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BEEF: Buffalo Explosion Experiment for Fieldwork:Preliminary Report
UNC Volcanolgy
June 21, 2013
1 Introduction
1.1 Motivation
Volcano seismology is primarily an observational and computational discipline, with very fewopportunities for experimental verification of processes observed in the field or modelled inthe lab. However, the Buffalo Man Made Maars project provided a valuable means to collectdata and demonstrate new methods of analysis during a controlled experiment designed tomimic volcanic explosions. This initiative came to our attention when results from the firstMan Made Maars experiment were presented in Taddeucci et al. [2013]. We recognizedkey opportunities to measure the vertical propagation of infrasound, the effect of cratermorphology on infrasound radiation patterns and seismo-acoustic energy partitioning. Theexperiment also provided means to test the integrated wireless seismic tomography networkunder development by the VolcanoSRI group. We developed a proposal and submitted itto the principal investigators of the Man Made Maars experiment; this proposal is includedas Appendix 10.1. All the data collection objectives outlined in the proposal were achievedduring the experiment.
1.2 Personnel
The Buffalo Man Made Maars experiment was an initiative by SUNY Buffalo. Principalorganizers from SUNY Buffalo included A. H. Graettinger, I. Sonder, and G. A. Valentine.Research teams from the United States, Germany, Italy, Canada, and New Zealand attendedthe experiment. There were a total of 18 primary researchers assisted by graduate studentsfrom SUNY Buffalo. The seismoacoustic group consisted of Ingo Sonder of SUNY Buffalo;Daniel Bowman, Keehoon Kim, and Jake Anderson of the University of North Carolina atChapel Hill (UNC); Jeff Johnson of Boise State University; Dan Hong and Lei Shi of GeorgiaState University; and Dennis Phillips of Michigan State University. Ingo Sonder deployed ageophone line in close proximity to the explosions. The UNC group deployed a ground-basednetwork of seismometers and infrasound microphones as well as a balloon-mounted infrasoundmicrophone array. Jeff Johnson deployed several additional infrasound microphones duringthe second day of the experiment as well as contributed valuable instrumentation to theUNC network. Dan Hong, Lei Shi, and Dennis Phillips tested VolcanoSRI instrumentation.
1
1.3 Field Setup
The UNC deployment consisted of a string of seismo-acoustic sensors deployed, primarily, ina linear array extending from the shot pads southwest. An experimental array of infrasoundsensors were deployed along a tethered cable hoisted above the explosion site by heliumballoons.
The surface stations consisted of a combination of short period and broad band seismicinstruments along with several infrasonic microphones (see Table 1). The purpose of theground array was to record the seismic waves at high fidelity and high sample rate (500samp/s). This diversity of instrumentation was due mainly to the availability of instru-mentation off the shelf. This mix further serves, however, as a reasonable way to test andcompare the various instruments employed in common volcanological settings.
There were 12 shots recorded on 4 distinct pad sites (Table 2). The positions for theshots were located with GPS, although the precise timing was estimated using the arrival ofthe seismic and acoustic waves. Details of the source parameters (yield, burial depth, load)and time lapse film of the explosion sources will be provided by the SUNY Buffalo team.
2 Instrumentation
Data for this experiment were recorded on three different acquisitions systems. The primarydata were recorded on Reftek 130 data logger’s and saved as standard REF files. The REFfiles were were converted to R-format files and SAC format for distribution.
A detailed report on the operation and performance of the RT-160, a new instrumentprovided by RefTek, is presented as an appendix to this document in Appendix 10.2.
The other system included new data loggers borrowed from Jeff Johnson. These werecommercial data loggers from Omnirecs called DataCube3 [Omnirecs, 2012]. They were setto record at a sample rate of 400 Hz and gain = 64.
Microphones were built by Jeff Johnson, Boise State, and documentation of the infrasonicresponse and other characteristics can be found in published literature [Marcillo et al., 2012].
2.1 Sensors
Sensors used by the UNC team are listed in Table Table 1), along with Lat-Lon locations.There were four different seismometers used in the experiment and the microphones hada slightly different implemnetations. Since the experiment involved a man-made syntheticsource of known characteristics, the team used this occasion to explore the diversity ofinstrumentation.
L28 Standard short period instrument.
