Local Seismographic Network Stations in Au Sable Forks, NY

Following the mainshock, scientists and staff at the Lamont-Doherty Earth Observatory (LDEO) immediately went to the epicentral region with six digital portable seismographs to monitor aftershocks. The first station was installed about 1/2 day after the mainshock. Six more stations were installed the next day (see the table below).

By April 27, 2002, a week after the mainshock on April 20, 2002, 16 seismographic stations were deployed and monitoring the aftershocks in the region. This collaborative effort is lead by LDEO with instrument and personnel contributions from the Instrumental Software Technologies, Inc. (ISTI; New Paltz, NY), Center for Earthquake Research and Information (CERI), University of Memphis, PASSCAL facility of the Incorporated Research Institutions for Seismology (IRIS) through the PASSCAL Instrument Center at New Mexico Tech, and the Polaris Consortium, Canada.

We achieved an important milestone in monitoring earthquakes and evaluating their hazards through rapid cross-border (Canada-US) and cross-regional (Central US-NorthEastern US; SouthWest-NorthEastern US) collaborative efforts. Hence, ISTI staff -- Paul Friberg & Sid Helman, who live in Upstate New York joined LDEO staff and deployed the first portable station in the epicentral area; CERI dispatched two of their techinical staff to the epicenral area with four accelerometers and a broadband seismograph; the IRIS/PASSCAL facility shipped three digital seismographs and ancilliary equipment within one day of the request; the POLARIS Consortium, Canada sent a field crew of three with a near real-time, satellite telemetry based earthquake monitoring system. The Polaris station, KSVO (see Figure 2), powered by a solar panel and batteries, was already transmitting data to the central Hub in London, Ontario, Canada within a day after the field crew arrived in the Au Sable Forks area.

This collaboration allowed us to maximize the scarce resources available for monitoring this damaging earthquake and its aftershocks in the Northeastern U.S.

Figure 1. Earthquakes that occurred in New York and adjacent states during 1970-2001 (from PDE and LCSN catalog). Earthquakes are plotted with circles and the seismographic stations are plotted with triangles. Au Sable Forks earthquake on April 20, 2002 is plotted with a star and its source mechanism is indicated by a beach-ball (thrust faulting on 45 degree dipping fault plane at a depth of 11 km). Other major earthquakes in the past are indicated; 09/05/1944 Conwall-Massena earthquake (mb=5.8), 10/07/1983 Newcomb earthquake (mb=5.1), 01/16/1994 Reading, Pa earthquake (mb=4.6), and 06/09/1975 Altona, NY earthquake (m=4.0).

Figure 2. Location of the local portable seismograph network stations: small solid triangles = short-period seismometers, large solid triangles = broadband seismometers, inverted triangles = accelerometers, and diamond = real-time satellite telemtry station, KSVO. Mainshock and large aftershocks located by using regional network data are plotted with (stars). 19 small aftershocks that occurred during April 22-27 and located by using local portable seismographs are plotted with open circles. Towns around the epicentral area are indicated by squares, e.g., Keeseville and Au Sable Forks. Topographic contour lines for 100, 200 and 300 meters are plotted with dotted lines.

Portable Seismographic Station Deployment in Chronological Order

(Make & S/N)
(mo/da hh:mm)
FORD 44.513 73.766 365 Guralp DM24 CMG-40T 04/21 02:27-04/30 17:32 ISTI -
JEEP 44.475 73.631 144 Reftek 262 L22 04/21 14:06 LDEO  - 
SCAP 44.562 73.627 333 Reftek 526 L22 04/21 17:07 LDEO  - 
LAKE 44.495 73.716 354 Reftek 524 L28 04/21 20:45 LDEO  - 
MESS 44.571 73.715 283 Reftek 232 L22 04/21 23:16 LDEO  - 
BARN 44.593 73.629 256 Reftek 240 L28 04/22 00:44 LDEO  - 
BARN Guralp DM24 CMG-40T 04/25 20:00 CERI CD failed 
BILL 44.482 73.806 408 Reftek 6115 w/disk L22 04/23 21:52 ISTI/LDEO  - 
BILL K2/1365 L28 04/25 20:30 CERI STA/LTA=6
SKUN 44.535 73.594 180 K2/1368/solar L28 04/25 14:10 CERI STA/LTA=3, need battery
GREE 44.425 73.629 238 Reftek 479 L22 04/25 12:50 PASSCAL  - 
GREE K2/1361 L28 04/25 16:45 CERI STA/LTA=4
OREB 44.586 73.781 280 K2/1362/solar L4C/2 Hz 04/26 19:00 CERI STA/LTA=6
BROK 44.462 73.749 300 Reftek 525 L22 04/25 14:00 PASSCAL/LDEO DAS 393 failed 05/10
KSVO 44.552 73.686 381 Trident CMG-3ESP 04/26 18:04 POLARIS  - 
HALL 44.519 73.521 210 Reftek 117 L22 04/27 14:30 PASSCAL noisy site 05/10

K2 set with 1 g full scale, trigger on 0.1-12.5 Hz filter band set at 2% g, and sampling at 200 samples/sec

Station Table Station Table for Print


Between April 22 and April 27, we detected and located 19 small aftershocks (see Figure 2). The initial mainshock hypocenter determined from regional stations was only about 3 km NW and within the depth range of preliminary aftershock hypocenters. Thus, we were able to capture early aftershocks with a network that spans a 20 km-wide area centered above a 10 km deep source. The epicenter of the mainshock is about 8 km north of town of Au Sable Forks, and hence the April 20, 2002 Plattsburgh, NY earthquake is now formally called Au Sable Forks earthquake.

Additional Links

Following people have participated to the field work
CERI: field crew & support; Jim Bollwerk, Chris Watson, Arch Johnston, Mitch Withers
ISTI: Paul Friberg, Sid Hellman
POLARIS Consortium: field crew; Calvin Andrews, Mike Patten and Isa Asudeh; other personnel, John Adams, David Eaton and Gail Atkinson
LDEO: John Grenville, Jian Zhang, John Contino, Jeremiah Armitage, John Armbruster, Nano Seeber, Won-Young Kim, Art Lerner-Lam

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Won-Young Kim, Lamont-Doherty Earth Observatory of Columbia University, copyright©2002 all rights reserved