2001 Summary: AG0011/AG1937: Pacific Northwest Seismograph Network Operations

PACIFIC NORTHWEST SEISMOGRAPH NETWORK OPERATIONS
HQ98AG1937 (11/1/99-10/31/00) 01HQAG0011 (11/1/00-10/31/01)
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
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, 2000 - Sept. 30, 2001

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, 2000 and Sept. 30, 2001 the PNSN analyzed 6,263 events. Of these, 5,133 were earthquakes or blasts within the network (2,099 of which were too small to locate). Within the network area, 2,227 tectonic earthquakes were located west of 120.5 degrees west longitude (including 800 in the general vicinity of Mount St. Helens, which has not had a magmatic eruption since 1986), and 275 east of 120.5 degrees west longitude. The remaining events were blasts within the network (587), regional earthquakes (394), teleseisms (736), low-frequency events (70; probably icequakes, mostly near the summit of Mt. Rainier), and surficial events (5; rockfalls near the summits of Mt. St. Helens and Mt Rainier).

Between Oct. 1, 2000 and Sept. 30, 2001, 23 earthquakes were reported felt in Washington west of the Cascades, ranging in magnitude from 1.1 to 6.8. Thirty-seven earthquakes (magnitudes 0.6 to 3.9) were reported felt east of the Cascades, and just one earthquake (magnitude 1.9) was reported felt in Oregon.

The largest event during the reporting period was the damaging magnitude 6.8 Nisqually earthquake of Feb. 28, 2001.

Network Operations

The Pacific Northwest Seismograph Network (PNSN) operates 159 short-period, broad-band, or strong-motion seismic stations west of 120 degrees west longitude under this agreement, and 38 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 four US National Network (USNSN) stations in Washington and Oregon.

Figure 1a. Seismograph stations operated by or recorded at the PNSN at the end of September, 2001. Black crosses indicate the locations of short-period seismometers, Red triangles represent the locations of three-component broad-band seismometer installations, and white squares show the locations of strong-motion stations.

Figure 1b. Detail of Fig. 1a. Puget Sound Seismograph stations operated by or recorded at the PNSN at the end of September, 2001. Symbols as in Fig. 1a.

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. PRELIMINARY information for earthquakes of M>=2.9 is sent out automatically by the event detection process. Emergency managers and other high-priority information users receive very rapid notification through the RACE pager-PC system, faxes and e-mail. 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. In summer 2001, 20 new instruments were installed, bringing the total number of PNSN ANSS strong-motion instruments to 42. 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. Highlights this year include the upgrade of two stations to meet CREST (Consolidated Reporting of EarthquakeS and Tsunamis) standards, and the installation of three other new CREST stations.

Data Availability:All triggered network trace-data is saved in raw unedited format, and continuous telemetry data streams are saved from several selected broadband data and short-period stations. Processed data for each event are backed up on network archive tapes. Edited event trace-data are archived on large disks and kept on 2.1 GByte exabyte tape. We archive the edited trace-data at the University on high-speed, high-capacity (20 GByte) digital linear tape (DLT) cartridges and 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. In addition to information sheets, lab tours, workshops, and media interviews, we have an audio library with several tapes, including a frequently updated message on current seismic activity. Similar, more comprehensive, information is available via Internet on the World-Wide-Web (WWW): /SEIS/

The installation of strong-motion instruments has encouraged the formation of research relationships with organizations who are interested in the data collected and the potential for useful data products. These organizations, in turn, provide the PNSN with station sites and/or telemetry. Cooperative efforts will contribute to more robust and diversified network telemetry, additional non-federally funded strong motion seismograph stations, and increased support for critical staff.

Special Events:

This year was a busy one for us. The M 6.8 Nisqually earthquake on February 28th was followed by intense national media attention, with a high demand for interviews and information. FEMA funding was obtained for: The Nisqually Earthquake Clearinghouse (hosted by the PNSN) to collect and organize data related to the earthquake. The Clearinghouse operated through the end of September.

High demand for public information continued as additional western Washington Benioff zone earthquakes (M 5.0 and M 4.3) occurred in June and July, and a swarm of small earthquakes, in sporadic bursts from June through September, were felt by many in downtown Spokane.

PNSN staff met with numerous state and county officials, representatives of utility and private companies, and engineering and emergency management groups regarding rapid earthquake notification and long-term network and strong-motion development plans. The PNSN installed a RACE System at the WSDOT Seattle Operations Center.

