HomeMy WebLinkAbout2001-01-09; City Council; 16026; Request Presentation/Seismic & Tsunami ThreatAB# f&&&f-b
MTG. I+- 9-24
DEPT: CM
2lTY OF CARLSBAD - AGENuA BILL
TITLE: DEPT. HD.
Request to Give Presentation on the Need for a Seismic and
dfi!zL ’ Tsunami Threat Analysis for the San Onofre Nuclear Generating CITY ATTY.
Station
CITY MGR
RECOMMENDED ACTION:
Receive presentation from Patricia Borchman, a citizen of Vista, on the need for a seismic
and tsunami threat analysis for the San Onofre power generating facility (SONGS).
ITEM EXPLANATION:
The City Council provides an opportunity for citizens and organizations to have an item
placed on a City Council Agenda by submitting a letter to the City Manager. Attached is a
letter (Exhibit 1) from Patricia Borchman, who has requested that the City Council hear a
presentation on the need for a seismic and tsunami threat analysis for the SONGS
aboveground dry storage facility.
FISCAL IMPACT:
None
EXHIBITS:
1. Letter to Mayor Lewis from Patricia Borchman, dated November 27, 2000.
FROM : BE GOOD
November 27,ZOOO
Honorable Mayor and City Council
City of Carlsbad
1200 Carl&ad Village Dr.
Carlsbad, 92008
FAX NO. : 7609419625 QPr. 29 2000 01: 15Prl Pi
Patricia Borchmann ATTACHMENT 1
176 Walker Way REFERRFD VT C!T!".'f.NAGER
Vi@ Ca 92083 (760) 941-9625 Date:
RE: REQUEST FOR FOLLOWUP ACTION -FORMAL SUPPORT FOR tZlTIZENS’ NEED FOR MORE ExllENsIvE SEISMIC EIAZARD AND ‘CWMAMI ANALY!SIS ON SAN ONOFBE NUCLEAR GENEIUTING
STATION (SONGS)’ APPLICATION (EOO-QlS) FOR AN’ ABOVE-GROUND DRY STORAGE FACILITY FOR R4DIOACI’IVE FUEL ASSEMBLIES - PENDING BEFORE CALIFOMA COASTAL COMMISSION
Dear Horrorable Mayor and City Council,
On November 14,2000, the California Coastal Commission continued action on a pending
application (500-014) by Southern California Edison, to allow an aboveground, dry storage facility
for spent radioactive fuel at Sau OnoGre Nuclear Generating Station (SONGS). The Commission
instructed applicant to provide more hfbrmation about the site’s geology and potential seismic and
tsunami hazards, and because local governments had been left out, they should all be notified before
the matter is considered by the Commission again January 2001, at the earliest.
During this interim, I seek formal support by City Council members of various north San Diego
communities, to JOIN with the explicit concerns, aud persoltlll requests for time to rewiew md
comment on the application for this important public safety issnc, (by 3 out of 5 City Council members from the City of San Clemente -Berg, Ritachel, Eggleston). Due to the lack of prior
advance public notice on this proposal, there was insuEcient time for the City of San Clemente to develop a specific City request prior to the Commission’s November 14,200O meeting.
Them is now suddenly a small window of time to enable aff&ed, and potentialiy vulnerable
Cities to ACT. During this crucial lnterim period, I urge Cities in North San Diego County to
support CITIZEN’S NFXD for more extensive analysis and public safety precautions, and
potential plant upgrades if determined necessary, to assure certainty of both safe plant
operation, and absolute storage safety for radioactive fhei assembiies.
Specifically, I ask your formal support by the City of Carlsbad, for any, or all of the following: 1) Citizen’s need for time to evaluate the application and the seismic hazard and tsunami analysis
presented by the applicant in January 2001, and plant upgrades if determined necessary;
2) Updated, and upgraded emergency plans; 3) Broader public notice and disclosure by the Coastal Commission staff and the Nuclear Regulatory
Commission, inciuding an informatibnal public meeting with Nuclear Regulamry Commission
authorities on San Onofie issues.
