My 42 days in Paris 2018/8/3 Ando lab seminar Tomofumi Shimoda - PowerPoint PPT Presentation

My 42 days in Paris 2018/8/3 Ando lab seminar Tomofumi Shimoda

abstract • visited Paris from 6/15 to 7/29 • APC (Astroparticule et cosmologie) • IPGP (Institute de Physique du Globe de Paris) • mainly worked with Kevin Juhel about earthquake early warning (EEW) and partly with Donatella about Newtonian noise • main topic : how TOBA can contribude to EEW?

Earthquake early warning with gravity perturbation • gravity perturbation from deformed ground can be used for earthquake detection ! - + + - dilated compressed • gravity travels faster than p-wave • earlier detection especially for off-shore events • better magnitude estimation of large earthquake • seismometers can saturate

gravity perturbation induced by Tohoku-oki earthquake was detected • with broadband seismometers • Mw = 9.1

for smaller earthquakes : Gravity gradiometers • gravity change cannot be distinguished from background seismic vibration (equivalence principle) • gravity gradient change can be separated from it • Superconducting gravity gradiometer (SGG) • Torsion bar (TOBA, TorPeDO) • Atom interferometer (AI) SGG

research topics • gravity perturbation signal in different gravity gradient tensor components • which component is important for EEW? • how can different kind of detectors (SGG, TOBA, AI,..) contribute to EEW? ℎ ** ℎ *+ ℎ *, % = ' ( ℎ +* ℎ ++ ℎ +, ∇⨂ ⃗ ℎ ,* ℎ ,+ ℎ ,, • EEW with realistic sensitivity of TOBA • how is it different from model noise ( ∝ f -2 at low-f, flat at high-f) ? • what kind of design is preferred?

gr gravit ity signa ignal l in in dif different gr gradie dient te tensor component nts • 5 independent components • each detector measures different set of components • SGG : all components • TOBA : only horizontal components • (AI : only vertical components?) gravity gradient tensor horizontal vertical ℎ )) ℎ )* ℎ )+ ∇⨂∇# $ = & ' ℎ *) ℎ ** ℎ *+ ℎ +) ℎ +* ℎ ++ SGG h ij = h ji , h xx + h yy + h zz = 0 (in free space)

S/N with next-stage gravity gradiometers • sensitivity : ~ 10 -15 /rtHz @ 0.1 Hz (“model 2” in Kevin’s definition) • S/N at t= 10s, 15s → early detection • S/N at p-wave arrival time → parameter estimation • three-types of focal mechanism (mechanism of deformation) • stlike-slip, dip-slip(10 o ), dip-slip(20 o ) dip-slip strike-slip N Z E E 10 o , 20 o

S/N of horizontal 5 components N CC t = 10s after onset PP N distance (<300km) E epicenter azimuth E color=S/N vertical Mw = 7.5 Z contour : S/N = 3, 8 N ZZ assuming “model2” noise RZ (floor=1e-15, cutoff=0.1Hz) TZ 3-types of focal mechanism E N Z E E 10 o , 20 o dip-slip strike-slip

S/N of horizontal 5 components N CC t = 10s after onset PP and CC are large for strike-slip PP N distance (<300km) E only CC is large at 0 o ,90 o ,180 o ,270 o epicenter azimuth E color=S/N vertical Mw = 7.5 Z contour : S/N = 3, 8 N ZZ assuming “model2” noise RZ (floor=1e-15, cutoff=0.1Hz) TZ 3-types of focal mechanism E N Z E E 10 o , 20 o dip-slip strike-slip

S/N of horizontal 5 components N CC t = 10s after onset PP N distance (<300km) E PP and ZZ are large for dip-slip at 180 o epicenter azimuth E color=S/N vertical Mw = 7.5 Z contour : S/N = 3, 8 N ZZ assuming “model2” noise RZ (floor=1e-15, cutoff=0.1Hz) TZ 3-types of focal mechanism E N Z only RZ is large for dip-slip at 0 o E E 10 o , 20 o dip-slip strike-slip

S/N of horizontal 5 components N CC t = 10s after onset PP N distance (<300km) E epicenter azimuth E color=S/N vertical CC and TZ can compensate for S/N Mw = 7.5 at 90 o , 270 o Z contour : S/N = 3, 8 N ZZ assuming “model2” noise RZ (floor=1e-15, cutoff=0.1Hz) TZ 3-types of focal mechanism E N Z E E 10 o , 20 o dip-slip strike-slip

S/N of horizontal 5 components N CC t = 15s after onset PP N distance (<300km) E epicenter azimuth E color=S/N vertical Mw = 7.5 Z contour : S/N = 3, 8 N ZZ assuming “model2” noise RZ (floor=1e-15, cutoff=0.1Hz) TZ 3-types of focal mechanism E N Z E E 10 o , 20 o dip-slip strike-slip things are similar as t=10s

