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 (<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.

Seismotectonic Snapshots: The 18 March 2020 Mw 5.7 Magna, 31 March 2020 Mw 6.5 Stanley, and 15 May 2020 Mw 6.5 Monte Cristo Intermountain West Earthquakes

2021 ◽  
Author(s):  
Steven G. Wesnousky
Keyword(s):  
Active Faults ◽  
Relative Size ◽  
Fault System ◽  
Intermountain West ◽  
Surface Rupture ◽  
Slip Mechanism ◽  
Walker Lane ◽  
Earthquake Ruptures ◽  
Seismic Networks ◽  
Broad Region

Abstract Seismological characteristics of the 18 March 2020 Mw 5.7 Magna, 31 March 2020 Mw 6.5 Stanley, and 15 May 2020 Mw 6.5 Monte Cristo Intermountain West earthquakes are largely consistent with expectations arising from observations accumulated over the ∼40  yr since implementation and subsequent growth of seismic networks in the broad region. Each occurred within a zone of relatively elevated seismicity, active faults, and geodetically observed strain accumulation. Aftershock distributions in each are confined primarily to depths of <15  km, and the total number of aftershocks correlates with the relative size of the events. In each case, the number per day decays exponentially in the days following the mainshock. None of the mainshocks was preceded by a foreshock sequence that delivered a plausible warning of the impending earthquakes. With respect to tectonics, each earthquake brings new insights. The Stanley and Monte Cristo earthquakes are at the margins of geodetically defined regions of right-lateral transtension, though the pattern of faulting in each region is markedly different. The strike-slip mechanism of the Stanley earthquake stands in contrast to the zone of normal major range bounding faults and historical earthquake ruptures that characterize the region in which it occurred and is the first relatively well instrumented event to show a rupture extending northward through the Trans-Challis fault system. The Magna event has been interpreted to represent low-angle normal slip near the base of a listric Wasatch range bounding fault (Pang et al., 2020). The east-striking left-lateral Monte Cristo earthquake within the Walker Lane is in contrast to the major northwest-striking right-lateral faults that dominate the area, though predictable from prior regional mapping. Surface rupture reportedly accompanied only the Monte Cristo earthquake, though its trace does not clearly follow the zone of aftershocks.

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

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

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

scholarly journals Preliminary paleoearthquake investigations of active faults on Awaji Island, Japan,
 in relation to the 1995 Great Hanshin (Kobe) earthquake

1996 ◽  
Vol 29 (3) ◽  
pp. 172-177
Author(s):  
R. Van Dissen ◽  
J. Begg ◽  
Y. Awata
Keyword(s):  
New Zealand ◽  
Active Fault ◽  
Active Faults ◽  
Geological Survey ◽  
Historical Records ◽  
Surface Rupture ◽  
Kobe Earthquake ◽  
Nojima Fault ◽  
One Year ◽  
Hanshin Earthquake

Approximately one year after the Great Hanshin (Kobe) Earthquake, two New Zealand geologists were invited to help with the Geological Survey of Japan's paleoearthquake/active fault studies in the Kobe/Awaji area. Trenches excavated across the Nojima fault, which ruptured during the Great Hanshin Earthquake, showed evidence of past surface rupture earthquakes, with the age of the penultimate earthquake estimated at approximately 2000 years. A trench across the Higashiura fault, located 3-4 km southeast of the Nojima fault, revealed at least two past surface rupture earthquakes. The timing of the older earthquakes is not yet known, but pottery fragments found in the trench constrain the timing of the most recent earthquake at less than 500-600 years. Historical records for this part of Japan suggest that within the last 700 years there has been only one regionally felt earthquake prior to the 1995 Great Hanshin Earthquake, and this was the AD 1596 Keicho Earthquake. It thus seems reasonable to suggest that the Higashiura fault was, at least in part, the source of the AD 1596 Keicho Earthquake.

Do active faults’ clay mineral compositions affect whether earthquake ruptures they host will displace the surface?

2021 ◽  
Author(s):  
Selina S. Fenske ◽  
Virginia G. Toy ◽  
Bernhard Schuck ◽  
Anja M. Schleicher ◽  
Klaus Reicherter
Keyword(s):  
Fault Zone ◽  
Clay Mineral ◽  
Active Faults ◽  
Surface Displacement ◽  
Surface Rupture ◽  
Near Surface ◽  
Ground Shaking ◽  
Physical Measurements ◽  
Surface Displacements ◽  
Earthquake Ruptures

<p>The tectonophysical paradigm that earthquake ruptures should not start, or easily propagate into, the shallowest few kilometers of Earth’s crust makes it difficult to understand why damaging surface displacements have occurred during historic events. The paradigm is supported by decades of analyses demonstrating that near the surface, most major fault zones are composed of clay minerals – particularly extraordinarily weak smectites – which most laboratory physical measurements suggest should prevent surface rupture if present. Recent studies of New Zealand’s Alpine Fault Zone (AFZ) demonstrate smectites are absent from some near surface fault outcrops, which may explain why this fault was able to offset the surface locally in past events. The absence of smectites in places within the AFZ can be attributed to locally exceptionally high geothermal gradients related to circulation of meteoric (surface-derived) water into the fault zone, driven by significant topographic gradients. The record of surface rupture of the AFZ is heterogeneous, and no one has yet systematically examined the distribution of segments devoid of evidence for recent displacement. There are significant implications for seismic hazard, which comprises both surface displacements and ground shaking with intensity related to the area of fault plane that ruptures (which will be reduced if ruptures do not reach the surface).  We will present results of new rigorous XRD clay mineral analyses of AFZ principal slip zone gouges that indicate where smectites are present, and consider if these display systematic relationships to surface displacement records. We also plan to apply the same methodology to the Carboneras Fault Zone in Spain, and the infrequent Holocene-active faults in Western Germany.</p>

