scholarly journals Discrete changes in fault free-face roughness: constraining past earthquakes characteristics

2020 ◽  
Author(s):  
Olaf Zielke ◽  
Lucilla Benedetti ◽  
P. Martin Mai ◽  
Magali Rizza ◽  
Jules Fleury ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Active Tectonics ◽  
Slip Rate ◽  
Fault Scarp ◽  
Rock Properties ◽  
Normal Faults ◽  
Earthquake Recurrence ◽  
Face Surface ◽  
Free Face ◽  
Face Morphology

<p>A driving motivator in many active tectonics studies is to learn more about the recurrence large and potentially destructive earthquakes, providing the means to assess the respective fault’s future seismic behavior. Doing so requires long records of earthquake recurrence. The lack of sufficiently long instrumental seismic records (that would be best suited for this task) has led to the development of other approaches that may constrain the recurrence of surface rupturing earthquakes along individual faults. These approaches take different forms, depending on the specific tectonic and geographic conditions of an investigated region.</p><p>For example, around the Mediterranean Sea, we frequently find bedrock scarps along normal faults. Assuming that bedrock (i.e., fault free-face) exposure is caused by the occurrence of sub-sequent large earthquakes, we may measure certain rock properties to constrain the time and size of past earthquakes as well as the fault’s geologic slip-rate. A now-classic example in this regard is the measurement of <sup>36</sup>Cl concentrations along exposed fault scarps in limestones.</p><p>For the presented study, we looked at another property of the exposed fault free-face, namely its morphologic roughness. We aim to identify whether fault free-face roughness contains information to constrain earthquake occurrence and fault slip-rates following the assumption that  sub-sequent exposure to the elements and sub-areal erosional conditions may leave a signal in how rough (or smooth) the fault free-face is (assuming a somewhat uniform pre-exposure roughness). Here, we present observations of fault free-face surface roughness for the Mt. Vettore fault (last ruptured in 2016) and the Rocca Preturo fault (The underlying models of fault free-face morphology were generated using the Structure-from-Motion approach and a large suite of unregistered optical images.). Employing different metrics to quantify morphologic roughness, we were indeed able to observe a) an increase in surface roughness with fault scarp height (i.e., longer exposure to sub-areal erosion causes higher roughness), and b) distinct (rather than gradual) changes in surface roughness, suggesting a correlation to individual exposure events such as earthquakes. Hence, fault free-face morphology of bedrock faults may serve as an additional metric to reconstruct earthquake recurrence patterns.</p>

scholarly journals Uncertainty in strain-rate from field measurements of the geometry, rates and kinematics of active normal faults: Implications for seismic hazard assessment

2020 ◽  
Author(s):  
Claudia Sgambato ◽  
Joanna P. Faure Walker ◽  
Gerald P. Roberts
Keyword(s):  
Seismic Hazard ◽  
Strain Rate ◽  
Structural Complexity ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
Field Measurements ◽  
Structural Data ◽  
Fault Scarp ◽  
Normal Faults ◽  
Multiple Measurements

<p>Multiple measurements of the geometry, kinematics and rates of slip across the well-exposed Auletta fault scarp (Campania, Italy) are presented, and we use these in order to investigate: (1) the spatial resolution of field measurements needed to accurately calculate a representative strain-rate for seismic hazard calculations; (2) what aspects of the geometry and kinematics would introduce uncertainty in calculated strain-rate, if those are not measured in the field. Our results show that the magnitude of the post-glacial maximum (15±3 ka) throw gradually decreases towards the tip of the fault, but variations are observed along strike, across areas of structural complexity such as along-strike bends in the fault plane where the fault dip is greater. We find that if such variations are unnoticed, different values of strain-rate would be produced, and hence different values would result in seismic hazard calculations. To demonstrate this, we calculate the strain-rate across the Auletta fault using all our measurements, and subsequently degrade the dataset removing one measurement at a time and recalculating the implied strain-rate at each step. The results show that excluding measurements can alter strain-rate results beyond 1 σ uncertainty, thus we suggest caution when using only one measurement of slip-rate along a fault for calculating hazard, as a full understanding of the potential implied errors needs consideration. Furthermore, we investigate the effect of approximating the throw profile along the fault using boxcar and triangular slip distributions; we show that this can underestimate or overestimate the strain-rate, with results in the range of 72–237% of our most detailed strain-rate calculation. We suggest that improved understanding of the potential implied errors in strain-rate calculations from field structural data should be implemented in seismic hazard calculations.</p>

