k Jigu-Mulli-wa-Mulli-Tamsa Vol. 13, No. 3, 2010, p. 187~197 w ûw û š ³ sƒ * w w w Paleoseismological Study and Evaluation of Maximum Earthquake Magnitude along the Yangsan and Ulsan Fault Zones in the Southeastern Part of Korea Jai Bok Kyung* Korea National University of Education ù d w š w 1994 z., sw,, m š y ùkü, d û wš d» ùkù. š w d wš 20». wr,» 30 z ¾ ¾» ùkù, ¾ y w š. d p w w, w. wš d ƒ w. s³ mw d y sƒw w, s³ 0.1 ~ 0.04 m/ka C w w, s³ 0.2 ~ 0.06 m/ka B-C w w. ƒ d ³ x» w w ³ d s³ 6.8, š d 7.0. d y, w ƒ û.,, š w, ³, y Abstract: The paleoseismological study in Korea has begun along the Yangsan fault zone (YFZ) and Ulsan fault zone (UFZ) since 1994. Some evidences related to late Quaternary movement are found at only some part of the YFZ, such as Pyonghae, Yuge, and Eonyang-Tongdosa areas. However, it is found along the most of the UFZ except the northen and southern ends of the fault. The dominant time span of faulting events along the YFZ and UFZ are quite different, and 500 ka to 200 ka and 300 ka to recent time, respectively. The dominant faulting senses of the YFZ and UFZ are right-lateral strike slip and reverse, respectively. These senses correspond well with the focal mechanism of recent occurring earthquakes along these two fault zones. If we evaluate the intensity of the activity of the YFZ from the average slip rate, which is 0.1 ~ 0.04 m/ka, it is comparable with the faults of higher C class in Japan. The slip rate of UFZ, which is 0.2 ~ 0.06 m/ka, is comparable with the faults of lower B to higher C class. Based on the relationship between maximum displacement and magnitude, the maximum earthquake magnitude is evaluated to be 6.8 and 7.0 in the YFZ and UFZ, respectively. An intensive studies are needed to clarify the problems such as segmentation of faults, return period, and geological evidences related to historical earthquakes. Keywords: Yangsan fault zone (YFZ), Ulsan fault zone (UFZ), paleoseismology, maximum earthquake magnitude, activity of fault 2010 8 5 ; 2010 8 18 ; 2010 8 24 k *Corresponding author E-mail: jbkyung@knue.ac.kr Address: Dept. of Earth Science Education, Korea National University of Education Chongwon-Gun, Chungbuk, 363-791, Korea 187