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 Surface Faulting Caused by the 2016 Central Italy Seismic Sequence: Field Mapping and LiDAR/UAV Imaging

2018 ◽  
Vol 34 (4) ◽  
pp. 1585-1610 ◽  
Author(s):  
Stefano Gori ◽  
Emanuela Falcucci ◽  
Fabrizio Galadini ◽  
Paolo Zimmaro ◽  
Alberto Pizzi ◽  
...  
Keyword(s):  
Imaging Techniques ◽  
Central Italy ◽  
Normal Fault ◽  
Fault System ◽  
Surface Rupture ◽  
Field Mapping ◽  
Central Italy Earthquake ◽  
Levels Of Detail ◽  
Main Fault ◽  
Surface Ruptures

The three mainshock events (M6.1 24 August, M5.9 26 October, and M6.5 30 October 2016) in the Central Italy earthquake sequence produced surface ruptures on known segments of the Mt. Vettore–Mt. Bove normal fault system. As a result, teams from Italian national research institutions and universities, working collaboratively with the U.S. Geotechnical Extreme Events Reconnaissance Association (GEER), were mobilized to collect perishable data. Our reconnaissance approach included field mapping and advanced imaging techniques, both directed towards documenting the location and extent of surface rupture on the main fault exposure and secondary features. Mapping activity occurred after each mainshock (with different levels of detail at different times), which provides data on the progression of locations and amounts of slip between events. Along the full length of the Mt. Vettore–Mt. Bove fault system, vertical offsets ranged from 0–35 cm and 70–200 cm for the 24 August and 30 October events, respectively. Comparisons between observed surface rupture displacements and available empirical models show that the three events fit within expected ranges.

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 The San Andreas Fault Paleoseismic Record at Elizabeth Lake: Why are There Fewer Surface-Rupturing Earthquakes on the Mojave Section?

2021 ◽  
Author(s):  
Sean P. Bemis ◽  
Kate Scharer ◽  
James F. Dolan
Keyword(s):  
San Andreas Fault ◽  
Active Faults ◽  
Structural Complexity ◽  
Plate Motion ◽  
Fault System ◽  
San Andreas ◽  
Time Period ◽  
Earthquake Ruptures ◽  
Major Fault ◽  
Restraining Bend

ABSTRACT The structural complexity of active faults and the stress release history along the fault system may exert control on the locus and extent of individual earthquake ruptures. Fault bends, in particular, are often invoked as a possible mechanism for terminating earthquake ruptures. However, there are few records available to examine how these factors may influence the along-fault recurrence of earthquakes. We present a new paleoearthquake chronology for the southern San Andreas fault at Elizabeth Lake and integrate this record with existing paleoearthquake records to examine how the timing and frequency of earthquakes vary through a major restraining bend. This restraining bend features a mature, throughgoing right-lateral strike-slip fault, two major fault intersections, proposed subsurface fault dip changes, and a >200  km long section of fault misaligned with the regional plate motion. The Frazier Mountain, Elizabeth Lake, Pallett Creek, Wrightwood, and Pitman Canyon paleoseismic sites are located on this relatively linear surface trace of the San Andreas fault between fault bends. Our paleoseismic investigations at Elizabeth Lake document 4–5 earthquakes, since ∼1100  C.E., similar to the number of earthquakes recorded at Pallett Creek. In contrast, the Frazier Mountain and Wrightwood sites each record 8–9 earthquakes during this same time period. Differences in earthquake frequency demonstrate that fewer earthquakes rupture the central portion of the restraining bend than occur near the fault bends and intersections. Furthermore, the similarity of earthquake records from the Bidart Fan paleoseismic site northwest of the restraining bend and the Frazier Mountain paleoseismic site suggests that the broad, 30° curve of the Big Bend section of the San Andreas fault exerts less influence on fault rupture behavior than the 3D geometry of the Mojave sections of the fault.

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 Revision of the geological context of the Port-au-Prince, Haiti, metropolitan area: implications for seismic microzonation

2014 ◽  
Vol 2 (2) ◽  
pp. 1613-1635
Author(s):  
M. Terrier ◽  
A. Bialkowski ◽  
A. Nachbaur ◽  
C. Prépetit ◽  
Y. F. Joseph
Keyword(s):  
Metropolitan Area ◽  
Seismic Risk ◽  
Morphological Analysis ◽  
Active Faults ◽  
Seismic Microzonation ◽  
Ground Movement ◽  
Fault System ◽  
Surface Rupture ◽  
Development Policies ◽  
The Impact

Abstract. A geological study has been conducted in the framework of the microzonation of Portau- Prince, Haiti. It reveals the deposit of Miocene and Pliocene formations in a marine environment and the impact on these deposits of the Enriquillo-Plantain Garden N80° E fault system and of N110° E faults. The tectonic and morphological analysis indicates motion during the Quaternary along several mapped reverse left-lateral N110° E faults affecting the capital. Assessing ground-movement hazards represents an integral component of seismic microzonation. The geological results have provided essential groundwork for this assessment. Seismic microzonation aims to take seismic risk more fully into account in the city's urbanization and development policies. To this end, assumptions are made as to risks induced by surface rupture and ground movement from active faults.

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