scholarly journals Magnitude-Dependent Transient Increase of Seismogenic Depth

2020 ◽  
Vol 91 (4) ◽  
pp. 2182-2191
Author(s):  
Olaf Zielke ◽  
Danijel Schorlemmer ◽  
Sigurjon Jónsson ◽  
Paul Martin Mai
Keyword(s):  
Transition Zone ◽  
Fault System ◽  
Seismogenic Zone ◽  
Tectonic Deformation ◽  
Rupture Length ◽  
Strain And Strain Rate ◽  
Background Seismicity ◽  
Earthquake Size ◽  
Large Earthquakes

Abstract The thickness of the seismogenic zone in the Earth’s crust plays an important role in seismotectonics, affecting fault-system architecture and relative fault activity, earthquake size and distribution within a fault system, as well as long-term accumulation of tectonic deformation. Within the last two decades, several studies have revealed that aftershocks of large continental earthquakes may occur below the background depth of the seismogenic zone, that is, below the seismic–aseismic transition zone. This observation may be explained with a strain- and strain-rate-induced shift in rheological behavior that follows large mainshocks, transiently changing the deformation style below the seismogenic zone from incipient ductile to seismically brittle failure. As large earthquakes transiently deepen the seismic–aseismic transition zone, it is plausible to assume that larger mainshocks may cause stronger deepening than smaller mainshocks. Corresponding observations, however, have not yet been reported. Here, we use well-located seismic catalogs from Alaska, California, Japan, and Turkey to analyze if mainshock size positively correlates with the amount of transient deepening of the seismic–aseismic transition zone. We compare the depths of background seismicity with aftershock depths of 16 continental strike-slip earthquakes (6≤M≤7.8) and find that large mainshocks do cause stronger transient deepening than moderate-size mainshocks. We further suggest that this deepening effect also applies to the mainshocks themselves, with larger mainshock coseismic ruptures being capable of extending deeper into the normally aseismic zone. This understanding may help address fundamental questions of earthquake-source physics such as the assumed scale invariance of earthquake stress drop and whether fault-slip scales with rupture length or rupture width.

Erosion rates of the New Zealand Southern Alps reflect long-term tectonics and transient climate

2021 ◽  
Author(s):  
Duna Roda-Boluda ◽  
Taylor Schildgen ◽  
Hella Wittmann-Oelze ◽  
Stefanie Tofelde ◽  
Aaron Bufe ◽  
...  
Keyword(s):  
New Zealand ◽  
Strike Slip ◽  
Southern Alps ◽  
Fault System ◽  
Tectonic Deformation ◽  
Seismic Cycle ◽  
Erosion Rates ◽  
Alpine Fault ◽  
Oblique Convergence

<p>The Southern Alps of New Zealand are the expression of the oblique convergence between the Pacific and Australian plates, which move at a relative velocity of nearly 40 mm/yr. This convergence is accommodated by the range-bounding Alpine Fault, with a strike-slip component of ~30-40 mm/yr, and a shortening component normal to the fault of ~8-10 mm/yr. While strike-slip rates seem to be fairly constant along the Alpine Fault, throw rates appear to vary considerably, and whether the locus of maximum exhumation is located near the fault, at the main drainage divide, or part-way between, is still debated. These uncertainties stem from very limited data characterizing vertical deformation rates along and across the Southern Alps. Thermochronology has constrained the Southern Alps exhumation history since the Miocene, but Quaternary exhumation is hard to resolve precisely due to the very high exhumation rates. Likewise, GPS surveys estimate a vertical uplift of ~5 mm/yr, but integrate only over ~10 yr timescales and are restricted to one transect across the range.</p><p>To obtain insights into the Quaternary distribution and rates of exhumation of the western Southern Alps, we use new <sup>10</sup>Be catchment-averaged erosion rates from 20 catchments along the western side of the range. Catchment-averaged erosion rates span an order of magnitude, between ~0.8 and >10 mm/yr, but we find that erosion rates of >10 mm/yr, a value often quoted in the literature as representative for the entire range, are very localized. Moreover, erosion rates decrease sharply north of the intersection with the Marlborough Fault System, suggesting substantial slip partitioning. These <sup>10</sup>Be catchment-averaged erosion rates integrate, on average, over the last ~300 yrs. Considering that the last earthquake on the Alpine Fault was in 1717, these rates are representative of inter-seismic erosion. Lake sedimentation rates and coseismic landslide modelling suggest that long-term (~10<sup>3</sup> yrs) erosion rates over a full seismic cycle could be ~40% greater than our inter-seismic erosion rates. If we assume steady state topography, such a scaling of our <sup>10</sup>Be erosion rate estimates can be used to estimate rock uplift rates in the Southern Alps. Finally, we find that erosion, and hence potentially exhumation, does not seem to be localized at a particular distance from the fault, as some tectonic and provenance studies have suggested. Instead, we find that superimposed on the primary tectonic control, there is an elevation/temperature control on erosion rates, which is probably transient and related to frost-cracking and glacial retreat.</p><p>Our results highlight the potential for <sup>10</sup>Be catchment-averaged erosion rates to provide insights into the magnitude and distribution of tectonic deformation rates, and the limitations that arise from transient erosion controls related to the seismic cycle and climate-modulated surface processes.</p><p> </p><p> </p>

