Bochum, University, Diss., 2003.

No description available.

Precaldera volcanism between 3.2-2.6 M.a. produced a basalt -trachybasalt -trachyandesite -quartz latite suite peripheral to the present Long Valley caldera from a heterogeneous, interactive, deep crustal magmatic -system. The suite consists of ( 1) widespread, predominately porphyritic olivine-augite basalt / trachybasalt / trachyandesite flow sequences (> 24 km³), (2) local orthopyroxene -phyric silicic trachyandesite flows (> I km³), and (3) sparsely -phyric orthopyroxene -hornblende -plagioclase quartz latite dome-flows and coarsely -phyric biotite -hornblende -plagioclase quartz latite dome-flows ( > 4 km³) erupted in that general sequence. Field, petrographic, and major-, minor-, and trace-element, as well as Sr isotopic studies of representative precaldera lavas on the northwest periphery of the caldera suggest that: (I) the basaltic magmas were generated from a lherzolite partial melt modified by minor crystal fractionation (limited fractionation due to their high incompatible element content) and contamination by older sialic rocks or their derivatives (represented by granitic inclusions, quartz xenocrysts, and progressively higher ⁸⁷Sr/⁸⁶Sr, 0.7062 to 0.7067), (2) the silicic trachyandesite was probably the result of intimate mixing of basaltic and quartz latite magmas (reflected in compositional gaps in progressively more silicic bulk compositional trends and the similarity of the quartz latite and silicic trachyandesite initial ⁸⁷Sr/⁸⁶Sr ratios, 0.7070-0.7074), and (3) the quartz latite was derived by crustal melting at different depths (as reflected in the variable ⁸⁷Sr/⁸⁶Sr, 0.7072-0.7095) and underwent radically changing crystallization conditions and contamination by trachyandesite (represented by heterogeneous mineral assemblages, chemistry, and textures indicating changing equilibrium conditions most evident in the trachyandesite enclave-rich quartz latite). The basaltic magmas provided the heat and mass to the crust promoting partial melting and generation of quartz latitic magmas. Synchronous basaltic intrusion and generation of crustal melts interacted and hybridized to yield trachyandesite. The isolated occurrence of trachyandesite enclaves in the youngest quartz latite dome-flows, suggests the disruption of a quartz latite-trachyandesite interface during late stages of the eruptive drawdown of a small volume magmatic system. Heat from continued basaltic input and coalesence of initially separate quartz latite bodies could possibly have resulted in development of the larger silicic magma chamber from which the younger rhyolitic (Glass Mountain-Bishop Tuft) magmas erupted. / M.S.

A description and model of the near-surface hydrothermal system at Casa Diablo, with its implications for the larger-scale hydrothermal system of Long Valley, California, is presented. The data include resistivity profiles with penetrations to three different depth ranges, and analyses of inorganic mercury concentrations in 144 soil samples taken over a 1.3 by 1.7 km area. Analyses of the data together with the mapping of active surface hydrothermal features (fumaroles, mudpots, etc.), has revealed that the relationship between the hydrothermal system, surface hydrothermal activity, and mercury anomalies is strongly controlled by faults and topography. There are, however, more subtle factors responsible for the location of many active and anomalous zones such as fractures, zones of high permeability, and interactions between hydrothermal and cooler groundwater. In addition, the near-surface location of the upwelling from the deep hydrothermal reservoir, which supplies the geothermal power plants at Casa Diablo and the numerous hot pools in the caldera with hydrothermal water, has been detected. The data indicate that after upwelling the hydrothermal water flows eastward at shallow depth for at least 2 km and probably continues another 10 km to the east, all the way to Lake Crowley.

The advent of Global Positioning System (GPS) has revolutionized geodesy with high accuracy, fast speed, simple use, and low cost. This dissertation investigates three topics on volcano and earthquake-related deformation using GPS measurements and models to demonstrate the power of the new generation of geodetic methods. The three topics include the 2002-2003 continued episodic inflation at Long Valley Caldera in eastern California, the coseismic and postseismic response of the energetic 2008 MW 6.4 Achaia-Elia Earthquake in northwest Peloponnese, Greece, and the interseismic megathrust coupling and forearc sliver transport near the Nicoya Peninsula in northwest Costa Rica.

