Seismicity Rate Change at the Coso Geothermal Field Following the July 2019 Ridgecrest Earthquakes

2020 ◽  
Vol 110 (4) ◽  
pp. 1728-1735 ◽  
Author(s):  
J. Ole Kaven
Keyword(s):  
Geothermal Field ◽  
Rate Change ◽  
Local Network ◽  
Surrounding Area ◽  
Regional Network ◽  
Seismicity Rate ◽  
The North ◽  
Brittle Ductile Transition ◽  
Seismicity Rates ◽  
Coso Geothermal Field

ABSTRACT Many geothermal and volcanic regions experience remote and regional triggering following large earthquakes. The transient or permanent changes in stresses acting on faults and fractures can lead to changes in seismicity rates following either the passage of teleseismic waves or the permanent change in stresses following regional events. One such region of prevalent triggering is the Coso Geothermal Field (CGF) in eastern California, which is located roughly 30 km to the north of the 2019 Mw 7.1 Ridgecrest epicenter. Previous regional earthquakes have not only seemingly caused increase in seismicity rate surrounding the CGF, but also showed an absence of such rate increases in the CGF itself. To test whether seismicity rates in the CGF were dissimilar to the surrounding area following the Mw 7.1 Ridgecrest earthquake, I carry out seismicity rate change calculations using a catalog of seismicity compiled using a local seismic network and find that the behavior at CGF is identical to the surrounding area. Comparisons of seismicity rate changes calculated using a regional-network-derived catalog, and the local-network-derived catalog show that for a moderate, regional earthquake (2009 Mw 5.2 Olancha, California), the local network catalog reveals a change in seismicity rate whereas the regionally network catalog shows no significant changes. The differences are possibly related to incomplete sampling of seismicity using the regional network due to the existence of a shallow brittle–ductile transition centered on the CGF. The CGF, thus, is prone to triggering from both teleseismic and regional earthquakes.

Seismic quiescence, stress drops, and asperities in the New Hebrides arc

1983 ◽  
Vol 73 (1) ◽  
pp. 219-236
Author(s):  
M. Wyss ◽  
R. E. Habermann ◽  
Ch. Heiniger
Keyword(s):  
High Stress ◽  
Plate Boundary ◽  
Seismic Quiescence ◽  
Data Set ◽  
Seismicity Rate ◽  
Seismic Gaps ◽  
Main Shocks ◽  
Seismicity Rates ◽  
New Hebrides ◽  
Stress Drops

abstract The rate of occurrence of earthquakes shallower than 100 km during the years 1963 to 1980 was studied as a function of time and space along the New Hebrides island arc. Systematic examination of the seismicity rates for different magnitude bands showed that events with mb < 4.8 were not reported consistently over time. The seismicity rate as defined by mb ≧ 4.8 events was examined quantitatively and systematically in the source volumes of three recent main shocks and within two seismic gaps. A clear case of seismic quiescence could be shown to have existed before one of the large main shocks if a major asperity was excluded from the volume studied. The 1980 Ms = 8 rupture in the northern New Hebrides was preceded by a pattern of 9 to 12 yr of quiescence followed by 5 yr of normal rate. This pattern does not conform to the hypothesis that quiescence lasts up to the mainshock which it precedes. The 1980 rupture also did not fully conform to the gap hypothesis: half of its aftershock area covered part of a great rupture which occurred in 1966. A major asperity seemed to play a critical role in the 1966 and 1980 great ruptures: it stopped the 1966 rupture, and both parts of the 1980 double rupture initiated from it. In addition, this major asperity made itself known by a seismicity rate and stress drops higher than in the surrounding areas. Stress drops of 272 earthquakes were estimated by the MS/mb method. Time dependence of stress drops could not be studied because of changes in the world data set of Ms and mb values. Areas of high stress drops did not correlate in general with areas of high seismicity rate. Instead, outstandingly high average stress drops were observed in two plate boundary segments with average seismicity rate where ocean floor ridges are being subducted. The seismic gaps of the central and northern New Hebrides each contain seismically quiet regions. In the central New Hebrides, the 50 to 100 km of the plate boundary near 18.5°S showed an extremely low seismicity rate during the entire observation period. Low seismicity could be a permanent property of this location. In the northern New Hebrides gap, seismic quiescence started in mid-1972, except in a central volume where high stress drops are observed. This volume is interpreted as an asperity, and the quiescence may be interpreted as part of the preparation process to a future large main shock near 13.5°S.

