scholarly journals Slow-to-Fast Deformation in Mafic Fault Rocks on an Active Low-Angle Normal Fault, Woodlark Rift, SE Papua New Guinea

2020 ◽  
Author(s):  
Marcel Mizera ◽  
Timothy Little ◽  
Carolyn Boulton ◽  
David John Prior ◽  
Emma Jane Watson ◽  
...  
Keyword(s):  
Papua New Guinea ◽  
Normal Fault ◽  
New Guinea ◽  
Fault Rocks

Mixed-mode Slip Behavior and Strength Evolution of an Actively Exhuming Low-Angle Normal Fault, Woodlark Rift, SE Papua New Guinea

2020 ◽  
Author(s):  
Marcel Mizera ◽  
Timothy Little ◽  
Carolyn Boulton ◽  
James Biemiller ◽  
David Prior
Keyword(s):  
Papua New Guinea ◽  
Fault Zone ◽  
Normal Fault ◽  
New Guinea ◽  
Grain Boundary Sliding ◽  
Fault Scarp ◽  
Geochemical Data ◽  
Fault Rock ◽  
Fault Rocks ◽  
Crystallographic Preferred Orientation

<p>Rapid dip-slip (11.7±3.5 mm/yr) on the active Mai'iu low-angle normal fault in SE Papua New Guinea enabled the preservation of early formed microstructures in mid to shallow crustal rocks. The corrugated, convex-upward shaped fault scarp dips as low as 16°–20° near its trace close to sea level and forms a continuous landscape surface traceable for at least 28 km in the NNE slip-direction. Structurally, offset on the Mai'iu fault has formed a metamorphic core complex and has exhumed a metabasaltic footwall during 30–45 km of dip slip on a rolling-hinge style detachment fault. The exhumed crustal section records the spatiotemporal evolution of fault rock deformation mechanisms and the differential stresses that drive slip on this active low-angle normal fault.</p><p>The Mai'iu fault exposes a <3 m-thick fault core consisting of gouges and cataclasites. These deformed units overprint a structurally underlying carapace of metabasaltic mylonites that are locally >60 m-thick. Detailed microstructural, textural and geochemical data combined with chlorite-based geothermometry of these fault rocks reveal a variety of deformation processes operating within the Mai'iu fault zone. A strong crystallographic preferred orientation of non-plastically deformed actinolite in a pre-existing, fine-grained (6–33 µm) mafic assemblage indicates that mylonitic deformation was controlled by diffusion-accommodated grain-boundary sliding together with syn-tectonic chlorite precipitation at >270–370°C. At shallower crustal levels on the fault (T≈150–270°C), fluid-assisted mass transfer and metasomatic reactions created a foliated cataclasite fabric during inferred periods of aseismic creep. Pseudotachylites and ultracataclasites mutually cross-cut both the foliations and one another, recording repeated episodes of seismic slip. In these fault rocks, paleopiezometry based on calcite twinning yields peak differential stresses of ~140–185 MPa at inferred depths of 8–12 km. These differential stresses were high enough to drive continued slip on a ~35° dipping segment of the Mai'iu fault, and to cause new brittle yielding of strong mafic rocks in the exhuming footwall of that fault. In the uppermost crust (<8 km; T<150°C), where the Mai'iu fault dips shallowly and is most severely misoriented for slip, actively deforming fault rocks are clay-rich gouges containing abundant saponite, a frictionally weak mineral (µ<0.28).</p><p>In summary, these results combined with fault dislocation models of GPS velocities from campaign stations in this region suggest a combination of brittle frictional and viscous flow processes within the Mai'iu fault zone. Gouges of the Mai'iu fault have been strongly altered by fluids and are frictionally weak near the surface, where the fault is most strongly misoriented. At greater depths (8–12 km) the fault is stronger and slips both by aseismic creep and episodic earthquakes (a mixture of fast and slow slip) in response to locally high differential stresses.</p>

Mixed-Mode Seismic Slip and Aseismic Creep on a Highly Active Low-Angle Normal Fault System in Papua New Guinea

