BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS

Transcription

1 190s )l'8 /j COliB?ACTUS (LENDili-rG S':::CriON) PUrrt".cA"-: D~ ::; BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS RECORD RECORD 1985/18 MACQUARIE ISLAND GEOPHYSICAL OBSERVATORY ANNUAL REPORT 1982 by I.J. FERGUSON The information contained in this report has been obtained by the Bureau of Mineral Resources. Geology and Geophysics as part of the policy of the Australian Governmept to assist in the exploration and development of mineral resources. It may not be published in any form or used in a company prospectus or statement without the permission in writing of the Director.

2 RECORD 1985/18 MACQUARIE ISLAND GEOPHYSICAL OBSERVATORY ANNUAL REPORT 1982 by I.J. FERGUSON

3 CONTENTS SUMMARY 1. INTRODUCTION 2. GEOMAGNETIC OBSERVATORY La Cour magnetograph Baseline values Scale values Orientation tests Parallax tests Magnetometers Intercomparisons Preliminary data 3. SEISMOLOGICAL OBSERVATORY Seismograph Seismograph calibrations Routine seismograph checks Seismic Data 4. CONTROL EQUIPMENT Timing Power Cables and wiring 5. BUILDING MAINTENANCE Geophysics office 6. OTHER DUTIES 7. ACKNOWLEDGEMENTS 8. REFERENCES APPENDICES 1. Geophysical observatory history Geomagnetic absolute instruments Repairs and alterations to instruments TABLES 1. Station data for Macquarie Island, Observed mean baseline values, Magnetograph parameters, Orientation tests for La Cour variometer magnets, 04 October Orientation comparison, Parallax text, 03 August Preliminary instrument corrections, Macquarie Island, Preliminary monthly mean geomagnetic values and K-indices, Geomagnetic annual mean values, Reference mark azimuth, Magnetometer comparisons, Seismograph parameters, Local earthquakes felt on Macquarie Island, FIGURES 1. Macquarie Island, SP-Z, Calibration curves, Electronic filter installed in seismograph, August A. Response of AR311-recorder pen to input voltage, Correc~ions to measured seismograph deflections, Page

4 SUMMARY.. Recording of the geomagnetic field and seismic activity continued at the Macquarie Island Geophysical Observatory during Preliminary seismological and geomagnetic data were forwarded on a regular basis to Australia.

5 1. INTRODUCTION The geophysical observatory on Macquarie Island has recorded the geomagnetic field and seismic activity since The observatory forms part of the Australian National Antarctic Research Expeditions (ANARE) station on the island. It is operated by a geophysicist from the Bureau of Mineral Resources, Geology and Geophysics, Canberra with logistic support from the Antaractic Division, Department of Science and Technology. An outline of the history of the observatory is given in Appendix 1, and the co-ordinates of the seismic and magnetic stations are given in Table 1. During 1982 geomagnetic field variations were recorded using a La Cour NORMAL run magnetograph. Absolute magnetic observations were made seven times each month. Throughout 1982 the seismograph comprised a short-period vertical Willmore mark II seismometer and a visual drum recorder. The author was geophysicist on Macquarie Island for most of 1982, replacing Geoff Thomas on 28 January and handing over to Barry Page the stand-in observer for the summer period, on 31 October. 2. GEOMAGNETIC OBSERVATORY Magnetic recording continued throughout 1982 with a total of 7 days' record loss. This loss occurred during magnetograph adjustments, rewiring of control equipment and because of faulty record changes. La Cour magnetograph The La Cour magnetograph recorder (20 mm/hr) functioned satisfactorily throughout Record quality was occasionally reduced by extreme condensation on magnetometer lenses, fluctuating lamp intensity and spider webs on the variometer lamp. The magnetograph recorder motor was driven by synchronous 240V 50Hz AC supplied by an inverter. Time marks were supplied by a BMR TMU2 time mark unit, driven by either an EMI crystal controlled clock or a backup. The power and timing are discussed in more detail in Section 4 of this report. Baseline values The declination (0), horizontal intensity (H) and vertical intensity (Z) baseline values (BLV) were derived from regular absolute magnetic observations; and the temperature BLV from daily observation of the Z variometer thermometer (Table 2). Baseline value changes were caused by earthquakes, magnetograph readjustment, change of absolute instruments, drift and a thunderstorm. The cause of the 0 BLV change in late October is unknown. On 14 June adjustments made to the H ordinate, baseline and temperature traces, by rotation of the H magnetometer internal prisms, also caused a change in H scale value. 1

