Groundwater extraction-induced seismicity around Delhi region, India

AbstractThe non-tectonic deformation, either of natural or anthropogenic origin, may influence the earthquake occurrence process and seismicity rate along the plate-boundary or ‘stable’ plate-interiors domains. The low magnitude but moderate seismicity rate of Delhi region on the stable plate-interiors domains of India, exhibits significant variation both in short-term at annual seasonal scale and in long-term at decadal scale. It correlates with the anthropogenic groundwater pumping for the extensive irrigation, urban activities, and seasonally controlled hydrological loading cycle of Indo-Ganga Basin hosted freshwater aquifers. Our coupled hydro-mechanical simulation and poro-mechanical analysis of basement fault stability suggest that the combined aquifer contraction and basement rock expansion act together to modulate the effective stress regime and anthropogenic seismicity on the basement faults in Delhi region.

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Neotectonics of Graciosa island (Azores): a contribution to seismic hazard assessment of a volcanic area in a complex geodynamic setting

Annals of Geophysics ◽

10.4401/ag-6222 ◽

2014 ◽

Vol 56 (6) ◽

Author(s):

Ana Hipólito ◽

José Madeira ◽

Rita Carmo ◽

João Luís Gaspar

Keyword(s):

Stress Field ◽

Seismic Hazard ◽

Plate Boundary ◽

Seismic Hazard Assessment ◽

Middle Pleistocene ◽

Geodynamic Setting ◽

Tectonic Deformation ◽

Volcanic Area ◽

Stress Regime ◽

Regional Stress

Graciosa is a mid-Pleistocene to Holocene volcanic island that lies in a complex plate boundary between the North American, Eurasian, and Nubian plates. Large fault scarps displace the oldest (Middle Pleistocene) volcanic units, but in the younger areas recent volcanism (Holocene to Upper Pleistocene) conceals the surface expression of faulting, limiting neotectonic observations. The large displacement accumulated by the older volcanic units when compared with the younger formations suggests a variability of deformation rates and the possibility of alternating periods of higher and lower tectonic deformation rates; this would increase the recurrence interval of surface rupturing earthquakes. Nevertheless, in historical times a few destructive earthquakes affected the island attesting for its seismic hazard. Regarding the structural data, two main fault systems, incompatible with a single stress field, were identified at Graciosa Island. Thus, it is proposed that the region is affected by two alternating stress fields. The stress field #1 corresponds to the regional stress regime proposed by several authors for the interplate shear zone that constitutes the Azorean segment of the Eurasia-Nubia plate boundary. It is suggested that the stress field #2 will act when the area under the influence of the regional stress field #1 narrows as a result of variations in the differential spreading rates north and south of Azores. The islands closer to the edge of the sheared region will temporarily come under the influence of a different (external) stress field (stress field #2). Such data support the concept that, in the Azores, the Eurasia-Nubia boundary corresponds to a complex and wide deformation zone, variable in time.

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New seismological data from the Calabrian arc reveal arc-orthogonal extension across the subduction zone

Scientific Reports ◽

10.1038/s41598-020-79719-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Tiziana Sgroi ◽

Alina Polonia ◽

Graziella Barberi ◽

Andrea Billi ◽

Luca Gasperini

Keyword(s):

Lateral Displacement ◽

Tectonic Setting ◽

Plate Boundary ◽

Velocity Model ◽

Tectonic Deformation ◽

Accretionary Wedge ◽

Tectonic Structures ◽

Plate Convergence ◽

Seismogenic Layer ◽

Regional Tectonic

AbstractThe Calabrian Arc subduction-rollback system along the convergent Africa/Eurasia plate boundary is among the most active geological structures in the Mediterranean Sea. However, its seismogenic behaviour is largely unknown, mostly due to the lack of seismological observations. We studied low-to-moderate magnitude earthquakes recorded by the seismic network onshore, integrated by data from a seafloor observatory (NEMO-SN1), to compute a lithospheric velocity model for the western Ionian Sea, and relocate seismic events along major tectonic structures. Spatial changes in the depth distribution of earthquakes highlight a major lithospheric boundary constituted by the Ionian Fault, which separates two sectors where thickness of the seismogenic layer varies over 40 km. This regional tectonic boundary represents the eastern limit of a domain characterized by thinner lithosphere, arc-orthogonal extension, and transtensional tectonic deformation. Occurrence of a few thrust-type earthquakes in the accretionary wedge may suggest a locked subduction interface in a complex tectonic setting, which involves the interplay between arc-orthogonal extension and plate convergence. We finally note that distribution of earthquakes and associated extensional deformation in the Messina Straits region could be explained by right-lateral displacement along the Ionian Fault. This observation could shed new light on proposed mechanisms for the 1908 Messina earthquake.