CMG40T Midrange broadband instrument with corner frequency 30 s.
CMG3T Broadband seismometer, corner frequency 120 s.
HS1 Geophone on RT 160, corner frequency 2 Hz.
2
ACC Accelerometer on RT 160, corner frequency 2 Hz.
mic1 1 inch microphone
mic0.5 0.5 inch microphone
mic5 5 inch microphone
3 Initial Analysis
The weeks following the deployment involved formatting the data, establishing a namingconvention for the highly unconventional aerial deployment, and preparing the first figuresfor this report.
Bowman wrote a detailed report on the use of the RT160, a new seismic station providedby Refraction Technologies (Reftek). The UNC team discovered several problems with thesenew stations, which Bowman outlined in his report and transmitted to Ref Tek. The reportis included as Appendix 10.2.
Origin time of each explosion and velocity of P- and S-waves were inverted from traveltimes of P- and S-phase to the stations. Origin times were obtained with respect to sevenout of twelve explosions for which at least three seismic stations were in operation (Table2). Errors in picking arrival times are ∼50 ms, and associating error of the origin times are±4 ms at 95% confidence level. Slope of trave time curve provides estimates of seismic wavevelocity in local medium (Figure 1). Average P- and S-wave velocities are 1589 m/s (±32m/s) and 390 m/s (±13 m/s). The remainder of the shot timings were determined using theaverage velocities and a nearby station.
4 Seismic Data Sharing and Download
All shot data recorded in Buffalo from UNC investigators can be accessed by downloading atar file from Lees’ web site:
http://www.unc.edu/~leesj/FETCH/GRAB/TEMP/SACit_2013.06.21_14_00.tar.gz
The seismic data is stored in 12 shot directories in SAC format.
5 Anticipated Research Projects
5.1 Moment tensor inversion: Keehoon Kim
Kim will determine the moment tensor for the explosions. Seismic moment tensors are math-ematical representations of seismic sources. Seismic signals excited by buried explosions canbe inverted for the moment tensor, providing unique constraints on source region’s physicalproperties including magnitude of explosion, geometry of explosion cavity (or deformation),and temporal evolution of material flow [Chouet, 1996]. The buried explosion may causesigificant deformation of the source region. In addition, the creation of the crater and thevertical plume accompany significant mass transport from the source region to the surface.
3
Thus, seismic moment tensor analysis may shed light on these source processes related tocrater formation.
5.2 Vertical array, anelastic attenuation: Daniel Bowman
Bowman will investigate the disposition of the vertical array, which was in constant motiondue to wind. This resulted in stations that change position over time, a unique problemthat is almost never encountered in seismoacoustic studies. The instrument locations will beestimated using image analysis of video that Bowman recorded during each shot. Followingthe location, we will be investigating the acoustic wave propagation and the approximationsof monopole, dipole and quadropole radiation from the explosion source. Such radiationpatterns provide critical constraints on the source model for infrasound waves originating atthe vent of a volcano [Kim et al., 2012b]. In contrast to previous studies, however, we willinvestigate the radiation patterns both upon and above the surface of the Earth. Resultsfrom this study will shed light on the efficacy of using vertical arrays to constrain infrasoundon volcanoes. If the vertical array deployed at the MMM experiment observes phenomenathat ground instruments did not record, a vertical array capable of recording signals atvolcanoes will be developed.
A comparison of seven different methods of estimating the analestic attenuation (Q) ofseismic waves was made in the late 1980s [Tonn, 1989]. Results of synthetic tests performedin this study indicate that the analytic signal method [Engelhard, 1996] is the most accurateway to constrain Q. However, this method becomes unstable in the presence of noise; this mayaccount for its lack of representation in the scientific literature of the last 15 years. Recentdevelopments in signal processing, specifically the empirical mode decomposition [Huanget al., 1998], ensemble empirical mode decomposition [Wu and Huang, 2009] and statisticalempirical mode decomposition [Kim et al., 2012a] methods are promising means to removenoise from seismic data. Results from the MMM experiment will be used to test a newanalytical signal method of determining Q using the signal processing algorithms describedabove. If this method performs well, it will be applied to an active source tomography datasetrecorded at Montserrat. Bowman anticipates that this project will comprise his dissertationresearch.
