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| Titel |
The Christchurch Mw 6.3 earthquake: Rupture processes play a strong role in high Peak Ground Acceleration |
| VerfasserIn |
Bill Fry, Rafael Benites, Martin Reyners, Caroline Holden, Stephen Bannister, Anna Kaiser, Charles Williams, Matt Gerstenberger, John Ristau |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250058227
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| Zusammenfassung |
| On September 4, 2010, a surface-rupturing crustal earthquake (Mw 7.1) struck the Canterbury
Plains region in New Zealand’s South Island (Gledhill et al., 2011). The Canterbury Plains is
a region of relatively low seismicity in New Zealand and the structure that ruptured was
a previously unmapped fault. Compared to the average New Zealand aftershock
decay model, the aftershock sequence was relatively under-productive for the first 5
months.
On February 22, 2011, an Mw 6.3 aftershock occurred within kilometers of the city of
Christchurch. The earthquake resulted in about 3 meters of oblique-thrust slip on a south
dipping fault beneath a volcanic edifice that defines the southern extent of the city. It occurred
on a fault that experienced a slight (approx. 0.15 MPa) Coulomb failure stress increase as a
result of the Mw 7.1 event. Recorded peak ground acceleration (PGA) in the city exceeded
2g. Many of the poorly consolidated, low shear-wave velocity soils liquefied during the
shaking. The dense strong motion network recorded numerous sites that liquefied with less
than 0.5g peak horizontal accelerations. A number of factors contributed to the strong
shaking. However, most of the observations can be explained by the combination of a few
dominant source effects: 1) the high amount of energy released in the earthquake, 2) the
direction of energy release combined with the effects of high rupture velocity 3) a
trampoline effect, and 4) the proximity of the earthquake to the city. We will present
results of seismological observations and numerical simulations to support these
claims.
The dense data from the February 22nd earthquake has provided us with the valuable
opportunity to study the rupture process in fine detail and understand its relative effects
on recorded ground motions. To this aim, numerous ongoing studies aim to use
novel numerical techniques to better define the physics of the rupture, the effects of
wave propagation through a heterogeneous earth, and the near surface processes
that contribute to wave amplification in the frequency bands that affect the build
environment. |
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