Rapid diapir growth, a triggering agent 

of a 6 1/2 magnitude earthquake on October 29, 1966, 

in Acarnania (Greece) 

A. G. GALAI\OP01:LOS - A. l~KOXO)IJDWJ " 

Rece iyea on Jul y 28t.h, 19i3 

Ru'nIAR..... - 'l'he]"(J exists guud evillence that Iliapir gr owing occurH 
at a rate similal" to j·he rate of sedinH'ntation. Taking this into aeroun l , 
il is rel\.fJonable to assume tlmt aifTerential, rnpid lualling, dnring the filling 
of tlw Krmllasta !"eseryoir, cOlllhinel1 wit.h a Ileeper pend.ration uf liuills, may 
have affertell the large.scale ddormation of the Tl"iassie stl"ata of gypSllm in 
Acarnania allil prubahly inereasea Iliapir gruwt.h at a cat:1strophie rate; 
cllnsequently long·tel"ln stahility of the diapiric formaHuns of g;qlsum 
Ilishuhell hy eXI~essiye Ildul"lllniiun mHy hnve resuHel1 in n premature re· 
lease of t.he regional strains in tlw fOl"ln of a Yery shallow muUIIJ1wke on 
Oetober 2D, 1%6. 

RI ASSU:'iITO. - Esist.ono huone t estimonianze che l'acrresdllwnto Ilei 
di:1pil·0 aYYenga cun una velocità pari a Iluplla di sedimlmi"azione. Pllr!{'llilo 
da lJ1wsbl premessa, è mgionevulc ]J1"esumere che l" impruyyiso eal·ico, a 
seguito del riempimento Ild hadno Ili Kl"Cmasta, sumllwto illl una più Ill"O-
fondn penetrazione ai liquilii, possono aver contrihuito alla Ildonllazione 
Ili granlli proporzioni s u hit.a Ilagli strati Trinssiei ael gesso in Acarnania 
e prO\labilmente ayer aumentato in llllllJU catastroficu In velueitil. Ili aeere-
seimento ael aiapiro; di conseguenza la lunga stahili t il delle formazioni 
diaJliriche Ili gesso I\isturbate aa eccessiya ddonll:1zione, possono aveI" pro· 
VOC:1to una prematul"a liherazione delle t.ensiuni regional i sfoei:1t.a quest ' ult i-
ma, il 29 Ott.ubre HI6(i, sotto fonua Ili un t.elTmlloto molto SUI1(JJiiriale. 

rt is rat.her well establiHhecl ancl generalIy aeeeptecl that many 
triggering forees of relatiyely small magnit.nde, in pomparison with the 
ma.in clee})-seatecl strain producing forees, ma~T ehange nncler eertain 
fayourable eonditiollS the mte of strain release in li st.ressed regioll 
being cIose t{) breaking strengt.h ('l. 

(*) Kational Ohservatory of A t hens. SciSlllologil~al Insti t ute , Athl'ns 
(Greece). 



"\ft"l'a IOIl,!! !:w]; ()]' ('omplet(· ab.~CIH'e or Ilefltl'lll'tiYl' ,~ho('kfl ill 
Illl' Wl'st"I'll ]IH1't of N'!ltral Gl'ce('c :ln 111l11~11a1 l':lrt,llqUHkl' HetiYity 
fltal'tl'd ili th" Kl'l'mH~hl tlam Hn'H Hbont thl'ee mlJlttlls H l't {'l' impounlling 
or the mtijj('iallake (l!Wi'i, ,Jn1~' 21) in the fln'a or tlle CanonI Y.Olll'. 
TJJ(~ aetivity ('\llmi!lat('d ili tlll'l'f' O l/J to ti 1/2 nmgnitllde fl111Jf'b 011 
Fl'bl'llHI'.\' ;'), IDOli, Of'toher 2!l, l!)OO Hlltl ~"H.\' 1, HHi7. 

