PACIFIC NORTHWEST SEISMOGRAPH NETWORK OPERATIONS
01HQAG0011
S.D. Malone, R.S. Crosson, and A.I. Qamar, P.I.s
Dept. of Earth and Space Sciences, University of Washington
Seattle, WA 98195-1310
Phone:(206)543-1190 FAX:(206)543-0489
e-mail: steve, bob, tony, or ruth@ess.washington.edu
URL: /SEIS/PNSN/
Key words: Seismology, Education-lay, Real-time earthquake information

Oct. 1, 2002 - Sept. 30, 2003

Non-technical Summary

The Pacific Northwest Seismograph Network (PNSN) operates seismograph stations in Washington and Oregon, and collects and analyzes earthquake data. Between Oct. 1, 2002 and Sept. 30, 2003 the PNSN analyzed 4,990 events. Of these, 4,050 were earthquakes or blasts within the network (1,439 of which were too small to locate). Within the network area, 1,836 earthquakes were located west of 120.5 degrees west longitude (including 550 in the general vicinity of Mount St. Helens, which has not had a magmatic eruption since 1986), and 286 east of 120.5 degrees west longitude. The remaining events were blasts within the network (500), regional earthquakes (282), teleseisms (658), low-frequency events (535 events, 12 locatable, probably icequakes, near the summit of Mt. Rainier), and surficial events (558 events, 4 locatable, mostly rockfalls near the summits of Mt. St. Helens and Mt Rainier).

West of the Cascades, 41 earthquakes were reported felt in Washington or Oregon, ranging in magnitude from 2.0 to 4.8. The largest event was a magnitude 4.8 Benioff zone earthquake at a depth of about 50 km, located in Washington on the eastern side of the Olympic Peninsula on April 25 (UTC).

East of the Cascades in Washington, seven earthquakes (magnitudes 0.6 to 3.3) were reported felt (the largest, magnitude 3.3, was actually slightly out of the area, in Idaho). In Oregon, twelve earthquakes (including 3 just over the border in Idaho state) were reported felt. The largest event in Oregon was close to the Portland urban area. It was magnitude 3.9, and occurred at a depth of about 18 km on April 24 (UTC).

This year, low-amplitude seismic signals (deep tremor) were discovered. These signals may be associated with "silent slip" events on the Cascadia Subduction zone. "Silent slip" events were discovered a few years ago through GPS geodetic data. The "deep tremor" can be seen online in webicorder records from nearby stations, but barely rises above the background noise. With special filtering and processing the signals are often very clearly seen and appear to originate at 30-40 km depth -- along the Cascadia subduction zone beneath northwestern Washington and Vancouver Island. Some deep tremor events have been observed at about the same time and place as the "silent slip" events detected with GPS.

Network Operations

The Pacific Northwest Seismograph Network (PNSN) operates 176 short-period, broad-band, or strong-motion seismic stations west of 120 degrees west longitude under this agreement, and 40 additional stations under other support. Some stations include up to 7 components. PNSN stations in southern and central Oregon are maintained by the University of Oregon under Cooperative Agreement 01HQAG0012. The PNSN exchanges real-time data with adjacent networks to improve our ability to locate earthquakes on the edge of our network. The PNSN records and assists with the maintenance of several short-period stations operated by the USGS, and receives real-time data from six US National Network (USNSN) stations in Washington and Oregon.

A PNSN seismologist is always available on-call, and our standard procedure is to respond to pager messages from our automatic earthquake detection process (initiated for any earthquake within our network of magnitude 2.9 or larger), or calls from Washington or Oregon emergency management agencies or the UW police. Information for well-located earthquakes is sent out automatically by the event detection process to select recipients including the national ANSS catalog. Emergency managers and other high-priority information users receive very rapid notification through the RACE pager-PC system, faxes, e-mail, and the national QDDS earthquake message system. Simultaneously, an automatic Web-site is created for the event (see /SEIS/EQ_Special/lasteq.html).

Final details are provided as soon as the duty seismologist analyzes the earthquake information. Final locations and magnitudes for earthquakes of M>=2.9 are also disseminated through the NOAA emergency weather notification system.

For all earthquakes, updates of information are posted to Web-pages each time the analyst finalizes a group of locations and magnitudes. In addition to ordinary phone lines, the PNSN has a radio link to the King County and City of Seattle Emergency Operations Centers and an independent direct phone link to the Washington State Dept. of Emergency Services.

