scholarly journals The Matata Earthquake Sequence of 1977, Bay of Plenty, New Zealand

2021 ◽  
Author(s):  
◽  
Wayne Phillip Richardson
Keyword(s):  
Normal Component ◽  
Focal Depth ◽  
Heterogeneous Structure ◽  
Volcanic Front ◽  
Plate Interface ◽  
Stick Slip ◽  
Volcanic Region ◽  
The North ◽  
Shear Component ◽  
Recent Volcanism

<p>An ML. 5.4 earthquake and an associated sequence of smaller earthquakes, including foreshocks, were well recorded in 1977 by a network of 10 seismographs set for a microearthquake survey in the Bay of Plenty region, which is transitional between back-are spreading regions of the Havre Trough and the continental North Island. Upper crustal aftershock origins clustered and migrated within an area 7 km by 15 km elongated east-west. The aftershocks were relatively swarm-like, producing a b- value of 1.29 [plus or minus] 0.13, and were apparently of long sequence duration, with decay coefficient p = 0.67 [plus or minus] 0.03. A northeast-trending rupture fitted for the mainshock, originating close to where foreshocks were centred, and passing between tight concentrations of later aftershock activity to either side. Teleseismic waveforms, in addition to providing a 10.5 km estimate of focal depth, helped to constrain the solution of focal mechanism for the mainshock. The preferred solution is for mainly right-lateral slip on a northeast striking plane but with a normal component. The slip trend parallels the front of recent volcanism. Mechanisms for related events range from normal to strike slip, on parallel and intersecting planes, and are indicative of the complexity of geological structure where north-trending faults of the North Island shear belt meet with the front of recent volcanism. as well as of a prevailing traction across the volcanic front. The volcanic region is characterised by a low Poisson's ratio, suggested by the Wadati method to be v= 0.19 [plus or minus] 0.01 in contrast to v =0.27 [plus or minus] 0.01 for the greywacke region to the southeast; this difference is attributed to contrasting rock types and other conditions either side of the volcanic front. The multiplicity of earthquake sequences in the volcanic region indicates a high degree of heterogeneous structure. A low stress drop of 2.8 MPa inferred for the Matata mainshock suggests that the faulting occurs on pre-existing planes. Off-fault aftershocks occurred where the failure stress increased as a result of the mainshock rupture. A concurrent sequence of earthquakes originating near 50km depth indicated thrusting on the lithospheric plate interface underlying the North Island; thrusting on the interface apparently extends to about 70km depth, where the plates become decoupled. Oblique plate convergence and stick-slip motion on the weakly coupled interface provides the regional dextral shear component observed in the volcanic region for the Matata mainshock. An extensional component is therefore a necessary addition for the observed normal component of faulting, which predominated for the 1987 Edgecumbe mainshock. Wave mode conversions inferred for subcrustal earthquakes and the Matata sequence mainshock indicate that the Moho shallows from 28.5 km to 22 km northwestwards across the volcanic front, suggesting that new crust in the Bay of Plenty region is being created over a wide region rather than by active rifting along a sharp margin.</p>

scholarly journals The Matata Earthquake Sequence of 1977, Bay of Plenty, New Zealand

2021 ◽  
Author(s):  
◽  
Wayne Phillip Richardson
Keyword(s):  
Normal Component ◽  
Focal Depth ◽  
Heterogeneous Structure ◽  
Volcanic Front ◽  
Plate Interface ◽  
Stick Slip ◽  
Volcanic Region ◽  
The North ◽  
Shear Component ◽  
Recent Volcanism

