Monitoring a Passive Seismic Network at Neal Hot Springs Geothermal Plant

The Neal Hot Springs Project, currently under construction, will produce 23 MW of geothermal electric power once online. The project is located near Vale, Oregon (approx. 90 miles northwest of Boise) and consists of about 9.6 square miles of land, which is leased by U.S. Geothermal Inc. During construction the Geosciences department at Boise State University set up a network of 11 passive seismic stations in the area to monitor seismic activity. The goal is to obtain a large collection of seismic data during construction and testing, and to continue seismic monitoring during production. The data will be used to determine natural seismic activity, if any, in the area, seismic activity directly related to testing and production, and to determine the effects of fluid flow in the subsurface. These data sets may also be useful in targeting future geothermal reservoirs within the project area

The Incidence and Magnitude of Tooth-Size Discrepancies in Caucasians, Blacks and Hispanics

The present investigation utilized the Bolton Analysis to determine the incidence and magnitude of tooth-size discrepancy in a sample of 227 orthodontic patients. Sliding calipers were used to measure the mesiodistal width of the permanent dentition on pretreatment study models of 120 Caucasian, 51 Black, and 56 Hispanic patients. The overall and anterior ratios were analyzed and the frequency and magnitude of excess maxillary and mandibular tooth structure was determined. Each racial group demonstrated a significant incidence of tooth-size discrepancy in the maxillary and mandibular arches of a magnitude (\u3e 0.5mm) which would require some form of correction. In addition, one-way analysis of variance revealed the mean overall ratio for Blacks was significantly different than the mean overall ratio for Caucasians and Hispanics. Key words: Bolton Analysis, tooth-size discrepancy, tooth-size analysis, mesiodistal width, dental biometric

Experimental Study of Salt Bead Dissolutions in Aqueous Solvents

Bead dissolutions of several chloride compoundslithium chloride-potassium chloride (LiCl-KCl) eutectic, lithium chloride (LiCl), strontium chloride (SrCl₂), cerium chloride (CeCl₃), lanthanum chloride (LaCl₃), praseodymium chloride (PrCl₃), and yttrium chloride (YCl₃)were performed in water at 20 °C. Additional bead dissolutions involved LiCl-KCl beads in two types of brine solvents. Each bead diameter was measured and found to change linearly with time in water. A model regression to these measured data resulted with <i>R</i>² > 0.942. Results indicated dissolution was faster in water than in the brines. Calculated mass transfer coefficients were in the range of 1.00 × 10^–2 mm s⁻¹ to 2.67 × 10^–2 mm s⁻¹. Based on a Sherwood correlation, <i>Sh</i> = 2 + 0.0254<i>Gr</i>^0.333<i>Sc</i>^0.577, calculated diffusion coefficients were in the range of 10^–5 mm² s⁻¹ to 10^–3 mm² s⁻¹. Results implied mass transfer of the eutectic was dominated by diffusion, whereas a transition from natural convection to diffusion was inferred for the other solutes

Seismic Investigation of the Neal Hot Springs Geothermal Area

Neal Hot Springs (NHS) is an active geothermal site and home to a 23MW geothermal electric power plant that is now online and producing at full capacity. The site is located near Vale, Oregon (approx. 145 km Northwest of Boise) and consists of about 25 square kilometers of land which is leased by U.S. Geothermal Inc. In May 2011, students and faculty of the Boise State University geophysics field camp set up a network of 11 seismic stations in the area to monitor seismic activity related to geothermal production and natural seismicity. The network continuously recorded data until it was decommissioned in November 2012. The network obtained continuous seismic recordings during construction and testing of the power plant facility, and continued seismic recording during production. We are using the data to establish a datum of global, regional, and local natural seismicity and we are analyzing the data to identify seismic activity directly related to geothermal testing and production. Currently, our results show that the area surrounding Neal Hot Springs Geothermal Plant exhibits very little natural seismic activity, unusual for a geothermal system. With a nearly two year dataset, we have identified two small magnitude earthquakes within the vicinity of NHS. We have yet to establish the link between these two earthquakes and geothermal activities at NHS, but we have established that both events took place within a few kilometers of the site. Our preliminary conclusion is that these earthquakes are likely from the nearby Cottonwood Mountain fault that shows compelling evidence for late Quaternary motion. This fault is one of many northwest-trending active faults within eastern Oregon. We have not confirmed any seismic activity induced by the power plant thus far, but ongoing analysis from our May 2011 to November 2012 seismic data will help identify small seismic events near NHS that are either related to the Cottonwood Mountain fault or related to geothermal production at NHS. Our results will place constraints on local seismicity that will enable us to better understand hazards and stresses related to active faults or geothermal production