Two Earthquake Sequences Nearly a Century Apart Reveal a Conjugate Seismogenic System in Central Taiwan

2020 ◽  
Vol 91 (3) ◽  
pp. 1469-1481 ◽  
Author(s):  
Ming-Che Hsieh ◽  
Yen-Yu Lin ◽  
Kuo-Fong Ma ◽  
Li Zhao ◽  
Yi-Wun Liao
Keyword(s):  
Active Faults ◽  
Fault System ◽  
High Angle ◽  
Mountain Building ◽  
Good Opportunity ◽  
Building Process ◽  
Orogenic Wedge ◽  
Central Taiwan ◽  
Earthquake Sequences ◽  
Conjugate Fault

Abstract Seismically active central Taiwan is considered part of an orogenic wedge with low-angle east-dipping active faults above a detachment surface and an active mountain-building process later. In 2013, two moderate reverse-faulting earthquakes of magnitudes ML 6.2 and 6.5 occurred in Nantou. They brought to mind the historically damaging sequence of four earthquakes in the same area that claimed a total of 71 lives in 1916. The 2013 earthquake sequence provides a good opportunity to study the 1916 sequence. We compared the historical Omori record of the main event in the 1916 sequence, discovered in the Seismogram Archives at the Earthquake Research Institute, University of Tokyo, and the corresponding simulated Omori records of the 2013 events. Our comparison shows significant similarity among the earthquakes, although they are separated by nearly 100 yr. To understand the seismogenic structure associated with these earthquake sequences, we further studied the source rupture properties of earthquakes in this region since 1999 using local broadband records to determine the rupture fault planes. Results show that all events have similar focal mechanisms with one low-angle east-dipping and another high-angle west-dipping nodal planes. Rupture plane determination indicates that whereas events at shallow depths (<20  km) ruptured on the low-angle east-dipping plane, events at greater depths (>20  km) slipped on the high-angle west-dipping plane in a conjugate fault system. The comparison also suggests that the 1916 sequence occurred on the low-angle east-dipping plane of this conjugate fault system in the orogenic wedge as part of a mountain-building process. Given the active mountain-building process in central Taiwan, occurrences of this type of earthquake must be addressed in seismic hazard mitigation efforts.

scholarly journals Fault interactions in a complex fault system: insight from the 1936–1997 NE Lut earthquake sequence

2020 ◽  
Vol 224 (2) ◽  
pp. 1157-1173
Author(s):  
M Marchandon ◽  
M Vergnolle ◽  
O Cavalié
Keyword(s):  
Fault System ◽  
Coulomb Stress ◽  
Coulomb Stress Changes ◽  
Fault Systems ◽  
Complex Fault ◽  
Stress Changes ◽  
Fault Interactions ◽  
Seismic Deformation ◽  
Earthquake Sequences ◽  
Conjugate Fault

SUMMARY Calculations of Coulomb stress changes have shown that moderate to large earthquakes may increase stress at the location of future earthquakes. Coulomb stress transfers have thus been widely accepted to explain earthquake sequences, especially for sequences occurring within parallel or collinear fault systems. Relating, under this framework, successive earthquakes occurring within more complex fault systems (i.e. conjugate fault system) is more challenging. In this study, we assess which ingredients of the Coulomb stress change theory are decisive for explaining the succession of three large (Mw 7+) earthquakes that occurred on a conjugate fault system in the NE Lut, East Iran, during a 30-yr period. These earthquakes belong to a larger seismic sequence made up of 11 earthquakes (Mw 5.9+) from 1936 to 1997. To reach our goal, we calculate, at each earthquake date, the stress changes generated by the static deformation of the preceding earthquakes, the following post-seismic deformation due to the viscoelastic relaxation of the lithosphere, and the interseismic deformation since 1936. We first show that accurately modelling the source and receiver fault geometry is crucial to precisely estimating Coulomb stress changes. Then we show that 7 out of 10 earthquakes of the NE Lut sequence, considering the uncertainties, are favoured by the previous earthquakes. Furthermore, the last two M7+ earthquakes of the sequence (1979 and 1997) have mainly been favoured by the moderate Mw ∼ 6 earthquakes. Finally, we investigate the link between the Coulomb stress changes due to previous earthquakes and the rupture extension of the next earthquake and show that a correlation does exist for some earthquakes but is not systematic.

Bathymetry and uplift rate of the Gulf of Aqaba, Dead Sea Fault.

