Active Fault Map Research Articles

A comment on “Orogen-parallel, active left-slip faults in the eastern Himalaya: Implications for the growth mechanism of the Himalayan arc” by Li and Yin (Earth Planet Sci. Lett. 274 (2008) 258–267)

Understanding how convergence is partitioned in the Himalayan arc and across the entire Tibetan plateau provides critical kinematic constraints on mechanical models of continental lithospheric deformation. Based on geomorphic evidence, Li and Yin (2008) recently claimed to have discovered several active E–W trending left-lateral faults in south Tibet. These faults, interpreted to be part of a ~100 km-wide and N500 km-long Dinggye–Chigu fault zone (DCFZ), would follow the Himalayan arc from ~88°E to the eastern syntaxis (95°E). The total slip-rate across this zone would be at least 4 to 8 mm/yr, and possibly up to 25 to 70 mm/yr (when summing given slip-rate on each fault). The rates are then compared with the right-lateral slip-rate along the Karakorum fault in western Tibet, inferred to be between 1 and 10 mm/yr from the literature. It is concluded that, since 4 Ma, oroclinal bending is the dominant process in Himalayan tectonics (Klootwijk et al., 1985). This article has major implications on the mechanics of the Himalayas and of the collision belts in general. Our fieldwork, geomorphic and geodetic analysis of the region studied by Li and Yin (2008) suggest that: 1) the geomorphic offsets interpreted by these authors are better explained by landform alignments with no Fig. 1. Simplified geological and active fault map of the Dinggye region (see inset for location within Indo-Asia collision framework). The Gongzuo and Comuzhelin basins are characterized by folds, trending on average EW, of the Tethysian sediments in the hanging wall of thenorthdipping southTibetandetachment system(e.g., Burgetal.,1984). Presentday active faults are NS trending normal faults (e.g. Armijo et al.,1986). Note the extension of high lake stands (at 4400 and 4460m asl) marked by clear shorelines (sand bars, steep cliffs, etc...). Arrow is location of Fig. 3. Rectangles are Figs 2, 4 and 5. r Woerd).

活断層からの地震発生予測

In order to assess the probability of the occurrence of future large earthquakes based upon the past activities of active faults, we divided active faults into behavioral segments, and adopted the cascade earthquake model, that is, a model that considers that an earthquake is sometimes caused by a single segment and sometimes caused by multiple segments. Using this model, we can evaluate the rupture probability of active faults by a uniform standard without any inconsistencies with field data. The result was published as the Rupture Probability Map of Major Active Faults in Japan.

Variations and Origin of Fault Activity of Baikal Rift System and Adjacent Territories in Real Time

The available geological and geophysical methods fail to estimate variations of fault activity in real time intervals, such as, months, years or decades. Using geo-informational technologies, this challenge can be resolved with an algorithm and software based on a quantitative index of seismic activity. Such an approach has been applied to studies on the Baikal rift system (BRS) and its adjacent territories. It is discovered that fault activity is variable in intervals of several years, which cannot be attributed to changes in regional stress fields. An active fault map of BRS and curves of the quantitative index of seismic activity of faults are constructed for the BRS cross-section. The proposed method ensures a detailed classification of active faults by the quantitative index of seismic activity, and thus significantly extends options for finding solutions of problems related to the middle-term forecast of earthquakes. This method has been applied to study spatial and temporal variations, sources, and mechanisms of the recent fault activation. It is shown that fault activation has a relatively high frequency on the real time scale because of the slow deformation waves of disturbance that are generated by inter-plate and intra-block movements of the brittle lithosphere. Throughput velocity of deformation waves allow classification of active faults into groups that differ in geological and geophysical parameters. They also allow an estimation of the direction of the deformation wave's front and identification of an area of dominating fault activation in real time (geologically instant) intervals.