I urge that this Council take immediate action, by direct& your &to conduct any followup
necessary to enable thh sIected body to take action on behalf of the public safety of your
citizens. Due to the urgency caused by time constraints, I ask that you agendize this at the next
available City Council meeting to take formal action. Thank you for your consideration-
PatriciaBorchmann
r- L
FROM : BE GOOD FFlX NO. : 7609419625 Flpr. 29 2808 81: 16PM P2
Cities in North San Diego County should direct any formal ktten OI support to:
Peter Douglas, Executive Director
California Constal Commission
45 Fremoat, Suite 2000
San Fra~~cIsco, CA 94105-2219
Refer to: Application E-00-014
Phone (415) !304-52@0
FAX (415) 9065400
Other Exhibits:
1 l- 15-00 Article in North County Times
11-l 5-00 Article in San Diego Union Tribune (Edison o&cials confirmed SONGS was designed and built to withstand an earthquake up to 7.0 Magnitude)
October 2000 article from Geology Journal - Offshore Blind ‘Ibust Faults Capable of Generating Seismic Events up to 7.6 Magnitude
FROM : BE GOOD FFlX NO. : 76B9419625
Commission delays
.
San Onof’re decision .
PHIL DIEHL
STAR WRITER
LOS ANGELES -The state Coastal Commissioners post- poned a decision Tuesday on whether Sourhern California Edison shouid be allowed CO build an abovc*ground, dry-stor- age facility for radioactive fuel at San Onofre. More information is needed about the sire’s geology and p tential seismic and tsunami hm ards, commission Chairwoman Sara Wan said. Also, she said, lo- cal governments such as the city
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FlPP. 29 2088 01: 16PM P3
of San Clemente should be noti- fied before the matter is con+d- ered by the commission agam. San Uemente, she said, was not notified this tune. The commission’s agreement to postpone the matter, proba- bly until at least its January meeting, satisfied the requests of about a dozen people, mosrfy San Clemente residents, who at- tended the meeting KO say the proposal was ill-advised and ill- considered. Commission staff members were instructed to study geologic issues further
+ ONOFRE, A-S
9
- -5. . . . . .
i4t WEDNESDAY, l4cmm~ 15,ZooO (ALL)
N ONOFRE
iontinucd from A-1
Nuclear plant seeks permission for above-ground storage
and prepare a repon. “That’s what we were hoping for,” said Lyn Harris Hicks, a longdme San Uemente resident who worked to organite people opposed to the faality. “No other industrial building that sire would be allowed on any oceanfront in California, let alone on a popular state beach.” Edison officials believed they . had presented adequate infor- marion for the project’s ap- proval and were disappointed Iwith the postponement, ‘spokesman Rai Golden said. . . . -. -. : - . .
Edison has requested per& sion to build three steel-rein- forced concrete pads at San Onofre for the storage of used fuel assemblies, often called “spent fuel,” from Units 2 and 3. The fuels would be placed in- side stainless steel canisters in- serted in concrete modules, with a total of 104 modules on the
pa& San Onofre now stores all it; spent fuel in below-ground, un= &water pools. Those pools are nearly full and will run out of space by 2007, Golden said. The Federal Department of Energy, responsible for the permanent smage of spent fuel, is unlikely
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seismic safety and other gee logical issues were explored thoroughly before the Units 2 and 3 react- were built in the 1970s and early ‘8Os, Golden said. The nudear power plant is among the. most earthquake proof snctures in the United States, he said.
to open a permanent storage fa- cihy before 2010. Fuel assemblies’are used up to four years in the San Onofre reactors. Once removed, the as- semblies remain highly ra- dioactive and must be kept un- der water for ar least five years or they will overheat and melt. The radiation dissipates gradu- ally, but the assemblies are ex- pected to remain hazardous for hundreds of thousands of years.. Executive Director Peter Douglas and legal Bcounsel Ralph Faust borht;zsed the commissioners even though the issue of whe’& to put spent fuel is “highly Sensitiven and “controvekal,” the commis- sion was not to consider the ra- diation safety of the proposed storage facility. Radiation safety is regulated by the federal Nuclear Regula- tory Commission, Faust said, while the state Coastal Conimis-
. . .,
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sion is to consider only qRters of coastal development “To the California Coastal Commission, it’s jusr e concrete
pad - not a radiation issue,’ Faust said. It should be consid- ered the same way as the con- struction of a hotel or house on the coast would be, he said. Still, some - commissioners said they felt it is their duty to consider the potential hazards of spent fuel. “Who knows what rhe impli- cations of storing this stuff on the beach will be?” Commis- sioner Christina Desser said. ‘There are a host of questions I have about it.” Commissioner Shirley Dett- loff -pressed similar concerns. “I’m having a difficult time dividing out where our jurisdic- tion stops, as, far as this being a safe site,= Dettloff said.