S/N of horizontal 5 components N CC t = p-wave arrival time PP N distance (<1000km) E epicenter azimuth E color=S/N vertical Mw = 7.5 Z contour : S/N = 100, 300 N ZZ assuming “model2” noise RZ (floor=1e-15, cutoff=0.1Hz) TZ 3-types of focal mechanism E N Z E E 10 o , 20 o dip-slip strike-slip

How about atom interferometers? (vertical components only?) total S/N of horizontal(TOBA) and all(SGG?) components S/N of horizontal components are ~70% of all components at 90 o ~ 270 o (where detectors will be usually placed) • t=10s Z N E horizontal E N E almost same S/N horizontal gradient is small at 0 o all

How about atom interferometers? (vertical components only?) total S/N of horizontal(TOBA) and all(SGG?) components • t=15s Z E horizontal N E all

How about atom interferometers? (vertical components only?) total S/N of horizontal(TOBA) and all(SGG?) components • t=p-wave Z E arrival time horizontal N E all RZ component grows

summary of gravity signal in different components (from a viewpoint of TOBA) • strike-slip : horizontal components are large • dip-slip (at azimuth = 180 o ) : horizontal components are ~70% of all components • dip-slip (at azimuth = 0 o ) : horizontal components are much smaller than all components • but usually azim.=0 o is the direction without land (detectors cannot be placed) • TOBA seems to have enough contribution to EEW

S/N S/N with realistic sensitivity pendulum rotation translation • resonant peaks (f0 ~ 8mHz, 40mHz, 0.6Hz) • ∝ f -2.5 dependence at f < 0.1Hz (thermal noise) • Newtonian noise (higher at f<0.1Hz) ∝ f -2 for model noise phase-III TOBA which has been used so far ∝ f -2.5 temperature NN model @ 100m depth instrument nosie infrasoundNN @ 100m depth

̃ basic S/N calculation process • matched filter #(%)' ' ℎ ∗ (%) ℎ ∗ (%) ! ̃ #(%) data signal noise ,% = ! ,% # . = ℎ . + 0(.) * + (%) * + (%) * + (%) whitened data whitened signal (template) data (signal+noise) convolve pre- (normalize) whitening template S/N (signal)

f 0 f effect of resonant peaks ∝ 1/Q notch filter • resonant peak -> apply notch filter for prewhitening • one resonant peak decreases S/N by 5~15% for Q=5 (Q of notch filter) assuming floor of peak is 10 times lower than noise floor noise floor + ~1/10 peak t=10s t=t p t=15s / (S/N without peaks) Q=10 (S/N with peaks) Q=5 Q=3 Q=50 Q=1 peak frequency (f0)

total effect of resonant peaks in TOBA design sensitivity • S/N with design sensitivity with peaks vs without peaks → notch + HPF → only HPF S/N S/N = 0.78 @ t = 10s 0.74 @ t = 15s 0.73 @ t = p-wave arrival resonant peaks in TOBA senitivity will decrease S/N by 22 ~ 27%

f -2.5 noise what kind of pre-whitening filter should be used? ( realtime f 2.5 filter is not available ) how much does S/N change compared with model noise? pre-whitened noise spectrum d e s i g n model noise s e n s i t i v i t y Mw = 8.5 distance = 300 km cross-mode S/N @ t=10s (x 1000) 3rd order HPF seems to be good pre-whitening S/N is ~2 times smaller than f -2 noise (model2)

f -2.5 noise what kind of pre-whitening filter should be used? ( realtime f 2.5 filter is not available ) how much does S/N change compared with model noise? pre-whitened noise spectrum d e s i g n model noise s e n s i t i v i t y Mw = 8.5 distance = 300 km cross-mode S/N @ t=t p (38.5s) 2nd order HPF seems to be good pre-whitening S/N is ~4 times smaller than f -2 noise (model2)

effect of NN temperature NN at 100m underground d e ( s is assumed ( maybe overestimated ) v i = g 1 n 0 s m e n / s s i , t d i v e i t p y t h w = i 1 t h 0 0 N m N ) Mw = 8.5 distance = 300 km cross-mode S/N @ t=t p (38.5s) S/N @ t=10s (x 1000) S/N is ~20 times smaller S/N is ~4000 times smaller than f -2 noise (model2) than f -2 noise (model2) small!

summary of realistic noise • one resonant peak will decrease S/N by 5~15% • total effect in TOBA is about 22~27% • f -2.5 thermal noise decreases S/N by ~2 times (t=10s) or by ~4 times (t=38s) than f -2 model noise • proper choice of pre-whitening filter depends on time • filter bank (multiple filtered signals to monitor) • or is there any better signal processing? • temperature NN degrades S/N very much • but temperature NN is maybe overestimated • more accurate calculation is necessary

what I’m interested in next • optimal signal processing • detectability of actual earthquakes with TOBA vs SGG • Alaska, Japan, California, etc... • temperature NN • focal mechanism estimation using 5 components • depth dependence

future upgrade possibility of TOBA • increasing in size is quite effective for EEW current design (without peaks) thermal noise ∝ ~(length) -2.5 shot noise ∝ ~(length) -2.5 ( laser power ∝ (mass), sensor response ∝ (length) )