5.3 Shock waves: Jake Anderson
Anderson will explore the evolution and dissipation of shock waves generated near the sourceof the explosion. Shock waves have properties that differ significantly from normal acousticwaves that may alter waves close to the source. A clear understanding of shock waves involcanic settings is critical for understanding propagation effects on amplitude and arrivaltime for monitoring and source inversion. Anderson will also study energy partitioningbetween the earth and atmosphere and how it differs among explosions, and how it mayrelate to properties of explosion sites.
4
5.4 Dispersion: Jonathan Lees
Lees will work on particle motion analysis and dispersion of the surface waves as the wavetrain travels along the linear array. This will provide constraints on the velocity models usedin moment tensor inversion. Lees is exploring the use of the wavelet transform (see Figures3 and 2) and the Hilbert-Huang Transform [Huang et al., 1998] (see Figures 4 and 5) inextracting dispersion curves.
5.5 Instrumentation for VolcanoSRI
As part of a test for equipment developed by NSF project VolcanoSRI, researchers fromMichigan State University and Georgia State University, Atlanta, installed several stationsto test recording and communication.
6 Acknowledgments
Researchers from UNC were supported by NSF grants OIA-1125185 and EAR-0838395 aswell as the NSF Graduate Research Fellowship Program under Grant DGE-1144081. TheMartin Research Fund at UNC supported the development and deployment of the verticalarray.
These experiments were funded primarily by the University at Buffalo through the UBCenter for Geohazards Studies, with additional contributions from team member sponsors.We thank the following for their key assistance in preparing for and executing the experi-ments: D. Goralski, J.L. Ball, K. Bennet, D. Doronzo A.G. Harp, C.G. Hughes, P. Johnson,S. Pansino, D. Ruth, D. Schonwalder, M. Sweeney, and P. More.
7 Tables
5
Figure 1: Trave time curves of P- and S-waves from the explosion site to the stations.
6
Figure 2: Velocity versus Frequency for Shot 6, station S03T40V measured on the wavelettransform, 3
7
Figure 3: Wavelet Transform of the surface wave at station S03T40V vertical component,Shot number 6.
8
Figure 4: Empirical Mode Decomposition of Shot 6 recorded on S03T40V - vertical compo-nent. Note surface wave dispersion.
9
Figure 5: Hilbert-Huang transform of the surface wave at station S03T40V vertical compo-nent, Shot number 6.
10
Station Sensor Serial Logger Channel lat lon elev1 S01L28V L28 9999 A3H VNE 42.50 -78.62 4072 S02T40V 40T T41033 9026 VNE 42.50 -78.62 4033 S03T40V 40T T41034 9025 VNE 42.50 -78.62 4064 S04T03V 3T T3A28 9024 VNE 42.50 -78.62 4065 S06RTSV HS1 9999 C04A VNE 42.50 -78.62 4016 S06RTSA ACC 9999 C04A VNE 42.50 -78.62 4017 S07RTSV HS1 9999 C04C VNE 42.50 -78.61 4008 S07RTSA ACC 9999 C04C VNE 42.50 -78.61 4009 S02M05I mic0.5 9999 9026 I 42.50 -78.62 406
10 S02M05J mic0.5 9999 9026 J 42.50 -78.62 40511 S03M10I mic1 01C021 9025 I 42.50 -78.62 40512 S03M05J mic0.5 0.5G012 9025 J 42.50 -78.62 40513 S04M10I mic1 01D048 9024 I 42.50 -78.62 40514 S04M10J mic1 01D007 9024 J 42.50 -78.62 40515 S04M10K mic1 01D024 9024 K 42.50 -78.62 40416 S05M50I mic5 5.0F001 A3F I 42.50 -78.62 40417 S05M10J mic1 01D040 A3F J 42.50 -78.62 40418 S05M05K mic1 9999 A3F K 42.50 -78.62 40119 S08M05I mic0.5 9999 A3G I 42.50 -78.62 40520 S08M10J mic1 9999 A3G J 42.50 -78.62 40521 S09M50I mic5 9999 A3E I 42.50 -78.61 40422 S09M10J mic1 9999 A3E J 42.50 -78.61 40523 S09M10K mic1 9999 A3E K 42.50 -78.61 40524 B01M10I mic1 01D048 9024 I -99925 B01M10J mic1 01D007 9024 J -99926 B08M10I mic1 01D048 9024 I -99927 B08M10J mic1 01D007 9024 J -99928 B09M10I mic1 01D048 9024 I -99929 B09M10J mic1 01D007 9024 J -99930 B10M10I mic1 01D048 9024 I -99931 B10M10J mic1 01D007 9024 J -99932 B11M10I mic1 01D048 9024 I -99933 B11M10J mic1 01D007 9024 J -99934 B12M10I mic1 01D048 9024 I -99935 B12M10J mic1 01D007 9024 J -999
Table 1: Buffalo 2013 station file. Stations that include the letter B were deployed on theballoon tether.
