Electronic Supplement to

Rupture Directivity Analysis of the 2018 Hokkaido Eastern Iburi

Earthquake and its Seismotectonic Implication

by Chong Zang, Sidao Ni, Zhichao Shen

This electronic supplement contains: Analysis of teleseismic waveforms for 2018 Hokkaido

Eastern Iburi Earthquake; Waveform fitting for seismic stations in point source inversion;

Uncertainty test for different velocity models.

List of Figure Captions

Figure S1. Analysis of teleseismic waveforms. (a) Comparison of observations with synthetics.

The broadband vertical component displacement waveforms are showed here. For synthetics, the

centroid depth and double-couple focal mechanism come from gCMT. (b) Velocity model used to

generate the synthetics. Black: for eastern stations. Red: for western stations. (c) Comparison of

individual phases (P, pP, sP; red line) with full wave field (black dashed line) by wavefield

decomposition. For each phase, the energies of other phases are compressed. The theoretical

arrival time of P, pP and sP are marked by blue dashed line.

Figure S2. Waveform fitting for seismic stations in point source inversion. Station names,

azimuths and epicentral distances are showed on the left side. Cross-correlation coefficients and

time shifts are showed on the right side. Black and red traces are observed and synthetic

seismograms, respectively.

Figure S3. Uncertainty test for different velocity models. (a) Three velocity models tested in this

study. Black: the crust1.0 model without sediment (Eastern model). Red: the crust1.0 model with

sediment (Western model). Blue: the crust2.0 model. (b) Point source inversion results for

different velocity models. (c) Rupture directivity analysis results for different velocity models.

Rupture models are marked with various symbols (Circle: NP1-model; Star: NP2-model; Triangle:

Point source model). Color of the symbols correspond to the above three velocity models. The

black dashed lines show results in this study.

Figure S1. Analysis of teleseismic waveforms. (a) Comparison of observations with synthetics.

The broadband vertical component displacement waveforms are showed here. For synthetics, the

centroid depth and double-couple focal mechanism come from gCMT. (b) Velocity model used to

generate the synthetics. Black: for eastern stations. Red: for western stations. (c) Comparison of

individual phases (P, pP, sP; red line) with full wave field (black dashed line) by wavefield

decomposition. For each phase, the energies of other phases are compressed. The theoretical

arrival time of P, pP and sP are marked by blue dashed line.

Figure S2. Waveform fitting in point source inversion. Station names, azimuths and epicentral

distances are showed on the left side. Cross-correlation coefficients and time shifts are showed on

the right side. Black and red traces are observed and synthetic seismograms, respectively.

Figure S3. Uncertainty test for different velocity models. (a) Three velocity models tested in this

study. Black: the crust1.0 model without sediment (Eastern model). Red: the crust1.0 model with

sediment (Western model). Blue: the crust2.0 model. (b) Point source inversion results for

different velocity models. (c) Rupture directivity analysis results for different velocity models.

Rupture models are marked with various symbols (Circle: NP1-model; Star: NP2-model; Triangle:

Point source model). Color of the symbols correspond to the above three velocity models. The

black dashed lines show results in this study.