Measurement of terrestrial radiation level in a neotectonic fault system in Trinidad

Publication date: February 2019

Source: Journal of Environmental Radioactivity, Volume 197

Author(s): K.S. Banerjee, A. Baijoo

Abstract

Present study area, which is located in the Central Range Fault (CRF) in the island of Trinidad, can provide solution to that problem as this strike-slip fault system is reported to be active in present time (during Holocene, most current geological epoch) with a movement of geodetic rate of 12 ± 3 mm/yr. Most recent work, with improved GPS time series analysis indicated that as creeping fault rather than locked fault. Moreover, the selected fault system is accompanied by mud volcanoes, which can amplify the level of radiation activity by slight but significant anomalies as described by some researchers from other areas. Furthermore, being one of the first environmental radiation study in the Caribbean Islands, this study is significant. With the aim to achieve a continuous monitoring of radiological data to assess the activity along CRF for possible earthquake forecasting, objectives of this preliminary investigation are to delineate CRFZ using radiation survey and to investigate the potential of using this survey to detect tectonic activities in this zone. As a pilot study, radiation measurements were carried out with the help of a portable Geiger Muller counter in 52 locations along the 25 km long section of CRF between Naved Dam and Pointe-a-Pierre. Radiation measurements were taken both at 1 m level above the surface and at nearly 1 m below the ground. Results from this pilot study showed that lithology was not the lone contributor to terrestrial radiation levels, as CRFZ and associated fissure plane have good control also (∼3–5 times higher than the average background level). Although present study was not able to indicate the possibility of earthquakes in recent times (as previously stated), however, elevated radiation values in the vicinity of CRF, associated fissures (possibly interconnected fractures) and active mud volcanoes indicate possible activity in the study area. However, detail and periodic radiological studies are required before concluding that CRF is a creep fault rather than a locked fault.

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