Data Services Newsletter

Volume 7 : No 3 : September 2005

USArray at the IRIS DMC

Background

USArray is the seismological component of the large EarthScope project (http://www.earthscope.org/). USArray itself has three sub-components, the Backbone, Transportable and Flexible Arrays. Data can be requested from the DMC on a per-component basis using the virtual network codes: _US-BB, _US-TA and _US-FA (respectively for each Array). More information is available here: http://www.earthscope.org/usarray/

Status Update

Currently the DMC is collecting data in real-time from 17 USArray Backbone stations and 100 Transportable Array stations and data from 3 Flexible Array experiments has been archived. The real-time collection amounts to approximately 1.3 gigabytes per day of raw time series data, the bulk of which is standard USArray 40 Hz and 1 Hz seismic waveforms. The Backbone consists of 13 ANSS (US) stations and 4 AFTAC (IM) stations. The Transportable Array consists of 40 newly installed (TA) stations, 40 Caltech (CI) stations, 18 Berkeley (BK) stations, 2 ANZA (AZ) stations and soon stations from UNR (NN). Current station maps and lists are available from the DMC here: http://ds.iris.edu/earthscope/usarray/

New Personnel

In order to handle the increasing amount of USArray data two new DMC staff members were added this year to the USArray data analyst team: Dr. Peggy Johnson and Dr. Mary Templeton bringing the team total to three.

Quality Control

In cooperation with network operators the DMC performs quality control on all USArray data arriving at the data center. This quality control includes everything from validating the accuracy of metadata to continuously monitoring incoming waveforms. The USArray data analyst team manually applies various methods to assess data quality. There will soon be too much data for the team to ever look at all of it. For this reason the QC procedures will always be a combination of automated problem detection systems and manual methods.

All data arriving in real-time at the DMC is processed by our Quality Analysis Control Kit (QUACK) which applies numerous measurements to the raw data. All results from QUACK are available on the web in an integrated interface:

USArray QUACK interface
Figure 1: IRIS DMC QUACK interface showing data from USArray station 109C.

For the DMC USArray data analysts QUACK often provides the first indication that something is wrong with a station. QUACK is continually being refined to allow more accurate identification and useful reporting of data problems.

While QUACK is a great workhorse for deriving data parameters it does not address the problem of low-latency, real-time data monitoring. For this purpose we have recently installed SeisNetWatch, a product from ISTI (http://www.isti.com/). This system allows the DMC to constantly monitor the status of all USArray stations delivering data in real-time.

USArray SeisNetWatch interface
Figure 2: ISTI SeisNetWatch interface to USArray station state-of-health. The DMC uses SeisNetWatch to constantly monitor the status of USArray stations in near real-time.

All detected data problems are reported upstream to the network operators. When appropriate Data Problem Report is issued and archived at the DMC.

by Chad Trabant (IRIS Data Management Center)

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