West Coast/Alaska Tsunami Warning Center

Operations Manual

NOAA/NWS/WCATWC

910 South Felton Street

Palmer, Alaska 99645

http://wcatwc.arh.noaa.gov

 

 

Section 4.1: EarlyBird Overview and Module Description

 

Last Updated: 11/2009

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WC/ATWC’s EarlyBird seismic data processing system is used for both real-time and post-processing of seismic data.  EarlyBird is a combination of standard Earthworm modules (Johnson, et al., 1995) and WC/ATWC-developed earthworm modules. 

Several iterations of processing software have been developed at the WC/ATWC (Sokolowski, et al., (1983); Sokolowski, et al., (1990); and Zitek, et al., (1990); Whitmore and Sokolowski, (2002)). EarlyBird automatically locates and sizes (using Mb, Ml, MS, Mw, and Mwp) worldwide, regional, and local earthquakes. Graphical interfaces for the earthworm modules have been created to allow interactive additions and changes to automatically computed parameters during initial earthquake processing or after-the-fact. Real-time data can be monitored and interacted with directly through earthworm modules. Data logged to disk by the system can be analyzed immediately after logging through stand-alone analysis programs. The automatically computed seismic parameters are interfaced with the tsunami message generation software and the EarthVu geographic information system (Section 4.3).

The Earthworm software was initially installed at the WC/ATWC through NOAA's National Tsunami Hazard Mitigation Program. One aspect of this program was to enhance the tsunami warning centers with seismic data from networks operated by regional earthquake centers. The USGS implemented this task in the late 1990s and chose Earthworm as the standard for seismic data and hypocenter parameter exchange.

The seismic network utilized by the EarlyBird system is discussed in detail in Section 2.3. Incoming seismic data are distributed throughout the center as shown in Section 3.2.  Seismic data arrives at the WC/ATWC by four basic paths: digital broadband data via leased circuits, digital broadband data transmitted via the CrestNet, digital broadband data transmitted over the internet, and digital data transmitted via a VSAT system.  Data is exported to other centers using the CrestNet or internet.

A separate PC is used to acquire data from each path and to export data and hypocenters to other centers.  Connections between import/export and processing systems are shown in the attached figure (which also links to earthworm ring and module diagrams).  Switches, routers, PCs, and data paths are configured to eliminate any single points of failure. 

A network of ten Windows XP-based PCs comprise the EarlyBird seismic processing system.  Six PCs, as described above, import and export data using standard Earthworm modules.  Two of the remaining PCs are the main and backup seismic data processors. Both constantly monitor earthquake activity on approximately 350 seismic channels.  The last two PCs are used for training/development and large screen display.



The figure above displays the data processing flow within EarlyBird1.  Earthworm rings are shared memory locations.  The windows icons indicate modules which accommodate user interaction and review.  Both trace data and processed hypocenters from other observatories are first placed in the INPUT_RING.  Here, the information is either decimated or copied as is into the WAVE_RING.  The hypocenter information is manipulated by the Hypo_print module for display in EarthVu.  The rest of the modules operate on the trace data.  Latency_mon keeps track of data outages and latencies.  Disk_wcatwc logs all trace data to disk.  This data is immediately available for review by Analyze, and modules Hypo_display, Lpproc, Mm, and Mtinver.  Typically two weeks worth of data is saved on disk.  Large quakes are archived through Analyze.  Module Pick_wcatwc analyzes the signal to determine the onset of an earthquake.  Once a pick has been made, the signal is further analyzed to determine Mb, Ml, and Mwp magnitude parameters.  Module Develo displays the real-time signal in a similar fashion as an old-fashioned develocorder.  Develo displays P-picks made in Pick_wcatwc and allows the user to add or refine pick data to earthquakes presently being processed.  Develo also analyzes the signal to look for strong earthquakes.  Alarms are triggered when parameters have been exceeded.  The P-picks made in Pick_wcatwc are sent to the PICK_RING .  Module Loc_wcatwc ingests these P-picks and automatically locates the events.  Alarms can be triggered in Loc_wcatwc based on location and size.  The earthquake locations and magnitude information is sent to HYPO_RING.  Module Hypo_display summarizes this information and displays a GUI which allows a user to modify P data (which is re-sent to Loc_wcatwc for refinement).  When a large earthquake occurs (M>5), long period and broadband data are processed to refine the magnitude estimate.  Broadband data in WAVE_RING is decimated to 1 sample/second and placed in WAVE_RING_LP.  Modules Lpproc, Mm, and Mtinver operate on these data to determine Ms, Mw, moment tensor, and fault plane solutions.  Hypocenter information is exported from the HYPO_RING to other centers through Worm3.  Each of these modules is described in greater detail below.