'l'hl' GHVI'OYO massir fOl'm,~ a fallltl'd alltk1i11(\ with SX"\Y-i-!i-!1!; 
nllllling axiH lw1011gillg to thl' ChnTOYO - Tripolifl zolle: it ('ollHists of 
Cp]lPl' ('l'l'hH'l'llUS n'l'f liml'sto!ll's alli l TNtial'Y lim(\~tollcs ~1l1'l'oU11111'tl 
by llysf'h dl'posit~, Oll ('"vitlell('(\ of thl' "lllStitut: F1'l\!l~ai,~ du Pf'tl'O!t'" 
(1.F.P., l!WO), qlloll'tl hy Hi('htN HIII! )Ial'iolakos (' ), lite l'a, H/OO m 
thil'k 1:"ppcr ('l'l'tal'l'ouf! liml'stolll'S OY('1'lil' l'H, 1500m garly ('l'da·l'l'OIlf! 
Hnd JUnlssie limefltollef! H11d H 'rl'iHflsie fOl'lllatioll or a salt ('U.~JJiOll 
(g~'psum, anh~'lll'itc alili dolomitl') of ullkllOWll thieklll'S.~ (s, Fig'. I), 

.At thc lwginllillj.{ of Ihe llyM'JJ dl'1JO.~itioli i11 Ihl' T011iHll Hl111 UHY1'OYO 
wlIe ai: thc Cppel' 1!;ocelle tllifl area 1'I'pl'CScnted aH uplifL tlmt wa~ 
('on'l'l'd wilh thl' 1l~'M'h not lwrol'c the Olij.{of'e!le . ..1f'l'ol'ding to n,l{il'h-

I In ,,- z~ I 
--~ E 
---'" - 1 

. . .. _ rr------~"----~_------~:_tl---_ -o-_~ ___ ..--~_ ~ 

_o~_'_'"_-r~ _. ~ r · I ' · " ·- ' . . -Terti.iir 
"-.... ,..-. .. ~ .... , ... v., ... " .... 

Ob",- I 
Kreide T 

I -. 

, -, 

Trias 

Fig, l - t4!mtigraphy of (~a\'l'ovo ZOlle aml illlwr !oniall zone afte!' Dietel' 
Hil'htel' ani! llia~ ~Iariolak()s( · ). 



{)1!7 

tel' HIHl r. ;\[~\1'iolnkoK (') 11](' IIplift lUO\'l'llWlIl W,IK ('amwd h,'" linlokilH'~is 
(s, Fig, 2), p1'O(1l1('ill~ lIUlU('ml1S fnlllt~ tltnt ~tTikl' lIpal'i,'- pamllel to 

Ihe (1in'diol! of tlte (hl"l'o"n allti\'lim', 'l'hl' f(nlUC 1l'!'Inni\' ('\'o]u1io1i 

wai'! 11111 fonnml by ,\,G. Ya~ii(' n fuI' the t'amarilh\K ~()l'~(' il! t':\pain. 

, 

b 

, 

~ 
Fly~ 

'l'' 'II I 

. . . . . . . . . 
.~ ... . . '.' . . . . '.' 

-

, , , , , 

~ 
Kl'llide-Kek 

, , , , , 
~ 

'. ' . 

Ju 01l _K a lk 

, , 

Q' , , , , , , 

". ~ , ... -
" .. -
-

'- -
, .... 

SIIlnr-Seoian 
del" Ttia5 

}'ig, 2 _ :--;('!wlI,alie dia!!;!":!!" showilll!; 1111' uplilt l'rol'P~~ ,,( Ganol'o 'l<1s~if 
aH('I' Dip({'l' Riellh'l' alld ilia;; 'larioJakos ( ~ ): 

a) '1<1I'gi"<11 1ll0\·PIII('llt 01 ~alt jow<1l'ds 1111' (;<1\"I'O\"" 1I1'pa durill!!; 1111' 
high('I' I·PW'I' \'l'('ta('l'ou.~, 1'11111('0("'11<' allOl EoePllC; 

l,) FOl'lwd,ioll o l il. ~aH (·lIKhioll iII t.lw (;al"l'ol'o an'lI il1ld :l('(','jpl'atr'd uplilt 
a 1 I hl' ln'!!;illllill/! o( fiyse h ,kpo.~i t iOll, 1'I'l'akillg o Il' 01 h lI!!;(' fl'aglllJ'llt.~: 

I") Dilllillutioll or Ul'lift il1ld ('(jualizatioll or I!w l'('lid ill Ihl' ()lig(l('('IlC. 