Many presentations were given; to professional groups such as the Washington State Emergency Managers Association (WSEMA), the Western States Seismic Policy Council (WSSPC), the Contingency Planners And Recovery Managers (CPARM), and the Western Washington Emergency Network conference; and to general audiences at functions including Disaster Saturday, the Burke Museum, the Olympic Peninsula Intertribal Cultural Advisory Committee, the Association of Geo-science Educators, the Seattle Middle Schools Science Fair.

The PNSN hosted meetings of the ANSS Technical Integration Committee (see report at http://www.anss.org/ticplan/) and the ANNS Pacific Northwest Region Siting Advisory Committee Meeting (see http://spike.ess.washington.edu/SEIS/ANSS/minutes_april01.html), as well as several meetings of Cascadia Regional Earthquake Workgroup (CREW) subcommittees. PNSN representatives attended a wide variety of other meetings related to earthquake hazards, preparedness, and related information and outreach.

The PNSN was especially well represented at the April meeting of the Seismological Society of America, with individual or shared authorship of numerous posters and presentations.

Tony Qamar, Washington State Seismologist, has been appointed to the newly reconstituted Seismic Safety Committee of the Washington State Emergency Management Council. Dr. Qamar has been appointed chairman of the Information and Technology Subcommittee.

Seismicity

Figure 2. Earthquakes magnitude 2.0 or larger between Oct. 1, 2000 and Sept. 30, 2001. Locations of a few cities are shown as white-filled diamonds. Earthquakes are indicated by red circles or green squares; red circles represent earthquakes at depths shallower than 30 km, and green squares represent earthquakes at 30 km or deeper.

By far the most interesting event during the reporting period was the magnitude 6.8 Nisqually earthquake of Feb. 28, 2001. Extensive information is available on the

The Nisqually Earthquake Clearinghouse: http://maximus.ce.washington.edu/~nisqually/index.html A great deal has been and will be written regarding this earthquake, which caused at least a billion dollars in damages. Only four small aftershocks were recorded in the two weeks following the mainshock, but a possible late aftershock of magnitude 4.3 occurred nearby about six months later.

The Nisqually earthquake was the largest of a unusual series of Benioff zone earthqukes that began in July 1999 with a M 5.8 earthquake about 41 km depth beneath Satsop WA. The Nisqually earthquake, in Feb. 2001, was east of the Satsop earthquake and, at 52 km, deeper. A M 5.0 earthquake on June 10, 2001 was near the location and depth of the 1999 Satsop earthquake, and a M 4.3 earthquake on July 22 (UTC) was close to the location and depth of the Nisqually event.

Other interesting seismicity included a swarm of 61 earthquakes located in the immediate area of downtown Spokane. In addition to the locatable earthquakes, there were many additional events too small to locate due to sparse network coverage of the area. The swarm began in May, and the largest earthquake during the reporting period was a M 3.9 on June 25. No comparable sequence is known in the history of Spokane. For additional details see web page:

The 2001 Spokane Earthquake Sequence: /SEIS/EQ_Special/WEBDIR_01062514151n/overview.html

____________________________________________________________________________________________
		TABLE 1--BENIOFF ZONE EARTHQUAKES - Sizable earthquakes near Satsop, WA
		plus Nisqually Earthquake and aftershocks.

		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
99/07/03 01:43:54	47.07N	123.46W  40.7	5.8	BA              8.0 km   N of Satsop, WA
01/02/28 18:54:32	47.14N	122.72W  51.9	6.8	BA  MAINSHOCK  17.0 km  NE of Olympia, WA
01/02/28 19:02:03	47.18N	122.72W  52.3	1.0	BA  Aftershock 19.7 km  NE of Olympia, WA
01/03/01 09:10:20	47.19N	122.71W  54.3	3.4	BA  Aftershock 21.6 km  NE of Olympia, WA
01/03/01 14:23:34	47.18N	122.72W  51.4	2.7	BA  Aftershock 19.4 km  NE of Olympia, WA
01/03/11 11:57:36	47.20N	122.62W  47.8	1.2	AB             14.9 km WSW of Tacoma, WA
01/06/10 13:19:11	47.16N	123.50W  40.7	5.0	BA             18.3 km   N of Satsop, WA
01/07/22 15:13:52	47.08N	122.68W  52.4	4.3	BA  Aftershock?16.3 km ENE of Olympia, WA

