Aftershock data for the 2017 MW5.5 Pohang earthquake

# written by J.-U. Woo
Data includes [1] initial earthquake catalog and [2] relocated earthquake catalog

Suggested citations:
(For the uploaded catalogs) 1. J.-U. Woo, M. Kim, J. Rhie, and T.-S. Kang, 2020, Aftershock sequence and statistics of the 2017 MW 5.5 Pohang earthquake, South Korea: implications of fault heterogeneity and post-seismic relaxation, Bulletin of Seismological Society of America. Detailed information will be posted on the zenodo website.

Further suggested citations:
(For 1-D velocity model at EGS site and catalogs at Pohang EGS site) 2. J.-U. Woo, M. Kim, D.-H. Sheen, T.-S. Kang, J. Rhie, F. Grigoli, W.L. Ellsworth, D. Giardini, 2019, An In-Depth Seismological Analysis Revealing a Causal Link Between the 2017 MW 5.5 Pohang Earthquake and EGS Project, JGR solid earth, doi:10.1029/2019JB018368.
3. W.L. Ellsworth, D. Giardini, J. Townend, S. Ge, and T. Shimamoto, 2019, Triggering of the Pohang, Korea, Earthquake (Mw 5.5) by Enhanced Geothermal System Stimulation. Seismological Research Letters, 90(5), 1844-1858.
4. K.-K. Lee, W.L. Ellsworth, D. Giardini, J. Townend, S. Ge, T. Shimamoto, I.-W. Yeo, T.-S. Kang, J. Rhie, D.-H. Sheen, C. Chang, J.-U. Woo, C. Langenbruch, 2019, Managing injection-induced seismic risks. Science, 364(6442), 730-732.
5. C. Langenbruch, W. L. Ellsworth, J.-U. Woo and D. J. Wald, 2020, Value at Induced Risk: Injection-induced seismic risk from low-probability, high-impact events. Geophysical Research Letters, 47, e2019GL085878. http://doi.org/10.1029/2019GL085878.

Descriptions:
[1] Initial earthquake catalog (cat1)
 - First column: event index (sequentially increasing number)
 - Second column: event ID
 - Third column: event origin date as year/month/day_of_month
 - Fourth column: event origin time as hour:minute:second
 - Fifth and sixth columns: latitude and longitude in degree
[2] Relocated earthquake catalog (cat2, not shifted; hypocentroid-shifted data will be overwritten within a few days)
 - First column: event index (linked with event index of cat1)
 - Second column: event ID (linked with event ID of cat2)
 - Third column: event origin date as year/month/day_of_month
 - Fourth column: event origin time as hour:minute:second
 - Fifth and sixth columns: latitude and longitude in degree
 - Seventh column: depth in km
 - Eighth column: 1.96*(standard deviation of W-E relative locations obtained from 200 times of bootstrap resampling) in meter
 - Ninth column: 1.96*(standard deviation of S-N relative locations obtained from 200 times of bootstrap resampling) in meter
 - Tenth column: 1.96*(standard deviation of relative depths obtained from 200 times of bootstrap resampling) in meter