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 Early Warning Kyoto, April 21-22, DPRI, Kyoto University L. Rivera, H. Kanamori W phase source inversion, regional application
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
W-phase Example: Nicaragua, 1992 Vertical traces - integrated once ANMO, ∆ = 28 ◦ PAS, ∆ = 36 ◦ ALE, ∆ = 71 ◦ 1000 s L. Rivera, H. Kanamori W phase source inversion, regional application
W-phase Example: Nicaragua, 1992 Vertical traces - integrated once ANMO, ∆ = 28 ◦ PAS, ∆ = 36 ◦ ALE, ∆ = 71 ◦ 1000 s L. Rivera, H. Kanamori W phase source inversion, regional application
W-phase: Example: Nicaragua, 1992 Deconvolved + bp 200s-1000s ANMO, ∆ = 28 ◦ Vertical displacement ( µ ) PAS, ∆ = 36 ◦ ALE, ∆ = 71 ◦ 1000 s L. Rivera, H. Kanamori W phase source inversion, regional application
W-phase: Example: Nicaragua, 1992 Deconvolved + bp 200s-1000s ANMO, ∆ = 28 ◦ Vertical displacement ( µ ) PAS, ∆ = 36 ◦ ALE, ∆ = 71 ◦ 1000 s L. Rivera, H. Kanamori W phase source inversion, regional application
Time window W-phase time-window P , P + 15 ∆ s / ◦ L. Rivera, H. Kanamori W phase source inversion, regional application
W-phase in the global context Global scale Definition 2500 ◮ Time window: P , P+15 ∆ ◮ Bandpass: .001 Hz - .005 Hz 2000 Properties travel time [s] S 1500 ◮ Fast group velocity: 4.5-9 km/s W-phase P + 1 5 ¢ ◮ Fairly insensitive to: 1000 ◮ shallow lateral heterogeneities ◮ source second order details 500 P ◮ Avoid large amplitude surface 0 0 10 20 30 40 50 60 70 80 90 waves d i s t a n c e ¢ [ d e g r e e s ] L. Rivera, H. Kanamori W phase source inversion, regional application
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 ◦ ): t 0 + 20 min ◮ Grid search ( ∆ < 90 ◦ ): t 0 + 35 min ◮ RT implementation: β -test at NEIC-USGS, (Gavin Hayes) L. Rivera, H. Kanamori W phase source inversion, regional application
Example: global data Tokachi-Oki-2003 t 0 + 20 min t 0 + 35 min L. Rivera, H. Kanamori W phase source inversion, regional application
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
W-phase time window Regional scale Global scale 2500 500 2000 400 P + 1 5 ¤ 1 2 s 6 m i n travel time [s] travel time [s] 1500 300 P + 1 5 ¢ 1000 200 P 500 100 P 0 0 0 10 20 30 40 50 60 70 80 90 2 4 6 8 10 12 14 16 d i s t a n c e ¢ [ d e g r e e s ] d i s t a n c e ¢ [ d e g r e e s ] L. Rivera, H. Kanamori W phase source inversion, regional application
W-phase time window Regional scale Global scale 2500 500 2000 400 P + 1 5 ¤ 1 2 s 6 m i n travel time [s] travel time [s] 1500 300 P + 1 5 ¢ 1000 200 P 500 100 P 0 0 0 10 20 30 40 50 60 70 80 90 2 4 6 8 10 12 14 16 d i s t a n c e ¢ [ d e g r e e s ] d i s t a n c e ¢ [ d e g r e e s ] L. Rivera, H. Kanamori W phase source inversion, regional application
Extension to lower magnitudes Acceleration noise spectrum at MAJO O A B C L. Rivera, H. Kanamori W phase source inversion, regional application
Extension to lower magnitudes Acceleration noise spectrum at MAJO O A B C L. Rivera, H. Kanamori W phase source inversion, regional application
Extension to lower magnitudes Acceleration noise spectrum at MAJO O A B C L. Rivera, H. Kanamori W phase source inversion, regional application
130˚ 135˚ 140˚ 145˚ 45˚ 45˚ NOP SHR KNP HSS URH KSR HID IMG KMU MMA TMR IYG GJM 40˚ 40˚ TYS KSN KSK SBT WJM KZK HRO Data: YMZ ASI SAG SRN TSK ONS TTO KNM Japanese broadband YAS SGN YSI TGA NAA FUJ YZK KNY JIZ NRW 35˚ 35˚ NSK WTR YTY KZS network (F-net) IZH NOK TGW ISI KIS OKW KMT UMJ SBR INN TSA HJO STM TKD Events: FUK TMC AOG SIB TKO M jma > 6 . 7 TAS KYK 2003-2008 30˚ 30˚ AMM OSW STS−1 25˚ 25˚ STS−2 130˚ 135˚ 140˚ 145˚ L. Rivera, H. Kanamori W phase source inversion, regional application
F-net, 2003-2008, M jma > 6.7 (1/4) L. Rivera, H. Kanamori W phase source inversion, regional application
F-net, 2003-2008, M jma > 6.7 (2/4) L. Rivera, H. Kanamori W phase source inversion, regional application
F-net, 2003-2008, M jma > 6.7 (3/4) L. Rivera, H. Kanamori W phase source inversion, regional application
F-net, 2003-2008, M jma > 6.7 (4/4) L. Rivera, H. Kanamori W phase source inversion, regional application
Regional W phase focal mechanisms ( t 0 + 6 min ) 130˚ 135˚ 140˚ 145˚ 150˚ 112804I 120604A 45˚ 45˚ 200809110020A 200806132343A 092503C 102304D 092503K 092503K 200707160113A 40˚ 40˚ 200703250041A 200807231526A 200511142138A 200503200153A 052603A 35˚ 35˚ 200508160246A 103103A 090504A 090504D 200807190239A 30˚ 30˚ 200805071645A 200501190611A 200610232117A STS−1 200709281338A 200709281338A 25˚ STS−2 25˚ 20˚ 20˚ 130˚ 135˚ 140˚ 145˚ 150˚ L. Rivera, H. Kanamori W phase source inversion, regional application
Regional W-phase, example of fit: 2008 Iwate 200806132343A ( 0.002 Hz - 0.010 Hz, n = 4, W ) 0.094 NMR WTR KMT NRW OKW TGW TMC OSW KZS KNP TGA NOP YAS NKG SHR ABU HJO YZK NOK SAG AOG UMJ NSK TSA YTY INN SBR TKO STM TAS FUK KIS YSI IZH SIB ISI 0.047 0.000 -0.047 -0.094 mm -0.141 -0.188 -0.235 -0.282 -0.329 0 5000 sec L. Rivera, H. Kanamori W phase source inversion, regional application
Moment Magnitude: gCMT - W-phase 8.5 +0.1 - 0.1 8.0 7.5 W phase Mw 7.0 6.5 6.0 6.0 6.5 7.0 7.5 8.0 8.5 gCMT Mw L. Rivera, H. Kanamori W phase source inversion, regional application
2003 Tokachi-oki: depth effect HVD ( H = 28 km ) H = 45 km H = 28 km δ = 29 ◦ δ = 14 ◦ δ = 11 ◦ M w = 8 . 02 M w = 8 . 15 M w = 8 . 26 L. Rivera, H. Kanamori W phase source inversion, regional application
Conclusions ◮ We use F-net data in the range (5 ◦ < ∆ < 12 ◦ ) ◮ Time window: t P , t P + 180 s ◮ Variable frequency band: ( . 00167 Hz − . 005 Hz ) → ( . 005 Hz . 010 Hz ) ◮ Moment tensor solution available at t 0 + 6 min ◮ 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
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