2021 ◽  
Author(s):  
Matthieu Ribot ◽  
Yann Klinger ◽  
Edwige Pons-Branchu ◽  
Marthe Lefevre ◽  
Sigurjón Jónsson
Keyword(s):  
High Resolution ◽  
Tectonic Evolution ◽  
Active Faults ◽  
Major Change ◽  
Dead Sea ◽  
Fault System ◽  
Arabian Plate ◽  
Gulf Of Aqaba ◽  
Uplift Rate ◽  
The Dead

<p>Initially described in the late 50’s, the Dead Sea Fault system connects at its southern end to the Red Sea extensive system, through a succession of left-stepping faults. In this region, the left-lateral differential displacement of the Arabian plate with respect to the Sinai micro-plate along the Dead Sea fault results in the formation of a depression corresponding to the Gulf Aqaba. We acquired new bathymetric data in the areas of the Gulf of Aqaba and Strait of Tiran during two marine campaigns (June 2018, September 2019) in order to investigate the location of the active faults, which structure and control the morphology of the area. The high-resolution datasets (10-m posting) allow us to present a new fault map of the gulf and to discuss the seismic potential of the main active faults.</p><p>We also investigated the eastern margin of the Gulf of Aqaba and Tiran island to assess the vertical uplift rate. To do so, we computed high-resolution topographic data and we processed new series of U-Th analyses on corals from the uplifted marine terraces.</p><p>Combining our results with previous studies, we determined the local and the regional uplift in the area of the Gulf of Aqaba and Strait of Tiran.</p><p>Eventually, we discussed the tectonic evolution of the gulf since the last major change of the tectonic regime and we propose a revised tectonic evolution model of the area.</p><p> </p>

scholarly journals Empirical Relationship for Assessing the Near-Field Horizontal Coseismic Displacement Using GPS Seismology Data

2021 ◽  
Vol 60 (1) ◽  
pp. 31-50
Author(s):  
Ryad Darawcheh ◽  
Riad Al Ghazzi ◽  
Mohamad Khir Abdul-wahed
Keyword(s):  
Near Field ◽  
Empirical Relationship ◽  
Active Faults ◽  
Historical Earthquakes ◽  
Dead Sea ◽  
Fault System ◽  
Coseismic Displacement ◽  
Data Set ◽  
Earthquake Parameters ◽  
Gps Station

In this research, a data set of horizontal GPS coseismic displacement in the near-field has been assembled around the world in order to investigate a potential relationship between the displacement and the earthquake parameters. Regression analyses have been applied to the data of 120 interplate earthquakes having the magnitude (Mw 4.8-9.2). An empirical relationship for prediction near-field horizontal GPS coseismic displacement as a function of moment magnitude and the distance between hypocenter and near field GPS station has been established using the multi regression analysis. The obtained relationship allows assessing the coseismic displacements associated with some large historical earthquakes occurred along the Dead Sea fault system. Such a fair relationship could be useful for assessing the coseismic displacement at any point around the active faults.

Numerical simulation of earthquake sequences

1977 ◽  
Vol 67 (5) ◽  
pp. 1363-1377
Author(s):  
John B. Rundle ◽  
David D. Jackson
Keyword(s):  
Numerical Simulation ◽  
Crack Nucleation ◽  
Fault System ◽  
One Dimensional ◽  
Linear Behavior ◽  
Frequency Relation ◽  
Earthquake Sequences ◽  
Poissonian Statistics ◽  
Stored Elastic Energy ◽  
Good Agreement

abstract Numerical simulation of earthquake occurrence using a one-dimensional fault model demonstrates that (a) the linear behavior of the magnitude-frequency relation is not an immutable law but rather is dependent on the mechanical properties of the fault, (b) “randomness” as measured by adherence to Poissonian statistics does not preclude useful prediction by statistical means, (c) the rate of occurrence of simulated earthquakes is in good agreement with the Kolmogorov model in which seismicity is related primarily to the stored elastic energy in a fault system, and (d) the occurrence of foreshocks and aftershocks can be well explained by the occurrence of stress-induced crack nucleation.

