Since 1984, we have issued quarterly bulletins for all of Washington and Oregon. These include catalogs of earthquakes and blasts located in Washington and Oregon, providing up-to-date coverage of seismic and volcanic activity. Appendix 1 contains quarterly bulletins covering 1997.
The PNSN is currently in the process of upgrading operations, including extensive changes to data recording, exchange, and processing systems. Upgrades include enhancement of the emergency information distribution system, installation of seismic sensors that can accurately capture the full range of earthquake amplitudes and frequencies, implementation of a data recording system that fully supports multi-component and multi-timestamped data, and near-real-time data exchange with neighboring networks.
The USGS/NOAA CREST (Consolidated Reporting of EarthquakeS and Tsunamis) project is designed to improve NOAA's ability to assess the likelihood of a tsunami and issue timely warnings in the event of a US subduction earthquake. CREST calls for upgrades to regional networks to enable them to provide very rapid and reliable information to the Alaska and Pacific Tsunami Warning Centers. While recent PNSN station upgrades have been in urban areas, our updating effort is fully compatible with the USGS/NOAA CREST project. The EARTHWORM data reporting system, already in use at the PNSN, has been selected for use by CREST.
In May of 1996 the US Geological Survey (USGS) funded the Pacific Northwest Seismograph Network (PNSN) to begin a pilot project of modern strong-motion instrumentation in the Puget Sound urban area. Three sites were funded under this agreement, and funds for three additional stations were provided by the USGS under special contract 1434-HQ-96-GR-02714. All six funded stations are installed and operating as part of the network. Table 1C gives locations, instrumentation, and telemetry methods used for each of the current strong-motion stations. Several of the strong-motion sites also have broad-band three-component sensors.
RACE is an earthquake notification system for emergency managers and others who need very rapid pager-based notification of earthquake activity. The RACE system is based on the CUBE system developed at Cal Tech for the Southern California Seismic Network. The RACE system is operating in test mode at the Oregon Dept. of Mineral Industries, and the Oregon Office of Emergency Management. An article on the development and future potential of rapid notification systems appeared in the December, 1997 issue of Washington Geology Vol. 25, No. 4, pp. 33-36. The article is entitled "Rapid Earthquake Notification in the Pacific Northwest" by A. Qamar, S.D. Malone, and R.S. Ludwin
The PNSN is upgrading its SUNWORM data aquisition system to be fully EARTHWORM compatible. The EARTHWORM system was initially developed by the USGS to replace outdated Real-Time Picker (RTP) hardware. It was also designed to help regional networks with both real-time earthquake notification issues and data recording and processing. Additional issues being addressed by the EARTHWORM team now include replacement of obsolete hardware and software, integration of regional and national networks, and re-engineering of seismographic networks to accommodate advances in Internet communications, telemetry, and sensor design. Design objectives of the EARTHWORM system include modularity, vendor independence, connectivity, scalability, and robustness. More information on the EARTHWORM system is available on the CNSS (Council for the National Seismic System) web pages: "http://www.cnss.org/"
The PNSN has been running a test installation of the basic EARTHWORM automatic earthquake location software since June, 1997. PNSN programmer Pete Lombard assisted with EARTHWORM development. Specific recent accomplishments include:
One of the PIs (SDM) of this contract was elected Chairman of the Council of the National Seismic System (CNSS) this past winter. His duties as chairman are considered related to this cooperative agreement and thus are partially supported by this agreement. During this year the CNSS Chairman arranged for a set of master CNSS WEB pages, national meeting summary, the initiation of an EarthWorm Advisory Board and a design for the exchange of rapid earthquake notification messages between networks, as well as other routine CNSS business.
At the end of 1997, the PNSN was digitally recording 142 channels of seismic data in a triggered mode, and receiving additional data from 13 broad-band and 6 strong-motion stations in the Pacific Northwest. The operation of 92 sites (some with multiple components) were supported under this contract, JOA 1434-95-A-1302. The majority of stations consist of a single, short-period vertical, component which is telemetered continuously in analog form to the UW. In addition, JOA 1434-95-A-1302 supports operation of the 6 strong motion stations and 7 of the broad-band stations, and horizontal seismometers with Wood-Anderson-response at station SEA on the campus of the University of Washington. The supported stations cover much of western Washington and Oregon, including the volcanos of the central Cascades.
Additional stations funded by other contracts are also used in event locations. The locations of all stations operating at the end of 1997 are given in Tables 1A (short-period), 1B (broad-band), and 1C (strong motion) and shown in Fig. 1. Quarterly reports provide additional details of station operation. Quarterly reports from January 1, 1997 through December, 1997 are included as Appendix 1.
