U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

CATALOG OF EARTHQUAKE HYPOCENTERS AT REDOUBT VOLCANO 

AND MT. SPURR, ALASKA: OCTOBER 12,1989 - DECEMBER 31,1990

by

John A. Power1, Gail D. March2, John C. Lahr1, Arthur D. Jolly1, Gina R. Cruse1

Open-File Report 93 - 685-A

This report is preliminary and has not been reviewed for conformity with U.S. 

Geological Survey editorial standards. Any use of trade, product, or firm names is 

for descriptive purposes only and does not imply endorsement by the U.S. 

Government.

1 Alaska Volcano Observatory 2 Alaska Volcano Observatory

U.S. Geological Survey, Alaska Division of Geological &

Geophysical Institute, Geophysical Surveys,

University of Alaska, 794 University Ave, Suite 200,

Fairbanks, AK 99775 Fairbanks, AK 99709
TABLE OF CONTENTS

INTRODUCTION.............................................................................................................3

INSTRUMENTATION...................................................................................................^

DATA ACQUISITION AND REDUCTION............,,...................,..........................?

VELOCITY MODELS.....................................................................................................9

DISCUSSION..................................................................................................................... 11

REFERENCES..................................................................................................................16

ILLUSTRATIONS

Figure 1. Location of AVO seismic stations in Cook Inlet area .............................4

Figure 2. Seismic stations in vicinity of Mt. Spurr..........................................................6

Figure 3. Seismic stations in vicinity of Mt. Redoubt.,....,,...,,,..,........,...,,,....,....?

Figure 4. Earthquake epicenters and cross sections from Mt. Spurr.......................... 12

Figure 5. Earthquake epicenters and cross sections from Mt. Redoubt,,,,,,,.......14

Figure 6. Focal depth versus time for located earthquakes..........................................15

APPENDIX

APPENDIX A. Locations of AVO seismic stations....................................................18

APPENDIX B. Stations used for triggering and recording ..........................................20

APPENDIX C. Seismic station response curves,,,,,,,,,,,,,,,,,,,,,..................36
INTRODUCTION

The Alaska Volcano Observatory (AVO), a cooperative program of the U.S. 

Geological Survey, the Geophysical Institute of the University of Alaska, Fairbanks, 

and the Alaska Division of Geological and Geophysical Surveys, began a program of 

seismic monitoring at potentially active volcanoes in the Cook Inlet region in 1988. 

Seismic monitoring of this area was previously accomplished by two independent 

seismic networks operated by the U.S. Geological Survey (Northern Cook Inlet) and 

the Geophysical Institute (Southern Cook Inlet). In 1989 the AVO seismic program 

consisted of three small-aperture networks of six, five, and six stations on Mt. Spurr, 

Redoubt Volcano, and Augustine Volcano respectively. Thirty-five other stations 

were operated in the Cook Inlet region as part of the AVO program. During 1990 

six additional stations were added to the Redoubt network in response to eruptive 

activity, and three stations were installed at Iliamna Volcano. The principal 

objectives of the AVO program have been the seismic surveillance of the Cook Inlet 

volcanoes and the investigation of seismic processes associated with active volcanism.

The locations of seismograph stations operated by AVO between 1988 and 1990 

are shown in Figure 1. Geographic coordinates, elevations, and the installation date 

of each of the stations are contained in Appendix A. Signals from each of the 

stations are telemetered to Fairbanks, where recording and analysis take place. Data 

is recorded digitally in event-detection mode on a PC/AT system and continuously 

and in event-detection mode on a Masscomp system (Alaska Volcano Observatory 

Staff, 1990). The two event-detection systems employ different triggering 

parameters, with the PC/AT system having greater sensitivity for events in close 

proximity to the volcanoes. Data is also recorded on Helicorders, a Real-time 

Seismic Amplitude Measurement (RSAM) system (Murray and Endo, 1989; Endo 

and Murray, 1991), and a Seismic Spectral Amplitude Measurement (SSAM) system 

(Stephens and others, in press). A description of the various components of the 

computer systems, their networking, and associated software is given by March and 

Power (1990).

Following a 23 year period of quiescence, Redoubt Volcano erupted between 

December 14,1989 and April 21,1990. The eruption was accompanied by thousands 

of earthquakes (Alaska Volcano Observatory Staff, 1990). Throughout the eruption 

sequence, data from the PC/AT system provided the primary means of determining 

earthquake hypocenters. This report catalogs the earthquake hypocenters and 

magnitudes calculated from data collected between October 12, 1989 and December 

31, 1990 on the PC/AT acquisition system, provides station locations, statistics, and 

calibrations, and outlines which stations were recorded and used in triggering the 