11
num
ber
char
ge.w
tpad
lat
lon
zyr
jdm
odom
hr
mi
sec
11.
000
142
.501
1286
-78.
6149
676
0.40
520
1312
75
713
101.
4084
062
0.66
72
42.5
0114
19-7
8.61
4921
50.
405
2013
127
57
1422
50.9
3875
83
0.33
32
42.5
0114
19-7
8.61
4921
50.
405
2013
127
57
1538
17.5
0465
24
0.33
33
42.5
0115
48-7
8.61
4876
90.
405
2013
127
57
1717
4.27
1540
50.
333
342
.501
1548
-78.
6148
769
0.40
520
1312
75
718
216.
0117
276
0.33
33
42.5
0115
48-7
8.61
4876
90.
405
2013
127
57
1922
17.3
9063
57
0.33
34
42.5
0117
42-7
8.61
4809
30.
405
2013
128
58
1259
54.7
2559
68
0.33
34
42.5
0117
42-7
8.61
4809
30.
405
2013
128
58
1419
38.2
2349
89
0.33
34
42.5
0117
42-7
8.61
4809
30.
405
2013
128
58
157
14.3
8523
310
0.33
35
42.5
0118
89-7
8.61
4758
40.
405
2013
128
58
167
54.8
0044
111
0.33
35
42.5
0118
89-7
8.61
4758
40.
405
2013
128
58
1646
25.3
1569
612
0.33
35
42.5
0118
89-7
8.61
4758
40.
405
2013
128
58
1723
14.6
3595
1
Tab
le2:
Buff
alo
2013
Shot
Info
rmat
ion.
Tim
esar
ees
tim
ated
from
the
seis
mic
arri
vals
.
12
8 Figures
Figure 6: Buffalo Deployment Map May, 2013.
13
Figure 7: Buffalo Deployment Map May, 2013.
14
9 Shot Gathers
References
B. Chouet. New methods and future trends in seismological volcano monitoring. Monitoringand mitigation of volcano hazards, pages 23–97, 1996.
L. Engelhard. Determination of seismic-wave attenuation by complex trace analysis. Geo-physical Journal International, Geophysical Journal International:608–622, 1996.
Norden E. Huang, Zhang Shen, Steven R. Long, Manli C. Wu, Hsing H. Shih, Quanan Zhen,Nai-Chyuan Yen, Chi Chao Tung, and Henry H. Liu. The empirical mode decompositionand the Hilbert spectrum for nonlinear and non-stationary time series analysis. Proceedingsof the Royal Society of London A, 454:903–995, 1998.
D. Kim, Kyungmee Kim, and Hee-Seok Oh. Extending the scope of empirical mode de-composition by smoothing. EURASIP Journal on Advances in Signal Processing, 2012(1):168, 2012a. doi: 10.1186/1687-6180-2012-168. URL http://asp.eurasipjournals.com/
content/2012/1/168.
K. Kim, J. M. Lees, and M. Ruiz. Acoustic multiple source model for volcanic explosionsand inversion for source parameters. Geophysical Journal International, 191:1192–1204,2012b. doi: 10.1111/j.1365-246X.2012.05696.x.
Omar Marcillo, Jeffrey B. Johnson, and Darren Hart. Implementation, characterization,and evaluation of an inexpensive low-power low-noise infrasound sensor based on a mi-cromachined differential pressure transducer and a mechanical filter. J. Atmos. OceanicTechnol., 29:1275–1284, 2012. doi: 10.1175/JTECH-D-11-00101.1.