____________________________________________________________________________________________

____________________________________________________________________________________________
		TABLE 2-- FELT EARTHQUAKES 10/1/00-9/30/01

		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
00/10/15 14:30:05    47.84N 123.03W  50.0   3.6  BA  31.4 km WNW of Poulsbo, WA
00/11/01 08:37:17    48.27N 122.54W  21.8   3.3  BA  21.7 km  SW of Mount Vernon, WA
00/11/05 13:10:01    49.47N 119.63W   0.0   3.0  BD   4.7 km  SW of Penticton, BC
00/11/10 09:12:39    48.46N 123.23W  25.2   1.5  BB   9.5 km ENE of Victoria, BC
00/11/25 10:01:39    48.83N 119.34W   2.0   3.1  BD  55.2 km NNE of Okanogan, WA
00/12/24 17:04:58    47.74N 120.26W   8.6   3.5  DB   9.8 km NNW of Entiat, WA
00/12/31 18:07:44    47.50N 121.66W  12.6   2.9  BA   8.8 km   E of North Bend, WA
01/02/14 03:54:54    48.75N 123.12W  20.9   2.3  BD  26.0 km NNW of Friday Harbor, WA
01/02/14 22:03:58    47.51N 121.89W   6.6   3.1  BA   5.4 km   S of Fall City, WA
01/02/24 07:40:50    47.53N 122.06W  22.6   2.2  BA  13.2 km  SE of Bellevue, WA
01/02/28 07:16:13    47.75N 120.03W   0.6   3.2  BB  10.2 km   S of Chelan, WA
01/02/28 18:54:32    47.14N 122.72W  51.9   6.8  BA  17.0 km  NE of Olympia, WA
01/03/01 09:10:20    47.19N 122.71W  54.3   3.4  BA  21.6 km  NE of Olympia, WA
01/03/01 14:23:34    47.18N 122.72W  51.4   2.7  BA  19.4 km  NE of Olympia, WA
01/03/10 06:26:05    47.48N 122.79W  19.3   1.7  AA  15.9 km  SW of Bremerton, WA
01/03/11 17:08:54    47.60N 121.91W  21.6   2.9  BA   4.4 km NNW of Fall City, WA
01/03/16 02:41:11    47.56N 122.07W  18.1   2.2  AA  10.2 km ESE of Bellevue, WA
01/03/21 10:31:05    46.21N 121.02W   0.9   2.9  CC  35.4 km   E of Mt Adams, WA
01/04/07 16:02:35    48.72N 124.76W  41.8   3.9  CD  90.6 km NNW of Forks, WA
01/06/10 13:19:11    47.16N 123.50W  40.7   5.0  BA  18.3 km   N of Satsop, WA
01/06/25 14:15:22    47.68N 117.39W  10.5   3.9  BD   1.3 km NNE of Spokane, WA
01/06/25 15:01:27    47.70N 117.41W  11.1   3.4  DD   3.4 km   N of Spokane, WA
01/06/25 16:49:16    47.73N 117.47W   0.0   2.3  BD   9.0 km NNW of Spokane, WA
01/06/25 22:58:13    47.72N 117.46W   0.0   2.3  DD   7.0 km  NW of Spokane, WA
01/06/26 01:21:21    47.75N 117.48W   0.0   2.1  BD  11.4 km NNW of Spokane, WA
01/06/26 05:52:26    47.75N 117.48W   8.0   2.4  DD  10.9 km  NW of Spokane, WA
01/06/27 09:07:45    47.72N 117.45W   0.4   2.4  DD   6.8 km  NW of Spokane, WA
01/06/27 14:45:37    47.70N 117.41W   7.3   2.9  DD   4.2 km   N of Spokane, WA
01/06/28 07:51:42    47.69N 117.43W   0.5   2.1  DC   3.6 km  NW of Spokane, WA
