Mainshock Magnitude Research Articles

A rapid analysis of aftershock processes after a moderate magnitude earthquake with ML methods

SUMMARY Moderate magnitude earthquakes and seismic sequences frequently develop on fault systems, but whether they are linked to future major ruptures is always ambiguous. In this study, we investigated a seismic sequence that has developed within a portion of the stretching region of the Apennines in Italy where moderate to large earthquakes are likely to occur. We captured a total of 2039 aftershocks of the 2023 September 18, Mw 4.9 earthquake occurred during the first week, by using machine-learning (ML) based algorithms. Aftershocks align on two 5–7 km long parallel faults, from a length that exceeds what is expected from the main shock magnitude. The segments are ramping at about 6 km depth on closely spaced N100 striking 70 N dipping planes, at a distance of some kilometres from the main shock hypocentre. Our results indicate that even moderate magnitude events trigger seismicity on a spread set of fault segments around the main shock hypocentre, revealing processes of interaction within the crustal layer. The possibility that larger earthquakes develop during seismicity spread is favoured by pore pressure diffusion, in relation with the closeness to criticality of fault segments. Based on the very rapid activation of seismicity on the entire system and a back-front signal from the hypocentre of the main event, we infer that fluid pressure, initially high within the crustal layer, rapidly dropped after the main shock. Our study reinforces the importance of timely extracting information on fault geometry and seismicity distribution on faults. ML-based methods represent a viable tool for semi-real-time application, yielding constraints on short-time forecasts.

Forecasting fluid-injection induced seismicity to choose the best injection strategy for safety and efficiency.

Induced seismicity poses a challenge to the development of Enhanced Geothermal Systems (EGS). Improving monitoring and forecasting techniques is essential to mitigate induced seismicity and thereby fostering a positive perception of EGS projects among local authorities and population. Induced seismicity is the result of complex and coupled thermo-hydro-mechanical-chemical mechanisms. Injection flux and pressure are crucial controlling parameters for both hydraulic stimulation and circulation protocols. We develop a methodology combining a hydro-mechanical model with a seismicity rate model to estimate the magnitude and frequency of mainshocks and aftershocks induced by fluid injection. We apply the methodology to the case of the Basel EGS (2006, Switzerland) to compare the effects of progressive, cyclic and constant injections on the mechanical response of discrete faults. Results from the coupled hydro-mechanical models show that the pore pressure diffusion and consequent enhancement of fault permeability are limited to the vicinity of the injection well during cyclic injection. Additionally, constant injection induces seismicity from the start of the injection but enhances the permeability of most of the faults within a shorter duration, inducing less post-injection seismicity. The methodology can be adapted to any numerical model and allows new projects to be developed by anticipating the safest injection protocol.This article is part of the theme issue 'Induced seismicity in coupled subsurface systems'.

Statistical modeling of 3D seismicity and its correlation with fault slips along major faults in California

This study applies a 3D Epidemic Type Aftershock Sequence (ETAS) model to the earthquake catalog in California. A new depth kernel function incorporating the scaling effect of mainshock magnitudes is introduced into the model. The results demonstrate that the new model improves data fitting, and we find a consistent decrease in aftershock productivity with depth by stochastic reconstruction. We attribute this to the decreasing fault coupling with depth or active seismic faulting in the upper crust. Furthermore, we compare background seismicity rates derived from the new model with the long-term slip rates on the faults in the study region. We reveal a linear increase in the seismicity rate with the slip rate on the logarithmic scale, suggesting the accumulated strain on fault is partially released by seismic activities. Additionally, a significant correlation exists between the background seismicity rate and fault segments exhibiting relatively high creep rates, especially in the transition zones for fault coupling along the central San Andreas fault. This finding suggests that interseismic background earthquakes mostly occur in areas with moderate coupling ratios.

Seismic damage analysis of shallow buried subway station in clayey sand soil under mainshock-aftershock earthquakes

During earthquake events, a mainshock may trigger a number of following aftershock earthquakes in a short time. Usually, structures will be damaged to a certain extent by the mainshock, and aftershocks can further exacerbate the damage to structures, making post-disaster rescue and rehabilitation extremely challenging. Yet, most of research on seismic performance of underground structures only considered the single mainshock, ignoring the effect of aftershocks. In this study, a nonlinear numerical model of the shallow buried shallow subway station in clayey sand soil under mainshock-aftershock sequences was constructed to replicate the damage evolution process of underground structures. A limited numerical sensitivity analysis was performed considering the influences of the magnitude of mainshock and aftershock intensity. The results indicate that the damage of subway station is closely related to the magnitude of mainshock intensity. The aftershocks might cause more serious incremental damage to underground structures and secondary displacement of the site, potentially lead to collapse of the subway station, when the mainshock magnitude is greater. With the superposition of the mainshock and aftershock, the relative horizontal displacement of the subway station could reach the inter-story drift limit value. Therefore, the aftershock should be taken into account for seismic safety design of shallow underground structures.