Omnirecs, 2012. URL http://www.omnirecs.de/.
J. Taddeucci, G. A. Valentine, I. Sonder, J. D. L. White, P.-S. Ross, and P. Scarlato. Theeffect of pre-existing craters on the initial development of explosive volcanic eruptions: Anexperimental investigation. Geophys. Res. Lett., 40:507–510, 2013. doi: 10.1002/grl.50176.
Rainer Tonn. Comparison of seven methods for the computation of Q. Physics of the Earthand Planetary Interiors, 55:259–268, 1989.
Z. Wu and N. E. Huang. Ensemble empirical mode decomposition: A noise-assisted dataanalysis method. Advances in Adaptive Data Analysis, 1:1–41, 2009.
15
Figure 8: Buffalo Shot1
16
Figure 9: Buffalo Shot2
17
Figure 10: Buffalo Shot3
18
Figure 11: Buffalo Shot4
19
Figure 12: Buffalo Shot5
20
Figure 13: Buffalo Shot6
21
Figure 14: Buffalo Shot7
22
Figure 15: Buffalo Shot8
23
Figure 16: Buffalo Shot9
24
Figure 17: Buffalo Shot10
25
Figure 18: Buffalo Shot11
26
Figure 19: Buffalo Shot12
27
10 Appendices
10.1 Proposal to Partipate in MMM
28
Proposed Field Work for Blast Experiments
Danny Bowman, Jonathan Lees, Keehoon Kim (UNC),Jeffrey Johnson (Boise State),
VolcanoSRI Group (UNC/Michigan State/Georgia State)
June 21, 2013
1 Objectives
1. Measure vertical propagation of infrasound
2. Determine effect of crater morphology on infrasound radiation patterns
3. Quantify partitioning between infrasonic and seismic energy from explo-sions of known energy and depth
4. Measure the transition from shock waves to sonic energy
5. Test our integrated wireless geophone network to determine how effectivelywe can locate the seismic source
2 Proposed Work
These are outlines of possible projects we could do. They are not mutuallyexclusive - we would like to try all three. The second and third in particularwould greatly advance our objectives of developing a wireless seismic networkand determining the source mechanisms of infrasound at volcanoes.
2.1 Scenario One
Deploy one to several strings of microphones approximately 10 m away fromthe explosion sites and extending across the field to the south. The strings ofmicrophones will be approximately one hundred meters long. The microphonesare approximately 6 inches across, and the microphones will be hooked to a datalogger the size of a small briefcase. We anticipate setting up the instrumentsin the morning and letting them run all day without interference. We wouldlikely download the data each afternoon once the blasting is finished. We mayalso install up to five seismic stations in the munitions field and possibly in theforest surrounding the site. These stations would consist of a car battery, alogger about a foot across, and a seismometer approximately 6 inches across.
1
Like the microphones, these would run all day without interference. This wouldaddress Objectives 2, 3, and 4.
2.2 Scenario Two
In addition to the above deployments, we would place several wireless geophonestations around the explosion site. Since these are seismic stations, they couldbe located several hundred meters from the pads. Therefore, they should keepout of the way of other experiments in the blast area. Like the Scenario Onenetworks, these systems should run without interference. This scenario wouldaddress Objective 5.
2.3 Scenario Three
Along with Scenarios One and/or Two, we would develop and deploy a systemto lift a vertical string of microphones above (or above and to the side of) theexplosion sites. We understand that the instruments should be approximately30 m above the explosion to stay clear of debris. We are considering variousdesigns including a balloon tethered in a tripod like fashion. We could also fly acamera if this would be useful to other investigators. The balloon system wouldbe tested at UNC prior to deployment in Buffalo, and the instruments shouldfly without interference as long as weather remains favorable. This scenariowould address Objectives 1-4, with particular emphasis on 1. It would provide aquantitative test to determine if these explosions represent a monopole (Figure1) or dipole (Figure 2) source. Having a microphone above the explosion iscritical, as the dipole source produces a strong overpressure above the explosionbut very little overpressure to the sides.
2
Figure 1: Infrasound radiation pattern of monopole source.
3
Figure 2: Infrasound radiation pattern of dipole source.