The PNSN provides "Recent Earthquakes" web pages using the national "Quake Data Delivery System", "ShakeMap" pages (showing instrumental intensity, PGA, and PGV), and links to the USGS CIIM (Community Internet Intensity Maps) site, which collects, compiles, and interprets web-based felt reports from the public.

  • The PNSN Strong Motion Program: Since 1996, the PNSN has installed digital strong-motion instruments, mostly in the Puget Sound urban area. There are now 51 ANSS instruments in the Pacific Northwest, and a total of 89 strong-motion real-time stations in our network. Continuous data from these stations are sent to the PNSN via Internet or lease-line modem, but the instruments also have a trigger set to record stronger events on-site. If continuous data transmission fails, the data will still be available via dial-up retrieval or site visit. Three additional dial-up stations are operated by the USGS in the Portland area. This year two new CREST (Consolidated Reporting of EarthquakeS and Tsunamis) stations were installed, one on the flanks of Mt. Hood in Oregon and the other near Ellensburg in the Cascades, bringing the total number of PNSN CREST stations to 15. The PNSN also receives 4 additional northern California CREST stations.

  • Data Availability: Continuous telemetry data streams from most broadband stations and a few selected short-period stations are recorded at the UW, and all broad-band and short-period data are provided to IRIS in near real-time via the IRIS BUD system. Complete unedited trace-data are saved for all network triggers. Edited, quality-controlled event trace-data are archived at the UW on large disks, 2.1 GByte exabyte tape, and on high-speed, high-capacity (20 GByte) digital linear tape (DLT) cartridges. Edited event trace-data are also archived at the IRIS Data Management Center (DMC) in SEED format, where they can be retrieved by any investigator via the standard IRIS data request mechanisms.

  • Education and Outreach: Staff from the PNSN provide an educational outreach program to better inform the public, policy makers, and emergency managers about seismicity and natural hazards. Most of the PNSN strong-motion instruments are located at public schools and monthly e-mail information and news updates are sent to teachers. We also provide information sheets, lab tours, workshops, and media interviews, and have an audio library with several tapes. Current seismic activity and other information are available via Internet on the World-Wide-Web (WWW): /SEIS/PNSN

  • Special Events: PNSN staff participated in meetings with numerous groups, including hosting several meetings of the ANSS PNW Region Advisory Committee (see www.ess.washington.edu/SEIS/ANSS/), and making presentations in other meetings, such as ANSS, IRIS and Earthscope committees, Cascadia Regional Earthquake Workgroup, Washington State Seismic Safety Council, National Tsunami Hazard Mitigation Group, Earthquake Engineering Research Institute, Seismological Society of America, National Park employees, and many other groups.

    Seismicity

    Between Oct. 1, 2002 and Sept. 30, 2003, 24 earthquakes were reported felt in Washington west of the Cascades, ranging in magnitude from 1.6 to 4.1. Forty-four earthquakes (magnitudes -1.6 to 4.0) were reported felt east of the Cascades, and four earthquakes ranging in magnitude from 3.2 to 4.5 were reported felt in Oregon. 