PC/AT system.
Redoubt 

Volcano

lliamna 

Volcano

aA. Augustine 

Volcano

Location map for Cook Inlet

Figure 1. Location of seismic stations operated by the Alaska Volcano Observatory 

between 1988 and 1990.
INSTRUMENTATION

In October 1989 six seismic stations, SPU, CRP, CGL, NCG, BGL, and CKL, 

were in operation around Mt. Spurr (Figure 2). Between October 1989 and 

February 1990 the Redoubt network consisted of 5 stations; RED, RDN, NCT, DFR, 

and RDT. RDT was a three-component station with north-south and east-west 

oriented horizontal instruments. On February 2, 1990 station DRE was installed 

both to augment monitoring capability at Redoubt Volcano and to aid in monitoring 

for eruption-related floods in the Drift River valley. In March stations RSO, REF, 

and RWS were installed on the Redoubt cone to augment the existing network 

(Figure 3). Station RWS was replaced by station RDW on September 9. On 

September 10 and 24 two additional stations, RS1 and RS2, were added to form a 

tripartite array with station RSO. The horizontal instruments at station RDT were 

moved to station RED on August 30, 1990. Station RDN was disabled as a result of 

eruptive activity between January 2 - 9, 1990 and February 11 - November 9, 1990. 

Eruptive activity on December 14, 1989 apparently damaged the RDN seismometer, 

altering the frequency response. This problem was corrected on November 9, 1990 

when the seismometer was replaced. Other stations experienced minor technical 

trouble and short interruptions in telemetry during the report period. Information 

on which stations were recorded and used in triggering on the PC/AT system is 

contained in Appendix B.

AVO seismic stations in the northern portion of Cook Inlet are maintained by 

the U. S. Geological Survey, and in southern Cook Inlet by the Geophysical Institute 

(Figure 1). Each institution uses slightly different field equipment. As this report 

catalogs only hypocenters at Mt. Spurr and Redoubt Volcano, just equipment at and 

operation of stations at these volcanoes is covered.
SPURR SEISMIC STATIONS 1989 - 1990

25'

20' -

15'

61" 10' -

40' 30' 20' 10' 152' 50'

Figure 2. Seismic stations in vicinity of Mt. Spurr.

Stations at Mt. Spurr and Redoubt Volcano consist of a vertical component 

seismometer with a frequency of 1 HZ (Mark Products L-4C), an A1VCO (Rogers 

and others, 1980), radio transmitter, antenna, and batteries (which in some cases are 

float-charged by a solar panel). The two exceptions to this are stations RED and 

DRE, which differ only in the use of a monitron VCO. Signals from each station are 

relayed to radio receivers and telemetered via frequency-multiplexed phone lines to 

the AVO offices in Fairbanks. Appendix C illustrates the response characteristics of 

the entire system from the seismometer to the computer screen for the various 

stations.
REDOUBT SEISMIC STATIONS 1989 - 1990

35'

30'

60° 25'

DFR A

A NCT

10 KM

A ORE

RDT A

153 50' 40' 30'

Figure 3. Seismic stations in vicinity of Redoubt Volcano. Stations RS1 and RS2 are 

not shown.

DATA ACQUISITION AND REDUCTION

On October 12, 1989 event-triggered recording began on a PC/AT-based seismic 

data acquisition system (Lee and others, 1989). This system uses the program 

MDETECT (Lee and others, 1988) to digitize, detect, and record sixteen channels of 

data. Between October 12, 1989 and December 31, 1990 the system triggered over 

12,000 times.

When the PC/AT system was first installed in Fairbanks, the sixteen input 

channels were distributed evenly among stations on Mt. Spurr, Redoubt Volcano,
and Augustine Volcano. Through the course of the 1989-90 eruption of Redoubt 

Volcano, input channels were shifted from stations at Augustine and then Mt. Spurr 

to stations closer to Redoubt Volcano and to new stations added to the Redoubt 

network. After January 5, 1990, Augustine stations were not recorded on the PC/AT 

system and after March 10, 1990, stations near Mt. Spurr were not used to trigger 

event recording.

Recorded events were visually inspected on a computer screen and classified as 

either a volcano-tectonic earthquake, a long-period event, an explosion event, a 

regional tectonic earthquake, a teleseismic event, or a non-seismic event. After 

additional spectral analysis (Lahr, and others, in press), some events at Redoubt 

Volcano were reclassified as hybrid events (see Power and others, in press, for a 

description of the various event types). Events were only analyzed for reclassification 

as hybrids between December 13, 1989 and January 2, 1990. If an event was 

classified as either a volcano-tectonic or long-period event and had four or more 

distinct phases at three or more stations, it was selected for location. No attempt was 

made to locate long-period events with emergent arrivals or low-frequency events in 

the Spurr area. The initial examination on the computer screen, event classification, 

the determination of P and S arrival times, direction of first motion, and the period 

and amplitude of the maximum recorded signal were determined using the program 

XPICK (Robinson, 1990). Earthquake hypocenters and magnitudes were calculated 

using the program HYPOELLIPSE (Lahr, 1989). Computed magnitudes 

approximate the Richter local magnitude as outlined by Eaton and others, (1970). 

