A copy of this work was available on the public web and has been preserved in the Wayback Machine. The capture dates from 2010; you can also visit <a rel="external noopener" href="http://eqkc.earth.ncu.edu.tw:80/papers/2006_Ma_etal_Nature.pdf">the original URL</a>. The file type is <code>application/pdf</code>.
<i title="Springer Nature">
<a target="_blank" rel="noopener" href="https://fatcat.wiki/container/drfdii35rzaibj3aml5uhvr5xm" style="color: black;">Nature</a>
Determining the seismic fracture energy during an earthquake and understanding the associated creation and development of a fault zone requires a combination of both seismological and geological field data 1 . The actual thickness of the zone that slips during the rupture of a large earthquake is not known and is a key seismological parameter in understanding energy dissipation, rupture processes and seismic efficiency. The 1999 magnitude-7.7 earthquake in Chi-Chi, Taiwan, produced large slip<span class="external-identifiers"> <a target="_blank" rel="external noopener noreferrer" href="https://doi.org/10.1038/nature05253">doi:10.1038/nature05253</a> <a target="_blank" rel="external noopener" href="https://www.ncbi.nlm.nih.gov/pubmed/17122854">pmid:17122854</a> <a target="_blank" rel="external noopener" href="https://fatcat.wiki/release/djibpzzvxjhavhmw7rkihu5wa4">fatcat:djibpzzvxjhavhmw7rkihu5wa4</a> </span>
more »... to 10 metres) at or near the surface 2 , which is accessible to borehole drilling and provides a rare opportunity to sample a fault that had large slip in a recent earthquake. Here we present the retrieved cores from the Taiwan Chelungpu-fault Drilling Project and identify the main slip zone associated with the Chi-Chi earthquake. The surface fracture energy estimated from grain sizes in the gouge zone of the fault sample was directly compared to the seismic fracture energy determined from near-field seismic data 3,4 . From the comparison, the contribution of gouge surface energy to the earthquake breakdown work is quantified to be 6 per cent. The North-South-trending Chelungpu fault is a major 90-km structure that dips shallowly to the east (30u), and principally slips within, and parallel to, bedding of the Pliocene Chinshui shale 5 . Taiwan Chelungpu-fault Drilling Project (TCDP) drilled two vertical holes 40 m apart (hole A to a depth of 2 km, and hole B to a depth of 1.3 km), and a side-track from hole B (hole C) at the depth of 950 m to 1,200 m about 2 km east of the surface rupture, near the town of DaKeng (Fig. 1a) . The subsurface location of the Chinshui shale was known from high-resolution seismic reflection profiles 6,7 at a depth of about 1,000 m under the DaKeng site. The spatial slip distribution for the earthquake was well constrained from close strong motion stations and Global Positioning System (GPS) data 3,4 and shows a slip of 8.3 m on the fault near the drill site. The drilling carried out continuous coring for depths of 500-2,000 m for hole A, 950-1,300 m for hole B and 950-1,200 m for hole C, respectively. Geophysical well logs were carried out in hole A to collect seismic velocities, densities and digital images. From the hole-A core, the Chelungpu fault zone is seen within the Chinsui shale as a damaged zone at depths of about 1,105 to 1,115 m, consisting of fault breccia and fault gouge (Fig. 1b) . The degree of fracturing increases from the top to the bottom of the zone. Near the bottom of the broad zone of deformation, a 12-cm-thick primary slip zone (PSZ) can be identified based on the presence of ultra-finegrained fault gouge and increased fracture density at depths of 1,111.23 to 1,111.35 m. A corresponding feature was also found in the hole-B core at depths of 1,136.50 to 1,136.62 m, confirming the fault dip of 30u E. The geophysical logging measurements of low
<a target="_blank" rel="noopener" href="https://web.archive.org/web/20100326093913/http://eqkc.earth.ncu.edu.tw:80/papers/2006_Ma_etal_Nature.pdf" title="fulltext PDF download" data-goatcounter-click="serp-fulltext" data-goatcounter-title="serp-fulltext"> <button class="ui simple right pointing dropdown compact black labeled icon button serp-button"> <i class="icon ia-icon"></i> Web Archive [PDF] <div class="menu fulltext-thumbnail"> <img src="https://blobs.fatcat.wiki/thumbnail/pdf/2f/75/2f7554dbc73b3b13b92ede2a85eb3c137853847e.180px.jpg" alt="fulltext thumbnail" loading="lazy"> </div> </button> </a> <a target="_blank" rel="external noopener noreferrer" href="https://doi.org/10.1038/nature05253"> <button class="ui left aligned compact blue labeled icon button serp-button"> <i class="external alternate icon"></i> nature.com </button> </a>