Multiple damage zone structure of an exhumed seismogenic megasplay fault in a subduction zone - a study from the Nobeoka Thrust Drilling Project

Hamahashi, Mari; Hamada, Yohei; Yamaguchi, Asuka; Kimura, Gaku; Fukuchi, Rina; Saito, Saneatsu; Kameda, Jun; Kitamura, Yujin; Fujimoto, Koichiro; Hashimoto, Yoshitaka

doi:10.1186/s40623-015-0186-2

Earth, Planets and Space

Table 2 Values of fracture density and physical properties for each interval in the footwall

From: Multiple damage zone structure of an exhumed seismogenic megasplay fault in a subduction zone - a study from the Nobeoka Thrust Drilling Project

Interval footwall	Depth (mbgs)	Fracture density total/density (number per 1 m)	Porosity (%)	Resistivity (Ω m)	Density (g cm − ³ )	P -wave velocity (km s − ¹ )	Gamma ray (API)	Cementation exponent m
Footwall unit 1 (42.1 to 80 mbgs)
Intact zone	41.8 to 66.7	245/10	7.6	232	2.72	4.25	123	0.60
Damage zone	66.7 to 75, 80 to 85.7	102/7	7.8	241	2.71	4.34	124	Upper: 1.07, Lower: 0.92
Brecciated zone	75 to 80	43/9	10.9	166	2.65	3.94	125	0.82
Footwall unit 2 (80 to 112 mbgs)
Intact zone	85.7 to 95	96/11	7.6	226	2.70	4.25	125	0.95
Damage zone	95 to 112, 115 to 124	249/10	7.6	251	2.70	4.19	123	Upper: 0.80, Lower: 0.96
Brecciated zone	112 to 115	25/9	31	80	2.08	2.29	94	0.36
Footwall unit 3 (112 to 180 mbgs)
Intact zone	124 to 134, 174 to 180	121/8,354/9	7.2	281	2.72	4.29	126	1.00
Damage zone	134 to 157, 159 to 174	354/9	7.2	330	2.71	4.40	127	Upper: 1.22, Lower: 0.88
Brecciated zone	157 to 159	011/6	10.9	168	2.65	3.96	128	0.26
Footwall unit 4-1 (180 to 196.6 mbgs)
Intact zone	180 to 184.6	25/6	7.1	255	2.72	4.39	126	0.56
Damage zone	184.6 to 188, 189 to 196.6	73/7	6.7	270	2.73	4.50	126	Upper: 1.00, Lower: 1.00
Brecciated zone	188 to 189	14/16	8.4	205	2.69	4.10	124	0.72
Footwall unit 4-2 (196.6 to 221.2 mbgs)
Intact zone	196.6 to 201.8	54/11	6.4	283	2.71	4.57	128	0.79
Damage zone	201.8 to 210, 212 to 221.2	167/10	7.0	281	2.72	4.34	128	Upper: 0.95, Lower: 1.12
Brecciated zone	210 to 212	20/10	9.4	209	2.59	3.55	123	0.49
Footwall unit 4-3 (221.2 to 255 mbgs)
Intact zone	221.2 to 222.5, 247.3 to 255	73/8	6.4	234	2.73	4.61	126	0.79
Damage zone	222.5 to 242, 243 to 247.3	179/8	6.6	228	2.73	4.46	127	Upper: 1.42, Lower: 0.86
Brecciated zone	242 to 243	13/13	10.2	101	2.65	3.58	123	0.58

Depth, fracture total number distribution, fracture density (number of fractures per 1 m), neutron porosity, resistivity, density, P-wave velocity, natural gamma ray values, and Archie’s cementation exponent m for the intact zones, surrounding damage zones, and the brecciated zones in the footwall are presented.

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