West Coast/Alaska
Tsunami Warning Center
Operations Manual
NOAA/NWS/WCATWC
Palmer,
http://wcatwc.arh.noaa.gov
Section
4.1: EarlyBird Overview and Module Description
Last Updated:
8/2010
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WC/ATWCs 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.
Earlybird builds on several iterations of processing
software previously 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
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 TsunamiNet, digital broadband data
transmitted over the internet, and digital data transmitted via a private VSAT
system. Data are exported to other
centers using the TsunamiNet 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.
Five 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 three 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.
Waveforms are first placed in the SCNL_RING.
Here duplicates are filtered out and the
information either decimated or copied as is into the WAVE_RING.
The modules perform the following basic
functions: 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.
Data from 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.
s 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 CWorm and IWorm. 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,
·
startstop -start and restart all
modules when necessary, and
·
wftimefilter – filter out
duplicate and out of order packets.
Several locally-developed 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.
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
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).
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.