Uplift and active tectonics of southern Albania inferred from incision of alluvial terraces

2009 ◽  
Vol 71 (3) ◽  
pp. 465-476 ◽  
Author(s):  
J. Carcaillet ◽  
J.L. Mugnier ◽  
R. Koçi ◽  
F. Jouanne
Keyword(s):  
Active Faults ◽  
Active Tectonics ◽  
Slip Rate ◽  
Age Dating ◽  
Normal Faults ◽  
Published Data ◽  
Fluvial Terraces ◽  
Thrust System ◽  
Alluvial Terraces

AbstractIn Albania, the Osum and Vjoje rivers cross the active graben system and the active frontal thrust system of the Albanides. The effects of climatic and geodynamic forcing on the development of these two rivers were investigated by the means of field mapping, topographic surveying and absolute exposure-age dating. We established the chronology of terraces abandonment from the compilation of new dating (14C and in situ produced 10Be) and previously published data. We identified nine fluvial terraces units developed since Marine Isotope Stage 6 up to historic times. From this reconstituted history, we quantified the vertical uplift on a time scale shorter than the glacial climatic cycle. Regional bulging produces an overall increase of the incision rate from the west to the east that reaches a maximum value of 2.8 m/ka in the hinterland. Local pulses of incision are generated by activation of normal faults. The most active faults have a SW–NE trend and a vertical slip rate ranging from 1.8 to 2.2 m/ka. This study outlines the geodynamic control in the development of rivers flowing through the Albanides on the scale of 103–105ka.

Late Pleistocene extension and strike-slip in the Dead Sea Basin

2004 ◽  
Vol 141 (5) ◽  
pp. 565-572 ◽  
Author(s):  
YUVAL BARTOV ◽  
AMIR SAGY
Keyword(s):  
Internal Structure ◽  
Slip Rate ◽  
Dead Sea ◽  
Strike Slip ◽  
Normal Faults ◽  
Small Scale ◽  
Dead Sea Basin ◽  
Pull Apart Basin ◽  
Western Border ◽  
The Dead

A newly discovered active small-scale pull-apart (Mor structure), located in the western part of the Dead Sea Basin, shows recent basin-parallel extension and strike-slip faulting, and offers a rare view of pull-apart internal structure. The Mor structure is bounded by N–S-trending strike-slip faults, and cross-cut by low-angle, E–W-trending normal faults. The geometry of this pull-apart suggests that displacement between the two stepped N–S strike-slip faults of the Mor structure is transferred by the extension associated with the normal faults. The continuing deformation in this structure is evident by the observation of at least three deformation episodes between 50 ka and present. The calculated sinistral slip-rate is 3.5 mm/yr over the last 30 000 years. This slip rate indicates that the Mor structure overlies the currently most active strike-slip fault within the western border of the Dead Sea pull-apart. The Mor structure is an example of a small pull-apart basin developed within a larger pull-apart. This type of hierarchy in pull-apart structures is an indication for their ongoing evolution.

scholarly journals Paleoearthquake history of the Spili fault

2017 ◽  
Vol 47 (2) ◽  
pp. 595
Author(s):  
V. Mouslopoulou ◽  
D. Moraetis ◽  
L. Benedetti ◽  
V. Guillou ◽  
D. Hristopulos
Keyword(s):  
Rare Earth ◽  
Active Faults ◽  
Fault Scarp ◽  
Large Magnitude ◽  
Earthquake Recurrence ◽  
Earthquake Parameters ◽  
History Of ◽  
Earthquake Recurrence Interval ◽  
Seismic Displacements

