What is the role of GPS and InSAR in monitoring tectonic hazard activity?

• A. GPS measures rainfall patterns to predict landslides.
• B. GPS measures precise crustal displacement; InSAR detects surface deformation using radar phase changes; both track strain and fault movement for hazard assessment.
• C. InSAR measures magnetic anomalies.
• D. Both are used to locate mineral deposits.

Answer: (B)

Measuring how the crust moves and stores strain is essential to understanding tectonic hazard activity. GPS networks provide precise, time-stamped three-dimensional position data at many ground stations along faults, so you can see how far and in what direction the ground shifts over days, months, or years. This reveals slow accumulation of strain and rapid movements during earthquakes. InSAR uses radar imagery from satellites to map surface deformation over wide areas by analyzing changes in the radar signal phase; tiny ground movements change the distance to the satellite, allowing a detailed map of surface movement with high spatial resolution and millimeter-scale sensitivity.

Together, GPS gives exact point-by-point movement over time, while InSAR provides broad-area deformation patterns. This combination lets scientists quantify fault slip, monitor how strain is building or releasing, detect unusual deformation that could hint at precursors or postseismic relaxation, and assess hazards such as future fault rupture. These tools focus on crustal deformation rather than rainfall patterns, magnetic anomalies, or locating mineral deposits.