scholarly journals Contrasting seismogenic behaviors on the North Anatolian Fault in the Sea of Marmara

2020 ◽  
Author(s):  
Pierre Henry ◽  
Céline Grall ◽  
M Sinan Özeren ◽  
Volkan Özbey ◽  
Gülsen Uçarkus ◽  
...  
Keyword(s):  
Heat Flow ◽  
Sedimentary Cover ◽  
Large Earthquake ◽  
Fault Slip ◽  
North Anatolian Fault ◽  
Fault System ◽  
Seismogenic Zone ◽  
Sea Of Marmara ◽  
The North

<p>Since the 1999 Izmit-Kocaeli earthquake, the Main Marmara Fault (MMF) of the North Anatolian Fault system in the Sea of Marmara has been considered at an imminent risk for a large earthquake. Land geodesy has difficulties characterizing the distribution of interseismic loading, and hence of slip deficit, on the offshore faults, and notably on the Istanbul-Silivri segment of the NAF. The need to clarify the status of offshore fault segments has motivated seafloor monitoring experiments and marine geophysical and sedimentological studies, notably in the framework of EMSO consortium and MARSITE and MAREGAMI projects. Results from cross-disciplinary projects have shown that aseismic creep, spatially correlated to active gas venting at the seafloor, occurs on the Western segment of the MMF. This segment is also capable to large earthquake ruptures such as the 1912 event. On the eastern part of the Sea of Marmara, the Istanbul-Silivri and Prince Island segments appear essentially locked. Moreover, the base of the seismogenic zone and locking depth appears to shallow (from 15-20 to 10-15 km) from west to east.</p><p>On one hand, we propose to further evaluate fault slip rates and distribution of locking ratio on individual fault segments using an elastic block model constrained by land geodesy data and marine observations (long-term fault slip rate estimates, local acoustic ranging results). On the other hand, we evaluate the temperature at the seismogenic depths by basin modelling. Results suggest that spatial variations of fault behavior in the Sea of Marmara may result from a combination of factors. First, thermogenic gas generation within the > 6 km thick sedimentary cover in the Western Sea of Marmara may contribute to unlock the shallow part of the fault by generating overpressures. Second, heterogeneity of the crust composition could be a factor as the North Anatolian Fault system follows the intra-pontide ophiolitic suture. For instance, long term post-seismic creep onland at Ismet Paşa has been related to the presence of serpentinite in the fault zone. Moreover, high-density magnetic bodies have been identified along the MMF. Third, varying thermal regimes between the Western and Eastern parts of the Sea of Marmara may account for variations in the seismogenic depths. Seafloor heat flow in the Sea of Marmara is strongly affected by sediment blanketing and basin modeling considering this process suggests that the crustal heat flow is about 20 mW/m<sup>2</sup> higher in the eastern part than in western part of the Sea of Marmara. This difference may be explained by a more spread out crustal extension in the western Sea of Marmara.</p>

What Can Surface-Slip Distributions Tell Us about Fault Connectivity at Depth?

2020 ◽  
Vol 110 (3) ◽  
pp. 1025-1036
Author(s):  
David D. Oglesby
Keyword(s):  
Spatial Distribution ◽  
Alternative Explanation ◽  
Fault System ◽  
Seismogenic Zone ◽  
Dynamic Rupture ◽  
Fault Segment ◽  
Surface Slip ◽  
Fault Systems ◽  
Earthquake Size ◽  
Different Sources