6 Scale values The D, Hand Z scale values were determined using Helmholtz coils and a BMR MC01 magnetic calibrator (Table 3). Scale value measurements were made up to seven times monthly. The MC01 calibrator WqS repaired in September when a fault developed in its internal constant current supply (Appendix 3). The temperature (T) scale value was derived from a least squares fit to an annual plot of observed variometer temperatures against corresponding T ordinates. Orientation tests The orientations of the Hand D variometer magnets were determined using Helmholtz coils and a variable current source. A deflecting magnet was used to determine the Z magnet orientation (Table 4). Final orientation tests were made i on 04 October. The ex-median angle determined for D differs significantly from that of 1981 (Table 5). This is most probably a result of variometer adjustments made in August 1981 (Williams, 1982). The H magnet ex-prime-vertical angle was changed by torsion head rotation on 11 February and 10 June to correct earthquake caused ordinate changes. At no time did the angle exceed 1.6 degrees. Parallax tests The results of the parallax test conducted on 03 August were adopted as the values for parallax corrections for 1982 (Table 6). Magnetometers Magnetometers used during 1982 were: H: QHM's 177 (standard), 178, 179 D: 01 Jan - 26 Jan Askania declinometer with circle Jan - 31 Dec Askania declinometer with circle Z: BMZ 236 F: PPM MNS 2/2 Observations of Hand D were taken on pier E. The reference mark used for D i was North Mark Inner (NMI). Surveyors from the Tasmanian Department of Lands determined the azimuth of the reference marks during January 1982 (Table 10). Declinometer 505 was replaced by declinometer 506 in January 1982 in an attempt to decrease the scatter of D baseline values (Williams, 1982). Baseline values however continued to be erratic, scattered by up to two minutes. The feet of circle 616 were tightened on 09 December in a further attempt to reduce this scatter. Total intensity (f) observations were taken with the PPM head on P ier 1tJ. Zp values were derived from these observations using the scaled H ordinate and the mean, corrected H BLV for that month. The F pier difference was taken as zero, as determined previously by Davies (1982). Absolute instruments used since 1950 are listed in Appendix 2. 2

7 Intercomparisons During the brief changeover period in late October the Macquarie Island magnetometers were compared with the BMR travelling standards H: QHM 177 compared with QHM 172, HTM 704 D: Ask , circle compared with Ask , circle F: PPM MNS 2/2 compared with PPM Elsec 595/144 Three sets of QHM and declinometer comparisons were completed and one set of PPM comparisons (Table 11). Instrument differences between QHM 178, QHM 179 and QHM 177 were derived from the year's observed H-baselines. Preliminary data Preliminary monthly mean geomagnetic values were determined from the ten magnetically quietest days each month. This information, along with the scaled H and D components of K-indices, the K-index and preliminary mean baseline values for the month were telexed to BMR, Canberra. Preliminary instrument corrections applied to the mean geomagnetic values for 1982 are given in Table 7. The preliminary monthly mean and annual mean values for 1982 are given in Table 8. Annual mean values for 1972 to 1982 are given in Table SEISMOLOGICAL OBSERVATORY Recording continued throughout 1982 with a total 7 days of record loss. This loss resulted mainly from extreme weather conditions and radio frequency interference from the base standby transmitter. Seismograph Seismic activity was detected using a Willmore MK II seismoter (free period 1.0s) situated in the seismic vault; the output was amplified by an AS320 amplifier then transmitted via underground shielded cable to the Geophysics Laboratory where it was recorded using an AR311 amplifier and a Geotech RIO recorder (modified by the BMR for visual recording). Time marks were supplied to the seismograms from a control unit driven by either the EMI clock or a backup. Each day radio time pips from VNG Australia were used to correct the clock to Universal Time and to record comparison time marks on the seismograms. The recorder was powered by synchronous 240V 50Hz AC from an inverter. Seismograph calibrations The seismograph was calibrated several times during 1982 using the harmonic drive method. For these calibrations the function generator was connected into the calibration circuit at the seismic vault. This was to avoid electrical induction between the calibration and seismic signal lines, which share a long shielded cable from the seismic vault to the Geophysics Laboratory. Between 01 January and 20 January the seismograph response was reduced because of incorrect connection of the input signal into the AR311 amplifier. After the connections were corrected the response remained constant from 21 3

