Geomorphic and stratigraphic records of paleoearthquakes on the Yangsan Fault and Ulsan Fault, SE Korea
- Abstract
- Earthquake is one of the powerful natural disasters that cause human and socio damages. Understanding behavioral characteristics support crucial information for seismic mitigation hazards. Previous paleoseismic research has mainly targeted the tectonically active regions (interplate). However, a large magnitude of earthquakes occurs within intraplate conditions. Recently, interest in earthquakes within the intraplate has been increasing, and the study of intraplate faults has begun. It was known to the random spatio-temporal characteristic of slip under the intraplate fault, compared with interplate regimes. However, according to recent reports, intraplate faults have constant recurrence intervals of slip, but only difficult to find their evidence because they have long-periodic cycles.
The Korean Peninsula is located within the Eurasian Plate; there has been no report about surface rupturing earthquakes since from installation of the modern seismometer. However, historical and paleoseismological studies reported large earthquakes with surface rupture in the Korean peninsula in the prehistoric period. After experiencing the Gyeongju earthquake (12th of September 2016; Mw5.5) and Pohang earthquake (15th of November 2017; Mw5.4), seismic and paleoseismic research are highlighted by geoscientists but also the nation people of Korea. I conducted paleoseismic studies along the Yangsan Fault and Ulsan Fault, the southeastern part of the Korean peninsula, during my Ph.D. Here, I found geomorphological and stratigraphical surface rupturing paleoearthquakes and discussed with pre-reported paleoseismic studies along the Yangsan Fault and Ulsan Fault.
The Yangsan Fault is NNE-SSW trending mature dextral strike-slip fault with about 200 km-long, and the Ulsan Fault is NNW-SSE trending reverse dominant oblique-slip fault with about 50 km-long. I confirmed geomorphology related to strike-slip faulting along the Yangsan Fault and calculated about 0.3-0.4 mm/yr lateral slip rate of the Bangok section (CHAPTER2). Also, I proposed a rupture scenario through the most recent earthquake timing and penultimate earthquake timing derived from three trench investigations along the Yangsan Fault (CHAPTER3). I could not find slip evidence during the Holocene along this section. Vertical steps about 10-20 m on the alluvial fan surfaces developed along the Ulsan Fault, and I interpreted these geomorphic features caused by cumulative slip along the eastern dipping reverse fault based on field observations geophysical survey (CHAPTER4). Also, I reported the youngest earthquake event along the Ulsan Fault at the Wonwonsa 2nd site (CHAPTER5). In CHAPTER6, I discussed my results with previous studies and found two meaningful features about paleoseismic features along the Yangsan Fault and Ulsan Fault. First, the northern part of the Yangsan Fault and Ulsan Fault slipped during the Holocene, but the southern part of the Yangsan Fault did not slip during the Holocene. Second, the lateral slip rate of the Yangsan Fault is slightly faster than the vertical slip rate of the Ulsan Fault. I discussed controlling factors for this phenomenon and recommended directions for future studies.
- Issued Date
- 2022
- Awarded Date
- 2022. 2
- Type
- Dissertation
- Publisher
- 부경대학교
- Affiliation
- 부경대학교 대학원
- Department
- 대학원 지구환경시스템과학부지구환경과학전공
- Advisor
- 김영석
- Table Of Contents
- CHAPTER 1. Introduction 1
1.1 Motivation and objectives 1
1.2 Framework of this study 5
1.3 Scope of this study 8
1.4 Overview and background of thesis 10
1.5 References 12
CHAPTER 2. Long-term lateral slip rate of the intraplate strike-slip fault: a case study of the Yangsan Fault, SE Korea 17
Abstract 17
2.1. Introduction 18
2.2. Study area 21
2.3. Methodology 24
2.3.1. Geomorphic analysis 24
2.3.2. Field survey 25
2.3.3. Cosmogenic nuclides burial dating 26
2.4. Results 28
2.4.1. Geomorphic characteristics of the alluvial fan 28
2.4.2. Field evidence for the paleoearthquakes 30
2.4.3. Burial age of the fan deposit 37
2.5. Discussion 38
2.5.1. Cumulative lateral offset and long-term slip rate 38
2.5.2. Comparison with the central-southern YSF 42
2.6. Conclusions 46
2.7. References 47
CHAPTER 3. Stratigraphic Constraints of Rupture Kinematics and Scenarios of Paleoearthquakes on the Southern Yangsan Fault, SE Korea 58
Abstract 58
3.1. Introduction 59
3.2. Study area 64
3.2.1. Seismotectonic setting 64
3.2.2. The Yangsan Fault 65
3.2.3. Inbo trench 67
3.3. Methods 67
3.3.1. Fault tracing and trench locations 67
3.3.2. Trench excavation 68
3.3.3. Geochronology 69
3.4. Results 71
3.4.1. WS trench 71
3.4.2. MH trench 76
3.4.3. IBN trench 81
3.5. Discussion 85
3.5.1. Stratigraphic features related to fault splay kinematics 85
3.5.2. Rupture scenarios for the northern section of the southern Yangsan Fault 88
3.6. Conclusions 92
3.7. References 94
CHAPTER 4. A study on the topographical deformation characteristics of the central part of Ulsan fault 105
Abstract 105
4.1. Introduction 106
4.2. Topography and Geology 111
4.2.1. Topography 111
4.2.2. Geology and structures 112
4.3. Methodology 118
4.4. Results 120
4.4.1. Topographical analysis 120
4.4.2. Geophysical survey: Electric resistivity tomography (ERT) 124
4.4.3. Field observation 126
4.5. Discussions 132
4.5.1. Topographical anomalies and fault activity 132
4.5.2. Timing and slip rate 134
4.6. Conclusions 136
4.7. References 138
CHAPTER 5. Kinematic characteristics and earthquake timing of the Wonwonsa fault in the central Ulsan fault 145
Abstract 145
5.1. Introduction 146
5.2. Geomorphology and geologic settings 149
5.2.1. Geomorphic settings 149
5.2.2. Geologic settings 150
5.3. Methods 153
5.4. Results 155
5.4.1. Characteristics of the Quaternary fault 155
5.4.2. Geochronology 157
5.4.3. Fault parameters 160
5.5. Discussions 162
5.5.1. Comparisons between Quaternary faults along the Ulsan fault 162
5.5.2. Reversed age dating 164
5.6. Conclusions 166
5.7. References 167
CHAPTER 6. Concluding remarks 177
6.1. Most recent earthquake timing along the Yangsan Fault and Ulsan Fault 178
6.1.1. Data acquisition and most recent earthquake timing 178
6.1.2. Possible controlling factors for earthquake timing result 180
6.2. Slip rate along the Yangsan Fault and Ulsan Fault 185
6.2.1. Data acquisition and slip rate 185
6.2.2. Possible controlling factors for slip rate 187
6.3. Limitation for paleoseismic study in intraplate region and recommendations for future works 189
6.4. References 192
Summary (in Korean) 198
Acknowledgment (in Korean) 201
- Degree
- Doctor
- Appears in Collections:
- 대학원 > 지구환경시스템과학부-지구환경과학전공
- Files in This Item:
-
-
There are no files associated with this item.
-
Items in Repository are protected by copyright, with all rights reserved, unless otherwise indicated.