ABSTRACT Fault systems with stepovers and gaps along strike are ubiquitous in nature, and many modern earthquakes (e.g., 1992 Landers, 1999 Hector Mine, 2016 Kaikōura, and 2019 Ridgecrest) have shown that ruptures can readily propagate across some disconnections, while being halted by others. It is quite possible, however, that many faults that appear discontinuous at the surface are in fact connected at depth, facilitating throughgoing rupture, and potentially increasing earthquake size. The present work explores whether the mapped surface slip in an earthquake is indicative of the connectivity of the fault system at depth. If there is a signal of subsurface connectivity in the surface-slip pattern, then the connectivity of the system could potentially be inferred. Through 3D dynamic rupture modeling of faults with along-strike gaps of various depths, I explore whether the amplitude or the spatial distribution of slip after an earthquake could be used to diagnose fault connectivity at depth. I find that, in general, fault segments that are connected up to shallow depths of 1–2 km and are relatively long along strike compared to the seismogenic depth tend to have higher slip gradients at their edges than faults that are connected at greater depth, or that are disconnected to the bottom of the seismogenic zone. Systematic slip gradient differences at fault segment edges have been recorded in past earthquakes, giving hope that the modeled effect can be detected in many cases, even though mapped surface slip is affected by a number of different sources of heterogeneity. The results provide an alternative explanation for observations that stepovers that allow throughgoing rupture tend to have higher slip gradients than those at which rupture terminates: perhaps many such stepovers are connected at depth, which could persistently favor throughgoing rupture. There may be implications for interpretation of apparent fault discontinuities worldwide.

Insight on the results of three different correlation analyses between satellite TIR anomalies and earthquake occurrence

2021 ◽  
Author(s):  
Carolina Filizzola ◽  
Roberto Colonna ◽  
Alexander Eleftheriou ◽  
Nicola Genzano ◽  
Katsumi Hattori ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
International Workshop ◽  
Statistical Correlation ◽  
Physical Models ◽  
Short Term ◽  
Correlation Analyses ◽  
Multi Temporal ◽  
Casual Relation ◽  
Large Earthquakes

<p>In order to evaluate the potentiality of the parameter “RST-based satellite TIR anomalies” in relation with earthquake (M≥4) occurrence, in recent years we performed three long-term statistical correlation analyses on different seismically active areas, such as Greece (Eleftheriou et al., 2016), Italy (Genzano et al., 2020), and Japan (Genzano et al., 2021).</p><p>With this aim, by means of the RST (Robust Satellite Techniques; Tramutoli, 1998, 2007) approach we analysed ten-year time series of satellite images collected by the SEVIRI sensor (on board the MSG platforms) over Greece (2004-2013) and Italy (2004-2014), and by the JAMI and IMAGER sensors (on board the MTSAT satellites) over Japan (2005-2015).  By applying empirical spatial-temporal rules, which are established also taking account of the physical models up to now proposed to explain seismic TIR anomaly appearances, the performed long -term correlation analyses put in relief that a non-casual relation exists between satellite TIR anomalies and the occurrence of earthquakes.</p><p>At the same time, in the carried out studies we introduced and validated refinements and improvements to the RST approach, which are able to minimize the proliferation of the false positives (i.e. TIR anomalies independent from the seismic sources, but due to other causes such as meteorological factors).    </p><p>Here, we summarize the achieved results and discuss them from the perspective of a multi-parameter system, which could improve our present knowledge on the earthquake-related processes and increase our capacity to assess the seismic hazard in the medium-short term (months to days).</p><p> </p><p>References</p><p>Eleftheriou, A., C. Filizzola, N. Genzano, T. Lacava, M. Lisi, R. Paciello, N. Pergola, F. Vallianatos, and V. Tramutoli (2016), Long-Term RST Analysis of Anomalous TIR Sequences in Relation with Earthquakes Occurred in Greece in the Period 2004–2013, Pure Appl. Geophys., 173(1), 285–303, doi:10.1007/s00024-015-1116-8.</p><p>Genzano, N., C. Filizzola, M. Lisi, N. Pergola, and V. Tramutoli (2020), Toward the development of a multi parametric system for a short-term assessment of the seismic hazard in Italy, Ann. Geophys, 63, 5, PA550, doi:10.4401/ag-8227.</p><p>Genzano, N., C. Filizzola, K. Hattori, N. Pergola, and V. Tramutoli (2021), Statistical correlation analysis between thermal infrared anomalies observed from MTSATs and large earthquakes occurred in Japan (2005 - 2015), Journal of Geophysics Research – Solid Earth, doi: 10.1029/2020JB020108 (accepted).</p><p>Tramutoli, V. (1998), Robust AVHRR Techniques (RAT) for Environmental Monitoring: theory and applications, in Proceedings of SPIE, vol. 3496, edited by E. Zilioli, pp. 101–113, doi: 10.1117/12.332714</p><p>Tramutoli, V. (2007), Robust Satellite Techniques (RST) for Natural and Environmental Hazards Monitoring and Mitigation: Theory and Applications, in 2007 International Workshop on the Analysis of Multi-temporal Remote Sensing Images, pp. 1–6, IEEE. doi: 10.1109/MULTITEMP.2007.4293057</p>

scholarly journals Long-Term Effects of Vegetation Treatments in the Chaparral Transition Zone