Aftershock probabilistic seismic hazard analysis based on enhanced Bayesian network considering frequency information

AbstractBayesian network (BN) is an important tool in probabilistic seismic risk analysis (PSRA) due to its holistic nature and powerful probabilistic inference capabilities. However, while the information that can be stored by BN includes variable values, probability distributions, and relationships between variables, it does not involve event quantities. The results obtained from PSRA and probabilistic seismic hazard analysis (PSHA) are commonly frequency‐related (the number of occurrences per unit time), fundamentally describing event numbers. BN assumes a fixed event number relationship between nodes, but the aftershock counts vary for different mainshock magnitudes. This limitation further restricts its effectiveness in lifespan PSRA for structures. Therefore, this study aims to propose an enhanced BN (EBN) for modeling aftershock PSHA (APSHA) considering frequency information. This paper first introduces the modeling method using BN, including PSHA and a simplified model of APSHA using Båth's law. Next, an EBN that can effectively address frequency issues between the mainshock and aftershocks is presented for modeling APSHA considering the modified Omori's law, while the mathematical principles of both forward and backward inferences for the EBN are elaborated in detail. Then, the article carefully analyzes the utilization of the EBN for APSHA modeling under different scenarios where the information regarding the mainshock is known to varying extents, followed by the extension of the EBN in a time domain to obtain time‐dependent aftershock hazard. Finally, an example of APSHA in a specific location in China is illustrated.

Elevated collapse risk based on decaying aftershock hazard and damaged building fragilities

This article proposes a framework to support postearthquake building safety and reoccupancy decisions by quantifying the change in building collapse risk following a mainshock earthquake event. This risk may be exacerbated by both an increase in seismic hazard due to aftershock activity and a reduction in building collapse resistance due to structural damage. To address these factors, the framework is based on a hazard that includes (1) both the steady-state and the aftershock occurrence rates, that is, the elevated hazard that accounts for the dependence on the mainshock magnitude and the aftershock rate that decays over time, and (2) revised collapse fragility functions that account for structural damage sustained during the mainshock. The framework is capable of addressing region-specific questions such as (1) What are the mainshock magnitudes for which aftershocks pose a life-safety concern? (2) How long does it take for the elevated risk due to aftershocks to dissipate? and (3) What gaps in current knowledge deserve further attention from the earthquake engineering and seismology communities? The framework addresses these questions for a 20-story building in San Francisco, assuming three different, hypothetical mainshock events of magnitudes 7,7.5, and 8 M W on the San Andreas fault. This is followed by a parametric study that considers a range of buildings and provides a graphical representation of the elevated risk to inform building evaluation (tagging) decisions, based on the intact building’s collapse capacity, the amount of structural damage, and the length of time after the mainshock.

Time-Dependent Probabilistic Seismic Hazard Analysis for Seismic Sequences Based on Hybrid Renewal Process Models

