Tectonic Tremor Triggered along Major Strike-Slip Faults around the World S51B-2362 Chastity Aiken1, Zhigang Peng1, David R. Shelly2, David P. Hill2, Hector Gonzalez-Huizar3, Kevin Chao4, Jessica Zimmerman5, Roby Douilly6, Anne Deschamps7, Jennifer Haase8, and Eric Calais9 1Georgia Institute of Technology; 2 U.S. Geological Survey, Menlo Park; 3 University of Texas, El Paso; 4 University of Tokyo, Earthquake Research Institute; 5 Texas A & M University, Commerce; 6 Purdue University; 7 Université de Nice Sophia Antipolis; 8 Scripps Institute of Oceanography; 9 Ecole Normale Superieure Research Question Triggered Tremor Observations Triggering Potential How does triggered tremor differ on strike-slip faults around the world?
Eastern Denali Fault of Yukon Territory, Canada San Andreas Fault of Parkfield, California Figure 7 (LEFT). Theoretical example of triggering Background 20130105 M7.5 Dist: 625.8 km BAZ: 163.2 deg Station: CN.HYT 20121028 M7.7 Dist: 2080.0 km BAZ: 337.7 deg Station: BK.PKD potential as a function of wave amplitude (i.e. stress), Deep tectonic tremor, which generally occurs in the lower crust beneath the 64˚ (a) 6 (a) 0.08 depth (i.e. frequency), and incidence angle on a vertical Mw7.9 North Love American BHT seismogenic zone where earthquakes occur, has been observed at several major Plate HHT 4 strike-slip fault. From Hill and Prejean (2013). CDF 0.04 Yukon Alaska Parkfield plate-bounding faults around the Pacific Rim. In order to investigate the potential 2012 Haida Gwaii 63˚ 2 M 7.5 0 BHR link between tremor and earthquake nucleation, further study of when, where, and Totschunda Fault HHR 2012 Sumatra EDF Pacific 0 Plate M 7.7 BVCY how tremor occurs is needed. Tremor is known to occur ambiently, sometimes in YUK1 Velocity (cm/s) −0.04 −2 Rayleigh association with GPS detected slow-slip events but could also be triggered by 62˚ Velocity (cm/s) BHZ YUK2 YUK3 HHZ Eastern Denali Fault −4 −0.08 100 km small stress perturbations arising from solid earth tides as well as passing seismic YUK4 −6 3 YUK5 Normal Parallel Normal Parallel waves of a distant earthquake. Because triggered tremor occurs on the same fault (b) 2 61˚ YUK6 (b) 20 km HYT 2 1.5 10 patch as ambient tremor (Gomberg, 2010) and generally has a higher signal-to- YUK7 1 2012 Costa Rica BHZ 1 (a) (b) HHZ 0 10 ↓ ↓ ↓ ↓ 1 0 hp > 5 Hz Figure 8 (RIGHT). Triggering 10 noise ratio, it is relatively easy to identify. hp > 20 Hz −1 −1.5 0 60˚ 2004 Parkfield EQ 2012 El Salvador −5 0
Velocity (cm/s) earthquake characteristics for all 10 -148˚ -146˚ -144˚ -142˚ -140˚ -138˚ -136˚ −2 −5 x10 10 Velocity (cm/s) x10 −3 Low-freq EQ −1 2012 Oaxaca 10 earthquakes studied in Yukon, Canada. We present a review of triggered tremor in 4 strike-slip regions: (1) the Eastern 40 10 −1 35.5˚NWave Incidence 36˚N 36.5˚N (c) 10 (c) 8 30 (a) Peak transverse dynamic stress vs. −2 Denali Fault in Yukon, Canada, (2) the Queen Charlotte Fault near Haida Gwaii, Seismic Stations 6 10 10 kPa −2 BHZ angle of seismic wave incidence. (b) 10 Canada, (3) the San Andreas Fault near Parkfield, CA, and (4) the Enriquillo- 20 HHZ 121.5˚W 121˚W 120.5˚W 120˚W 4 −3 10 −3 2 10 Surface wave velocity spectra. Event 10 Frequency (Hz) Plaintain Garden Fault in the southern Haiti peninsula. We characterize triggered −4
