Ambient seismic noise interferometry using rotational ground motion Céline Hadziioannou, Paul Neumann University of Hamburg, Germany Joachim assermann, Heiner !gel "udwig$%aximilians-University %unich, Germany Ulrich 'chreiber Technical University %unich, Germany … and the *+%Y team - .ideo recording of presentation here 0or scan the QR code23 Note4 most references are lin5s to the publications2 - Ne# sensing technologies 6 beyond conventional seismic translation measurements- Here: rotational ground motion Can we detect the wea5 ocean-generated seismic noise with the e&isting rotation sensors7 Can we /erform ambient noise interferometry #ith rotational motions7 !nterferometry with rotations 8 strain4 Paitz, Sager, 9ichtner: GJI 2<=> +bserving rotations4 Ring lasers G meter Observatory instruments: Ring lasers Ring lasers o?er a point measurement of rotational ground motion @ RLAS in Wettzell Germany: vertical com/onent rotation =; meter most sensitive worldwide co-located seismometer4 A( @ RO"Y near Munich Germany: RLAS Brst 3-com/onent rotation RO"# co-located seismometer4 9U* D*+%,4 A Multi-Component Ring Laser for Geodesy and Geophysics”, earthAr&iv D"ord of the Rings”, Science, 2<=F +bserving rotations4 Ring lasers Observatory instruments: Ring lasers @ RLAS in Wettzell Germany: vertical com/onent rotation most sensitive worldwide co-located seismometer4 A( @ RO"Y near Munich Germany: Brst 3-com/onent rotation co-located seismometer4 9U* Here: focus on vertical component: 'H- and Love waves %an we pic' up the ocean microseism? PP'L for seismometer vs- ring laser Translations: Seismometer Rotations: RLAS Laser Primary Secondary 'econdary %icroseism %icroseism %icroseism !nstrument sensitivity limit H<-<J$<-= Hz] H<-=$<-; Hz] 0before 2<=K3 RLAS RO"# %an we pic' up the ocean microseism? PP'L for seismometer vs- ring laser Translations: Seismometer Rotations: RLAS Laser Primary Secondary Primary 'econdary %icroseism %icroseism %icroseism %icroseism !nstrument sensitivity limit H<-<J$<-= Hz] H<-=$<-; Hz] 0after 2<=K3 RLAS RO"# *"A' ring laser in ettzell im/roved in 20=F Here4 Primary microseism detected in January 20=K !s it really the primary microseism7 Combining Rotation and Translation 3C Translation @ 3C Rotation Ground acceleration *otation rate Seismometer Rotation sensor @ *otation rate and acceleration should be in phase @ am/litudes scaled by t&o times the horizontal phase velocity) *hase velocity → using single measurement of 6C in phase + waveforms similar → can Bnd source direction %an we pic' up the ocean microseism? PP'L for seismometer vs- ring laser Rotations: RLAS Laser Primary 'econdary %icroseism %icroseism !nstrument sensitivity limit 0after 2<=K3 RLAS RO"# *"A' ring laser in ettzell im/roved in 20=F Here4 Primary microseism detected in January 20=K !s it really the primary microseism7 !s it coming from a speci,c direction? 'ingle$point bac'azimuth determination *otation rate and acceleration should be in phase in phase → waveforms similar + can find source direction *rimary microseism: 0-<5 N 0-= Hz h t u m i z RLAS a ' RO"# c a b -. hours A//roach described: Hadziioannou et al- ;<=;, Jo' Sensitivity of ring laser sufficiently im/roved to detect primary microseism Rotations: RLAS Laser Primary Secondary Coherent #avefield coming from North4 %icroseism / %icroseism 0consistent #ith e-g. Juretze5 8 Hadziioannou, GJI 2<=F3 *rimary microseism detected/ <-<J N 0-= Hz !nstrument sensitivity limit h t 0after ;<=K3 u m i z RLAS a ' RO"# c a b -. hours A//roach described: Hadziioannou et al. 20=;, Jo' - Ne# sensing technologies 6 beyond conventional seismic translation measurements- Here: rotational ground motion Can we detect the wea5 ocean-generated seismic noise with the e&isting rotation sensors7 Yes/ + Sensitivity of ring laser sufficiently im/roved to detect primary microseism Can we /erform ambient noise interferometry #ith rotational motions7 Ambient noise interferometry 9rom seismic noise to useful signal4 noise interferometry 1deal case: ● noise sources illuminating medium from all sides ● Average recorded noise over long time ● Turns seismometers into 2virtual sources’ A correlation 0 time N time + 4oes this work for rotational motion( Noise *eceiver source ant to know more? D(utorial on seismic interferometryE, apenaar et al, Geo/hysics 20=< Seismic noise interferometry with rotational ground motion? h t u m i z a ' c a b 5 hours RLAS RO"# .)