ABSTRACT Probabilistic seismic hazard analysis (PSHA) is a methodology with a long history and has been widely implemented. However, in the conventional PSHA and sequence-based probabilistic seismic hazard analysis (SPSHA) approaches, the occurrence of mainshocks is modeled as the homogeneous Poisson process, which is unsuitable for large earthquakes. To account for the stationary occurrence of small-to-moderate (STM) mainshocks and the nonstationary behavior of large mainshocks, we propose a time-dependent sequence-based probabilistic seismic hazard analysis (TD-SPSHA) approach by combining the time-dependent mainshock probabilistic seismic hazard analysis (TD-PSHA) and aftershock probabilistic seismic hazard analysis, consisting of four components: (1) STM mainshocks, (2) aftershocks associated with STM mainshocks, (3) large mainshocks, and (4) aftershocks associated with large mainshocks. The approach incorporates an exponential-magnitude, exponential-time model for STM mainshocks, and a renewal-time, characteristic-magnitude model for large mainshocks to assess the time-dependent hazard for mainshocks. Then nonhomogeneous Poisson process is used to model the occurrence of associated aftershocks, in which the aftershock sequences can be modeled using the Reasenberg and Jones (RJ) model or the epidemic-type aftershock sequence (ETAS) model. To demonstrate the proposed TD-SPSHA approach, a representative site of the San Andreas fault is selected as a benchmark case, for which five time-dependent recurrence models, including normal, lognormal, gamma, Weibull, and Brownian passage time (BPT) distributions, are chosen to determine the occurrence of large mainshocks. Then sensitivity tests are presented to show the effects on TD-SPSHA, including (1) time-dependent recurrence models, (2) mainshock magnitude, (3) rupture distance, (4) aftershock duration, (5) escaped time since the last event, and (6) future time interval. Furthermore, the bimodal hybrid renewal model is utilized by TD-SPSHA for another case site. The comparison results illustrate that the sequence hazard analysis approach ignoring time-varying properties of large earthquakes for long periods and the effects of associated aftershocks will result in a significantly underestimated hazard. The TD-SPSHA-based hazard curves using the ETAS model are larger than those of the RJ model. The proposed TD-SPSHA approach may be of significant interest to the field of earthquake engineering, particularly in the context of structural design or seismic risk analysis for the long term.

A New Statistical Perspective on Båth’s Law

Abstract The empirical Båth’s law states that the average magnitude difference (ΔM) between a mainshock and its strongest aftershock is ∼1.2, independent of the size of the mainshock. Although this observation can generally be explained by a scaling of aftershock productivity with mainshock magnitude in combination with a Gutenberg–Richter frequency–magnitude distribution, estimates of ΔM may be preferable because they are directly related to the most interesting information, namely the magnitudes of the main events, without relying on assumptions. However, a major challenge in calculating this value is the bias introduced by missing data points when the strongest aftershock is below the observed cut-off magnitude. Ignoring missing values leads to a systematic error because the data points removed are those with particularly large magnitude differences ΔM. The error can be minimized by restricting the statistics to mainshocks that are at least 2 magnitude units above the cutoff, but then the sample size is strongly reduced. This work provides an innovative approach for modeling ΔM by adapting methods for time-to-event data, which often suffer from incomplete observations (censoring). In doing so, we adequately account for unobserved values and estimate a fully parametric distribution of the magnitude differences ΔM for mainshocks in a global earthquake catalog. Our results suggest that magnitude differences are best modeled by the Gompertz distribution and that larger ΔM are expected at increasing depths and higher heat flows.

Predicting the Future Performance of the Planned Seismic Network in Chinese Mainland

Abstract The China Earthquake Administration has currently launched an ambitious nationwide seismicity monitoring network project that will increase the number of stations from ∼950 to 2000 for the broadband seismic stations used to compile the earthquake catalog. The new network is planned to go online by the end of 2023. For more than half of Chinese mainland, the interstation distance of the broadband seismic network will soon be smaller than 100 km, for 27% smaller than 50 km, and for 6% smaller than 25 km. Of all possible ways to characterize the higher-resolution monitoring of the frequent smaller earthquakes expected inside Chinese mainland, the completeness magnitude (Mc) remains one of the most commonly used. Using the prior model of the Bayesian magnitude of completeness method calibrated on the Chinese earthquake catalog from 1 January 2009 to 26 June 2022, we predict the spatial distribution of Mc for the new network based on the planned network configuration. If almost the entire Chinese mainland is at present covered down to Mc=3.3, this threshold will fall to Mc=2.9 in the near future. This means approximately two times more earthquakes will be recorded in the complete catalog available for statistical analysis per year (for a = 6.77 and b = 0.80 in the Gutenberg–Richter law log10N=a−b·M, in which N represents the number of events of magnitude larger than or equal to M and M≥Mc). Based on the observation that abnormal seismicity as precursors are most likely to be observed at least at three units below the mainshock magnitude, and assuming earthquakes to be potentially damaging at M ≥ 5, the new seismic network shall achieve the goal of 76% coverage for optimal seismic-based earthquake prediction research.