Frequency (Hz) 0 0 200 400 600 800 1000 1200 1400 labels in (b) also pertain to outline 10 Triggering 2011 Tohoku−Oki −4 tremor as broadband signals with long duration that are coincident with surface 0 50 100 150 200 250 300 350 400 450 500 Time since mainshock (s) 2012 Sumatra 10 −5 Non−triggering Time since mainshock (s) color in (a) and in map for this region 2012 Haida Gwaii Amplitude Spectra (cm/s/Hz) 10 2013 Craig, Alaska −5 waves from a distant earthquake. We locate tremor sources using the envelope Transverse Dynamic Stress (MPa) Figure 3. Tremor triggered near the Eastern Denali Fault of northwest Canada. Figure 5. Tremor triggered on the San Andreas Fault near Parkfield, CA. (Figure 3). ↑ ↑ ↑ ↑ Non−triggering 10 cross-correlation method or a matched filter technique (Shelly et al., 2006) if it is −2 −1 0 1 0 90 180 270 360 10 10 10 10 Back Azimuth (deg) Frequency (Hz) visible on 3 or more stations. We discuss triggering potential in each region in (LEFT) Map view of the Eastern Denali Fault with average triggered tremor sources marked (LEFT) Map view of the San Andreas Fault with average triggered low-frequency terms of dynamic stress, seismic wave incidence, and frequency dependence. by circles. Stations are triangles. “Beach balls” and dots are earthquakes. earthquake (LFE) sources marked. Dots are earthquakes. Queen Charlotte Fault
Normal Parallel Normal Parallel (RIGHT) Example of tremor triggered by the 2013/01/05 Mw 7.5 Craig, AK earthquake (RIGHT) Example of tremor triggered by the 2012/10/28 Mw 7.7 Haida Gwaii earthquake. Figure 1. Illustration of the brittle, −1 (green star in map above). 1 (a) (b) 10 fast-slipping seismogenic zone Red circles are matched filter detected LFEs (Shelly et al. 2006). 10 ↓ ↓ ↓ ↓ Figure 9 (LEFT). Triggering 0 −2 (red), and slow-slip zones (yellow), 10 Triggering 10 earthquake characteristics for all Possible Triggering −3 −1 10 and stable sliding zones (blue) for a 10 Non−triggering earthquakes studied in Haida vertical fault. Red zone is where −2 −4 Gwaii, Canada. Symbols and Queen Charlotte Fault of Haida Gwaii, Canada Enriquillo-Plantain Garden Fault of Haiti 10 10 kPa 10 −5 earthquakes generally occur. −3 10 notation are the same as in Figure 7. 20110311 M9.0 Dist: 6425.9 km BAZ: 292.1 deg Station: CN.MOBC 20100227 M8.8 Dist: 5985.8 km BAZ: 180.2 deg Station: CN.JAKH 10 Tremor generally occurs in the −6 Event labels in (b) also pertain to (a) −4 (a) Love 10 2002 Denali 10 QCF ~ 5 cm yr -1 Love HA19 2004 Sumatra region marked by the ellipse. From 0.4 outline color in (a) and in map for 0.4 HHT −5 2010 Chile −7
MASB BHT Amplitude Spectra (m/s/Hz) NDB 50 km HA18 HA17 HA20 2011 Tohoku−Oki 10 HA16 10 Kanamori (2008). 1 Denali HA15 HA21 2012 Sumatra this region (Figure 4). HA14 HA13 0.2 Transverse Dynamic Stress (MPa) Non−triggering −8 2 Sumatra 2004 0.2 HA11 PAPH ↑ ↑ ↑ ↑ 10 GRG −2 −1 0 1 BNAB -1 0 90 180 270 360 3 Chile Ms8.1 EPGF 6 +/- 2 mm yr HHR 10 10 10 10 BHR MRG PTG M 7.0 0 1 0 w Back Azimuth (deg) 4 Tohoku-Oki VIB PEM Frequency (Hz) 2 MOBC −0.2 Rayleigh DIB −0.2 Rayleigh Velocity (cm/s) 4 Velocity (cm/s) JAKH Mw7.7 HA03 HHZ BHZ HA02 San Andreas Fault HA10 HA04 HA01 Mw7.9 HA09 HA07 HA05 −0.4 −0.4 HA08 Methods 1 BNB HA06 Normal Parallel Normal Parallel North 4 2
American 3 18˚N 18.5˚N 10 2 Plate (b) (b) Strike-slip faults with no tremor observations, 3 2 1 (a) (b) 4 Pacific 1.5 Time since mainshock (s) 10 1 Select a study region Plate HHZ Figure 10 (RIGHT). Triggering ↓ ↓ ↓ ↓ 10
52˚N 53˚N 54˚N BBB BHZ comparable to the San Andreas Fault 1400 1500 1600 1700 1800 1900 0 0 bp 5−15 Hz 0 3 Juan de Fuca bp 5−15 Hz earthquake characteristics for all 10 0 Plate −2 10 −1.5 −4 −5 Velocity (cm/s) x10 earthquakes studied near Parkfield, −1 134˚W 132˚W 130˚W Velocity (cm/s) x10 10 −1 −4 10 −3 73.5˚W 73˚W 72.5˚W 72˚W 20 20 CA. Symbols and notation are the −2 Shallow, less < 100 km depth (c) 10 10 kPa −2 (c) 15 15 same as in Figure 7. Event labels in 10 Select earthquakes as Magnitude > 5.5 −3 10 HHZ 10 −3 10 BHZ (b) also pertain to outline color in Known Triggers 10 Distance > 100 km −4 potential triggers 5 2012 Haida Gwaii 5 (a) and in map for this region 10 Triggering 2012 Oaxaca −4 Frequency (Hz) 10 Peak dynamic stress > 1 kPa Frequency (Hz) 2012 Sumatra 0 −5 Non−triggering 0 0 500 1000 1500 2000 2500 3000 3500 4000 2012 El Salvador 800 1000 1200 1400 1600 1800 2000 2200 2400 (Figure 5). 10 −5 Amplitude Spectra (cm/s/Hz) Time since mainshock (s) 2012 Costa Rica 10