Aside from station outages, normal maintenance includes a visit to each site at least once every two years to replace batteries and do preventive maintenance. In addition seismometers must be replaced every 4-6 years. More than 30 radio telemetry relay sites are also maintained independently of the seismograph stations.
Table 1A lists short-period stations with continuous telemetry to the PNSN lab which were operated by the PNSN at the end of the reporting period. Table 1B lists broad-band stations in the Pacific Northwest, and Table 1C lists strong-motion, three component stations. The first column in Tables 1A and 1B gives the 3-letter station designator. Column 2 designates the funding agency; operations of stations marked by a % symbol were fully supported by USGS joint operating agreement 1434-95-A-1302. Stations designated # were installed or are maintained by the USGS, but are telemetered to the PNSN lab. Data from some of the broad-band stations operated under other support are archived at the PNSN. Remaining columns give station north latitude and west longitude (in degrees, minutes and seconds), station elevation in km, and comments indicating landmarks for which stations were named.
=
TABLE 1A
Short-period Stations operating during the fourth quarter 1997
=
l1p-2 c1p-2w(2) cp-2 cp-2 cp-2 lp-2. STA F LAT LONG EL NAME
_
ASR % 46 09 09.9 121 36 01.6 1.357 Mt. Adams - Stagman Ridge AUG % 45 44 10.0 121 40 50.0 0.865 Augspurger Mtn BBO % 42 53 12.6 122 40 46.6 1.671 Butler Butte, Oregon BHW % 47 50 12.6 122 01 55.8 0.198 Bald Hill BLN % 48 00 26.5 122 58 18.6 0.585 Blyn Mt. BOW % 46 28 30.0 123 13 41.0 0.870 Boistfort Mt. BPO % 44 39 06.9 121 41 19.2 1.957 Bald Peter, Oregon BRV + 46 29 07.2 119 59 28.2 0.920 Black Rock Valley BVW + 46 48 39.6 119 52 59.4 0.670 Beverly CBS + 47 48 17.4 120 02 30.0 1.067 Chelan Butte, South CDF % 46 06 58.2 122 02 51.0 0.780 Cedar Flats CMM % 46 26 07.0 122 30 21.0 0.620 Crazy Man Mt. CMW % 48 25 25.3 122 07 08.4 1.190 Cultus Mtns. CPW % 46 58 25.8 123 08 10.8 0.792 Capitol Peak CRF + 46 49 30.0 119 23 13.2 0.189 Corfu DBO 43 07 09.0 123 14 34.0 0.984 Dodson Butte, Oregon DPW + 47 52 14.3 118 12 10.2 0.892 Davenport DY2 + 47 59 06.6 119 46 16.8 0.890 Dyer Hill 2 EDM # 46 11 50.4 122 09 00.0 1.609 East Dome, Mt. St. Helens ELK % 46 18 20.0 122 20 27.0 1.270 Elk Rock ELL + 46 54 34.8 120 33 58.8 0.789 Ellensburg EPH + 47 21 22.8 119 35 45.6 0.661 Ephrata ET3 + 46 34 38.4 118 56 15.0 0.286 Eltopia (replaces ET2) ETW + 47 36 15.6 120 19 56.4 1.477 Entiat FBO % 44 18 35.6 122 34 40.2 1.080 Farmers Butte, Oregon FL2 % 46 11 47.0 122 21 01.0 1.378 Flat Top 2 FMW % 46 56 29.6 121 40 11.3 1.859 Mt. Fremont GBL + 46 35 54.0 119 27 35.4 0.330 Gable Mountain GHW % 47 02 30.0 122 16 21.0 0.268 Garrison Hill GL2 + 45 57 35.0 120 49 22.5 1.000 New Goldendale GLK % 46 33 50.2 121 36 30.7 1.320 Glacier Lake GMO % 44 26 20.8 120 