Earthquake accelerograms and attenuation of seismic waves at Oolong, New South Wales

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3 BMR Jurnal f Australian Gelgy &: Gephysics 5 198 3-7 arthquake accelergrams and attenuatin f seismic waves at Olng New Suth Wales Rn S Smith & A J Mcwin The first Australian earthquake accelergrams

1 3 BMR Jurnal f Australian Gelgy &: Gephysics arthquake accelergrams and attenuatin f seismic waves at Olng New Suth Wales Rn S Smith & A J Mcwin The first Australian earthquake accelergrams were btained frm an accelergraph situated in the Daltn-Gunning regin f New Suth Wales Preliminary results were btained fr earthquakes n 23 Nvember 197 (maximum resultant acceleratin m/ 52) June 1977 (21 m/s2) 4 July 1977 (95 m/s2) and 3 February 1979 (13 m/s2) Maximum grund velcities were calculated fr these earthquakes and isseismal maps drawn fr the earth quake5 at Bwning n June 1977 and 4 July 1977 These data were used t test the validity f the relatin Y == aebmr-c fr assessing grund mtin aud hence determining seismic risk Because f the uncertainties in the derivatin f analytical expressins fr grund mtins the fit t bserved values f acceleratin velcity and intensity is cnsidered t be gd The relatin recmmended fr use by the Seismic Sub Cmmittee f the Australian Natinal Cmmittee n arthquake ngineering included a depth adjusting factr C where (R2 = D2 h2 C2) When C was mitted a better fit t the bserved acceleratins was btained but a prer fit t bserved velcities The isseismal pattern fr the 4 July 1977 earthquake supprts the radiatin pattern expected frm the faulting suggested by the fcal mechanism and distributin f aftershcks The isseismals fr the June 1977 earthquake shw a different radiatin pattern; this suggests a different fcal mechanism ntrductin On 17 Octber 1974 BMR installed an accelergraph at Hillcrest abut 1 km nrthwest f Olng railway statin in the Daltn-Gunning regin f New Suth Wales (Fig 1) The instrument is a Kinemetrics SMA-l triaxial strng-mtin acceergraph munted n a cncrete slab abve a firm veneer f sil verlying granite The trigger threshld is 5 mm / s2 and the accelergraph perates fr as lng as the trigger detects grund mtin plus 1 secnds The accelergraph was triggered by fur earth quakes: n 23 Nvember 197 June July 1977 and 3 February 1979-the resulting accelergrams are the first btained in Australia n each earthquake the instrument was triggered by the S-wave and the largest trace amplitudes were recrded n the hri ntal cmpnents The accelergrams are shwn in Figure 2 The traces were digitised manually after phtgraphic enlargement (x3) at intervals equivalent t 2 ms Parallax between traces was allwed fr by measuring the alignment f the sharply defined trace endings The first three accelergrams were analysed digitally by the methds described by Denham & Small (1971) Hwever fr this study the 1979 acceergram has nly been hand-scaled The vectr resultant maximum acceleratins and velcities are given in Table 1 Duratins f grund acceleratins in excess f 2 m/ s2 were less than O5s fr the three smallest earthquakes and abut s fr the largest Results and discussin The Kanai scaling rule is f the frm Y = aebmr-c; Y represents the maximum grund ac celeratin velcity r Mdified Mercalli intensity (fr MM intensity Yi = ny) and R2 = D2 h 2 C2 D = epicentral distance (km) h = depth t fcus (km) C = depth adjusting cnstant M = Richter magnitude (ML) The values f the cnstants a b c used fr the arthquake Risk Maps f Australia were thse btained by steva & Rsenblueth (194) fr the Western United States f America (Mcwin & thers 197) The scaling rule was adpted by the Standards Assciatin f Australia fr assessing grund mtin and hence determining seismic risk fr the Seismic Zne Map f Australia (Standards Assciatin f Australia) 9 4 JUL 1977 Bwning 3 Crkwell JUN 1977 OOltn':'l 1 NO B 1979 & Gunn Yss c-? ; OMurrumbtemn ): <! /; NSW (' & g::qe ( ACT? i / CANBRRA p' '-') Quenbeyn '> 5km rlhquke eplcenlre Accelerqrph slijn - :: '::; _u ' r-- C! vc ''''''': 1/89'11 Figure 1 Map f snthern NSW shwing earthqnake epicentres and accelergraph lcatin

