scholarly journals Morphotectonic Kinematic Indicators along the Vigan-Aggao Fault: The Western Deformation Front of the Philippine Fault Zone in Northern Luzon, the Philippines

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 83 ◽  
Author(s):  
Rolly E. Rimando ◽  
Jeremy M. Rimando
Keyword(s):  
Fault Zone ◽  
Active Fault ◽  
Active Faults ◽  
Vertical Component ◽  
The Philippines ◽  
Google Earth ◽  
Fault System ◽  
Philippine Sea Plate ◽  
Oblique Convergence ◽  
Philippine Fault Zone

The Vigan-Aggao Fault is a 140-km-long complex active fault system consisting of multiple traces in the westernmost part of the Philippine Fault Zone (PFZ) in northern Luzon, the Philippines. In this paper, its traces, segmentation, and oblique left-lateral strike-slip motion are determined from horizontal and vertical displacements measured from over a thousand piercing points pricked from displaced spurs and streams observed from Google Earth Pro satellite images. This work marks the first instance of the extensive use of Google Earth as a tool in mapping and determining the kinematics of active faults. Complete 3D image coverage of a major thoroughgoing active fault system is freely and easily accessible on the Google Earth Pro platform. It provides a great advantage to researchers collecting morphotectonic displacement data, especially where access to aerial photos covering the entire fault system is next to impossible. This tool has not been applied in the past due to apprehensions on the positional measurement accuracy (mainly of the vertical component). The new method outlined in this paper demonstrates the applicability of this tool in the detailed mapping of active fault traces through a neotectonic analysis of fault-zone features. From the sense of motion of the active faults in northern Luzon and of the major bounding faults in central Luzon, the nature of deformation in these regions can be inferred. An understanding of the kinematics is critical in appreciating the distribution and the preferred mode of accommodation of deformation by faulting in central and northern Luzon resulting from oblique convergence of the Sunda Plate and the Philippine Sea Plate. The location, extent, segmentation patterns, and sense of motion of active faults are critical in coming up with reasonable estimates of the hazards involved and identifying areas prone to these hazards. The magnitude of earthquakes is also partly dependent on the type and nature of fault movement. With a proper evaluation of these parameters, earthquake hazards and their effects in different tectonic settings worldwide can be estimated more accurately.

scholarly journals A photogrametric study on active faults in the Nepal Himalayas

1982 ◽  
Vol 2 ◽  
pp. 67-80
Author(s):  
Takashi Nakata
Keyword(s):  
Active Fault ◽  
Late Quaternary ◽  
Lateral Displacement ◽  
Active Faults ◽  
Aerial Photographs ◽  
Fault System ◽  
Lateral Movement ◽  
Active Faulting ◽  
Quaternary Period ◽  
Late Quaternary Period

Active faults in the Nepal Himalayas are identified by means of interpretation of vertical aerial photographs. They are mainly distributed along the major tectonic lines as older geological faults and are classified into four groups, the Main Central Active Fault system, the active faults in the Lower Himalayas, the Main Boundary Active Fault system and active faults along the Himalayan Front Fault. The mode of active faulting is closely related to the strikes of the faults. Along the NW-SE and NE-SW trending faults, lateral displacement with northward drop is prevailing, and right-lateral movement along the former and left-lateral movement along the latter is a rule in the sense of displacements. On the other hand, dip-slip faulting is observed mainly along the E-W trending faults belonging to the Main Boundary Active Fault system. However, apparent displacement along the faults is mostly of northward drop. It is considered that active faulting along the major tectonic lines except the Himalayan Front Fault does not favor the upheaval of the Himalayan ranges during the late Quaternary period.

scholarly journals Measurements of tectonic micro-displacements within the Idrija fault zone in the Učja valley (W Slovenia)

