Long-period earthquakes and co-eruptive dome inflation seen with particle image velocimetry.

Dome growth and explosive degassing are fundamental processes in the cycle of continental arc volcanism. Because both processes generate seismic energy, geophysical field studies of volcanic processes are often grounded in the interpretation of volcanic earthquakes. Although previous seismic studies have provided important constraints on volcano dynamics, such inversion results do not uniquely constrain magma source dimension and material properties. Here we report combined optical geodetic and seismic observations that robustly constrain the sources of long-period volcanic earthquakes coincident with frequent explosive eruptions at the volcano Santiaguito, in Guatemala. The acceleration of dome deformation, extracted from high-resolution optical image processing, is shown to be associated with recorded long-period seismic sources and the frequency content of seismic signals measured across a broadband network. These earthquake sources are observed as abrupt subvertical surface displacements of the dome, in which 20-50-cm uplift originates at the central vent and propagates at approximately 50 m s(-1) towards the 200-m-diameter periphery. Episodic shifts of the 20-80-m thick dome induce peak forces greater than 10(9) N and reflect surface manifestations of the volcanic long-period earthquakes, a broad class of volcano seismic activity that is poorly understood and observed at many volcanic centres worldwide. On the basis of these observations, the abrupt mass shift of solidified domes, conduit magma or magma pads may play a part in generating long-period earthquakes at silicic volcanic systems.

Predictability of Precipitation Over the Conterminous U.S. Based on the CMIP5 Multi-Model Ensemble.

Characterizing precipitation seasonality and variability in the face of future uncertainty is important for a well-informed climate change adaptation strategy. Using the Colwell index of predictability and monthly normalized precipitation data from the Coupled Model Intercomparison Project Phase 5 (CMIP5) multi-model ensembles, this study identifies spatial hotspots of changes in precipitation predictability in the United States under various climate scenarios. Over the historic period (1950-2005), the recurrent pattern of precipitation is highly predictable in the East and along the coastal Northwest, and is less so in the arid Southwest. Comparing the future (2040-2095) to the historic period, larger changes in precipitation predictability are observed under Representative Concentration Pathways (RCP) 8.5 than those under RCP 4.5. Finally, there are region-specific hotspots of future changes in precipitation predictability, and these hotspots often coincide with regions of little projected change in total precipitation, with exceptions along the wetter East and parts of the drier central West. Therefore, decision-makers are advised to not rely on future total precipitation as an indicator of water resources. Changes in precipitation predictability and the subsequent changes on seasonality and variability are equally, if not more, important factors to be included in future regional environmental assessment.