Characterizing mud volcanic activity through terrestrial gamma radiation: Insights into subsurface processes at the...

The Piparo Mud Volcano is a significant natural hazard in Trinidad and Tobago, highlighted by its violent 1997 eruption and subsequent heightened activity in 2019, 2024, and 2025. These events arise from overpressurized subsurface conditions that force fluidized mud and gas to the surface. Despite these ongoing risks, current monitoring frameworks remain surface-based and event-driven, offering limited insight into deeper structural and geophysical precursors of activity. To address this gap, this study applies gamma radiation monitoring to: (1) explore correlations between spatial radiation patterns and geomorphological features, (2) examine temporal variations, and (3) evaluate its potential to predict volcanic activity. Measurements were collected at 40 locations over a 29-month period at six intervals (0, 4, 11, 17, 23, 29), using a Geiger-Müller counter, positioned 1 m above ground level (GL) and 0.5 m below GL. The results revealed contrasting spatial patterns above and below GL, with elevated surface gamma radiation in fracture-dense southern and eastern crater areas, while below GL radiation peaked in opposing pressurized zones. Gamma radiation also varied systematically across three distinct phases: pre-activity (months 0-11), active (months 11-17), and post-activity (months 17-29). During pre-activity, gamma radiation increased above GL and declined below GL, then converged prior to an expulsion event in month 13, and diverged again during post-activity. These patterns demonstrate a clear link between gamma radiation fluctuations and mud volcanic activity, highlighting a novel method for early detection and improved hazard assessment.