Spatial Orientation and Persistence Variability in Seismicity Patterns Related to Volcanic Activity in Hawaii: Applications to Hazard Assessment

Volcanic activity, which often includes a complex interplay between different factors such as magmatic processes, changes in crustal stress, earthquake events, etc., may lead to remarkable challenges regarding the identification of practically useful hazard patterns. These patterns may change over time at variable speed and in ways that are difficult to predict. Nevertheless, it is very important for hazard management to achieve a reasonable characterization of such patterns at different spatial and temporal scales. Events thread analysis (ETA) has the advantage of grasping spatial and temporal aspects of earthquake patterns together with their relation to scale. In this paper we apply ETA in three-dimensional physical space to study orientation-dependent scaling properties of seismicity patterns related to hot spot volcanism in Hawaii. The events threads are obtained by connecting series of hypocentres of successive earthquakes; projections of events threads corresponding to all the possible spatial orientations with a given angular resolution are constructed and subjected to detrended fluctuation analysis. The resulting isopersistence diagrams characterize space-time correlations in seismicity patterns for different time windows. One can thus apply a rigorous tool to identify and compare persistence in the scaling behaviour of seismicity patterns for any orientation. Isopersistence diagrams provide "dynamic fingerprints" of the system under investigation, which we discuss in the light of the eruption history and of information from geological and geophysical investigations. We show that in the case of Hawaii one can distinguish relatively long-lived, stable dynamic regimes, interrupted by departures that can be interpreted in terms of the changing relationships between different parts of the geosystem. Eventually, due to a new type of phase space based on isopersistence diagrams, one can follow the evolution of dynamic fingerprints of Hawaiian volcanism and obtain timely information about relevant changes in hazard patterns.