01/06/28 11:47:48    47.66N 117.41W   0.2   0.7  BD   1.0 km WSW of Spokane, WA
01/06/29 01:13:27    47.67N 117.41W   0.3   2.3  DD   1.0 km NNW of Spokane, WA
01/06/30 01:23:31    46.85N 121.97W   7.7   3.3  BB  16.2 km   W of Mt Rainier, WA
01/07/01 05:44:12    47.67N 117.41W   0.0   2.8  CD   0.4 km   W of Spokane, WA
01/07/01 05:45:43    47.66N 117.40W   0.5   2.8  CD   0.3 km SSE of Spokane, WA
01/07/01 06:07:13    47.67N 117.40W   0.0   2.3  CD   0.5 km  NW of Spokane, WA
01/07/02 17:48:28    47.67N 117.42W   0.5   0.6  BB   1.5 km WNW of Spokane, WA
01/07/03 21:20:27    47.67N 117.41W   0.0   2.2  BA   0.9 km  NW of Spokane, WA
01/07/08 11:16:32    47.68N 117.41W   0.5   1.5  CB   1.7 km  NW of Spokane, WA
01/07/16 11:37:35    45.11N 122.51W  13.1   1.9  CB  21.4 km  SE of Canby, OR
01/07/22 15:13:52    47.08N 122.68W  52.4   4.3  BA  16.3 km ENE of Olympia, WA
01/07/24 13:31:06    47.49N 122.02W  16.4   2.2  BA   9.3 km   N of Maple Valley, WA
01/07/29 06:26:53    47.74N 117.46W   0.6   2.1  BC   8.9 km NNW of Spokane, WA
01/07/29 06:37:58    47.72N 117.45W   6.2   1.3  AD   7.5 km NNW of Spokane, WA
01/07/29 07:04:25    47.73N 117.46W   3.9   1.2  AD   7.9 km NNW of Spokane, WA
01/07/30 20:35:09    47.73N 117.46W   0.6   1.8  BD   8.2 km NNW of Spokane, WA
01/07/31 01:38:11    47.73N 117.45W   0.4   3.2  DC   8.0 km NNW of Spokane, WA
01/07/31 05:07:32    47.73N 117.44W   0.6   2.2  AC   7.4 km NNW of Spokane, WA
01/07/31 05:24:33    47.74N 117.45W   0.5   1.5  CD   9.2 km NNW of Spokane, WA
01/07/31 06:48:11    47.71N 117.47W   0.5   1.8  DD   7.3 km  NW of Spokane, WA
01/07/31 08:51:55    47.72N 117.45W   2.1   1.6  CD   7.4 km NNW of Spokane, WA
01/07/31 16:27:43    47.72N 117.45W   0.6   1.8  BC   7.4 km NNW of Spokane, WA
01/08/01 14:29:48    47.71N 117.44W   0.6   2.2  AD   5.9 km NNW of Spokane, WA
01/08/09 13:31:24    47.73N 117.46W   0.5   1.5  BB   8.2 km  NW of Spokane, WA
01/08/14 13:28:27    44.28N 125.46W  10.0   1.5  BD 119.1 km WSW of Newport, OR
01/08/19 06:17:32    48.25N 121.61W   1.7   3.0  CC   1.0 km WSW of Darrington, WA
01/08/25 17:52:34    48.23N 121.60W   2.7   2.1  CC   2.1 km   S of Darrington, WA
01/08/30 03:47:31    48.23N 121.62W   4.8   2.7  CC   2.9 km  SW of Darrington, WA
01/09/28 18:34:53    47.68N 117.38W   1.8   2.8  BC   1.8 km  NE of Spokane, WA
01/09/28 18:37:53    47.66N 117.37W   0.3   1.9  CD   2.3 km ESE of Spokane, WA
01/09/28 18:38:37    47.67N 117.40W   0.6   2.6  CC   0.7 km NNW of Spokane, WA
01/09/28 18:41:40    47.67N 117.39W   0.0   1.6  BC   0.6 km  NE of Spokane, WA
____________________________________________________________________________________________