<p>An ML. 5.4 earthquake and an associated sequence of smaller earthquakes, including foreshocks, were well recorded in 1977 by a network of 10 seismographs set for a microearthquake survey in the Bay of Plenty region, which is transitional between back-are spreading regions of the Havre Trough and the continental North Island. Upper crustal aftershock origins clustered and migrated within an area 7 km by 15 km elongated east-west. The aftershocks were relatively swarm-like, producing a b- value of 1.29 [plus or minus] 0.13, and were apparently of long sequence duration, with decay coefficient p = 0.67 [plus or minus] 0.03. A northeast-trending rupture fitted for the mainshock, originating close to where foreshocks were centred, and passing between tight concentrations of later aftershock activity to either side. Teleseismic waveforms, in addition to providing a 10.5 km estimate of focal depth, helped to constrain the solution of focal mechanism for the mainshock. The preferred solution is for mainly right-lateral slip on a northeast striking plane but with a normal component. The slip trend parallels the front of recent volcanism. Mechanisms for related events range from normal to strike slip, on parallel and intersecting planes, and are indicative of the complexity of geological structure where north-trending faults of the North Island shear belt meet with the front of recent volcanism. as well as of a prevailing traction across the volcanic front. The volcanic region is characterised by a low Poisson's ratio, suggested by the Wadati method to be v= 0.19 [plus or minus] 0.01 in contrast to v =0.27 [plus or minus] 0.01 for the greywacke region to the southeast; this difference is attributed to contrasting rock types and other conditions either side of the volcanic front. The multiplicity of earthquake sequences in the volcanic region indicates a high degree of heterogeneous structure. A low stress drop of 2.8 MPa inferred for the Matata mainshock suggests that the faulting occurs on pre-existing planes. Off-fault aftershocks occurred where the failure stress increased as a result of the mainshock rupture. A concurrent sequence of earthquakes originating near 50km depth indicated thrusting on the lithospheric plate interface underlying the North Island; thrusting on the interface apparently extends to about 70km depth, where the plates become decoupled. Oblique plate convergence and stick-slip motion on the weakly coupled interface provides the regional dextral shear component observed in the volcanic region for the Matata mainshock. An extensional component is therefore a necessary addition for the observed normal component of faulting, which predominated for the 1987 Edgecumbe mainshock. Wave mode conversions inferred for subcrustal earthquakes and the Matata sequence mainshock indicate that the Moho shallows from 28.5 km to 22 km northwestwards across the volcanic front, suggesting that new crust in the Bay of Plenty region is being created over a wide region rather than by active rifting along a sharp margin.</p>

Geodetic strain and the deformational history of the North Island of New Zealand during the late Cainozoic

1987 ◽  
Vol 321 (1557) ◽  
pp. 163-181 ◽  
Keyword(s):  
New Zealand ◽  
Subduction Zone ◽  
East Coast ◽  
Late Quaternary ◽  
Plate Boundary ◽  
Boundary Zone ◽  
Metamorphic Belt ◽  
Volcanic Region ◽  
The North ◽  
Plate Boundary Zone

The subduction zone under the east coast of the North Island of New Zealand comprises, from east to west, a frontal wedge, a fore-arc basin, uplifted basement forming the arc and the Central Volcanic Region. Reconstructions of the plate boundary zone for the Cainozoic from seafloor spreading data require the fore-arc basin to have rotated through 60° in the last 20 Ma which is confirmed by palaeomagnetic declination studies. Estimates of shear strain from geodetic data show that the fore-arc basin is rotating today and that it is under extension in the direction normal to the trend of the plate boundary zone. The extension is apparently achieved by normal faulting. Estimates of the amount of sediments accreted to the subduction zone exceed the volume of the frontal wedge: underplating by the excess sediments is suggested to be the cause of late Quaternary uplift of the fore-arc basin. Low-temperature—high-pressure metamorphism may therefore be occurring at depth on the east coast and high-temperature—low-pressure metamorphism is probable in the Central Volcanic Region. The North Island of New Zealand is therefore a likely setting for a paired metamorphic belt in the making.

Source Characteristics of the 2019 Mw 6.5 Ambon, Eastern Indonesia, Earthquake Inferred from Seismic and Geodetic Data

2021 ◽  
Author(s):  
Irwan Meilano ◽  
Rino Salman ◽  
Suchi Rahmadani ◽  
Qibin Shi ◽  
Susilo Susilo ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Normal Component ◽  
Slip Rate ◽  
Velocity Fields ◽  
Geodetic Data ◽  
Capital City ◽  
Strain Rate Tensor ◽  
Source Characteristics ◽  
Eastern Indonesia ◽  
The North

