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Jacobeit, E, Thomas C, Vernon F.  2013.  Influence of station topography and Moho depth on the mislocation vectors for the Kyrgyz Broadband Seismic Network (KNET). Geophysical Journal International. 193:949-959.   10.1093/gji/ggt014   AbstractWebsite

Deviations of slowness and backazimuth from theoretically calculated values, the so-called mislocation vectors, are measured for the Kyrgyz Broadband Seismic Network (KNET) in the Tien Shan region. 870 events have been analysed for arrivals of P and PKP waves from all azimuths. The deviations of slowness and backazimuth show a strong trend with values up to 1 s deg(-1) for slowness values for waves arriving from the North and South and backazimuth deviations of, in some cases, more than 10 degrees for waves arriving from the East and West. Calculating the traveltime deviations of the stations for topography of the Tien Shan region and Moho depth values appropriate for this area shows that most slowness and backazimuth deviations can be reduced to very small values. The remaining mislocation vectors show no strong trends and are on average smaller than 0.2 s deg(-1) for slowness and 2 degrees for backazimuth values, which is within the error bars of these measurements. Results from array methods that rely on the knowledge of the backazimuth values show much improved resolution after the correction of the mislocation vectors which shows the importance of knowing and correcting for structures directly beneath arrays.

Jacques, AA, Horel JD, Crosman ET, Vernon FL.  2015.  Central and Eastern US surface pressure variations derived from the USArray Network. Monthly Weather Review. 143:1472-1493.   10.1175/mwr-d-14-00274.1   AbstractWebsite

Large-magnitude pressure signatures associated with a wide range of atmospheric phenomena (e.g., mesoscale gravity waves, convective complexes, tropical disturbances, and synoptic storm systems) are examined using a unique set of surface pressure sensors deployed as part of the National Science Foundation Earth-Scope USArray Transportable Array. As part of the USArray project, approximately 400 seismic stations were deployed in a pseudogrid fashion across a portion of the United States for 1-2 yr, then retrieved and redeployed farther east. Surface pressure observations at a sampling frequency of 1 Hz were examined during the period 1 January 2010-28 February 2014 when the seismic array was transitioning from the central to eastern continental United States. Surface pressure time series at over 900 locations were bandpass filtered to examine pressure perturbations on three temporal scales: meso-(10 min-4 h), subsynoptic (4-30 h), and synoptic (30 h-5 days) scales. Case studies of strong pressure perturbations are analyzed using web tools developed to visualize and track tens of thousands of such events with respect to archived radar imagery and surface wind observations. Seasonal assessments of the bandpass-filtered variance and frequency of large-magnitude events are conducted to identify prominent areas of activity. Large-magnitude mesoscale pressure perturbations occurred most frequently during spring in the southern Great Plains and shifted northward during summer. Synoptic-scale pressure perturbations are strongest during winter in the northern states with maxima located near the East Coast associated with frequent synoptic development along the coastal storm track.

Jacques, AA, Horel JD, Crosman ET, Vernon F, Tytell J.  2016.  The Earthscope US transportable array 1 Hz surface pressure dataset. Geoscience Data Journal. 3:29-36.   10.1002/gdj3.37   AbstractWebsite

A unique set of high temporal frequency surface atmospheric pressure observations have been collected and archived from a large-scale field campaign in the geosciences. The Earthscope U.S. Transportable Array (USArray TA) consists of approximately 400 deployable surface platforms. Stations were deployed in a Cartesian-like gridded fashion across a section of the contiguous United States for 1-2 year then retrieved and redeployed as new platforms further east. While primarily deployed for seismic measurements, platforms also recorded surface atmospheric pressure. These pressure data, collected and stored at a temporal frequency of 1 Hz, have been made available via the Research Data Archive at the National Center for Atmospheric Research (NCAR) for the time period 1 Jan 2010-31 Dec 2015. The 6 years of observations contain data from over 1000 locations ranging from the central to eastern United States, as well as some platforms in Alaska and the northwest United States. Data were organized as annual station files with supplemental metadata and quality control summary files. Several web-based interfaces are also available to rapidly explore the pressure archive. We describe the available dataset with several prominent atmospheric events shown as usage examples.

Jacques, AA, Horel JD, Crosman ET, Vernon FL.  2017.  Tracking Mesoscale Pressure Perturbations Using the USArray Transportable Array. Monthly Weather Review. 145:3119-3142.   10.1175/mwr-d-16-0450.1   AbstractWebsite

Mesoscale convective phenomena induce pressure perturbations that can alter the strength and magnitude of surface winds, precipitation, and other sensible weather, which, in some cases, can inflict injuries and damage to property. This work extends prior research to identify and characterize mesoscale pressure features using a unique resource of 1-Hz pressure observations available from the USArray Transportable Array (TA) seismic field campaign. A two-dimensional variational technique is used to obtain 5-km surface pressure analysis grids every 5 min from 1 March to 31 August 2011 from the TA observations and gridded surface pressure from the Real-Time Mesoscale Analysis over a swath of the central United States. Bandpass-filtering and feature-tracking algorithms are employed to isolate, identify, and assess prominent mesoscale pressure perturbations and their properties. Two case studies, the first involving mesoscale convective systems and the second using a solitary gravity wave, are analyzed using additional surface observation and gridded data resources. Summary statistics for tracked features during the period reviewed indicate a majority of perturbations last less than 3 h, produce maximum perturbation magnitudes between 2 and 5 hPa, and move at speeds ranging from 15 to 35ms(-1). The results of this study combined with improvements nationwide in real-time access to pressure observations at subhourly reporting intervals highlight the potential for improved detection and nowcasting of high-impact mesoscale weather features.

Johnson, CW, Vernon F, Nakata N, Ben-Zion Y.  2019.  Atmospheric processes modulating noise in Fairfield nodal 5 Hz geophones. Seismological Research Letters. 90:1612-1618.   10.1785/0220180383   AbstractWebsite

Atmospheric processes are documented to modulate seismic noise in Fairfield Nodal three-component geophones. Spectral analysis has shown high-amplitude signals between 40 and 50 Hz in all waveforms inspected. The changes in spectral amplitudes and frequency are found to be modified by daily variations in wind velocity and temperature, which are temporally correlated for much of the study. The wind velocity is shown to affect a wide spectral band with peak amplitudes that depend on the distance from in situ structures coupling wind energy into the shallow crust. The wind velocity increases the spectral amplitudes, most noticeably in the 40-50 Hz band; it produces a 15 Hz frequency modulation in the conditions of highest wind, with resonance frequencies up to 150 Hz. These signals likely reflect a superposition of multiple local and regional sources producing wind-generated ground motions and nonlinear wave propagation in the shallow subsurface. During periods of temperatures below 0 degrees C, a similar frequency modulation is observed, but the amplitudes are not as pronounced without the elevated wind velocity. A possible source of the continuous noise signal and the temperature-dependent frequency modulation is the spike mount that is attached to the nodal housing. The noise signals modulated by the wind and temperature variations require installation procedures in order to mitigate the effects of the contaminating noise on the geophysical processes of interest.