<0 8 A. ~ . GAI.,U.iOl'OUl.OS - A. EKO!oi(HU])ES 

Thcl'C cxists go()(l cvj(lClleC tlmf, diapil' gl'Owing oceul'S at. a rate 
similar to the rate of sedimentation (~). Taking j,llis ili Lo account, it 
is l'easonable to assume t.ha,t, ilifTcl'ential, l'ftl)id ]oading, !lUl'ing thc 
filling of tIte Kl'ernnsta l'l'sl'l'yoir, eombined with a deepel' l)Cnetl'ation 
oI flui(1f;, m,t)' ha ve aITertcd tIte hu'ge-sca.le defOl'mntion of t.he Tl'jassie 
strata oI gypsnlll in Acarnania aIHl lli'Obably inel'eased diapil' growth 
Ht a catash'Ol)hic rate; C'ollsequently long-tcl'lll f\tability oI t.hc 
(liavil'ic fOl'mahons of gYllsum disturbeil by excessive ileformatioll 
mfly lmvc resnltcd in a. ]ll'cl1latnrc l'elense of the r('giolln,] stl'ains in the 
fonn oI [\, Yer,\' shallow earthqwtkc OH Oet~)I)C1' 2D, ] D60 (:{8.f)o~, 21 J oB; 
h = 1 ± 5.i) lcm, J.1I. = 01/2). The restrieLion of the highest inten-
sity ("VIII) to jmt one locnlit.y (Kn.tomm) Sl)etl,ks well for t.lte shallowness 
of t.he focus. 

A ,;imilar ea,se, well documented, was observed at the ilum site 
in Lhe CanuHillrl,,~ gO!'ge, Svain, lh-wember 8, 1961, ami p!'esumably 
at. the dam f!itef! of Ca,nelles·Sa,nLa, Anna, Spnin, June 9, 1962 (P) and 
also a,t the ilam site of Oued Fodda, in Algeri,t, from JalHlary t,o 
l\Iay 193:1 (G). There is eviilenee in speeta.eular fashion that movcment 
of the salt is even now a.l-Tecting t.he Ul)permost f!ediment layers at the 
sea tloor of west.ern l\lmlit,elTanean (7), 

Ba,rt,hquake,~ triggered by Ira,te!' loading and/O!' lulll'ication a.re in 
generai af!sociated with normal faulting; thif! wa .. ~ the eaf!e of the Krema· 
sta earthquake on February 5, 190G (:19.1°N, 21.7 nE; h = 1G ± 4.7 km , 
.M. ,.--c O 1/4). The Ka,Lonna, earthquake of Oetober 29, 19GG, was 
associateil with thruf!t faulting (,~. Fig. 3); this is in aecordanee with 
tlmt one shoulil expect if rapid dial)ir growth has aded as triggel'ing 
mecha,niMn (f!. Fig. 4). 

The el)icenter of the second late 'Lft,el .. ~hoek of :!Ilay 1, 1967 (39.6°N, 
21.:1°B, h = :H ± :~,2 km, .M . = 61j2) ami t.hat of October 29, 1fJ66, 
are almof!t eqni(lista.nt from Lhe epieenter of the Kremasta earthqmLke 
oI Fcbruary 5, 19G6. The fault meeh,tllif!ms of both late aItershoeks 
wel'e simiIa.r, Le, of reverse type; it is then l)Osf!ible the evapol'ites to 
exten<l northw anls ami t.he same triggering agent. to have also act.c<l 
in the case of the ])r(W1IlCghc earthquake of lIIay l, 19G7. 

The l'ate of (liapil'ie proeesses is rclativcly grcatel' when dial)il's 
are al)proaching or rcaching the wrIa.ce (s. Fig, 4); t.hus the rat.e of 
movement of evapol'ites a,t fa!' grea,t.el' dCl)th should be ma1'iwdly less 
tha.n the ra,te of growth of a well-devclopc(l diapir apIH'oaching the 
surface. Thif! might CXl)lain, at leaf!t to some extent, why thc l)l'og!'es-
sive, jC1'ky l'elief of t.he regiollul stress fielil was manifesLe<l disastrously 



" 
:' ,', ,', ,' , ,', ,', ,', 
" 1:1: 

~ 
l2l'TIl 
~ 
~ 

c::J 

III,' 
,' ,' 

', II 
I,. ' 
', ','1 ' 1',', ,I, ', 

' I li 

:':': :1, ', 
' ,III , ,I:!:' ' 1111 ',l, II' ,' III' , ",1 ,' 1,111 :' 1 ,111, l ,II ,', 
" ' I :':1:' , ' ',' l'l' I ' 'I: 

" 
']f l ' 

:1:1' 
,', 
:' I :! ~ , ,':' 
'I: 

Tonian Geosynclin e 

Tripolis Ridge 

Olonos-Pindos G eosyncline 

Post-Tectonic Deposits 

Pela!;lonian Rid!;le 

o " 

~·: .. .'.'::;:I 
t:·:·:·:·:·:·:.:.; 

@] 

~ 
~ 

East Siop e 01 
p la t e 

Apullon 

West Si de al Pelagonian 
Ridg e 

Outcropin!;ls 01 dìapyric 
Tr,oss'c Gypsum 

Front lì ne 01 Upthrusts, 
dash e d when probobl e 

Normal Faults, doshed 
wh e n probobl e 

" SO " .. 