Abstract The 26 September 2019 Mw 6.5 Ambon earthquake has been the largest instrumentally recorded event to occur in Ambon, the capital city of Maluku Islands, eastern Indonesia, and ruptured a previously unmapped active fault. In this study, we use seismic and geodetic data to investigate the source characteristics of the event. Our results show that the rupture process was complex in both the rupture initiation and slip directions. In addition, the rupture was mostly strike-slip motion with normal component and pure reverse slip in the north of the inverted fault. Our analysis of campaign and continuous Global Positioning System (GPS) velocity fields estimates that the fault has a 4.9 [4.0, 5.5] mm/yr slip rate with an earthquake recurrence interval of 115 [102, 141] yr. In addition, a comparison of the horizontal strain-rate tensor derived from GPS velocity fields with historical earthquake data shows that Ambon Island and the nearby regions have a high strain accumulation rate correlated with the distribution of Mw≥6 earthquakes, indicating that the regions are seismically active and possibly will experience more Ambon-type earthquakes in the future.

Well-Log-Based Velocity and Density Models for the Montney Unconventional Resource Play in Northeast British Columbia, Canada, Applicable to Induced Seismicity Monitoring and Research

2020 ◽  
Author(s):  
Alireza Babaie Mahani ◽  
Dmytro Malytskyy ◽  
Ryan Visser ◽  
Mark Hayes ◽  
Michelle Gaucher ◽  
...  
Keyword(s):  
British Columbia ◽  
Hydraulic Fracturing ◽  
Cross Sections ◽  
Induced Seismicity ◽  
Focal Depth ◽  
Depth Resolution ◽  
Velocity Model ◽  
The North ◽  
Seismicity Monitoring ◽  
Unconventional Resource

Abstract We present detailed velocity and density models for the Montney unconventional resource play in northeast British Columbia, Canada. The new models are specifically essential for robust hypocenter determination in the areas undergoing multistage hydraulic-fracturing operations and for detailed analysis of induced seismicity processes in the region. For the upper 4 km of the sedimentary structure, we review hundreds of well logs and select sonic and density logs from 19 locations to build the representative models. For depths below 4 km, we extend our models using data from the southern Alberta refraction experiment (Clowes et al., 2002). We provide one set of models for the entire Montney play along with two separated sets for the southern and northern areas. Specifically, the models for the southern and northern Montney play are based on logs located in and around the Kiskatinaw Seismic Monitoring and Mitigation Area and the North Peace Ground Motion Monitoring area, respectively. To demonstrate the usefulness of our detailed velocity model, we compare the hypocenter location of earthquakes that occurred within the Montney play as determined with our model and the simple two-layered model (CN01) routinely used by Natural Resources Canada. Locations obtained by our velocity model cluster more tightly with the majority of events having root mean square residual of &lt;0.2  s compared with that of &lt;0.4  s when the CN01 model is used. Cross sections of seismicity versus depth across the area also show significant improvements in the determination of focal depths. Our model results in a reasonable median focal depth of ∼2  km for events in this area, which is consistent with the completion depths of hydraulic-fracturing operations. In comparison, most solutions determined with the CN01 model have fixed focal depths (0 km) due to the lack of depth resolution.

scholarly journals Possible Quaternary growth of a hidden anticline at the front of the Jura fold-and-thrust belt: geomorphological constraints from the Forêt de Chaux area, France

2011 ◽  
Vol 182 (4) ◽  
pp. 337-346 ◽  
Author(s):  
Stéphane Molliex ◽  
Olivier Fabbri ◽  
Vincent Bichet ◽  
Herfried Madritsch
Keyword(s):  
Focal Depth ◽  
Fault Reactivation ◽  
Thrust Belt ◽  
Alluvial Deposits ◽  
The North ◽  
Basement Faults ◽  
Fold And Thrust Belt ◽  
Median Position ◽  
Differential Uplift ◽  
River Migration