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

Bulletin of the Seismological Society of America ◽

10.1785/bssa0730010219 ◽

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.

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Delineating Deep Basement Faults in Eastern Dharwar Craton through Systematic Methods of Geophysics and Remote Sensing vis-à-vis the Concerns of Moderate Seismicity

Journal of Geography & Natural Disasters ◽

10.4172/2167-0587.1000184 ◽

2017 ◽

Vol 07 (01) ◽

Cited By ~ 1

Author(s):

Ayaz Mohmood Dar ◽

Lasitha S ◽

Kaiser Bukhari ◽

Maqbool Yousuf

Keyword(s):

Remote Sensing ◽

Dharwar Craton ◽

Eastern Dharwar Craton ◽

Basement Faults ◽

Moderate Seismicity

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The Gujarat, West India, earthquake (Jan 26th 2001). A geodynamic event in an intraplate compressional regime?

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.17234 ◽

2001 ◽

Vol 34 (4) ◽

pp. 1405

Author(s):

Γ. Δ. ΔΑΝΑΜΟΣ ◽

Ε. Λ. ΛΕΚΚΑΣ ◽

Σ. Γ. ΛΟΖΙΟΣ

Keyword(s):

Large Scale ◽

Lateral Displacement ◽

Indian Subcontinent ◽

Plate Boundary ◽

Horizontal Displacement ◽

Vertical Displacement ◽

Lateral Spreading ◽

Tectonic Deformation ◽

Epicentral Area ◽

Surface Ruptures

The Jan. 26, 2001, Ms=7.7 earthquake occurred in Gujarat region of W. India, which lies 200-400 Km away from the active plate boundary zone, between the Indian subcontinent and the Asian plate, along the India-Pakistan border and the Himalayan belt. An Ms=7.7±0.2 earthquake also occurred in the same region in 1819. A zone of co-seismic E-W surface ruptures, 30-40 Km long and 15-20 Km wide, observed near the epicentral area and seems to be associated with pre-existing reverse faults and thrust folds, which were partially reactivated during the recent earthquake. Except the reverse vertical displacement a significant right lateral displacement was also observed along these E-W surface ruptures. This Ms=7.7 seismic event has been also accompanied by a large scale flexural-slip folding, as the absence of significant co-seismic fault displacement and fault scarp shows. This type of compressional tectonic deformation is also confirmed by the focal mechanism of the earthquake and the seismo-tectonic "history" of the area. The NW-SE open cracks, also observed along the same zone, are associated with the right lateral horizontal displacement of the reactivated fault (or branch faults) and the development of local extensional stress field in the huge anticlinic hinges of the co-seismic flexural-slip folds. A large number of ground ruptures, failures and open cracks are also associated with extensive sand boils, liquefaction phenomena and lateral spreading.

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Seismotectonics of the northern Longitudinal Valley, Taiwan, inferred from aftershock sequences of 2018 Mw6.4 and 2019 Mw6.2 Hualien earthquakes

10.5194/egusphere-egu2020-21398 ◽

2020 ◽

Author(s):

Wei-Fang Sun ◽

Hao Kuo-Chen ◽

Zhuo-Kang Guan ◽

Wen-Yen Chang

Keyword(s):

