scholarly journals Evaluating variability in coseismic slips of paleo-earthquakes using a flight of displaced terraces across the Kamishiro fault, Itoigawa-Shizuoka Tectonic Line, central Japan

2020 ◽  
Author(s):  
Naoya Takahashi ◽  
Shinji Toda
Keyword(s):  
Monte Carlo ◽  
Three Dimensional ◽  
Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard Assessment ◽  
Reverse Fault ◽  
Coseismic Slip ◽  
Central Japan ◽  
Systematic Analysis ◽  
Multiple Faults ◽  
Fluvial Terraces

Abstract Examining the regularity between events during an earthquake slip leads to an understanding of earthquake recurrence and provides the basis for probabilistic seismic hazard assessment. Generally, scientists use systematic analysis of three-dimensional paleoseismic trenches and numerous offset markers along fault zones to study slip history. Flights of displaced terraces have also been used, under the assumption that the number of earthquakes contributing to the observed cumulative slip is known. This study presents a Monte Carlo-based approach to estimating slip variability from a series of displaced terraces when such an assumption cannot be satisfied. First, we mapped fluvial terraces across the Kamishiro Fault, which is an intra-plate reverse fault in central Japan, and systematically measured the cumulative net slip in the mapped terraces. By combining these measurements with the age of the paleoearthquakes, we estimated the amount of net slip for the penultimate event (PE) and antepenultimate event (APE) to be 1.5 ± 0.2 and 2.7 ± 0.4 m, respectively. The APE slip was twice that of the PE slip and 2.5 times larger than the most recent event, the Nagano-ken-hokubu earthquake, and measured 1.2 ± 0.1 m. This suggests that the APE ruptured along the entire length of the 26 km-long Kamishiro Fault or that there were multiple faults involving adjacent segments. As we are unsure how many earthquakes had occurred since the oldest terrace was formed, we assumed three cases based on available paleoseismic records. In each case, we calculated the slip that could reproduce the cumulative slips within a reasonable range of observed terrace offsets and then estimated the coefficient of variation for coseismic slips (COVs) of paleoearthquakes. The resulting COVs typically fell into the range of 0.3 to 0.5, indicating that, over the last few thousand years, the Kamishiro Fault did not regularly behave as it had done before the 2014 event. Instead, there were large variations in the fault’s coseismic slip, as suggested by the global dataset. Although we acknowledge that our approach may be oversimplified, the Monte Carlo-based approach should help assess the regularity of earthquakes from displaced terraces where limited data are available.

scholarly journals Evaluating variability in coseismic slips of paleoearthquakes from an incomplete slip history: an example from displaced terrace flights across the Kamishiro fault, central Japan

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Naoya Takahashi ◽  
Shinji Toda
Keyword(s):  
Monte Carlo ◽  
Three Dimensional ◽  
Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard Assessment ◽  
Reverse Fault ◽  
Central Japan ◽  
Systematic Analysis ◽  
Fluvial Terraces ◽  
Rupture Length ◽  
Slip History

AbstractExamining the regularity in slip over seismic cycles leads to an understanding of earthquake recurrence and provides the basis for probabilistic seismic hazard assessment. Systematic analysis of three-dimensional paleoseismic trenches and analysis of offset markers along faults reveal slip history. Flights of displaced terraces have also been used to study slips of paleoearthquakes when the number of earthquakes contributing to the observed displacement of a terrace is known. This study presents a Monte Carlo-based approach to estimating slip variability using displaced terraces when a detailed paleoseismic record is not available. First, we mapped fluvial terraces across the Kamishiro fault, which is an intra-plate reverse fault in central Japan, and systematically measured the cumulative dip slip of the mapped terraces. By combining these measurements with the age of the paleoearthquakes, we estimated the amount of dip slip for the penultimate event (PE) and antepenultimate event (APE) to be 1.6 and 3.4 m, respectively. The APE slip was nearly three times larger than the most recent event of 2014 (Mw 6.2): 1.2 m. This suggests that the rupture length of the APE was much longer than that of the 2014 event and the entire Kamishiro fault ruptured with adjacent faults during the APE. Thereafter, we performed the Monte Carlo simulations to explore the possible range of the coefficient of variation for slip per event (COVs). The simulation considered all the possible rupture histories in terms of the number of events and their slip amounts. The resulting COVs typically ranged between 0.3 and 0.54, indicating a large variation in the slip per event of the Kamishiro fault during the last few thousand years. To test the accuracy of our approach, we performed the same simulation to a fault whose slip per event was well constrained. The result showed that the error in the COVs estimate was less than 0.15 in 86% of realizations, which was comparable to the uncertainty in COVs derived from a paleoseismic trenching. Based on the accuracy test, we conclude that the Monte Carlo-based approach should help assess the regularity of earthquakes using an incomplete paleoseismic record.

