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Using W phase for regional tsunami warning and rapid earthquake - - PowerPoint PPT Presentation

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Using W phase for regional tsunami warning and rapid earthquake hazard assessment Luis Rivera 1 Hiroo Kanamori 2 1 Strasbourg University, Institut de Physique du Globe 2 Seismological Laboratory, Caltech 2nd International Workshop on Earthquake

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Using W phase for regional tsunami warning and rapid earthquake hazard assessment

Luis Rivera1 Hiroo Kanamori2

1Strasbourg University, Institut de Physique du Globe 2Seismological Laboratory, Caltech

2nd International Workshop on Earthquake Early Warning Kyoto, April 21-22, DPRI, Kyoto University

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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W-phase Introduction

◮ We have recently developed a source inversion technique

based on the waveform modeling of W-phase.

◮ W-phase is a very long period (200s-1000s) phase arriving

right after the P .

◮ It was first recognized after the 1992 Nicaragua

earthquake.

◮ The inversion technique was originally devised to work for

large events (Mw>∼7.5) with teleseismic data and it provideas a VLP characterization of the source (e.g. Tsunami earthquakes).

◮ We explore here the possibility of an application with

regional data and with smaller magnitudes.

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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W-phase Example: Nicaragua, 1992

ANMO, ∆ = 28◦ PAS, ∆ = 36◦ ALE, ∆ = 71◦ Vertical traces - integrated once 1000 s

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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W-phase Example: Nicaragua, 1992

ANMO, ∆ = 28◦ PAS, ∆ = 36◦ ALE, ∆ = 71◦ Vertical traces - integrated once 1000 s

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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W-phase: Example: Nicaragua, 1992

ANMO, ∆ = 28◦ PAS, ∆ = 36◦ ALE, ∆ = 71◦ Vertical displacement ( µ ) Deconvolved + bp 200s-1000s 1000 s

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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W-phase: Example: Nicaragua, 1992

ANMO, ∆ = 28◦ PAS, ∆ = 36◦ ALE, ∆ = 71◦ Vertical displacement ( µ ) Deconvolved + bp 200s-1000s 1000 s

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Time window

W-phase time-window P, P + 15∆ s/◦

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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W-phase in the global context

10 20 30 40 50 60 70 80 90

] s e e r g e d [ ¢ e c n a t s i d

500 1000 1500 2000 2500

travel time [s]

P S ¢ 5 1 + P

W-phase Global scale

Definition

◮ Time window: P

, P+15∆

◮ Bandpass: .001 Hz - .005 Hz

Properties

◮ Fast group velocity: 4.5-9 km/s ◮ Fairly insensitive to:

◮ shallow lateral heterogeneities ◮ source second order details

◮ Avoid large amplitude surface

waves

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Source retrieval from W-phase Inversion: main features

◮ Time domain ◮ Point source (VLP data) ◮ Need a preliminary source location: PDE, JMA ◮ Library of precomputed Green’s functions ◮ Linear inversion –> Moment tensor components

◮ PDE (∆ < 50◦): t0 + 20 min ◮ Grid search (∆ < 90◦): t0 + 35 min

◮ RT implementation: β-test at NEIC-USGS, (Gavin Hayes)

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Example: global data Tokachi-Oki-2003 t0 + 20 min t0 + 35 min

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Regional data Extension to regional data and lower magnitudes

◮ Target: Mw >∼ 6.5 ◮ Data distribution:

◮ ∆ < 12◦ → 6 min. ◮ ∆ > 5◦: high gain data, nonlinearity.