Earthquake depths are computed with respect to sea level, with the negative values 

reflecting height above sea level.

HYPOELLIPSE expresses the quality of earthquake solutions using a number 

of parameters which include: RMS (the root mean square residual); SEH (the 68 

percent confidence limit in the least well-constrained direction); SEZ (the 68 percent 

confidence limit in depth); GAP (the largest azimuthal separation between stations 

measured from the epicenter); NP, the number of P arrivals used in the solution; and 

NS, the number of S arrivals used in the solution. More detailed information on 

these parameters is given by Lahr (1989). A complete discussion of the earthquake 

location process is given by Lee and Stewart (1981).

Earthquake hypocenter determinations contain both systematic and random 

errors. Systematic errors can result from errors in the velocity model, 

misidentification of phases, or systematic timing errors. Systematic errors affect the 

accuracy of the hypocenter determination and can be evaluated through controlled 

experiments such as locating man-made explosions. Random errors result from 

timing errors and are estimated for each earthquake through the use of standard
statistical techniques. Random errors affect the precision with which hypocenters 

can be calculated.

The quality of each solution was checked using a computer algorithm which 

identifies those events without magnitude, fewer than three P phases, fewer than one 

S phase, or SEH or SEZ greater than 15.0 km. Additionally all events at Redoubt 

Volcano with depths greater than 10 km and volcano-tectonic events with depths less 

than 4 km were reinspected. Corrections were made as required.

VELOCITY MODELS

For earthquakes which occur at Mt. Spurr, the velocity model used to calculate 

hypocenters is:

LAYER DEPTH P VELOCITY (km/s) VP/VS (km/s) 

(TO TOP OF LAYER)

1 -3.2 5.1 1.81

2 -2.2 5.5 1.81

3 -5.05 6.3 1.74

Depths are referenced to sea level, with negative values reflecting height above 

sea level. Below 27.05 km depth this model is underlain by a uniform halfspace with 

P-wave velocity of 7.2 km/s and VP/VS of 1.78 km/s. Station corrections for use with 

this model are shown below:
STATION P-DELAY (Seconds) S-DELAY (Seconds)

BGL -0.12 0.00

BRLK -0.62 -1.20

CGL 0.04 -0.11

CKL 0.07 0.00

CNP -0.44 0.00

CRP 0.11 0.00

CUT 0.41 0.00

DFR -0.37 -0.77

GHO 0.36 0.00

ILM -0.63 -1.40

KNK -0.85 -0.54

NCT -0.24 -0.66

NKA 2.18 0.00

NNL 1.21 0.00

PME 0.18 0.00

RON -0.42 -0.69

RDT -0.49 -0.88

RED -0.43 -1.00

SKL -0.20 -0.80

SLV -1.10 0.00

SPU 0.04 -0.06

SVW 0.00 -0.65

The Spurr model was derived by minimizing the average root-mean-square (rms) 

residual of observed versus computed travel times (Jolly and others, 1991).

At Redoubt Volcano the velocity model used is:

LAYER DEPTH P VELOCITY (km/s) VP/VS(km/s) 

(TO TOP OF LAYER)

1 -3.00 2.9 1.80

2 -1.70 5.1 1.80

3 1.50 6.4 1.72

In this model depths are referenced to sea level; negative values reflect height 

above sea level. Below 17 km depth this model is underlain by a uniform halfspace 

with P-wave velocity of 7.0 km/s and a VP/VS ratio of 1.780. Station corrections for 

use with this model are shown below:

10
STATION P-DELAY (Seconds) S-DELAY (SECONDS)

DFR 0.00 -0.10

ORE 0.00 0.00

NCT 0.00 0.06

RON -0.01 -0.04

RDT 0.00 -0.02

RDTE 0.00 -0.02

RDTN 0.00 -0.02

ROW 0.02 -0.12

REF 0.01 0.00

RED -0.02 -0.05

REDE -0.02 -0.05

REDN -0.02 -0.05

RSO 0.00 0.00

RS1 0.00 0.00

RS2 0.00 0.00

S phases at DFR, RON, REF, RSl, RS2, and RSO are not used. S phases at the 

remaining stations are used with reading errors set to 0.14 seconds. This model was 

derived by Lahr and others, (in press) by minimizing the average root-mean-square 

(rms) residual of observed versus computed travel times and developing station 

corrections based on explosion data collected during the summer of 1991.

DISCUSSION

Origin times, focal coordinates, magnitudes, and related parameters for 9877 

earthquakes from October 12, 1989 through December 31, 1990 are contained in a 

file on the accompanying floppy disk. Epicenters of 144 of these events occur with 20 

km of the summit of Mt. Spurr (Figure 4). The remaining 9733 earthquakes occur in 

the vicinity of Redoubt Volcano and are associated with the 1989-90 eruption (Power 

and others, in press).