Time since mainshock (s) Transverse Dynamic Stress (MPa) Non−triggering ↑ ↑ ↑ ↑ −2 −1 0 1 Figure 4. Tremor triggered near the Queen Charlotte Fault of western Canada. From Aiken et 0 90 180 270 360 10 10 10 10 Instrument correction Figure 6. Tremor triggered near the Enriquillo-Plantain Garden (EPG) Fault of the southern Haiti Back Azimuth (deg) Frequency (Hz) Retrieve, process, and Filtering al. (2013). peninsula.
Triggered tremor identification Enriquillo-PlantainNVT in Haiti triggered by the 2010 Mw8.8 Maule, Garden Chile earthquake Fault analyze seismic data Triggered tremor location (LEFT) Map view of the Queen Charlotte Fault with average triggered tremor sources (LEFT) Map view of the EPG Fault with triggered tremor bursts marked by circles (average marked by circles. Stations are triangles. Stars and dots are earthquakes. location marked by green star). Land stations are triangles. OBS stations are marked by their Rayleigh (HHZ) 1 cm Figure 11 (LEFT). Time dependent names. White star and dots are Haiti mainshock and its aftershocks. Displ. Love (HHT) dynamic stress computed for the (RIGHT) Example of tremor triggered by the 2011/03/11 Mw9.0 Tohoku-Oki, Japan c.c.= 0.12 Enriquillo-Plantain Garden Fault at 20 earthquake. (RIGHT) Example of tremor triggered by the 2010/02/27 Mw8.8 Maule, Chile earthquake. Rayleigh c.c.= 0.78 km depth with a friction coefficient of Love 10 kPa c.c.= 0.76 0.2. (TOP) Vertical and transverse Total Dynamic Stress displacement seismogram. (MIDDLE) Dynamic “stress”grams for vertical and NVT envelope Literature Cited Conclusions NVT transverse components. (BOTTOM) Tremor and envelope. Aiken, C., Z. Peng, and K. Chao (2013), Tremor triggered along the Queen Charlotte • We discovered triggered tremor on 3 strike-slip faults where tremor was not 1200 1400 1600 1800 Margin by large teleseismic earthquakes, Geophys. Res. Lett., 40, doi: 10.1002/grl.50220. previously reported. Time (s) by H. Gonzalez-Huizar (2013) Gomberg, J. (2010), Lessons from (triggered) tremor, J. Geophys. Res., 115(B10), doi: UTEP 10.1029/2009JB007011. • We located the tremor sources to be on or near the fault traces in each of the regions. Acknowledgments Hill, D. P. and S. Prejean (2013), Dynamic triggering, vol. 4, Earthquake Seismology, • Our triggering observations are in agreement with the Coulomb failure criterion (Hill C.A. is supported by National Science Foundation (NSF) Graduate Research Fellowship Treatise on Geophysics. and Prejean, 2013). DGE-1148903. Z.P. is supported by NSF CAREER grant EAR-0956051.
Kanamori, H. (2008), Earthquake physics and real-time seismology, Nature, 451, 271-273, • Long period, large amplitude surface waves are responsible for triggering tremor in doi:10.1038/nature06585. these regions, as has been observed elsewhere. Figure 2. Location of tremor sources around the world, with regions Shelly, D. R., G. C. Beroza, S. Ide, and S. Nakamula (2006), Low-frequency earthquakes where tremor has not previously been discovered (this study) marked in Shikoku, Japan, and their relationship to episodic tremor and slip, Nature, 442, 188-191, • The Parkfield segment of the San Andreas Fault is more easily triggered than the Corresponding Author: [email protected] as red stars. doi: 10.1038/nature04931. other regions, which reflects recent strength properties of the fault.