Publications

Quarterly bulletins from the PNSN provide operational details and descriptions of seismic activity in Washington and Oregon. These are available from 1984 through the third quarter of 2000. PNSN Quarterly Reports from 1994-1998 included moment-tensor focal mechanisms for earthquakes larger than magnitude 3.5 provided by Dr. John Nabelek of Oregon State University (OSU) under support from USGS NEHRP Grant 1434-93-G-2326. Final published catalogs are available from 1970, when the network began operation, though 1989. A 1990-1994 printed catalog is in preparation.

Reports and Articles

Kirkham, H., S. Malone, and J. Delaney, 2000, The NEPTUNE observatory as seismic early warning system. Joint US-Japan conference on earthquake disaster mitigation, Japan, July 10, 2000

Musumeci, C., S.D. Malone, E. Giampiccolo, and S. Gresta, 2000, Hypocentral distribution, focal mechanisms and the stress field at Mount St. Helens (1995-1998), Annali de Geofisica V. 43, N. 5, p. 889-904.

Musumeci, C, S.D. Malone, and S. Gresta, in press, Magma System Recharge of Mount St. Helens from precise relative hypocenter location of microearthquakes. Jour. Geophys. Res (in press).

Nisqually Earthquake Clearinghouse Group, 2001, Nisqually Earthquake Preliminary Reconnaissance Report, http://www.eeri.org/earthquakes/Reconn/Nisqually_Wa_2001/NisquallyEQrep.PDF, EERI Reconnaissance Report (32 pp.)

PNSN Staff, 2001, Preliminary Report on the Mw=6.8 Nisqually, Washington earthquake of 28 February 2001, 2001, Seis. Res. Lett., V. 72, N. 3, pp. 352-361.

Van Wagoner, T., R.S. Crosson, N.P. Symons, G.F. Medema, K.C. Creager, and L.A. Preston 2001 (in review), High resolution seismic tomography and earthquake relocation n the Puget Lowland, Washington, JGR.

Abstracts

Bakun, W.H. and R.S. Ludwin, 2001 (abstract), Significant Historical Puget Sound Earthquakes, Seismological Society of America 2001 Annual Meeting, Special Session on the Nisqually Earthquake, V. 72, No. 3, p. 392

Bakun, W.H., R.A. Haugerud, M.G. Hopper, and R.S. Ludwin, 2001 (abstract), The December 1872 Washington State Earthquake, Seismological Society of America 2001 Annual Meeting, Seis. Res. Lett. V. 72, No. 2, p. 269

Ludwin, R.S., 2001 (abstract), Searching for Native Stories about Cascadia Subduction Zone Earthquakes, Seismological Society of America 2001 Annual Meeting, Seis. Res. Lett. V. 72, No. 2, p. 270

Crosson, R.S., K.C. Creager, S. Malone, G. Thomas, R. Ludwin, A. Qamar, 2001 (abstract), The Magnitude 6.8 Nisqually Earthquake of February 28, 2001: Seismological Aspects, Seismological Society of America 2001 Annual Meeting, Special Session on the Nisqually Earthquake, V. 72, No. 3, p. 394

Frankel, A., D. Carver , S. Malone, G. Thomas, C. Weaver, C. Stephens, R. Porcella, H. Benz, J. Filson, I. Wong, T. Bice, R. Norris, M. Petersen, and S. Harmsen, 2001 (abstract), Overview of strong-motion recordings of the M6.8 Nisqually, Washington, earthquake, Seismological Society of America 2001 Annual Meeting, Special Session on the Nisqually Earthquake, V. 72, No. 3, p. 390

Haugerud, R.A., G. Thomas, and S.P. Palmer, 2001 (abstract), Regional map view of instrumentally-determined ground motions, Nisqually Earthquake of 28 February 2001, Seismological Society of America 2001 Annual Meeting, Special Session on the Nisqually Earthquake

Crosson, R.S., and N.P. Symons, 2001 (abstract), What goes down, comes up: flexural origin of the Puget Basins and tectonic implications, V. 72, No. 2, p. 237

McCrory, P.A., S.R. Walter, and R.S. Crosson, 2001 (abstract), Possible discontinuity in Juan de Fuca plate in the vicinity of the 2001 (M6.8) Nisqually earthquake, Seismological Society of America 2001 Annual Meeting, Special Session on the Nisqually Earthquake, V. 72, No. 3, p. 391

Preston, L.A., K.C. Creager, R.S. Crosson, T.M. Van Wagoner, A.M. Trehu, T.M. Brocher, M.A. FISHER, and SHIPS Working Group , 2001 (abstract), Cascadia slab structure and deep earthquakes, V. 72, No. 2, p. 237

Troost, K.G., R.A. Haugerud, T.J. Walsh, E.L. Harp, D.B. Booth, W.P. Steele, K.W. Wegmann, T.L. Pratt, B.S. Sherrod, and S. L. Kramer, 2001 (abstract), Ground failures produced by the Nisqually earthquake, V. 72, No. 3, p. 396

Xu, Q., K.C. Creager, Q. Li, and R.S. CROSSON, 2001 (abstract), Seismological Society of America 2001 Annual Meeting, Special Session on the Nisqually Earthquake, V. 72, No. 3, p. 394

Theses and Dissertations

Jeffrey B. Johnson, Interpretation of infrasound generated by erupting volcanoes and seismo-acoustic energy partitioning during strombolian explosions. PhD Dissertation, University of Washington, 2000

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