Paleo-surface ruptures at both sides of a pressure ridge along Alhama de Murcia Fault (SE Spain)

2020 ◽  
Author(s):  
Octavi Gómez-Novell ◽  
María Ortuño ◽  
Julián García-Mayordomo ◽  
Eulàlia Masana ◽  
Thomas Rockwell ◽  
...  
Keyword(s):  
Active Faults ◽  
Great Part ◽  
Slip Rate ◽  
Fault System ◽  
Radiocarbon Dates ◽  
Seismic Parameters ◽  
Central Segment ◽  
Pressure Ridge ◽  
Combining Data ◽  
Surface Ruptures

<p>The Alhama de Murcia Fault (AMF) is one of the most seismically active faults in the Iberian Peninsula, with important associated historical and instrumental seismicity (e.g. the 1674 I<sub>EMS </sub>VIII and 2011 Mw 5.1 Lorca earthquakes), and numerous geomorphic and paleoseismic evidence of paleoearthquakes. It is an oblique left-lateral strike slip fault within the Eastern Betics Shear Zone (EBSZ), a nearly 500 km long fault system that absorbs a great part of convergence between the Nubian and Eurasian plates. Previous paleoseismic studies have mainly focused on the southwestern and especially the central segment of the fault and yielded slip rate values ranging from 1.0 up to 1.7 mm/yr. In the central segment (Lorca-Totana), the fault splays into several branches, the two frontal ones forming a pressure ridge. Paleoseismic trenches have exclusively been dug in the northwestern fault of the pressure ridge, where most of the displacement is along strike, while the expected reverse southeastern branch has never been directly observed.</p><p>We present the first results of paleoseismic trenching across a complete transect of the pressure ridge in the Lorca-Totana segment of AMF. To do so we excavated an exceptionally large trench (7 m deep) in the NW branch and 5 trenches in the SE branch. We have been able to: a) extend the paleoearthquake catalogue in the NW branch by interpreting a total of 13 paleoearthquakes, 6 of which were not identified in previous studies. A restoration analysis has been performed; b) unveil the existence and recent activity (Holocene) of the thrust that bounds the pressure ridge to the SE. We have interpreted at least 5 surface ruptures, with the last one being younger than 8-9 kyr BP, based on new radiocarbon dates.</p><p>The study of these two sites allows for the refinement of the seismic parameters of the fault, formerly inferred from the study of a single branch. In this sense, the more complete paleoearthquake catalogue will allow for reassessment of the recurrence intervals assigned to the fault and new slip rate estimates will be inferred by combining data from the two studied sites. Furthermore, forthcoming OSL dates may allow us to prove or reject the synchronicity of surface ruptures on both sides of the pressure ridge, shedding light on the rupturing style of this fault system during the Late Quaternary. We discuss how these new data on fault-interaction may affect several seismic parameters and their repercussion in source modelling for fault-based probabilistic seismic hazard assessments (PSHA) of the region.</p>

scholarly journals Repeated triggered ruptures on a distributed secondary fault system: an example from the 2016 Kumamoto earthquake, southwest Japan

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Daisuke Ishimura ◽  
Hiroyuki Tsutsumi ◽  
Shinji Toda ◽  
Yo Fukushima ◽  
Yasuhiro Kumahara ◽  
...  
Keyword(s):  
Slip Surface ◽  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Vertical Displacement ◽  
Rupture Zone ◽  
Fault System ◽  
2016 Kumamoto Earthquake ◽  
Kumamoto Earthquake ◽  
Surface Ruptures