    		TABLE 2-- FELT EARTHQUAKES Oct. 1, 2002 - Sept. 30, 2003

		DATE-TIME is in Universal Time (UTC) which is PST + 8 hours.
		Magnitudes are reported as local magnitude (Ml).
		QUAL is location quality A-good, D-poor
____________________________________________________________________________________________
DATE-(UTC)-TIME      LAT(N)  LON(W)   DEP  MAG  QUAL  COMMENTS
yy/mm/dd hh:mm:ss    deg.      deg.   km    Ml
02/10/04 17:31:32    47.65N 120.25W   3.0   2.5  AB   2.3 km WSW of Entiat, WA
02/10/08 10:40:23    47.58N 121.84W  17.5   2.9  BA   4.2 km ENE of Fall City, WA
02/10/18 10:13:57    47.00N 121.99W  15.7   2.0  BA  21.7 km   S of Enumclaw, WA
02/10/31 10:50:46    48.49N 122.88W   0.1   2.4  CC  10.1 km ESE of Friday Harbor, WA
02/11/04 05:02:03    48.16N 122.56W  26.7   3.1  BA  33.3 km SSW of Mount Vernon, WA
02/11/16 00:46:58    45.07N 116.82W  10.0   3.4  DD  85.8 km ENE of Baker, OR
02/11/16 09:24:58    45.08N 116.80W  10.0   2.4  BD  88.5 km ENE of Baker, OR
02/11/16 09:37:39    45.15N 116.86W  10.0   3.1  CD  87.4 km ENE of Baker, OR
02/11/23 09:41:17    47.69N 117.40W   0.0   0.6  AC   2.3 km   N of Spokane, WA (Mission & N Division)
02/11/29 11:52:35    48.93N 123.04W  13.3   3.8  CD  22.0 km   S of Vancouver,BC
02/12/07 04:26:40    48.10N 123.34W   8.8   2.2  BA   7.8 km   E of Port Angeles, WA
02/12/27 06:38:06    48.08N 123.35W   8.9   2.4  BC   7.5 km ESE of Port Angeles, WA
03/01/09 17:55:11    47.62N 121.97W   8.8   2.1  BA   5.3 km  SW of Carnation, WA
03/01/13 09:58:00    47.77N 120.12W   4.6   2.6  BB  11.1 km  SW of Chelan, WA
03/01/14 00:06:06    48.47N 123.12W  20.9   2.7  BA  10.9 km  SW of Friday Harbor, WA
03/01/14 20:52:50    47.59N 121.90W   2.3   2.5  BB   3.0 km NNW of Fall City, WA
03/01/15 03:41:58    46.61N 120.52W  11.0   3.2  BA   2.7 km NNW of Yakima, WA
03/01/17 01:18:26    48.62N 123.00W  13.5   2.4  BB  10.2 km   N of Friday Harbor, WA
03/01/17 01:42:38    48.60N 123.08W   8.2   2.4  CB  10.2 km  NW of Friday Harbor, WA
03/01/31 22:47:28    47.74N 121.83W   0.0   2.5  CB  11.0 km   E of Duvall, WA
03/02/07 09:16:50    48.49N 123.59W  23.0   2.2  CB  19.9 km WNW of Victoria, BC
03/02/08 18:39:10    47.51N 121.89W   5.8   2.8  CA   5.3 km   S of Fall City, WA
03/02/19 13:54:13    46.54N 121.77W   1.4   2.4  CC  24.9 km   W of Goat Rocks, WA
03/03/09 03:29:52    47.63N 122.15W  22.0   2.4  BA   4.3 km  NE of Bellevue, WA
03/03/18 11:42:28    47.59N 122.60W  27.2   2.5  BA   3.8 km NNE of Bremerton, WA
03/03/20 16:07:47    48.73N 119.51W   0.0   2.7  AD  41.0 km   N of Okanogan, WA
03/03/21 11:23:11    49.22N 123.59W   6.9   2.2  BD  40.2 km WNW of Vancouver,BC
03/03/24 13:16:49    49.23N 123.58W  23.6   2.7  BD  39.9 km WNW of Vancouver,BC
03/03/24 13:43:36    49.25N 123.62W  15.3   2.9  BD  43.5 km WNW of Vancouver,BC
03/03/31 21:20:22    45.63N 122.75W  16.9   2.6  BA  15.5 km  NW of Portland, OR
03/04/15 09:42:43    47.70N 122.60W  23.8   2.1  BB   4.0 km  SE of Poulsbo, WA
03/04/17 01:38:02    47.68N 122.09W  13.7   2.7  CA   8.3 km   E of Kirkland, WA
03/04/24 19:26:30    45.63N 122.73W  17.2   3.9  BA  14.3 km  NW of Portland, OR
03/04/25 10:02:12    47.67N 123.25W  51.3   4.8  BA  37.3 km ESE of Mt Olympus, WA
03/04/25 21:55:31    45.63N 122.74W  16.8   2.2  BA  14.9 km  NW of Portland, OR
03/04/28 22:25:48    45.11N 122.43W  15.1   2.8  CA  26.3 km  SE of Canby, OR
03/05/30 03:50:07    47.48N 122.72W  25.0   3.7  BA  11.4 km  SW of Bremerton, WA
03/06/20 02:01:23    47.65N 121.98W  19.6   3.5  BA   5.4 km   W of Carnation, WA
03/06/20 15:29:56    47.62N 122.16W  32.1   2.5  CA   2.6 km ENE of Bellevue, WA
03/06/26 12:44:57    45.75N 122.32W   7.6   2.2  BC  33.6 km  NE of Portland, OR
03/06/28 06:15:50    47.93N 121.83W  15.7   2.4  BA  12.9 km  NE of Monroe, WA
03/07/06 05:55:11    47.42N 122.77W   8.1   3.0  CB  19.5 km  SW of Bremerton, WA
03/07/08 13:27:37    47.65N 120.27W   0.0   1.9  BB   4.1 km   W of Entiat, WA
03/07/25 20:48:01    45.63N 122.73W  17.4   3.0  BA  14.8 km  NW of Portland, OR
03/07/26 05:26:33    45.63N 122.74W  16.8   2.2  AA  14.8 km  NW of Portland, OR
03/07/26 11:24:44    45.63N 122.73W  16.9   2.8  BA  14.5 km  NW of Portland, OR
03/07/27 10:31:28    45.63N 122.73W  18.3   2.4  BA  14.2 km  NW of Portland, OR
03/07/29 06:21:40    45.99N 122.71W  19.8   2.1  BB  23.5 km  SE of Longview, WA
03/08/22 19:08:37    47.66N 117.43W   0.5   0.9  AC   2.2 km WSW of Spokane, WA (Mission & N Division)
03/09/01 08:55:03    47.94N 121.74W  11.6   2.3  CB  19.6 km ENE of Monroe, WA
03/09/01 18:37:52    47.67N 120.26W   4.9   2.1  AB   3.7 km WNW of Entiat, WA
03/09/21 06:12:41    47.60N 121.83W  17.4   2.0  BA   6.5 km  NE of Fall City, WA
03/09/22 14:06:19    47.93N 116.99W   0.7   3.3  BD  43.0 km  NE of Spokane, WA (Mission & N Division)
____________________________________________________________________________________________
    Publications