A fault scarp in an urban area identified by LiDAR survey: A Case study on the Itoigawa–Shizuoka Tectonic Line, central Japan

A light detection and ranging (LiDAR) survey was conducted in a densely built-up area to generate a high-resolution digital elevation model (DEM) to look for active faults. The urban district of Matsumoto City in central Japan is located in a 3-km 2 basin along the Itoigawa–Shizuoka Tectonic Line active fault system, one of Japanese onshore fault systems with the highest earthquake probability. A high-resolution DEM at a 0.5-m-grid interval was obtained after removing the effects of laser returns from buildings, clouds and vegetation. It revealed a continuous scarp, up to ~ 2 m in height. Borehole data and archaeological studies indicate the scarp was formed during the most recent faulting event associated with historical earthquakes. In addition, the fault scarp strongly supports that the urban district is in a pull-apart basin related to a fault step-over between two left-lateral strike-slip faults. Consequently, accurate interpretation of fault geometry is crucial to provide estimates of future surface deformation and to allow modeling of basin structure and strong ground motion. Thus, the LiDAR mapping survey in urban districts is effective for detailed active fault mapping in order to constrain basin structure and to forecast the exact location of surface rupturing associated with large earthquakes.

Contribution of the SISCam Web-based GIS to the seismotectonic study of Campania (Southern Apennines): an example of application to the Sannio-area

In this article the implementation and potential of the Seismotectonic Information System of the Campania Region (SISCam) are described, in particular an application of this Web-based GIS system to the seismotectonic analysis of the Sannio area (Southern Apennines) is performed. WEB-GIS technologies greatly contribute to both the environmental monitoring and the disaster management of areas affected by high natural risks. Specifically the SISCam system has been developed with the aim of providing easy access and fast diffusion, through Internet technology, of the most significant geological, geophysical, and territorial data relative to the Campania Region. The Sannio area has been selected as our application example because it is among the most active seismic regions in Italy. This portion of the Southern Apennines which was hit by the June 5, 1688 strong earthquake (M W = 6.7, CPTI 1999) and by some low- and moderate-energy seismic sequences (1990–1992, 1997), is characterized by a complex inherited tectonic setting and low-tectonic deformation rates that hide the seismogenic sources position. Since this case study turned out to be complicated, the use of the SIScam WEB-GIS has become indispensable because it allowed us to visualize, integrate and analyze all the data available, in order to obtain an accurate and direct picture of the seismotectonic setting of the area. Moreover, a different approach of data analysis was necessary, due to the lack of up-to-date neotectonic and structural data; therefore, the operation of this GIS system enabled us to process and generate some original informative layers, through image analysis, such as new structural lineaments represented on a map of the potential active faults of the area, which has been the final result of our application, as a contribution to new knowledge about the local seismic risk parameters.

Investigation of earthquakes' geo-surroundings in the Pannonian Basin by using GIS tools

The mechanism of earthquake occurrence in the Pannonian Basin is not clear in most cases (in other words, it is often not possible to find a relationship between the location of epicenters and the elements of the maps of recent tectonic movements), hence a GIS has been created in order to clarify the origin of these events. The special seismological GIS includes all relevant information (maps and joint database) concerned with earthquakes covering the whole territory of Hungary. GIS contains the following maps: special macro- and microseismic epicenters and their parameters; different active tectonic fault maps; digital terrain model of the recent relief; digital terrain models of different geological basements; appropriate geophysical anomaly maps; Quaternary sediment thickness; recent rivers, water streams and settlements. GIS enables us to carry out special operations between different layers by applying its tools in order to reveal the recent tectonic movements and to throw light upon the generation of possible earthquake occurrences. Results of the present investigation in GIS revealed that significant relation exists between the earthquake foci and recent tectonic lines. Some foci, however, can not be related to fracture lines. One part of earthquakes showed agreement with Pre-Tertiary basement areas of considerable slope, with the recent tectonic elements of Geomorphological maps and with the piedmonts of the North Hungarian Range. Some traces of recent movements have been found with the help of the multiplication map of Quaternary sediment thickness map and Recent relief (Digital Elevation Model).

