Coupling observable data to the spatio-temporal properties of natural hazards, An application to the volcanic field of Harrat Rahat, Saudi Arabia

The volcanic field of Harrat Rahat in Saudi Arabia is a highly complex volcanic system with 950+ volcanic cones or craters distributed over 20,000 km2 and with evidence of volcanic activity spanning from 10 Ma to present with two historical eruptions in 641 AD and 1256 AD. This record, the proximity of Harrat Rahat to the city of Al-Madinah, and a possible stalled eruption in 1999 AD, drives a need to quantify the likelihood and magnitude of future eruptions. For volcanic fields, as is common for the majority of natural hazards, we cannot yet directly observe the underlying geophysical processes, nor do we understand them sufficiently to create reliable, predictive models. However, technological advancements and novel monitoring techniques facilitate the collection of a vast range of data types from satellite based to subsurface measurements for a region of interest. Observable data for Harrat Rahat include: vent locations, volumes and spatial distributions of past eruptive products, aeromagnetic and seismic interpretations of sub-surface structure, and regional tectonic models. We present here a bootstrap method whereby observed data values at the locations and times of an eruption are compared to values sampled at random points in space-time. This allows direct determination of the relationship (if any) between each observable data set and the spatio-temporal recurrence rates of volcanism in Harrat Rahat.