EarlybIrd uses the following standard Earthworm modules:

·         adsend - digitize analog data,

·         copystatus - copy errors/heartbeats from one ring to another,           
decimate - filter and reduce the sample rate of data for export and processing,

·         export_generic/scn - send hypocenter and trace data to other centers,

·         import_generic - gather hypocenter and trace data from other centers,

·         import_ida - receive data from the IRIS/IDA network into Earthworm,

·         liss2ew - receive data from the IRIS/ASL network into Earthworm,

·         ringdup_scn/generic - copy messages from one ring to another,

·         statmgr - monitor modules attached to a ring, and

·         startstop -start and restart all modules when necessary.


Several local Earthworm modules are also used and are discussed in greater detail in the links:

·         analyze - read, display, and analyze seismic data previously logged to disk, and archive data to CD-ROM,

·         atplayer – simulate real-time events with older data,

·         develo - display real-time, short period seismic data in develocorder type view,

·         disk_wcatwc - log trace data to disk,

·         dumptide - log certain channels to disk (tide gage data), 

·         hypo_display - display computed hypocenter parameters and adjust P data,

·         hypo_print - log hypocenters to disk and EarthVu,

·         latency_mon - track data outages and latencies for all channels,

·         locate - interactively locate earthquakes detected in automatically or interactively, trigger LP processing in lpproc or analyze for MS and Mw, and display location and P data to screen,

·         loc_wcatwc - associator/locator module,

·         lpproc - display real-time, long period seismic data and process data for MS,

·         mm - process surface wave data for Mm (Mw),

·         mtinver - process data for moment tensor,

·         page_alarm - send alarm messages through various interfaces, and

·         pick_wcatwc - P-picking/magnitude determination algorithm.

·         summary - display earthquake summary and procedures to monitor.

 

One other non-Earthworm-based program is used to generate tsunami products:

·         MESSAGE2 - create tsunami warning and other messages, and

 

Initialization files for earthworm-based modules are saved in the /twc-ops/earthworm/run/params directory, and are suffixed with .d. 

 

Data are shared between the programs through shared memory, disk files, and semaphores.  The earthworm system is modular.  If one module breaks, the others should not be affected.  The earthworm module statmgr monitors the modules and will restart them if necessary.  The earthworm startstop module starts and stops the earthworm modules, and gives status of each.

All of the programs, including the Earthworm-based components of EarlyBird, run on a PC with a graphics adapter which splits the screen into twelve monitors. Modules analyze, locate, lpproc, develo, hypo_display, mm, mtinver, summary, and latency_mon also have graphical displays which utilize a monitor. MESSAGE2 brings up a dialog box when activated in locate. The EarthVu system uses the other four monitors.   The EarlyBird system can be run on a single-monitor PC, but data will not be as clear as on a twelve-monitor system.  

References

Buland, R. and C.H. Chapman (1983). The computation of seismic travel times, Bull. Seism. Soc. Am., 73, 1271-1302.

Kennet, B.L.N. (1991). IASPEI 1991 Seismological Tables, pub. by Research School of Earth Sciences, Australian National U., Canberra AU, 167 pp.

Johnson, C.E., A. Bittenbinder, B. Bogaert, L. Dietz, and W. Kohler (1995). Earthworm: a flexible approach to seismic network processing, IRIS Newsletter, 14, 1-4.

Sokolowski, T.J., G.W. Fuller, M.E. Blackford, and W.J. Jorgensen (1983). The Alaska Tsunami Warning Center's automatic earthquake processing system, in Proceedings, 1983 Tsunami Symposium, Hamburg, FRG, August, 1983, 131-147.

Sokolowski, T.J., P.M. Whitmore, and W.J. Jorgensen (1990). Alaska Tsunami Warning Center's automatic and interactive computer processing system, Pure and Applied Geophysics, 134, 163-174.

Whitmore, P.M. and T.J. Sokolowski (2002). Automatic earthquake processing developments at the U.S. West Coast/Alaska Tsunami Warning Center, in Recent Research Developments in Seismology, Transworld Research Network, Kervala, India, 1-13.

Zitek, W.O., A.H. Medbery, and T.J. Sokolowski (1990). Concurrent seismic data acquisition and processing using a single IBM PS/2 computer, NOAA Technical Memorandum NWS AR-41, 20 pp.