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: 5/2007
------------------------------------------------------------------------------------------------------------
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), WC/ATWC-developed earthworm modules,
and stand-alone seismic processing software.
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 eight 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 250 seismic channels. The last PC is a training/development PC
which mirrors the main EarlyBird system.
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 the stand-alone program 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:
·
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,
·
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.
Four
stand-alone, non-Earthworm-based programs are also part of the EarlyBird system
and are described in greater detail in the links:
·
ANALYZE - read, display,
and analyze seismic data previously logged to disk, and archive data to CD-ROM,
·
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,
·
MESSAGE2 - create tsunami
warning and other messages, and
·
SUMMARY - display
earthquake summary and procedures to monitor.
Initialization files for
earthworm-based modules are saved in the earthworm/run/params directory, and
are suffixed with .d. Initialization
files for the stand-alone programs are kept in the same directory as the code,
and are suffixed with .ini.
The stand-alone programs are
designed to operate completely independently.
That is, one does not have to be running for the others to operate. Data are shared between the programs through
disk files, and sometimes 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. The
programs ANALYZE, LOCATE, and SUMMARY each display a window covering one
monitor. Earthworm modules lpproc, develo, hypo_display, mm, mtinver, 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
an 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.