Sierra Nevada-Great Basin boundary zone: Earthquake hazard related to structure, active tectonic processes, and anomalous patterns of earthquake occurrence

1980 ◽  
Vol 70 (5) ◽  
pp. 1557-1572
Author(s):  
J. D. VanWormer ◽  
Alan S. Ryall
Keyword(s):  
Sierra Nevada ◽  
Great Basin ◽  
Temporal Variations ◽  
Mono Lake ◽  
Local Network ◽  
Low Velocity ◽  
Owens Valley ◽  
Walker Lake ◽  
Fault Plane Solutions ◽  
The North

abstract Precise epicentral determinations based on local network recordings are compared with mapped faults and volcanic features in the western Great Basin. This region is structurally and seismically complex, and seismogenic processes vary within it. In the area north of the rupture zone of the 1872 Owens Valley earthquake, dispersed clusters of epicenters agree with a shatter zone of faults that extend the 1872 breaks to the north and northwest. An area of frequent earthquake swarms east of Mono Lake is characterized by northeast-striking faults and a crustal low-velocity zone; seismicity in this area appears to be related to volcanic processes that produced thick Pliocene basalt flows in the Adobe Hills and minor historic activity in Mono Lake. In the Garfield Hills between Walker Lake and the Excelsior Mountains, there is some clustering of epicenters along a north-trending zone that does not correlate with major Cenozoic structures. In an area west of Walker Lake, low seismicity supports a previous suggestion by Gilbert and Reynolds (1973) that deformation in that area has been primarily by folding and not by faulting. To the north, clusters of earthquakes are observed at both ends of a 70-km-long fault zone that forms the eastern boundary of the Sierra Nevada from Markleeville to Reno. Clusters of events also appear at both ends of the Dog Valley Fault in the Sierra west of Reno, and at Virginia City to the east. Fault-plane solutions for the belt in which major earthquakes have occurred in Nevada during the historic period (from Pleasant Valley in the north to the Excelsior Mountains on the California-Nevada Border) correspond to normaloblique slip and are similar to that found by Romney (1957) for the 1954 Fairview Peak shock. However, mechanisms of recent moderate earthquakes within the SNGBZ are related to right- or left-lateral slip, respectively, on nearly vertical, northwest-, or northeast-striking planes. These mechanisms are explained by a block faulting model of the SNGBZ in which the main fault segments trend north, have normal-oblique slip, and are offset or terminated by northwest-trending strike-slip faults. This is supported by the observation that seismicity during the period of observation has been concentrated at places where major faults terminate or intersect. Anomalous temporal variations, consisting of a general decrease in seismicity in the southern part of the SNGBZ from October 1977 to September 1978, followed by a burst of moderate earthquakes that has continued for more than 18 months, is suggestive of a pattern that several authors have identified as precursory to large earthquakes. The 1977 to 1979 variations are particularly noteworthy because they occurred over the entire SNGBZ, indicating a regional rather than local cause for the observed changes.

Ugliness and Beauty: the Politics of Landscape in Walter Greenwood's Love on the Dole

2013 ◽  
Vol 29 (1) ◽  
pp. 35-47
Author(s):  
Claire Warden
Keyword(s):  
Twentieth Century ◽  
Working Class ◽  
The Other ◽  
Surrounding Area ◽  
North West ◽  
Avant Garde ◽  
The North ◽  
The One ◽  
The University ◽  
Open Fields

The multi-spatial landscape of the North-West of England (Manchester–Salford and the surrounding area) provides the setting for Walter Greenwood's 1934 play Love on the Dole. Both the urban industrialized cityscape and the rural countryside that surrounds it are vital framing devices for the narrative – these spaces not simply acting as backdrops but taking on character roles. In this article Claire Warden reads the play's presentation of the North through the concept of landscape theatre, on the one hand, and Raymond Williams's city–country dialogism on the other, claiming that Love on the Dole is imbued with the revolutionary possibility that defines the very landscape in which it is set. From claustrophobic working-class kitchen to the open fields of Derbyshire, Love on the Dole has a sense of spatial ambition in which Greenwood regards all landscapes as tainted by the industrial world while maintaining their capacity to function independently. Ugliness and beauty, capitalist hegemony and socialistic hopefulness reside simultaneously in this important under-researched example of twentieth-century British theatre, thereby reflecting the ambivalent, shifting landscape of the North and producing a play that cannot be easily defined artistically or politically. Claire Warden is a Lecturer in Drama at the University of Lincoln. Her work focuses on peripheral British performances in the early to mid-twentieth century. She is the author of British Avant-Garde Theatre (Palgrave MacMillan, 2012) and is currently writing Modernist and Avant-Garde Performance: an Introduction for Edinburgh University Press, to be published in 2014.