l<'ig. 3 - Stl'lw!urnl lineallHl1lh, (l) alHl fanH. . p!allt' so!ntiolls iur tho llwill 
eartll1l'Jake of 10uu, }'ebl'. 5, and tlw two late afh~l'Rhoeks of 101i1i (Jet.. 20 
and IOni, :lTay 1 (~) . 'l'ho iucnl lIlcchanis1ll8 arc shown as cqnal . al'ca 
pl'Ujections of t.hc, low(~r foea! helllisphel'c. 'l'he upell cil'clcs arc (.hc axes of 

cOlllprcssiull, P, anù the e!oHed dl'deH are t.lw axes of tension, '1'. 



, b' 

6 

5 

:; ;:; == ....•. 4 

: ;; :: 3 
" 

b' 

::; ::; 2 



at Katouna, in (hl' uo)"111 {'liti o[ (hl' ht ']1 of t.he on1el"Opini!~ o[ ~Iia]lil'it 
'l'\'ia,~~it' gyp.~lIlll (~. Fii!. ;.~), ea.i lllon1h~ {';ll'lh'\' (han al 11l'oMlp{'g-II('. 

'l'he .~tratig-[·a]lb.\- 01' Gny\'oyo zone antl inne\' louiall zone nntl th" 
u]llift l)J·o("P.~~ of GaYl"oYo IlJaH~if (~), lllnke the SIl!!'g-,,~1 ion of n mpitl 
tliapir !!'J"ow1h 1willg l'e~ponsihlt' fol' 11l(' l·l·[jPj' o[ (be n'!!'iollnl .~tI'PSS 
til'ld mon' ('edaiu. 'l'II{' ùlen i~ ('()]"]"o1!ol'a1ed b~- 1hp pn'~l'n('{' of IlIHIl~­
'VHI'1lI .~nlplHll·{'lm~ s]ll'in!!'~ in tbe al'{'a "oIl~i~I{·I·l·d; tbe {'.\i~1pnep of 

. -'\----1'" - " 
'--.. ,...,.. ~ 

'---'-
L-_ _ ~~~~ ___ _____ __' 

I·'ig'. 5. - \I;qJ sholl"ing ('nl"tlll[1wke d('n~it,\' 01'1'1" a "YI'ar ]wriod, I !W.j..]!lil), 
nftl'l" two i1('ralioll.~. lh'll!<it~- i" 1Il('n~lll'('d :I" 111(' 1l1l1ll1wl' or ('\'l'nt~ pn 1).1 0 

IHli111l11'-longil mk J'(·dHllgh·. 

sn11lhnl'eom springs iIHlil',l1,('~ tbnt inno\\' oj' wl"fa('{) watet·,~ l'xlpnds aH 
de{'p ns lbe 'l'l'i;l.~sie gyp~lIlll la.n'1' al h'a~t. It sboultl he atltlell that 
.~lIlphllJ'('ou" Hpl'ings haYt> hppll do.~{·11 dw·in).!.' the eOlls1nH.:tioll 01' the 
Kl'l'llla~(:.a Ilalll. 'l'11i~ also 1lI11~1 han' l'onj\'ilm1{'~1 jo (h" (,bang-e of 
t.he stn's~ di,,1:rilmLion path'['n in 1be l'egion {·onsill('l'l,tl. 

'l'hl' O l!:!. nmgnitude eHI'1hqunk<'s Oli ()elo!w\' :!U, IUtiO, nnd 011 
::Uay 1, lUOi, lHWillg o('elll'l'ed in the a[(el .. ~lll)('k pel'ioll sta'l'tell hy th{' 



G12 A. G. GALAXOI'OIJLOS A. EKO:S-O\fIJ>ES 

Krenmsta cnrthl]Ha-ke on Fcbrnary 5, 1960, Oll thc ontf\kirts o[ tlle 
19H-l-19j"O nnrthl]nakc dcmit.y zone (H. Fil!. !'i), rc"eal thcir illt.crplay 
1111(1 dose eOlllleclioll; tllllS the lnlwl "lat.(~ aHer~ho('ks" wc hn"c pnt on 
them is well justified. 

The ('ellter of the enrthl] nakc dcmitr paHem OYcr t.hc "7 -ycar pcrio(l, 
HHi-l-19j"O, i.~ do.~e lo thc infltrnmcntal cpi('cnt.cr of tlle KrenUlsta 
earthl]ualw, i.c. aboHt 18 km lo t·he :North o[ the Kremasta (lam. 
r~oeat.iolls nnd [oeal (lelJths fOI" all ea-rthquakes are tho~e giyell by LS.e. 