    Quarterly bulletins from the PNSN (/SEIS/PNSN/REPTS/quarterly.html) provide operational details and descriptions of seismic activity in Washington and Oregon. These are available from 1984 through the third quarter of 2003. Final published catalogs are available from 1970, when the network began operation, though 1989.

  • Reports and Articles

    Bakun, W.H., R.A. Haugerud, M.G. Hopper, and R.S. Ludwin, 2002, The December 1872 Washington State Earthquake, Bulletin of the Seismological Society of America, Vol. 92, No. 8, pp. 3239-3252

    Brocher, T.M, C.S. Weaver, R.S. Ludwin, 2003 (in press), Assessing hypocentral accuracy and lower magnitude completeness in the Pacific Northwest using seismic refraction detonations and cumulative frequency-magnitude relationships, Seis. Res. Lett., V. 74, No. 6, pp. 772-788.

    Caruso, F., S. Viciguerra, V. Latora, A. Rapisara, S. Malone, (in preparation), Multifractal analysis of Mount St. Helens seismicity as a quantitative characterization of the eruptive activity

    Jones, J., S.D. Malone, (submitted), Mount Hood earthquake activity: volcanic or tectonic origin?, Bull. Seis. Soc. Amer.

    Musumeci, C., S. Gresta, S.D. Malone, 2002, Magma System Recharge of Mount St. Helens from precise relative hypocenter location of microearthquakes, Jour Geophys. Res. DOI:10.1029/2001JB000629.

    Oppenheimer, D., A. Bittenbinder, B. Bogaert, R. Buland, L. Dietz, R. Hanson, S. Malone, C. McCreery, T. Sokolowski, C. Weaver, 2002, The Crest Project: Consolidated reporting of earthquakes and tsunami, ITS 2001 Proceedings, NTHMP Review Session, Paper R5, 2002

    Preston, L.A., K.C. Creager, R.S. Crosson, T.M. Brocher, and A. Trehu, 2003, Intraslab earthquakes: Dehydration of the Cascadia Slab, Science, V. 302, pp. 1197-2000.

    Ranf, R.T., M.O. Eberhard, S. Malone, (in press), Post-Earthquake Prioritization of Bridge Inspections, Earthquake Spectra, EERI

    Tusa, G, S.D. Malone E. Giampiccolo, Stefano Gresta, Carla Musumeci (in press) Microearthquake source parameters and seismic attenuation at Mount St. Helens. Bull. Seis. Soc. Amer.

    Van Wagoner, T., R.S. Crosson, K.C. Creager, G. Medema, L. Preston, N.P. Symons, and T.M. Brocher, 2002, Crustal Structure and relocated earthquakes in the Puget Lowland, Washington, from high-resolution seismic tomography, J. Geophys. Res., 107 (B12), 2381, doi:10.1029/2001JB000710, 2002.