8 January until 19 August. A calibration test was performed on 14 April; Figure 1 shows the calculated calibration curve. During this time the seismograph magnification at periods less than 1.0s was higher than desirable. This resulted in record loss during strong prevailing winds. On 23 August, following a short trial, a low-pass passive electronic filter was installed between the AS320 and AR311 ampl~fiers (Fig 2). A calibration test on 24 August indicated that the filter considerably improved the response (Fig 1). The seismograph response remained constant from 24 August until 31 December with no further loss of record due to wind. During the calibration tests it was noticed that the response of the AR311-recorder pen system was not linear for peak-to-peak deflections over 30 mm. The response varied with the magnitude of the input signal. An increasing voltage ramp input into the AR311, recorded on the seismogram as a flattened curve (Fig 3A). This and other tests provided factors to correct measured deflections to true linear values (Fig 3B). The non-linearity is thought to be due to overloading of the pen motor. Thel curvilinear nature of the pen's swing contributes only slightly to the non-linearity; for an 80 mm swing, the error in measuring the orthogonal deflection (instead of the curvilinear deflection) is less than 2 mm. The AR311 amplifier also contributes only slightly to the non-linearity. Measurement of the AR311 output during an increasing input voltage indicates that for pen - deflections up to 80 mm, the AR311 respo~se falls and the combined AR311-recording pen response falls by 35%. Routine seismograph checks Between 07 July and 11 July AR311 attenuation was increased from 24 db to ensure that any aftershocks of the 07 July earthquake were recorded. At all other times the attenuation remained at 24 db (Table 12). The system response was 'monitored daily using calibration pulses applied to ' each seismogram by a BMR electronic calibrating unit. Occasional seismometer free period checks were also made throughout the year. Seismic data Macquarie Island lies on an active plate margin. Numerous small local earthquakes are recorded each year and usually a number of small tremors (Table 13). Seismic data were telexed to Canberra everyone or two weeks, for distribution internationally. 4. CONTROL EQUIPMENT The timing and power controls for the seismograph and magnetograph are located in an instrument room off the main Geophysics Laboratory. Batteries and an inverter are located in a special battery room, which with a dark room is shared with the Upper Atmosphere Physics Group. 4

9 4t 4t 4t 4t 4t Timing The EMI clock functioned well from its installation on 26 January, when it replaced the previous EMI clock, until 25 August. With only occasional adjustment it operated with a drift of less than 30 ms/day. On 25 August the EMI failed due to a noisy oscillator. After nine days of running on standby Mercer chronometer timing, a time reader was set-up to display timing from the Systron-Donner clock in the Upper Atmosphere Physics Laboratory. A time decoder was constructed to supply appropriate seismogram time marks and a 50 Hz reference signal for the inverter. This timing proved extremely reliable with a rate of less than 10 ms day. During November and December 1982 a GED clock was installed to replace the EMI clock (Page, 1984). The Mercer chronometer ran satisfactorily as a backup for periods of 1-2 days. After extended periods of operation however, the daily rate increased upto 10 s/day. Power The primary power source for the seismograph and magnetograph was a Saunders 24V/240 V inverter running from two heavy duty batteries. These batteries were trickle charged from station mains. The internal synchronising frequency of the inverter tended to drift, and when it was not synchronized externally (eg when the EMI failed) the output voltage increased above 240 V. The secondary power source, a Stabilac voltage stabilizer running on station mains, required occasional minor adjustments to keep voltage output at around 235V AC. Cables and wiring During 1982 unsuccessful attempts were made to locate and remove the short circuit in the pyrotenax cable from the Geophysics Laboratory to the variometer hut. In September a small panel was built to improve power/timing/scale value connections on the rear of the control rack. Signal lines, 240 V AC lines and 12V DC lines were separated and provided with appropriate plugs and sockets. On 13 September in gusty winds two air-dropped packages, after bouncing some distance across the isthmus, hit the variometer hut. One external support beam and some outer roof cladding were broken. Although the hut remained lightproof its temperature stability decreased and moisture content increased. Because of a lack of non-magnetic cladding on the base, repairs had not been effected by the end of BUILDING MAINTENANCE The door of the absolute hut was repaired on 29 October after it had sheared off at the hinges. It was noted then that the door frame was soft and rotted. The above problems illustrate the general state of the magnetic huts. Panels and underlying supports are rotting away due to absorbed moisture. No dramatic failures will occur, however, unless the buildings are subjected to a significant structural stress, for example during gale force winds. The