57 22.3 1.689 Grizzly Mountain, Oregon GMW % 47 32 52.5 122 47 10.8 0.506 Gold Mt. GSM % 47 12 11.4 121 47 40.2 1.305 Grass Mt. GUL % 45 55 27.0 121 35 44.0 1.189 Guler Mt. HAM # 42 04 08.3 121 58 16.0 1.999 Hamaker Mt., Oregon HBO % 43 50 39.5 122 19 11.9 1.615 Huckleberry Mt., Oregon HDW % 47 38 54.6 123 03 15.2 1.006 Hoodsport HOG # 42 14 32.7 121 42 20.5 1.887 Hogback Mtn., Oregon HSO % 43 31 33.0 123 05 24.0 1.020 Harness Mountain, Oregon HSR % 46 10 28.0 122 10 46.0 1.720 South Ridge, Mt. St. Helens HTW % 47 48 14.2 121 46 03.5 0.833 Haystack Lookout JBO + 45 27 41.7 119 50 13.3 0.645 Jordan Butte, Oregon JCW % 48 11 42.7 121 55 31.1 0.792 Jim Creek JUN % 46 08 48.0 122 09 10.8 1.049 June Lake KMO % 45 38 07.8 123 29 22.2 0.975 Kings Mt., Oregon KOS % 46 27 40.8 122 11 25.8 0.828 Kosmos LAB # 42 16 03.3 122 03 48.7 1.774 Little Aspen Butte, Oregon (4-comp) LCW % 46 40 14.4 122 42 02.8 0.396 Lucas Creek LMW % 46 40 04.8 122 17 28.8 1.195 Ladd Mt. LNO + 45 52 18.6 118 17 06.6 0.771 Lincton Mt., Oregon LO2 % 46 45 00.0 121 48 36.0 0.853 Longmire LOC + 46 43 01.2 119 25 51.0 0.210 Locke Island LVP % 46 04 06.0 122 24 30.0 1.170 Lakeview Peak MBW % 48 47 02.4 121 53 58.8 1.676 Mt. Baker MCW % 48 40 46.8 122 49 56.4 0.693 Mt. Constitution MDW + 46 36 47.4 119 45 39.6 0.330 Midway MEW % 47 12 07.0 122 38 45.0 0.097 McNeil Island MJ2 + 46 33 27.0 119 21 32.4 0.146 May Junction 2 MOX + 46 34 38.4 120 17 53.4 0.501 Moxie City
l1p-2 c1p-2w(2) cp-2 cp-2 cp-2 lp-2.
TABLE 1A continued
_
STA F LAT LONG EL NAME
_
MPO % 44 30 17.4 123 33 00.6 1.249 Mary's Peak, Oregon MTM % 46 01 31.8 122 12 42.0 1.121 Mt. Mitchell NAC + 46 43 59.4 120 49 25.2 0.728 Naches NCO % 43 42 14.4 121 08 18.0 1.908 Newberry Crater, Oregon NEL + 48 04 12.6 120 20 24.6 1.500 Nelson Butte NLO % 46 05 21.9 123 27 01.8 0.826 Nicolai Mt., Oregon OBC % 48 02 07.1 124 04 39.0 0.938 Olympics - Bonidu Creek OBH % 47 19 34.5 123 51 57.0 0.383 Olympics - Burnt Hill OCP % 48 17 53.5 124 37 30.0 0.487 Olympics - Cheeka Peak OD2 + 47 23 15.6 118 42 34.8 0.553 Odessa site 2 OFK % 47 57 00.0 124 21 28.1 0.134 Olympics - Forks OHW % 48 19 24.0 122 31 54.6 0.054 Oak Harbor ONR % 46 52 37.5 123 46 16.5 0.257 Olympics - North River OOW % 47 44 03.6 124 11 10.2 0.561 Octopus West OSD % 47 48 59.2 123 42 13.7 2.008 Olympics - Snow Dome OSR % 47 30 20.3 123 57 42.0 0.815 Olympics Salmon Ridge OT3 + 46 40 08.4 119 13 58.8 0.322 New Othello OTR % 48 05 00.0 124 20 39.0 0.712 Olympics - Tyee Ridge PAT + 45 52 55.2 119 45 08.4 0.262 Paterson PGO % 45 27 42.6 122 27 11.5 0.253 Gresham, Oregon PGW % 47 49 18.8 122 35 57.7 0.122 Port Gamble PRO + 46 12 45.6 119 41 08.4 0.553 Prosser RC1 + 46 56 42.6 119 26 39.6 0.485 Royal City (3 comp.) RCM % 46 50 08.9 121 43 54.4 3.085 Mt. Rainier, Camp Muir RCS % 46 52 15.6 121 43 52.0 2.877 Mt. Rainier, Camp Schurman RER % 46 49 09.2 121 50 27.3 1.756 Mt. Rainier, Emerald Ridge