High Potential for Splay Faulting in the Molucca Sea, Indonesia: November 2019 Mw 7.2 Earthquake and Tsunami

2021 ◽  
Author(s):  
Mohammad Heidarzadeh ◽  
Takeo Ishibe ◽  
Tomoya Harada ◽  
Danny Hilman Natawidjaja ◽  
Ignatius Ryan Pranantyo ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Seismic Events ◽  
Thrust Faults ◽  
Mean Square ◽  
Rupture Velocity ◽  
Collision Zone ◽  
Tectonic Settings ◽  
Dip Angle ◽  
Splay Faults ◽  
Error Index

Abstract Tsunami potential from high dip-angle splay faults is an understudied topic, although such splay faults can significantly amplify coastal tsunami heights as compared with ordinary thrust faults. Here, we identify a hotspot for tsunamis from splay faulting in the Molucca Sea arc–arc collision zone in eastern Indonesia, which accommodates one of the world’s most complicated tectonic settings. The November 2019 Mw 7.2 earthquake and tsunami are studied through teleseismic inversions assuming rupture velocities in the range 1.5–4.0  km/s followed by tsunami simulations. The normalized root mean square error index was applied and revealed that the best model has a rupture velocity of 2.0  km/s from the steeply dipping plane. The recent high dip-angle reverse 2019 Mw 7.2 and 2014 Mw 7.1 earthquakes combined with numerous similar seismic events may indicate that this region is prone to splay faulting. This study highlights the need for understanding tsunamis from splay faulting in other subduction zones.

Water and the Oxidation State of Subduction Zone Magmas

Science ◽  
2009 ◽  
Vol 325 (5940) ◽  
pp. 605-607 ◽  
Author(s):  
Katherine A. Kelley ◽  
Elizabeth Cottrell
Keyword(s):  
Oxygen Fugacity ◽  
Subduction Zones ◽  
Melt Inclusions ◽  
Primary Control ◽  
Edge Structure ◽  
Secular Evolution ◽  
Oxidized Iron ◽  
Tectonic Settings ◽  
Major Factors ◽  
X Ray Absorption

Mantle oxygen fugacity exerts a primary control on mass exchange between Earth’s surface and interior at subduction zones, but the major factors controlling mantle oxygen fugacity (such as volatiles and phase assemblages) and how tectonic cycles drive its secular evolution are still debated. We present integrated measurements of redox-sensitive ratios of oxidized iron to total iron (Fe3+/ΣFe), determined with Fe K-edge micro–x-ray absorption near-edge structure spectroscopy, and pre-eruptive magmatic H2O contents of a global sampling of primitive undegassed basaltic glasses and melt inclusions covering a range of plate tectonic settings. Magmatic Fe3+/ΣFe ratios increase toward subduction zones (at ridges, 0.13 to 0.17; at back arcs, 0.15 to 0.19; and at arcs, 0.18 to 0.32) and correlate linearly with H2O content and element tracers of slab-derived fluids. These observations indicate a direct link between mass transfer from the subducted plate and oxidation of the mantle wedge.

The Koyna earthquake of December 10 1967: A multiple seismic event

1971 ◽  
Vol 61 (1) ◽  
pp. 167-176 ◽  
Author(s):  
Harsh K. Gupta ◽  
B. K. Rastogi ◽  
Hari Narain
Keyword(s):  
Seismic Event ◽  
Strong Motion ◽  
Seismic Events ◽  
Field Observations ◽  
Rupture Velocity ◽  
P Waves ◽  
Seismic Arrays ◽  
Sine Curve ◽  
Curve Method ◽  
Different Origin

abstract The analysis of P waves recorded at seismological observatories and seismic arrays at teleseismic distances and strong motion seismographs located at Koyna Dam suggest the Koyna earthquake of December 10 1967 to be a complex multiple event. Six of the events could be identified, and the second and third events are located with respect to the initiation using the Gutenberg sine-curve method at distances of 6 and 17 km due south, the average rupture velocity being 3.4 km/sec. The findings are consistent with the field observations and the different origin times, epicenters and magnitudes reported for the earthquake. Seismic array records are found to be very useful in examining the multiplicity of seismic events.

scholarly journals Clinical Model to the Analysis of Synergy Pattern Changes of Back Muscles and its Relationship with the Occurrence of Fatigue

2018 ◽  
Vol 11 (1) ◽  
pp. 53-60
Author(s):  
Armin HakKak Moghaddam Torbati ◽  
Ehsan Tahami ◽  
Hamid Reza Kobravi
Keyword(s):  
Standard Deviation ◽  
Time Trial ◽  
Maximum Error ◽  
Mean Square ◽  
Clinical Model ◽  
Minimum Error ◽  
The Third ◽  
Frequency Index ◽  
Error Index ◽  
Basis Vectors

