scholarly journals Benefits of Defining Geological Sensitive Zones in the Mitigation of Disasters Along Earthquake Fault Zones in Taiwan – The Case of Milun Fault

2021 ◽  
Vol 16 (8) ◽  
pp. 1257-1264
Author(s):  
Tyan-Ming Chu ◽  
Wen-Jeng Huang ◽  
Tsung-Yi Lin ◽  
Shih-Ting Lu ◽  
Yen-Chiu Liu ◽  
...  
Keyword(s):  
Fault Zone ◽  
Urban Areas ◽  
Hanging Wall ◽  
Active Faults ◽  
Earthquake Hazards ◽  
Fault Line ◽  
Earthquake Fault ◽  
Before And After ◽  
Surface Ruptures ◽  
Recurrence Intervals

In Taiwan, the main purpose of earthquake fault zone legislation is to prevent earthquake-related disasters around the surface traces of active faults, particularly in urban areas. Here, the Geologically Sensitive Area (GSA) of the Milun Fault (Milun Earthquake Fault Zone) is used as an example to reveal the importance of such legislation. Field data collected along the Milun Fault before and after the 2018 Hualien Earthquake were used to reveal the reappearance of damages within the GSA. The 2018 Hualien Earthquake represents one of the shortest recurrence intervals (67 years) among all major faults in Taiwan. Most of the surface ruptures and damaged buildings in Hualien City were within the Milun Fault GSA and concentrated on the hanging wall of the fault. Moreover, 61% (91/148) of the damaged buildings and 83% (692/835) of the surface ruptures occurred within 100 m of the fault line. The results of this study demonstrate the importance of defining GSAs of active faults for mitigating earthquake hazards.

scholarly journals Evaluation of Dip Angles of Active Faults Beneath the Osaka Plain Inferred from a 2D Numerical Analysis of visco-elasto-plastic Models

2020 ◽  
Author(s):  
Hayami Nishiwaki ◽  
Takamoto Okudaira ◽  
Kazuhiko Ishii ◽  
Muneki Mitamura
Keyword(s):  
Fault Zone ◽  
Urban Areas ◽  
Active Faults ◽  
Three Dimensional ◽  
Seismogenic Zone ◽  
Earthquake Ground Motion ◽  
Convex Curve ◽  
Seismic Reflection Profile ◽  
Geological Structures ◽  
Dip Angle

Abstract The geometries (i.e., dip angles) of active faults from the surface to the seismogenic zone are among the most important factors used to evaluate earthquake ground motion, which is crucial to seismic hazard assessments in urban areas. In Osaka, a metropolitan city in Japan, there are several active faults (e.g., the Uemachi and Ikoma faults), which are inferred from the topography, the attitude of active faults in surface trenches, the seismic reflection profile at shallow depths (less than 2 km), and the three-dimensional distribution of the Quaternary sedimentary layers. The Uemachi and Ikoma faults are N–S-striking fault systems with total lengths of 42 km and 38 km, respectively, with the former being located ~12 km west of the latter; however, the geometries of each of the active faults within the seismogenic zone is not clear. In this study, to examine the geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone, we analyze the development of the geological structures of sedimentary layers based on numerical simulations of a two-dimensional visco-elasto-plastic body under a horizontal compressive stress field, including preexisting linear high-strained weak zones (i.e., faults) and surface sedimentation processes, and evaluate the relationship between the observed geological structures of the Quaternary sediments (i.e., the Osaka Group) in the Osaka Plain and the model results. Based on a comparison between the simulation results and the geological observations/interpretation, we propose geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone. When the friction coefficient of the faults is ~0.5, the dip angles of the Uemachi and Ikoma faults near the surface are ~30°–40° and the Uemachi fault has a downward convex curve at the bottom of the seismogenic zone but does not converge to the Ikoma fault. Based on the analysis in this study, the dip angle of the Uemachi fault zone is estimated to be approximately 30°–40°, and the downward extension of the Uemachi fault zone nearly coincides with the epicenter of the 2018 northern Osaka earthquake.