10 carpenter inspected the magnetic huts and recommended their replacement in the near future. Geophysics office The problem of the leaking window in the Geophysics office (Williams, 1982), was traced by the carpenter to the glass being of incorrect size for its frame. The leakage was substantially stopped in 1982 and it is expected to be completely sealed during OTHER DUTIES The normal additional domestic type duties were performed during These comprised rostered slushie duty in the mess, dong as and science block areas, garbage runs and occasional cooking. Occasional help was given to the Upper Atmosphere Physics Group. Assistance was also given in the cleaning and painting of Lusitania Bay Hut and in the restoration of Otto Bauer's grave at Nuggets. 7. ACKNOWLEDGEMENTS The author thanks all members of the Macquarie Island party for their assistance and companionship during Special thanks are due to Alan Nutley for numerous electrical repairs, construction of the time decoder and for changing records when the author was away from base. 8. REFERENCES DAVIES, P.M., Macquarie Island Geophysical Observatory, Annual Report Bureau of Mineral Resources, Austra7ia Record, 1983/2. WILLIAMS, W.H., Macquarie Island Geophysical Observatory, Annual Report Bureau of Mineral Resources, Austra7ia, Record, 1982/27 PAGE, B.J.; Macquarie Island Geophysical Observatory, November January Bureau of Minera7 Resources, Austra7ia Record, 1984/37 6

11 Bu il di ngs Seismological Observatory December 1956 February 1961 January 1962 November 1967 December 1969 December January October 1981 December APPENDIX 1 GEOPHYSICAL OBSERVATORY HISTORY MACQUARIE ISLAND - Start of ANARE station on Macquarie Island. - Seismograph Hut constructed - included geophysics office. - Magnetic Variometer Hut erected - Magnetic Abslute Hut erected - Geophysics Office constructed - Science Building constructed - included geophysics office, upper atmospheric physics laboratory and office for the Officer-in-Charge. - Two-component, short-period, Wood-Anderson seismograph (east-west and north-south) installed. - Replacement two-compoent, short-period Wood-Anderson seismograph installed. - Short-period Grenet vertical seismograph installed in addition to Wood-Anderson seismograph - Benioff three-component short-period seismograph installed to replace existing Grenet and Wood-Anderson Seismographs - Benioff vertical seismograph retained; the two horizontal component seismographs returned to Australia. - Willmore Mk I vertical seismometer used to test sites near seismic hut for seismic noise, the Willmore then replaced the Benioff, which was returned to Australia - Willmore MK I seismometer was replaced by Willmore MK II vertical seismometer. The Mk I seismometer was retained to enable sites on the plateau to be tested for microseismic noise. - Two Willmore MK II seismometers used concurrently during part of the year; one situated on the plateau and one in the seismic hut. - Willmore MK II in seismic but was returned to Australia and replaced by a Willmore Mk I. Willmore MK II remained in use on plateau. - Plateau system fatled early Willmore Mk I continued to operate in seismic hut. Willmore Mk II used to test sites on Wireless Hill for seismic noise. - Willmore Mk II used in seismic hut in vertical position as previously. Willmore Mk I used to set up horizontal north-south) seismograph in seismic hut. - Early in year, horizontal component recording was discontinued. - Willmore Mk I returned to Australia, leaving Willmore Mk II vertical seismograph in seismic hut. - Seismic recording system changed from photographic to vi sual. 7