Main Shock ◽

Surface Deformation ◽

Plate Boundary ◽

Aftershock Sequence ◽

Tectonic Structures ◽

Seismicity Rate ◽

Transitional Area ◽

Main Shocks ◽

Aftershock Sequences ◽

Seismic Networks

In the Hualien area, two Mw6.4 and Mw6.2 earthquakes, 20 km apart, occurred in February 2018 and April 2019 respectively. The former to the northeast, located offshore to &#8203;&#8203;the Liwu river, triggered several earthquake clusters along the Milun fault and southward to the Longitudinal Valley, the suture of the Eurasian and the Philippine Sea plates; the latter to the southwest, located in the Central Range, also triggered several seismic swarms in the Central Range, &#160;along the Liwu river to the northeast and at Ji'an to the southeast. Except for the Milun fault, neither GPS nor InSAR observations detects significant surface deformation after the occurrence of these two main shocks, indicating that the earthquake ruptures mainly developed within the crust. Therefore, seismic observation becomes an efficient tool for revealing the seismotectonics of the two earthquake sequences. For monitoring the aftershock sequences, two days after the main shocks, we deployed two geophone arrays, 70 Z-component RefTek 125A TEXANs for two weeks in 2018 and 47 three-component Fairfield Nodal Z-Lands for one month in 2019, with 1-5 km station spacing around the Hualien City. These earthquake swarms were well recorded and analyzed through the dense seismic networks. The numbers of aftershock sequences manually identified are two-fold more than that issued by the Central Weather Bureau, Taiwan. The seismicity of the 2018 aftershock sequence, to depths of between 5-15 km, was significantly reduced within 10 days after the main shock. however, the seismicity of the 2019 aftershock sequence, to depths of between 2-50 km, was still above background seismicity rate 30 days after the main shock. The spatial distribution of the 2018 aftershock sequence could be related to a fault zone of the plate boundary, but that of the 2019 and the relocated 1986 aftershock sequences show a conjugate thrust fault pair beneath the eastern Central Range. Our results clearly depict several local tectonic structures that have not been observed at the northern tip of the Longitudinal Valley, not only a suture but also a transitional area from collision to subduction.

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Interseismic stress field variations in Hjalli-Ölfus, SW Iceland

10.5194/egusphere-egu2020-8521 ◽

2020 ◽

Author(s):

Ingi Th. Bjarnason ◽

Revathy M. Parameswaran ◽

Bergthóra S. Thorbjarnardóttir

Keyword(s):

Plate Boundary ◽

Strike Slip ◽

Seismogenic Zone ◽

Plate Boundaries ◽

Central Volcano ◽

Seismic Zone ◽

Stress Regime ◽

Mid Atlantic Ridge ◽

Spatio Temporal ◽

Earthquake Sequences

Western South Iceland Seismic Zone (SISZ) plate boundary lies adjacent to the Hengill central volcano. The sinistral SISZ connects the two arms of the divergent Mid-Atlantic Ridge (MAR) plate boundaries (Western and Eastern Volcanic Zones; WVZ, EVZ), while Hengill is a part of the WVZ. Seismicity in western SISZ, also known as the Hjalli-&#214;lfus region, closely interacts with the seismicity and magmatism in Hengill. For instance, the&#160; 4 June 1998 Mw 5.4 Hengill earthquake witnessed aftershocks that extended south to meet the Hjalli-&#214;lfus segment. This segment then hosted the Mw 5.1 Hjalli-&#214;lfus earthquake that occurred on 13 November 1998; elucidating the Hengill-&#214;lfus interaction. Relative relocations of earthquakes from July 1991 to December 1999 in Hjalli-&#214;lfus indicate that the seismogenic zone is predominant at 4-8 km depth, with 80% of the events occuring along an ~ENE-WSW trending seismic zone with lateral extension of ~12 km. The remaining occur along N-S faults, much like the observed norm of dextral faulting along the rest of the SISZ (e.g., 17 June 2000, 29 May 2008 earthquakes; &#193;rnadottir et al., 2001; Brandsdottir et al., 2010). These relocated earthquake sequences were used to perform stress inversions within specified spatio-temporal grids. The results show that from 1994 to 1997, the western part of the Hjalli-&#214;lfus region exhibits an oblique normal stress regime, while the eastern part remains consistently strike-slip in nature. From mid-1997 to June 1998 western Hjalli-&#214;lfus shifts from an oblique normal to a strike-slip stress regime, while the eastern part maintains the strike-slip character of the SISZ. However, two months after the 4 June 1998 Hengill earthquake, the western part shifts back to an oblique normal regime, which loses a part of its normal-faulting tendency after the 13 November 1998 Hjalli-&#214;lfus earthquake. This variation in stress fields between two significant events on conjugately oriented prodominantly strike-slip faults is a clear example of these features influencing one another between seismic episodes.&#160;