Recent earthquake sequences at Coso: Evidence for conjugate faulting and stress loading near a geothermal field

1999 ◽  
Vol 89 (3) ◽  
pp. 785-795 ◽  
Author(s):  
Joydeep Bhattacharyya ◽  
Susanna Gross ◽  
Jonathan Lees ◽  
Mike Hastings
Keyword(s):  
Geothermal Field ◽  
Fault System ◽  
Fault Plane Solutions ◽  
Temporal Decay ◽  
Background Seismicity ◽  
Surface Ruptures ◽  
Temporal And Spatial Characteristics ◽  
Coso Geothermal Field ◽  
The One ◽  
Earthquake Sequences

Abstract Two recent earthquake sequences near the Coso geothermal field show clear evidence of faulting along conjugate planes. We present results from analyzing an earthquake sequence occurring in 1998 and compare it with a similar sequence that occurred in 1996. The two sequences followed mainshocks that occurred on 27 November 1996 and 6 March 1998. Both mainshocks ruptured approximately colocated regions of the same fault system. Following a comparison with the background seismicity of the Coso region, we have detected evidence of stress loading within the geothermal field that appears to be in response to the 1998 earthquakes. The ML = 5.2 mainshock in the 1998 sequence occurred at 5:47 a.m. UTC and was located approximately 45 km north of the town of Ridgecrest in the Coso range. The mainshock of the 1996 sequence had an ML magnitude of 5.3. There have been no observable surface ruptures associated with either of these sequences. Though the mainshocks for both sequences were located about 900 m apart and have nearly the same local magnitudes, the sequences differ in both their temporal and spatial characteristics. An analysis of the fault-plane solutions of the mainshocks and the aftershock locations suggests that the two sequences ruptured fault planes that are perpendicular to one another. We observe a much faster temporal decay of the 1998 sequence compared to the one in 1996; moreover, while the 1996 sequence was not followed by any sizeable (i.e., ML > 4.0) aftershocks, the 1998 sequence had four such events. From an estimate of the tectonic stressing rate on the fault that produced the 1998 sequence, we infer a repeat cycle of 135 years for an earthquake of comparable magnitude at Coso.

scholarly journals Morphotectonic Kinematic Indicators along the Vigan-Aggao Fault: The Western Deformation Front of the Philippine Fault Zone in Northern Luzon, the Philippines

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 83 ◽  
Author(s):  
Rolly E. Rimando ◽  
Jeremy M. Rimando
Keyword(s):  
Fault Zone ◽  
Active Fault ◽  
Active Faults ◽  
Vertical Component ◽  
The Philippines ◽  
Google Earth ◽  
Fault System ◽  
Philippine Sea Plate ◽  
Oblique Convergence ◽  
Philippine Fault Zone

The Vigan-Aggao Fault is a 140-km-long complex active fault system consisting of multiple traces in the westernmost part of the Philippine Fault Zone (PFZ) in northern Luzon, the Philippines. In this paper, its traces, segmentation, and oblique left-lateral strike-slip motion are determined from horizontal and vertical displacements measured from over a thousand piercing points pricked from displaced spurs and streams observed from Google Earth Pro satellite images. This work marks the first instance of the extensive use of Google Earth as a tool in mapping and determining the kinematics of active faults. Complete 3D image coverage of a major thoroughgoing active fault system is freely and easily accessible on the Google Earth Pro platform. It provides a great advantage to researchers collecting morphotectonic displacement data, especially where access to aerial photos covering the entire fault system is next to impossible. This tool has not been applied in the past due to apprehensions on the positional measurement accuracy (mainly of the vertical component). The new method outlined in this paper demonstrates the applicability of this tool in the detailed mapping of active fault traces through a neotectonic analysis of fault-zone features. From the sense of motion of the active faults in northern Luzon and of the major bounding faults in central Luzon, the nature of deformation in these regions can be inferred. An understanding of the kinematics is critical in appreciating the distribution and the preferred mode of accommodation of deformation by faulting in central and northern Luzon resulting from oblique convergence of the Sunda Plate and the Philippine Sea Plate. The location, extent, segmentation patterns, and sense of motion of active faults are critical in coming up with reasonable estimates of the hazards involved and identifying areas prone to these hazards. The magnitude of earthquakes is also partly dependent on the type and nature of fault movement. With a proper evaluation of these parameters, earthquake hazards and their effects in different tectonic settings worldwide can be estimated more accurately.

scholarly journals Methodology for Earthquake Rupture Rate estimates of fault networks: example for the Western Corinth Rift, Greece

2017 ◽  
Author(s):  
Thomas Chartier ◽  
Oona Scotti ◽  
Hélène Lyon-Caen ◽  
Aurélien Boiselet
Keyword(s):  
Active Faults ◽  
Slip Rate ◽  
Seismic Hazard Assessment ◽  
System Level ◽  
Fault System ◽  
Normal Faults ◽  
Accurate Estimation ◽  
Probabilistic Seismic Hazard Assessment ◽  
Earthquake Rupture ◽  
Multiple Faults

