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Wang, MH, Wang JX, Bock Y, Liang H, Dong DA, Fang P.  2019.  Dynamic mapping of the movement of landfalling atmospheric rivers over Southern California with GPS data. Geophysical Research Letters. 46:3551-3559.   10.1029/2018gl081318   AbstractWebsite

Atmospheric rivers (ARs) are long, narrow, and transient corridors of strong horizontal water vapor transport that can result in heavy precipitation. Measuring the movement of these concentrated water vapor bands is important in gaining better insight into AR characteristics and forecasts of AR-caused precipitation. We describe a method to dynamically map the movement of landfalling ARs. The method utilizes high-rate GPS observations from a dense network to derive isochrones that represent the AR arrival time over specific locations. The generated isochrones show that the three ARs, during landfall over Southern California in January 2017, moved southeastward and took about 10 hr to pass over the study area. Overlaying the topography with isochrones reveals that the Peninsular Ranges slow the movement of the landfalling ARs. The large spacing between two adjacent isochrones, reflecting fast AR movement, is closely related to the increased hourly rain rate. Plain Language Summary Atmospheric rivers (ARs), "rivers in the sky," are "rivers" of water vapor rather than liquid water. The landfall of ARs can cause extreme rainfall that in turn induces disasters. We present a method with a dense high-rate GPS network to capture the movement of the landfalling ARs over Southern California. For the three landfalling AR cases in January 2017, results show that the ARs moved southeastward and the durations of AR passing over the study area were about 10 hr. The results also reveal that the landfalling AR movement is affected by local terrain and the fast AR movement is closely related to the large hourly rain rate. The use of the method provides a way to study ARs with high spatial-temporal resolution, which is important in gaining better insight into the forecasts of AR-caused rainfall.

Goldberg, DE, Bock Y.  2017.  Self-contained local broadband seismogeodetic early warning system: Detection and location. Journal of Geophysical Research-Solid Earth. 122:3197-3220.   10.1002/2016jb013766   AbstractWebsite

Earthquake and local tsunami early warning is critical to mitigating adverse impacts of large-magnitude earthquakes. An optimal system must rely on near-source data to maximize warning time. To this end, we have developed a self-contained seismogeodetic early warning system employing an optimal combination of high-frequency information from strong-motion accelerometers and low-frequency information from collocated Global Navigation Satellite Systems (GNSS) instruments to estimate real-time displacements and velocities. Like GNSS, and unlike broadband seismometers, seismogeodetic stations record the full waveform, including static offset, without clipping in the near-field or saturating for large magnitude earthquakes. However, GNSS alone cannot provide a self-contained system and requires an external seismic trigger. Seismogeodetic stations detect Pwave arrivals with the same sensitivity as strong-motion accelerometers and thus provide a stand-alone system. We demonstrate the utility of near-source seismogeodesy for event detection and location with analysis of the 2010 M(w)7.2 El Mayor-Cucapah, Baja, California and 2014 M(w)6.0 Napa, California strike-slip events, and the 2014 M(w)8.2 Iquique, Chile subduction zone earthquake using observatory-grade accelerometers and GPS data. We present lessons from the 2014 M(w)4.0 Piedmont, California and 2016 M(w)5.2 Borrego Springs, California earthquakes, recorded by our seismogeodetic system with Micro-Electro Mechanical System (MEMS) accelerometers and GPS data and reanalyzed retrospectively. We conclude that our self-contained seismogeodetic system is suitable for early warning for earthquakes of significance (>M5) using either observatory-grade or MEMS accelerometers. Finally, we discuss the effect of network design on hypocenter location and suggest the deployment of additional seismogeodetic stations for the western U.S.

Granat, R, Parker J, Kedar S, Dong DA, Tang BY, Bock Y.  2013.  Statistical Approaches to Detecting Transient Signals in GPS: Results from the 2009-2011 Transient Detection Exercise. Seismological Research Letters. 84:444-454.   10.1785/0220130039   AbstractWebsite