Background:Right sitting not only leads to flatness of the lumbar spine and waistline, it also causes other problems for health. The curved body pushes into lungs and breathing will be problematic.Purpose:The main purpose of this study was investigating changing procedure of lumber muscles patterns and its relationship with the occurrence of fatigue.Methods:Participants were ten male with average age 24 ± 1. Firstly, the process of fatigue during sitting was observed by mid-frequency index. For performing the necessary analysis, the 10-second window of time was used. The 15 minutes of time trial was divided into 3 sub-terms. Each sub-term was investigated separately. The sub-terms contain: The beginning of record until the 90th second, from the 90th second to the 600th second and from the 600th second to the 900th second.Results:Results showed that in each subject there were synergy patterns in both of the first and the second sub-terms. Maximum error between basis vectors in all of the subjects were 0.87 and 0.79 respectively and standard deviations were 5 and 10 respectively (Mean square error index). In some participants, there were not any synergy patterns in the third sub-term (minimum error between basis vectors in all of the subjects was 18 and standard deviation was 7.5) while in other participants, their muscles still followed special synergy patterns (maximum error between basis vectors in all of the subjects was 0.98 standard deviation was 7.5).Conclusions:Comparing the synergy patterns between different participants has determined that the synergy patterns were the same only in the first sub-term.

scholarly journals Dynamic Rupture Modeling to Investigate the Role of Fault Geometry in Jumping Rupture Between Parallel‐Trace Thrust Faults

2019 ◽  
Vol 109 (6) ◽  
pp. 2168-2186 ◽  
Author(s):  
Paul Peshette ◽  
Julian Lozos ◽  
Doug Yule ◽  
Eileen Evans
Keyword(s):  
Near Field ◽  
Stress Conditions ◽  
Parameter Study ◽  
Thrust Faults ◽  
Dynamic Rupture ◽  
Long Distance ◽  
Fault Strength ◽  
Stress Changes ◽  
Dip Angle ◽  
3D Finite Element Method

Abstract Investigations of historic surface‐rupturing thrust earthquakes suggest that rupture can jump from one fault to another up to 8 km away. Additionally, there are observations of jumping rupture between thrust faults ∼50  km apart. In contrast, previous modeling studies of thrust faults find a maximum jumping rupture distance of merely 0.2 km. Here, we present a dynamic rupture modeling parameter study that attempts to reconcile these differences and determines geometric and stress conditions that promote jumping rupture. We use the 3D finite‐element method to model rupture on pairs of thrust faults with parallel surface traces and opposite dip orientations. We vary stress drop and fault strength ratio to determine conditions that produce jumping rupture at different dip angles and different minimum distance between faults. We find that geometry plays an essential role in determining whether or not rupture will jump to a neighboring thrust fault. Rupture is more likely to jump between faults dipping toward one another at steeper angles, and the behavior tapers down to no rupture jump in shallow dip cases. Our variations of stress parameters emphasize these toward‐orientation results. Rupture jump in faults dipping away from one another is complicated by variations of stress conditions, but the most prominent consistency is that for mid‐dip angle faults rupture rarely jumps. If initial stress conditions are such that they are already close to failure, the possibility of a long‐distance jump increases. Our models call attention to specific geometric and stress conditions where the dynamic rupture front is the most important to potential for jumping rupture. However, our models also highlight the importance of near‐field stress changes due to slip. According to our modeling, the potential for rupture to jump is strongly dependent on both dip angle and orientation of faults.

Improving the Co-seismic Slip Distributions of Synthetic Catalogs With Real Observations

2020 ◽  
Author(s):  
Hafize Başak Bayraktar ◽  
Antonio Scala ◽  
Gaetano Festa ◽  
Stefano Lorito
Keyword(s):  
Subduction Zones ◽  
Fault Plane ◽  
Active Regions ◽  
Fault Mechanics ◽  
Rupture Velocity ◽  
Seismic Slip ◽  
Tsunami Earthquakes ◽  
Seismic Cycles ◽  
Model Features ◽  
Shallow Part