scholarly journals Seismic Response of a Water Transmission Pipeline Across a Fault Zone Adopting a Large-Scale Vibration Table Test

2021 ◽  
Vol 9 ◽  
Author(s):  
Longsheng Deng ◽  
Wenzhong Zhang ◽  
Yan Dai ◽  
Wen Fan ◽  
Yubo Li ◽  
...  
Keyword(s):  
Seismic Response ◽  
Fault Zone ◽  
Large Scale ◽  
Hanging Wall ◽  
Active Faults ◽  
Dynamic Responses ◽  
Soil Pressure ◽  
Geologic Hazard ◽  
Amplification Ratio ◽  
Design And Construction

The seismic response is generally amplified significantly near the fault zone due to the influence of discontinuous interfaces and weak-broken geotechnical structures, which imposes a severe geologic hazard risk on the engineering crossing the fault. The Hanjiang to Weihe River Project (phase II) crosses many high seismic intensity regions and intersects with eight large-scale regional active faults. Seismic fortification of the pipelines across the fault zone is significant for the design and construction of the project. A large-scale vibration table test was adopted to investigate the seismic response and fault influences. The responses of accelerations, dynamic stresses, strains, and water pressures were obtained. The results show that the dynamic responses were amplified significantly by the fault zone and the hanging wall. The influence range of fault on acceleration response is approximately four times the fault width. The acceleration amplification ratio in the fault zone generally exceeds 1.35, even reaching 1.8, and the hanging wall amplification ratio is approximately 1.2. The dynamic soil pressure primarily depends on the acceleration distribution and is apparently influenced by pipeline location and model inhomogeneity. The pipeline is bent slightly along the axial direction, accompanied by expansion and shrinkage in the radial direction. The maximum tensile and compressive strains appear at the lower and upper pipeline boundaries near the middle section, respectively. Massive y-direction cracks developed in the soil, accompanied by slight seismic subsidence. The research findings could provide reasonable parameters for the seismic design and construction of the project.

scholarly journals Earthquake Hazards of the Grand Teton National Park Emphasizing the Teton Fault

1987 ◽  
Vol 11 ◽  
pp. 106-130
Author(s):  
D. Susong ◽  
R. Smith ◽  
R. Bruhn
Keyword(s):  
Fault Zone ◽  
Gravity Data ◽  
Hanging Wall ◽  
Regional Scale ◽  
Normal Fault ◽  
Earthquake Hazards ◽  
Eastern Front ◽  
The North ◽  
Teton Range ◽  
Structural Boundary

The Teton normal-fault zone extends for over 80 km along the eastern front of the Teton Range. Mapping and profiling of Quaternary fault scarps shows that the scarps are nearly continous for 55 km with scarp heights varying from about 10 m to 40 m. The largest scarps occur adjacent to the topographically highest parts of the Teton range. The scarps locally offset glacial moraine crests in a left-lateral sense. On a regional scale the scarps exhibit a right-stepping, en echelon geometry that is also consistent with a component of left-lateral displacenent. The Teton fault is structurally subdivided into three segments. One prominent geometrical segment boundary occurs just south Taggart Lake, where the range front bends through an angle of 23° and a major structural boundary extends through the hanging wall basin, as inferred by gravity data. This boundary may have influenced the history of Quaternary earthquake occurrences because vertical offset across faults scarps is greater to the north of the boundary, than to the south. The lengths of the proposed segments and scarp size are consistent with M7 to 7.5 earthquakes for the Teton fault zone.

