1
Nume ical models o Cascadia ea hquake scena ios cons ained by
ene gy budge analyses
LINDSAY GROSS, San Jose S a e Uni e si y
Twin Men o 1: Elizabe h Madden, San Jose S a e Uni e si y
Twin Men o 2: Amanda Thomas, Uni e si y o Cali o nia Da is
ABSTRACT
Mega h us subduc ion zone ea hquakes a e a deadly haza d ha many a eas, including he No h
Ame ican Paci ic Coas , ace. Unde s anding he mechanics behind hese e en s is pe inen o assessing he
possible impac on local communi ies. Mega h us ea hquake ene gy budge s, which a e a sum o he ene gy
componen s o ic ional, up u e, and adia ed ene gy, a e no pe ec ly unde s ood. High-pe o mance
compu a ional models, using so wa e, such as SeisSol, a e one way o isualize he up u es and unde s and he
dissipa ion o ene gy du ing hem. We e- un a sui e o models om Madden e . al (2022) o he Suma a-
Andaman ea hquake o 2004 o es ima e he ene gy budge o ha e en . We compa e he model indings o
obse a ions om he 2004 ea hquake o see how well he model i s he ene gy obse a ions. We will
cons uc a model o a po en ial mega h us e en a he Cascadia subduc ion zone in he Paci ic No hwes and
compa e i s ene gy budge o ha o he 2004 Suma a ea hquake. Ou indings will allow us o be e
unde s and mega h us ea hquake ene gy budge s, imp o e ou models o accu a ely ep esen hem, and be e
unde s and he na u e o he seismic haza d millions o people ace li ing on he Paci ic No hwes coas , whe e
a mega h us ea hquake will ine i ably s ike.
INTRODUCTION
Ea hquakes a e one o he g ea es na u al dange s o mankind (Kamme e al., 2024), especially in
coun ies ha ha e no es ablished building egula ions o comba dea h and inju y om mega h us
ea hquakes. Mega h us aul s a e subduc ion zone aul s ha cause some o he mos des uc i e ea hquakes
and can c ea e damaging sunamis. Take Indonesia, o example: in 2004, a Mw 9.1 ea hquake s uck he coas ,
whe e he Indo-Aus alian pla e subduc s unde he Eu asian pla e, in a mega h us e en . The e we e o e $13
billion in damages, and hund eds o housands o ci ilians we e killed. The Uni ed S a es Geological Su ey
(2019) oughly es ima es he ene gy p oduced om his e en a 2.00 x 1018 Joules, which is compa able o he
s eng h o 23,000 Hi oshima bombs. This ea hquake had a up u e leng h o oughly 800 miles, compa able o
he leng h o Cali o nia, and las ed o 8-10 minu es. No h Ame ica has i s own mega h us seismic haza d: he
Cascadia Subduc ion Zone (CSZ). Ou p ojec aims o analyze he up u e and ene gy budge o he 2004
Suma a e en , as well as compa e i o ha o a likely mega h us e en on he CSZ.
The only majo subduc ion zone in he Uni ed S a es is loca ed on he Wes Coas and uns om Canada
o No he n Cali o nia. He e, he Juan de Fuca and Explo e pla es subduc unde he No h Ame ican pla e.
O egon’s Depa men o Eme gency Managemen ells us he e ha e been no majo ea hquakes he e since
1700. Unde s anding po en ial ea hquakes using modeling is impo an when i comes o haza d mi iga ion o
Sho Con ibu ions
CRESCENT
Volume 1
Oc obe 2025
Doi: 10.5281/zenodo.17280397
Twinning
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a eas whe e he esiden s do no expe ience majo
ea hquakes o en, and s udying he ene gy budge can
imp o e hese models.
We will model he Cascadia subduc ion zone and
un di e en scena ios wi h a ying po e- luid p essu es,
wi h espec o he 2004 Suma a-Andaman ea hquake, and
compa e ou esul s o ha o he Suma a models om
Madden e . al (2022) and obse a ions om ha 2004
e en . Wi h hese models, we a e going o ge esul s o
adia ed ene gy, seismic momen , s a ic and o al ic ional
wo k. Wi h hese esul s, we will be able o deduce how he
ene gy is dis ibu ed amongs he ene gy budge
componen s in a Cascadia e en , simila o Suma a.
Figu e 1. Image o 2004 Suma a-Andaman ea hquake up u e
om Shea e , P., & Bü gmann, R. (2010).
