Magnitude Recurrence Relations for Colorado Earthquakes

2002 ◽  
Vol 18 (2) ◽  
pp. 233-250 ◽  
Author(s):  
Wayne A. Charlie ◽  
Raymond J. Battalora ◽  
Thomas J. Siller ◽  
Donald O. Doehring
Keyword(s):  
Recurrence Relations ◽  
Active Faults ◽  
Geological Survey ◽  
Fluid Injection ◽  
Historical Earthquake ◽  
Induced Earthquakes ◽  
Slip Rates ◽  
Probability Of Exceedance ◽  
Maximum Credible Earthquake ◽  
Significant Potential

Colorado has a significant potential for damaging earthquakes. The Colorado Geological Survey has identified 92 potentially active faults. Two faults have documented slip-rates approaching 1 mm per year. Four hundred and seventy-seven Colorado earthquakes have been felt and/or equaled or exceeded magnitude of 2.0 between 1870 and 1996. Eighty-two earthquakes have equaled or exceeded an MMI Scale of V. Colorado's largest historical earthquake, which occurred on 7 November 1882 (8 November UCT), had an estimated magnitude of 6.5 and maximum MMI of VII to VIII. Colorado's maximum credible earthquake has been estimated at 7.5 ML. In this paper we analyze independent earthquakes (foreshocks, aftershocks, and fluid-injection induced earthquakes removed) to develop magnitude-recurrence relations. Analysis of instrumentally measured earthquakes predicts that a 6.5 ML or larger earthquake occurring somewhere in Colorado has a mean recurrence interval of about 420 years. A magnitude 6.6 ML earthquake has a 10 percent Poisson's probability of exceedance in 50 years. A 7.5 ML earthquake has a 2 percent Poisson's probability of exceedance in 50 years. Colorado's magnitude-recurrence (Gutenberg-Richter) relation is log N=2.58−0.80 ML.

More Than 40 yr of Potentially Induced Seismicity Close to the San Andreas Fault in San Ardo, Central California

2020 ◽  
Vol 92 (1) ◽  
pp. 187-198
Author(s):  
Thomas H. W. Goebel ◽  
Manoochehr Shirzaei
Keyword(s):  
Induced Seismicity ◽  
Surface Deformation ◽  
Active Faults ◽  
Stress Transfer ◽  
Correlation Coefficients ◽  
Spatial Proximity ◽  
Fluid Injection ◽  
Induced Earthquakes ◽  
Temporal Correlations ◽  
Stress Changes

Abstract Evidence for fluid-injection-induced seismicity is rare in California hydrocarbon basins, despite widespread injection close to seismically active faults. We investigate a potential case of injection-induced earthquakes associated with San Ardo oilfield operations that began in the early 1950s. The largest potentially induced events occurred in 1955 (ML 5.2) and 1985 (Mw 4.5) within ∼6  km from the oilfield. We analyze Synthetic Aperture Radar interferometric images acquired by Sentinel-1A/B satellites between 2016 and 2020 and find surface deformation of up to 1.5  cm/yr, indicating pressure-imbalance in parts of the oilfield. Fluid injection in San Ardo is concentrated within highly permeable rocks directly above the granitic basement at a depth of ∼800  m. Seismicity predominantly occurs along basement faults at 6–13 km depths. Seismicity and wastewater disposal wells are spatially correlated to the north of the oilfield. Temporal correlations are observed over more than 40 yr with correlation coefficients of up to 0.71 for seismicity within a 24 km distance from the oilfield. Such large distances have not previously been observed in California but are similar to the large spatial footprint of injection in Oklahoma. The San Ardo seismicity shows anomalous clustering with earthquakes consistently occurring at close spatial proximity but long interevent times. Similar clustering has previously been reported in California geothermal fields and may be indicative of seismicity driven by long-term, spatially persistent external forcing. The complexity of seismic behavior at San Ardo suggests that multiple processes, such as elastic stress transfer and aseismic slip transients, contribute to the potentially induced earthquakes. The present observations show that fluid-injection operations occur close to seismically active faults in California. Yet, seismicity is predominantly observed on smaller unmapped faults with little observational evidence that large faults are sensitive to induced stress changes.

