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| Titel |
Tsunami early warning within 5 minutes |
| VerfasserIn |
A. Lomax, A. Michelini |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063312
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| Zusammenfassung |
| Tsunamis are most destructive at near to regional distances, arriving within 20-30 min after a
causative earthquake; effective early warning at these distances requires notification within 15
min or less. The size and impact of a tsunami also depend on sea floor displacement, which is
related to the length, L, width, W , mean slip, D, and depth, z, of the earthquake rupture.
Currently, the primary seismic discriminant for tsunami potential is the centroid-moment
tensor magnitude, MwCMT, representing the product LWD and estimated through an
indirect, inversion procedure. However, the obtained MwCMT and implied LWD value vary
with rupture depth, earth model and other factors, and is only available 20-30 min or more
after an earthquake. The use of more direct discriminants for tsunami potential could avoid
these problems and aid in effective early warning, especially for near to regional
distances.
Previously (http://alomax.net/posters/period-duration), we presented a direct procedure
for rapid assessment of earthquake tsunami potential using two, simple measures on P -wave
seismograms – the predominant period on velocity records, Td, and the likelihood, T50Ex,
that the high-frequency, apparent rupture-duration, T0, exceeds 50-55 sec. We have shown
that Td and T0 are related to the critical rupture parameters L, W , D and z, and that either of
the period-duration products TdT0 or TdT50Ex give more information on tsunami impact
and size than MwCMT, Mwp and other currently used discriminants. These results imply that
tsunami potential is not directly related to the product LWD from the “seismic” faulting
model, as is assumed with the use of the MwCMT discriminant. Instead, knowledge of
rupture length, L, and depth, z, alone can constrain well the tsunami potential of an
earthquake.
We introduce here special treatment of the signal around the S arrival at close stations, a
modified, real-time, Mwpd(RT) magnitude, and other procedures to allow early estimation of
event parameters and tsunami discriminants. We show that with real-time data currently
available in most regions of tsunami hazard, event locations, mb and Mwp magnitudes and
the direct, period-duration discriminant, TdT50Ex can be determined within 5 min after an
earthquake occurs, and T0, TdT0, and Mwpd(RT) within about 10 min. This processing is
implemented and running continuously in real-time within the Early-est earthquake monitor
at INGV-Rome (http://early-est.rm.ingv.it). The rapid availability of these measures can aid
in faster and more reliable tsunami early warning for near to regional distances. |
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