AbstractThe Mw7.0 2016 Kumamoto earthquake occurred on the previously mapped Futagawa–Hinagu fault causing significant strong ground motions. A ~ 30-km-long dextral surface rupture appeared on the major fault zone and dextral slip was up to 2–3 m. However, the surface ruptures were also broadly and remotely distributed approximately 10 km away from the primary rupture zone. These numerous distributed secondary surface slips with vertical displacement of less than a few tens of centimeters were detected by the interferometric synthetic aperture radar (InSAR) technology in previous studies. Such displacements occurred not only on previously mapped faults but also on unknown traces. Here, we addressed the following fundamental issues: whether the broadly distributed faults were involved in the past major earthquakes in the neighborhood, and how the fault topography of such secondary faults develops, seismically or aseismically. To find clues for understanding these issues, we show the results of field measurements of surface slips and paleoseismic trenching on distributed secondary faults called the Miyaji faults inside the Aso caldera, 10 km away from the eastern end of the primary rupture zone. Field observations revealed small but well-defined dextral slip surface ruptures that were consistent with vertical and dextral offsets derived from InSAR. On the trench walls, the penultimate event with vertical displacements almost similar to the 2016 event was identified. The timing of the penultimate event was around 2 ka, which was consistent with that of the primary fault and archeological information of the caldera. Considering the paleo-slip event and fault models of the Miyaji faults, they were presumed not to be source faults, and slip on these faults have been triggered by large earthquakes along major adjacent active faults. The results provide important insights into the seismic hazard assessment of low-slip-rate active faults and fault topography development due to triggered displacement along secondary faults.

scholarly journals Methodology for Earthquake Rupture Rate estimates of fault networks: example for the Western Corinth Rift, Greece

2017 ◽  
Author(s):  
Thomas Chartier ◽  
Oona Scotti ◽  
Hélène Lyon-Caen ◽  
Aurélien Boiselet
Keyword(s):  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
System Level ◽  
Fault System ◽  
Normal Faults ◽  
Accurate Estimation ◽  
Probabilistic Seismic Hazard Assessment ◽  
Earthquake Rupture ◽  
Multiple Faults

Abstract. Modelling the seismic potential of active faults is a fundamental step of probabilistic seismic hazard assessment (PSHA). An accurate estimation of the rate of earthquakes on the faults is necessary in order to obtain the probability of exceedance of a given ground motion. Most PSHA studies consider faults as independent structures and neglect the possibility of multiple faults or fault segments rupturing simultaneously (Fault to Fault -FtF- ruptures). The latest Californian model (UCERF-3) takes into account this possibility by considering a system level approach rather than an individual fault level approach using the geological , seismological and geodetical information to invert the earthquake rates. In many places of the world seismological and geodetical information long fault networks are often not well constrained. There is therefore a need to propose a methodology relying only on geological information to compute earthquake rate of the faults in the network. In this methodology, similarly to UCERF-3, a simple distance criteria is used to define FtF ruptures and consider single faults or FtF ruptures as an aleatory uncertainty. Rates of earthquakes on faults are then computed following two constraints: the magnitude frequency distribution (MFD) of earthquakes in the fault system as a whole must follow an imposed shape and the rate of earthquakes on each fault is determined by the specific slip-rate of each segment depending on the possible FtF ruptures. The modelled earthquake rates are then confronted to the available independent data (geodetical, seismological and paleoseismological data) in order to weigh different hypothesis explored in a logic tree. The methodology is tested on the Western Corinth Rift, Greece (WCR) where recent advancements have been made in the understanding of the geological slip rates of the complex network of normal faults which are accommodating the ~15 mm/yr North-South extension. Modelling results show that geological, seismological extension rates and paleoseismological rates of earthquakes cannot be reconciled with only single fault rupture scenarios and require hypothesising a large spectrum of possible FtF rupture sets. Furthermore, in order to fit the imposed regional Gutenberg-Richter MFD target, some of the slip along certain faults needs to be accommodated either with interseismic creep or as post-seismic processes. Furthermore, individual fault’s MFDs differ depending on the position of each fault in the system and the possible FtF ruptures associated with the fault. Finally, a comparison of modelled earthquake rupture rates with those deduced from the regional and local earthquake catalogue statistics and local paleosismological data indicates a better fit with the FtF rupture set constructed with a distance criteria based on a 5 km rather than 3 km, suggesting, a high connectivity of faults in the WCR fault system.