RMW % 47 27 35.0 121 48 19.2 1.024 Rattlesnake Mt. (West) RNO % 43 54 58.9 123 43 25.5 0.850 Roman Nose, Oregon RPW % 48 26 54.0 121 30 49.0 0.850 Rockport RSW + 46 23 40.2 119 35 28.8 1.045 Rattlesnake Mt. (East) RVC % 46 56 34.5 121 58 17.3 1.000 Mt. Rainier - Voight Creek RVN 47 01 38.6 121 20 11.9 1.885 Raven Roost RVW % 46 08 53.2 122 44 32.1 0.460 Rose Valley SAW + 47 42 06.0 119 24 01.8 0.701 St. Andrews SEA 47 39 18.0 122 18 30.0 0.030 Seattle (Wood Anderson) SEP # 46 12 00.7 122 11 28.1 2.116 September lobe (Replaces REM) SHW % 46 11 37.1 122 14 06.5 1.425 Mt. St. Helens SMW % 47 19 10.7 123 20 35.4 0.877 South Mtn. SOS % 46 14 38.5 122 08 12.0 1.270 Source of Smith Creek SSO % 44 51 21.6 122 27 37.8 1.242 Sweet Springs, Oregon STD % 46 14 16.0 122 13 21.9 1.268 Studebaker Ridge STW % 48 09 02.9 123 40 13.1 0.308 Striped Peak TBM + 47 10 12.0 120 35 52.8 1.006 Table Mt. TCO % 44 06 21.0 121 36 01.0 1.975 Three Creek Meadows, Oregon. TDH % 45 17 23.4 121 47 25.2 1.541 Tom,Dick,Harry Mt., Oregon TDL % 46 21 03.0 122 12 57.0 1.400 Tradedollar Lake TKO % 45 22 16.7 123 27 14.0 1.024 Trask Mtn, Oregon TRW + 46 17 32.0 120 32 31.0 0.723 Toppenish Ridge TWW + 47 08 17.4 120 52 06.0 1.027 Teanaway VBE % 45 03 37.2 121 35 12.6 1.544 Beaver Butte, Oregon VCR % 44 58 58.2 120 59 17.4 1.015 Criterion Ridge, Oregon VFP % 45 19 05.0 121 27 54.3 1.716 Flag Point, Oregon VG2 % 45 09 20.0 122 16 15.0 0.823 Goat Mt., Oregon VGB + 45 30 56.4 120 46 39.0 0.729 Gordon Butte, Oregon VIP % 44 30 29.4 120 37 07.8 1.731 Ingram Pt., Oregon VLL % 45 27 48.0 121 40 45.0 1.195 Laurance Lk., Oregon VLM % 45 32 18.6 122 02 21.0 1.150 Little Larch, Oregon VRC # 42 19 47.2 122 13 34.9 1.682 Rainbow Creek, Oregon VSP # 42 20 30.0 121 57 00.0 1.539 Spence Mtn, Oregon VT2 + 46 58 02.4 119 59 57.0 1.270 Vantage2 VTH % 45 10 52.2 120 33 40.8 0.773 The Trough, Oregon WA2 + 46 45 19.2 119 33 56.4 0.244 Wahluke Slope WAT + 47 41 55.2 119 57 14.4 0.821 Waterville WG4 + 46 01 49.2 118 51 21.0 0.511 Wallula Gap WIB # 46 20 34.8 123 52 30.6 0.503 Willapa Bay (3 comp.) WIW + 46 25 45.6 119 17 15.6 0.128 Wooded Island WPO % 45 34 24.0 122 47 22.4 0.334 West Portland, Oregon WPW % 46 41 53.4 121 32 48.0 1.250 White Pass WRD + 46 58 12.0 119 08 41.4 0.375 Warden XTL 46 55 47.8 121 29 35.8 1.665 Crystal Mtn. YA2 + 46 31 36.0 120 31 48.0 0.652 Yakima YEL # 46 12 35.0 122 11 16.0 1.750 Yellow Rock, Mt. St. Helens
Table 1B lists broad-band, three-component stations operating in Washington and Oregon that provide data to the PNSN. Stations are operated by the University of Washington (UW), Oregon State University (OSU), the University of Oregon (UO), or the US Geological Survey US National Seismograph Network (USGS-USNSN).
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TABLE 1B
Broad-band three-component stations operating at the end of the fourth quarter 1997. Symbols are as in Table 1A.