2020 ◽  
Author(s):  
James Biemiller ◽  
Laura Wallace ◽  
Luc Lavier
Keyword(s):  
Papua New Guinea ◽  
Normal Fault ◽  
New Guinea ◽  
Fault System ◽  
Normal Faults ◽  
Fault Mechanics ◽  
Fault Rocks ◽  
Near Surface ◽  
Geological Evidence ◽  
Seismic Slip

<p>Whether low-angle normal faults (LANFs; dip < 30°) slip in large earthquakes or creep aseismically is a longstanding problem in fault mechanics. Although abundant in the geologic record, active examples of these enigmatic ‘misoriented’ structures are rare and extension rates across them are typically less than a few mm/yr. As such, geodetic and seismological observations of LANFs are sparse and can be difficult to interpret in terms of earthquake cycles. With a long-term slip rate of ~1 cm/yr, the Mai’iu fault in Papua New Guinea may be the world’s most active LANF and thus offers an outstanding natural laboratory to evaluate seismic vs. aseismic behavior of LANFs. Here, we use new results from a campaign GPS network to determine the degree of locking vs. aseismic creep on the Mai’iu fault and evaluate these results in the context of geological evidence for mixed seismic and aseismic slip in exhumed Mai’iu fault rocks.</p><p>We derive velocities from GPS measurements with 3-4 km station spacing above the shallowest portions of the fault, which dips 21-25° at the surface. Dislocation modeling of these velocities is consistent with 6-8 mm/yr of horizontal extension, corresponding to ~1 cm/yr dip-slip rates on a 27-35°-dipping fault. Strain rates and vertical derivatives of horizontal stress rates derived from these velocities confirm localized extension across the fault. We compare and evaluate two interseismic locking models that fit the data best: one in which the fault deforms by shallow near-surface creep updip of a deeper zone of increased interseismic coupling which soles into a steadily creeping shear zone at depth, and one in which the fault creeps steadily downdip of a shallowly locked patch. These results combined with field and microstructural evidence from the exhumed fault rocks suggest that the fault slips by a mixture of brittle frictional (seismic slip, fracturing, and cataclastic creep) and viscous (stress-driven dissolution-precipitation creep, or pressure solution) processes. Using depth-constrained mechanical properties and stress conditions inferred from exhumed fault rocks, we model the time-dependent competition between frictional slip and viscous creep to assess where and how elastic strain accumulates along the Mai’iu fault, and whether the fault is capable of hosting or nucleating earthquakes.</p>

scholarly journals Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea

2020 ◽  
Vol 21 (11) ◽  
Author(s):  
M. Mizera ◽  
T. Little ◽  
C. Boulton ◽  
D. Prior ◽  
E. Watson ◽  
...  
Keyword(s):  
Papua New Guinea ◽  
Normal Fault ◽  
New Guinea ◽  
Fault Rocks

Using paleomagnetism to test rolling hinge behaviour of an active continental low angle normal fault, Papua New Guinea

2021 ◽  
Vol 558 ◽  
pp. 116745
Author(s):  
Emma J. Watson ◽  
Gillian M. Turner ◽  
Timothy A. Little ◽  
Elisa J. Piispa
Keyword(s):  
Papua New Guinea ◽  
Normal Fault ◽  
New Guinea

scholarly journals Mechanical Implications of Creep and Partial Coupling on the World's Fastest Slipping Low‐Angle Normal Fault in Southeastern Papua New Guinea

2020 ◽  
Vol 125 (10) ◽  
Author(s):  
James Biemiller ◽  
Carolyn Boulton ◽  
Laura Wallace ◽  
Susan Ellis ◽  
Timothy Little ◽  
...  
Keyword(s):  
Papua New Guinea ◽  
Normal Fault ◽  
New Guinea ◽  
Partial Coupling

Using Syntectonic Calcite Veins to Reconstruct the Strength Evolution of an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea

2021 ◽  
Author(s):  
Marcel Mizera ◽  
Tim Little ◽  
Carolyn Boulton ◽  
Yaron Katzir ◽  
Nivedita Thiagarajan ◽  
...  
Keyword(s):  
Papua New Guinea ◽  
Normal Fault ◽  
New Guinea ◽  
Calcite Veins ◽  
Strength Evolution

