Fault “Corrosion” by Fluid Injection: A Potential Cause of the November 2017 5.5 Korean Earthquake

Table 1

Pohang borehole stratigraphy.

Lithology	Name	Depth (m)	Age	Note
Mudstone	Yeonil group	0	Middle Miocene	1
Tuff	Beomgokri group	206		2
Mudstone	Yucheon group	330		3
Andesite	Gyeongsang volcanics	1250	Late Cretaceous	4
Granodiorite	Pohang granite	2356		5

Data for well PX-1 are from [13, 16], supplemented here with additional information. Depth is to the top of each stratigraphic division. Notes: 1: biostratigraphic age from [93]. 2: youngest ²⁰⁶Pb/²³⁸U date reported on detrital zircon, from [36], in overlying mudstone. Name from [41]. 3: lacustrine mudstone with interbedded sandstone, tuff, and rhyolitic lava. Representative ²⁰⁶Pb/²³⁸U date on zircon, from [36], for the rhyolite. Nomenclature from [32, 94]. 4: interbeds of andesite and andesitic tuff. Nomenclature from [32]. 5: granodiorite with gabbroic dykes. Oldest ²⁰⁶Pb/²³⁸U date on zircon, from [36].