The paleoearthquake activity on the Spili Fault is examined using a novel methodology that combines measurements of Rare Earth Elements (REE) and of in situ cosmogenic 36Cl on the exhumed fault scarp. Data show that the Spili Fault is active and has generated a minimum of five large-magnitude earthquakes over the last ~16500 years. The timing and, to a lesser degree, the slip-size of the identified paleoearthquakes was highly variable. Specifically, the two most recent events occurred between 100 and 900 years BP producing a cumulative displacement of 3.5 meters. The timing of the three older paleoearthquakes is constraint at 7300, 16300 and 16500 years BP with slip sizes of 2.5, 1.2 and 1.8 meters, respectively. The magnitude of the earthquakes that produced the measured co-seismic displacements, ranges from M 6.3-7.3 while the average earthquake recurrence interval on the Spili Fault is about 4200 years. The above data suggest that the Spili is among the most active faults on Crete and its earthquake parameters may be incorporated into the National Seismic Hazard Model.

scholarly journals Slip‐rate on the Main Köpetdag (Kopeh Dagh) Strike‐slip fault, Turkmenistan, and the active tectonics of the South Caspian

Tectonics ◽  
2021 ◽  
Author(s):  
Richard Thomas Walker ◽  
Y. Bezmenov ◽  
G. Begenjev ◽  
S. Carolin ◽  
N. Dodds ◽  
...  
Keyword(s):  
Active Tectonics ◽  
Slip Rate ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
The South

Paleoearthquakes on the Húsavík-Flatey Fault in northern Iceland: Where are the large earthquakes?

2021 ◽  
Author(s):  
Remi Matrau ◽  
Yann Klinger ◽  
Jonathan Harrington ◽  
Ulas Avsar ◽  
Esther R. Gudmundsdottir ◽  
...  
Keyword(s):  
Slip Rate ◽  
Late Glacial ◽  
Fault Scarp ◽  
Alluvial Fan ◽  
Tectonic Deformation ◽  
Birch Wood ◽  
Alluvial Deposits ◽  
Slip Rates ◽  
Tephra Layers ◽  
Large Earthquakes

<p>Paleoseismology is key to study earthquake recurrence and fault slip rates during the Late Pleistocene-Holocene. The Húsavík-Flatey Fault (HFF) in northern Iceland is a 100 km-long right-lateral transform fault connecting the onshore Northern Volcanic Zone to the offshore Kolbeinsey Ridge and accommodating, together with the Grímsey Oblique Rift (GOR), ~18 mm/yr of relative motion between the Eurasian and North American plates. Significant earthquakes occurred on the HFF in 1755, 1838 and 1872 with estimated magnitudes of 6.5-7. However, historical information on past earthquakes prior to 1755 is very limited in both timing and size.</p><p>We excavated five trenches in a small basin (Vestari Krubbsskál) located 5.5 km southeast of the town of Húsavík and at 300 m.a.s.l. and one trench in an alluvial fan (Traðargerði) located 0.5 km north of Húsavík and at 50 m.a.s.l. In a cold and wet environment, such as in coastal parts of Iceland, one has to take into account periglacial processes affecting the topsoil to discriminate tectonic from non-tectonic deformation. We used tephra layers in the Vestari Krubbsskál and Traðargerði trenches as well as birch wood samples in Traðargerði to constrain the timing of past earthquakes. Tephra layers Hekla-3 (2971 BP) and Hekla-4 (4331±20 BP) are visible in the top half of all the trenches. In addition, a few younger tephra layers are visible in the top part of the trenches. In Traðargerði several dark layers rich in organic matter are found, including birch wood-rich layers from the Earlier Birch Period (9000-7000 BP) and the Later Birch Period (5000-2500 BP). In Vestari Krubbsskál the lower halves of the trenches display mostly lacustrine deposits whereas in Traðargerði the lower half of the trench shows alluvial deposits overlaying coarser deposits (gravels/pebbles) most likely of late-glacial or early post-glacial origins. In addition, early Holocene tephra layers are observed in some of the trenches at both sites and may correspond to Askja-S (10800 BP), Saksunarvatn (10300 BP) and Vedde (12100 BP). These observations provide good age constraints and suggest that both the Vestari Krubbsskál and Traðargerði trenches cover the entire Holocene.</p><p>Trenches at both sites show significant normal deformation in addition to strike-slip, well correlated with their larger scale topographies (pull-apart basin in Vestari Krubbsskál and 45 m-high fault scarp in Traðargerði). We mapped layers, cracks and faults on all trench walls to build a catalogue of Holocene earthquakes. We identified events based on the upward terminations of the cracks and retrodeformation. Our results yield fewer major earthquakes than expected, suggesting that large earthquakes (around magnitude 7) are probably rare and the more typical HFF earthquakes of magnitude 6-6.5 likely produce limited topsoil deformation.[yk1]  Our interpretation also suggests that the Holocene slip rate [yk2] for the fault section we are studying may be slower than the estimated geodetic slip rate (6 to 9 mm/yr)[yk3]  for the entire onshore HFF, although secondary onshore sub-parallel fault strands could accommodate part of the deformation.</p>