$4 RON S SMTH & A J McWN OOLONG 23 Nvember 1 -'------=== Lng ert l{p Trans i =:------------- yr-:: ------- OOLONG June 77 ng ::::_=_=:::::::::=_ yertutp _ yans t Trans 'WJ/ OOLONG 3 Feb 79 ng M '{ert$

2 4 RON S SMTH & A J McWN OOLONG 23 Nvember 1 -'------=== Lng ert l{p Trans i =: yr-:: OOLONG June 77 ng ::::_=_=:::::::::=_ yertutp _ yans t Trans 'WJ/ OOLONG 3 Feb 79 ng M '{ert Uf N''''' rans t 1-1s-1 lee/b9-18a Figure 2 Olng accelergrams Prints f riginal accelergrams recrded n 7 mm film The time scale is 1 cm/ s and sensitivities abut 3 m/s2/mm Data n the earthquakes and accelergrams are listed in Table 1; results fr acceleratin are shwn in Figure 3 and fr velcity in Figure 4 Spectral analyses have nt been made but perids f maximum acceleratins were measured frm the accelergrams and cnverted t frequencies Fr these earthquakes the frequencies increase markedly with increasing epicentral distance but we cnsider the data inadequate t draw any cnclusins Fr three f the fur results the calculated accelera tin withut the depth-adjusting cnstant clsely matches the measured acceleratin The exceptin is the result fr June 1977 where the measured acceleratin is much less than the calculated accelera- tin t is pssible that the maximum grund mve ments ccurred befre the accelergraph began recrding The nminal delay between triggering and full peratin (quted by manufacturers) is 5ms which may have been lengthened by lw battery vltage The small gap in traces between the end f ne recrd and the beginning f the next is nrmally cnsistent eg fr the earthquakes n 23 Nvember 197 and 4 July 1977 the gaps crrespnd t abut -7 ms Hwever fr the earthquake n June 1977 it crrespnds t abut 9-12 ms Fr the three earthquakes f 23 Nvember July 1977 and 3 February 1979 an attempt was made t derive new values fr the cnstants a b c in the Kanai scaling rule fr acceleratins withut C Hw ever the results depend critically n the acceleratin values The values btained a = 83 x 1 7 b = 4 c = 982 differ frm thse previusly in use in par ticular values fr 'a' and 'c' are unreasnably high; realistic cnstants can nly be btained frm mre recrdings Maximum resultant velcities were btained frm the digitised accelergrams by integratin f the accelera tin values and frm measurements f the acceleratin and perid f grund mtin recrded n the undigi tised 1979 accelergram These velcities (again with the exceptin f the result fr June 1977 when the velcity measured was very lw) are nly a fair fit t the velcities given by the Kanai scaling rule; the discrepancies are wrse if the depth-adjusting cnstant (C) is nt applied Abut 5 arthquake Reprt questinnaires were distributed prmptly after the tw Bwning earthquakes f June and 4 July 1977 Frm the analysis f 7 reprts returned and interviews f 1 residents in the epicentral area isseismal maps shwing intensities (MM) were drawn (Figs 5 & ) The bserved isseismal radii are each the mean f eight measure ments at equally spaced aimuths arund the epicentre and are cmpared with thse calculated using the Kanai relatin in Table 2 and Figure 7 The calculated radii are a gd fit t thse bserved fr the lwer Date 23 Nv 7 Jun 77 4 July 77 3 Feb 79 Time (UTe) ' Latitude (S) 34 ' 34 ' 34 47' 9 1' Lngitude () 9 ' 8 54' 8 53' Magnitude (ML) Depth (h km) Distances (km) S2 = D2 h2 R2= D2 h2 C2 picentral (D) Hypcentral (S) AdjustedR 2 38 Acceleratins (m/s ) Measured Y (with C) 3 Y (withut C) 93 elcities (mm / s) Measured Y (with C) Y (withut C) 32 Dminant frequencies f(h) 17 Y = 2eO8ML R Y = 1e ML R Accelergraph c-rdinates : 34 44'S 9 98' Table 1 arthquakes and accelergram data (1) 3 18 (19) 35 11

