Volcanic structure of Long Valley (Northern California, USA) as revealed by seismic monitoring of rocks rigidity field

Category: 13-2
V.I. Lykov, A.O. Mostryukov


UDC 550.34.097 



V.I. Lykov, A.O. Mostryukov


Borok Geophysical observatory of Schmidt Institute of Physics of the Earth of the Russian Academy of Science, Borok (Yaroslavl region), Russia



A wide variety of geophysical, geodesic and hydrogeochemistry methods used in the course of last decades allows to develop theoretical models of composition for the Long Valley volcanic structure. The main goal of our research was to evaluate to what extent the method for determination of massif integral rigidity is applicable to such a complex structure. The method is based on a ratio of brittle to viscous destruction mechanisms in seismic focuses of background earthquakes. We used results of standardized seismogram analysis by Northern California Earthquakes Data Center. Information sources were earthquake focuses, so we were able to trace variations of massif integral rigidity throughout entire area filled with earthquake focuses. At the initial stage of our research, we focused on map construction for zoning of rigidity parameter of seismically active crust strata, as well as caldera sections. It was revealed that а significance of map and strata components depends on a deformation mode of the caldera surface. We discuss also the results of study of reduced rigidity channel detected in South-Western part of the caldera down to depth of 35 km. According to [Hill, 2001], abyssal gas breakthroughs are observed in this area. As a separate task, we studied temporal variations of rigidity, spatial manifestations of these variations, and their possible association with local strong earthquakes.

Keywords: earthquake, seismicity, rigidity, monitoring; stress change.



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