The Gondola And The Girl

https://digitalcommons.library.umaine.edu/mmb-vp/3877/thumbnail.jp

Channels Ran Through It—The Lawrence Formation at Lone Star Lake, Douglas County, Kansas

The upper part of the Ireland Sandstone Member of the Lawrence Formation exposed in the spillway of Lone Star Lake, southwest of Lawrence, Kansas, consists of abundant pinstripe-bedded shales and siltstones; thin, lenticular sandstone and siltstone beds; and meter-scale, channel-form sandstone and mudstone lenses. Soft-sediment-deformation structures, including load casts, ball-and-pillow, and pseudonodules are abundant. The lenticular and pinstripe bedding with bipolar paleocurrents suggests tide-influenced deposition. The crosscutting, channel-form deposits are interpreted as tidal channels in an environment with low energy but rapid sedimentation. The depositional environment was a tide-dominated, muddy upper estuary cut by tidal channels. Gravitational instabilities resulting from rapid deposition of sand over saturated mud produced inverse-density gradients that resulted in soft-sediment deformation

Identifying global seismic anisotropy patterns by correlating shear-wave splitting and surface-wave data

International audienceWe compare a global compilation of shear-wave splitting measurements with azimuthal seismic anisotropy parameters inferred from surface-wave tomography. The currently available splitting dataset is taken from a novel comprehensive collection of available publications that is updated interactively online. The comparison between the two types of data is made by calculating predicted splitting parameters from the anisotropic tomography model. Comparing these predicted splitting parameters with the observed ones, we find a considerable correlation between the two datasets at global scale. This result is noteworthy, since such correlation did not seem to exist in previous studies. The spatial resolution associated with the two types of methods is rather different. While surface waves have good vertical resolution and poor lateral resolution of several hundreds of kilometers, SKS splitting measurements have good lateral, but poor vertical resolution. The correlation can be understood in light of recent propositions that anisotropy seen by SKS splitting constrains mostly the upper mantle, and therefore a similar depth region as surface waves. The correlation also confirms the generally good quality of the shear-wave measurements, as well as that of the anisotropic tomography model

Accurate measurement of the time delay in the response of the LIGO gravitational wave detectors

We present a method to precisely calibrate the time delay in a long baseline gravitational-wave interferometer. An accurate time stamp is crucial for data analysis of gravitational wave detectors, especially when performing coincidence and correlation analyses between multiple detectors. Our method uses an intensity-modulated radiation pressure force to actuate on the mirrors. The time delay is measured by comparing the phase of the signal at the actuation point with the phase of the recorded signal within the calibrated data stream used for gravitational wave searches. Because the signal-injection path is independent of the interferometer's control system, which is used for the standard calibration, this method can be an independent verification of the timing error in the system. A measurement performed with the 4 km interferometer at the LIGO Hanford Observatory shows a 1 µs relative accuracy when averaging over 50 min. Our understanding of the systematic time delay in the detector response has reached the level of 10 µs

Blip glitches in Advanced LIGO data

Blip glitches are short noise transients present in data from ground-based gravitational-wave observatories. These glitches resemble the gravitational-wave signature of massive binary black hole mergers. Hence, the sensitivity of transient gravitational-wave searches to such high-mass systems and other potential short duration sources is degraded by the presence of blip glitches. The origin and rate of occurrence of this type of glitch have been largely unknown. In this paper we explore the population of blip glitches in Advanced LIGO during its first and second observing runs. On average, we find that Advanced LIGO data contains approximately two blip glitches per hour of data. We identify four subsets of blip glitches correlated with detector auxiliary or environmental sensor channels, however the physical causes of the majority of blips remain unclear