating, and analyzing numerous earthquakes, we acquire a much more comprehensive understanding of the forces at play and the activity level of faults. This also helps us gain insights into subsurface geology, such as identifying harder rock versus softer sediment and understanding the impact on the intensity of shaking. Having a solid grasp of earthquakes is essential for preparedness.
Major earthquakes are unavoidable. We are aware that they will take place. Tectonic plates persistently strain the crust around Southern California, and one day that strain will manifest as a significant quake. The most prudent approach is to be ready, and such readiness requires information from scientists and our network. Our fundamental earthquake research is aimed at providing that information as effectively as possible.
We are developing technologies for earthquake early warning systems. This necessitates obtaining earthquake information at remarkable speed. The network can transmit data within a fraction of a second once a quake commences to a central system that analyzes this information and issues early alerts. Following an earthquake, in the subsequent minutes to hours, we can gather much more detailed data, generate products like shake maps, and assess areas of intense shaking. Some of these tools originated here at the Seismo Lab during the 1980s and ’90s and are now employed globally.
How does the Seismo Lab integrate with other research conducted on campus?
Traditionally, seismology has focused on seismic events, but in recent years, we have begun to explore its potential for addressing environmental issues. Seismology enables us to examine geophysical processes just beneath the surface, such as groundwater storage. We can even analyze climate change effects in the ocean since varying ocean characteristics influence seismic wave propagation.
Caltech is advancing in climate studies, particularly concerning the cryosphere [the planet’s ice]. We can implement new observational and modeling capabilities to enhance our understanding of these processes. This marks a new direction for the Seismo Lab. While we will maintain our focus on earthquakes, we will also be expanding our scope to encompass climate-related, ice-related, and water-related phenomena.
So, can seismic waves be compared to X-rays that enable us to see beneath the surface?
Absolutely! Satellites allow us to monitor events occurring on or above the Earth’s surface, but it is significantly more challenging to observe or track ongoing processes occurring underground, even just a few centimeters beneath the surface. Seismic waves function as X-rays, allowing us to peer into the Earth, revealing conditions extending thousands of kilometers down to the core or just a few meters down to subterranean water sources. There is incredible potential in utilizing seismic waves for subsurface exploration, often with significant implications for environmental studies.
What does the future hold for the Seismo Lab?
We will continue to solidify our core strengths by merging essential geophysics research with effective public communication. Especially following the LA wildfires, we recognize the public’s demand for information post-natural disasters.
I have already mentioned our focus on environmental geophysics, and several faculty members are keenly interested in pursuing this avenue. This summer, we will welcome a glaciologist to our faculty.
New avenues are also emerging in planetary geophysics. Our history includes Don Anderson, a former Seismo Lab director from 1967–1989, who played a role in the deployment of the first seismometer to Mars. Many inquiries we have about other planets revolve around subterranean conditions, and geophysical studies are the most effective means to acquire such information. For example, we utilize seismological tools to analyze vibrations on other planets, and geodesy instruments to gauge planetary deformations. Saturn’s icy moon Enceladus serves as an excellent case in point. Enceladus is regularly squeezed by Saturn’s gravitational pull during its orbit, necessitating geophysical expertise to investigate the subsurface dynamics as it deforms and warms. Additionally, we can deploy seismometers to Venus to detect acoustic waves resulting from Venusquakes or volcanic activities. Countless opportunities exist for us to leverage the latest technologies from Earth to improve scientific endeavors on other planets.