Coma staff writer Phil Dietd at (7601
9014087 or dieht@ncIimesrcm
\\-l5f+ pM+ @q-VW ” . . .
FROM : BE GOOD
Decision
FFIX NO. : 7609419625 Rpr. 29 2000 01:17PM P4
on nuclear . .wEBte site . .
ise:delayed
:’ ,.,I . -’
By iany Rod+ ’
STAFF WRITER
: ~0s J&&ES - Gting the ncul for
more illformadon. espedany on earth-
~quakeiafcty,thesfa?eCoastalCanmiS- sion here yestrrdap posqxdd i& de& sicnionapmposcdnud~~~~~ . “ki?ityatsanMNuckxGw-ring ‘station hear Occansidc 171~ delay chagrined ~uthctm califor- fia Edison &&ds who want to build storage space for thousands of spent fuel mds hm the plant3 hvo active nuclear
gtnfmtorsforuptoSOyean. We’re disappointed.‘ said Edison sp~komur Ray Golden. We think we pmvidtd adquatc infomaation for them to make a d&Son to&y.’ . .oppOnerrtt of the project were hean- ‘aed by the ccmmision’s acrioh -This shows That they me mcning.’ said &c St&man of San Clcmcatc. a
member of Groups United A&aim m don Damagt She said she opposes the pmjtd bt ‘muse %uch a large !hcility should not be buiIt on such unstable topography. Hoivcvcr, ycsterda+ action wiIl probzt bly have no real impact on tic project, since &al au&or& nss with the Nude uRcgldam~commission. As Coastal Commission Executive Db
rector Peter Douglas pointed out. fed&- law precludes commissionershmim- pasing any conditions on San Onofre’s permitAllthtcommissi on an do is ~4cwthcprojatke&stoncoastaire- =wccs, and oi’da adjjcnts to the
P%zt if it a&& public access, rcu+ don. tm&,light and noise. It wvuld take
lcgrltdiontoactudyaopthtpmjm
, set: San Onotrt, 83
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+ SAN ONOFRE
:ONTINULD FROM PAGE 61 Panel delays
decision on nuclear waste .* QueGioIs aboiit the seismic safety of the proposed proicct arose during a public hearing
yesterday dominated by t&i-
many kom oppontnts
Sierra Club spokesman Mark Massara told comrnh sionem that Sap On&e is not suitiblc for storage of radioac
tivc waste bcuuse of its prox- imity to tiquakc faults. its ssceptiiility to damage fi-om tidal waves and its C]OSUESS to a heavily used recreational beach. Weurgcyoutajustsayno,” Massara said. Coastal consultant Norbcrt Dahl advised conuzkionas to act cautiously because of a his tory along the California coast of major indust& and power plant projeas that had to bc redesigned because seismic llaards were ignored.