2020 ◽  
Vol 60 (1) ◽  
Author(s):  
Andrej Gosar
Keyword(s):  
Fault Zone ◽  
Active Fault ◽  
Average Rate ◽  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Vertical Displacements ◽  
Recent Activity ◽  
Insight Into ◽  
Horizontal Displacements

A recent slip-rate of an active fault is a very important seismotectonic parameter, but not easy to determine. Idrija fault, 120 km long, is a prominent geomorphologic feature with large seismogenic potential, still needed to be researched. Measurements of tectonic micro-displacements can provide insight into its recent activity. The Učja valley extends transversally to the Idrija fault and was therefore selected for the installation of TM 71 extensometer. Measurements on the crack within its inner fault zone are conducted from the year 2004. In 14 years of observations a systematic horizontal displacements with average rate of 0.21 mm/year and subordinate vertical displacements of 0.06 mm/year were established, proving the activity of this fault. An overview of methods of displacement measurements related to active faults and of newer interdisciplinary investigations of the Idrija fault is given. Displacement rates are beside for geodynamic interpretations important for improvement of seismotectonic models and thus for better seismic hazard assessment.

scholarly journals Inter-episodes earthquake migration in the Bohai-Zhangjiakou Fault Zone, North China: Insights from numerical modeling

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0251606
Author(s):  
Bo Shao ◽  
Guiting Hou ◽  
Jun Shen
Keyword(s):  
Fault Zone ◽  
North China ◽  
Active Fault ◽  
Active Faults ◽  
Element Model ◽  
Low Velocity ◽  
Tangshan Earthquake ◽  
Seismic Migration ◽  
Stress Changes ◽  
Earthquake Migration

In this paper, we focus on why intraplate seismic initiation and migration occurs, which has widely been considered to be caused by static stress triggering caused by earthquakes, as well as post-seismic slips. To illustrate the mechanism underlying large earthquakes, in particular the migration caused by two key episodes that occurred after 1500 in the Bohai-Zhangjiakou Fault Zone (BZFZ) of North China, we developed a high-resolution three-dimensional viscoelastic finite element model that includes the active faults with vertical segmentation, their periodical locking, and the lithosphere heterogeneity. We used the birth and death of element groups to simulate stress intensity changes during the two episodes (named Episode I and II), with our results showing that the Tangshan earthquake was primarily triggered by the Sanhe-Pinggu M8.0 earthquake in 1679, whereas the Zhangbei M6.2 earthquake in 1998 was not triggered by earthquakes in Episode I. According to our work, the calculated stress changes in the different segments of the fault zone correspond to the magnitude of the triggered earthquakes. Further, the largest stress decrease was near the Sanhe-Pinggu fault and occurred the largest earthquake in Episode I, whereas the largest stress increase was near the Tangshan fault and occurred during the largest earthquake in Episode II. Given the above, we propose a model for seismic migration to describe the dynamic mechanisms of earthquake migration within the BZFZ and North China, in which the factors affecting both the seismic migration path and intensity primarily include the distance between the triggered active fault and the original fault, the coupling of the active faults, the location and scale of the low-velocity anomaly, its distance from the active fault, and the location and scale of the crustal thinning.

scholarly journals Active faults sources for the Pátzcuaro–Acambay fault system (Mexico): fractal analysis of slip rates and magnitudes <i>M</i><sub>w</sub> estimated from fault length

2018 ◽  
Vol 18 (11) ◽  
pp. 3121-3135
Author(s):  
Avith Mendoza-Ponce ◽  
Angel Figueroa-Soto ◽  
Diana Soria-Caballero ◽  
Víctor Hugo Garduño-Monroy
Keyword(s):  
Time Domain ◽  
Fractal Analysis ◽  
Active Faults ◽  
Slip Rate ◽  
Spatial Domain ◽  
Fault System ◽  
Slip Rates ◽  
Oblique Convergence ◽  
Definition Of ◽  
Intrinsic Definition