scholarly journals Evaluating variability in coseismic slips of paleo-earthquakes from an incomplete slip history: an example from displaced terrace flights across the Kamishiro fault, central Japan

2020 ◽  
Author(s):  
Naoya Takahashi ◽  
Shinji Toda
Keyword(s):  
Monte Carlo ◽  
Three Dimensional ◽  
Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard Assessment ◽  
Reverse Fault ◽  
Central Japan ◽  
Systematic Analysis ◽  
Fluvial Terraces ◽  
Rupture Length ◽  
Slip History

Abstract Examining the regularity in slip over seismic cycles leads to an understanding of earthquake recurrence and provides the basis for probabilistic seismic hazard assessment. Systematic analysis of three-dimensional paleoseismic trenches and analysis of offset markers along faults reveal slip history. Flights of displaced terraces have also been used to study slips of paleoearthquakes when the number of earthquakes contributing to the observed displacement of a terrace is known. This study presents a Monte Carlo-based approach to estimating slip variability using displaced terraces when a detailed paleoseismic record is not available. First, we mapped fluvial terraces across the Kamishiro fault, which is an intra-plate reverse fault in central Japan, and systematically measured the cumulative dip slip of the mapped terraces. By combining these measurements with the age of the paleoearthquakes, we estimated the amount of dip slip for the penultimate event (PE) and antepenultimate event (APE) to be 1.6 and 3.4 m, respectively. The APE slip was nearly three times larger than the most recent event of 2014 (Mw 6.2): 1.2 m. This suggests that the rupture length of the APE was much longer than that of the 2014 event and the entire Kamishiro fault ruptured with adjacent faults during the APE. Thereafter, we performed the Monte Carlo simulations to explore the possible range of the coefficient of variation for slip per event (COVs). The simulation considered all the possible rupture histories in terms of the number of events and their slip amounts. The resulting COVs typically ranged between 0.3 and 0.54, indicating a large variation in the slip per event of the Kamishiro fault during the last few thousand years. To test the accuracy of our approach, we performed the same simulation to a fault whose slip per event was well constrained. The result showed that the error in the COVs estimate was less than 0.15 in 86 % of realizations, which was comparable to the uncertainty in COVs derived from a paleoseismic trenching. Based on the accuracy test, we conclude that the Monte Carlo-based approach should help assess the regularity of earthquakes using an incomplete paleoseismic record.

scholarly journals Evaluating variability in coseismic slips of paleo-earthquakes from an incomplete slip history: an example from displaced terrace flights across the Kamishiro fault, central Japan

2021 ◽  
Author(s):  
Naoya Takahashi ◽  
Shinji Toda
Keyword(s):  
Monte Carlo ◽  
Three Dimensional ◽  
Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard Assessment ◽  
Reverse Fault ◽  
Central Japan ◽  
Systematic Analysis ◽  
Fluvial Terraces ◽  
Rupture Length ◽  
Slip History

Abstract Examining the regularity in slip over seismic cycles leads to an understanding of earthquake recurrence and provides the basis for probabilistic seismic hazard assessment. Systematic analysis of three-dimensional paleoseismic trenches and analysis of offset markers along faults reveal slip history. Flights of displaced terraces have also been used to study slips of paleoearthquakes when the number of earthquakes contributing to the observed displacement of a terrace is known. This study presents a Monte Carlo-based approach to estimating slip variability using displaced terraces when a detailed paleoseismic record is not available. First, we mapped fluvial terraces across the Kamishiro fault, which is an intra-plate reverse fault in central Japan, and systematically measured the cumulative dip slip of the mapped terraces. By combining these measurements with the age of the paleoearthquakes, we estimated the amount of dip slip for the penultimate event (PE) and antepenultimate event (APE) to be 1.6 and 3.4 m, respectively. The APE slip was nearly three times larger than the most recent event of 2014 (Mw 6.2): 1.2 m. This suggests that the rupture length of the APE was much longer than that of the 2014 event and the entire Kamishiro fault ruptured with adjacent faults during the APE. Thereafter, we performed the Monte Carlo simulations to explore the possible range of the coefficient of variation for slip per event (COVs). The simulation considered all the possible rupture histories in terms of the number of events and their slip amounts. The resulting COVs typically ranged between 0.3 and 0.54, indicating a large variation in the slip per event of the Kamishiro fault during the last few thousand years. To test the accuracy of our approach, we performed the same simulation to a fault whose slip per event was well constrained. The result showed that the error in the COVs estimate was less than 0.15 in 86 % of realizations, which was comparable to the uncertainty in COVs derived from a paleoseismic trenching. Based on the accuracy test, we conclude that the Monte Carlo-based approach should help assess the regularity of earthquakes using an incomplete paleoseismic record.

scholarly journals The use of Monte Carlo simulations for seismic hazard assessment in the U.K.