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.

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.

scholarly journals A 2000 Yr Paleoearthquake Record along the Conway Segment of the Hope Fault: Implications for Patterns of Earthquake Occurrence in Northern South Island and Southern North Island, New Zealand

2019 ◽  
Vol 109 (6) ◽  
pp. 2216-2239 ◽  
Author(s):  
Alexandra E. Hatem ◽  
James F. Dolan ◽  
Robert W. Zinke ◽  
Russell J. Van Dissen ◽  
Christopher M. McGuire ◽  
...  
Keyword(s):  
New Zealand ◽  
Late Holocene ◽  
Plate Boundary ◽  
Slip Rate ◽  
Fault System ◽  
Recent Event ◽  
Radiocarbon Age ◽  
Earthquake Record ◽  
Surface Ruptures ◽  
Age Constraints

Abstract Paleoseismic trenches excavated at two sites reveal ages of late Holocene earthquakes along the Conway segment of the Hope fault, the fastest-slipping fault within the Marlborough fault system in northern South Island, New Zealand. At the Green Burn East (GBE) site, a fault-perpendicular trench exposed gravel colluvial wedges, fissure fills, and upward fault terminations associated with five paleo-surface ruptures. Radiocarbon age constraints indicate that these five earthquakes occurred after 36 B.C.E., with the four most recent surface ruptures occurring during a relatively brief period (550 yr) between about 1290 C.E. and the beginning of the historical earthquake record about 1840 C.E. Additional trenches at the Green Burn West (GBW) site 1.4 km west of GBE reveal four likely coseismically generated landslides that occurred at approximately the same times as the four most recent GBE paleoearthquakes, independently overlapping with age ranges of events GB1, GB2, and GB3 from GBE. Combining age constraints from both trench sites indicates that the most recent event (GB1) occurred between 1731 and 1840 C.E., the penultimate event GB2 occurred between 1657 and 1797 C.E., GB3 occurred between 1495 and 1611 C.E., GB4 occurred between 1290 and 1420 C.E., and GB5 occurred between 36 B.C.E. and 1275 C.E. These new data facilitate comparisons with similar paleoearthquake records from other faults within the Alpine–Hope–Jordan–Kekerengu–Needles–Wairarapa (Al-Hp-JKN-Wr) fault system of throughgoing, fast-slip-rate (≥10  mm/yr) reverse-dextral faults that accommodate a majority of Pacific–Australia relative plate boundary motion. These comparisons indicate that combinations of the faults of the Al-Hp-JKN-Wr system may commonly rupture within relatively brief, ≤100-year-long sequences, but that full “wall-to-wall” rupture sequences involving all faults in the system are rare over the span of our paleoearthquake data. Rather, the data suggest that the Al-Hp-JKN-Wr system may commonly rupture in subsequences that do not involve the entire system, and potentially, at least sometimes, in isolated events.

scholarly journals Holocene surface-rupturing earthquakes on the Dinaric Fault System, western Slovenia

Solid Earth ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 2211-2234
Author(s):  
Christoph Grützner ◽  
Simone Aschenbrenner ◽  
Petra Jamšek Rupnik ◽  
Klaus Reicherter ◽  
Nour Saifelislam ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Active Faults ◽  
Historical Seismicity ◽  
Fault System ◽  
Historical Event ◽  
Near Surface ◽  
Geological Evidence ◽  
Geophysical Surveys ◽  
Deformation Features ◽  
Surface Ruptures