Early detection of eruptive dykes revealed by normalized difference vegetation index (NDVI) on Mt. Etna and Mt. Nyiragongo

Flank-fissure eruptions involve lateral injection and propagation of magma in a volcanic edifice along pre-existing fractures in the direction of the rift zones where magma intrusion and lava flow production are concentrated over time. Thus, the identification and mapping of active fractures and faults is a fundamental aspect of studies of active volcanic systems. However, gradual dyke wedge emplacement at depth in well-fractured zones on volcano flanks and in volcanic rift zones does not necessarily trigger large amplitude deformation signals susceptible to be recorded months or even years before the actual eruption. Here we show that active and potentially eruptive areas can be detected up to 2 yrs before the arrival to the surface of the final eruptive dyke and venting of lava flows by processing satellite images applying a normalized difference vegetation index (NDVI) algorithm. A posteriori analysis of satellite images indeed reveals that the surficial effects of dyke wedge injection and ascent on plant growth were apparent for Mt. Etna from 2000 to 2002 and for Mt. Nyiragongo in 2001, thus months to years before they erupted.

Late Quaternary geometry and kinematics of faults at the southern termination of the Taupo Volcanic Zone, New Zealand

Late Quaternary structure and kinematics at the southern termination of the Taupo Rift are investigated by means of active fault mapping and estimates of fault displacement and extension rates. Active faults in the southern Taupo Rift are normal in sense and include three major structures: the NNE‐trending Mt Ruapehu Graben; the E‐W to ESE‐WNW‐trending Ohakune‐Raetihi fault set; and the NE‐trending Karioi fault set. Displacements of young geomorphic features, fault plane exposures in roadcuts, and trenches across faults show that all faults are active contemporaneously. The Mt Ruapehu Graben is the southern extension of the modern (i.e., <26 ka) Taupo Rift (or Taupo Fault Belt, TFB), and has developed as a result of backarc extension related to the Hikurangi subduction margin. Geologic extension rate for the Mt Ruapehu Graben is estimated here at 2.3 ± 1.2 mm/yr. The other two structures strike almost perpendicular to the Taupo Rift terminating the Mt Ruapehu Graben to the south. The co‐existence of three normal fault sets in mutual cross‐cutting relations and with no significant strike‐slip on any of them may be related to local reorientation of the minimum principal stress axis (σ3) or to a stress tensor where |σ3| ≈ |σ2|. Complicated strains at the southern termination of the Taupo Rift are related to block rotations in the Hikurangi subduction margin.

Recent fold growth and drainage development: The Janauri and Chandigarh anticlines in the Siwalik foothills, northwest India

The active growth of a fault-and-thrust belt in frontal zones of Himalaya is a prominent topographical feature, extending 2500 km from Assam to Pakistan. In this paper, kinematical analysis of frontal anticlines and spatial mapping of active faults based on geomorphological features such as drainage pattern development, fault scarps and uplifted Quaternary alluvial fans are presented. We analyse the geomorphic and hydrographic expressions of the Chandigarh and the Janauri active anticlines in the NW India Siwaliks. To investigate the morphological scenario during the folding process, we used spatial imagery, geomorphometric parameters extracted from digital elevation models and fieldwork. Folding between the Beas and Sutlej Rivers gives clear geomorphological evidence of recent fold growth, presumably driven by movements of blind thrust faults. Structural style within the Janauri and Chandigarh anticlines is highly variable (fault-propagation folds, pop-up structures and transfer faults). The approach presented here involves analysis of topography and drainage incision of selected landforms to detect growth of active anticlines and transfer faults. Landforms that indicate active folding above a southwest-dipping frontal thrust and a northeast-dipping back-thrust are described. Along-strike differences in ridge morphology are measured to describe the interaction of river channel patterns with folds and thrust faults and to define history of anticline growth. The evolution of the apparently continuous Janauri ridge has occurred by the coalescence of independent segments growing towards each other. By contrast, systematic drainage basin asymmetry shows that the Chandigarh anticline ridge has propagated laterally from NW to SE.