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.

Bounds on the Average Recurrence Interval of Major Earthquakes Along the Haiyuan Fault In North-Central China

1988 ◽  
Vol 59 (3) ◽  
pp. 81-89 ◽  
Author(s):  
Zhang Peizhen ◽  
Peter Molnar ◽  
Zhang Weigi ◽  
Deng Qidong ◽  
Wang Yipeng ◽  
...  
Keyword(s):  
Slip Rate ◽  
Recurrence Interval ◽  
Central China ◽  
Great Earthquake ◽  
Average Amount ◽  
Earthquake Recurrence ◽  
Surface Rupture ◽  
North Central ◽  
Recurrence Intervals ◽  
Historic Record

Abstract Evidence of surface rupture has been found in trenches near Caiyuan and Shaomayin along the Haiyuan fault, where a great earthquake occurred in 1920. In addition to the 1920 earthquake, faulting occurred at least once between 2590 ± 190 years and 1525 ± 170 years B.P. in Caiyuan, and there probably was another event since 1525 ± 170 years B.P. The formation and later tilting of fault-related, scarp-derived colluvial wedges in the Shaomayin trench appear to record the occurrence of two pre-1920 events in the last 2200–3700 years, but there could have been three or more events. The average recurrence interval for great earthquakes along the Haiyuan fault probably exceeds 700 years, for the 1920 Haiyuan earthquake is the only major event to have been reported in this area in as many years of recorded history. Using a Holocene slip rate along this fault of 8 ± 2 mm/yr, and 8 m as the average amount of offset associated with past great events that have been determined by our previous studies, the resultant earthquake recurrence intervals would be from 800 to 1400 years. The results from our trenches and the historic record are consistent with this range.

Response of faults to climate-driven changes in ice and water volumes on Earth’s surface

2010 ◽  
Vol 368 (1919) ◽  
pp. 2501-2517 ◽  
Author(s):  
Andrea Hampel ◽  
Ralf Hetzel ◽  
Georgios Maniatis
Keyword(s):  
Rate Increase ◽  
Numerical Models ◽  
Ice Sheets ◽  
Slip Rate ◽  
Normal Faults ◽  
Basin And Range Province ◽  
Ice Caps ◽  
Last Glaciation ◽  
Earthquake Frequency ◽  
Water Volumes

Numerical models including one or more faults in a rheologically stratified lithosphere show that climate-induced variations in ice and water volumes on Earth’s surface considerably affect the slip evolution of both thrust and normal faults. In general, the slip rate and hence the seismicity of a fault decreases during loading and increases during unloading. Here, we present several case studies to show that a postglacial slip rate increase occurred on faults worldwide in regions where ice caps and lakes decayed at the end of the last glaciation. Of note is that the postglacial amplification of seismicity was not restricted to the areas beneath the large Laurentide and Fennoscandian ice sheets but also occurred in regions affected by smaller ice caps or lakes, e.g. the Basin-and-Range Province. Our results do not only have important consequences for the interpretation of palaeoseismological records from faults in these regions but also for the evaluation of the future seismicity in regions currently affected by deglaciation like Greenland and Antarctica: shrinkage of the modern ice sheets owing to global warming may ultimately lead to an increase in earthquake frequency in these regions.

Sign in / Sign up

Export Citation Format

Share Document