Global Characteristics of Observable Foreshocks for Large Earthquakes

AbstractForeshocks are the only currently widely identified precursory seismic behavior, yet their utility and even identifiability are problematic, in part because of extreme variation in behavior. Here, we establish some global trends that help identify the expected frequency of foreshocks as well the type of earthquake most prone to foreshocks. We establish these tendencies using the global earthquake catalog of the U.S. Geological Survey National Earthquake Information Center with a completeness level of magnitude 5 and mainshocks with Mw≥7.0. Foreshocks are identified using three clustering algorithms to address the challenge of distinguishing foreshocks from background activity. The methods give a range of 15%–43% of large mainshocks having at least one foreshock but a narrower range of 13%–26% having at least one foreshock with magnitude within two units of the mainshock magnitude. These observed global foreshock rates are similar to regional values for a completeness level of magnitude 3 using the same detection conditions. The foreshock sequences have distinctive characteristics with the global composite population b-values being lower for foreshocks than for aftershocks, an attribute that is also manifested in synthetic catalogs computed by epidemic-type aftershock sequences, which intrinsically involves only cascading processes. Focal mechanism similarity of foreshocks relative to mainshocks is more pronounced than for aftershocks. Despite these distinguishing characteristics of foreshock sequences, the conditions that promote high foreshock productivity are similar to those that promote high aftershock productivity. For instance, a modestly higher percentage of interplate mainshocks have foreshocks than intraplate mainshocks, and reverse faulting events slightly more commonly have foreshocks than normal or strike-slip-faulting mainshocks. The western circum-Pacific is prone to having slightly more foreshock activity than the eastern circum-Pacific.

Cluster-based foreshock discrimination model with flexible time horizon and mainshock magnitudes

Foreshock detection before mainshock occurrence is an important challenge limiting the short-term forecasts of large earthquakes. Various models for predicting mainshocks based on discrimination of foreshocks activity have been proposed, but many of them work in restricted scenarios and neglect foreshocks and mainshocks out of their scope. In disaster prevention, it is often necessary to change the forecast period and the magnitude of target mainshocks. This paper presents a cluster-based statistical discrimination of foreshocks which is applicable all over Japan and adjustable with respect to forecasting time span and mainshock magnitudes. Using the single-link clustering method, the model updates the expanding seismic clusters and determines in real time the probabilities that larger subsequent events will occur. The foreshock clusters and the others show different trends of certain feature statistics with respect to their magnitudes and spatiotemporal distances. Based on those features and the epicentral location, a nonlinear logistic regression model is used to evaluate the probabilities that growing seismic clusters are foreshocks that will trigger mainshocks within 30 days. The log of odds is estimated between the foreshock clusters and other clusters for respective feature values as nonlinear spline functions from a Japanese hypocenter catalog for the period 1926–1999. Based on the estimated odds functions, foreshock clusters tend to have smaller differences in their two largest magnitudes, shorter time durations, and slightly longer epicentral distances within the individual clusters. Given a potential foreshock cluster, its mainshock magnitude can be predicted by the Gutenberg–Richter law over the largest foreshock magnitude. The timing of mainshock occurrences from foreshocks is also predicted by multiplying the portion of mainshocks within a shorter span from those within 30 days by the evaluated foreshock probabilities. The predictive performance of our model is validated by the holdout method using a Japanese hypocenter catalog before and after 2000. The evaluated foreshock probabilities are roughly consistent with the actual portion of foreshocks in the validation catalog and could serve as an alert for large mainshocks.

New Physical Implications From Revisiting Foreshock Activity in Southern California

AbstractForeshock analysis promises new insights into the earthquake nucleation process and could potentially improve earthquake forecasting. Well‐performing clustering models like the Epidemic‐Type Aftershock Sequence (ETAS) model assume that foreshocks and general seismicity are generated by the same physical process, implying that foreshocks can be identified only in retrospect. However, several studies have recently found higher foreshock activity than predicted by ETAS. Here, we revisit the foreshock activity in southern California using different statistical methods and find anomalous foreshock sequences, that is, those unexplained by ETAS, mostly for mainshock magnitudes below 5.5. The spatial distribution of these anomalies reveals a preferential occurrence in zones of high heat flow, which are known to host swarm‐like seismicity. Outside these zones, the foreshocks generally behave as expected by ETAS. These findings show that anomalous foreshock sequences in southern California do not indicate a pre‐slip nucleation process, but swarm‐like behavior driven by heat flow.