Analysis of landslide susceptibility in the Suusamyr region, Tien Shan: statistical and geotechnical approach

The Suusamyr region is located in the northern part of the Tien Shan Range in Central Asia. In 1992, this region was hit by the Ms = 7.3 Suusamyr earthquake triggering several large landslides along the Suusamyr Valley and on the southern slopes of the adjacent Suusamyr Range. One of these landslides had been investigated by geophysical and geotechnical methods in order to determine local trigger factors. The present paper focuses on the influence of geological and morphological factors upon landslide occurrence on a regional scale. The analysis is based on a digital data set including landslides triggered in 1992 and several older landslides as well as various types of digital elevation models (DEMs), ASTER image data, and geological and active fault maps. These data were combined to compute landslide susceptibility (LS) maps using statistical methods, Landslide Factor and Conditional Analyses (LFA, CA), as well as a geotechnical one, the Newmark's Method (NM). The landslide data set was also analyzed with respect to the size–frequency relationship.

The sense in surveying surface ruptures and establishing active fault map associated with the Mid Niigata Earthquake in 2004

The sense in surveying surface ruptures and establishing active fault map associated with the Mid Niigata Earthquake in 2004

Active faulting in the Walker Lane

Deformation across the San Andreas and Walker Lane fault systems accounts for most relative Pacific–North American transform plate motion. The Walker Lane is composed of discontinuous sets of right‐slip faults that are located to the east and strike approximately parallel to the San Andreas fault system. Mapping of active faults in the central Walker Lane shows that right‐lateral shear is locally accommodated by rotation of crustal blocks bounded by steep‐dipping east striking left‐slip faults. The left slip and clockwise rotation of crustal blocks bounded by the east striking faults has produced major basins in the area, including Rattlesnake and Garfield flats; Teels, Columbus and Rhodes salt marshes; and Queen Valley. The Benton Springs and Petrified Springs faults are the major northwest striking structures currently accommodating transform motion in the central Walker Lane. Right‐lateral offsets of late Pleistocene surfaces along the two faults point to slip rates of at least 1 mm/yr. The northern limit of northwest trending strike‐slip faults in the central Walker Lane is abrupt and reflects transfer of strike‐slip to dip‐slip deformation in the western Basin and Range and transformation of right slip into rotation of crustal blocks to the north. The transfer of strike slip in the central Walker Lane to dip slip in the western Basin and Range correlates to a northward broadening of the modern strain field suggested by geodesy and appears to be a long‐lived feature of the deformation field. The complexity of faulting and apparent rotation of crustal blocks within the Walker Lane is consistent with the concept of a partially detached and elastic‐brittle crust that is being transported on a continuously deforming layer below. The regional pattern of faulting within the Walker Lane is more complex than observed along the San Andreas fault system to the west. The difference is attributed to the relatively less cumulative slip that has occurred across the Walker Lane and that oblique components of displacement are of opposite sense along the Walker Lane (extension) and San Andreas (contraction), respectively. Despite the gross differences in fault pattern, the Walker Lane and San Andreas also share similarities in deformation style, including clockwise rotations of crustal blocks leading to development of structural basins and the partitioning of oblique components of slip onto subparallel strike‐slip and dip‐slip faults.

Western Mediterranean Ridge mud belt correlates with active shear strain at the prism-backstop geological contact

A high-resolution swath-mapping survey conducted in the deep waters of the eastern Mediterranean Sea allowed mapping of active faults and mud volcanism along a sizable portion of the Mediterranean Ridge. Active shear is localized at the prism-backstop con- tact, a major dextral flower structure and a site of massive mud expulsion. We investigate the relationship between the mud output rate and horizontal strain rate by combining the mud volume estimate from sea-bottom reflectivity with kinematic modeling based on far- field global positioning system data and local fault and strain patterns. We find a direct correlation between maxima of mud output and maxima of the shear component of strain at the backstop contact. Mud volcanism may reflect the abundance of solid (mud) and fluid (methane) sources combined with a favorable tectonic regime established at the prism-backstop contact in post-Pliocene time, in relation to plate tectonic changes.