lfthithiStO~iSigTlored t.hentheperilfallstotheocmstal resow to the public and I& timacclytothcntcpaycrsofthc~ staceofca6fonliaurbailoutthe Llqitica that have an unbelicv- able ability to &c facilith in iI!llllediatcp~~tOhigh seismic ~rncs,~ he said Fault lines just offshore of the San On&c n&ear plant are capable of prvduhg an earthquake of 6.9 magnitu.dc on I
3 ficids said all fMlitic~, indud- Ingthetwoac&c~~on the 63.baue scn OnohE site were ctxis&ucttd to withstand a quake up to 7.0 in magnitude
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FROM : BE GOOD FAX NO. : 76094 19625 Apr. 29 2000 01: 17PM P5 .- _^
Oceanside and Thirtymile Bank blind thrusts: Implications for
earthquake hazards in coastal southern California
Carlos River0 John H. Shaw’ It Depamnent of Earth and Planemy S&noes. Harvard University, Cambridge, Massachusetts 02138, USA
tit-l Mueller Department of Gmkgkai scienas, University cd Colorado, Boulder, C&r&o 80309, USA
ABSTSACT
Wedefin~rctivcblindthnrsts~inoCErhore~~~~~~hwn
LorAlQdCSSOUthtOthtUnusd~~in~ borkThesebihdtbmstshrmed
by teeto& imerslou of Mloane exreadonal d&a&men& We attribute the 1986 Ocemsidc
(ML53)~ltbqurrlrgloul~~ofmarlnctcmccs,scrfloorfoldsarpsmd~gcodetic
colwergatcetomotlonontbaefimlllts.slugleand mu#iregrrmt cauunIpturcocarrriossu~
rJlepotentlalibrIarge (M7.1-7.6) brnlnlleqwntmrulqur that wouldafrecttbeLa6Angda
and San DIego metr~polit3n areas.
knd Gocansidc,
lN’lRODUCtlON
l’heimpottanceofblindduustfaultsassotuces
ofde8rmctivec3rthqu3kcsinsouthemcalifornia
wp5 - by the 1994 Nor&ridge (M 0)
CWXIL which caused more than $35 billion in
damage 10 metmpolitan Los Angeles (U.S. Om-
logical Sump and Soulhem Califomis Earth-
quake Center Sclentisrs, 1994). Similar blind
duustahavebeenpmpc6edtounderliemuchofdxe
Los &@a basin (D&s a al., lM19: ScIu&&r
a al. 1996: Shaw and Suppe, 1996; Shaw and
she3ra. 1999). In this paper we show that a&c
rhnr~dng extends to the offshore California
Boddmds. on the basis of analysis of marr: than
IOOOO km of .wirmic reflccdnn data. 771~6~
thrusts reactivate hliuoene extension4 dwh-
maw (Crouch nnd Suppe. I993 1. and may pose
significant hwads lo ctx~W1 CAifomh,
GCEANSIDEAND-
THRUSTS
Recent StUdics invoke lOWang& nomlal faults
in the N-ens formation of’ rhe Inner California
Bonledands and mzuion of the Transvemn Ranges
(Luyendyk and Horn&us, 1917; Crouch ad
Suppe, 1993: Nrcholrcn et al., 1994; Bohannon
ad Ceist. 19%: Inga3oll rind Rum-, 1999).
Through detailed mapping urd structural model-
ing. we demonstrate chat two of these Insults, the
Oceanside and Thirrymilt Bank dcrachmcno,
uwrd south from Layna Beach and Catalina
kkd, ra~vcly. LO Y less1 lhe hired state+
Mud00 intemational border (Fib 1). The exten.
sional nature of these fkulu is rcfleu~ in the
nod scpysticn of baxmmt (Figs. 1 sod 2). and
in the presmce of atmsional folds (mllovezs) aful
MiocclK grcnwh slnuxuIes (Wch nnd suppe
1993: BnhYlnon and G&I. 1999).
Here WC document Ihat hgc porlicns or lhese
detachmtnu have been reactivated to form the
Oceanside and ‘Ihirtymile Bank blind thrusts,
%oncsponding aurhor.
whichcomposclhe&nar~Bordcrlmdb:
blind thrust system Tectonic inversion of the
ocedndcdcnchmcntis-by3svbmernc
f~beltloalEuioffshoRbmveaI&na
Point and Oceanside (Fishu and Milk I99 I )
@ii. 2A), In contmst to the cx0cnvional m
thestconaa&nalsaucnuesdefotmPiiazncand
yixngcr~andarcocmmonly~atedwidr
pmnd~~Idscups.saucsaucnurct
donocutorfoldthe dcachnmt Thus; wc inter-
~lhatlhey~leintothe&ansidethru%
lhcOcaddch~is~overnn8m30f
more than 1800 km! Tn migraad s&mic r&&m
profiles, the thrust is imaged a$ a cohtrenr set of
..dn7ng&tionrlh8ldiplolhellorlheIurbuwl?tn
14°and250(Fi&2).7he~uatcnds~~abng
the Coronado Banks to the intcmational border
near San Dkgo Bay @ig 1). At Coronado Bank
hdng is rcflecccd by tectonic inversion of the
Coron;do Bank -t (Pig. ZB 3nd 2C)
(Nichclm et al.. 1993; Sorlien et aL. 1993).