Abstract. The Pátzcuaro–Acambay fault system (PAFS), located in the central part of the Trans-Mexican Volcanic Belt (TMVB), is delimited by an active transtensive deformation area associated with the oblique subduction zone between the Cocos and North American plates, with a convergence speed of 55 mm yr−1 at the latitude of the state of Michoacán, Mexico. Part of the oblique convergence is transferred to this fault system, where the slip rates range from 0.009 to 2.78 mm yr−1. This has caused historic earthquakes in Central Mexico, such as the Acambay quake (Ms=6.9) on 19 November 1912 with surface rupture, and another in Maravatío in 1979 with Ms=5.6. Also, paleoseismic analyses are showing Quaternary movements in some faults, with moderate to large magnitudes. Notably, this zone is seismically active, but lacks a dense local seismic network, and more importantly, its neotectonic movements have received very little attention. The present research encompasses three investigations carried out in the PAFS. First, the estimation of the maximum possible earthquake magnitudes, based on 316 fault lengths mapped on a 15 m digital elevation model, by means of three empirical relationships. In addition, the Hurst exponent Hw and its persistence, estimated for magnitudes Mw (spatial domain) and for 32 slip-rate data (time domain) by the wavelet variance analysis. Finally, the validity of the intrinsic definition of active fault proposed here. The average results for the estimation of the maximum and minimum magnitudes expected for this fault population are 5.5≤Mw≤7. Also, supported by the results of H at the spatial domain, this paper strongly suggests that the PAFS is classified in three different zones (western PAFS, central PAFS, and eastern PAFS) in terms of their roughness (Hw=0.7,Hw=0.5,Hw=0.8 respectively), showing different dynamics in seismotectonic activity and; the time domain, with a strong persistence Hw=0.949, suggests that the periodicities of slip rates are close in time (process with memory). The fractal capacity dimension (Db) is also estimated for the slip-rate series using the box-counting method. Inverse correlation between Db and low slip-rate concentration was observed. The resulting Db=1.86 is related to a lesser concentration of low slip-rates in the PAFS, suggesting that larger faults accommodate the strain more efficiently (length ≥3 km). Thus, in terms of fractal analysis, we can conclude that these 316 faults are seismically active, because they fulfill the intrinsic definition of active faults for the PAFS.

Characteristics and Implications of Nanocoatings on Gouges in a Seismically Active Fault Zone

2021 ◽  
Vol 21 (1) ◽  
pp. 707-714
Author(s):  
Lei Wang ◽  
Zhicai Wang ◽  
Hongtai Chao ◽  
Chuancheng Yang
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Fault Zone ◽  
Active Fault ◽  
Active Faults ◽  
Tectonic Stress ◽  
Tanlu Fault Zone ◽  
Tanlu Fault ◽  
Slip Planes ◽  
Scanning Electron

Using a ZEISS Axio Scope A1 ordinary polarizing microscope, a ZEISS Sigma 300 scanning electron microscope and a HITACHI S4800 scanning electron microscope, we observe micro/nanocharacteristics of slip planes in gouges sampled from the Tanlu fault zone, the Haiyuan fault zone and several other Late Pleistocene active faults, such as the Haiyang fault, the Shuangshan-Lijiazhuang fault and the Xintai-Mengyin fault, in Shandong Province. Based on microscopic observation of gouges, a straight slip zone is a sign of seismic stick slipping. According to scanning electron microscopy results, the surface of gouges is commonly covered by nanocoatings. Such coatings feature nanoparticles, aggregations, scratches, grooves, cracks and “silver lines.” According to the characteristics of nanomaterials, we believe that nanocoatings on gouges could help rapidly unload tectonic stress in the process of energy accumulation and weaken the strength of the active fault, which is beneficial to creep slipping and has a weakening effect on seismogenesis.

scholarly journals CCAF-DB: The Caribbean and Central American Active Fault Database

