As a geophysicist, I navigate the realm of geodesy with a keen interest in earthquakes and seismic hazards!

The Earth's shape might seem unchanged over time, but our planet is, in fact, a dynamic entity constantly undergoing subtle changes. These changes can have profound implications for both our environment and society. Especially when a significant amount of crustal deformation accumulates over years in a region, it indicates the potential for a large earthquake there in the future! Thus, geodesy —the study of measuring the Earth— plays a critical role in assessing seismic hazards for tectonically active regions.

Interferometric Synthetic Aperture RADAR processed using ISCE2 software (The 2019 Ridgecrest Earthquake Sequence; Sentinel-1A DT071)

How do we measure these motions?

The movements of the Earth's surface are subtle, unless an extreme event  occurs, such as volcanic eruptions or large earthquakes. The typical rates of plate motion in California are a few centimeters per year, similar to the rate at which our nails grow. It is challenging to accurately measure these movements with the naked eye. In addition, the horizontal extent of tectonically active regions can span 100s to 1000s of km, complicating the monitoring of crustal deformation. Thus, geophysicists utilize satellites to measure the movements of the Earth's surface across larger areas, achieving accuracy within a few millimeters to centimeters per year.

Global Navigation Satellite System (4mo horizontal displacements)

What do I do with these satellite-based geodetic data?

I use satellite-based geodetic data to model crustal deformation and investigate the geophysical processes behind the observed shape changes. Various mechanisms can lead to crustal deformation: groundwater extraction, variations in surface hydrologic loads, crustal thermal expansion, volcanic activities, plate tectonics, and earthquakes (Indeed, earthquakes also result in crustal deformation, which can significantly load or unload adjacent faults). In summary, satellite geodesy techniques, such as GNSS and InSAR, offer unparalleled observations for precise geophysical modeling of crustal deformation!

Poly3D, a boundary element method tool, which calculates crustal deformation associated with a given earthquake source