188 š w x y ù ƒ¾ y w d, š w, ƒ» j» š y w ƒ w. 4»( 200 ) z» y w y e, ¼, s, d, xk»ww p, w,, d y, d w Ÿ w,, j»,»( ) w w w. w ³ x x x w x w w wš. d y» p ³ w x 4» z» y w. w w 2000 ù» mw vw w w š,,, s, y, w ùkù. ù eƒ y wš v w w d ƒ wì m w š w. w d w š w vw w ùƒ 1994 z. p, w š,, ƒ l w ƒ w ù 4» z» d w š w ƒ. p, q w j j ³ d w ù ƒ w ƒ w š. 1994 z ¾ w, xw, š w w, w š w w wš, š, t w w š w. ûw w š y 1994 z ƒ 4» z»( 50 z) d w š w mw w ƒ. x vw» mw ƒ 4» d sw ƒ f ƒ. ƒ w ew x vw w. Lee & Na(1983) w ƒ y w. w, Lee and Jin (1991) d w» mw y p 3 (segment) ù x. z y mw š y 1994 w œ (Okada et al., 1994) mw ƒ. d y» w (Otsuki & Ehiro, 1978; Chang et al., 1990; Yoon & Kim, 1990), Jolivet et al. (1991) y» 14 ~ 42 Ma w. w, z» ƒ y w, z w 3z w d 2z w ( š k, 1994; k, 1998). w d w, 25 km (Choi et al., 1980), 35 km (Chang et al., 1990). w 4» z» œ d mw š y ³ w. d 4» d x, p e, mw. x ¾ ³ ( : Okada et al., 1994; k, 2001; Kyung, 2003; Okada et al., 2001;, 2000; Inoue and Choi, 2006;, 2006) w w sƒ,»,,» w» ƒ. d» d w p e,, OSL, C 14, x, mw. Fig. 1 ¾ 4» z» d q ù p e (Y1 ~ Y14) ùkü. w, ƒ mw x d p ww Table 1 š, û Table 2. ¼ ¼ ( 170 km) w 4» z» d p, d (sw,, ) û ( m ) w» ùkù. 4» z» d w ƒ d w ùkú ƒ 2ƒ ù ƒw. x ¾ w»,
ûw û š ³ sƒ 189 Fig. 1. Locations of Late Quaternary faults along the Yangsan and Ulsan fault zones. U1 to U17 and Y1 to 14 indicate the locations of trench or outcrop along the Ulsan and Yangsan fault zones, respectively. (segment) ù ƒ y»ƒ ƒ w. ( k, 2001; Kyung, 2003; «, 2002;, 2006;, 2000; ½ Ÿ, 2006) ùkù 4»z» d w d ùkü, d w. d d w Á ƒ ùkù, s³ 0.04 ~ 0.05 mm/, d 2,000 ~ 2,400 BP ( k, 2001). û ( m ) 10 km (Okada et al., 1994;, 1999a, 1999b;, 2002) w, d sww 2~3 d 4» z» d w š q. 4» z» d w w, wœ q x Á Áš w ùkü, p e š w d w š, s³ s ƒ ƒ 0.02 ~ 0.03 mm/, 0.05 ~ 0.1 mm/ ùkü. d ƒ 4» z» d»ƒ 100 Ka¾ š (, 1999a). Table 1 Table 2 d ww ùkü Fig. 2. 3 w 400 ~ 500 ka y w š, ƒ ¾»¾ d w. û ( m ) 250 ~ 400 ka y w š 100 ka¾ ùkù. x w w y, xw ùkü û ùkù. d ¼ w w ƒ v w. y y (degree of fault activity) 4» d s³ (S: m/ka) AA (100 > S à 10), A (A (10 > S à 1), B (1 > S à 0.1), C (0.1 > S à 0.01) w (Matsuda, 1975). û ùkù s³ 0.04 ~ 0.1 m/ka w d y C class w w., d y y x û w š q ù d ƒ e yw w ƒ w. Table 1. Late Quaternary fault characteristics in the northern part of the Yangsan fault zone. y e d w ƒ š x Y1 sw sw N-S ~ 90 o w Y2 Y3 36 o 44'49.6"N 129 o 26'39.6"E 36 o 12'05.2"N 129 o 18'16.2"E 36 o 03'34.7"N 129 o 15'14.0"E N-S 45 o E N17 o E 44 o E 500 ± 70 ka 420 ± 70 ka 460 ± 20 ka 1314 yr BP ~ 39,400 yr BP N11 o E 80 o SE ~ 90 o w 420 ± 30 ka 400 ± 20 ka, 14 C w (2006) (2000) k (2001) Kyung(2003) «(2002)