    Vinciguerra, S., D. Elsworth, S. Malone, (in preparation), The 1980 pressure response and dome failure of Mount St. Helens (USA) inferred by seismic scaling exponents.

  • Abstracts

    Barberopoulou, A., A. Qamar, T.L. Pratt, K. Creager, W. Steele, 2003, Local amplification of seismic waves from the Mw7.9 Alaska earthquake and damaging water waves in Lake Union, Seattle, Washington, Geoscience Horizons Seattle 2003, Abstracts with Programs, Geol. Soc. Am. Annual Meeting November 2-5 2003, Paper# 263-9, p. 646.

    Caruso, F.; Vinciguerra, S.; Latora, V.; Rapisarda, A.; Malone, S., 2003, Multifractal analysis of Mt. St. Helens, seismicity as an indicator for eruptive activity, EGS-AGU-EUG Joint Assembly, NP11-1TH4P-1412.

    Crider, J.G. R.S. Crosson, and J. Brooks, The Chelan seismic zone, the great terrace and the December 1872 Washington state earthquake, Geoscience Horizons Seattle 2003, Abstracts with Programs, Geol. Soc. Am. Annual Meeting November 2-5 2003, Paper# 263-3, p. 645.

    Crosson, R.S., 2003, Geophysical constraints on the deep structure of the Washington Cascades, and tectonic implications, Geoscience Horizons Seattle 2003, Abstracts with Programs, Geol. Soc. Am. Annual Meeting November 2-5 2003, Paper# 126-1, p. 305.

    Crosson, R.S. and R.J. Stewart, 2003, Implications of high resolution seismic tomography for the structure and evolution of the Puget basins, Geoscience Horizons Seattle 2003, Abstracts with Programs, Geol. Soc. Am. Annual Meeting November 2-5 2003, Paper# 127-11, p. 309.

    Hill, D.P., S. Prejean, D. Oppenheimer, S.D. Malone, K, Richards-Dinger, 2002, Activity remotely triggered in volcanic and geothermal centers in California and Washington by the 3 November 2002 Mw=7.9 Alaska earthquake Eos Trans. AGU, 83(47),S72F-1357.

    Jones, J.P., S. Malone, 2002, Mount Hood Earthquake Activity: Volcanic or Tectonic Origins?, Eos Trans. AGU, 83(47), S12A-1179.

    Johnson, J.B., R.C. Aster, M.C. Ruiz, S.D. Malone, P.J. McChesney, J.M. Lees, P.R. Kyle, 2003, Interpretation and utility pf infrasonic records from erupting volcanoes, Jour. Volcan. Geother. Res. V. 121 p. 15-63.

    Malone, S. and A. Haulter, 2003, How glacier-quakes can mimic low-frequency volcanic earthquake seismograms, EGS-AGU-EUG Joint Assembly, VGP14-1TU2P-0255.

    Malone, S.D., 2003, A review of regional seismic network recording and data exchange systems, Seis. Res. Lett., V74, 2, p. 228.

    McCausland, W.A., S. Malone, 2003, Deep tremor along the Cascadia subduction zone, Geoscience Horizons Seattle 2003, Abstracts with Programs, Geol. Soc. Am. Annual Meeting November 2-5 2003, Paper# 127-2 2003, p. 308.

    Moran, Seth C., S.D. Malone, J.M. Lees, 2003, Mid-crustal velocity anomalies in the central Washington cascades: evidence for structures affecting regional tectonics and volcanism?, Geoscience Horizons Seattle 2003, Abstracts with Programs, Geol. Soc. Am. Annual Meeting November 2-5 2003, Paper# 262-8, p. 644

    Preston, L., K. Creager, R. Crosson, Intraslab earthquakes in Cascadia caused by dehydration embrittlement, Geoscience Horizons Seattle 2003, Abstracts with Programs, Geol. Soc. Am. Annual Meeting November 2-5 2003, Paper #127-5, p. 308.

    Qamar, A., A. Wright, G. Thomas, 2003, Do Richter magnitudes reveal seismic site response?, Geoscience Horizons Seattle 2003, Abstracts with Programs, Geol. Soc. Am. Annual Meeting November 2-5 2003, Paper #263-9, p. 646

    Simpson, D.W., S. Malone, W. Prescott, 2003, Earthscope facilities for investigations of Cascadia seismicity, Geoscience Horizons Seattle 2003, Abstracts with Programs, Geol. Soc. Am. Annual Meeting November 2-5 2003, Paper# 127-14 2003 (abs) p. 310.