This thesis presents a new GIS-based scenario volcanic risk assessment model called RiskScape Volcano (RSV) that has been designed for the RiskScape program to advance the field of volcanic risk assessment. RiskScape is a natural hazards risk assessment software tool being developed in New Zealand by GNS Science and NIWA. When integrated into RiskScape, RSV will add proximal volcanic hazard risk assessment capability, and enhanced inventory design; it presently operates outside of RiskScape by combining volcanic hazard models’ output spatial hazard intensity (hazard maps) with inventory databases (asset maps) in GIS software to determine hazard exposure, which is then combined with fragility functions (relationships between hazard intensity and expected damage ratios) to estimate risk. This thesis consists of seven publications, each of which comprises a part of the development and testing of RSV: 1) results of field investigation of impacts to agriculture and infrastructure of the 2006 eruption of Merapi Volcano, Indonesia; 2) agricultural fragility functions for tephra damage in New Zealand based on the observations made at Merapi; 3) examination of wind patterns above the central North Island, New Zealand for better modeling of tephra dispersal with the ASHFALL model; 4) a description of the design, components, background, and an example application of the RSV model; 5) test of RSV via a risk assessment of population, agriculture, and infrastructure in the Rotorua District from a rhyolite eruption at the Okataina Volcanic Centre; 6) test of RSV via a comparison of risk to critical infrastructure in Mammoth Lakes, California from an eruption at Mammoth Mountain volcano versus an eruption from the Inyo craters; and 7) a survey of volcanic hazard awareness in the tourism sector in Mammoth Lakes. Tests of the model have demonstrated that it is capable of providing valid and useful risk assessments that can be used by local government and emergency management to prioritise eruption response planning and risk mitigation efforts. RSV has provided the RiskScape design team with a more complete quantitative volcanic risk assessment model that can be integrated into RiskScape and used in New Zealand and potentially overseas.

This thesis presents a new GIS-based scenario volcanic risk assessment model called RiskScape Volcano (RSV) that has been designed for the RiskScape program to advance the field of volcanic risk assessment. RiskScape is a natural hazards risk assessment software tool being developed in New Zealand by GNS Science and NIWA. When integrated into RiskScape, RSV will add proximal volcanic hazard risk assessment capability, and enhanced inventory design; it presently operates outside of RiskScape by combining volcanic hazard models’ output spatial hazard intensity (hazard maps) with inventory databases (asset maps) in GIS software to determine hazard exposure, which is then combined with fragility functions (relationships between hazard intensity and expected damage ratios) to estimate risk. This thesis consists of seven publications, each of which comprises a part of the development and testing of RSV: 1) results of field investigation of impacts to agriculture and infrastructure of the 2006 eruption of Merapi Volcano, Indonesia; 2) agricultural fragility functions for tephra damage in New Zealand based on the observations made at Merapi; 3) examination of wind patterns above the central North Island, New Zealand for better modeling of tephra dispersal with the ASHFALL model; 4) a description of the design, components, background, and an example application of the RSV model; 5) test of RSV via a risk assessment of population, agriculture, and infrastructure in the Rotorua District from a rhyolite eruption at the Okataina Volcanic Centre; 6) test of RSV via a comparison of risk to critical infrastructure in Mammoth Lakes, California from an eruption at Mammoth Mountain volcano versus an eruption from the Inyo craters; and 7) a survey of volcanic hazard awareness in the tourism sector in Mammoth Lakes. Tests of the model have demonstrated that it is capable of providing valid and useful risk assessments that can be used by local government and emergency management to prioritise eruption response planning and risk mitigation efforts. RSV has provided the RiskScape design team with a more complete quantitative volcanic risk assessment model that can be integrated into RiskScape and used in New Zealand and potentially overseas.