12 APPENDIX 1 (Contd) Magnetic Observatory 1950 August December - Watts horzontal intensity variometer No was installed. Scale value was 3.5 nt/mm. - Watts H-variometer returned to Australia. 3-component normal La Cour magnetograph installed.. Scale values: H, 12nT/mm; 0, 0.09'/mm; Z, 13 nt/mm. - 3-component insensitive La Cour magnetograph installed to supplement the existing sensitive magnetograph. Scale values: H, 63 nt/mm; 0, 2.25'/mm, Z, 59 nt/mm. - Normal La Cour magnetograph was replaced by La Cour rapid run magnetograph (180 mm/hr). The insensitive La Cour magnetograph was modified to increase the insensitivity of the Hand Z variometers by changing the H-fibre and replacing the Z-magnet. Scale values are shown below. H(nT/mm) D'/mm Z(nT/mm) Before Norma After Rapid-run Before Insens it i ve After Norma February 26 - The 0 fibre was/replaced in an attempt to reduce erratic drift. 9 March 1968, H fibre was replaced - scatter and and drift continued. The H scale value was reduced to 23.7/nT/mm February 01 - H variometer fibre was replaced in the normal magnetograph. This reduced the H scale value to 19.3 nt/mm, and eliminated steep drift Recording ceased on the rapid run magnetograph February - Rapid Run magnetometers returned to Australia. 8

13 APPENDIX 2 GEOMAGNETIC ABSOLUTE INSTRUMENTS MAGNETIC OBSERVATORY ABSOLUTE INSTRUMENTS D H F Z Instrument/Circle QHM PPM BMZ DCK 158 DCK QHMs 177,178, QHMs 177, QHMs 177, OHMs 178, QHMs 177, DCK , DCK , DCK , DCK , (instrument numbers not specifi ed) 1961 DCK , DCK , DCK , DCK , / , / , / ,179 64, / ,178, / / ,178, , / ,177, , / ,177, /339, / ,177,178, / / ,178, / / ,178, / / ,177, / / ,178, , / ,178, / / ,178, , / , 178, / ,221a / ,178, , / ,178,179 MNS2/ / ,178,179 MNS2/

14 APPENDIX 2 (Contd) MAGNETIC OBSERVATORY INTERCOMPARISON INSTRUMENTS Date Declination Askania/circle Horizontal Intensity Vertical Intensity PPM BMZ Notes / / (instruments (instruments / / / / / / QHM 179 QHM 178 QHM 177, 288 QHM 179, HTM not specified) QHM 178, HTM 154 QHM 174, 179 not specifi ed) QHM 178 QH~l 177 QHM 177 QHM 178, HTM 154 QHM 177, HTM 154 HTM 154 OHM 172, HTM 154 QHM 178, HTM 704 QHM 173, 179 OHM 174, HTM 704 QHM 172, HTM 704 OHM 172, HTM 704 OHM 172, HTM 704 OHM 172, HTM 704 OHM 172, HTM 704 OHM 172, HTM 704 OHM 172, HTM 704 OHM 172, HTM 704 OHM 172, HTM A 221A MNZ-1/1 211 MNZ-1/1 221 MNZ-1/1 221 E1 sec Elsec 592/ / / / / /424, 429 Geom. 16/ /271, Geom. 816/1023 Geom. 816/1023 MNS2/2 595/ / OHMs were used to measure declination between 1951 and To improve the accuracy of D observations, the Kew Magnetometer 159 was re-introduced in Between 1951 and 1968, OHMs 177, 178, 179 were used, two at Macquarie Island while the other one was being re-standardised in Australia. In 1968, OHM 172 was added to this list. From 1976 OHMs 177,178, 179 were left permanently at Macquarie Island and standardised during intercomparison observations once a year. 3. From 1968 an Elsec PPM was use~ for F absolutes. Z baselines derived from the F absolutes and the previous month's H baseline. 10