Criteria for Surface Rupture Microzonation of Active Faults for Earthquake Hazards in Urban Areas

2018 ◽  
pp. 187-230
Author(s):  
Hasan Sözbilir ◽  
Çağlar Özkaymak ◽  
Bora Uzel ◽  
Ökmen Sümer
Keyword(s):  
Land Use Planning ◽  
Urban Areas ◽  
Active Faults ◽  
Earthquake Hazard ◽  
Disaster Mitigation ◽  
Rupture Zone ◽  
Earthquake Hazards ◽  
Surface Rupture ◽  
Earthquake Hazard Assessment ◽  
Earthquake Effects

Formation of surface rupture zone along active faults buried directly beneath major cities create devastating earthquakes that seriously threaten the safety of human lives. Surface rupture microzonation (SRM) is the generic name for subdividing a region into individual areas having different potentials hazardous earthquake effects, defining their specific seismic behavior for engineering design and land-use planning in case a large devastating earthquake strikes the region. The basis of SRM is to model the rupture zone at the epicenter of an earthquake, and thus develop a hazard-avoid map indicating the vulnerability of the area to potential seismic hazard. Earthquake hazard assessment of active faults in urban areas are thus an important systematic engineering for disaster mitigation in major cities.

scholarly journals Geotechnical data synthesis for GIS-based analysis of fault zone geometry and hazard in an urban environment

Geosphere ◽  
2019 ◽  
Vol 15 (6) ◽  
pp. 1999-2017
Author(s):  
Luke Weidman ◽  
Jillian M. Maloney ◽  
Thomas K. Rockwell
Keyword(s):  
Fault Zone ◽  
Urban Areas ◽  
San Diego ◽  
Regional Scale ◽  
Active Faults ◽  
High Volume ◽  
Fault Zones ◽  
Small Scale ◽  
Fault Geometry ◽  
Geotechnical Data

Abstract Many fault zones trend through developed urban areas where their geomorphic expression is unclear, making it difficult to study fault zone details and assess seismic hazard. One example is the Holocene-active Rose Canyon fault zone, a strike-slip fault with potential to produce a M6.9 earthquake, which traverses the city of San Diego, California (USA). Several strands trend through densely populated areas, including downtown. Much of the developed environment in San Diego predates aerial imagery, making assessment of the natural landscape difficult. To comply with regulations on development in a seismically active area, geotechnical firms have conducted many private, small-scale fault studies in downtown San Diego since the 1980s. However, each report is site specific with minimal integration between neighboring sites, and there exists no resource where all data can be viewed simultaneously on a regional scale. Here, geotechnical data were mined from 268 individual reports and synthesized into an interactive geodatabase to elucidate fault geometry through downtown San Diego. In the geodatabase, fault segments were assigned a hazard classification, and their strike and dip characterized. Results show an active zone of discontinuous fault segments trending north-south in eastern downtown, including active faults outside the mapped regulatory Earthquake Fault Zone. Analysis of fault geometry shows high variability along strike that may be associated with a stepover into San Diego Bay. This type of geodatabase offers a method for compiling and analyzing a high volume of small-scale fault investigations for a more comprehensive understanding of fault zones located in developed regions.

scholarly journals Dip angles of active faults from the surface to the seismogenic zone inferred from a 2D numerical analysis of visco-elasto-plastic models: a case study for the Osaka Plain

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hayami Nishiwaki ◽  
Takamoto Okudaira ◽  
Kazuhiko Ishii ◽  
Muneki Mitamura
Keyword(s):  
Urban Areas ◽  
Active Faults ◽  
Three Dimensional ◽  
Seismogenic Zone ◽  
Earthquake Ground Motion ◽  
Convex Curve ◽  
Seismic Reflection Profile ◽  
Geological Structures ◽  
Dimensional Distribution ◽  
Dip Angle

