Jensen, Esther Hliðar

In January 2020, inflation up to 5 cm was detected in the volcanic system of Svartsengi, Reykjanes peninsula (Iceland). The inflation was probably linked to the movement of magma which was estimated to be at a depth of 3-5 km. Shortly after the detection of the inflation, the Scientific Advisory Board responsible for tackling the unrest deemed possible that the unrest could evolve into an effusive eruption. We used both the MrLavaLoba and the DOWNFLOW codes to simulate the area potentially inundated by lava flows in order to assess the hazard posed in case of an effusive eruption. The DOWNFLOW code was used to create a suite of 10,000 simulations which were used to derive maps of the lava flow hazards. These maps can be dynamically updated to account for ongoing modifications suggested by the geophysical signals of the monitoring system. The MrLavaLoba code, in turn, was tuned based on the historical lava flows in the area, so it would be ready to simulate potential lava flow fields if an eruption began. At the time of writing (April 2020), the area appears have experienced two intrusions and is currently in a waning phase. However, the lava flow modeling carried out constitutes an example of rapid response during an ongoing crisis. The post-processing of DOWNFLOW simulations can also allow for preliminary estimations of the time left before lava flow inundates given targets, providing effective support for stakeholders.

During the emplacement of the 2014-2015 lava flow in Holuhraun (Iceland) a new code for the simulation of lava flows (MrLavaLoba) was developed and tested. MrLavaLoba is a probabilistic code which derives the area likely to be inundated and the thickness of the final lava deposit. The flow field in Holuhraun progressed through a fairly flat floodplain, and the initial limited availability of topographic data was challenging, forcing us to develop specific modeling strategies. The development of the code, as well as simulation tests, continued after the end of the eruption, and latest results largely benefitted from the availability of improved topographic data. MrLavaLoba simulations of the Holuhraun scenario are compared with detailed observational analyses derived from the literature. The obtained results highlight that small-scale morphological features in the preemplacement topography can strongly influence the propagation of the flow. The distribution of the volume settling throughout the extension of the flow field turned out to be very important, and strongly affects the fit between the simulated and the real extent of the flow field. The performed analysis suggests that an improvement in the code should allow adaptable calibration during the course of the eruption in order to mimic different emplacement styles in different phases.