◮ Modifications:

◮ Time window: (P

, P+15∆) inappropriate

◮ Frequency band: signal/noise ratio

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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W-phase time window

10 20 30 40 50 60 70 80 90

] s e e r g e d [ ¢ e c n a t s i d

500 1000 1500 2000 2500

travel time [s]

P ¢ 5 1 + P

Global scale

2 4 6 8 10 12 14 16

] s e e r g e d [ ¢ e c n a t s i d

100 200 300 400 500

travel time [s]

P s 2 1 ¤ 5 1 + P

n i m 6

Regional scale

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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W-phase time window

10 20 30 40 50 60 70 80 90

] s e e r g e d [ ¢ e c n a t s i d

500 1000 1500 2000 2500

travel time [s]

P ¢ 5 1 + P

Global scale

2 4 6 8 10 12 14 16

] s e e r g e d [ ¢ e c n a t s i d

100 200 300 400 500

travel time [s]

P s 2 1 ¤ 5 1 + P

n i m 6

Regional scale

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Extension to lower magnitudes Acceleration noise spectrum at MAJO

O A B C

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Extension to lower magnitudes Acceleration noise spectrum at MAJO

O A B C

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Extension to lower magnitudes Acceleration noise spectrum at MAJO

O A B C

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Data: Japanese broadband network (F-net) Events: Mjma > 6.7 2003-2008

130˚ 130˚ 135˚ 135˚ 140˚ 140˚ 145˚ 145˚ 25˚ 25˚ 30˚ 30˚ 35˚ 35˚ 40˚ 40˚ 45˚ 45˚

STS−2 STS−1

AMM AOG ASI FUJ FUK GJM HID HJO HRO HSS IMG INN ISI IYG IZH JIZ KIS KMT KMU KNM KNP KNY KSK KSN KSR KYK KZK KZS MMA NAA NOK NOP NRW NSK OKW ONS OSW SAG SBR SBT SGN SHR SIB SRN STM TAS TGA TGW TKD TKO TMC TMR TSA TSK TTO TYS UMJ URH WJM WTR YAS YMZ YSI YTY YZK

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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F-net, 2003-2008, Mjma > 6.7 (1/4)

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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F-net, 2003-2008, Mjma > 6.7 (2/4)

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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F-net, 2003-2008, Mjma > 6.7 (3/4)

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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F-net, 2003-2008, Mjma > 6.7 (4/4)

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Regional W phase focal mechanisms (t0 + 6min)

130˚ 130˚ 135˚ 135˚ 140˚ 140˚ 145˚ 145˚ 150˚ 150˚ 20˚ 20˚ 25˚ 25˚ 30˚ 30˚ 35˚ 35˚ 40˚ 40˚ 45˚ 45˚

STS−2 STS−1

052603A 090504A 090504D 092503C 092503K 102304D 103103A 112804I 120604A 200501190611A 200503200153A 200508160246A 200511142138A 200610232117A 200703250041A 200707160113A 200709281338A 200805071645A 200806132343A 200807190239A 200807231526A 200809110020A 092503K 200709281338A

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Regional W-phase, example of fit: 2008 Iwate

200806132343A ( 0.002 Hz - 0.010 Hz, n = 4, W )

KZS KNP TGA NOP YAS NMR WTR NKG SHR ABU HJO YZK KIS NOK SAG AOG KMT ISI NRW YSI UMJ OKW TGW NSK TSA YTY INN SBR TMC IZH TKO STM SIB TAS FUK OSW

  • 0.329
  • 0.282
  • 0.235
  • 0.188
  • 0.141
  • 0.094
  • 0.047

0.000 0.047 0.094 mm 5000 sec

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Moment Magnitude: gCMT - W-phase

6.0 6.5 7.0 7.5 8.0 8.5

gCMT Mw

6.0 6.5 7.0 7.5 8.0 8.5

W phase Mw

  • 0.1

+0.1

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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2003 Tokachi-oki: depth effect

H = 45km δ = 29◦ Mw = 8.02 H = 28km δ = 14◦ Mw = 8.15 HVD(H = 28km) δ = 11◦ Mw = 8.26

  • L. Rivera, H. Kanamori

W phase source inversion, regional application

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Conclusions

◮ We use F-net data in the range (5◦ < ∆ < 12◦) ◮ Time window: tP, tP + 180s ◮ Variable frequency band:

(.00167Hz − .005Hz) → (.005Hz.010Hz)

◮ Moment tensor solution available at t0 + 6min ◮ Can be done completely automatic and ◮ Provide a solution 6 min after the origin time.

  • L. Rivera, H. Kanamori

W phase source inversion, regional application