AbstractThe geometries (i.e., dip angles) of active faults from the surface to the seismogenic zone are the most important factors used to evaluate earthquake ground motion, which is crucial for seismic hazard assessments in urban areas. In Osaka, a metropolitan city in Japan, there are several active faults (e.g., the Uemachi and Ikoma faults), which are inferred from the topography, the attitude of active faults in surface trenches, the seismic reflection profile at shallow depths (less than 2 km), and the three-dimensional distribution of the Quaternary sedimentary layers. The Uemachi and Ikoma faults are N–S-striking fault systems with total lengths of 42 km and 38 km, respectively, with the former being located ~ 12 km west of the latter; however, the geometries of each of the active faults within the seismogenic zone are not clear. In this study, to examine the geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone, we analyze the development of the geological structures of sedimentary layers based on numerical simulations of a two-dimensional visco-elasto-plastic body under a horizontal compressive stress field, including preexisting high-strained weak zones (i.e., faults) and surface sedimentation processes, and evaluate the relationship between the observed geological structures of the Quaternary sediments (i.e., the Osaka Group) in the Osaka Plain and the model results. As a result, we propose geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone. When the friction coefficient of the faults is ~ 0.5, the dip angles of the Uemachi and Ikoma faults near the surface are ~ 30°–40° and the Uemachi fault has a downward convex curve at the bottom of the seismogenic zone, but does not converge to the Ikoma fault. Based on the analysis in this study, the dip angle of the Uemachi fault zone is estimated to be approximately 30°–40°, which is lower than that estimated in the previous studies. If the active fault has a low angle, the width of the fault plane is long, and thus the estimated seismic moment will be large.

scholarly journals Driving stress and seismotectonic implications of the 2013 Mw5.8 Awaji Island earthquake, southwestern Japan, based on earthquake focal mechanisms before and after the mainshock

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Kazutoshi Imanishi ◽  
Makiko Ohtani ◽  
Takahiko Uchide
Keyword(s):  
Stress Field ◽  
Stress Tensor ◽  
Nankai Trough ◽  
Source Region ◽  
Local Scale ◽  
Southwest Japan ◽  
Stress Tensor Inversion ◽  
Earthquake Fault ◽  
Reverse Faulting ◽  
Before And After

Abstract A driving stress of the Mw5.8 reverse-faulting Awaji Island earthquake (2013), southwest Japan, was investigated using focal mechanism solutions of earthquakes before and after the mainshock. The seismic records from regional high-sensitivity seismic stations were used. Further, the stress tensor inversion method was applied to infer the stress fields in the source region. The results of the stress tensor inversion and the slip tendency analysis revealed that the stress field within the source region deviates from the surrounding area, in which the stress field locally contains a reverse-faulting component with ENE–WSW compression. This local fluctuation in the stress field is key to producing reverse-faulting earthquakes. The existing knowledge on regional-scale stress (tens to hundreds of km) cannot predict the occurrence of the Awaji Island earthquake, emphasizing the importance of estimating local-scale (< tens of km) stress information. It is possible that the local-scale stress heterogeneity has been formed by local tectonic movement, i.e., the formation of flexures in combination with recurring deep aseismic slips. The coseismic Coulomb stress change, induced by the disastrous 1995 Mw6.9 Kobe earthquake, increased along the fault plane of the Awaji Island earthquake; however, the postseismic stress change was negative. We concluded that the gradual stress build-up, due to the interseismic plate locking along the Nankai trough, overcame the postseismic stress reduction in a few years, pushing the Awaji Island earthquake fault over its failure threshold in 2013. The observation that the earthquake occurred in response to the interseismic plate locking has an important implication in terms of seismotectonics in southwest Japan, facilitating further research on the causal relationship between the inland earthquake activity and the Nankai trough earthquake. Furthermore, this study highlighted that the dataset before the mainshock may not have sufficient information to reflect the stress field in the source region due to the lack of earthquakes in that region. This is because the earthquake fault is generally locked prior to the mainshock. Further research is needed for estimating the stress field in the vicinity of an earthquake fault via seismicity before the mainshock alone.

scholarly journals Surface-Rupturing Historical Earthquakes in Australia and Their Environmental Effects: New Insights from Re-Analyses of Observational Data