Abstract This study presents new constraints for Plio-Quaternary (post-2.4 Ma to present-day) anticline growth along the frontal zone of the Jura fold-and-thrust belt, in the Forêt de Chaux area, located 30 km SW of Besançon. The Forêt de Chaux area consists of a N080°E-elongated depression bordered by the Doubs and Loue rivers to the north and south respectively, and filled with Sundgau-type Pliocene alluvial deposits. The upper surface of the Pliocene deposits between the Loue and Doubs rivers is marked by a N065°E-trending ridge crossing the depression in a median position. A differential uplift along this ridge, post-dating the deposition of the gravels (2.4 Ma), is suggested by several geomorphological observations such as the opposite river migration on each side of the ridge as well as variations of drainage geometry and incision intensity. Geological and geophysical subsurface data indicate that the ridge roughly coincides with the axis of an anticline hidden beneath the Pliocene deposits. The observed uplift is presumably related to a post-2.4 Ma anticline growth. The fact that the azimuth of the hidden anticline axis is parallel to the strike of deep-seated Late Paleozoic basement faults and not to the local strike of the thin-skinned Jura structures indicates that the inferred post-Pliocene deformation could possibly be an expression of a recent thick-skinned deformation of the basement of the northern Alpine foreland. The focal depth (15 km) of the February 24th, 2004, Besançon earthquake supports the hypothesis of a basement fault reactivation.

Temporary seismic network on drifting ice in the North Barents Sea

2020 ◽  
Author(s):  
Andrey Jakovlev ◽  
Sergey Kovalev ◽  
Egor Shimanchuk ◽  
Evgeniy Shimanchuk ◽  
Aleksey Nubom
Keyword(s):  
New Technologies ◽  
Barents Sea ◽  
Seismic Signal ◽  
Ice Cover ◽  
The Arctic ◽  
Stick Slip ◽  
Seismic Stations ◽  
The North ◽  
Drifting Ice ◽  
Ice Floes

&lt;p&gt;Despite the strong attention to the investigations in the Arctic its advance quite slowly. The harsh climatic conditions and big expenses slow down realization of the fieldwork in high latitudes. Therefore, scientists from over the world looks for new technologies, which could optimize and reduce the costs of the fieldworks that aimed at investigation of the geological structure beneath the Arctic Ocean. From March to May 2019 scientific expedition on the Expedition Vessel &amp;#8220;Akademic Tryoshnikov&amp;#8221; operated by the Arctic and Antarctic Research Institute that belongs to Rosgidromet were conducted in the framework of the program &amp;#8220;TransArctica 2019&amp;#8221; first stage. In the framework of the seismological experiments 6 temporary seismic stations at 4 different locations were installed on a drifted ice floe in the North Barents Sea. The first aim of the experiment was to elaborate technology of installation of the seismic stations on the drifting ice floes. The second aim was to check if obtained seismological records could be used for registration of the local and remote earthquakes, which are meant to investigate the lithosphere structure in the Arctic regions, and for investigation of the processes within the ice floe.&lt;/p&gt;&lt;p&gt;The stations were installed in the April 2019 on the ice floe near the EV &amp;#8220;Akademik Tryoshnikov&amp;#8221; that were &amp;#8220;frizzed&amp;#8221; in the ice floe and drifted together with them. After analysis of the recoded data the following types of the seismic signal generated by processes in the ice were observed:&lt;/p&gt;&lt;ul&gt;&lt;li&gt;- background signal from bending-gravitational waves with periods from 1 to 30 sec. Swell waves with periods from 17 to 30 sec were observed permanently during the whole period of network operation;&lt;/li&gt; &lt;li&gt;- continuous mechanical vibrations (self-oscillations) with a period of up to 2-3 sec;&lt;/li&gt; &lt;li&gt;- stick-slip relaxation self-oscillations with a period from 0.1 s to several minutes;&lt;/li&gt; &lt;li&gt;- mechanical movements of ice due to compression or stretching of ice caused by chaotic different scales fluctuations in the drift velocity of ice floes;&lt;/li&gt; &lt;li&gt;- process of ice fracturing due to compression or stretching of ice.&lt;/li&gt; &lt;/ul&gt;&lt;p&gt;Results of monitoring of the ice cover has shown that in the most cases there are no direct correlations of processes within the ice floes and local hydrometeorological condition. During the process of ice cover fracturing an increased value of the ice horizontal movement were observed. Analysis of the seismic signal from ice events has shown that stick-slip events preceded origin of the ice fractures.&lt;/p&gt;&lt;p&gt;As a result of the initial analysis of the seismograms several signals from remote and regional earthquakes were detected. For example, an earthquake that according to the ISC bulletin occur at 08:18:23UTC on April 11, 2019 near the Japan (40.35&amp;#176;N, 143.35&amp;#176;E, 35 km depth, MS = 6.0) were detected. A local earthquake that occur approximately at 05:58UTC on April 10, 2019 at a distance of ~500 km. Due to close location of stations to each other the localization of the earthquake is impossible.&lt;/p&gt;&lt;p&gt;This work is supported by the RSCF project #18-17-00095.&lt;/p&gt;