BACKGROUND
Subduc ion zones a e a ype o con e gen pla e bounda y ha occu s when one ec onic pla e subduc s,
o slides unde , ano he pla e. Mega h us ea hquakes and sunamis p esen signi ican haza ds a subduc ion
zones. The subduc ion zone in he Uni ed S a es is Cascadia, whe e he Juan de Fuca and Explo e pla es
subduc benea h he No h Ame ican pla e, c ea ing a dange ous zone ha s e ches om Canada o No he n
Cali o nia. Many majo No h Ame ican ci ies lie along he Cascadia Subduc ion Zone, including Sea le,
Po land, Eugene, Eu eka, and Vancou e . Since he e is no la ge ea hquake eco ded he e since 1700, he
chances o he aul slipping soon a e ele a ed, and could c ea e cos ly consequences. An ocean away is a
simila subduc ion zone, Suma a, whe e he Indo-Aus alian pla e subduc s unde he Eu asian pla e. In 2004, a
de as a ing Mw 9.1 mega h us ea hquake, wi h a up u e leng h o 800 miles, occu ed o he coas o
Indonesia, killing a qua e o a million people, displacing almos 2 million o he s, cos ing a o al o $13 billion,
and c ea ing a sunami so powe ul i eached Eas e n A ica and was obse ed a A lan ic and Paci ic wa e
s a ions, he Na ional Oceanic and A mosphe ic Adminis a ion (2023) epo s.
This ea hquake, called he Suma a-Andaman ea hquake, has been s udied by many seismologis s and
geologis s including D . Hi oo Kanamo i and D . Elizabe h Madden. Bo h Kanamo i (2006) and Madden e al.
(2022) c ea ed models o analyze he up u e and espec i e ene gy om his e en . Kanamo i aimed o es ima e
he adia ed ene gy using a ini e sou ce model wi h a ying equency bands and a i ed a an es ima e o
3.0E+17 J adia ed. He also ound ha he adia ion e iciency (0.16) and ene gy momen a io (0.46 x 10-5)
es ima ed om his adia ed ene gy, a e smalle han hose o simila magni ude ea hquakes (Kanamo i, 2006).
Madden e al. (2022) used supe compu e s o model he Suma a-Andaman ea hquake, wi h a ying luid
p essu es in each o he six scena ios. In hese scena ios, he alues o a e age slip, peak slip a e, s a ic shea
s ess, and magni ude we e epo ed om he ou pu o he models (Madden e al., 2022). New models o
Cascadia will e eal he simila i ies and di e ences in hese epo ed alues and allow us o be e unde s and
ea hquake beha io .
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Ea hquake ene gy budge s
a e no pe ec ly unde s ood, and a e
one o he main ocuses o ou
p ojec . To al ene gy is he sum o
ic ional ene gy, ac u e ene gy,
and adia ed ene gy. F ic ional
ene gy is he ene gy eleased and
con e ed o hea om he aul s’
ic ion om sliding. F ac u e ene gy
is he o al ene gy equi ed o
p opaga e up u e along a aul , and
adia ed ene gy is ene gy eleased in
he o m o seismic wa es. Figu e 2
shows he componen s o he ene gy
budge equa ion in e ms o s ess
and displacemen . Using ene gy
budge equa ions om Ma and
A chule a (2006) and Co ey e al.
(2023), we compa e ou model
esul s wi h obse a ions o he e en
o es ou model’s alidi y, and
be e unde s and ea hquake
beha io .
METHODS
To un he models, we use he San Diego’s Supe Compu ing Cen e ’s (SDSC) pla o m Expanse. On
Expanse, we use SeisSol, a high-pe o mance compu a ional ool op imized o ea hquake dynamics. To
unde s and he Suma a ene gy ou pu , we e- un he model om Madden e al. (2022), speci ically ocusing on
scena ios 3 h ough 6, which ha e high (93%) o e y high (97%) po e- luid p essu es (P ). These models a e
s uc u ally he same as he 2004 e en , bu a y in P , scena ios 3 and 5 bo h ha e high P , while 4 and 6 ha e
e y high P . Scena io 6 is he p e e ed model since i is he mos simila o he 2004 e en , and is he basis o
he compa isons wi h obse a ions. We use he ene gy ou pu ha SeisSol p oduces and calcula e o he ene gy
budge componen s, such as adia ed ene gy, and also he ene gy momen a io. We use equa ions o ic ional
and ac u e ene gy om Co ey e al. (2023), o back o he en elope calcula ions. To al ene gy is comp ised
o many di e en componen s ha make up he ene gy budge . Speci ically, o al ene gy is equaled o he sum
o ac u e ene gy, adia ed ene gy, and ic ional ene gy. SeisSol calcula es o al and s a ic wo k using
equa ions om Ma & A chule a (2006), inding adia ed ene gy o be equal o o al wo k minus s a ic wo k.
