A volcanotectonic cascade: Activation of range front faulting and eruptions by dike intrusion, Mono Basin‐Long Valley Caldera, California

Abstract

[1] Stratigraphic data suggest that during the North Mono-Inyo eruption sequence of $1350 A.D. a series of strong earthquakes occurred near the end of the North Mono explosive phases and the beginning of the Inyo explosive phases. The temporal proximity of these events suggests the possibility of a causal relationship. Geological and geomorphic features of the Hartley Springs Fault are consistent with rupture of the fault during the eruption sequence. These features include steep central slope segments on several fault scarps and a fault scarp and stratigraphic offset since the deposition of $1200-year-old tephra. We hypothesize that the Inyo Dike, found by drilling underneath the main Inyo vents, neared the Hartley Springs Fault as it propagated southward from the Mono Basin circa 1350 A.D. We demonstrate that once the lateral distance between dike and fault was sufficiently small, the mechanical interaction between them could have triggered the slip observed on the fault. The slip, in turn, could have reduced the horizontal confining pressure in a region near the southern tip of the fault. The presence of the main Inyo vents in this region suggests that the reduction in confining stress was sufficient to allow magma to propagate to the surface. The results suggest that a volcanotectonic ''cascade'' of eruptions and earthquakes is a possible mechanism by which a large section of a range front or rift system can be activated because of the positive feedback provided by each element to continued activity.

Magmatic gas emissions at Holocene volcanic features near Mono Lake, California, and their relation to regional magmatism

“…However, the fact that we found CO 2 emissions only near the top of North Coulee is not surprising. Detailed mapping and dating of deposits associated with the 650 yr-old eruptive sequence indicate that North Coulee overlies the source area for magma feeding the long dike that ultimately produced eruptions from Panum Crater to the Inyo craters near the southern end of the Inyo chain (Sieh and Bursik, 1986;Bursik et al, 2003). The North Coulee conduit may thus be the main focus of magmatic gas upflow in this area.…”

“…1) southward along the Mono Craters and Inyo volcanic chains to Mammoth Mountain, on the rim of the Long Valley Caldera (LVC). The MLMM strikes through the westernmost Basin and Range Province, across the Long Valley Caldera, and over the Sierra Nevada range front fault system (Bailey, 1989;Bursik and Sieh, 1989;Bursik et al, 2003), and thus is a volcanic line mainly in the geometric sense. We follow Hildreth (2004) in distinguishing the Mono Lake segment from the Mono Craters chain as well as Mammoth Mountain volcano from the Inyo chain.…”

The invisible hand: Tectonic triggering and modulation of a rhyolitic supereruption

“…While historic links between eruption onsets and seismicity are known (e.g., Manga and Brodsky, 2006), the question remains, how might one discern from the geological record whether an eruption was tectonically triggered? Tectonic processes may also be a key to understanding what controls syneruptive propagation of dikes (e.g., Bursik et al, 2003) and the vigor of magma withdrawal once an eruption has begun (e.g., Costa et al, 2011). Few theoretical models that invoke internal (magmatic) eruption triggers (e.g., overpressure and gas saturation; Blake, 1984) can explain the dynamic stop-start nature of activity inferred for some supereruptions (e.g., Oruanui, Huckleberry Ridge Tuff; Wilson, 2001Wilson, , 2008, which may instead refl ect external controls.…”

Elastic source model of the North Mono eruption (1325–1368 A.D.) based on shoreline deformation

“…The boundary element method has been used to investigate the interaction of cracks in an elastic medium (Dieterich Bursik et al (2003) and Decker 1975; Pollard and Holzhausen 1979;Segall and Pollard 1980). The method can reveal important information regarding the geometric parameters of a deformation source (width, height, depth to center, and inclination) as well as the mechanical parameters of source and host (driving pressure and rock stiffness).…”