190 Table 2. Late Quaternary fault characteristics in the southern part of the Yangsan fault zone. y e d w ƒ š x Y4 y y N40 o E 78 o NW w about 300 ka (1999b) Y5 1 1 Y6 2 2 Y7 ƒ 1 ƒ 1 Y8 ƒ 2 ƒ 2 Y9 Y10 s 1 s1 Y11 s 2 s2 ( s) Y12 (») Y13 Y14 35 o 32'55"N 129 o 07'19E 35 o 31'56.44"N 129 o 06'41.22"E N20 ~ 70 o ~ 85 o 30 o E SE w 35 o 32'04.7"N 129 o 06'40.9"E w 35 o 31'14.0"N 129 o 06'6.4"E 35 o 31'05.71"N 129 o 06'32.3"E 35 o 30'10.3"N 129 o 06'7.7"E 35 o 29'49.0"N 129 o 05'29.1"E 35 o 29'50.0"N 129 o 05'37.6"E 35 o 26'25.7"N 129 o 07'56.6"E 35 o 20'21.2"N 129 o 01'40.7"E 35 o 19'35.6"N 129 o 03'22.9"E 480Û40 ka 340Û30 ka about 100 ka about 300 ka, (2006), (1999a) (1999a) N10 o ~ 85 o SE 30 o E w (2002) N37 o E 80 o NW w (2002), w N25 o E 90 w o N10 o E 76 o SE (2000) Okada et al. (1994), (1998) N14 o E 48 o ~ 60 o SE (1998) N28 o E 80 o NW w NW 65 o ~ 79 o SW w 400Û50 ka 400Û30 ka 370Û60 ka 400Û40 ka 370Û50 ka 600Û40 ka 480Û70 ka 490Û70 ka 310Û20 ka 380Û60 ka (2006) «(2003) > 3,000 ka «(2003) Fig. 2. History of paleo-earthquakes in the Yangsan fault zone. l Ÿ NNW-SSE(y N-S) w 50 km d, d d w w. d wš w» d l d ƒ w w x ww x. w sk š,,, d ty, n v w šm ù š,,. w ƒ š d w ùkù œ y š. x ¾ y w w ù, Okada (1998) š 14 ~ 20, 5~6, 2~3 x d w. sw d w 4» d d d p e w. ù l w x e š ù d (, d, d, d, y,, š d,,, y d ) mw d xk 4» d p q w ( : k, 2001; 2002;, 1998, 2000;, 2002; Kyung, 1997; Ree and Kwon, 2005). ù
ûw û š ³ sƒ 191 Fig. 3. History of paleo-earthquakes in Ulsan fault zone. d š w mw d ³ w» w x d w š. wr, Fig. 1 d û wš d» ùk ù. w w, d w w d p š, mw w d» w ùkü (Table 3). wš d ƒ w. p e w d ƒ w Table 3. Late Quaternary fault characteristics in Ulsan fault zone. y e d w ƒ š x U1 š 1 š1 U2 š 2 š2 U3 š 3 š3 35 o 53'36.5"N 129 o 17'25.8"E 35 o 53'26.7"N 129 o 17'19.5"E U4 35o 52'43.3"N 129 o 19'39.5"E U5 U6 1 2-N 2-S 1 2-N 2-S N20 o W 0 o ~ 40 o 13,760Û140 yr BP 14,010Û240 yr BP 14 C, Okada et al. (2001) Suzuki et al. (2005) (2007) N50 o E 70 o SE Okada et al. (1999) 35 o 53'13.6"N 129 o 17'15.3"E N20o W 30 o ~ 60 o SE w (2005) 35 o 48'00.8"N 129 o 18'55.8"E 35 o 47'40.0"N 129 o 19'04.6"E N35 o E 50 o SE 44,610Û1,140 yrbp, 54Û7 ka 76Û5 ka, 90Û6 ka 81Û5 ka, 82Û5 ka 14 C OSL w(2003), Cheong et al. (2003) N21 o E N21 o E 320Û30 Ma (2006) N40 o W 45 o NE 250 ~ 300 ka 60 ~ 150 ka 35 o 47'32.8"N 250 ~ 300 ka U7 N25 o W 56 o NE 129 o 19'06.0"E 60 ~ 150 ka U8 x x 35o 46'58.9"N 129 o 19'53.9"E N15o W 70 o ~ 80 o NE 250 ~ 300 ka d U9 p p 35o 46'52.4"N 129 o 20'20.0"E U10 (Ÿ ) U11 35 o 46'01.7"N 129 o 20'16.2"E y y 35o 45'16.8"N 129 o 20'16.3"E U12 35o 44'51.4"N 129 o 20'14.5"E N04 o E 30 o SE 250 ~ 300 kaa d N30 o E 30 o SE 240Û20 ka, 320Û20 ka 370Û20 ka, 320Û20 ka 300Û10 ka, y (1999) Kyung and Lee (2006) y (1999) Kyung and Lee (2006) y (1999) y (1999) (2006) N27 o E 49 o SE > 3,000 ka KBSI N-S 30 o E U13 š 1 š1 35 o 44'02.1"N 129 o 20'03.1"E N10o W 20 o ~ 50 o NE U14 U15 35o 43'17.3"N 129 o 21'04.2"E 35o 41'49.7"N 129 o 21'02.1"E U16 y y 35o 39'44.2"N 129 o 20'40.5"E U17 35o 37'17.6"N 129 o 22'10.8"E N-S 75 o E N5 o E 12 o SE 30,150Û290 yrbp 160Û30 ka, 180Û5 ka 180Û60 ka, 210Û10 ka 2,290Û40yBP 7,470Û40yrBP 7,910Û50yBP 7,820Û220yBP 7,850Û100yBP 30,660Û450BP 31,250Û420yBP 12Û1 ka 39,100Û2000yBP 27,000yBP 70Û39 ka 53Û4 ka 130Û10 ka 200Û30 ka 400Û20 ka 460Û50 ka 230Û60 ka 480Û30 ka 14 C,, 14 C OSL 14 C OSL w N08 o E 74 o SE 660Û50 ka N10 o W 25 o NE 47,363Û12,535 yr BP (2006) Okada et al. (1998) (2000) KBSI, w (2005) Lee et al. (2002),. Okada (PC). Lee and Schwarcz (2001) Lee and Schwarcz (2001) 14 C (2001)
192 w convex ùkü ( : Okada et al., 1998a; Okada et al., 2001). Fig. 3 Table 3» d e y» w ùkü. š w d d wš 20». wr,» 30 z ¾ ¾» ùkù. w d x w yw d w ƒ š. x ¾ x»», s³, w l d w. s³, š d 0.1 ~ 0.06 mm/ (Okada et al., 2001; Suzuki et al., 2005; Inoue and Choi, 2006), 0.08 mm/, w 0.22 ~ 0.05 mm/ (Okada et al., 1998b), 0.1 ~ 0.08 mm/ (Okada et al., 1998a), š d 0.15 mm/ (Inoue and Choi, 2006) 0.06 ~ 0.2 mm/ s ùkü. 4» d s³ y y sƒw w B-C w š. w, d ùkù (one time vertical slip) š d 0.8 m (Okada et al., 2001; Suzuki et al., 2005; Inoue and Choi, 2006), (net slip) 1.6 m (Suzuki et al., 2005) ùkü. š d 1.5 m (Inoue and Choi, 2006) š.»(return period) š d 7 ka (Inoue and Choi, 2006) ~ 10 ka (Suzuki et al., 2005), š d 15 ka (Inoue and Choi, 2006). d w k w ÿ ¾ 4» d y (», y, )» w w» ƒ w, x y, xw, ƒ v w. ³ sƒ Slimmons (1982) d y d w» (maximum earthquake or maximum credible earthquake) ³ w, š y, d w, d ¼ w w. ù t w, ³ š, vw w t w» wš 4» z» d w ³ d y sƒw». ³ w e d š, j ³ wš t y ³ w mw, ü 4» z» d ƒ w ³ w š w. y»ƒ ¼» ³ w» d w.,» d w w, xw d p w w» d p w w. ³ ³ w 2 1 