F ic ional ene gy is ep esen ed by ini ial shea s ess imes a e age displacemen . F ac u e ene gy is ound o
be hal o shea s ess d op imes he c i ical displacemen , which is he h eshold o aul ailu e.
Fo he Cascadia models, we will use pa ame e s simila o he Suma a models, bu wi h ce ain
condi ions ailo ed o he Cascadia aul , especially when i comes o he geology, and aul shape which will be
e lec ed in he model’s mesh. We wan o examine how a mega h us ea hquake a he Cascadia subduc ion
zone is simila o and di e s om ha o he 2004 Suma a-Andaman ea hquake, by examining he ou pu o
ene gy componen s om he wo models.
Figu e 2. Componen s o he ene gy budge equa ion: ic ional ene gy, ac u e
ene gy, and up u e ene gy. S ess is ep esen ed on he y-axis and displacemen on
he x-axis, om Co ey e al. (2023) (no o scale).
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RESULTS
SeisSol p o ides us wi h alues o s a ic wo k being 3.67E+18 J, o al wo k 4.23E+18 J, and adia ed
ene gy o equal 5.60E+17. Ou model also p o ides us wi h a seismic momen o 4.93E+22 J. As we do no
ha e any obse a ions o ac u e ene gy o ic ional ene gy. We compa e he sum o ac u e and ic ional
ene gy o s a ic wo k o es he alidi y o hese indings. Using he equa ions o ic ional ene gy and ac u e
ene gy om Co ey e al. (2023) o calcula e s a ic wo k, we ge ha he sum is 2.12E+07 J/m2, and s a ic wo k
pe squa e me e , is ound o be 5.83E+07 J/m2.
Table 1
Ene gy Componen
Obse ed (Kanamo i 2006)
Model
Radia ed Ene gy
1.38E+17 J
5.60E+17 J
Seismic Momen
6.68E+22 J
4.93E+22 J
Compa ison o ene gy budge componen s om Madden e al. (2022) model o Kanamo i (2006) obse a ions.
Table 2
S a ic Wo k pe Squa e Me e
EF + EG
5.83E+07 J/m^2
2.12E+07 J/m^2
Compa ison o s a ic wo k pe squa e me e , calcula ed om Madden e al. (2022) model ou pu , wi h he sum o ic ional and
ac u e ene gy (s a ic wo k).
DISCUSSION
Kanamo i (2006) is he main sou ce o ou obse ed alues ha we compa e ou model indings o. He
ound adia ed ene gy o be 1.38E+17 J. Ou model indings o 5.60E+17 o adia ed ene gy a e la ge han
Kanamo i (2006) indings o 3.0E+17 J adia ed. Seismic momen , on he o he hand, is obse ed o be
6.68E+22 J, which is la ge han ou model’s inding o 4.93E+22 J, as shown in Table 1. Wi h s a ic wo k pe
squa e me e and he sum o ac u e and ic ional ene gy, we see in Table 2, ha he wo alues a e in he igh
o de o magni ude, bu he sum is hal o he s a ic wo k. One explana ion o his is ha he back o he
en elope calcula ions we do a e oo simpli ied. We use a e ages o calcula e hese alues, while he equa ions
SeisSol uses om Ma & A chule a (2003) in eg a e o e he en i e aul , which may lead o he di e ences in
alues.
CONCLUSION
This p ojec is only sc aping he su ace o he analyses in o subduc ion zone ea hquake ene gy budge s.
Th ough he CRESCENT Seed G an and he San Jose S a e Uni e si y’s RSCA ellowship, we plan o
con inue his wo k and un simula ions o mega h us ea hquake scena ios in he Cascadia egion. We will
compa e he Cascadia model ou pu wi h ha om Suma a, allowing us o highligh po en ial ea hquake
scena ios and be e cons ain ou models o highligh po en ial haza d.
ACKNOWLEDGEMENT
This ma e ial is based upon wo k suppo ed by CRESCENT and he Na ional Science Founda ion Co-ope a i e
ag eemen #2225286. I would like o hank my men o D . Elizabe h Madden o all he suppo , guidance, and
eedback o e he pas yea , as well as being he one o in oduce me o scien i ic esea ch. I would also like o
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hank D . Amanda Thomas and he g oup o esea che s o hei guidance du ing he summe , and he
oppo uni y o do ield wo k a M . Rainie . Thank you o my CRESCENT winning coho , and p ojec di ec o
Shannon Fasola o he suppo h ough he oad bumps I expe ienced. A special hank you o Ri wik Pa il o
helping wi h he ene gy plo s on Expanse. And inally, I would like o hank my amily and iends o hei
con inued suppo h ough he du a ion o his p ojec .
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