Tree-ring dated landslide movements and their relationship to seismic events in southwestern Montana, USA

To determine periods of incremental landslide movement and their possible relationship to regional seismic events, the tree-ring records of 32 tilted and damaged conifers at three sites on landslides in the Gravelly Range of southwestern Montana were examined. Several signs of disturbance in the tree-ring record indicating landslide movement were observed. Commonly, the tree-ring record displayed a marked reduction in annual ring width and/or the reaction wood formation. The tree-ring records from the three landslide sites indicate multiple periods of movement during the 20th century. Many of the periods of movement indicated by the strongest signals (most trees) at the sites occurred the year following significant earthquakes in the region. Those seismic events for which evidence in the tree-ring record was found at one or more of the three sites are the 1983 Borah Peak, 1959 Hebgen Lake, 1935 Helena, 1925 Clarkson, and 1908 Virginia City earthquakes. This study suggests that many of the landslide movements were triggered by, or are coincident with, earthquakes as much as 200 km from the study area.     

Wide-Field Camera for Gravitational Microlensing Survey: MOA-cam2

We have constructed a large, mosaic CCD camera called MOA-cam2 which has 4096 × 6144-pixelsto search for gravitational microlensing events. MOA-cam2 has three4096 × 2048-pixel SITe CCD chips, which have a very high quantum efficiency (nearly 80% in the wave region 500 to 800 nm),and three buttable sides. We have placed the threechips side by side with 100 m dead space. MOA-cam2 has been installed on the 61 cm Boller and Chivens telescope of the MOA collaboration at the Mt. John University Observatory (MJUO) in NewZealand since July 1998. The field coverage is 0.92° × 1.38° per exposure. The technical details of MOA-cam2 and the first images obtained with the Boller and Chivens telescope are presented. MOA-cam2 introduces a second phase of research on gravitational microlensing by the MOA collaboration.     

The importance of choosing precipitation datasets

Precipitation data are important for hydrometeorological analyses, yet there are many ways to measure precipitation. The impact of station density analysed by the current study by comparing measurements from the Missouri Mesonet available via the Missouri Climate Center and Community Collaborative Rain, Hail, and Snow (CoCoRaHS) measurements archived at the program website. The CoCoRaHS data utilize citizen scientists to report precipitation data providing for much denser data resolution than available through the Mesonet. Although previous research has shown the reliability of CoCoRaHS data, the results here demonstrate important differences in details of the spatial and temporal distribution of annual precipitation across the state of Missouri using the two data sets. Furthermore, differences in the warm and cold season distributions are presented, some of which may be related to interannual variability such as that associated with the El Niño and Southern Oscillation. The contradictory results from two widely‐used datasets display the importance in properly choosing precipitation data that have vastly differing temporal and spatial resolutions. With significantly different yearly aggregated precipitation values, the authors stress caution in selecting 1 particular rainfall dataset as conclusions drawn could be unrepresentative of the actual values. This issue may be remediated by increased spatiotemporal coverage of precipitation data.     

Ground truthed performance of single‐and dual‐polarized radar rain rates at large ranges

Radar accuracy in estimating qualitative precipitation estimation at distances larger than 120 km degrades rapidly because of increased volume coverage and beam height. The performance of the recently upgraded dual‐polarized technology to the NEXRAD network and its capabilities are in need of further examination, as improved rainfall estimates at large distances would allow for significant hydrological modelling improvements. Parameter based methods were applied to radars from St. Louis (KLSX) and Kansas City (KEAX), Missouri, USA, to test the precision and accuracy of both dual‐ and single‐polarized parameter estimations of precipitation at large distances. Hourly aggregated precipitation data from terrestrial‐based tipping buckets provided ground‐truthed reference data. For all KLSX data tested, an R(Z,ZDR) algorithm provided the smallest absolute error (3.7 mm h^?1) and root‐mean‐square‐error (45%) values. For most KEAX data, R(ZDR,KDP) and R(KDP) algorithms performed best, with RMSE values of 37%. With approximately 100 h of precipitation data between April and October of 2014, nearly 800 and 400 mm of precipitation were estimated by radar precipitation algorithms but was not observed by terrestrial‐based precipitation gauges for KLSX and KEAX, respectively. Additionally, nearly 30 and 190 mm of measured precipitation observed by gauges were not detected by the radar rainfall estimates from KLSX and KEAX, respectively. Results improve understanding of radar based precipitation estimates from long ranges thereby advancing applications for hydrometeorological modelling and flood forecasting. Copyright © 2016 John Wiley & Sons, Ltd.     