The Thirtymile Bank thrust is W&C of the
Gcunsidc tiult, and also otiginatai = an am-
sional duachment (Less et al., 1992). The fault
dcfincs an almost linear, continuous acarp cx-
tending horn southwest of Catalina Island IO
7%@milcBrmk(Ag 1).Thchar@ngwallofthc
rhrusr mnmlns Neogane syruifc strata that arc
gmllyf&ledinam3nna consi6raRwitbdlNa
inversion of rhc undalying huh.
Gmwthsvlrainoon&xWnalfoldsrbovtthe
Oceanside and Thirtymile Bank thrust5 suggest
lhStltlnrscing~hthCFliOCtUC.Tll3Sll8llOW,
casl-vagalt fold-and-duust belt above the GcWl-
dderhntstbCtwCUlDwrPailUMdoce;msideL
themost&euevidexeforrhisrectonicimusion.
FoIds in this belt genemte pronounced seaflax
scrap that Fist for -30 km. Althou& these
sarpsmqymflectr#cnt~vitycfrhc~g
oce3nside ctuwt (Fig. 2). uloy ac not cldillidve:
WChCk~Yb~COIltd~333fhf~rs.
Howcvor, young oontractiond folds also occur
alongthecoastandinvolvcdalaltineruraccs
lkst srrucfurcs record recent fault activity that
m3ybc3alibutcdtorhe-thnrn
?beS3nhquinHiIisuc8rthcsouthemmar-
ginofthcI.osAngclcsbin,w~thcmap@
PJROftheckean&tblustcxWKlsalshore.Tk
hills qrr formed by a northeast-vetgent anticline
that uplifts and deforms marine tcmxes. Grant
Flgure 1. PwepecWo view dmmt3dImen3bmdm
d Oceanside and Thirty- mlk Bank blind tIwust~. Grey surl8ce Is top of bIl-(CaYPSChi?@
Small triangles Indkate areas of i&m uplift o.alde at al, 107% 1992: hie and G&h,. 19%
Kern and Rookwe& 1992; Orant et al., 1999; Kler and Muollw, 1999). Digital
sh3Q3Qrclrdm8Ddsoum- em Califomk t&ogmptly was derived from digital
U.S. Gaologlbl swve$ SAM-Santa Ana Moun- telns: SJH--Ssn Joaauln
Hills;PVP-Palw Vtis Peninsula; SCI-Santa
Geobm: caobcr m v. 2s; no. lo: p. s91-894: II fi$um% 891
FROM : BE GOOD FQX NO. : 7609419625 Flpr. 29 2800 81: 18PM P6
Subnmrine Fold-Thrurr-Belt
Fgurr2GeomebyotOceanddrthrustuI~h~rstlrcrknprofi~A;Mlgmlod~nlkctkn mknrolngsrgmrnt@f mM~dLaswnKnoll.Shwpmdcontin~refkcdionsdippinOto~defineI#liorrotthru~lNdcohJkvvk#m~balts~ OccrnrklamNrtmatproducsJ~~Rldocr~Thircontnttiolul~~dorrnocr~~mur.we~Occvuldcro tbasalmNlldaequcncc.Noteolder(Neogenc)ensndanrl ral~~obucrurrkrriedbyOlbacnccmdywn~~~anweerendol
emcdon. S: Migrated sekmlc Image of lkeeneldr thrust northemt at Coronedo Sank Ocxmddethrustmotlonlsmflectedbybroad, ~lold~~Ih~kwredimenCvyunibMdknnlnOkod~rkpe.C:Mlg~~mk~ - pmiaeauo8aCW6b8d thrust. which resides In hsnglng wall of Ocem~ldc thrust emt of Crcopi Knoll. Fault k deftned by oflset of top btsmmml mflectIon. snd PmdLlcelt con- fold with pronounced s&bor sarp. Unil S, is Yine l d Oligocmo(7) synaxtonsknml strata: SI Ic kk Mii Plioctuw postaxtendonal drape: So Is Iam Pllocma(?)-Holocene syncontmct&~I sfrata S, l nd S, are grouped where und~verlkelrco)alc-l:l;daaunk~~ -lLSlXtWl~~~-IllFlgU~1.
