23 August 2005 GEOSS Workshop

The Importance of International Seismic Networks for Tsunami Warning

Stuart A. Weinstein and Charles McCreery,

Richard Hagemeyer Pacific Tsunami Warning Center

Int. Seismic Networks Are Int. Seismic Networks Are Instrumental To The Tsunami Instrumental To The Tsunami

Warning SystemWarning System

• They allow the warning system to They allow the warning system to respond quickly to any potential respond quickly to any potential tsunamigenic earthquake occurring tsunamigenic earthquake occurring anywhere in the world.anywhere in the world.

• Contribute to the monitoring of “local” Contribute to the monitoring of “local” earthquakes.earthquakes.

Int. Seismic Networks Are Int. Seismic Networks Are Instrumental To The Tsunami Instrumental To The Tsunami

Warning SystemWarning System

• With a Satellite dish, PTWC has a first With a Satellite dish, PTWC has a first hop capability for several instruments.hop capability for several instruments.

• Currently PTWC, receives MIDW, RPN, Currently PTWC, receives MIDW, RPN, JOHN and WAKE, with XMAS, KANT, JOHN and WAKE, with XMAS, KANT, and TARA to be received in the near and TARA to be received in the near future.future.

Earthquake MonitoringEarthquake Monitoring

• Near Real Time Seismic Data From Near Real Time Seismic Data From Over 130 Broadband Stations.Over 130 Broadband Stations.

• Digital AlarmsDigital Alarms

• Automatic P-Wave Picking And Automatic P-Wave Picking And Association (GLASS, LOC_ATWC)Association (GLASS, LOC_ATWC)

• Magnitude Estimation: Mwp, Mm, MsMagnitude Estimation: Mwp, Mm, Ms

• Energy/Moment ratio Energy/Moment ratio ewman and ewman and Okal)Okal)

Broadband Seismometer Distribution

Vertical Component Only

Earthquake MonitoringEarthquake Monitoring

Mwp (Tsuboi et al.)Mwp (Tsuboi et al.)

• P-wave method (fast!) developed for deep P-wave method (fast!) developed for deep focus earthquakes found to work for shallow focus earthquakes found to work for shallow quakes.quakes.

• Less affected by Saturation Problem Less affected by Saturation Problem Associated with MAssociated with Ms.

• Can be fooled by complex rupture (Peru Can be fooled by complex rupture (Peru 2001).2001).

Mwp and Local Earthquakes

Mwp is limited by the trade off between the S-P travel time, and the source duration of the event.

Appears to work well at less than 5 degrees epicentral distance. Depending on the Mw and source length, Mwp provides an estimate that is low by an amount that decreases between 1-5 degrees epicentral distance.

Will automate it for local earthquakes.

84 Mwp Observations Within 5 Degrees of The Epicenter

Earthquake MonitoringEarthquake Monitoring

Mantle Magnitude (Okal and Talandier)Mantle Magnitude (Okal and Talandier)

• Long Period Rayleigh Waves that Sample the Long Period Rayleigh Waves that Sample the Upper Mantle (Mantle Waves).Upper Mantle (Mantle Waves).

• Overcomes Saturation Problem Associated Overcomes Saturation Problem Associated with Mwith Ms (Variable Period Magnitude).

• Less Effected By Rupture Slowness Or Less Effected By Rupture Slowness Or Complexity.Complexity.

• Quicker Than Computing CMT.Quicker Than Computing CMT.

Sampling by Max Mm

Sampling by Max of Mean Mm(T)

Harvard Mw

Mea

n R

esid

ual

Mea

n R

esid

ual

Mea

n R

esid

ual

Mea

n R

esid

ual

273s163s

51s

EARTHWORM ARCHITECTURE

ASSOCHYPS

MODULE

MAGNMODULE

IMPORTMODULE

PICKMODULE

EXPORTMODULE

SINGLE PLATFORM (NT OR SOLARIS)

LAN/WAN

LAN/WAN

WAVE-FORMRING

PICKRING

HYPSRING

• FREE AND AVAILABLE OFF OF THE WEBFREE AND AVAILABLE OFF OF THE WEB

HTTP://GLDBRICK.CR.USGS.GOVHTTP://GLDBRICK.CR.USGS.GOV

• OPEN SOURCE (FREE SOURCE CODE)OPEN SOURCE (FREE SOURCE CODE)

• LARGE AND GROWING USER COMMUNITYLARGE AND GROWING USER COMMUNITY

• USERS GROUPS FOR PROBLEMSUSERS GROUPS FOR PROBLEMS

• USERS GROUP FOR DEVELOPERSUSERS GROUP FOR DEVELOPERS

• ANSS STANDARD FOR US SEISMIC NETWORKSANSS STANDARD FOR US SEISMIC NETWORKS

IMPORTANT EARTHWORM FEATURES

ISSUE TIME OF PTWC INITIAL BULLETINS FOR TELESEISMS

0

10

20

30

40

50

60

70

80

90

100

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

EVENT TIME (YEAR)

MIN

UT

ES

SIN

CE

QU

AK

E

ISSUE TIME OF PTWC BULLETINS FOR HAWAII EVENTS

0

5

10

15

20

25

30

1994 1996 1998 2000 2002 2004 2006

EVENT TIME (YEAR)

EL

AP

SE

D M

INU

TE

S

Food for ThoughtFood for Thought

• Greater global network density. How dense?Greater global network density. How dense?

• Leverage off of the assets being devoted to Leverage off of the assets being devoted to DART systemsDART systems:

• Communications.Communications.

• Successor to the STS-1 very broadband Successor to the STS-1 very broadband seismometer.seismometer.

•Ocean Bottom Seismometers•Hydrophone Arrays