Regional Characteristics of Observable Foreshocks

Abstract Measures of foreshock occurrence are systematically examined using earthquake catalogs for eight regions (Italy, southern California, northern California, Costa Rica, Onshore Japan, Alaska, Turkey, and Greece) after imposing a magnitude ≥3.0 completeness level. Foreshocks are identified using three approaches: a magnitude-dependent space + fixed-time windowing method, a nearest-neighbor clustering method, and a modified magnitude-dependent space + variable-time windowing method. The method with fixed-time windows systematically yields higher counts of foreshocks than the other two clustering methods. We find similar counts of foreshocks across the three methods when the magnitude aperture is equalized by including only earthquakes in the magnitude range M*−2≤ M< M*, in which M* is the mainshock magnitude. For most of the catalogs (excluding Italy and southern California), the measured b-values of the foreshocks of all region-specific mainshocks are lower by 0.1–0.2 than b-values of respective aftershocks. Allowing for variable-time windows results in relatively high probabilities of having at least one foreshock in Italy (∼43%–56%), compared to other regional catalogs. Foreshock probabilities decrease to 14%–41% for regions such as Turkey, Greece, and Costa Rica. Similar trends are found when requiring at least five foreshocks in a sequence to be considered. Estimates of foreshock probabilities for each mainshock are method dependent; however, consistent regional trends exist regardless of method, with regions such as Italy and southern California producing more observable foreshocks than Turkey and Greece. Some regions with relatively high background seismicity have comparatively low probabilities of detectable foreshock activity when using methods that account for variable background, possibly due to depletion of near-failure fault conditions by background activity.

A Short Note on the Aftershock Duration of Strong to Major Himalayan Earthquakes

Abstract Earthquakes of M ≥ 5 tend to be locally damaging, specifically when these are the aftershocks of larger earthquakes, as the main shock would have weakened the structures. For the rescue operations and general well-being of the local residents, it is helpful if an estimate is available as to how long M ≥ 5 aftershocks would continue to occur. Earthquakes M ≥ 6.5 tend to be followed by aftershocks of M ≥ 5. In this study, aftershock sequences of seven earthquakes of magnitude M ≥ 6.5 were analyzed. Six among these are in the Himalayan region and the remaining one is in the near vicinity in China. The analysis suggests that the number of M ≥ 5 aftershocks and the duration of their occurrence decrease with the decrease of the mainshock magnitude. For the 2008 Sichuan earthquake of M 7.9 there were 136 M ≥ 5 aftershocks, while for 1975 Kinnaur earthquake of M 6.8 there were only 9. The aftershock duration of the Himalayan region earthquakes obeys the exponential law T = AecM, where the A and c are constants associated with regional fault settings. This relation is helpful in providing an estimate of the time for which M ≥ 5 aftershock activity would continue after the occurrence of a M ≥ 6.5 earthquakes.

Aftershock Moment Tensor Scattering

AbstractCoseismic rotations of principal stress axes can provide insights into the strength of the crust, but it is unclear how common this phenomenon is. We use a nearest‐neighbor clustering algorithm to identify earthquake sequences in the global ISC‐GEM catalog and the regional Southern California catalog. Using an inner‐product‐based pairwise measure of moment tensor similarity, we demonstrate that, in both catalogs, aftershocks are less similar to their respective mainshocks than foreshocks are. We interpret this effect, which we call moment tensor scattering, as evidence for widespread coseismic stress rotations. Moment tensor scattering is observable for a broad range of mainshock magnitudes in both catalogs. We further demonstrate that mainshock‐aftershock similarity recovers logarithmically to pre‐mainshock levels on decadal timescales. We conclude that moment tensor scattering is a generally observable feature of seismic sequences which may be useful in future work to discriminate between models of crustal strength.

Characteristics of the foreshock occurrence for Mj3.0 to 7.2 shallow onshore earthquakes in Japan

We use the Japan Meteorological Agency (JMA) earthquake catalogue from January, 2001 to February, 2021 to investigate the spatiotemporal foreshock occurrence for shallow (within 30 km depth) onshore earthquakes (Mj3.0 to 7.2). We find clear peaks for the numbers of small earthquakes within 10 days and 3 km prior to the larger earthquakes, which are considered as our definition of foreshocks. After removing the aftershocks, earthquake swarms and possible triggered earthquakes by the 2011 Mw9.0 Tohoku-oki earthquake, we find that for the 2066 earthquakes (mainshocks), 783 (38%) have one or more foreshocks. There is a decreasing trend of foreshock occurrence rate with mainshock depth. Also, normal faulting earthquakes have higher foreshock occurrence rate than reverse faulting earthquakes. We calculate the earthquake occurrence rate as a function of the magnitudes of foreshocks and mainshocks, and we have found no clear trend between the magnitudes of foreshocks and mainshocks.Graphical