2019 ◽  
Author(s):  
Richard Styron ◽  
Julio García-Pelaez ◽  
Marco Pagani
Keyword(s):  
Central America ◽  
Fault Zone ◽  
North American ◽  
Active Fault ◽  
North American Plate ◽  
Central American ◽  
Normal Faults ◽  
Caribbean Plate ◽  
Oblique Convergence ◽  
The Caribbean

Abstract. A database of ~250 active fault traces in the Caribbean and Central American regions has been assembled to characterize the seismic hazard and tectonics of the area, as part of the GEM Foundation's Caribbean and Central American Risk Assesment (CCARA) project. The dataset is available in many vector GIS formats, and contains fault trace locations as well as attributes describing fault geometry and kinematics, slip rates, data quality and uncertainty, and other metadata as available. The data is public and open-source (available at https://github.com/GEMScienceTools/central_am_carib_faults), will be updated progressively as new data is available, and is open to community contribution. The active fault data show deformation in the region to be centered around the margins of the Caribbean plate. Northern Central America has sinistral and reverse faults north of the sinistral Motagua-Polochic Fault Zone, which accommodates sinistral Caribbean-North American relative motion. The Central American Highlands extend east-west along a broad array of normal faults, bound by the Motagua-Polochic Fault Zone in the north and dextral faulting in the southwest between the Caribbean plate and the Central American forearc. Faulting in southern Central America is complicated, with trench-parallel reverse and sinistral faults. The northern Caribbean-North American plate boundary is sinistral offshore of Central America, with transpressive stepovers through Jamaica, southern Cuba and Hispaniola. Farther east, deformation becomes more contractional closer to the Lesser Antilles subduction zone, with minor extension and sinistral shear throughout the upper plate, accommodating oblique convergence of the Caribbean and North American plates.

Active displacement on the Calaveras fault zone at Hollister, California

1971 ◽  
Vol 61 (2) ◽  
pp. 399-416
Author(s):  
Thomas H. Rogers ◽  
Robert D. Nason
Keyword(s):  
San Francisco ◽  
Fault Zone ◽  
Active Fault ◽  
San Andreas Fault ◽  
Fault System ◽  
Fault Creep ◽  
San Andreas ◽  
San Andreas Fault System ◽  
Fault Trace ◽  
Fault Displacement

abstract The Calaveras fault zone, which is a major branch of the San Andreas fault system in northern California, passes through the City of Hollister 160 km (100 miles) southeast of San Francisco. Active fault displacement (fault creep slippage) has occurred in and near Hollister along a fault trace within the Calaveras fault zone. Various man-made structures crossing the fault trace have been deformed and gradually offset in a right-lateral sense. The amount of offset varies directly with age of the structure. The maximum offset is 33 cm (13 in) of a sidewalk constructed in the period 1909 to 1914. Offsets on dated structures indicate displacement rates of approximately 2 mm/yr (0.08 in/yr) from 1909 to 1925 and 6 mm/yr (0.24 in/yr) from 1925 to 1967. Data obtained from periodic measurement of specially designed survey lines and instruments have indicated a displacement rate of 9 mm/yr (0.4 in/yr) since May 1967. Displacements of the survey lines are not associated with local earthquake events. Rates of active fault displacement vary with time and position along the Calaveras and San Andreas fault zones in the Hollister area. The pattern of this variation suggests that active displacement on the San Andreas fault zone may be transferring northeastward to the Calaveras fault zone.

scholarly journals CCAF-DB: the Caribbean and Central American active fault database

2020 ◽  
Vol 20 (3) ◽  
pp. 831-857 ◽  
Author(s):  
Richard Styron ◽  
Julio García-Pelaez ◽  
Marco Pagani
Keyword(s):  
Central America ◽  
Fault Zone ◽  
North American ◽  
Active Fault ◽  
North American Plate ◽  
Central American ◽  
Normal Faults ◽  
Caribbean Plate ◽  
Oblique Convergence ◽  
The Caribbean