scholarly journals Geothermal field and geology of the Caspian Sea region

2019 ◽  
pp. 104-118 ◽  
Author(s):  
Vladimir I. Zui ◽  
Siamak Mansouri Far Far
Keyword(s):  
Heat Flow ◽  
Flow Pattern ◽  
Caspian Sea ◽  
Sedimentary Basins ◽  
Geothermal Field ◽  
Flow Density ◽  
General Tendency ◽  
The Caspian Sea ◽  
Northern Iran ◽  
The North

The Caspian Sea and adjacent areas form the vast oil and gas-bearing megabasin. It consists of North Caspian, Middle Caspian, and South Caspian sedimentary basins. The granite-metamorphic basement of the basins becomes from north to south younger in the direction from Early Precambrian to Early Cimmerian age. It represents a transitional zone from the southern edge of the East European Craton to Alpine folding. Geothermal investigations have been carried out both in hundreds of deep boreholes and within the Caspian Sea and a few preliminary heat flow maps were published for the Caspian Sea region. All they excluded from consideration the southern part of the region within Iranian national borders. We prepared a new heat flow map including the northern Iran. The purpose of the article is to consider heat flow pattern within the whole Caspian Sea region including its southern part. Two vast high heat flow anomalies above 100 mW/m2 distinguished in the map: within the southwestern Iran and in waters of the Caspian Sea to the North of the Apsheron Ridge, separated by elongated strip of heat flow below 50 –55 mW/m 2 . A general tendency of heat flow from growing was distinguished from the Precambrian crustal blocks of the North Caspian Depression to the Alpine folding within the territory of Iran. Analysis of the heat flow pattern is discussed and two heat flow density profiles were compiled.

Archaeological works to the north of the Great Amun temple at Jebel Barkal (Sudan): preliminary results and new perspectives

2021 ◽  
pp. 36
Author(s):  
Maxim A. Lebedev
Keyword(s):  
Archaeological Research ◽  
Surrounding Area ◽  
Preliminary Results ◽  
The North ◽  
Actual Nature ◽  
Political Center ◽  
History Of ◽  
Field Season ◽  
Special Mention ◽  
The Temple

The paper presents preliminary results and discusses future perspectives on archaeological research in the area to the north of the Great Amun temple at Jebel Barkal (Napata) in connection to the most recent excavations of elite Meroitic structure B 1700. The field season of 2020 at B 1700 continued to bring to light a new monumental foundation platform of the cellular type constructed for a building which function and meaning remain a subject for debate. The now available data suggest that B 1700 followed the classic Meroitic square plan with rooms arranged around a central columned space, utility chambers on the ground floor, and official areas on the upper floor(s). Paper discusses general features of the exposed plan of B 1700, the process of its construction, recorded archaeological matrix, and finds. Special mention is made of the brick masonry, earlier occupation phase, later activities at the site, and the great pottery dump which was extensively used in the fill of the foundation platform. The author argues that elite building B 1700 was probably constructed at the time of king Natakamani (1 century AD) – one of the most known Kushite rulers of the Classic Meroitic period – and did not continue functioning for more than, probably, one century. The study of B 1700 and its surrounding area has a considerable significance for reconstructing the history of the development of the temple and royal zone to the north of the temenos of the Great Amun temple at Jebel Barkal as well as provide new data on the actual nature of Napata as an economic and political center of Meroitic Kush.  

Recent earthquake sequences at Coso: Evidence for conjugate faulting and stress loading near a geothermal field

1999 ◽  
Vol 89 (3) ◽  
pp. 785-795 ◽  
Author(s):  
Joydeep Bhattacharyya ◽  
Susanna Gross ◽  
Jonathan Lees ◽  
Mike Hastings
Keyword(s):  
Geothermal Field ◽  
Fault System ◽  
Fault Plane Solutions ◽  
Temporal Decay ◽  
Background Seismicity ◽  
Surface Ruptures ◽  
Temporal And Spatial Characteristics ◽  
Coso Geothermal Field ◽  
The One ◽  
Earthquake Sequences

