tsunami warning michelini

Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009

Implementation of tsunamiearly warning using

earthquake rupture duration

Michelini A.1, Lauciani, L. 1, Lomax, A.21.Istituto Nazionale di Geofisica e Vulcanologia, via di vigna murata, 605, 00143 Roma, Italy,[email protected], [email protected]. ALomax Scientific, Mouans-Sartoux, France. [email protected]


Talk Structure

• Problem and earlier work

• P-wave duration - a good proxy to tsunami-genesis

• Alarm design and implementation

• Tsunami and non-tsunami alerts examples

• Conclusions


Problem and earlier work• Very first tsunami warning are critical for rapid

alerts and intervention.• P-waves can provide very first information on

earthquake size and tsunami potential• Mwp (Tsuboi et al., 1995) is the quickest

methodology at teleseismic distances todetermine earthquake size but– Accurate up to M~7.5-8– Underestimates M≥8 because it does not account for

multiple ruptures (i.e., later pulses on the waveformsindicative of source duration)


Problem and earlier work (2)• Duration Magnitudes (e.g., MED, Mwpd, mBc, Mhara)

take into account the source duration explicitlyand are calibrated against MCMT

• Theta (I.e., energy to moment ratio) proposed asindicator of tsunami earthquakes

• However, duration alone appears to be a reliableindicator of tsunami genesis


It - Tsunami importance based on waterheight, h, and 0-4 descriptive indices, i,of tsunami effects (deaths, injuries,damage, houses destroyed)

(NOAA/WDC Historical TsunamiDatabase (NGDC, 2008)

!

It = h+ ideaths + iinjuries + idamage + ihousesdestroyed

Tsunami importance, It, and Duration, T0, for identification of tsunami earthquakes

From Lomax and Michelini, 2009a


The duration-amplitude procedure produces rapidly anearthquake moment magnitude M

wpd from P-wave

recordings at teleseismic distances (30-90º)

Mwpd available within < 20 minutes after OT. For large earthquakes Mwpd (with moment scaling) matches Mw

CMT

typically within ±0.2 magnitude units. Mwpd does not exhibit saturation for the largest events. Mwpd equals or is better than other procedures for rapid moment

magnitude determination. Duration, T0, seems to be a robust indicator for tsunamigenic

earthquakes (i.e., T0 ≥ 50 s) The Duration-Exceedance proxy to T0, produces rapid

estimates (5-10 minutes) for tsunamigenic earthquakesFrom Lomax and Michelini, 2009a


Problem and earlier work (3)

• Tsunami very first warnings in theworld:– only Magnitude (Mwp) at US tsunami

centers (PTWC and WCATWC; T ~ 5-10’)– JMA/Japan warnings based on

Magnitude ( T ≤ 3’)– GITEWS/German-Indonesian based on

magnitudes (e.g., mB, mBc) alone ( T≤5’)


Tsunami Early Warningusing Duration - Exceedance

(Lom

ax &

Mic

helin

i, 20

09b;

http

://s3

.rm.in

gv.it

/D-E

.php


D-E

for

Sep

tem

ber

29

, 2

00

9 M

w=

8.2

Sam

oa


D-E

for

Sep

tem

ber

30

, 2

00

9 M

w=

7.7

Sum

atra


Summary

• Tsunami warning should rely on differenttools in order to issue alerts

• Duration-Exceedance, D-E, seems quitecomplementary to fast magnitudedeterminations used in all major centers

• D-E is visualized in real-time on the INGVseismic center video-wall

• The procedure is available athttp://s3.rm.ingv.it/D-E.php

tsunami warning michelini

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