<p>Subduction zones are the most seismically active regions on the globe and about 90% of historical events, including the largest ones with the magnitude M>9, occurred along these regions (Hayes et al., 2018). Most of these events were followed by devastating tsunamis with, in some cases, perhaps unexpected wave height distributions. Observation of events in the megathrust environment reveals that some earthquakes are characterized by slip concentration on the very shallow part of the subduction zone. This shallow slip phenomenon was repeatedly observed in the last two decades for both ordinary megathrust events (e.g. 2010 Maule and 2011 Tohoku) and tsunami earthquakes (2006 Java and 2010 Mentawai). Shallow ruptures feature depleted short–period energy release and very slow rupture velocity possibly due to the presence of (hydrated) sediments (Lay et al., 2011; Lay 2014; Polet and Kanamori, 2000). Associated long rupture durations have been explained with fault mechanics-related rigidity and stress drop variation with depth (Bilek and Lay, 1999) or, more recently, with lower rigidity of surrounding materials (Sallares and Ranero, 2019).</p><p>The characteristics of co-seismic slip distribution have an important impact on tsunami hazard. There are numerous methods that have been proposed to generate stochastic slip distributions, also including shallow slip amplification (Le Veque et al., 2016; Sepulveda et al., 2017; Scala et al., 2019). However, these models need to be calibrated against slip models estimated for real events.</p><p>Here, we investigate similarities and differences between the synthetic slip distributions provided by Scala et al. (2019) and a suite of 144 slip models of real events that occurred in different subduction zones (Ye et al.,2016). In particular, Scala et al. (2019) model features shallow slip amplification in single events, whose relative probabilities are balanced to restore cumulative slip homogeneity on the fault plane over multiple seismic cycles. This study also aims to improve and/or calibrate this model to account for the behavior observed from real events.</p>

scholarly journals Deserpentinization in Subduction Zones as a Source of Oxidation in Arcs: A Reality Check

2021 ◽  
Author(s):  
Katy A Evans ◽  
B Ronald Frost
Keyword(s):  
Subduction Zones ◽  
Ultramafic Rocks ◽  
Thermodynamic Models ◽  
Arc Magmas ◽  
Reality Check ◽  
Deep Earth ◽  
Tectonic Settings ◽  
Iron Bearing ◽  
Arc Magma

Abstract Previous studies have concluded that dehydration of serpentinites in subduction zones produces oxidizing fluids that are the cause of oxidized arc magmas. Here, observations of natural samples and settings are combined with thermodynamic models to explore some of the factors that complicate interpretation of the observations that form the basis of this conclusion. These factors include: the variability of serpentinite protoliths; the roles of carbon and sulfur in serpentinite evolution; variability in serpentinization in different tectonic settings; changes in the bulk compositions of ultramafic rocks during serpentinization; fundamental differences between serpentinization and deserpentinization; and the absence of precise geothermobarometers for ultramafic rocks. The capacity of serpentinite-derived fluids to oxidize sub-arc magma is also examined. These fluids can transport redox budget as carbon-, sulfur-, and iron-bearing species. Iron- and carbon-bearing species might be present in sufficient concentrations to transport redox budget deep within subduction zones, but are not viable transporters of redox budget at the temperatures of antigorite breakdown, which produces the largest proportion of fluid released by serpentinite dehydration. Sulfur-bearing species can carry significant redox budget, and calculations using the Deep Earth Water (DEW) model show that these species might be stable during antigorite breakdown. However, oxygen fugacities of ∼ΔFMQ +3 (where FMQ refers to the fayalite–magnetite–quartz buffer, and ΔFMQ is Log fO2 – Log fO2,FMQ), which is close to, or above, the hematite–magnetite buffer at the conditions of interest, are required to stabilize oxidized sulfur-bearing species. Pseudosection calculations indicate that these conditions might be attained at the conditions of antigorite breakdown if the starting serpentinites are sufficiently oxidized, but further work is required to assess the variability of serpentinite protoliths, metamorphic pressures and temperatures, and to confirm the relative positions of the mineral buffers with relation to changes in fluid speciation.

scholarly journals Rapid endogenic rock recycling in magmatic arcs

2020 ◽  
Author(s):  
Junyong Li ◽  
Ming Tang ◽  
Cin-Ty Lee ◽  
Xiaolei Wang ◽  
Zhi-Dong Gu ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Pressure Ratio ◽  
Age Distribution ◽  
Magmatic Zircon ◽  
Arc Magmatism ◽  
Thrust Faults ◽  
Yangtze Block ◽  
Zircon Age ◽  
Deep Crust ◽  
O Isotopes

Abstract In subduction zones, materials on Earth’s surface can be transported to the deep crust or mantle, but the exact mechanisms and the nature of the recycled materials are not fully understood. Here, we report a set of migmatites from western Yangtze Block, China. These migmatites have similar bulk compositions as forearc sediments. Zircon age distribution and Hf–O isotopes indicate that the precursors of the sediments were predominantly derived from juvenile arc crust itself. Using phase equilibria modelling, we show that the sediments experienced high temperature-to-pressure ratio metamorphism and were most likely transported to deep arc crust by intracrustal thrust faults. By dating the magmatic zircon cores and overgrowth rims, we find that the entire rock cycle, from arc magmatism, to weathering at the surface, then to burial and remelting in the deep crust, took place within ~ 10 Ma. Our findings highlight thrust faults as an efficient recycling channel in compressional arcs and endogenic recycling as an important mechanism driving internal redistribution and differentiation of arc crust.

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