Abstract. The Dinaric Fault System in western Slovenia, consisting of NW–SE-trending, right-lateral strike-slip faults, accommodates the northward motion of Adria with respect to Eurasia. These active faults show a clear imprint in the morphology, and some of them hosted moderate instrumental earthquakes. However, it is largely unknown if the faults also had strong earthquakes in the late Quaternary. This hampers our understanding of the regional tectonics and the seismic hazard. Geological evidence of co-seismic surface ruptures only exists for one historical event, the 1511 Idrija earthquake with a magnitude of ∼ M 6.8, but the causative fault is still disputed. Here we use geomorphological data, near-surface geophysical surveys, and paleoseismological trenching to study two of these faults: the Predjama Fault and the Idrija Fault. In a paleoseismological trench across the Predjama Fault we found deformation features that may have been caused by an earthquake between 13–0.7 ka, very likely not earlier than 8.4 ka. At the Idrija Fault, a surface-rupturing earthquake happened around 2.5 ka. We show that instrumental and historical seismicity data do not capture the strongest events in this area.

scholarly journals The Database of the Active Faults of Eurasia (AFEAD): Ontology and Design behind the Continental-Scale Dataset

2021 ◽  
Author(s):  
Egor Zelenin ◽  
Dmitry Bachmanov ◽  
Sofya Garipova ◽  
Vladimir Trifonov ◽  
Andrey Kozhurin
Keyword(s):  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Fault System ◽  
Continental Scale ◽  
Web Map ◽  
Sufficient Detail ◽  
Fault Parameters ◽  
North Asia ◽  
Text Information

Abstract. Active faults are those faults on which movement is possible in the future. It draws particular attention to active faults in geodynamic studies and seismic hazard assessment. Here we present a high-detail continental-scale geodatabase: The Active Faults of Eurasia Database (AFEAD). It comprises 46,775 objects stored in the shapefile format with spatial detail sufficient for a map of scale 1:1M. Fault sense, a rank of confidence in activity, a rank of slip rate, and a reference to source publications are provided for each database entry. Where possible, it is supplemented with a fault name, fault zone name, abbreviated fault parameters (e.g., slip rate, age of the last motion, total offset), and text information from the sources. The database was collected from 612 sources, including regional maps, databases, and research papers. AFEAD facilitates a spatial search for local studies. It provides sufficient detail for planning a study of a particular fault system and guides deeper bibliographical investigations if needed. This scenario is particularly significant for vast Central and North Asia areas, where most studies are available only in Russian and hardcopy. Moreover, the database model provides the basis for GIS-based regional and continental-scale integrative studies. The database is available at https://doi.org/10.13140/RG.2.2.10333.74726 and via web map at http://neotec.ginras.ru/index/mapbox/database_map.html (last access: July 30, 2021). Some database representations with supplementary data are hosted at http://neotec.ginras.ru/index/english/database_eng.html.

A retrospective of the work of Patience Cowie: the interaction of faults in space and time and their influences on subsurface fluid flow, surface processes and earthquakes

2021 ◽  
Author(s):  
Zoe Shipton
Keyword(s):  
Hazard Assessment ◽  
Active Faults ◽  
Slip Rate ◽  
Earthquake Hazard ◽  
Fault System ◽  
Fault Mechanics ◽  
Flow Surface ◽  
Earthquake Hazard Assessment ◽  
Recurrence Intervals ◽  
3D Seismic Data

&lt;p&gt;Patience Cowie was a truly outstanding scientist whose research spanned several disciplines of structural geology and tectonics. She made a lasting contribution to every discipline she published in and as well as academic advances, produced significant impacts in the hydrocarbon industry and earthquake hazard assessment. Her research in fault mechanics and fault population was a genuine game-changer. The implications of her work for predicting fault patterns and linkage have been crucial for the interpretation of 3D seismic data, and for examining the interplay between faults and the basins they bound and sediments they host. More recently she explored relationships between fault geometry, slip rate and recurrence intervals along seismically active faults, with important implications for earthquake hazard assessment.&lt;/p&gt;&lt;p&gt;Patience&amp;#8217;s drive to constrain physical explanations of the underlying dynamics of Earth processes meant her numerical modelling was always firmly grounded in field observations. Her models incorporated the effects of stress in time and space as fault system evolved, but always underpinned by geometric and kinematic observations in the field. She loved fieldwork and her joy at the beauty of geological structures was infectious and inspiring. &amp;#160;&lt;/p&gt;

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.

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