Geosciences ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 408 ◽  
Author(s):  
King ◽  
Quigley ◽  
Clark
Keyword(s):  
Observational Data ◽  
Environmental Effects ◽  
Active Faults ◽  
Magnetic Data ◽  
Future Research ◽  
Surface Rupture ◽  
Secondary Fracture ◽  
Geological Evidence ◽  
Surface Ruptures ◽  
Strong Control

We digitize surface rupture maps and compile observational data from 67 publications on ten of eleven historical, surface-rupturing earthquakes in Australia in order to analyze the prevailing characteristics of surface ruptures and other environmental effects in this crystalline basement-dominated intraplate environment. The studied earthquakes occurred between 1968 and 2018, and range in moment magnitude (Mw) from 4.7 to 6.6. All earthquakes involved co-seismic reverse faulting (with varying amounts of strike-slip) on single or multiple (1–6) discrete faults of ≥ 1 km length that are distinguished by orientation and kinematic criteria. Nine of ten earthquakes have surface-rupturing fault orientations that align with prevailing linear anomalies in geophysical (gravity and magnetic) data and bedrock structure (foliations and/or quartz veins and/or intrusive boundaries and/or pre-existing faults), indicating strong control of inherited crustal structure on contemporary faulting. Rupture kinematics are consistent with horizontal shortening driven by regional trajectories of horizontal compressive stress. The lack of precision in seismological data prohibits the assessment of whether surface ruptures project to hypocentral locations via contiguous, planar principal slip zones or whether rupture segmentation occurs between seismogenic depths and the surface. Rupture centroids of 1–4 km in depth indicate predominantly shallow seismic moment release. No studied earthquakes have unambiguous geological evidence for preceding surface-rupturing earthquakes on the same faults and five earthquakes contain evidence of absence of preceding ruptures since the late Pleistocene, collectively highlighting the challenge of using mapped active faults to predict future seismic hazards. Estimated maximum fault slip rates are 0.2–9.1 m Myr-1 with at least one order of uncertainty. New estimates for rupture length, fault dip, and coseismic net slip can be used to improve future iterations of earthquake magnitude—source size—displacement scaling equations. Observed environmental effects include primary surface rupture, secondary fracture/cracks, fissures, rock falls, ground-water anomalies, vegetation damage, sand-blows / liquefaction, displaced rock fragments, and holes from collapsible soil failure, at maximum estimated epicentral distances ranging from 0 to ~250 km. ESI-07 intensity-scale estimates range by ± 3 classes in each earthquake, depending on the effect considered. Comparing Mw-ESI relationships across geologically diverse environments is a fruitful avenue for future research.

scholarly journals Active Fault Systems in the Inner Northwest Apennines, Italy: A Reappraisal One Century after the 1920 Mw ~6.5 Fivizzano Earthquake

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 139
Author(s):  
Giancarlo Molli ◽  
Isabelle Manighetti ◽  
Rick Bennett ◽  
Jacques Malavieille ◽  
Enrico Serpelloni ◽  
...  
Keyword(s):  
Large Scale ◽  
Active Fault ◽  
Active Faults ◽  
Dense Network ◽  
Earthquake Fault ◽  
Slip Rates ◽  
Fault Systems ◽  
Seismological Data ◽  
Seismogenic Faults

Based on the review of the available stratigraphic, tectonic, morphological, geodetic, and seismological data, along with new structural observations, we present a reappraisal of the potential seismogenic faults and fault systems in the inner northwest Apennines, Italy, which was the site, one century ago, of the devastating Mw ~6.5, 1920 Fivizzano earthquake. Our updated fault catalog provides the fault locations, as well as the description of their architecture, large-scale segmentation, cumulative displacements, evidence for recent to present activity, and long-term slip rates. Our work documents that a dense network of active faults, and thus potential earthquake fault sources, exists in the region. We discuss the seismogenic potential of these faults, and propose a general tectonic scenario that might account for their development.

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