2000 ◽  
Vol 43 (1) ◽  
Author(s):  
R. M. W. Musson
Keyword(s):  
Monte Carlo ◽  
Seismic Hazard ◽  
Hazard Assessment ◽  
Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard Assessment ◽  
Logic Tree ◽  
The United Kingdom ◽  
The Monte Carlo Method ◽  
Moderate Seismicity ◽  
Seismicity Model

The input required for a seismic hazard study using conventional Probabilistic Seismic Hazard assessment (PSHA) methods can also be used for probabilistic analysis of hazard using Monte Carlo simulation methods. This technique is very flexible, and seems to be under-represented in the literature. It is very easy to modify the form of the seismicity model used, for example, to introduce non-Poissonian behaviour, without extensive reprogramming. Uncertainty in input parameters can also be modelled very flexibly - for example, by the use of a standard deviation rather than by the discrete branches of a logic tree. In addition (and this advantage is perhaps not as trivial as it may sound) the simplicity of the method means that its principles can be grasped by the layman, which is useful when results have to be explained to people outside the seismological/engineering communities, such as planners and politicians. In this paper, some examples of the Monte Carlo method in action are shown in the context of a low to moderate seismicity area: the United Kingdom.

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.

scholarly journals Methodology for earthquake rupture rate estimates of fault networks: example for the western Corinth rift, Greece

2017 ◽  
Vol 17 (10) ◽  
pp. 1857-1869 ◽  
Author(s):  
Thomas Chartier ◽  
Oona Scotti ◽  
Hélène Lyon-Caen ◽  
Aurélien Boiselet
Keyword(s):  
Active Faults ◽  
Seismic Hazard Assessment ◽  
System Level ◽  
Fault System ◽  
Normal Faults ◽  
Accurate Estimation ◽  
Probabilistic Seismic Hazard Assessment ◽  
Earthquake Catalog ◽  
Earthquake Rupture ◽  
Multiple Faults

Abstract. Modeling 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 Uniform California Earthquake Rupture Forecast version 3 (UCERF-3) model 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 along fault networks is often not well constrained. There is therefore a need to propose a methodology relying on geological information alone to compute earthquake rates of the faults in the network. In the proposed methodology, a simple distance criteria is used to define FtF ruptures and consider single faults or FtF ruptures as an aleatory uncertainty, similarly to UCERF-3. 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 a priori chosen 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 modeled earthquake rates are then compared to the available independent data (geodetical, seismological and paleoseismological data) in order to weight different hypothesis explored in a logic tree.The methodology is tested on the western Corinth rift (WCR), Greece, 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−1 north–south extension. Modeling results show that geological, seismological and paleoseismological rates of earthquakes cannot be reconciled with only single-fault-rupture scenarios and require hypothesizing a large spectrum of possible FtF rupture sets. In order to fit the imposed regional Gutenberg–Richter (GR) MFD target, some of the slip along certain faults needs to be accommodated either with interseismic creep or as post-seismic processes. Furthermore, computed individual faults' 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 modeled earthquake rupture rates with those deduced from the regional and local earthquake catalog statistics and local paleoseismological data indicates a better fit with the FtF rupture set constructed with a distance criteria based on 5 km rather than 3 km, suggesting a high connectivity of faults in the WCR fault system.

scholarly journals Comparing the best-estimate uniform hazard response spectra to the observed data from the Mw 7.3 earthquake on November 12, 2017 in the Kermanshah areas of western Iran

2019 ◽  
pp. 19-34
Author(s):  
Nadereh Amerian ◽  
Elham Shabani ◽  
Ramin Nikrouz
Keyword(s):  
Seismic Hazard ◽  
Three Dimensional ◽  
Seismic Hazard Assessment ◽  
Response Spectra ◽  
Motion Prediction ◽  
Probabilistic Seismic Hazard Assessment ◽  
Ground Motion Prediction Equations ◽  
Ground Motion Prediction ◽  
Hazard Zoning ◽  
Hazard Response

In this study, synthetic catalogs based on the Monte Carlo simulations have been produced for probabilistic seismic hazard assessment (PSHA), in the Kermanshah region, West of Iran. Resultant seismic hazard zoning maps, hazard curves and three-dimensional deaggregation of seismic hazard are provided. In order to validate the estimated peak ground accelerations (PGAs), the deduced uniform hazard response spectra (UHRS) are compared with the recorded PGAs in some stations near to the large Mw 7.3 earthquake occurred in the western part of Iran near to Iraq border on 12 November 2017. Different ground motion prediction equations are tested and the results are compared.

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