In the formt provided y the uthors nd unedited. SUPPLEMENTARY INFORMATION DOI: 1.138/NGEO9 Tremor-rich shllow dyke formtion followed y silent mgm flow t Bárðrung in Icelnd 1,, 1, 3 1, 1 1, NATURE GEOSCIENCE www.nture.com/nturegeoscience 1 17 Mcmilln Pulishers Limited, prt of Springer Nture. All rights reserved.
Normlized RMS of velocity (m/s)... sk jk djk dyn kre kve mko von urh grf Best fitting curve 1 3 Distnce (km) Figure 1: Derivtion of site correction fctors. Root Men Squre (RMS) seismic mplitude t Icelndic Met Oce (IMO) sttions vs. hypocentrl source-receiver distnce of ve well locted events eneth the culdrons C1 to C3. Dt were ltered etween 3 nd Hz. Red points re discrded due to cler devition from the expected ehviour. The remining points re t ssuming ody wve decy of the mplitude with distnce. For ech point site correction fctors re derived with respect to the curve nd the medin is found for ech sttion. Freq. sk jk djk dyn kre kve mko von urh grf Q β nd (km/s) 3- Hz 9 93.9 1.3.9.11.9371 9 Tle 1: Site correction fctors derived in the 3- Hz frequency nd for events eneth the culdrons nd in the dyke.
17 3' 17 ' 17 1' 17 ' 1 8' 1 3' ' e 1 UR 8' 9 C3 C ' 1 1 1 C1 3' km 18 1 18 IMO loction Culdron Seismometer Dyke # S position sign size Figure : Azimuthl precision check of the rry. Mgnitude. event locted 1. km north of C3 t 7 km depth on Septemer 3 rd, 1 y IMO. (-d) The output of the FK nlysis (() ck zimuth, () slowness, (c) solute power nd (d) semlnce) coloured ccording to semlnce, incresing from.31 (lue) to.9 (red) is shown for UR. Typicl slownesses ssocited with ody nd surfce wves of n erthquke in the dyke cn e seen. (e) Projected ck zimuth of the P wve. The red dimond indictes the reltive reloction using the IMO sttions, which is within the error limits of the ck zimuth from UR. Elevtion in m.s.l., sed on dt from the Ntionl Lnd Survey of Icelnd. Velocity (m/s) 1... 1. 8 1 3 1 8 1 Time (s) Frequency (Hz).3.8...1.1 8 Figure 3: Simulted event from source t 3 km depth. () Normlised verticl component synthetic seismogrm t UR rry t 1 km distnce (the source is 1 Hz Ricker wvelet) nd () Amplitude spectrogrm with fst Fourier trnsform window length of. s nd % overlp. 3
Rel tremor 1:-1: km 1 km 1e 1... 1. c.. 1... 1. 1... 1. 1. d e Figure : Comprison of rel nd synthetic tremor simulted with perfectly regulr com function. Sugures s in gure ut for tremor simulted y convolving the synthetic seismogrm with perfectly regulr com function nd regulr mplitude distriution. All spectrogrms re mde with fst Fourier trnsform window length of 1 s... 1. 1. f 1e 7 8...3.1...3.1 Velocity (m/s) Frequency (Hz). 3. 3... 1. 1e 1 1 1e 1.3 1..9.7...3.1 Figure : Seismic recording t DY3 (see inset in gure 3) directly on top of the dyke on August 3 th, 1. () Seismogrm nd () Amplitude spectrogrm with fst Fourier trnsform window length of 1 s from DY3 t.8397 N nd 1.87 W ltered etween. nd Hz shows no indiction of continuous tremor signl.
3.. Tremor 11::3-11::3 Erthqukes Locl Mgnitude. 1.. 1-7 1-1 - 1 - Pek to pek mplitude (m/s) Figure : Mgnitude estimtion of the lrgest 'single events' in the tremor. Strs relte pek to pek mplitudes t UR with mgnitudes from the IMO erthquke ctlogue for events eneth culdrons C1 to C3 ltered etween 1 nd Hz. As the tremor seems to e composed of swrms of individul events we estimted pek to pek mplitude during minute long time window t the time of mximum tremor mplitude (dotted line) visully ensuring tht the mximum tremor mplitude does not correspond to dyke erthqukes. The lrgest individul event corresponds to mgnitude erthquke. Prmeter Prmeter rnge Ref. Prmeter vlues in reference Rock stiness (GP). - Length (km) 1 1 1 dyke segments re 1.1-1 km long Width (m) 1 1 1 rms of the EQ is 8-1 m " " " " " rdius of ow pth of.7 Fluid density (kg/m 3 ) 7 3-7 Viscosity (P s) 1 3 Flow velocity (m/s) 1 1-3.7, sed on incresed erthquke rte in dyke fter clder events Tle : Prmeters for the tremor simultion in the model of Julin constrined y eld mesurements.