3-D mapping of segmented active faults in the southern Vienna Basin

In this paper we present novel data on the location and kinematics of seismically active fault segments of the Vienna Basin Transfer Fault System in the southern Vienna Basin. Spatial mapping of active faults and kinematical analyses are based on commercial 3-D reflection seismic data, geomorphological features such as tilted Quaternary river terraces and fault scarps, the geometry of subsided Quaternary basins, and published geodetic data. Accordingly, active faulting in the southern Vienna Basin occurs partly by reactivation of the Miocene fault system related to the formation of the Vienna pull-apart basin between c. 17 and 8 Ma. Two domains of Quaternary and active faults can be distinguished with, (1) predominantly strike-slip and (2) mainly normal faulting. (1) A seismically active NE-striking sinistral strike-slip fault zone with large negative flower structures is mapped at the south-eastern margin of the basin. Subsidence within the reflection seismically imaged flower structure is documented by up to 1000 m of throw since Pannonian times and the accumulation of up to 150 m thick Quaternary gravels. At the surface the fault zone is characterized by en-echelon faults with some prominent scarps. (2) Major E-dipping normal faults branch off from the transfer strike-slip fault system. The normal faults extend into the central and western part of the basin as well as into the urban area of Vienna. Close to Vienna, the normal offset along such a normal fault is at minimum 300 m since Pannonian times. Surface expressions of active normal faulting are tilted Quaternary terraces of the Danube river and tilted ancient land surfaces in the hanging wall of the normal faults. The mapped active normal faults are kinematically linked by a common detachment horizon, which is in contact with the seismically active strike-slip zone along the south-eastern border of the basin. Northeast of the Vienna Basin the seismically active zone continues as a straight line indicating a rather linear transfer fault zone than a pull-apart step over geometry.

Magnetic Surveying of the Chaochou Fault of Southern Taiwan: Culmination of Basement-Involved Surface Thrusting in Arc-Continent Collision

Taiwan's southernmost, best-defined onshore surface geologic contact, resulting from the collision of the Philippine plate against the Eurasia plate, is the NNE-trending, 80 km long, oblique-slip Chaochou fault. This major crustal break in the Eurasian plate has an extremely conspicuous surface expression noted from satellite imagery and topographic maps as well as distinct subsurface magnetic and gravity signatures, up to 40 nT and 50 mgal, respectively. From a regional total magnetic intensity survey that included seven east-west profiles, integrated with Bouguer gravity and seismic reflection data, we suggest that the nearly vertical dip of the Chaochou fault in the shallow subsurface results from basement-involved thrusting that changes to high-angle reverse faulting near the surface. The horizontal offset on this basement thrust probably involves shallow left-lateral strike slip motion, whereas the major thrust geometry is controlled by deeper seated normal faults in the pre-Miocene basement rocks. The net effect of all this motion produces the present-day surface escarpment over a distance of 80 km between the villages of Liouguei and Fangliao in southern Taiwan. The overriding east-dipping Chaochou fault and associated Wanlong splay are upthrusts that bifurcate from a basement-involved decollement at approximately 6 km depth. As such, these two faults represent the westernmost advance of basement-involved thrusting exposed at the surface in southern Taiwan. Linear regression analysis applied to results from detailed field surveying of the total intensity of the magnetic field is useful in locating both extensional and compressional fault regimes in basement rocks. This technique should be considered not only by plate tectonophysicists, but by those researchers involved in the mapping of active faults where seismic risk is high.

Active faults and paleoseismicity in Fennoscandia, especially Sweden. Primary structures and secondary effects

Fennoscandia, today a region of low to moderately low seismicity, was, at the time of deglaciation, with rates of uplift on the order of tens of centimetres per year, a region of very high seismicity and active tectonics. This is evident both from primary fault structures and from secondary sedimentary and hard rock effects in the region around the epicentral areas. The map of active faults in Fennoscandia includes numerous structures previously not recognised. Despite this, the recording of active faults and paleoseismic events is still in its initial phase. Much more data will surely accumulate in the near future.