Rangelands ◽  
2001 ◽  
Vol 23 (1) ◽  
Author(s):  
Kelly N. Fuhrmann ◽  
Timothy E. Crews ◽  
Keyword(s):  
Transition Zone ◽  
Long Term Effects

scholarly journals Bachatskiy induced earthquake on June 18, 2013, ML=6.1, I0=7 (Kuzbass)

2020 ◽  
Vol 2 (1) ◽  
pp. 48-61 ◽  
Author(s):  
Aleksandr Emanov ◽  
Aleksey Emanov ◽  
Aleksandr Fateev
Keyword(s):  
B Value ◽  
Mountain Area ◽  
Seismic Arrays ◽  
Seismic Activation ◽  
Background Seismicity ◽  
Single Process ◽  
Strip Mine ◽  
Large Earthquakes ◽  
Sayan Mountain ◽  
Natural Seismicity

The Bachatsky earthquake of 18 June 2013 and a seismic activation of the same name coal strip mine, started several years before the earthquake and still persists today, have been studied using temporal local seismic arrays in the area. It was found experimentally that the seismic process area is closely connected to open workings, and the earthquakes are extend-ed from the working bed to a depth of 4-5 km. Adjacent to the mine depression sedimentary rocks were activated. The technogenic seismic regime is continuous and not stationary: intervals of background seismicity with relatively weak and seldom events are disturbed by bursts of activity with a rise in the magnitude of stronger earthquakes and frequency of occurrence of weak events. The seismic activation may last for 1–3 months. During the last five years, four seismic activations have been recorded, three of which were generated by large earthquakes of 09.02.2012, ML4.3; 04.03.2013, ML3.9; 18.06.2013, ML6.1. The last one was completed by a series of perceptible earthquakes with local magnitude of 3.0–3.5. The focal mechanism of the Bachatsky earthquake is a thrust fault with one of the motion planes corresponding to the anthropogenic impact. The earthquake flow forms a single process in the space with the b-value of the Gutenberg-Richter relationship different from the natural seismicity. The studied induced seismicity does not correspond to the structural regularities of natural seismicity in the Altai-Sayan mountain area. The findings prove that the Bachatsky earthquake and associated activation can be considered as man-made events.

scholarly journals Modeling long-term volcanic deformation at Kusatsu-Shirane and Asama volcanoes, Japan, using the GNSS coordinate time series

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hiroshi Munekane
Keyword(s):  
Source Parameters ◽  
Tohoku Earthquake ◽  
Oblate Spheroid ◽  
Satellite System ◽  
Deformation Source ◽  
Postseismic Deformation ◽  
Tectonic Deformation ◽  
Linear Inversion ◽  
The 2011 Tohoku Earthquake

AbstractLong-term deformation of Kusatsu-Shirane and Asama volcanoes in central Japan were investigated using Global Navigation Satellite System (GNSS) measurements. Large postseismic deformation caused by the 2011 Tohoku earthquake—which obscures the long-term volcanic deformation—was effectively removed by approximating the postseismic and other recent tectonic deformation in terms of quadrature of the geographical eastings/northings. Subsequently, deformation source parameters were estimated by the Markov Chain Monte Carlo (MCMC) method and linear inversion, employing an analytical model that calculates the deformation from an arbitrary oriented prolate/oblate spheroid. The deformation source of Kusatsu-Shirane volcano was found to be a sill-like oblate spheroid located a few kilometers northwest of the Yugama crater at a depth of approximately 4 $$\text {km}$$ km , while that of Asama was also estimated to be a sill-like oblate spheroid beneath the western flank of the edifice at a depth of approximately 12 $$\text {km}$$ km , along with the previously reported shallow east–west striking dike at a depth of approximately 1 $$\text {km}$$ km . It was revealed that (1) volume changes of the Kusatsu-Shirane deformation source and the shallow deformation source of Asama were correlated with the volcanic activities of the corresponding volcanoes, and (2) the Asama deep source has been steadily losing volume, which may indicate that the volcano will experience fewer eruptions in the near future.

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