4
10.2 Field Report for RT-160 Seismometer
33
Field Report for RT-160 Seismometer
Daniel C. Bowman, Jacob F. Anderson, and Keehoon Kim
June 21, 2013
1 Introduction
Refraction Technologies, Incorporated (Ref Tek) provided us with two RT-160 seismometers for field testingand evaluation during a simulated volcanic explosion experiment. Our field team (Daniel C. Bowman, JacobF. Anderson, and Keehoon Kim, all from the University of North Carolina at Chapel Hill) received theseinstruments, learned how to use them via a draft operations manual, deployed them in the field, recordedseismic data from 12 explosions, decommissioned the seismometers, recovered seismic data, and shippedthe instruments back to Ref Tek. We then deconvolved the seismic data and performed simple analysis todetermine the quality and usability of the results. This document describes our activities and assessment ofthe RT-160 seismometer.
2 Pre-deployment Setup
Ref Tek shipped two RT-160 seismometers and associated equipment to Buffalo, New York via UPS Ground.The shipment included the following:
• Seismometers: Serial No. C04A and C04C
• Two battery chargers
• An iPod touch with real time monitoring software installed
• An iPod charger
• A WiFi hot spot device
• Two bubble level attachments
We received this equipment on the evening of May 6, 2013. The battery packs were inside the seis-mometers. The batteries were disconnected so that the instruments would not turn on during transit. Allequipment appeared to be in good condition when we received them.
As the explosion experiment was starting on May 7, we had only a short time to learn how to use theseismometers. We set up the two units in our hotel room and after some initial trial and error, managedto turn them on and connect them to the iPod via the WiFi hot spot (Figure 1). The LED lights on theseismometer were a bit confusing at first as we were not used to this type of display, however after referringto the documentation we were able to use the status lights to determine the state of the instruments. It tookus about an hour and a half after unpacking the seismometers to feel confident that we could successfullydeploy them in the field.
We used the real time display on the iPod to make sure that all three axes were preforming correctly. Wenoticed that the real time display would stop showing data after an apparently random time interval (froma few seconds to after about 30 seconds). We suspect that this is a bug in the display app. However, thewireless connection performed well even though other wireless networks were present at the hotel.
1
3 Experiment, Network Deployment, and Data Processing
The experiment consisted of 12 explosions over two days. The size of the charges ranged from 1 lb to 1/3lb and the burial depth ranged from 0.5 to 1 meter below the ground surface. Explosions occurred on fiveadjacent pads (Figure 2).
The C04A seismometer was located approximately 30 to 46 m from the explosions as part of a lineararray that included 4 seismometers from UNC. The C04C seismometer was placed approximately 34 to 36 mfrom the explosions and was orthogonal to the linear array (Figure 2). We dug holes approximately 1 meterdeep at each location, placed the seismometers inside (Figure 3), and covered them with 5 gallon buckets(Figure 4). We did not backfill with soil both because we wanted to be able to easily recover the data andalso because we were concerned about GPS problems. We used a compass to orient the axes. Initially, wedid not realize that bubble levels had been included in the equipment shipment, so we used an iPhone app tolevel each seismometer. We did not verify that the LEDs indicated the correct level as we did not understandhow to do that until the end of the experiment. We brought each seismometer back to the hotel after eachday for safekeeping. We were able to use the sensitivity, damping constant, and natural frequency given inthe data sheet of the built-in geophone to deconvolve the instrument response. However, this process wouldbe easier if all necessary information for conversion to physical units–the counts-volts constant, sensitivity,normalization constant, poles, and zeros–were provided in one place in the instructions.
4 Results
The two velocimeters operated without any trouble throughout the duration of the experiment, and wesuccessfully recovered data from all 12 explosions (Figure 5). We did not examine accelerometer datain detail, but no problems were apparent in a brief overview. In contrast, difficulties with providing theappropriate power supply caused us to lose some data at our other stations.
The internal GPS had serious issues with acquiring a fix and providing an accurate station location.While some locations were within 10 m of the true station location, others ranged from hundreds of metersto hundreds of kilometers. The GPS problems could be due to the seismometers being in holes. However,we felt that the holes were necessary to prevent other site personnel from disturbing the instruments and toreduce noise levels.