Abstract. A database of ∼250 active fault traces in the Caribbean and Central American regions has been assembled to characterize the seismic hazard and tectonics of the area, as part of the Global Earthquake Model (GEM) Foundation's Caribbean and Central American Risk Assessment (CCARA) project. The dataset is available in many vector GIS formats and contains fault trace locations as well as attributes describing fault geometry and kinematics, slip rates, data quality and uncertainty, and other metadata as available. The database is public and open source (available at: https://github.com/GEMScienceTools/central_am_carib_faults, last access: 23 March 2020), will be updated progressively as new data become available, and is open to community contribution. The active fault data show deformation in the region to be centered around the margins of the Caribbean plate. Northern Central America has sinistral and reverse faults north of the sinistral Motagua–Polochic fault zone, which accommodates sinistral Caribbean–North American relative motion. The Central Highlands in Central America extend east–west along a broad array of normal faults, bound by the Motagua–Polochic fault zone in the north and trench-parallel dextral faulting in the southwest between the Caribbean plate and the Central American forearc. Faulting in southern Central America is complicated, with trench-parallel reverse and sinistral faults. The northern Caribbean–North American plate boundary is sinistral off the shore of Central America, with transpressive stepovers through Jamaica, southern Cuba and Hispaniola. Farther east, deformation becomes more contractional closer to the Lesser Antilles subduction zone, with minor extension and sinistral shear throughout the upper plate, accommodating oblique convergence of the Caribbean and North American plates.

Evidence of Previous Faulting along the 2019 Ridgecrest, California, Earthquake Ruptures

2020 ◽  
Vol 110 (4) ◽  
pp. 1427-1456 ◽  
Author(s):  
Jessica Ann Thompson Jobe ◽  
Belle Philibosian ◽  
Colin Chupik ◽  
Timothy Dawson ◽  
Scott E. K. Bennett ◽  
...  
Keyword(s):  
Active Fault ◽  
Active Faults ◽  
Ground Surface ◽  
Vertical Motion ◽  
Fault System ◽  
Field Observations ◽  
Surface Rupture ◽  
Earthquake Ruptures ◽  
Slip Displacement ◽  
Surface Ruptures

ABSTRACT The July 2019 Ridgecrest earthquakes in southeastern California were characterized as surprising by some, because only ∼35% of the rupture occurred on previously mapped faults. Employing more detailed inspection of pre-event high-resolution topography and imagery in combination with field observations, we document evidence of active faulting in the landscape along the entire fault system. Scarps, deflected drainages, and lineaments and contrasts in topography, vegetation, and ground color demonstrate previous slip on a dense network of orthogonal faults, consistent with patterns of ground surface rupture observed in 2019. Not all of these newly mapped fault strands ruptured in 2019. Outcrop-scale field observations additionally reveal tufa lineaments and sheared Quaternary deposits. Neotectonic features are commonly short (&lt;2  km), discontinuous, and display en echelon patterns along both the M 6.4 and M 7.1 ruptures. These features are generally more prominent and better preserved outside the late Pleistocene lake basins. Fault expression may also be related to deformation style: scarps and topographic lineaments are more prevalent in areas where substantial vertical motion occurred in 2019. Where strike-slip displacement dominated in 2019, the faults are mainly expressed by less prominent tonal and vegetation features. Both the northeast- and northwest-trending active-fault systems are subparallel to regional bedrock fabrics that were established as early as ∼150  Ma, and may be reactivating these older structures. Overall, we estimate that 50%–70% (i.e., an additional 15%–35%) of the 2019 surface ruptures could have been recognized as active faults with detailed inspection of pre-earthquake data. Similar detailed mapping of potential neotectonic features could help improve seismic hazard analyses in other regions of eastern California and elsewhere that likely have distributed faulting or incompletely mapped faults. In areas where faults cannot be resolved as single throughgoing structures, we recommend a zone of potential faulting should be used as a hazard model input.

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