Chandra X-ray observations of two unusual BAL quasars

We report sensitive Chandra X-ray non-detections of two unusual, luminous Iron Low-Ionization Broad Absorption Line Quasars (FeLoBALs). The observations do detect a non-BAL, wide-binary companion quasar to one of the FeLoBAL quasars. We combine X-ray-derived column density lower limits (assuming solar metallicity) with column densities measured from ultraviolet spectra and CLOUDY photoionization simulations to explore whether constant-density slabs at broad-line region densities can match the physical parameters of these two BAL outflows, and find that they cannot. In the “overlapping-trough” object SDSS J0300+0048, we measure the column density of the X-ray absorbing gas to be N_H ? 1.8 × 10²⁴ cm^?2. From the presence of Fe ii UV78 absorption but lack of Fe ii UV195/UV196 absorption, we infer the density in that part of the absorbing region to be n_e ? 10⁶ cm^?3. We do find that a slab of gas at that density might be able to explain this object’s absorption. In the Fe iii-dominant object SDSS J2215–0045, the X-ray absorbing column density of N_H ? 3.4 × 10²⁴ cm^?2 is consistent with the Fe iii-derived N_H ? 2 × 10²² cm^?2 provided the ionization parameter is log U > 1.0 for both the n_e = 10¹¹ cm^?3 and n_e = 10¹² cm^?3 scenarios considered (such densities are required to produce Fe iii absorption without Fe iiabsorption). However, the velocity width of the absorption rules out its being concentrated in a single slab at these densities. Instead, this object’s spectrum can be explained by a low density, high ionization and high temperature disk wind that encounters and ablates higher density, lower ionization Fe iii-emitting clumps.     

Automatic Graben Detection in Lunar Images Using Hessian Technique

Lunar surface exploration is increasing rapidly with priority being given to precision of lunar soft landing. Lunar soft landing is achieved when craters and grabens are used as navigational landmarks. Grabens are formed from localized tensional stress fields or from near-surface dike emplacement. These tectonic features tend to have consistently straight or accurate parallel-striking walls bounded by steep, inward-dipping normal faults. Aiming at navigational application, a novel approach for automatic graben detection based on Hessian technique has been implemented on Digital Terrain Model (DTM) of lunar image. The Hessian technique uses gradient change as a key parameter to identify grabens. Adaptive Binarization using Otsu method is used to extract graben features from the Hessian image. Features such as small grabens and craters are removed using morphological operations, resulting in significant appearance of grabens. The experiment is conducted in different DTM images of lunar surface and the results indicate 90 % of the grabens are detected. The statistical results are evaluated based on visual interpretation, for both automatic and manual graben detection. It is observed that the proposed automatic graben detection technique gives better results than the manual detection.     

Secondary Ion Mass Spectrometry Analyses of Diamond and Moissanite in Ophiolite

The Cameca 1280-HR large geometry SIMS instrument is a highly versatile analytical tool which can support a broad range of geochemical applications.Research using the Potsdam 1280 instrument focuses primarily on isotope ratio determinations in geomaterials.Optimized measurement protocols have already been established forδ18O determinations in zircon,and we are also working towards routine oxygen isotope determinations for quartz,calcite,mica,apatite and titanite.The primary challenge in developing such measurement systems are the identification and characterization of suitable reference materials(RMs),and this is made particularly challenging due to the matrix dependent ion yields of the SIMS ion source.Here we wish to report our progress towards establishing new analytical protocols for the determination ofδ13C in both diamond and moissanite.In the case of diamond,our facility possesses three natural RMs with which we are able to produce data with a typical analytical repeatability of~0.15‰(1sd).An inter-comparison of our three diamond RMs demonstrates an overall data quality of better than 0.5‰in terms of systematic offset between the various materials characterized using gas source mass spectrometry(Palot et al.,2012).A single suchδ13C determination in diamond requires 80 s of data acquisition and involves a test portion mass of~400 pgof material.In-house diamond reference materials forδ15N calibration allow us to measure this isotopic system to a total analytical uncertainty of±1.6‰(1sd)at nitrogen concentrations reaching down to 250μg/g.Due to the relatively low abundance of nitrogen in diamonds,such isotope ratio determinations require around 9 minutes of data collection.With respect toδ13C determinations in moissanite,we use a kimberlitic Si C as calibrant(Mathez et al.,1995),on which we achieve a repeatability of~0.2‰(1sd)on a~350 pg test portion mass.Total data acquisition time for such measurements is 80 s.We are currently in the process of developing a second moissanite RM based on a synthetic,coarse-grained powder.We will also investigate this new material for itsδ30Si characteristics.