15 APPENDIX 3 REPAIRS AND ALTERATIONS TO INSTRUMENTS Magnetic Calibrator: MCGl The magnetic calibrator was repaired on 25 September by A.Nutley, the ANARE electrical engineer. This followed a month of erratic performance by the calibrator - with unstable output currents and variable rise times. The problem was trced to the output current from amplifier Al being non-constant. The 3.9 V of zener diode CR2 and gain of transistor Al put this output current theoretically only just on the safe side of constant. Zener voltage was reduced to 3.3 V (IN4728 replaced by IN748) and transistor Ql (2N3566) replaced by a transistor of higher gain (2N3053). The calibrator performed satisfactorily after these alterations. The occasional instability to output currents still experienced is due to radio frequency interference from the standby transmitter on base. PPM: MNS2/2 tt The MNS2/2 failed on 22 October. After it was switched on, the displays failed to light and a burning smell was noted. A.Nutley traced the problem to failed transistors Ql and Qll on the internal power supply board. The transistors QI and QIl were replaced by the only available spares on base; QII by two 2N2484 transistors and Q1 by a 2N4032 transistor. The oscillation frequency of the supply was reduced (by a parallel capacitor) to allow for the reduced performance of the replacement transistors. These alterations produced a satisfactory although sometimes sluggish performance for the MNS2. 11

16 TABLE 1 STATION DATA FOR MACQUARIE ISLAND 1982 Geographic latitude longitude Geomagnetic latitude longitude Elevation (m) Foundation Magnetic Absolute Hut ' 'E Basalt Seismograph Station (MCQ) 'S 'E 14 Basa lt TABLE 2 OBSERVED MEAN BASELINE VALUES, 1982 Date 1982 HORIZONTAL INTENSITY Jan 01 Jan 25 Feb 02 Feb 11 May 22 Jun 09 Jun 16 DECLINATION Jan 01 Feb 01 Oct 25 VERTICAL INTENSITY Jan 01 Jan 25 Jun 27 Jul 07 TEMPERATURE Jan 01 Jan 25 Mar 16 Jun 10 Aug 04 UT Baseline BHs nt ~ ' ' ' BZs* nt BT C Standard Deviation Remarks 3.2 nt 0.0 Adjustment Earthquake Adjustment Earthquake Adjustment Adjustment 1.0' 0.8' 0.7' Declinometer changed Drift Adjustment Earthquake Earthquake Drift Dr; ft Thunderstorm ~---- * Derived from Hand F (MNS2/2). 12

17 TABLE 3 MAGNETOGRAPH PARAMETERS, Dates Scale Value Temp Calibration Coil Co-efficient current constant HORIZONTAL INTENSITY Jan 01 - Jun 14 Jun 14 - Dec 31 DECLINATION VERTICAL INTENSITY TEMPERATURE nt/mm nt/m 2.38 min/mm nt/mm 1.42 C/mm 3.0 ntj"c o 0 TABLE ntj"c 60 rna 8.04 nt/rna 20 rna 8.04 nt/rna 40 rna 7.49 nt/rna ORIENTATION TESTS FOR LA COUR VARIOMETER MAGNETS, 04 OCTOBER 1982 Component Deflector Reference Field Magnet N Pole Orientation N-Pole H D Z coil ( 300 rna) co il (400 rna) Magnet (at 115 cm M = nt.m nt '(E) nt East North North North East Down 13

18 TABLE 5 ' Year ORIENTATION COMPARISON, H D z TABLE 6 PARALLAX TEST, 03 AUGUST 1982 H D Z T Trace Correction +0.3 min -1.8 min 0.0 min -1.2 min TABLE 7 PRELIMINARY INSTRUMENT CORRECTIONS, MACQUARIE ISLAND, 1982 Magnetometer nt Correction nt/oersted (H = 12665nT) QHM 177 QHM 178 QHM 179 ASK ASK MNS2/ o o