Structural and Geomorphic Evidence for Rolling‐Hinge Style Deformation of an Active Continental Low‐Angle Normal Fault, SE Papua New Guinea

Tectonics ◽  
2019 ◽  
Vol 38 (5) ◽  
pp. 1556-1583 ◽  
Author(s):  
M. Mizera ◽  
T. A. Little ◽  
J. Biemiller ◽  
S. Ellis ◽  
S. Webber ◽  
...  
Keyword(s):  
Papua New Guinea ◽  
Normal Fault ◽  
New Guinea

scholarly journals Along-Strike Rapid Structural and Geomorphic Transition From Transpression to Strike-Slip to Transtension Related to Active Microplate Rotation, Papua New Guinea

2021 ◽  
Vol 9 ◽  
Author(s):  
Lei Sun ◽  
Paul Mann
Keyword(s):  
Papua New Guinea ◽  
Structural Variation ◽  
Plate Boundary ◽  
Normal Fault ◽  
New Guinea ◽  
Strike Slip ◽  
Gps Geodesy ◽  
Central Segment ◽  
Abrupt Changes ◽  
Longitudinal Profiles

The area of southeastern Papua New Guinea includes three active microplates – the Trobriand, Woodlark, and Solomon Sea plates – that are being deformed by regional convergence between the much larger Pacific and Australian Plates. The landward extent of the plate boundary between the Trobriand and Australian Plates corresponds to the Owen-Stanley Fault Zone (OSFZ), an onland and continuous 510 km-long left-lateral strike-slip fault that forms a linear, intermontane valley within the elongate Owen-Stanley Range (OSR) and continues as a 250 km-long low-angle normal fault along the margins of Goodenough and Woodlark basins. GPS geodesy reveals that the Trobriand microplate has undergone rapid counter-clockwise rotation since the Late Miocene (8.4 Ma) and that this rotation about a nearby pole of rotation predicts transpressional deformation along the 250 km-long northwestern segment of the OSFZ, strike-slip motion along a 100 km-long central segment, and transtension along the 270 km-long ESE-trending southeastern segment of OSFZ. In order to illustrate the along-strike variations in neotectonic uplift resulting from the changing structure of the OSFZ, we delineated 3903 river segments in the northeastern side of the OSR drainage divide and derived river longitudinal profiles along each river segment. Normalized steepness indices (ksn) and knickpoint clusters are the highest and most concentrated, respectively, for the northwestern transpressional segment of the OSR, moderately high and concentrated along the southeastern segment of the OSR, and the lowest and least concentrated along the central strike-slip segment. These geomorphological indices indicate that most of the plate boundary uplift occurs along the transpressional and transtensional segments that are connected by the central strike-slip zone. Within this overall pattern of structural variation, abrupt changes in the azimuth of the OSFZ create more localized anomalies in the geomorphological indices.

Evolution of a rapidly slipping, active low-angle normal fault, Suckling-Dayman metamorphic core complex, SE Papua New Guinea

2019 ◽  
Vol 131 (7-8) ◽  
pp. 1333-1363 ◽  
Author(s):  
Timothy A. Little ◽  
S.M. Webber ◽  
M. Mizera ◽  
C. Boulton ◽  
J. Oesterle ◽  
...  
Keyword(s):  
Papua New Guinea ◽  
Normal Fault ◽  
New Guinea ◽  
Metamorphic Core Complex ◽  
Core Complex ◽  
Metamorphic Core

scholarly journals Mechanical Implications of Creep and Partial Coupling on the World's Fastest Slipping Low-angle Normal Fault in Southeastern Papua New Guinea

2020 ◽  
Author(s):  
James B. Biemiller ◽  
Carolyn Boulton ◽  
Laura Wallace ◽  
Susan Ellis ◽  
Timothy Little ◽  
...  
Keyword(s):  
Papua New Guinea ◽  
Normal Fault ◽  
New Guinea ◽  
Partial Coupling
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