There is also a severe timing error during the second day of the experiment. Based on visual inspectionof the seismograms, we find that the C04C instrument shows arrivals about 0.4 seconds earlier than expected(Figure 6). The other instrument (C04A) appears to have the correct timing. We suspect that this may bea GPS problem also.
5 Evaluation
We found that the Ref Tek 16 seismometers are rugged and very easy to deploy quickly. We appreciated thesimplicity of the deployment process and we expect that these seismometers could be set up by relativelyinexperienced field staff without too many problems. We collected valuable data from this deployment andthe instruments contributed significantly to the success of our expedition. However, the corner frequencyis too high for our work with volcanoes - we need something more broadband. The complete lack of userconfiguration makes it impossible to adapt these instruments to situations that require different data loggingparameters. More generally, the GPS and timing problems are very frustrating. Perhaps the instrumentscould include a GPS antenna that could be extended above ground if the sensor package needed to be buried?While the internal battery pack was easy to charge and replace, it cannot be shipped via air or carried aboardan airplane. This will be a drawback for investigators who need to move the seismometers quickly.
Once the GPS problems are addressed, we would recommend these instruments to investigators concernedmore with rapid response to local events rather than high precision data or distant deployments. We thinkthat the Ref Tek 160 also might be a good seismometer for educational purposes - students could practicedeployment and data retrieval on this user-friendly system.
5.1 Pros
• The seismometers are rugged and easy to deploy.
• The integrated sensor/logger package made it very convenient to transport and set up the instrumentwithout having to connect lots of cables.
• The preset sample rate and gain made it very simple to use the seismometer.
• Data retrieval was easy and intuitive.
5.2 Cons
• There is a bug in the real time monitoring software that causes the display to stop acquiring after anapparently random period of time.
• It is easy to accidentally turn on the magnetic switch when the seismometers are being transported.
• The very poor GPS accuracy made it necessary to survey the instrument locations, instead of beingable to rely on the internal GPS to give a good location.
• The severe timing error on one of the instruments on the second day was distressing and we areconcerned that there may be more subtle timing errors elsewhere.
• The fixed sample rate and other parameters limit the versatility of the instruments. For example, thehigh frequency portion of the P arrival on Station S04T03V is not present on the RT 160 stationsbecause of their lower sample rate (Figure 6).
• The size of the battery pack makes it illegal to take on a plane or ship via air. This will be a significantimpediment for overseas deployments or rapid response far from the instrument storage area.
6 Figures
Figure 1: Learning how to use RT-160 seismometers prior to field deployment.
Figure 2: RT-160 locations relative to explosion pads.
Figure 3: RT-160 placed inside hole before being covered with a bucket.
Figure 4: View of installed station.
Figure 5: Seismogram of Explosion 1, displaying traces from Station S06RTSV (Serial C04A) and StationS07RTSV (Serial C04C).
Figure 6: Seismogram of Explosion 12 (day 2), displaying traces from Station S06RTSV (Serial C04A),Station S07RTSV (Serial C04C). Station S04T03V was located about 20 meters further from the explosionthan Station S06RTSV. Note that S07RTSV is about 0.4 seconds earlier than S06RTSV.
10.3 Instrument Responses
41
Table 3: 3T5 POLES
real imaginary1 -0.0364424747816416 0.03644247478164162 -0.0364424747816416 -0.03644247478164163 -1130.97335529233 04 -1005.30964914873 05 -502.654824574367 02 ZEROES1 0 02 0 0
Normalization 571507691.771286Sensitivity 1500
Table 4: 40T3 POLES
real imaginary1 -0.148031845837151 0.1480318458371512 -0.148031845837151 -0.1480318458371513 -314.159265358979 03 ZEROES1 0 02 0 03 999.026463841554 0
Normalization -0.314Sensitivity 800
Table 5: L282 POLES
real imaginary1 -19.99 19.992 -19.99 -19.992 ZEROES1 0 02 0 0
Normalization 1Sensitivity 30.4
42
Table 6: RT160V1 POLES
real imaginary1 -6.28318 01 ZEROES1 6.28318 0
Normalization 1Sensitivity 2113819608
Table 7: RT160A1 POLES
real imaginary1 -6.28318 02 ZEROES1 6.28318 02 0 0
Normalization 1Sensitivity 135915.102040816
43