3 N ARTHQUAK ACCLROGRAMS OOLONG NSW S <f) UJ ' UJ U U 2 1 With C ' J J ' ' Observed acceleratns 'j t) v J } Calcutated acceleratins N 2- n 1 Withut C :;;! 1 Observed acceleratns - - Calculated acceleratns 1 t) J ' 2 1 2u Figure 3 <f) UJ 13 g J'D2 -h 2 c2 (km) (km) 15/B9-19A Observed and calculated acceleratins--olng NSW Plt f the relatin between bserved and calculated acceleratins bth with and withut the depth crrectin factr 'C' Data are listed in Table 1 With C jl :;; J ' J Observed vetactiies Calculated vetactiies J ' 2 1 Withut C J :::;; ' ('l ' J } Observed velcities Calcutated velasllies '1 2-5'! W D2-h2C2 (km) 2'5i 2 (km) 155/89-2A Figure 4 Observed and calculated velcities--olng NSW Plt f the relatin between bserved and calculated velcities bth with and withut the depth crrectin factr 'C' Data are listed in the table

RON S SMTH & A J McWN Cndblin 8 Parkes The maximum acceleratin f the earthquake n June 1977 was prbably nt recrded because f an instrumental malfunctin 15 The Kanai scaling rule can be used t

4 RON S SMTH & A J McWN Cndblin 8 Parkes The maximum acceleratin f the earthquake n June 1977 was prbably nt recrded because f an instrumental malfunctin 15 The Kanai scaling rule can be used t determine maximum grund mtins expected in the Daltn Gunning regin f NSW fr earthquakes at mid crustal depths Ktmba fl 34 The cnstants adpted (steva & Rsenblueth 194) give realistic estimates f grund acceleratin velcity and intensity Temr t is nt pssible t redetermine reliable cnstants fr the Kanai relatin with s few data; mre recrdings are necessary stimates fr acceleratin are imprved but estimates fr velcity wrsened if the depth-adjusting cnstant is nt used Hlbrk The radiatin pattern f maximum intensities bserved fr the 4 July 1977 earthquake cnfirms the faulting suggested by the fault-plane slutin 3 C eam The radiatin pattern fr the June 1977 earth quake suggests a different fcal mechanism but n fault-plane determinatin has been pssible 2km Dte ' June 1977 picentre Time 12 ' 4823 UT arthquake was felt Magnitude 4 5 ML arthquake was nt felt picentre ' Depth1Km Nmed place Zne intensity (MM) 15S/ B9-2A Figure 5 sseismal map-bwning earthquake June 1979 Felt intensities determined frm the replies t ques tinnaires distributed sseismals shwn delineate the bundaries between nes marked 4 July 1977 sseismals (MM) Jun e 1977 sseismals (MM) Distances (km) D bserved R bserved R calc R2 = D2 h2 C2 R calc derived frm emm = 2989 e15ml R-2 5 Table 2 Mean isseismal radii-bwning earthquakes intensities at larger distances but the maximum inten sities bserved nearer the epicentres are lwer than calculated The maximum intensity ne fr the 4 July 1977 earthquake is elngated alng a nrth-nrtheasterly axis parallel t the directin f the fault strike f the earth quake (veringham & Smith 1979) whereas that fr June 977 is elngated t the sutheast The difference in radiatin patterns suggest different fcal mechanisms but t few P-wave first arrivals were re crded fr the June 1977 earthquake fr a fault plane slutin t be btained Cnclusins Maximum acceleratins recrded were m / S2 (7g) n 23 Nvember 7 95 m / s2 (97g) n 4 July 77 and abut 1 m/ s 2 (:13g) n 3 February 79 Dle 4 July 1977 Time 2' UTe Magnilude 5 ML picentre ' Depth 2km 2km picentr e arthquake was fell arlhquake was nal felt Zane inlensily (MM) Named p lace Small figure beside slid circle indicates intensity is di fferenl frm ne desiqnatin ss/ a9-22a Figure sseismal map-bwning earthquake 4 July 1979 Felt intensities determined frm the replies t ques tinnaires distributed and interviews f residents in the near epicentral regin sseismals shwn deli neate the bundaries between nes marked