Application of Bodner Viscoplastic Theory to Pressure-Shear Plate Impact Experiment

1990 ◽  
Vol 112 (1) ◽  
pp. 52-55 ◽  
Author(s):  
A. Gilat ◽  
J. Tsai
Keyword(s):  
Bauschinger Effect ◽  
Normal Component ◽  
Uniaxial Stress ◽  
Strain Rates ◽  
Stress Tests ◽  
Plate Impact ◽  
Calculated Profile ◽  
Shear Plate ◽  
Shear Component ◽  
Impact Experiment

An application of the unified elastic-viscoplastic constitutive theory of Bodner [5] is presented. The material parameters in the theory, which includes directional hardening, are determined from results of uniaxial stress tests at constant strain rates. The constitutive equations are then used in numerical modeling of pressure-shear plate impact experiment. The results show that the measured normal component of the wave agrees well with the calculated profile. A small discrepancy, which can be accounted for by the presence of a Bauschinger effect, exists between the theoretical and the experimental shear component of the wave profiles.

scholarly journals Ormond earthquake liquefaction reconnaissance report

1993 ◽  
Vol 26 (3) ◽  
pp. 312-328 ◽  
Author(s):  
Steven A. Christensen
Keyword(s):  
New Zealand ◽  
Focal Depth ◽  
Strong Motion ◽  
North West ◽  
The North ◽  
Peak Ground Accelerations ◽  
Seismological Observatory

On August 10 1993, at 09h 46m UT an earthquake of magnitude (ML) 6.4 occurred near Ormond, a locality to the north west of Gisbome in the North Island of New Zealand. The epicentre of the event was 38.52°S, 177.93°E, and had a focal depth of 48 km (Seismological Observatory, Institute of Geological and Nuclear Sciences Ltd.). Strong motion accelerographs at two sites on sediment in Gisborne recorded peak ground accelerations of 0.22 g at a distance of 20 km from the epicentre, while at Wairoa (80 km to the SW of the epicentre) 0.05 g was recorded, at Tolaga Bay (30 km to the NE of the epicentre) 0.09 g was measured [Pers. Comn. J. Zhou], and strong motion lasted for 5-10 s. Intensity of MMVI was observed in the Ormond area with pockets of MMVII, the later being based in particular on the presence of liquefaction.

scholarly journals Quantitative finite strain analysis of the quartz mylonites within the Three Pagodas shear zone, western Thailand

2018 ◽  
Vol 111 (2) ◽  
pp. 171-179
Author(s):  
Pitsanupong Kanjanapayont ◽  
Peekamon Ponmanee ◽  
Bernhard Grasemann ◽  
Urs Klötzli ◽  
Prayath Nantasin
Keyword(s):  
Shear Zone ◽  
Pure Shear ◽  
Strain Analysis ◽  
Strain Ratio ◽  
Kinematic Vorticity ◽  
The North ◽  
Shear Sense ◽  
Shear Component ◽  
The Mean ◽  
Vorticity Analysis

AbstractThe NW–trending Three Pagodas shear zone exposes a high–grade metamorphic complex named Thabsila gneiss in the Kanchanaburi region, western Thailand. The quartz mylonites within this strike–slip zone were selected for strain analysis. 2–dimensional strain analysis indicates that the averaged strain ratio (Rs) for the lower greenschist facies increment of XZ– plane is Rs = 1.60–1.97 by using the Fry’s method. Kinematic vorticity analysis of the quartz mylonites in the shear zone showed that the mean kinematic vorticity number of this increment is Wk = 0.75–0.99 with an average at 0.90 ±0.07. The results implied that the quartz mylonites within the Three Pagodas shear zone have a dominant simple shear component of about 72% with a small pure shear component. A sinistral shear sense is indicated by kinematic indicators from macro– to micro–scale. We conclude that the Three Pagodas shear zone deformed in the process of sinstral shear–dominated transpression, which is similar to the Mae Ping shear zone in the north.

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