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l1p-2 c1p-2w(2) cp-2 cp-2 cp-2 lp-2. STA F LAT LONG EL NAME
_
CHE 45 21 16.0 122 59 19.0 0.436 Chehalem, Oregon (UO) COR 44 35 08.5 123 18 11.5 0.121 Corvallis, Oregon (IRIS station, OSU) ERW % 48 27 14.4 122 37 30.2 0.389 Mt. Erie, WA (UW) GNW % 47 33 51.8 122 49 31.0 0.165 Green Mountain, WA (UW) LON % 46 45 00.0 121 48 36.0 0.853 Longmire, WA (UW) LTY % 47 15 21.2 120 39 53.3 0.970 Liberty, WA (UW) NEW 48 15 50.0 117 07 13.0 0.760 Newport Observatory (USGS-USNSN) PIN 43 48 40.0 120 52 19.0 1.865 Pine Mt. Oregon (UO) RAI 46 02 25.1 122 53 06.4 1.520 Trojan Plant, Oregon (OSU) RWW % 46 57 50.1 123 32 35.9 0.015 Ranney Well (UW) SPW % 47 33 13.3 122 14 45.1 0.008 Seward Park, Seattle (UW) TTW % 47 41 40.7 121 41 20.0 0.542 Tolt Res, WA (UW) WVOR 42 26 02.0 118 38 13.0 1.344 Wildhorse Valley, Oregon (USGS-USNSN) =
Table 1C lists strong-motion, three-component stations
operating in Washington and Oregon that provide data in real or near-real
time to the PNSN.
Several of these stations also have broad-band instruments, as noted.
The "SENSOR" field designates what type of seismic sensor is used;
A = Terra-Tech SSA-320 SLN triaxial accelerometer,
BB = Guralp CMG-40T 3-D broadband velocity sensor. The "TELEMETRY" field indicates
the type of telemetry used to recover the data. C = continuously telemetered via dedicated telephone lines, D = dial-up.
=
TABLE 1C
Strong-motion three-component stations operating at the end of the fourth quarter 1997. Symbols are as in Table 1A.
=
l1p-2 c1p-2w(2) cp-2 cp-2 cp-2 lp-2 lp-2 lp-2. STA F LAT LONG EL NAME SENSORS TELEMETRY
_
ERW % 48 27 14.4 122 37 30.2 0.389 Mt. Erie, WA A,BB C MPL % 47 28 08.2 122 11 06.2 0.122 Maple Valley A C,D QAW % 47 37 53.2 122 21 15.0 0.140 Queen Anne A C SEA % 47 39 18.0 122 18 30.0 0.030 Seattle A C,D SPW % 47 33 13.3 122 14 45.1 0.008 Seward Park, Seattle A,BB C UPS % 47 15 56.1 122 28 58.4 0.113 U. Puget Sound A D =
The seismograph network operated by the University of Washington consists of small numbers of broad-band and strong-motion sensors, plus over one hundred and forty short-period, vertical component, real-time-telemetered seismographic stations. Using real-time-telemetry data, the PNSN seismic recording system operates in an `event triggered' mode, recording data at 100 samples per sec. per channel. Data from stations with other telemetry systems are retrieved and integrated with the event-triggered data. Arrival times, first motion polarities, signal durations, signal amplitudes, locations and focal mechanisms (when possible) are determined in postprocessing. Digital data are processed for all teleseisms, regional events, and all locatable local events. Each trace data file has an associated `pickfile' which includes arrival times, polarities, coda lengths, and other data.
Through the end of 1997, the PNSN operated a SUNWORM data acquisition system running on a SUN SparcStation-5 computer. During the last half of 1997, an EARTHWORM system was developed. The EARTHWORM will replace the SUNWORM system as the main PNSN data-acquisition system. The SUNWORM system will continue to operate as a backup system.
PNSN broad-band stations TTW, ERW, and SPW record continuously, and individual events are extracted from the data. Stations LTY, RWW, LON, and GNW record digitally on-site, and data are retrieved via dial-up modem. We also receive data for selected events via Auto-DRM from U.S. National Seismograph Network (USNSN) stations NEW; in north-eastern Washington, and WVOR; in south-eastern Oregon. Data for specific events are provided to the PNSN from broad-band stations PIN, DBO, COR, and RAI (operated by Oregon State University and the University of Oregon).
Broad-band data in "raw" formats are stored on ongoing "network-archive" backups along with all unedited network-trigger trace data. Broadband data are also archived in merged and edited UW2 format on our "Master Event" tapes along with data from the PNSN short-period network, Our "Master Event" files are also translated to IRIS-SEED format and submitted to the IRIS Data Management Center for archive and distribution. All of our "Master Event" tapes of seismic trace data from 1980-1997 have now been reformatted to the IRIS-SEED format and submitted to the IRIS Data Management Center, where they are made available through the standard request mechanisms of the IRIS data-base system.