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Geomorphic expression and slip rate of the Fairweather fault, southeast Alaska, and evidence for predecessors of the 1958 rupture

Geosphere ◽

10.1130/ges02299.1 ◽

2021 ◽

Author(s):

Robert C. Witter ◽

Adrian M. Bender ◽

Katherine M. Scharer ◽

Christopher B. DuRoss ◽

Peter J. Haeussler ◽

...

Keyword(s):

Active Faults ◽

Plate Boundary ◽

Slip Rate ◽

Strike Slip ◽

Tectonic Deformation ◽

Plate Boundaries ◽

Slip Rates ◽

Southeast Alaska ◽

The Past ◽

Show Evidence

Active traces of the southern Fairweather fault were revealed by light detection and ranging (lidar) and show evidence for transpressional deformation between North America and the Yakutat block in southeast Alaska. We map the Holocene geomorphic expression of tectonic deformation along the southern 30 km of the Fairweather fault, which ruptured in the 1958 moment magnitude 7.8 earthquake. Digital maps of surficial geology, geomorphology, and active faults illustrate both strike-slip and dip-slip deformation styles within a 10°–30° double restraining bend where the southern Fairweather fault steps offshore to the Queen Charlotte fault. We measure offset landforms along the fault and calibrate legacy 14C data to reassess the rate of Holocene strike-slip motion (≥49 mm/yr), which corroborates published estimates that place most of the plate boundary motion on the Fairweather fault. Our slip-rate estimates allow a component of oblique-reverse motion to be accommodated by contractional structures west of the Fairweather fault consistent with geodetic block models. Stratigraphic and structural relations in hand-dug excavations across two active fault strands provide an incomplete paleoseismic record including evidence for up to six surface ruptures in the past 5600 years, and at least two to four events in the past 810 years. The incomplete record suggests an earthquake recurrence interval of ≥270 years—much longer than intervals <100 years implied by published slip rates and expected earthquake displacements. Our paleoseismic observations and map of active traces of the southern Fairweather fault illustrate the complexity of transpressional deformation and seismic potential along one of Earth’s fastest strike-slip plate boundaries.

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Seismicity clusters in Central Chile: investigating the role of repeating earthquakes and swarms in a subduction region

Geophysical Journal International ◽

10.1093/gji/ggaa562 ◽

2020 ◽

Vol 224 (3) ◽

pp. 2028-2043

Author(s):

Carla Valenzuela-Malebrán ◽

Simone Cesca ◽

Sergio Ruiz ◽

Luigi Passarelli ◽

Felipe Leyton ◽

...

Keyword(s):