11
20-

61° 15'

MT SPURR SEISMICITY

OCTOBER 12, 1989 - DECEMBER 31, 1990

MAGNITUDE!

" -9.0+

a 1.0+

D 2.0+

D

30' 20' 10' 152

SOUTH

SB 

Q

NORTH WEST

IB

EAST

0 4 8 12 16 20 24 

DISTANCE (KM)

0 4 8 12 16 20 24 

DISTANCE (KM)

Figure 4. Epicenter map and cross sections for Mt. Spurr from October 12,1989 

through March 10,1990.

12
Earthquakes located at Mt. Spun by the PC/AT system form a dominant cluster 

beneath the summit of Mt. Spurr. Events in this cluster are shallow and range from - 

3.0 to 1.0 km depth. This cluster of events is a long-standing feature of seismic 

activity at Mt. Spurr (Jolly, and others, 1991). Magnitudes of located events at Mt 

Spurr ranged from -0.6 to 2.7 during the report period. In March 1990 stations on 

the PC/AT system were shifted from stations in the Mt. Spurr network to new 

stations at Redoubt Volcano. The PC/AT system did not trigger on stations in the 

Mt. Spurr network for the remainder of the report period.

At Redoubt Volcano a few small earthquakes were located during October and 

November 1989. A vigorous swarm of long-period earthquakes occurred in the 23- 

hour period prior to the onset of the 1989-90 eruption on December 14, 1989. 

Shallow swarms (-3 to 1 km depth) of volcano-tectonic earthquakes followed 

explosive events on December 15 and 19. A deeper swarm of volcano-tectonic 

earthquakes was initiated by explosive events on December 15. This deeper swarm 

increased in intensity in late December and declined gradually through the 

remainder of the eruption. Additional swarms of long-period events are described by 

Stephens and others, (in press). Generally only those long-period events which 

occurred during swarms on December 13 - 14 and December 26, 1989 - January 2, 

1990 were large enough to locate. A map of earthquake epicenters for Redoubt 

Volcano is shown in Figure 5. A plot of focal depth versus time of all located events 

in the Redoubt network between October 12, 1989 and December 31, 1990 is shown 

in Figure 6. For more detailed descriptions and analysis of the seismicity 

accompanying the 1989-90 eruption of Redoubt Volcano see Chouet and others, (in 

press), Lahr and others, (in press), Power and others, (in press), and Stephens and 

others, (in press).

13
KEDOUBT SU1SM1CITY

OCTOBER 12, 1989 - DECEMBER 31, 1990

35'

30' -

60° 25'

.... i V ... I .... I ...,,.,.

153 501 40' 30'

SOUTH NORTH WEST EAST

4 8 12 18 

DISTANCE (KM)

4 8 12 16 

DISTANCE (KM)

20

Figure 5. Epicenters map and cross sections for Redoubt Volcano from October 12, 

1989 through December 31,1990.

14
REDOUBT TIME - DEPTH PLOT

OCTOBER 1989 - DECEMBER 1990

0 H

-10 H

II I i i I I I ii rTT~TT~n~r"rTTT~n~T~r~n ""i I n I ' i I i i I ' ' l~rr

'OCT NCV DEC ' 1990 FEB MAR APR MAY JUN JU, AUG SEP CCT NCV DEC

1 OCT 89. o o TIME

Figure 6. Focal depth versus time for all located events in the Redoubt network 

between October 12,1989 and December 31,1990.

15
REFERENCES

Alaska Volcano Observatory Staff, 1990, The 1989-90 eruption of Redoubt Volcano.

EOS Transactions of the American Geophysical Union. 71:265-275. 

Chouet, B. A., Page, R A, Stephens, C.D., Lahr, J. C, and Power, J. A, in press,

Precursory swarms of long-period events at Redoubt Volcano (1989 -90),

Alaska: Their origin and use as a forecasting tool: Journal of Volcanology

and Geothermal Research. 

Eaton, J. P., O'Neil, M. E., and Murdock, J. N., 1970, Aftershocks of the 1966

Parkfield-Cholame, California earthquake: a detailed study: Bulletin of the

Seismological Society of America, 60:1151-1197. 

Endo, E.T., and Murray, T.L., 1991, Real-time Seismic Amplitude Measurement

(RSAM): A volcano monitoring and prediction tool: Bulletin of

Volcanology, 53: 533-545. 

Jolly, A. D., Page, R. A., Stephens, C. D., Lahr, J. C., Power, J. P., and Cruse, G. R.,

1991, Seismicity in the vicinity of Mt. Spurr Volcano, South-central, Alaska,

based on a revised velocity model: EOS Transactions of the American

Geophysical Union., 567. 

Lahr, J. C., Chouet, B. C., Stephens, C. D., Power, J. A, and Page, R. A, in press,

Earthquake location and error analysis procedures for a volcanic sequence:

application to 1989 -1990 eruptions at Redoubt Volcano, Alaska: Journal of

Volcanology and Geothermal Research. 