PNSN Quarterly Reports since 1994 have included moment-tensor focal mechanisms for earthquakes larger than magnitude 3.5. These have been provided to us by Dr. John Nabelek of Oregon State University (OSU) under support from USGS NEHRP Grant 1434-93-G-2326. OSU also provides broad-band data for some events from stations COR and RAI. The University of Oregon (UO) provides broad-band data for some events (from stations PIN and DBO. Phase data for earthquakes in northern Washington and southern British Columbia are exchanged with the Canadian Pacific Geoscience Centre promptly for significant events. We also exchange data occasionally with the Montana Bureau of Mines, Boise State University, and CALNET. The entire PNSN catalog has been contributed to the CNSS composite catalog located at the Northern California Earthquake Data Center. The PNSN section of the CNSS catalog is updated daily.
Publications wholly or partly supported under this operating agreement are listed in Appendix 2.
Figure 2 shows earthquakes of magnitude 2.0 or larger located in Washington and Oregon during this reporting period. Table 2 lists earthquakes recorded by the PNSN during 1997 which were reported felt. For comparison purposes, Table 3 gives information on seismic activity recorded at the PNSN annually since 1980.
During this reporting period there were 25 earthquakes reported felt west of the Cascades in Washington, ranging in magnitude from 2.2 to 5.4. Six earthquake were felt east of the Cascades. In Oregon, a total of 4 earthquakes were reported felt.
TABLE 2 =
Felt Earthquakes during 1997 DATE-(UTC)-TIME LAT(N) LON(W) DEPTH MAG COMMENTS yy/mm/dd hh:mm:ss deg. deg. km _ 97/01/19 18:03:48 45.03N 122.61W 16.0 2.4 22.0 km ESE of Woodburn, OR 97/02/01 10:10:56 46.63N 121.66W 0.0 0.8 21.9 km NW of Goat Rocks 97/02/01 11:31:56 46.63N 121.65W 1.0 1.4 21.6 km NW of Goat Rocks 97/02/06 22:17:18 47.55N 121.81W 3.3 2.3 5.2 km ESE of Fall City, WA 97/02/10 04:26:58 47.55N 122.28W 6.8 3.5 5.3 km SSE of Seattle, WA 97/03/22 06:05:34 45.18N 120.06W 0.8 3.9 79.7 km E of Maupin, OR 97/03/26 03:10:36 45.98N 118.35W 4.7 2.6 9.7 km S of Walla Walla, Wa 97/05/03 23:49:44 48.48N 121.70W 0.0 3.1 6.3 km SSE of Concrete, WA 97/05/18 08:28:08 48.66N 122.35W 12.7 3.2 14.2 km SE of Bellingham, WA 97/05/22 10:35:21 44.05N 122.51W 6.8 2.3 45.6 km E of Eugene, OR 97/05/22 13:57:10 44.05N 122.51W 8.1 2.6 45.4 km E of Eugene, OR 97/06/13 13:44:37 49.23N 123.56W 25.7 3.1 40.0 km WNW of Vancouver,BC 97/06/14 20:18:07 48.11N 121.58W 12.0 2.6 14.6 km S of Darrington, WA 97/06/23 19:13:27 47.58N 122.56W 7.7 4.9 5.6 km NE of Bremerton, WA 97/06/23 19:30:09 47.60N 122.55W 1.2 2.6 6.9 km NE of Bremerton, WA 97/06/23 21:46:24 47.60N 122.55W 0.9 3.1 6.9 km NE of Bremerton, WA 97/06/24 14:23:13 48.35N 119.88W 11.2 4.6 23.0 km W of Okanogan, WA 97/06/24 14:36:02 48.36N 119.86W 8.3 3.6 22.5 km W of Okanogan, WA 97/06/24 14:40:58 49.25N 123.61W 15.7 4.6 44.1 km WNW of Vancouver,BC 97/06/24 20:40:10 47.58N 122.55W 1.1 2.6 6.9 km ENE of Bremerton, WA
=
TABLE 2 (continued): Felt Earthquakes during 1997 DATE-(UTC)-TIME LAT(N) LON(W) DEPTH MAG COMMENTS yy/mm/dd hh:mm:ss deg. deg. km _ 97/06/26 07:11:04 47.60N 122.55W 0.3 1.2 7.0 km NE of Bremerton, WA 97/06/27 05:30:49 47.60N 122.58W 1.5 3.1 5.4 km NE of Bremerton, WA 97/06/27 10:47:49 47.58N 122.55W 0.9 3.9 6.9 km ENE of Bremerton, WA 97/07/03 22:54:43 47.75N 121.80W 0.0 1.7 13.9 km E of Duvall, WA 97/07/04 10:45:38 47.70N 120.03W 8.6 3.7 14.1 km S of Chelan, WA 97/07/11 01:26:01 47.58N 122.53W 1.0 2.2 7.2 km ENE of Bremerton, WA 97/07/11 01:28:55 47.58N 122.53W 6.1 3.5 7.0 km ENE of Bremerton, WA 97/08/01 12:55:03 47.30N 123.73W 0.0 3.4 36.7 km N of Aberdeen, WA 97/09/03 17:17:26 47.68N 120.26W 0.6 3.3 4.9 km NW of Entiat, WA 97/09/24 06:10:22 48.60N 123.08W 10.0 3.4 10.9 km NW of Friday Harbor, WA 97/10/14 18:20:49 47.58N 122.60W 6.5 2.3 3.8 km NE of Bremerton, WA 97/10/19 23:06:19 47.76N 121.85W 5.4 3.1 9.5 km ENE of Duvall, WA 97/11/18 01:53:06 46.13N 120.46W 15.6 3.9 50.4 km S of Yakima, Wa 97/11/26 00:05:34 47.78N 123.06W 46.6 3.7 32.7 km WNW of Poulsbo, WA 97/12/23 20:22:45 47.21N 123.88W 0.0 1.7 27.8 km NNW of Aberdeen, WA =