Subduction Zone ◽

Slip Rate ◽

Central Chile ◽

Moment Tensors ◽

Seismicity Rate ◽

Megathrust Earthquakes ◽

Omori Law ◽

Aftershock Sequences ◽

Moderate Seismicity ◽

Maule Earthquake

SUMMARY Seismicity along subduction interfaces is usually dominated by large main-shock–aftershock sequences indicative of a continuum distribution of highly coupled large asperities. In the past decades, however, the increased resolution of seismic catalogues at some subduction zone seems to indicate instead a more complex rheological segmentation of the interface. Large and megathrust earthquake ruptures seem interspersed among regions of low seismic coupling and less stress buildup. In this weaker zone, the strain is primarily released via a combination of moderate-size swarm-like seismicity and aseismic slip. Along the Chilean subduction zone, the densification of the seismic network allowed for the identification of localized seismic clusters, some of them appearing in the form of swarms before megathrust earthquakes. The origin and driving processes of this seismic activity have not yet been identified. In this study, we follow a systematic approach to characterize the seismicity at two persistent clusters in Central Chile, one located offshore Navidad and one inland, at ∼40 km depth beneath Vichuquén, which occurred throughout ∼20 yr. We investigated these clusters, by deriving high-resolution hypocentral locations and moment tensors and performing a detailed analysis of spatio-temporal patterns, magnitude and interevent time distributions of the clustered earthquakes. Both clusters are characterized by weak to moderate seismicity (below Mw 6) and stand out as clear seismicity rate and Benioff strain anomalies. At the Navidad cluster, seismicity occurs in the form of swarms, with a characteristic duration of 2–7 d and location and thrust mechanisms compatible with activity on the slab interface. Conversely, we find at Vichuquén activity dominated by thrust earthquakes occurring as repeaters on the slab interface, with a slip rate of approximately ∼5.0 cm yr−1. We attribute these clusters to local features of the subducting plate: the Navidad swarms are likely driven by repeated high pore pressure transients along a pre-fractured patch of the slab, while the seismicity at the Vichuquén cluster is interpreted as the result of a subducting seamount. Both clusters have been active before and after the Mw 8.8 Maule earthquake and persisted afterwards with the seismicity decay following the Omori law. These interactions are especially evident for the Vichuquén cluster, where the seismicity rate increased considerably after the Maule earthquake and continues to be an area of clearly elevated seismicity rate compared to its surroundings.

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Feedbacks between internal fluvial drainage and high-plateau tectonic growth. A mechanistic perspective.

10.5194/egusphere-egu2020-17481 ◽

2020 ◽

Author(s):

Daniel Garcia-Castellanos ◽

Weiming Liu ◽

Zhongping Lai ◽

Ivone Jiménez-Munt ◽

Lucía Struth ◽

...

Keyword(s):

Numerical Modeling ◽

Numerical Models ◽

Plate Boundary ◽

Active Regions ◽

Sedimentary Basins ◽

Tectonic Deformation ◽

The Tibetan Plateau ◽

Internal Drainage ◽

High Plateau ◽

River Incision

High-plateaus are relatively flat areas at high elevations. The stream-power river-incision law predicts that surface water incises the landscape proportionally to local river slope, and therefore the margins of high-plateaus are prone to a river erosion that should terminate the low relief of the highlands that characterizes the plateau. This means that long-lived high-plateaus need an additional mechanism to compete with river incision.In absence of tectonic deformation, river networks propagate into the plateau via a retrogressive wave of river incision. A well-constrained non-tectonic scenario is provided by the Neogene Duero and Ebro sedimentary basins in N Iberia, where ongoing incision rates presently range from .02 (Duero) to .5 m/kyr (Ebro) and have propagated upstream at similar rates of up to 0.2 km/kyr, based on cosmogenic dating studies combined with numerical modeling. These rates started with the transition from internal (endorheic) to external (exorheic) drainage of both basins sometime between 8 and 12 million years ago. Interestingly, while the pre-exorheic Ebro Basin sedimentary plateau has been mostly obliterated by erosion, the Duero Basin still preserves large areas of low relief, in spite of the very similar geological setting. The causes will be discussed using landscape evolution numerical modeling.In contrast, tectonically active regions can counteract river incision and preserve high plateaus by longer time periods. Recent studies based on sedimentary stratigraphy of endorheic basins suggest that large areas of the Tibetan high plateau remain internally drained since ca 35 Ma. In the Altiplano/Puna plateau region internal drainage dates to ~15 Ma and the majority of the topographic uplift has taken place after 10 Ma. Computer models have shown that tectonic deformation is sensitive to internal drainage, because endorheism implies a nearly perfect sediment trap that effectively reduces the output of orogenic erosion to zero. The cancellation of orogen-scale erosion can severely modify tectonic deformation patterns, increase topography and propagate deformation further into the undeformed forelands of the orogenic system. Symmetrically, internal drainage is also promoted by the orographic rain shadow due to the growth of topography in the early stages of tectonism.Numerical models coupling the aforementioned mechanisms have shown that, as sediment transport and accumulation within the endorheic region progresses, the propagation of deformation to areas more distal to the tectonic plate boundary can lead to a lower&#8208;relief landscape. A recent reassessment of the ages of the Tibetan plateau sedimentary record in the Lunpola Basin seems consistent with an early onset of low relief and internal drainage. Finally, as topography and crustal thickness increase, lower crust flow is facilitated by the lower viscosity implied by higher pressure, favoring a further reduction of local relief within the highlands.

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