Active faults in Africa: a review

The active fault database and Map of active faults in Africa, in scale of 1:5,000,000, were compiled according to the ILP Project II-2 “World Map of Major Active Faults”. The data were collected in the Royal Museum of Central Africa, Tervuren, Belgium, and in the Geological Institute, Moscow, where the final edition was carried out. Active faults of Africa form three groups. The first group is represented by thrusts and reverse faults associated with compressed folds in the northwest Africa. They belong to the western part of the Alpine–Central Asian collision belt. The faults disturb only the Earth's crust and some of them do not penetrate deeper than the sedimentary cover. The second group comprises the faults of the Great African rift system. The faults form the known Western and Eastern branches, which are rifts with abnormal mantle below. The deep-seated mantle “hot” anomaly probably relates to the eastern volcanic branch. In the north, it joins with the Aden–Red Sea rift zone. Active faults in Egypt, Libya and Tunis may represent a link between the East African rift system and Pantellerian rift zone in the Mediterranean. The third group included rare faults in the west of Equatorial Africa. The data were scarce, so that most of the faults of this group were identified solely by interpretation of space imageries and seismicity. Some longer faults of the group may continue the transverse faults of the Atlantic and thus can penetrate into the mantle. This seems evident for the Cameron fault line.

Active faults in Eurasia: general remarks

The database and map of active faults of Eurasia, 1:5,000,000, have been compiled according to the ILP Project II-2 “World Map of Major Active Faults.” The map shows the complicated distribution of active faulting. The major faults group in broad mobile belts between relatively weakly faulted parts of the main plates. The faults form the plates, microplates and crustal blocks boundaries there and are accompanied by deformation of the boundary areas. Using active fault data for the seismic hazard assessment (estimation of maximum possible magnitudes of earthquakes in fault zones), it is necessary to take into account the total neotectonic activity of the territory and average rate and sense of motion on the fault. Because trenching gives a possibility to determine only vertical earthquake offset on a fault, it is necessary to make corrections for strike–slip faults to estimate the earthquake magnitude by using this parameter.

Active faults, seismicity and recent fracturing in the lithosphere of the Baikal rift system

A map of major active faults has been constructed for the Baikal rift system (BRS). Recent active faults are identified using seismological data. The BRS seismicity of the past 40 years is statistically analyzed. Areas of a “stable” concentration of epicenters are revealed. On this basis, a zone of recent fracturing of the lithosphere is identified and its relation to active and developing faults of the BRS is analyzed. The zone of the lithosphere fracturing is a major tectonic structure, which controls both the recent seismic process and the reactivation of ancient faults. It is demonstrated that the available seismological data can provide a basis for a detailed classification of faults by degree of their tectonic activity. Regularities in the distribution of strong earthquakes along the zone of the recent fracturing of the lithosphere are established, as well as regularities in the distribution of strong and weak seismic events relative to transform and other faults. The degree of the fault reactivation is determined by their spatial closeness to the axial zone of the recent rupturing of the lithosphere.

Geomorphological identification of pre-existing active Chelungpu Fault in central Taiwan, especially its relation to the location of the surface rupture by the 1999 Chichi earthquake

Pre-existing active faults were identified on the Chelungpu Fault, based on airphoto interpretation and field survey, and their precise position was mapped. Active faults are divided into four types from I to IV, depending on certainty of the presence of active faults and accuracy of their location. Most of the Chelungpu Fault shows evidence of Late Quaternary repeated activities. The location of the 1999 Chichi earthquake surface ruptures were plotted from the sites where they were accurately mapped by GPS measurements by the Central Geological Survey, supplemented by our own observations, on the active fault map. There is a very close coincidence between the active fault trace and the 1999 surface rupture, indicating that the mapping of active faults is fundamental for the estimation of location of rupture by future earthquakes.