Lee, W. H. K., and Stewart, S. W., 1981, Principals and applications of

microearthquake networks: Academic Press, New York, 293 pp. 

Lee, W. H. K., Tottingham, D. M., and Ellis, J. O., 1988, A PC-based seismic data

acquisition and processing system: U.S. Geological Survey, Open-file Report

88-751, 31 pp. 

Lee, W. H. K. (Editor), 1989, Toolbox for seismic data acquisition, processing and

analysis: IASPEI Software Library, Vol. 1, Seismological Society of America,

El Cerrito, 284 pp. 

March, G. D., and Power, J. A, 1990, A networked computer configuration for

seismic monitoring of volcanic eruptions: U.S. Geological Survey, Open-file

Report 90-422,19 pp. 

Murray, T. L., and Endo, E. T., 1989, A real-time seismic amplitude measurement

system (RSAM): U.S. Geological Survey, Open-file Report 89-684, 26 pp.

16
Power, J. A., Lahr, J. C., Page, R. A, Chouet, B. A, Stephens, C.D., Harlow, D. H., 

Murray, T. L., and Davies, J. N., in press, Seismic evolution of the 1989 - 90 

eruption of Redoubt Volcano, Alaska: Journal, of Volcanology and 

Geothermal Research.

Robinson, M., 1990, Xpick user's manual v2.7: Seismology Lab, Geophysical 

Institute, University of Alaska, 93 pp.

Rogers, J. A, Maslak, S., and Lahr, J. C., 1980, A seismic electronic system with

automatic calibration and crystal reference: U.S. Geological Survey. Open-file 

Report 80-324.130 pp.

Stephens, C. D., Chouet, B. A, Page, R. A, Lahr, J. C, and Power, J. A, in press, 

Seismological aspects of the 1989-1990 eruptions at Redoubt Volcano, 

Alaska: the SSAM perspective: Journal of Volcanology and Geothermal 

Research.

17
APPENDIX A

Appendix A lists stations operated by the Alaska Volcano Observatory in the Cook 

Inlet region between October, 1989 and December, 1990. The list includes 

geographic coordinates, elevation, installation date, and organization responsible for 

maintenance for each station.

Station

BGL

CGL

CKL

CKN

CRP

NCG

SPU

REF

RDM

ROW

RS1

RS2

RSO

RED

REDE

REDN

REDL

RWS

DFR

ORE

NOT

RDT

RDTN

RDTE

INE

INW

IVS

AUH

AUI

AUIE

AUIN

AUP

AUS

AUW

AUE

AUL

ODD

SKN

NNL

CNP

Latitude

61.2635

61.3077

61.1965

61.2073

61.2670

61.4037

61.1817

60.4892

60.5230

60.4827

60.4602

60.4630

60.4622

60.4190

60.4190

60.4190

60.1490

60.4880

60.5920

60.5832

60.5617

60.5738

60.5738

60.5738

60.0608

60.0677

60.0092

59.3638

59.3352

59.3352

59.3352

59.3623

59.3600

59.3670

59.3590

59.3822

58.9298

61.9803

60.0443

59.5258

Longitude Elevation (m)

-152.3905

-152.0067

-152.3378

-152.1815

-152.1555

-152.1567

-152.0543

-152.7017

-152.7385

-152.8095

-152.7580

-152.7573

-152.7538

-152.7720

-152.7720

-152.7720

-152.7720

-152.7745

-152.6862

-152.5868

-152.9297

-152.4062

-152.4062

-152.4062

-153.6250

-153.1325

-153.0808

-153.4435

-153.4277

-153.4277

-153.4277

-153.4205

-153.4307

-153.4708

-153.3722

-153.4345

-153.6430

-151.5297

-151.2893

-151.2360

1173

1082

1265

735

1622

1244

800

1801

1372

1813

1864

1953

1921

1067

1067

1067

1067

2713

1097

489

1166

930

930

930

1585

1219

2332

900

293

293

293

1033

1226

320

172

360

622

564

381

564

Installation 

date

890813

810922

890805

910819

810826

890806

710810

900314

880813

900907

900910

900910

900301

740000

900830

900830

900830

900315

880815

900201

880814

710809

710809

710809

900829

900829

900829

781201

780406

860600

860600

870922

900901

860700

870830

801029

810817

720808

720824

830701

Maintainer

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

USGS

UAGI

UAGI

UAGI

UAGI

UAGI

UAGI

UAGI

UAGI

UAGI

UAGI

UAGI

UAGI

UAGI

USGS

USGS

USGS

18
Station Latitude Longitude Elevation (m) Installation Maintainer

	date

HOM 59.6583 -151.6433 198 760800 UAGI

PDB 59.7878 -154.1925 305 780909 UAGI

OPT 59.6527 -153.2297 450 740000 UAGI

PDB 59.7878 -154.1925 305 780909 UAGI

MMN 59.1852 -154.3367 442 810822 UAGI

BGM 59.3927 -155.2293 625 780908 UAGI

SHU 58.6280 -152.3488 34 740000 UAGI

XLV 59.4547 -151.6717 320 870916 UAGI

19
APPENDIX B

Appendix B shows stations being recorded on the PC/AT acquisition system on a 

daily scale for the period October 8,1989 through December 31,1990. The period 

from October 8,1989 through December 11,1989 is not well documented, as few 

events were recorded during this period. The period from December 12,1989 

through December 31, 1990 is well documented. Different patterns are used to 

distinguish whether stations were used in event triggering or were only recorded.