5 ARTHQUAK ACCLROGRAMS OOLONG NSW June 1977 Observed intensties Calculated intenslltes Acknwledgement The figures were drawn by S Ryle References R (km)! 'j: OJ a; 4 July 1977 ' OJ - Observed intensites - Calculated intensties R (km) Figure 7 7 ' DNHAM D & SMALL G R 1971-Strng-mtin data centre Bureau f Mineral Resurces Gelgy & Gephysics Canberra Bulletin f the New Zealand Scietey fr arthquake ngineering 4 1 STA R L & ROSNBLUTH 194-xpectis de temblres distancias mderadas y grandes Sciedad Mexicana de lngenieria Seismica RNGHAM B & SMTH R S 1979-mplicatins f fault plane slutins fr Australian earthquakes n 4 July 1977 May 1978 and Nvember 1978 BMR Jurnal f Australian Gelgy & Gephysics McwN A J UNDRWOOD R & DNHAM D 197arthquake Risk in Australia BMR Jurnal f Aus tralian Gelgy & Gephysics STANDARDS ASSOCATON OF AUSTRALA-AS2121-The SAA arthquake Cde 155/89-2'A Observed and calculated intensities-bwning earthquakes Plt f intensities shwing the relatin between cal culated and bserved radii f isseismals BMR Jurnal / Australian Gelgy 4< Gephysics Manganese ndules frm the Tasman Sea ff Sydney N F xn D Mretn l G Hicks l Tw manganese ndules were recently recvered by HMAS Kimbla frm a water depth f m in a nrtheast-trending trugh abut nautical miles sutheast f Sydney (155 35' 3 15'S) They were assciated with greenish gray calcareus mud laid dwn belw the lyscline but abve the carbnate cmpensatin depth The ndules are subspherical lind abut 1 cm in diameter and have a high clay cntent a lw Mn:Fe rati and lw cntents f Ni (%) Cu (17%) and C (%) During a shrt gelgical cruise in May 1979 by HMAS Kimbla t whse captain and crew we are mst grateful tw manganese ndules were recvered frm the deep sea abut nautical miles sutheast f Sydney (xn 1979) Sampling was carried ut using tw Benths free-fall grabs at each statin; they sample a bttm area f abut x cm and trap material 1 Sch()l f arth Sciences Mnash University Claytn ic 31 in a net with mm mesh Statin 5 at which the ndules were recvered was at ' 3 15'S miles nrthwest f Gascyne Seamunt and the esti mated water depth was m The samplers re cvered 1-2 kg f greenish gray calcareus mud and tw large manganese ndules The mud is 17 percent sand 4 percent carse silt (-3 micrns) and 79 percent fine silt and clay and cntains 28 percent CaC 3 by weight The carser fractins are dminated by mainly whle but crrded

ACCELEROGRAPH RECORDINGS OF THE M USA EARTHQUAKE 16 SEPTEMBER, 1972

115 ACCELEROGRAPH RECORDINGS OF THE M USA EARTHQUAKE 16 SEPTEMBER, 1972 B.Gauir SUMMARY On 16 September, 1972 at 04 15 09.8 UT an earthquake f magnitude ML 5.0 ccurred in sutheast Papua within abut 20