cl al. (1999) proposed that the rold is dcvolopod
above an active. southwest-dipping blind thrust
tirlipcatsr*Of6.420.79mm4fr.batbdOn
uplift rates of 0.21-O.n mm&f. Our seismic data
imge the ofMOre extension of this structure
~3).andC0n6nnlhntitf0nnedab0veashal-
low blind thntst with an average southwest dip
VdU Cd 23’. HOwevCr. this shallow fault is re-
strictcd to the hanging wall of the Oceanside
thu* at dep& we intaupret that this shallow fault
soles into the rhtua fosming a structural wedge
(Mdwedeff, 1992; Mueller et al.. lQ98). We
comb&d tbc obsaxd dip values for the back-
bust sysran (23’) and the Ocean&de thrust
(14”-259 wilh rhe uplift ran at the San Jo&n
HillSillW~-Wdgtmodtl;\nd&~
aslipmteondlettlntsrof0z-O.41lnln&.7his
slipraeyieldsanuplifcratenbovecheOcesnddc
thmsr. in ch6 absence of the backthrust of 0.&0.l7 mndyr. ‘his rcsuk is compatible with
rhc otcmwvcd 0.13417 mm/yr uplift rate of
mark EITSWS south of the San Joaquin Hills.
which extend to San Diego anti into northern
Mexico (Lqjoic a al., 1979. 1992; Banic and
Gada 1992: Kern and Rockwell 1992) (Fig 1). If
892
thcOccan.GdcblindduustisresQomibleforaIl~
partofthiscoastaluplifLitimpliestbacfherhnra
isactivefartothesoudrofdx.SanJoaquinHills.
We consider rhe calculated slip rates for the
Oceansidethnlatfobeminimumvalueskeause
tbcyaredaivedfiwnuplihrates.whichmayk
affectedby~ccompaaarion andlofflallral
sub&ncetbatnauyoocurductocnntaltbickon-
ing Ghaw n al.. 1994). To gown maximum slip
ntcs, we usa gcodaic obeavrrrions but indicrks
as much as 2 mmlyr of norbut-southwest
(N43OE) com~crgence betwoes Catalina Islaod
and the ooast (Kia and Mu&.r. 1999). Given
thatsbwtwingpIo&cedbyrhcoccassi&lhrust
shouldnotauMthisv~wccaIcubamaxi-
mum slip rate for the thrust of 2.2 mm&. Simi-
Figure 3.10~: Kinemmtic modal of Mind thnmt tarltingmdtemceupliftbenalhSmJomquln Hllk (Grant et I& 1999). LAB-Lo@ Angaka
badn; NT-Nmqort4qkwood MM zm0. Sottom: Mlgmtad sekmk mlkctkn profik
hrclging- emtuwknor~Iddy#m, wtaldrhasdmrbpedabme~dppingWc thnla7vvrr--Hubwpy~s--rcoondr
larly. lhe slip rate of 6te Thirtymile Bank thrust shouldbenomorcchan0.%mm$r,suchthatthe
resulmnc shaming does not mad the gcoduic
wnvergsnce rare of 0.86 mm& calculatotl
bCWCCIl-ISbUldaadSsnClWlUUClsland
FROM : EiE GCOD FFlX NO. : rG3419625 ,- Apr. 29 2000 01: 19PM P7
(Kicf and Mueller, 19%‘). which is west of the
l7aymileB5nkmlusf.
Toformerfunhsraaivifyoll Ihc loncrBoKlcr-
lands thrust system, and to determine if these
huh arc seimrogtnic. WC sought to establish the
ori@n of the 19S6 Oceanside (ML 5.3) earth-
q&c. The mainshock had a dominanf compo-
nent of thrust movement. whasls many of the
&rskckswcrcstrikslip(~nandJones
1988). Astiz and Shcarcr (2000) relocated the
cubhock sod atlsrshocks of rhc Oceanside
eanhquake by using the I,,-norm waveform
~oss-w~on methaI and quarry blast infor-
malionfKnncaIaliMIslaod.merrlocatedealdl.
quake sequcncc is clusuncd at -8 km de+, and
d&nes a 25”~Up an-dipping surface (Fig. 4).
