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| Titel |
The Use of Preliminary First-Motion Mechanisms and Later Moment Tensor Solutions for Rapid Tsunami Early-Warning Scenario Forecasting |
| VerfasserIn |
Fabrizio Bernardi, Anthony Lomax, Laura Scognamiglio, Alberto Michelini |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250134953
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| Publikation (Nr.) |
 EGU/EGU2016-15734.pdf |
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| Zusammenfassung |
| Following the ICG/NEAMTWS guidelines, the first tsunami warning messages for events
with magnitude M ≥ 5.5 are based only on seismic information, i.e., epicenter location,
hypocenter depth, and magnitude. However, in order to provide more informative,
real-time tsunami scenario forecasting, reliable faulting mechanism information is
needed.
Full-waveform, moment tensor solutions (MT) are typically available in 3-15 min after
event origin time for local/near-regional events and in 15-20 min for regional/teleseismic
events. Classic, P first-motion (FM) focal-mechanisms can be available within 3 min for
local/near-regional events and in 5-10 min for regional/teleseismic monitoring, depending on
station coverage.
We present first a robust, probabilistic, adaptive grid-search, FM inversion which,
combined with fast magnitude estimates such as Mwp, forms a preliminary mechanism
estimate and proxy for MT solutions. This MT proxy allows rapid event characterization and
analysis, such as estimation of shaking distribution and initial modeling of tsunami waves,
before a definitive, waveform MT is available.
Secondly, we present a near real-time MT inversion using waveforms band-pass filtered
from 0.01 − 0.02Hz band and a minimum of 6 min of signal after the event origin time for
events in the Mediterranean area. The solution is then updated every minute by adding 1 min
of signal and using the epicenter parameters available in real time from the automatic
localization provided by the Early-Est rapid earthquake location system. Tests on events since
2000 in the Mediterranean area indicate that reliable solutions are available within 7-15
minutes after event origin time.
Implementing both methodologies in our system allows the use of FM mechanisms for
rapid, preliminary tsunami forecasting within a few minutes after the earthquake occurrence,
and the use of a definitive MT solution a few minutes later for further forecasting
updates. |
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