ACJ(XOìYLEDG.ÌllEX'l'S 

'l'he autllors wi.~h t.o a.cknowle(lge tlleir gnltitHdc t.o Pro[essor 
.1. Hothe for ea.nillg" thcir attentioll to tlle Yagiic's "'ork all(1 pro-
"iding them with photo('opicf\ of Gourinanl'r; an(1 Yagiie's paper.~. 

(l) BOll~ 0\' ,\~, .T., G ,\ LA ;<>OPOU LOS, A. all(I DI,LI IIA~ IS, N., I !l71. - S('i'l-/l/ol<>c/o/l-ic 
J/I1}J o! (ireccr. "l'uhl. 8ds\lI. I11St. ~<lt. Ohs .. o\t!tl'llS illl(1 IllHt. (il'ol. 
~llhsll)"fll('(' R{'H.'·, (i n'l'l'l'. 

('I J)"",opouw.~ •. 1. ",,,I DEW,",,«. S., Jm. - 0". Ilo .1[,d"",I,,,, "I ""'" 
l<Jarlhlfl/rlkcx in i111~ ..!UfI ()! We"'/an Oreeci' lImi/hl' SlreiSiS Producin(j Thcm. 
l'n'Sl'llteti ill tlte EU1"lJp. ~I'iSlll. COlli. ~II'I·tillg III. B1"ilSO'", ROlliallia 
1!l72; ill pl'l'HS ill '''l\·e!llli{"al i'otl\(lit's", lO, BUl"ul"l·st.. 

(3) GALAN()r()n.()~, A., IHGG. - 'l'he Inf/nence o! l/rc FrIUII/w/i()1I o! J/llrr//h/!11 
I,r/~I' h'l~ t'r/lion on l,oca/ Harlhqaa!.-r .Idil'il!! in Ihe .lIli<'1I Hfl8ill _[rn/. 
"'\1111. G(\o1. l'il)'S lIellell.", 18, 2Hl·30H. 

("') (iEllA, I.'., 1\)72. - Hl'deH' o{ Sfili '1'1'e/OlliCiS iiI Hcll1/ioll lo Ihc l)i~flIi8ll/0! 
[(/(I/iol/dil'c l!"(ls!cs iII "'''1111 Fonlllrlion.·. "(il'(,]. ~oe. Alli. Bull.", 83, 
12, 3551·3574. 

(~) RICII'I"Jo;II, n. awl .'Ir'\HIOLAKO~, I., 1!173. - ()1i.~lholl/r.llmlllll, ~inllislrl'l" Ilich! 
bdil/lln/eo' 1<>!.-10,o·('dllllcllla(Oflixehe8 P/wcllolllcni l(. F(!lRrh-_1 /il1/fll'!"l/ nrf~ n. 
"N. ,fh. n{·oJ. l'aliiollt. Ahlt.", 142, 2, 1Iii'·170, 8tllt.tgart .. 

( ~ ) HOTIIlè, l'. ,1., H170. - S~iiSm"x .Irli/icie!~. '''l'ed.ollopltysi(·s'', 9, 21!i · 23H. 

(1) 8TASU:Y, .I. D., H173. - J[odc!"1(. fiaiSin 8cdimel(.1 De!orlll.(llion //.11 Srrll 
1'edonic~, Il' ~ '''I ~ rll ]1"dil('I"rI/I(.('IIII. AhHtra("tOi, EUl"OpC'<lll Geo]JltysÌt'nl 
t',)('iety, ;l,iil"i('h, ~l'ptelllh{'I' 2,;-2!l, ]1. 07. 

(~) lA\li:r-:, G. A., I!W!). ~ JfiCl"II.Nllrlhqlwk,,~ in HI'SI'IT()irs. "l'ro{"ectiiugs oC 
oC the ,Ioilll; ~YIl'lI()SilllIlOr ECCE/ARIS, Ke('olld ElI)"O]lea11 Kylllp08illlll 
Oll Earth(lun](e Ell!-(illeel"ill!-(", .'Ifiilll'og"l"aphc(l, ?lf[/(l1"i,l, pp. 211·3,;. 

(") 1",IIiCJo;, G. E., 1073. - 'J'er!"l~lIIolox!J Nm/Jf/(o·eiS. "R{lvi.~11l ,le Olll"<lsl'llbliens", 
pp. 7,l3·7IiO.