Tko&muionandpositionofthefaulcplaneare conskfwt with the downdip projection of the
Tlhymile Bank fluusf. Thur we suggest that the
eardquakrupfnradasm~~pwiofthettuust.ra
veiling fhsacdvirysnd seismogenic poh&al of
thrusr faoits io the her California Bonhrlandn
SEISMIC-S
WC assess dr seismic hazard posed by these
blind thrusts using huh arcas to predict earth-
quakmagnitudeaandrecurrenceinmrvalsbased
an empiri4 relations among IUpNrC am slip
ne,yd moment magnitude (Wells and t3pper-
smith, 1994). Lacking direct evidence of huit
segmmioa we consider cumplctc ruptures of
da5 tilts 5nd rhur maximum carthquak magui-
rude skbough ruptures may occur in smaller
and more ffequcnt events.
We defined the seismgenic fault aura as the
intibcnuccnSkmdepthandthebaseofthe . esmogkccnlst3t20kmdcpth.LfthcOccan.
side flmIsT Npclms only along the e%Ient of the
Sao Joaquin Hills (1390 kmz), this would pro-
dU(raneanhqualoofM,7.1.Thismagnituflei.s
simik to that pmpo4 for a south-dipping blind
Flgurs 4.Thrwdhnenrlanal pernpealve otlhlrtymlle Bank thrust wItIt relocated hypocxmtsra of 1986 Oceanside earth-
quake (&et& and Sheerer, 2000). Note correlation between mapped shape and PosItIon of Thlrtymilc Bank thrust with
surfmoe deflned by relocated sfterrhook dustor. SJH-San Joaquln Hllls.
thrust (Grant cl al., 1999). but invokes an op-
posed northeastdipping seismic source. We con-
end, howcvcr,fhatcheOceaosideaod?hircymile
Bankthmstsareaaivcovrratcgionmuchlargez
than the extent of the San Joaquin Hills, on the
basis of tk Oceanside ear&qualm, ooastal uplift,
seamor scalps. and obsm!ed gwdcdc shorml-
ing.TodefinetheaeI;ugupoamnaltupturcarcas,
we must first ddrcss the interaction of these
thrustswithac&suikwlipfauIlsindw+on
(Fig. 5). The NewpottIngicwood-Rosc Canyon
fauJtsystemisabo~ofadjacenttodtcOccansidc
fluus Similarly. the San Diego trough strike-slip
fault is above CIIC Thirtymile Bank thrust.
We propose four possible interactions bctwczn
thee two class of fad. each & tion invoking
adifTemrfaukgwmutyatdqxhchacinfiuenws
haard cstimabs. One solution would have
younger s&o-slip faults cutting and precluding
fhha activiry on ok huts (Fig. SA). We con-
tend that this sohttioa is incompatible with the
.=kmd+!kgwdelic.Mdgwiogicsvidawzsup
porting pruicnt activity on the thrust system.
A secxmd solution would have the thrusts temti-
nateinthestrikeslipfitults@ig.SB~Tltis~
would dictate that the strike-slip faults cut down
dvclu& meMcireseismog~cNsf.aslsccmsid-
crcd in most current hazard asscssmmts. This
solution is plausible for the Oceanside thrust In
thissccnal+&oniytheareaoftheoFucnsidethluu
west of rhis Newport-Inglcwood-Rose Canyon
SWibS~p~lt~lamShOUldbCWllSidWWJ~a
pcaiblcearhqu&munxInconhst,thelocs
lionofIhc~&errtbqualaindkau4rhstlhc
Thirtymile ad rhnrr;c mends east af the San
Diego nough fault (Pig. 41 pnxluding the type of
bulc Unkgc shown in Ape SB.
Altaroacively, the IJMUSU may cut the strik
slip fault zones (Fig. SC). This solution would
pe.rmircoevalactivityonbolhtypesof~tsi3nd
would yield two in&pen&c 3ourccsfofcachof
m5 paifed tllnw and slrikAip systems. In the
finaIsccnario,rkIhruscandmiltaslipfaulomay
mage into a single structure at depth (Pig. 5D).