d ( t q ¼ ) l w,., w ( : Bonilla et al., 1984; Wells and Coppersmith, 1994), t q ¼ w ( : Slemmons, 1982; Bonilla et al., 1984; Khromovskikh, 1989; Wells and Coppersmith, 1994), s³ w ( : Kanamori, 1977), tq ¼ (L) (D) w ( : (Slemmons, 1982; Bonilla et al., 1984; Mason, 1992), q w ( : Wells and Coppersmith, 1994). ù ƒ ³ w y ü. (maximum displacement) w w d ³ x k. x ¾ ³ w x š, d w š. t q ¼ w ³ ƒ tq ¼ (surface rupture length) ³ w. t q ¼ d ƒ y ü., ƒ q ¼ ó w ù, d q w ù k,,,»k w ó w ù,, f (curves), (overlap) d»w ³e sw ù. tq ¼ (L) (D) w L D w w w w k ƒ. (Slemmons, 1982; Bonilla et al., 1984) log LD w Ms z ƒ L D ƒƒ w z
ûw û š ³ sƒ 193 Table 4. Empirical formula between maximum displacement (D) and magnitude (M). Authors Relations Yangsan F.Z. (Yuge fault) D=1.0 m Ulsan F.Z. (Galgok fault) D=1.6 m Data range or Remark Iida (1965, All) logd(m)=0.55m 3.71 6.7 7.1 M: 6.6 ~ 8.6, WW Slemmons (1982. R) Ms = 6.793 + 1.306logD(m) 6.8 7.1 M: 5.9 ~ 7.7, D: 0.3 ~ 4 m, WW Slemmons (1982, R+SS) Ms = 6.944 + 0.856logD(m) 6.9 7.1 WW Bonilla et al. (1984, All) Ms = 6.95 + 0.723logD(m) 7.0 7.1 WW Bonilla et al. (1984, All) Ms = 6.93 + 0.665logD(m) 6.9 7.1 plate interiors Wells & Coppersmith (1994, R) Mw = 6.52 + 0.44logD(m) 6.5 6.6 M: 4 ~ 7.4, D: 0.11 ~ 6.5 m, WW Wells & Coppersmith (1994, All) Mw = 6.69 + 0.74logD(m) 6.7 6.8 M: 5.2 ~ 8.1, D: 0.01 ~ 14.6 m, WW Average 6.8 7.0 Maximum 7.0 7.1 Minimum 6.5 6.6 *R reverse fault, SS strike slip fault, All all fault types, WW: worldwide data ƒ w. Mason(1992) LD z ƒ q ¼ ³ ùkü ³ j ùkü» w š w. s³ w p d ƒ s³ w (average subsurface displacement) x w» w. Wells and Coppersmith (1994) pƒ œ s³ w 76% š s³ w s³ t 132%. q ³ œ s l q x w (Wells and Coppersmith, 1994). w q ¼ ù ww w s w w. ³ sƒ sƒw, ù y d w x w. tq ¼ ù q y ü w». ƒ d p e, mw w. 4» z» d w» w ù, 1z d» w w d w. d d p e, mw Holocene alluvial gravel 0.5 m, d 1.0 m ùkü (Kyung, 2003), ½ Ÿ (2006) d d w ³ 6.5 ~ 7.5 w. š d p e mw 0.8 m, 1.6 m (Suzuki et al., 2005;, 2007). š ƒ w ³ sƒ -³ x (Table 4) x d ƒ w w w. Table 4 œ w s³ w, ³ d s³ 6.8, š d 7.0. š d w š (Paleo-earthquakes) ù 2000 w (Historical earthquakes) sƒw» y w. Table 5 w vw». vw d t rupture w ƒ. w sƒ ³ (Lee and Yang, 2006) š s ƒ ³ j ùkü. ù, x ¾ d mw t ù xw w. NNE-SSW w NNW-SSE ü N-S w ƒ w m wš. Table 5 Fig. 4 vw d w x w. 1643 (Fig. 5) w ƒ j, x» t x ù d xw ƒ. t ù rupture evidenceƒ, ù y w ƒ.