Three geographically separated magnitude 4.5+ earthquakes occurred within a 24 hour period on June 23 and 24. The first, and largest, earthquake occurred within the Puget basin near Bremerton. The second earthquake was east of the Cascade crest near Okanogan, and the third was located in British Columbia's Georgia Strait between Vancouver Island and the mainland.
The Bremerton earthquake, June 23 19:13 UTC, M 4.9: The magnitude 4.9 Bremerton earthquake occurred at a depth of about 8 km on June 23, 1997 at 19:13 UTC (12:13 PM PDT). The epicenter was approximately 5.7 km east-northeast of Bremerton, Washington. The earthquake, and several aftershocks, were widely felt throughout the greater Seattle area. A total of 80 events, including the mainshock, were located within a rectangular area 10 km square centered on the mainshock location, including two felt earthquakes about 3 minutes apart on July 11 (UTC). (see Table 1). After the end of July, aftershock activity diminished considerably.
The Okanogan earthquake, June 24 14:23 UTC, M 4.6: A magnitude 4.6 earthquake centered between Okanogan and Twisp, Washington, occurred at 14:23 UTC (7:23 AM PDT) on June 24, 1997 (Figure 11). It had a depth of about 11 km, and was widely felt in north-eastern Washington. A moderate aftershock (M 3.6), also felt, occurred 12 minutes after the mainshock. Nine more aftershocks, none larger than magnitude 2.7, were recorded and located.
The Georgia Strait earthquake, June 24 14:41 UTC, M 4.6: The second magnitude 4.6 earthquake on June 24 occurred beneath the Strait of Georgia at 14:41 UTC (7:41 AM PDT). Although out of the area normally covered by this report (and not shown in Fig. 2), this event was felt in northwestern Washington. A foreshock, magnitude 3.1, was felt on June 13. One aftershock, magnitude 1.5, was located nearby. A total of 9 aftershocks were reported felt.
Other notable activity during the year included sizable rockfalls on Mount Adams on August 29-31 and on October 20. In addition to earthquakes and blasts the PNSN has recorded a wide variety of volcanic signals, icequakes, rockfalls and debris flows, meteors, the space shuttle, and military exercises.
Last year, a supplement to this operating agreement provided funding for a followup detailed study of the Duvall sequence (and also for the strong-motion instruments mentioned earlier). The supplement began in August of 1996, and ran through November of 1997. George Thomas, a recent graduate, compiled and analyzed information on Duvall Sequence. He, and others, have prepared an article entitled "The May 3 1996 M5.4 Duvall, Washington Earthquake: Structure and Tectonic Implications" for submission to BSSA.
Table 3 includes the total number of events processed, including both locatable and unlocatable earthquakes and explosions (blasts), both within and outside the Pacific Northwest Seismograph Network area. The total number of events is approximately equal to the sum of the number of events outside the network, inside the network, and unlocated. It is not exact because a few earthquakes or blasts fall just outside the region that we defined as "Inside the Net" (117-125W, 42-49.5N) but were processed and flagged as if they were local events within the network. The total number of "Located" events within the PNSN Network is the sum of located earthquakes and located blasts.
