What controls b-value variability in an active oceanic volcanic island? A multi-parameter study of the seismicity of Tenerife (Canary Islands).

Tenerife (Canary Islands, Spain) is an active oceanic volcanic island where low to moderate seismicity provides one of the few direct windows into the present stress state, hydrothermal, and volcanic activity. The island contains four main volcanic systems that interact in complex ways, and its seismic behaviour is also influenced by regional tectonic stresses, including the fault zone between Tenerife and Gran Canaria. Since 2016, small but persistent changes in the rate and spatial pattern of local earthquakes have been observed. These changes raise the question of how Gutenberg–Richter parameters and related metrics respond to an evolving volcanic–tectonic setting. 

 

In this study, we use a catalogue-based, multi-parameter approach to investigate the factors controlling variations in the Gutenberg–Richter a and b values in Tenerife. The analysis is complemented by simple fractal measures that describe how earthquake hypocentres cluster in time and space. We track the spatial and temporal evolution of these parameters using moving windows at different scales, paying particular attention to magnitude completeness, as seismicity is strongly concentrated in a few areas of the island. 

 

We explicitly separate background seismicity from well-defined swarm episodes. Swarms are analysed both independently and as part of the whole catalogue, allowing us to quantify the extent to which they influence overall estimates of a, b, and the fractal dimension. 

 

By comparing the resulting parameter patterns with the main volcanic systems, rift zones, and structural lineaments, we explore how variations in b-value and clustering reflect differences in stress conditions and structural complexity. Special attention is given to areas and time periods in which, based on independent geochemical data, the hydrothermal system is known to have played an important role, as fluid circulation can enhances microseismicity in Tenerife 

This work aims to provide observational constraints on the interpretation of Gutenberg–Richter parameters and fractal metrics in an ocean-island setting. We show how this simple but information-rich framework can help distinguish volcanic, tectonic, and hydrothermal contributions to seismicity in Tenerife, and can serve as a basis for future models that link b-value variability to underlying physical processes in interacting volcanic systems.