Abstract. Modelling the seismic potential of active faults is a fundamental step of probabilistic seismic hazard assessment (PSHA). An accurate estimation of the rate of earthquakes on the faults is necessary in order to obtain the probability of exceedance of a given ground motion. Most PSHA studies consider faults as independent structures and neglect the possibility of multiple faults or fault segments rupturing simultaneously (Fault to Fault -FtF- ruptures). The latest Californian model (UCERF-3) takes into account this possibility by considering a system level approach rather than an individual fault level approach using the geological , seismological and geodetical information to invert the earthquake rates. In many places of the world seismological and geodetical information long fault networks are often not well constrained. There is therefore a need to propose a methodology relying only on geological information to compute earthquake rate of the faults in the network. In this methodology, similarly to UCERF-3, a simple distance criteria is used to define FtF ruptures and consider single faults or FtF ruptures as an aleatory uncertainty. Rates of earthquakes on faults are then computed following two constraints: the magnitude frequency distribution (MFD) of earthquakes in the fault system as a whole must follow an imposed shape and the rate of earthquakes on each fault is determined by the specific slip-rate of each segment depending on the possible FtF ruptures. The modelled earthquake rates are then confronted to the available independent data (geodetical, seismological and paleoseismological data) in order to weigh different hypothesis explored in a logic tree. The methodology is tested on the Western Corinth Rift, Greece (WCR) where recent advancements have been made in the understanding of the geological slip rates of the complex network of normal faults which are accommodating the ~15 mm/yr North-South extension. Modelling results show that geological, seismological extension rates and paleoseismological rates of earthquakes cannot be reconciled with only single fault rupture scenarios and require hypothesising a large spectrum of possible FtF rupture sets. Furthermore, in order to fit the imposed regional Gutenberg-Richter MFD target, some of the slip along certain faults needs to be accommodated either with interseismic creep or as post-seismic processes. Furthermore, individual fault’s MFDs differ depending on the position of each fault in the system and the possible FtF ruptures associated with the fault. Finally, a comparison of modelled earthquake rupture rates with those deduced from the regional and local earthquake catalogue statistics and local paleosismological data indicates a better fit with the FtF rupture set constructed with a distance criteria based on a 5 km rather than 3 km, suggesting, a high connectivity of faults in the WCR fault system.

Active Faulting in Source Region of 2016–2017 Central Italy Event Sequence

2018 ◽  
Vol 34 (4) ◽  
pp. 1557-1583 ◽  
Author(s):  
Fabrizio Galadini ◽  
Emanuela Falcucci ◽  
Stefano Gori ◽  
Paolo Zimmaro ◽  
Daniele Cheloni ◽  
...  
Keyword(s):  
Source Region ◽  
Central Italy ◽  
Active Faults ◽  
Earthquake Sequence ◽  
Fault System ◽  
Fault Plane Solutions ◽  
Moment Tensors ◽  
Central Italy Earthquake ◽  
Finite Fault ◽  
Main Shocks

The Central Italy earthquake sequence produced three main shocks: M6.1 24 August, M5.9 26 October, and M6.5 30 October 2016. Additional M5–5.5 events struck this territory on 18 January 2017 in the Campotosto area. Fault plane solutions for the main shocks exhibit normal faulting (characteristic of crustal extension occurring in the inner central Apennines). Significant evidence, including hypocenter locations, strike and dip angles of the moment tensors, inverted finite fault models (using GPS, interferometric aperture radar, and ground motion data), and surface rupture patterns, all point to the earthquakes having been generated on the Mt. Vettore–Mt. Bove fault system (all three main shocks) and on the Amatrice fault, in the northern sector of the Laga Mountains (portion of 24 August event). The earthquake sequence provides examples of both synthetic and antithetic ruptures on a single fault system (30 October event) and rupture between two faults (24 August event). We describe active faults in the region and their segmentation and present understanding of the potential for linkages between segments (or faults) in the generation of large earthquakes.