Slip rates along active faults estimated with cosmic-ray–exposure dates: Application to the Bogd fault, Gobi-Altaï, Mongolia

Geology ◽  
1995 ◽  
Vol 23 (11) ◽  
pp. 1019 ◽  
Author(s):  
J. F. Ritz ◽  
E. T. Brown ◽  
D. L. Bourlès ◽  
H. Philip ◽  
A. Schlupp ◽  
...  
Keyword(s):  
Active Faults ◽  
Cosmic Ray ◽  
Slip Rates

scholarly journals Active Fault Systems in the Inner Northwest Apennines, Italy: A Reappraisal One Century after the 1920 Mw ~6.5 Fivizzano Earthquake

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 139
Author(s):  
Giancarlo Molli ◽  
Isabelle Manighetti ◽  
Rick Bennett ◽  
Jacques Malavieille ◽  
Enrico Serpelloni ◽  
...  
Keyword(s):  
Large Scale ◽  
Active Fault ◽  
Active Faults ◽  
Dense Network ◽  
Earthquake Fault ◽  
Slip Rates ◽  
Fault Systems ◽  
Seismological Data ◽  
Seismogenic Faults

Based on the review of the available stratigraphic, tectonic, morphological, geodetic, and seismological data, along with new structural observations, we present a reappraisal of the potential seismogenic faults and fault systems in the inner northwest Apennines, Italy, which was the site, one century ago, of the devastating Mw ~6.5, 1920 Fivizzano earthquake. Our updated fault catalog provides the fault locations, as well as the description of their architecture, large-scale segmentation, cumulative displacements, evidence for recent to present activity, and long-term slip rates. Our work documents that a dense network of active faults, and thus potential earthquake fault sources, exists in the region. We discuss the seismogenic potential of these faults, and propose a general tectonic scenario that might account for their development.

scholarly journals Tectonic Geomorphology and Paleoseismology of the Sharkhai fault: a new source of seismic hazard for Ulaanbaatar (Mongolia)

2021 ◽  
Author(s):  
Abeer Al-Ashkar ◽  
Antoine Schlupp ◽  
Matthieu Ferry ◽  
Ulziibat Munkhuu
Keyword(s):  
Seismic Hazard ◽  
Scaling Laws ◽  
Active Faults ◽  
Seismic Hazard Assessment ◽  
Capital City ◽  
Tectonic Geomorphology ◽  
Time Interval ◽  
Coseismic Slip ◽  
Slip Rates ◽  
Large Earthquakes

Abstract. We present new constraints from tectonic geomorphology and paleoseismology along the newly discovered Sharkhai fault near the capital city of Mongolia. Detailed observations from high resolution Pleiades satellite images and field investigations allowed us to map the fault in detail, describe its geometry and segmentation, characterize its kinematics, and document its recent activity and seismic behavior (cumulative displacements and paleoseismicity). The Sharkhai fault displays a surface length of ~40 km with a slightly arcuate geometry, and a strike ranging from N42° E to N72° E. It affects numerous drainages that show left-lateral cumulative displacements reaching 57 m. Paleoseismic investigations document the faulting and deposition record for the last ~3000 yr and reveal that the penultimate earthquake (PE) occurred between 1515 ± 90 BC and 945 ± 110 BC and the most recent event (MRE) occurred after 860 ± 85 AD. The resulting time interval of 2080 ± 470 years is the first constraint on the Sharkhai fault for large earthquakes. On the basis of our mapping of the surface rupture and the resulting segmentation analysis, we propose two possible scenarios for large earthquakes with likely magnitudes between 6.4 ± 0.2 and 7.1 ± 0.2. Furthermore, we apply scaling laws to infer coseismic slip values and derive preliminary estimates of long-term slip rates between 0.2 ± 0.2 and 1.0 ± 0.5 mm/y. Finally, we propose that these original observations and results from a newly discovered fault should be taken into account for the seismic hazard assessment for the city of Ulaanbaatar and help build a comprehensive model of active faults in that region.

scholarly journals The active tectonic landscape of Lake Ohrid (FYR of Macedonia/Albania)

2014 ◽  
Vol 56 (6) ◽  
Author(s):  
Nadine Hoffmann
Keyword(s):  
Active Faults ◽  
Fault Scarp ◽  
Mass Wasting ◽  
Lake Ohrid ◽  
Slip Rates ◽  
Active Tectonic ◽  
Western Border ◽  
Wine Glass ◽  
Yugoslavian Republic ◽  
Fault Scarps