20
BBSBSSBSSB

Unknown

Record

| Record and 

trigger

21
CDss

O) O) O) O)

Unknown

Record

Record and 

trigger

22
O)O)O) 

cococo

gg co cb ^

gg

Unknown

I Record

| Record and 

trigger

23
Unknown

Record

Record and 

trigger

24
a ^o CD 

®

ta 

g CD 

°

- B.

03 CL

8B.
I I I I I I I I I I

(Q CD(Q O

CD ° - a

03 

Q.

73 C

§ 3 ^ a 1
H

IIi 

i I i tss 

Hi

^

t III \iIII !§ ^s 

H *iss ^ sis 

ft H 

H iS ' *S ' s^

^ H 

^

^ ^ 

^ ^ " Sjss " ^ ^ ^ 

H

% % " %

^ 1 

^ fl 111

 11'\

 |i I'I I'I 

II

(Q fD S O 

0> 

O

- 3.

03 

0.

8 a

c

;* 3
10

00

I I I I I I I I I I I I

CD O -1 a

CD

CD 3

8 § a i
Unknown

Record

Record and 

trigger

29
532

70 W 

I

I I I I I I

OJ

o

i i I I i i i i I I 1 i 7/1/90

7/2/907/3/90

7/4/907/5/907/6/907/7/907/8/90

7/9/907/10/90

7/11/907/12/907/13/907/14/907/15/907/16/90

7/17/907/18/907/19/907/20/907/21/907/22/907/23/907/24/907/25/90

7/26/907/27/90

7/28/907/29/907/30/907/31/908/1/90

(Q (Q

ca 

a
co3333333333333333333 35

I Unknown

I Record

| Record and 

trigger
U) K»

9/1/909/2/909/3/90

9/4/909/5/909/6/909/7/909/8/909/9/90

9/10/90

9/11/909/12/909/13/909/14/909/15/909/16/909/17/90

9/18/909/19/909/20/90

9/21/909/22/909/23/90

9/24/90

9/25/909/26/90

9/27/909/28/90

9/29/909/30/90

10/1/90

a 

g

CD O 

(B 

203 Q.

8 a

C 

I
o 9>

i BBB55555S5

Unknown

Record

Record and 

trigger

33
I Unknown

I Record

| Record and 

trigger

34
Unknown

Record

Record and 

trigger

35
APPENDIX C

Response curves for stations monitored by the PC/AT seismic acquisition system 

from December, 1989 through December, 1990. Calibration data is not available for 

stations CGL, REDN, REDE, and NNL during the report period. No calibration 

data is available for station RED between August 30 and December 21,1990. Prior 

to August 30,1990, station RED used a monitron VCO, so calculation of its response 

curve uses separate parameters. All other stations use the A1VCO (Rogers and 

others, 1980).