Paleo-surface ruptures at both sides of a pressure ridge along Alhama de Murcia Fault (SE Spain)

2020 ◽  
Author(s):  
Octavi Gómez-Novell ◽  
María Ortuño ◽  
Julián García-Mayordomo ◽  
Eulàlia Masana ◽  
Thomas Rockwell ◽  
...  
Keyword(s):  
Active Faults ◽  
Great Part ◽  
Slip Rate ◽  
Fault System ◽  
Radiocarbon Dates ◽  
Seismic Parameters ◽  
Central Segment ◽  
Pressure Ridge ◽  
Combining Data ◽  
Surface Ruptures

<p>The Alhama de Murcia Fault (AMF) is one of the most seismically active faults in the Iberian Peninsula, with important associated historical and instrumental seismicity (e.g. the 1674 I<sub>EMS </sub>VIII and 2011 Mw 5.1 Lorca earthquakes), and numerous geomorphic and paleoseismic evidence of paleoearthquakes. It is an oblique left-lateral strike slip fault within the Eastern Betics Shear Zone (EBSZ), a nearly 500 km long fault system that absorbs a great part of convergence between the Nubian and Eurasian plates. Previous paleoseismic studies have mainly focused on the southwestern and especially the central segment of the fault and yielded slip rate values ranging from 1.0 up to 1.7 mm/yr. In the central segment (Lorca-Totana), the fault splays into several branches, the two frontal ones forming a pressure ridge. Paleoseismic trenches have exclusively been dug in the northwestern fault of the pressure ridge, where most of the displacement is along strike, while the expected reverse southeastern branch has never been directly observed.</p><p>We present the first results of paleoseismic trenching across a complete transect of the pressure ridge in the Lorca-Totana segment of AMF. To do so we excavated an exceptionally large trench (7 m deep) in the NW branch and 5 trenches in the SE branch. We have been able to: a) extend the paleoearthquake catalogue in the NW branch by interpreting a total of 13 paleoearthquakes, 6 of which were not identified in previous studies. A restoration analysis has been performed; b) unveil the existence and recent activity (Holocene) of the thrust that bounds the pressure ridge to the SE. We have interpreted at least 5 surface ruptures, with the last one being younger than 8-9 kyr BP, based on new radiocarbon dates.</p><p>The study of these two sites allows for the refinement of the seismic parameters of the fault, formerly inferred from the study of a single branch. In this sense, the more complete paleoearthquake catalogue will allow for reassessment of the recurrence intervals assigned to the fault and new slip rate estimates will be inferred by combining data from the two studied sites. Furthermore, forthcoming OSL dates may allow us to prove or reject the synchronicity of surface ruptures on both sides of the pressure ridge, shedding light on the rupturing style of this fault system during the Late Quaternary. We discuss how these new data on fault-interaction may affect several seismic parameters and their repercussion in source modelling for fault-based probabilistic seismic hazard assessments (PSHA) of the region.</p>

scholarly journals The seismogenic fault system of the 2017 <i>M<sub>w</sub></i> 7.3 Iran-Iraq earthquake: constraints from surface and subsurface data, cross-section balancing and restoration

2018 ◽  
Author(s):  
Stefano Tavani ◽  
Mariano Parente ◽  
Francesco Puzone ◽  
Amerigo Corradetti ◽  
Gholamreza Gharabeigli ◽  
...  
Keyword(s):  
Cross Section ◽  
Sedimentary Cover ◽  
Active Faults ◽  
Fault System ◽  
Limited Information ◽  
Seismogenic Fault ◽  
Plate Convergence ◽  
Mountain Front ◽  
Seismogenic Structures ◽  
Seismic Reflection Profiles

Abstract. The 2017 Mw Iran-Iraq earthquake occurred in a region where the pattern of major plate convergence is well constrained, but limited information is available on the seismogenic structures. Geological observations, interpretation of seismic reflection profiles, and well data are used in this paper to build a regional balanced cross-section that provides a comprehensive picture of the geometry and dimensional parameters of active faults in the hypocentral area. Our results indicate: (i) coexistence of thin- and thick-skinned thrusting, (ii) reactivation of inherited structures, and (iii) occurrence of weak units promoting heterogeneous deformation within the Paleo-Cenozoic sedimentary cover and partial decoupling from the underlying basement. According to our study, the main shock of the November 2017 seismic sequence is located within the basement, along the low-angle Mountain Front Fault. Aftershocks unzipped the up-dip portion of the same fault. This merges with a detachment level located at the base of the Paleozoic succession, to form a crustal-scale fault-bend anticline. Size and geometry of the Mountain Front Fault are consistent with a down-dip rupture width of 30 km, which is required for an Mw 7.3 earthquake.

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