<p><span style="font-family: CMR10; font-size: medium;">The study area at the Lake Ohrid Basin is located on 693 m a.s.l. at the south-western border of the Former Yugoslavian Republic of Macedonia with Albania. It is a suitable location for neotectonic studies. It exhibits a large variety of morphological expressions associated with the seismic activity of the region. Linear bedrock fault scarps give the relief on both sides of the lake a staircase-like appearance; other features are wine-glass shaped valleys and triangular facets. These often short living features are used to identify active faults and to parameterise palaeoearthquakes (slip rates, subsidence and erosion). According to the results of fault scarp profiling a halfgraben shape of the basin is proposed with the west coast being dominated by mass wasting processes most likely triggered by seismic events.</span></p>

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.

scholarly journals Project SUPRASYD 1993 - granitic rocks and shear zones with possible gold potential, Julianehåb batholith, South Greenland

1994 ◽  
Vol 160 ◽  
pp. 28-31
Author(s):  
A.A Garde ◽  
H.K Schønwandt
Keyword(s):  
East Coast ◽  
Economic Assessment ◽  
Shear Zones ◽  
Geological Survey ◽  
Granitic Rocks ◽  
Significant Potential ◽  
Metavolcanic Rocks ◽  
Sulphide Deposits ◽  
Important Constituent

In 1992 the Geological Survey of Greenland (GGU) initiated the project SUPRASYD in order to carry out an economic assessment of the Ketilidian orogen in South Greenland, especially the supracrustal rocks in the southern and eastern parts of the orogen (see Dawes & Schønwandt, 1992). Geological investigations in the area east of Nanortalik and along the east coast of South Greenland as far as 62°N had previously indicated that acid metavolcanic rocks were an important constituent of the supracrustal rocks, and it was therefore expected that the region might have a significant potential for sulphide deposits.

Maximum Magnitude Estimation for An Intraplate Setting - Example: The Giles County, Virginia, Seismic Zone

1992 ◽  
Vol 63 (2) ◽  
pp. 139-152 ◽  
Author(s):  
G. A. Bollinger ◽  
M. S. Sibol ◽  
M. C. Chapman
Keyword(s):  
Magnitude Estimation ◽  
Recurrence Relations ◽  
Value Theory ◽  
Seismogenic Zone ◽  
Maximum Magnitude ◽  
Seismic Zone ◽  
Historical Earthquake ◽  
Data Bases ◽  
Source Dimensions ◽  
Global Data

Abstract The process of maximum magnitude estimation is intrinsically subjective and depends directly on the experience and judgment of the analyst. Coppersmith et al. (1987; Table 1) discuss six methods for determining the maximum magnitude earthquake for a seismogenic zone. Those include: (I) Addition of an increment to the largest historical earthquake, (II) Extrapolation of magnitude recurrence relations, (III) Use of source dimensions to estimate magnitude, (IV) Statistical approaches (application of extreme value theory and maximum likelihood techniques), (V) Strain rate or moment release rate methods, and (VI) Reference to a global data base. Each technique has associated uncertainties in its applicability to the zone under consideration as well as in the specification of the key parameters involved. Of the six techniques listed above, only the first three are applicable to the data bases presently available for intraplate areas. Application of methods I, II, and III, to the Giles County, Virginia, seismic zone leads to the following results: MS,I = 6.9 (second subscript indicating which of the six methods was used) from adding a 1.0 increment to the maximum historical earthquake known to have occurred in the zone (May 31, 1897; MMI = VIII; mb = 5.8, MS = 5.9), MS,II = 7.0 from extension of the magnitude recurrence curve for the zone to a recurrence interval of 1000 years, and MS,III = 6.5 from the average of six estimates for the fault zone area. For a single estimate of maximum magnitude, the average of the above three values MS = 6.8 or equivalently, mb = 6.3 can be used.

Postglacial faulting near Crater Lake, Oregon, and its possible association with the Mazama caldera-forming eruption

2019 ◽  
Vol 131 (9-10) ◽  
pp. 1440-1458
Author(s):  
Charles R. Bacon ◽  
Joel E. Robinson
Keyword(s):  
Crater Lake ◽  
Active Faults ◽  
Large Earthquake ◽  
Normal Displacement ◽  
Normal Faults ◽  
Caldera Collapse ◽  
Normal Extension ◽  
Slip Rates ◽  
Crater Lake National Park ◽  
Lateral Offset