In this case, oblique slip on a deep fault would
partition into pure thrust and stike-slip motion
on the shallow faults. This linkage would imply
that the combined areas of the strikc4p and
thrust faults should be considcrcd to determine
maximunl potential rupture areas.
Figure 5. Potend8l contlgurr th~f~rnnat8dehilo*llp hult lntenxtlon (555 text for di5cusucn).
FROM : 9E GOOD FQX NO. : 7689419625 * ,-
If the oceanside thrust terminates in the
Newport-Ingkwood-Rose Canyon fault zone. as
dictated in soludon two. the thrust would have an
MO of 1890 km2. A rupcurc of this cntirc fault
would gwtwatc an earthquake of M, 7.3. In con-
traaifrheOaansdethnscalcndsrtrroug)lrhc
Newpon-lnglewood-Rosc Czmyon sysrcm then
nwoUldha~anaMof3180km2,wtlidrcauld
ptaluce an event of M, 7.5. An csti& s&n+
pit area of 25 16 km2 for rhc ‘Thirtymile Bank
thrust would genare similar (M, 7.4) earth-
quakes. If the Oceansi& &trust snd Nowporr-
In&wood-Rose Canyon system are linked as
dcsuibcd in the last solution (Fig. XI). that the
combined fault area (4393 km2) couid produce
M, 7.6 eadquakcs. This fault linka6c WCII&
would not a&a the magnitude estimate for the
Tbidymilo Bank thrust, becrruse the San Diego
trough fault is confined to sedimenls in the uppQ
2knlofcheausL
To aciulsm SYwago Ipcurr~ inwcvals for
these - soznatios, we use minimum slip
m&s derived hwn tunce uplilI (0.27 mmlyr for
the Oceanside thrust). and maximum slip rates
govmd by lhc olsorvcd geudclic shorting
(2.2 ndyr for ti Ocesnside thrust; 0.96 mm+r
IbrThhytn~k Bank thrust). On the bnris of these
rates. M, 7.1 evenly on the Oceanddr: thrust
limited to the cxtont of the San Joaquin Hills
waukl ocau evwy 6oLuKlo yr. M, 73 and 7.s
carthqUdkCSOflthCg#.W~6idCthN6tWOUld
cuzurevmy7%64OOand I l@-IXloOy~, re+o- - dwly. At,,, 7.4events on &eThirzymileBank thtur
wulcl &VC minimum repeat time6 of 2 100 yr.
Qi~th&L7.6~pourd linldngthe~
side thnur and Newport-In&won&Ro.se Canyon
fauits, we rrmy auxsi& the oblique-slip TIC that
is ru~lvcd on the thrust and suike-slip faults.
Onshote studies st San Diego Bay provide a slip
rate of 1.07 * 0.03 mmlyr for the Newpart-
Ingl-oso Canyon systmn (Rockwell d ~1..
1992). Tlsis skike slip oombined with rhe mage of
dipslip IX& on the oCeansi& thrust (0.27-2.2
mm/yr) y&s an oblique slip range of 1.19-2.91
mm@ on the hasis of these ranges or oblique slip
~tes.M.,7.6ea&qu&swouldoccuronavaa~
eVery 96o-wx) yr. ThCXC NpCUN SUUWiO6 pn-
clict wry htg~ tat infxquatb czitthqti stilar
to those document~I on other thrust fiults in
southan California (Rubin c( al., IYQB). Altema-
tidy. stress on the Oceans& snd Thirtymile
&nkblindtbrustscouldkr&a~insmallerbut
moltfiqutluevena.
This rr?rcuch WOE partially fun&l by Huwd Univasity and the Southern California Eurhquakkr Ctmu (SEC). Data were provided by lbxaco and
other industry sponsors. &EC is dnded by the
National Science Foundarion (NSF) Coopcm~ive
A-1 B~R-8920136 and U.S. Goolo&al SW. vcy Coopentive Agreements 14-06-0001-A0899 and I434-H()-WAGO/1716. We thaak M,Y. Siisr mnd R Bilotti for cnauibutioas to this work.
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RllainusA GEOUX;Y.owohaurY)