19 TABLE 8 PRELIMINARY MONTHLY MEAN GEOMAGNETIC VALUES AND K-INDICES, Month H D (E) III F K (1982) (nt) (, ) 0 (nt) (nt) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec MEAN TABLE 9 GEOMAGNETIC ANNUAL MEAN VALUES, Year D(E) I H X Y Z F 0 (, ) (, ) 0 (nt) (nt) (nt) (nt) (nt) MEAN ANNUAL CHANGE

20 TABLE 10 REFERENCE MARK AZIMUTH, 1982 Mark Code Description Azimuth AR NMI NMXI SM Anchor Rock Rock format ion near western shoreline 01 d auroral camera stand The Nuggets rock formation ' ' ' ' TABLE 11 MAGNETOMETER COMPARISONS, 1982 Date (1982) Inst A Inst B Difference (A-B) at H = 12,800 nt Oct 26, 27 Oct 26, 27 Oct 26, 27 Oct 27 QHM 172 QHM 177 HTM 704 QH~~ 177 Ask Ask Elsec 595/144 MNS2/2 Through Routine Baseline values Jan 01-Jan 24 QHM 177 OHM nt QHM nt Jan 25-Feb QHM 177 QHM nt QHM nt Feb 02-Feb 11 QHM 177 QHM nt QHM nt Feb ll-may 22 QH~~ 177 QHM nt QHM nt May 22-Jun 09 QHM 177 QHM nt QHM nt Jun 09-Jun 16 QHM 177 QHM nt QHM nt Jun 16-Dec 31 QHM 177 QHM nt QHM nt + 16 nt ( H) - 12 nt ( H) - 3.6' - 3 nt MEAN QHM 177 QHM nt ( H) QHM 177 QHM nt ( H)

21 TABLE 12 SEISMOGRAPH PARAMETERS, 1982 Willmore Mark II Seismometer Free Period AS320 Preamp. filters Low pass filter cut off Amplifier Attenuator Settings Gain at 1 Hz Pol arity 1. 0 s 0.1 Hz to 12.5 Hz 2 Hz AS320 AR311 Jan 20 Aug 19 Aug 20-0ec db 24 db Page up = Ground Motion Up TABLE 13 LOCAL EARTHQUAKES FELT ON MACQUARIE ISLAND, 1982 Date 1982 Arrival Time (UT) S-p (sec) Intensity (ML) Feb 02 IPD II I - IV Feb 02 IPC III - IV Mar 10 IPD II Mar 21 I PC II Apr 20 I PC I I May 22 IPO II - I II Jun 24 IPO II Jun 27 IPD III Jun 28 IPD I I Jul 07 IPC II Oct 05 IPD II Oct 03 I PC I I Nov 19 IPC I I 17

22 100 Jan 20- Aug 19 at I Hz :>:: c Q "0 u <= 01 0 ~ 10 Aug 23-Dec 31 Magnification 2600 at 1 Hz 01L L L ~ ~ ' PeriOd (sees) 24-2/29 Fig.1 Macquarie island, SP-Z seismograph calibration curves, 1982

23 R (19 8 Kn) v\alv~-----~ ~g Underground Line from AS320 =r C (4/lF) Preamplifier --1 : -$'1 Fig. 2 Electronic fi Iter installed in seismograph, August /30 AR 311 Amplifier Input

24 50 40 E E,9 30 U <Il ;;: <Il 0 20 c <Il Measured, ortnogonal deflection --- Constant sensitivity of 27,6 mm/v - measured sensitivity for deflections < 15mm 0,5 1,0 I Input Voltage 3,0 1,5 Fig.3A Response of AR 311- recorder pen to in put voltage, u G: 1,3 c,2 U 0) ~ 12 u 1'/ Corrected Deflection: Measured Deflection ~ Correction Foetor /,0'-----""""::-..--' ' ' ' ' eo Measured Deflection (peak to peak) Fig. 3 B Corrections to measured seismograph deflections, 1982