36
Station Response Curves

Frequency

0.012589

0.015849

0.019953

0.025119

0.031623

0.039811

0.050119

0.063096

0.079433

0.100000

0.125893

0.158489

0.199526

0.251189

0.316228

0.398107

0.501187

0.630957

0.794328

1.000000

1.258925

1.584893

1.995262

2.511886

3.162278

3.981072

5.011872

6.309573

7.943282

10.000000

12.589254

15.848932

19.952623

25.118864

31.622777

39.810717

50.118723

63.095734

79.432823

100.000000

CRP

4.655144

12.384398

29.40626

98.60799

344.318

761.632322

1837.04042

5322.7848

13071.0453

31720.1311

72633.8622

155046.974

329621.5

698558.9

1418157

2905045

5874843

11652004

21345948

35751170

53619020

73480290

95757090

121987580

154065730

193993800

231453300

284979500

347787700

414419200

475127900

548455700

535372500

551881200

422994000

386860500

305201000

230790300

97295250

74017320

NCG

9.879016

26.281822

62.40514

209.26311

730.702

1616.31475

3898.51565

11295.8646

27739.0056

67315.5723

154141.545

329036.339

699513.5

1482462.1

3009573

6165005

12467427

24727556

45299772

75870130

113788780

155937810

203213010

258878620

326953970

411688200

491183700

604775500

738065300

879468800

1008303100

1163917300

1136152500

1171186800

897666000

820984500

647689000

489776700

206477250

157077480

CGL

no

calibration

available

SPU

20.453144

54.412898

129.20126

433.25049

1512.818

3346.3574

8071.3405

23386.5341

57429.7962

139367.635

319128.87

681224.489

1448246.5

3069233.9

6230907

12763795

25812093

51195004

93786948

157078670

235584020

322847790

420724590

535972580

676913230

852343800

1016928300

1252104500

1528062700

1820819200

2087552900

2409730700

2352247500

2424781200

1858494000

1699735500

1340951000

1014015300

427482750

325207320

BGL

5.266

14.0095

33.265

111.5475

389.5

861.575025

2078.10003

6021.24978

14786.2503

35882.5012

82165.0025

175392.505

372875

790225

1604250

3286250

6645750

13181000

24147000

40442500

60655000

83122500

108322500

137995000

174282500

219450000

261825000

322375000

393425000

468800000

537475000

620425000

605625000

624300000

478500000

437625000

345250000

261075000

110062500

83730000

CKL

5.560896

14.794032

35.12784

117.79416

411.312

909.823226

2194.47363

6358.43976

15614.2803

37891.9213

86766.2426

185214.485

393756

834477.6

1694088

3470280

7017912

13919136

25499232

42707280

64051680

87777360

114388560

145722720

184042320

231739200

276487200

340428000

415456800

495052800

567573600

655168800

639540000

659260800

505296000

462132000

364584000

275695200

116226000

88418880

RDT

7.983256

21.238402

50.42974

169.10601

590.482

1306.14774

3150.39964

9128.21466

22415.9555

54397.8719

124562.144

265895.037

565278.5

1197981.1

2432043

4981955

10074957

19982396

36606852

61310830

91952980

126013710

164216910

209200420

264212270

332686200

396926700

488720500

596432300

710700800

814812100

940564300

918127500

946438800

725406000

663439500

523399000

395789700

166854750

126934680

DFR

9.078584

24.152378

57.34886

192.30789

671.498

1485.35534

3582.64444

10380.6346

25491.4955

61861.4321

141652.464

302376.678

642836.5

1362347.9

2765727

5665495

11457273

22724044

41629428

69722870

104569220

143303190

186747990

237903380

300463030

378331800

451386300

555774500

678264700

808211200

926606900

1069612700

1044097500

1076293200

824934000

754465500

595211000

450093300

189747750

144350520

37
Station Response Curves

NCT

4.865784

12.944778

30.73686

103.06989

359.898

796.095323

1920.16442

5563.63479

13662.4953

33155.4311

75920.4623

162062.675

344536.5

730167.9

1482327

3036495

6140673

12179244

22311828

37368870

56045220

76805190

100089990

127507380

161037030

202771800

241926300

297874500

363524700

433171200

496626900

573272700

559597500

576853200

442134000

404365500

319011000

241233300

101697750

77366520

RDM*

4.52876

12.04817

28.6079

95.93085

334.97

740.954522

1787.16602

5178.27481

12716.1753

30858.9511

70661.9021

150837.554

320672.5

679593.5

1379655

2826175

5715345

11335660

20766420

34780550

52163300

71485350

93157350

118675700

149882950

188727000

225169500

277242500

338345500

403168000

462228500

533565500

520837500

536898000

411510000

376357500

296915000

224524500

94653750

72007800

RDN +

5.076424

13.505158

32.06746

107.53179

375.478

830.558324

2003.28842

5804.48478

14253.9453

34590.7312

79207.0624

169078.375

359451 .5

761776.9

1546497

3167945

6406503

12706484

23277708

38986570

58471420

80130090

104422890

133027180

168008330

211549800

252399300

310769500

379261700

451923200

518125900

598089700

583822500

601825200

461274000

421870500

332821000