- 6 0)5 Hz Secondary microseism available on both sensors Dominant source to#ard N consistent #ith beamforming D here do ocean microseisms come from7E Juretze5 8 Hadziioannou, JGR ;<=M Seismic noise interferometry with rotational ground motion? Need long enough stacking time: 6 P one year of noise, <=-<=-;<=K – <=-=;-;<=K Ambient noise from the secondary microseism available on both sensors: 6 filter between <-= – <-2 Hz RLAS RO"# Seismic noise interferometry with rotational ground motion? "ove waves RLAS Ambient noise interferometry: RO"# @ blac': bet#een two seismometers near *+MY and *"A' 0QclassicR case) Seismic noise interferometry with rotational ground motion? "ove waves RLAS Ambient noise interferometry: RO"# @ blac'4 between t&o seismometers near *+%Y and *"AS 0Qclassic’ case) @ red4 between the t&o ring lasers *+MY and *"A' Seismic noise interferometry with rotational ground motion? "ove waves RLAS Ambient noise interferometry: RO"# @ blac'4 between t&o seismometers near *+%Y and *"AS 0Qclassic’ case) @ red4 between the t&o ring lasers *+MY and *"A' @ &aveform of vertical rotation rate 0red3 should be similar to the transverse acceleration 0blac'3 @ #ith long enough stac'ing time, the #aveforms match2 Seismic noise interferometry with rotational ground motion? "ove waves RLAS Ambient noise interferometry: RO"# @ blac': between t&o seismometers near *+%, and *"A' 0Qclassic’ case3 @ red4 between the t&o ring lasers *+%Y and *"AS @ blue: synthetic signal for =D model 0P*A%3 source at *"A' recorded at *+%, 'eismic noise analysis with rotational ground motion Ocean-generated noise can be detected at two ring laser sites: beside the secondary microseism, no# also the primary microseism + push limit towards weak motions *roof of concept: first case of 2rotational3 noise interferometry using ocean-generated noise recorded at t#o ring lasers + towards noise interferometry of 6-component displacement data. !eneral: + ambient noise applications with rotational motion What3s ne8t( 'lides 8 more4 celine-hadzii-com What does the future bring? 1nnovative $raining net&or' funded by <: H2.5. programme Started march 5.5-) integrate emerging ground$motion sensing technology into seismological /ractice A?ect of small-scale structure and changes on the seismic wave field $rain a ne# generation of researchers4 -= *h4 positions across <urope !ermany University of Hamburg (Coordinator3 "%U Munich GFS Potsdam S&itzerland A(H ZTrich 9rance !PGP Paris Université Grenoble Al/es 1reland L!AS Dublin :; University of Edinburgh Uritish Geological 'ervice %ore about 'PIN4 htt/4VVs/in-itn-eu 'lides 8 more4 celine-hadzii-com twitter-comV'PIN_itn References 1n this presentation: Hadziioannou, C-, Gaebler, P-, 'chreiber, U-, Wassermann, J-, & Igel, H- 0;<=;3- A&amining ambient noise using colocated measurements of rotational and translational motion. Journal of 'eismology, =M0G3, FKF$F>M- htt/4VVd&-doi-orgV=<-=<<FVs=<>J<$<=;$>;KK$J C- Juretze5, C- Hadziioannou, 0;<=F3- "in5ing source region and ocean #ave /arameters #ith the observed /rimary microseismic noise, Geo/hys- J- Int- ;== 0C3, =MG<$=MJG- htt/s4VVdoi-orgV=<-=<>CVgXiVgg&CKK C- Juretze5, C- Hadziioannou, 0;<=M3- here do ocean microseisms come from7 A study of "ove$to$*ayleigh #ave ratios, J- Geo/hys- *es- 'olid Earth =;=, MFG=$MFJM htt/4VVd&-doi-orgV=<-=<<;V;<=MJU<=C<=F D*+%,4 A Multi$Com/onent *ing "aser for Geodesy and Geo/hysicsE 0;<;=3 Geo/hysical Journal International, ;;J0=3, MKG – M>K- htt/s4VVdoi-orgV=<-=<>CVgXiVggaaM=G earthAr&iv htt/s4VVearthar&iv-orgVre/ository/vie#V=F;CV Y"ord of the *ingsY, 'cience ;= A/r ;<=F4 Vol- CJM, Issue MCCJ, //- ;CM$;CK L+!4 =<-==;MVscience-CJM-MCCJ-;CM Paitz, P-, 'ager, Z-, & 9ichtner, A- 0;<=>3- *otation and strain ambient noise interferometry. Geo/hysical Journal International, ;=M0C3, =>CK$=>J;- htt/s4VVdoi-orgV=<-=<>CVgXiVggy5;K a/enaar, Z-, Draganov, L-, 'nieder, *-, Cam/man, [-, & Verdel, A- 0;<=<3- (utorial on seismic interferometry: Part =\Uasic /rinci/les and a//lications- Geo/hysics, FJ0J3, FJA=>J$FJA;<>- htt/s4VVdoi-orgV=<-==><V=-CGJFGGJ References Rotational seismology database 'alvermoser, J-, Hadziioannou, C-, Hable, S-, Krischer, L-, Cho#, B-, Ramos, C-, Wassermann, J., Schreiber, U-, Gebauer, A & !gel, H- (;<=F3- An event database for rotational seismology- Seismological Research Letters. htt/s4VVrotations-database-geophysi5-uni$muenchen-deV !et started &ith rotational data seismo-live-org → rotational seismology 6 C introductory noteboo5s to re/roduce some figures from the rotational database presented in the lin5 above.