Chile is one of the world's most seismically active regions and is therefore extensively studied by the earthquake sciences. The great length of the country hosts a variety of measurement systems allowing for the characterization of earthquake processes over a wide range of timescales and in different phases of the seismic cycle. Starting in the early 1990s, several research groups began to deploy continuously operating geodetic networks in Chile, forming the core of the modern network of Global Navigation Satellite Systems (GNSS) receivers used to monitor geodynamics from the southern tip of the Americas to the central Andes. Today, the Centro Sismologico Nacional (CSN) of the Universidad de Chile maintains and improves this network, increasing its coverage and spatial density while greatly reducing solution latency. We present the status of the GNSS network, its data streams, and the real-time analysis system used to support real-time modeling of earthquakes. The system takes 2 s, on average, to collect raw data, estimate positions, and stream results. Such low latency is essential to enabling early warning of earthquakes and tsunamis in Chile.

Over the last decade, the 1-sample-per-second kinematic Global Positioning System (GPS) has been used as a displacement sensor in earthquake observations and for structural health monitoring. Many researchers in both seismology and engineering have expressed the desire for higher-sample-rate (10-sample-per-second or higher) GPS data to acquire high-frequency displacement information, We performed several shake table tests of GPS observation on 29 April, 2009 for the purpose of evaluating the performance of high rate kinematic GPS, We found that the accuracy of high rate kinematic GPS depended on antenna movement, but was independent of receiver sampling rate, The errors in kinematic GPS measurements during the periods of strong shaking were systematically larger than those during the static periods, Furthermore, we found that these large errors were coincident with large accelerations and jerks in the motions experienced by the GPS receivers and antennas, Observations from the 2010 earthquake in Maule, Chile (M 8.8) indicated that strong ground motions can degrade the accuracy of high rate kinematic GPS measurements. Significant jerks and/or accelerations can cause GPS units to temporarily lose tracking on satellite signals and lead to gaps in GPS-recorded seismograms.

In December, 2005, the L2C signal was introduced to improve the accuracy, tracking and redundancy of the GPS system for civilian users. The unencrypted L2C code can be tracked with civilian receivers without correlation. The L2C signal provides a 6-12 dB-Hz SNR improvement over L2P(Y) legacy signal, and a small improvement over L1 C/A-code, which allows for better tracking in marginal signal conditions. With the recent launches of the first block II-F satellites (SVN62/PRN25; SVN63/PRN01), there are 9 healthy satellites broadcasting L2C signals. Seven Block IIR-M satellites also broadcast the L2C signal.

Aims:This study was to investigate the methanogenic community in a biogas reactor from start-up to acidification conditions. Furthermore, reliability and accuracy of the applied quantitative real-time PCR method (Q-PCR) was briefly evaluated.Methods and Results:A mesophilic (37 degrees C), maize silage fed, continuously stirred tank reactor was surveyed. It was operated semi-continuously with increasing daily organic loading rates (OLRs) to reach acidification. Gas production and organic acid composition were measured. Methanogenic community structure was determined by 16S rDNA-based Q-PCR to estimate the abundance of key methanogenic micro-organisms. 16S rDNA of hydrogenotrophic Methanobacteriales was most abundant at OLRs of >= 3 center dot 7 g dry organic matter (DOM) l-1 day-1. By contrast, that of aceticlastic Methanosaetaceae predominated at lower OLRs but disappeared at OLRs of >= 4 center dot 1 g DOM l-1 day-1. At the same OLR, the propionate concentration increased dramatically indicating the acidification of the digester. Application of internal standards to examine Q-PCR's accuracy revealed that the detected amount of 16S rDNA may vary within one log cycle.Conclusions:These results suggest that the absence of Methanosaetaceae might be taken as biological indicator for process' instability. Inhibitory effects on Q-PCR analyses could not be determined based on the spiking experiments.Significance and Impact of the Study:In this study, reactors' microbiology was observed over time using Q-PCR. Insights into the abundance of different methanogens might be used to improve the performance of biogas reactors.