=
TABLE 3
Annual counts of events recorded by the PNSN, 1980-1997
= n n | n n | n | n n. Year Total # Out of Net Inside Net _ Unlocated Located Total EQs(#felt) Blasts _ 80 4576 253 1075 3246 2874(18) 372 81 5155 291 1474 3385 2672(29) 713 82 4452 329 1824 2297 1948(20) 349 83 4489 405 2338 1745 1356(15) 389 84 3144 267 1095 1780 1409(16) 371 85 3560 266 1168 2122 1890(16) 232 86 2554 318 452 1776 1594(21) 182 87 1981 537 127 1304 966(22) 338 88 2249 507 114 1624 1263(19) 361 89 2781 501 137 2136 1835(38) 301 90 3433 717 204 2505 2096(26) 409 91 3083 675 315 2085 1687(26) 398 92 3522 891 235 2381 1993(22) 388 93 5594 731 626 4224 3877(35) 347 94 6243 900 1518 3816 3424(28) 392 95 5354 959 1462 2915 2539(16) 376 96 4741 911 1192 2628 2214(39) 414 97 3881 728 904 2239 1992(35) 247
=
The RACE system, discussed earlier, is a pager-based alarm system that updates earthquake locations mapped on a PC screen. When a "significant" event (magnitude 2.9 or larger) is located by the PNSN automatic systems, preliminary location and magnitude is sent within minutes to seismologists and the RACE system via pager. The same information is forwarded via fax and e-mail to others with critical need. A set of web-pages on earthquakes magnitude 3.3 and larger are automatically generated and linked to the PNSN web-site. These preliminary messages are rapidly followed by final processing and update of the RACE systems, faxes, e-mail, and web-site, within 20 minutes to an hour.
Summary lists for all earthquakes located by the PNSN since 1969 are available via anonymous ftp on ftp.geophys.washington.edu in the pub/seis_net subdirectory. This information is also available via the PNSN World-Wide-Web(WWW) site.
lp lp lp lp lp lp lp lp lp lp-2 np-2 np-2 np-2 np-2 np-2 np-2 np-2 np-2.
TABLE 4
Quarterly Comparison of Methods of Accessing PNSN list of most recent earthquakes, M>=2.0 =
Access Method 96-A 96-B 96-C 96-D 97-A 97-B 97-C 97-D = Finger Quake 83,000 90,300 62,900 63,000 66,800 95,000 97,000 118,063 World-Wide-Web 6,300 16,500 10,800 5,400 15,700 27,700 37,100 34,700
The PNSN has an educational outreach program to better inform the public, policy makers, and emergency managers about seismicity and natural hazards. We provide information sheets, lab tours, workshops, and media interviews, and have an audio library with several tapes, including a frequently updated "recent earthquakes" message. Outreach highlights this reporting period include: 1,300-3,000 calls per quarter to our audio library, Tours of the PNSN lab were provided to over 1,000 students, teachers, and parents.
Our World-Wide-Web site is an important element of our outreach, and it has steadily increased in popularity; handling more than 300,000 public contacts/quarter. An additional 400,000 Web-contacts/quarter are made through other earthquake-related pages hosted on the PNSN web-server; including the "CREW" Web-site, the very popular "Tsunami!" site, the "seismosurfing" page, and the "Council for the National Seismic System (CNSS)" Web-site
Seismic stations, telemetry links, and data acquisition equipment were maintained by Jim Ramey and Allen Strelow at the UW, Patrick McChesney (stationed at CVO in Vancouver, Washington), Pat Ryan (of the University of Oregon in Eugene, Oregon), and Don Hartshorn (of Pacific Northwest National Labs in Richland, WA). Bill Steele provided information to the public, while Sandra Corso handled routine data analysis and archiving of digital trace data in UW2 format. Sandy Stromme archived data in SEED format. Dr. Peter Lombard assisted with EARTHWORM development. Ruth Ludwin wrote reports, maintained the PNSN web-pages, and handled administrative tasks. Moment-tensor focal mechanisms for earthquakes larger than magnitude 3.5 were provided for our quarterly reports by Dr. John Nabelek of Oregon State University (OSU) under support from USGS NEHRP Grant 1434-93-G-2326. OSU also provides broad-band data from stations COR and RAI, which we archive with our trace-data files. The University of Oregon (UO) provides broad-band data from stations PIN and DBO.