Abstract Two recent earthquake sequences near the Coso geothermal field show clear evidence of faulting along conjugate planes. We present results from analyzing an earthquake sequence occurring in 1998 and compare it with a similar sequence that occurred in 1996. The two sequences followed mainshocks that occurred on 27 November 1996 and 6 March 1998. Both mainshocks ruptured approximately colocated regions of the same fault system. Following a comparison with the background seismicity of the Coso region, we have detected evidence of stress loading within the geothermal field that appears to be in response to the 1998 earthquakes. The ML = 5.2 mainshock in the 1998 sequence occurred at 5:47 a.m. UTC and was located approximately 45 km north of the town of Ridgecrest in the Coso range. The mainshock of the 1996 sequence had an ML magnitude of 5.3. There have been no observable surface ruptures associated with either of these sequences. Though the mainshocks for both sequences were located about 900 m apart and have nearly the same local magnitudes, the sequences differ in both their temporal and spatial characteristics. An analysis of the fault-plane solutions of the mainshocks and the aftershock locations suggests that the two sequences ruptured fault planes that are perpendicular to one another. We observe a much faster temporal decay of the 1998 sequence compared to the one in 1996; moreover, while the 1996 sequence was not followed by any sizeable (i.e., ML > 4.0) aftershocks, the 1998 sequence had four such events. From an estimate of the tectonic stressing rate on the fault that produced the 1998 sequence, we infer a repeat cycle of 135 years for an earthquake of comparable magnitude at Coso.

Earthquakes Induced by Wastewater Injection, Part I: Model Development and Hindcasting

2020 ◽  
Author(s):  
Iason Grigoratos ◽  
Ellen Rathje ◽  
Paolo Bazzurro ◽  
Alexandros Savvaidis
Keyword(s):  
Time Lag ◽  
Model Development ◽  
Time History ◽  
Companion Paper ◽  
Rate Dependency ◽  
Seismicity Rate ◽  
Index Model ◽  
Seismicity Rates ◽  
Central United States ◽  
Spatial Calibration

ABSTRACT In the past decade, several parts of central United States, including Oklahoma, have experienced unprecedented seismicity rates, following an increase in the volumes of wastewater fluids that are being disposed underground. In this article, we present a semi-empirical model to hindcast the observed seismicity given the injection time history. Our proposed recurrence model is a modified version of the Gutenberg–Richter relation, building upon the seismogenic index model, which predicts a linear relationship between the number of induced events and the injected volume. Our methodology accounts for the effects of spatiotemporal pore-pressure diffusion, the stressing-rate dependency of the time lag between injection and seismicity rate changes, and the rapid cessation of seismicity upon unloading. We also introduced a novel multiscale regression, which enabled us to produce grid-independent results of increased spatial resolution. Although the model is generic to be applicable in any region and has essentially only two free parameters for spatial calibration, it matches the earthquake time history of Oklahoma well across various scales, for both increasing and decreasing injection rates. In the companion paper (Grigoratos, Rathje, et al., 2020), we employ the model to distinguish the disposal-induced seismicity from the expected tectonic seismicity and test its forecasting potential.

Risk from Oklahoma’s Induced Earthquakes: The Cost of Declustering

2020 ◽  
Author(s):  
Jeremy Maurer ◽  
Deborah Kane ◽  
Marleen Nyst ◽  
Jessica Velasquez
Keyword(s):  
Financial Risk ◽  
B Value ◽  
Earthquake Risk ◽  
Eastern United States ◽  
Induced Earthquakes ◽  
Magnitude Distribution ◽  
Seismicity Rate ◽  
Seismicity Rates ◽  
Tectonic Earthquakes ◽  
Frequency Magnitude

ABSTRACT The U.S. Geological Survey (USGS) has for each year 2016–2018 released a one-year seismic hazard map for the central and eastern United States (CEUS) to address the problem of induced and triggered seismicity (ITS) in the region. ITS in areas with historically low rates of earthquakes provides both challenges and opportunities to learn about crustal conditions, but few scientific studies have considered the financial risk implications of damage caused by ITS. We directly address this issue by modeling earthquake risk in the CEUS using the 1 yr hazard model from the USGS and the RiskLink software package developed by Risk Management Solutions, Inc. We explore the sensitivity of risk to declustering and b-value, and consider whether declustering methods developed for tectonic earthquakes are suitable for ITS. In particular, the Gardner and Knopoff (1974) declustering algorithm has been used in every USGS hazard forecast, including the recent 1 yr forecasts, but leads to the counterintuitive result that earthquake risk in Oklahoma is at its highest level in 2018, even though there were one-fifth as many earthquakes as occurred in 2016. Our analysis shows that this is a result of (1) the peculiar characteristics of the declustering algorithm with space-varying and time-varying seismicity rates, (2) the fact that the frequency–magnitude distribution of earthquakes in Oklahoma is not well described by a single b-value, and (3) at later times, seismicity is more spatially diffuse and seismicity rate increases are closer to more populated areas. ITS in Oklahoma may include a combination of swarm-like events with tectonic-style events, which have different frequency–magnitude and aftershock distributions. New algorithms for hazard estimation need to be developed to account for these unique characteristics of ITS.

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