Space–Time Trade-Off of Precursory Seismicity in New Zealand and California Revealed by a Medium-Term Earthquake Forecasting Model

The ‘Every Earthquake a Precursor According to Scale’ (EEPAS) medium-term earthquake forecasting model is based on the precursory scale increase (Ψ) phenomenon and associated scaling relations, in which the precursor magnitude MP is predictive of the mainshock magnitude Mm, precursor time TP and precursory area AP. In early studies of Ψ, a relatively low correlation between TP and AP suggested the possibility of a trade-off between time and area as a second-order effect. Here, we investigate the trade-off by means of the EEPAS model. Existing versions of EEPAS in New Zealand and California forecast target earthquakes of magnitudes M > 4.95 from input catalogues with M > 2.95. We systematically vary one parameter each from the EEPAS distributions for time and location, thereby varying the temporal and spatial scales of these distributions by two orders of magnitude. As one of these parameters is varied, the other is refitted to a 20-year period of each catalogue. The resulting curves of the temporal scaling factor against the spatial scaling factor are consistent with an even trade-off between time and area, given the limited temporal and spatial extent of the input catalogue. Hybrid models are formed by mixing several EEPAS models, with parameter sets chosen from points on the trade-off line. These are tested against the original fitted EEPAS models on a subsequent period of the New Zealand catalogue. The resulting information gains suggest that the space–time trade-off can be exploited to improve forecasting.

Immediate Foreshocks Indicating Cascading Rupture Developments for 527 M 0.9 to 5.4 Ridgecrest Earthquakes

AbstractUnderstanding earthquake foreshocks is essential for deciphering earthquake rupture physics and can aid seismic hazard mitigation. With regional dense seismic arrays, we identify immediate foreshocks of 527 0.9 M 5.4 events of the 2019 Ridgecrest earthquake sequence, including 48 earthquakes with series of immediate foreshocks. These immediate foreshocks are adjacent to the mainshocks occurring within 100 s of the mainshocks, and their P waves share high resemblances with the mainshock P waves. However, attributes of the immediate‐foreshock P waves, including the amplitudes and preceding times, do not clearly scale with the mainshock magnitudes. Our observations suggest that earthquake rupture may initiate in a universal fashion but evolves stochastically. This indicates that earthquake rupture development is likely controlled by fine‐scale fault heterogeneities in the Ridgecrest fault system, and the final magnitude is the only difference between small and large earthquakes.

Possible Precursory Slow‐Slip to Two ML∼3 Mainevents of the Diemtigen Microearthquake Sequence, Switzerland

AbstractHow earthquakes initiate is still a largely debated question in earthquake science. On the lab scale, rupture initiation is well studied, and detailed models of how rupture nucleation evolves have been developed. Contrarily, for real earthquakes, only a few high‐resolution observations of this process are available today, mostly limited to mainshock magnitudes > M5. Consequently, there is still no consensus on whether and how laboratory results can be transferred to real earthquakes. Here we show that rupture nucleation phenomena observed on the lab scale can also be imaged on the microearthquake‐scale with little instrumental effort. Our results highlight the potential of the applied analysis workflow to significantly improve the observation quality of seismicity patterns and immediate foreshock phenomena in microearthquake sequences. Our approach can help to narrow the existing observational gap to the lab scale and may contribute to a better understanding of the mechanisms of earthquake initiation in the future.

Behavior factor prediction equations for reinforced concrete frames under critical mainshock-aftershock sequences using artificial neural networks

ABSTRACT This paper proposes the ductility demands control of reinforced concrete frames under criticalsuccessive earthquakes using evaluation of behavior factors (R factors). The influence of RC frameperiods, PGA and magnitude of mainshocks and aftershocks is also taken into account by 10 training ideal artificial neural network (ANN) and proposing the empirical equations. Firstly, 2D RC frames are implemented in Opensees and then evaluated under as-recorded critical single and successive scenario. R factors are calculated and compared for single and successive cases. It is found that the sequences of critical records decrease R factors and capacity of RC frames about 18% and 30%, respectively. Despite what is necessitated in the seismic design codes, proposing a constant value as R factor for whole RC structure especially under single scenarios cannot lead to proper design of structures. Hence, the idealized multilayer ANNs employed to generate the empirical charts for evaluation of R factors.