Abstract Volcanoes of subduction-related magmatic arcs occur in a variety of crustal tectonic regimes, including where active faults indicate arc-normal extension. The Cascades arc volcano Mount Mazama overlaps on its west an ∼10-km-wide zone of ∼north-south–trending normal faults. A lidar (light detection and ranging) survey of Crater Lake National Park, reveals several previously unrecognized faults west of the caldera. Postglacial vertical separations measured from profiles across scarps range from ∼2 m to as much as 12 m. Scarp profiles commonly suggest two or more postglacial surface-rupturing events. Ignimbrite of the ca. 7.6 ka climactic eruption of Mount Mazama, during which Crater Lake caldera formed, appears to bury fault strands where they project into thick, valley-filling ignimbrite. Lack of lateral offset of linear features suggests principally normal displacement, although predominant left stepping of scarp strands implies a component of dextral slip. West-northwest–east-southeast and north-northwest–south-southeast linear topographic elements, such as low scarps or ridges, shallow troughs, and straight reaches of streams, suggest that erosion was influenced by distributed shear, consistent with GPS vectors and clockwise rotation of the Oregon forearc block. Surface rupture lengths (SRL) of faults suggest earthquakes of (moment magnitude) Mw6.5 from empirical scaling relationships. If several faults slipped in one event, a combined SRL of 44 km suggests an earthquake of Mw7.0. Postglacial scarps as high as 12 m imply maximum vertical slip rates of 1.5 mm/yr for the zone west of Crater Lake, considerably higher than the ∼0.3 mm/yr long-term rate for the nearby West Klamath Lake fault zone. An unanswered question is the timing of surface-rupturing earthquakes relative to the Mazama climactic eruption. The eruption may have been preceded by a large earthquake. Alternatively, large surface-rupturing earthquakes may have occurred during the eruption, a result of decrease in east-west compressive stress during ejection of ∼50 km3 of magma and concurrent caldera collapse.

scholarly journals Integrating faults and past earthquakes into a probabilistic seismic hazard model for peninsular Italy

2017 ◽  
Vol 17 (11) ◽  
pp. 2017-2039 ◽  
Author(s):  
Alessandro Valentini ◽  
Francesco Visini ◽  
Bruno Pace
Keyword(s):  
Seismic Hazard ◽  
Seismic Activity ◽  
Grid Point ◽  
Active Faults ◽  
Gaussian Model ◽  
Probabilistic Seismic Hazard ◽  
Maximum Magnitude ◽  
Slip Rates ◽  
Earthquake Sources ◽  
The Impact

Abstract. Italy is one of the most seismically active countries in Europe. Moderate to strong earthquakes, with magnitudes of up to ∼ 7, have been historically recorded for many active faults. Currently, probabilistic seismic hazard assessments in Italy are mainly based on area source models, in which seismicity is modelled using a number of seismotectonic zones and the occurrence of earthquakes is assumed uniform. However, in the past decade, efforts have increasingly been directed towards using fault sources in seismic hazard models to obtain more detailed and potentially more realistic patterns of ground motion. In our model, we used two categories of earthquake sources. The first involves active faults, and using geological slip rates to quantify the seismic activity rate. We produced an inventory of all fault sources with details of their geometric, kinematic, and energetic properties. The associated parameters were used to compute the total seismic moment rate of each fault. We evaluated the magnitude–frequency distribution (MFD) of each fault source using two models: a characteristic Gaussian model centred at the maximum magnitude and a truncated Gutenberg–Richter model. The second earthquake source category involves grid-point seismicity, with a fixed-radius smoothed approach and a historical catalogue were used to evaluate seismic activity. Under the assumption that deformation is concentrated along faults, we combined the MFD derived from the geometry and slip rates of active faults with the MFD from the spatially smoothed earthquake sources and assumed that the smoothed seismic activity in the vicinity of an active fault gradually decreases by a fault-size-driven factor. Additionally, we computed horizontal peak ground acceleration (PGA) maps for return periods of 475 and 2475 years. Although the ranges and gross spatial distributions of the expected accelerations obtained here are comparable to those obtained through methods involving seismic catalogues and classical zonation models, the spatial pattern of the hazard maps obtained with our model is far more detailed. Our model is characterized by areas that are more hazardous and that correspond to mapped active faults, while previous models yield expected accelerations that are almost uniformly distributed across large regions. In addition, we conducted sensitivity tests to determine the impact on the hazard results of the earthquake rates derived from two MFD models for faults and to determine the relative contributions of faults versus distributed seismic activity. We believe that our model represents advancements in terms of the input data (quantity and quality) and methodology used in the field of fault-based regional seismic hazard modelling in Italy.

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