194 Table 5. Major historical earthquakes occurred around the Yangsan and Ulsan fault zones. No. year/month/day Latitude Longitude Description of damages Intensity Magnitude M L (Lee & Yang, 2006) (Lee & Yang, 2006) 1 100/10/ 35.8 129.3. ƒ, vw VIII-IX 6.7 2 304/9/ 35.8 129.3. ƒ, vw VIII-IX 6.7 3 510/5/ 35.8 129.3. ƒ, vw VIII-IX 6.7 4 779/3/ 35.8 129.3. ƒ, vw 100 VIII-IX 6.7 5 1036/7/23 35.8 129.3. ƒ {, û, w VIII 6.4, ƒk, 3 6 1643/7/24 35.5 129.5 2.,, ½w, š : y Á VIII-IX 6.7. :, t ³, (6œ), Á Fig. 5. Location and felt area of damaging earthquakes (MMI VIII- IX) which occurred Ulsan city in July 24, 1643. Solid and broken lines indicate the estimated felt area corresponding to MMI VI-VII and II-III, respectively. Fig. 4. Location of damaging earthquakes (MMI VIII-IX) which occurred Kyungju city in A.D. 100, 304, 510 and 779 (a), and 1036 (b). Broken line indicates the estimated felt area corresponding to MMI II-III. 4» z» z š y d š w d(, ) ù kù, ƒ w k w ƒ. w vw ù y y w œ p w š sw ƒ w. w 4» z» d w 1994 z ƒ w w š. x ¾ d w 4» z
ûw û š ³ sƒ 195» d mw x š y ww w. ƒ., ¼ d d sww d sw,, -m š y ùküš, ƒ z d». 4»z» d w ƒ d w ùkú ƒ ƒw. x ¾ w», š, ƒ y»ƒ ƒ. ù. d û wš d» ùkù. d p w w, w. wš d ƒ w.. š w d wš 20». wr,» 30 z ¾ ¾» ùkù, ¾ y w š.. s³ mw d y sƒw w, s³ 0.1 ~ 0.04 m/ka C w w, s³ 0.2 ~ 0.06 m/ka B-C w w.. ƒ d ³ x» w sƒw ³ d s³ 6.8, š d 7.0. ù vw w t w» wš ³ d sƒw ƒ., sƒ x sƒw w y ü..» d, d š d 7 ka, š d 15 ka ¼» ùkü. d š w w w» w y w d p zywš d ¼, ƒ, d, s³,» ³, ³ w. p, y», s³ ƒ w, š y z w. d 4» n d sƒ š w sw» 4» d ³ w š». w, d sw 4» d, p w w w š. OSL,, C 14, Loess d w š,, d, d ƒ š. w mw 4» d w m d ƒ y w. vw w w, xw üš,» d ³ w d š w w w š w. 4» d e d w w œw w». w w 2010w KNUE w ww, w, CATER 2008-5402 w w. š x, 2002, û» d w p e, w œwz, w y wz, w k wz, w wz 2002 œ w tz, 293-297., 2007, 4» z» z š w p, w 3y, w, 105-117.,»y, Okada, A., Watanabe, M., Suzuki Y., and Takemura, K., 1999a, û p e w dp ³, wz, 20, 101-110.,»y, Okada, A., 1999b, š w x p e., 3, 155-168., k, 2001,» d, wz, 37, 563-577. ½, Ÿ, 2006, p e d w w d ³, wz, 42, 79-94.,,,,,,, 2002, š 4» d, wz, 38, 309-323.,, ½, k, 2001, 1 4» ( ), w wz œ w tz, 65p., 2006, w û 4» d, w w w w, 382p., y, 1999, w û y d x, w wz, 34, 231-246. «, 2002, d w, w, w» KINS/HR-474, 42p. «, 2003, d w, w,
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