251676300

106100250

80715720

REF

4.613016

12.272322

29.14014

97.71561

341.202

754.739722

1820.41562

5274.6148

12952.7553

31433.0711

71976.5421

153643.834

326638.5

692237.1

1405323

2878755

5821677

11546556

21152772

35427630

53133780

72815310

94890510

120883620

152671470

192238200

229358700

282400500

344640300

410668800

470828100

543492300

530527500

546886800

419166000

383359500

302439000

228701700

96414750

73347480

RSO

5.16068

13.72931

32.5997

109.31655

381.71

844.343525

2036.53802

5900.82478

14490.5253

35164.8512

80521.7024

171884.655

365417.5

774420.5

1572165

3220525

6512835

12917380

23664060

39633650

59441900

81460050

106156050

135235100

170796850

215061000

256588500

315927500

385556500

459424000

526725500

608016500

593512500

611814000

468930000

428872500

338345000

255853500

107861250

82055400

RWS

3.854712

10.254954

24.34998

81.65277

285.114

630.672918

1521.16922

4407.55484

10823.5352

26265.9909

60144.7818

128387.314

272944.5

578444.7

1174311

2405535

4864689

9648492

17675604

29603910

44399460

60845670

79292070

101012340

127574790

160637400

191655900

235978500

287987100

343161600

393431700

454151100

443317500

456987600

350262000

320341500

252723000

191106900

80565750

61290360

ROW

4.697272

12.496474

29.67238

99.50037

347.434

768.524922

1853.66522

5370.9548

13189.3353

32007.1911

73291.1822

156450.114

332604.5

704880.7

1430991

2931335

5928009

11757452

21539124

36074710

54104260

74145270

96623670

123091540

155459990

195749400

233547900

287558500

350935100

418169600

479427700

553419100

540217500

556875600

426822000

390361500

307963000

232878900

98175750

74687160

RS2

4.549824

12.104208

28.74096

96.37704

336.528

744.400822

1795.47842

5202.35981

12775.3203

31002.4811

70990.5621

151539.124

322164

682754.4

1386072

2839320

5741928

11388384

20863008

34942320

52405920

71817840

93590640

119227680

150580080

189604800

226216800

278532000

339919200

405043200

464378400

536047200

523260000

539395200

413424000

378108000

298296000

225568800

95094000

72342720

RDTN

2.295976

6.108142

14.50354

48.63471

169.822

375.64671 1

906.051611

2625.2649

6446.80513

15644.7705

35823.9411

76471.1321

162573.5

344538.1

699453

1432805

2897547

5746916

10528092

17632930

26445580

36241410

47228610

60165820

75987170

95680200

114155700

140555500

171533300

204396800

234339100

270505300

264052500

272194800

208626000

190804500

150529000

113828700

47987250

36506280

* Before 2/15/90 

+ After 8/30/90

38
Station Response Curves

Monitron VCO

RDTE

2.274912

6.052104

14.37048

48.18852

168.264

372.200411

897.739211

2601.1799

6387.66013

15501.2405

35495.2811

75769.5621

161082

341377.2

693036

1419660

2870964

5694192

10431504

17471160

26202960

35908920

46795320

59613840

75290040

94802400

113108400

139266000

169959600

202521600

232189200

268023600

261630000

269697600

206712000

189054000

149148000

112784400

47547000

36171360

RED#

no

calibration

available

REDN

no

calibration

available

REDE

no

calibration

available

NNL

no

calibration

available

Frequency

0.1

0.2

0.4

0.5

0.8

1.0

1.7

2.0

2.5

3.3

5.0

10

15

20

30

40

50

RED##

4606

36106

182915

479641

1328618

2428016

5847094

7517646

9981755

13942052

20309967

30515013

34959133

34672125

26028727

15837535

2503975

ORE

no

calibration

available

# After 8/30/90, maintained by U.S. Geological Survey

## Before 8/30/90, maintained by University of Alaska

39
Counts per cm

ui o> 0

Ul o

Ul

-I

rt>

O 

Ul

Ul
Counts per cm

*. en O) oa 

cn

o>

cr 

o>

O 

In

tv)
10

Counts per cm

en at oo

i 

_t

in

n

J 

I

p

in

en
Counts per cm

en

6

In

.3

pIn
Counts per cm

O> ». Ol O> -J 00
6

cn

2,

1

O

cn

en

tvj

Counts per cm 

*. en o> 
DFR

10 -r

9 4-

8 +

§ 

8.

v> ~e

J

-2 -1.5 -1 -0.5 0 0.5

Frequency (Hz)

1 1.5

46
NOT

-2 -1.5 -1 -0.5 0 0.5

Frequency (Hz)

1 1.5

47
Counts per cm

to CA> Ul o> 00 

Ul

CD 

<D

(D

CT

0)

Ul

(O

<o o

o

Ul

p 

Ul

Ul
RDN

9 -r

-2 -1.5 -1 -0.5 0 0.5

Frequency (Hz)

1.5

After August 30,1990

49
REF

-2 -1.5 -1 -0.5 0 0.5

Frequency (Hz)

50

1 1.5
RSO

-2 -1.5 -0.5 0 0.5

Frequency (Hz)

1 1.5

51
RWS

-2 -1.5 -1 -0.5 0 0.5

Frequency (Hz)

52

1 1.5
ROW

-2 -1.5 -1 -0.5 0 0.5

Frequency (Hz)

1 1.5

53
RS2

-2 -1.5 -1 -0.5 0 0.5

Frequency (Hz)

54

1 1.5
RDTN

-2 -1.5 -1 -0.5 0 0.5

Frequency (Hz)

1 1.5

55
RDTE

9 -r

8 +

-2 -1.5 -1 -0.5 0 0.5

Frequency (Hz)

56

1 1.5
RED

100000000 -r

10000000 --

1000000

100000

E 

E

V.

0)

a

I

o 

0

10000

1000 --

100 --

10 --

Before August 30,1990

0.1 0.2 0.4 0.5 0.8 1.0 1.7 2.0 2.5 3.3 5.0 10 15 20 30 40 50

Frequency (Hz)

57