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J.W. Baker

Publications and source records attributed to J.W. Baker.

5 recordsLinked to original sources
USGS2014

Rapid earthquake characterization using MEMS accelerometers and volunteer hosts following the M 7.2 Darfield, New Zealand, Earthquake

We test the feasibility of rapidly detecting and characterizing earthquakes with the Quake‐Catcher Network (QCN) that connects low‐cost microelectromechanical systems accelerometers to a network of volunteer‐owned, Internet‐connected computers. Following the 3 September 2010 M 7.2 Darfield, New Zealand, earthquake we installed over 180 QCN sensors in the Christchurch region to record the aftershock sequence. The sensors are monitored continuously by the host computer and send trigger reports to the central server. The central server correlates incoming triggers to detect when an earthquake has occurred. The location and magnitude are then rapidly estimated from a minimal set of received ground‐motion parameters. Full seismic time series are typically not retrieved for tens of minutes or even hours after an event. We benchmark the QCN real‐time detection performance against the GNS Science GeoNet earthquake catalog. Under normal network operations, QCN detects and characterizes earthquakes within 9.1 s of the earthquake rupture and determines the magnitude within 1 magnitude unit of that reported in the GNS catalog for 90% of the detections.

Darfield↗
USGS2008

Effect of imbalanced nutrients and immigration on Prymnesium parvum community dominance and toxicity: Results from in-lake microcosm experiments

Prymnesium parvum, a haptophyte species, forms harmful blooms, including those that have caused severe fish kills in Texas, USA, over the past 6 yr. We studied P. parvum dynamics using in situ microcosm experiments at Lake Possum Kingdom, Texas, during 3 seasons (fall 2004, winter and spring 2005). Experimental treatments included full and partial nutrient enrichment (encompassing nitrogen [N] and phosphorus [P] deficient treatments), P. parvum immigration and combinations of these factors. In the control and N and P deficient treatments, P. parvum populations dominated the community, but only in the N deficient treatments did P. parvum experience a significant growth in the population. In contrast, when nutrients were not limiting, P. parvum tended to lose its competitive edge to other taxa such as chlorophytes, euglenophytes and diatoms, which then dominated the community. Population growth of P. parvum was also stimulated through immigration, but only during the winter experiment, a period of the year when bloom initiation is common. This finding suggests that movement into the water column may be an important process leading to P. parvum bloom initiation. Toxicity of P. parvum to fish was also affected by the nutrient changes: during conditions of no nutrient addition P. parvum was most toxic; intermediate toxicity was observed under N and P deficient conditions, and full nutrient enrichments resulted in nearly non-toxic conditions. ?? Inter-Research 2008.

Aquatic Microbial Ecology↗
USGS1983

Geochemistry of the Chattanooga shale, Dekalb County, central Tennessee.

This Upper Devonian shale is of interest because of its unusual enrichment in trace elements, especially U; a new chemical analysis for major, minor and trace elements is presented. Stable isotopes of carbon (organic) show delta 13C approx -29per mille and for total sulphur show -21 to -27per mille delta 34S. The organic matter was found to range from dominantly marine (Dowelltown member) to dominantly terrestrial (Gassaway member) by extraction-column chromatography-GS and also by pyrolysis-GS of kerogen. Trace elements U, Mo, Co, Zn, Cu, Ni, V, As and Hg are enriched in the organic- and sulphide-rich units. This enrichment can be related to a euxinic depositional environment, to a very slow sedimentation rate (approx 2 mm/1000 years), to the type of organic matter that varied from mainly marine to terrestrial, and to the source of the metals, which shows abundance variations that originated, at least in part, from volcanic ash layers.-R.S.M.

Southeastern Geology↗