Download - 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]
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
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
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
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)
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
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
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
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
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
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
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
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’)
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
Tsunami Early Warningusing Duration - Exceedance
(Lom
ax &
Mic
helin
i, 20
09b;
http
://s3
.rm.in
gv.it
/D-E
.php
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
D-E
for
Sep
tem
ber
29
, 2
00
9 M
w=
8.2
Sam
oa
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
D-E
for
Sep
tem
ber
30
, 2
00
9 M
w=
7.7
Sum
atra
Convenzione INGV-DPC 2007-2009First Annual Meeting - Rome 19-21 October 2009
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