scholarly journals Aftershock sequences of moderate-sized intermediate and deep earthquakes in the Tonga Subduction Zone

1997 ◽  
Vol 24 (16) ◽  
pp. 2059-2062 ◽  
Author(s):  
Douglas A. Wiens ◽  
H. J. Gilbert ◽  
B. Hicks ◽  
M. E. Wysession ◽  
P. J. Shore
Keyword(s):  
Subduction Zone ◽  
Deep Earthquakes ◽  
Aftershock Sequences ◽  
Tonga Subduction Zone

Spatial and temporal clustering of deep and shallow earthquakes in the Fiji-Tonga-Kermadec region

1967 ◽  
Vol 57 (5) ◽  
pp. 935-958 ◽  
Author(s):  
Bryan L. Isacks ◽  
Lynn R. Sykes ◽  
Jack Oliver
Keyword(s):  
Seismic Wave Propagation ◽  
Linear Feature ◽  
Space And Time ◽  
Deep Earthquakes ◽  
Shallow Earthquakes ◽  
Aftershock Sequences ◽  
Double Couple ◽  
In Series ◽  
Deep Focus ◽  
Distribution Of Stress

abstract A study of the tendency of deep and shallow earthquakes in the Fiji-Tonga-Kermadec region to cluster in space and time revealed that (a) in general, deep earthquakes do not form either aftershock sequences of swarms of the types commonly observed in series of shallow shocks throughout the world; (b) a small percentage of the deep earthquakes cluster in the form of multiplets, i.e., small numbers of events closely grouped in space and time; and (c) during the 7-year interval studied, clustering of the shallow events in the Kermadec region was markedly greater than that of shallow events in the Tongan region; clustering of shallow events in the Tongan area was, in turn, greater than that of the deep shocks in the Fijian region. The data provide new constraints for hypotheses of focal mechanisms. Most deep multiplets were doublets, and in no case were more than 12 events observed per multiplet. Resolution of the analysis was sufficient to show that, in the case of at least one multiplet, separation between events was smaller than 2 km, but that in other cases it was larger than 5 km. Separations between events in time were sometimes smaller than 2 seconds, but in no case was the relation in time and space such that a later event of a multiplet could not have been dependent upon an earlier event, i.e., the time between events was greater than that required for seismic wave propagation between the two foci. A narrow linear feature about 60 km long is defined by a spatially progressive sequence of deep multiplets that were observed during 1965. These deep multiplets are also confined to a narrow range of depths between about 625 and 660 km. This feature seems to form a portion of the lower edge of the narrow inclined zone of deep earthquakes. Patterns of first motions radiated from earthquakes in the linear feature are generally similar to one another and are in agreement with a model of the source corresponding to a double-couple or shear dislocation. Variations among the radiation patterns, although minor, are distinct and indicate some heterogeneity in the detailed distribution of stress. The data of this study do not support the hypothesis of a volumetric phase change as the mechanism of the deep-focus earthquakes. Although there is no existing hypothesis that does predict completely the results determined here, the data appear to agree best with the mechanism proposed by Orowan. A significant source of data for this work is a new network of five seismograph stations now operating in Fiji and Tonga. This study, under the U.S. Upper Mantle Program, is part of a more comprehensive investigation of deep earthquakes in the region.

scholarly journals Deep seismic structure of the Tonga subduction zone: Implications for mantle hydration, tectonic erosion, and arc magmatism

2011 ◽  
Vol 116 (B10) ◽  
Author(s):  
Eduardo Contreras-Reyes ◽  
Ingo Grevemeyer ◽  
Anthony B. Watts ◽  
Ernst R. Flueh ◽  
Christine Peirce ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Arc Magmatism ◽  
Seismic Structure ◽  
Tonga Subduction Zone ◽  
Tectonic Erosion

Deep seismicity and modes of deformation in Tonga subduction zone

Nature ◽  
1984 ◽  
Vol 307 (5951) ◽  
pp. 505-509 ◽  
Author(s):  
Domenico Giardini ◽  
John H. Woodhouse
Keyword(s):  
Subduction Zone ◽  
Tonga Subduction Zone ◽  
Deep Seismicity

scholarly journals Modeling anisotropy and plate-driven flow in the Tonga subduction zone back arc

2000 ◽  
Vol 105 (B7) ◽  
pp. 16181-16191 ◽  
Author(s):  
Karen M. Fischer ◽  
E. M. Parmentier ◽  
Alexander R. Stine ◽  
Elizabeth R. Wolf
Keyword(s):  
Subduction Zone ◽  
Tonga Subduction Zone ◽  
Back Arc

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

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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