Magnitude Of Future Earthquakes Research Articles

Coseismic deformation and multi-fault slip model of the 2019 Mindanao earthquake sequence derived from Sentinel-1 and ALOS-2 data

From October to December 2019, a sequence of four earthquakes of Mw > 6.0 occurred in southern Mindanao, the Philippines, and revealed complex tectonics in this region. We used Advanced Land Observing Satellite (ALOS)-2 and Sentinel-1A/B Synthetic Aperture Radar (SAR) data to map the coseismic deformation and to constrain both the fault geometry and kinematics of coseismic slip distributions during the four earthquakes. Our observed coseismic deformation field shows that these four earthquakes ruptured two intersected conjugate faults with NE and NW strikes. Based on ascending and descending Interferometric SAR (InSAR) data, we constructed elastic half-space models to search for the optimal fault dip angle and inverted the slip distributions of the four earthquakes. The results show that these four earthquakes were all dominated by left- and right-lateral strike-slip motion. The two conjugate faults clearly had significant differences in terms of slip behaviour and fault kinematics. The static Coulomb stress change indicates that earlier earthquakes had a significant triggering effect on subsequent earthquakes. The static Coulomb stress change induced by the four earthquakes suggests a significant stress loading effect on NW-trending faults. The results of this study show that the potential for future earthquakes on NW-trending faults cannot be ignored; however the magnitudes of future earthquakes should be limited by complex fault geometry and segmentation.

Earthquake hazard estimation for road tunnel in Northwest Himalayas

Seismic hazard assessment of earthquake prone terrain is estimated in numerous ways for civil underground structures such as tunnels which receives little attention on the seismic zones of the country. The resemblance of the past behaviour of earthquake is seen in the present seismotectonic block, and this is considered for this study. With this, the magnitudes of future earthquakes and its effects are predicted with Matlab software. In order to emphasize the need for carrying out a detailed Seismic Hazard analysis in underground openings, a proposed communication (road) tunnel project located in Kashmir Himalayas (GPS coordinates of Latitude 32.20° to 37.20° N, Longitude 72.50° to 80.50° E) one of the highest seismic zones of the Country (zone-V, BIS-2002) was taken up and the results reported in the paper. The paper incidentally has brought to light the need for carrying out such detailed seismic analyses in a routine manner for underground structures to be constructed in the country particularly in higher seismic zones, besides adumbrating structural support measures required for the various ground classes in the proposed road tunnel at Kashmir in response to seismic loading and also recommending retrofitting for other structures already in existence. A spin off the study is expected to be in the area of refining seismic zonation of the country and micro-zonation studies that are slated for the future.

Earthquake Risk Analysis and Qualitative Comparison of Attenuation Relationships in Garmsar City, Iran

Despite the scientists’ wide efforts to determine earthquake risks all around the world, it is not still possible to predict the exact time, location and magnitude of future earthquakes and aftershocks at the ground surface so precise results are not predictable within near future. The most significant reason for this relates to numerous complexities of earthquake mechanism and causal conditions and waves through different ground layers with completely different properties. Logical tree method was used with weights to determine acceleration spectra due to spectral nature of region. Probabilistic analysis of earthquake hazard was done using SEISRISK III program. The analysis results are proposed through spectral acceleration maps for 50 years in Garmsar. Moreover, uniform hazard spectrum and spectrum with constant shape are presented.

Artificial neural networks (ANN) and stochastic techniques to estimate earthquake occurrences in Northeast region of India

The paper presents the probability of earthquake occurrences and forecasting of earthquake magnitudes size in northeast India, using four stochastic models (Gamma, Lognormal, Weilbull and Log-logistic) and artificial neural networks, respectively considering updated earthquake catalogue of magnitude Mw ≥ 6.0 that occurred from year 1737 to 2015 in the study area. On the basis of past seismicity of the region, the conditional probabilities for the identified seismic source zones (12 sources) have been estimated using their best fit model and respective model parameters for various combinations of elapsed time (T) and time interval (t). It is observed that for elapsed time T=0 years, EBT & Kabaw zone shows highest conditional probability and it reaches 0.7 to 0.91 after about small time interval of 3-6 years (2014-2017; since last earthquake of Mw ≥ 6.0 occurred in the year 2011) for an earthquake magnitude Mw ≥ 6.0.Whereas, Sylhet zone shows lowest value of conditional probability among all twelve seismic source zones and it reaches 0.7 after about large time interval of 48 years (year 2045, since last event of Mw ≥ 6.0 occurred in the year 1999). While for elapsed time up to 2016 from the occurrence of the last earthquake of magnitude Mw ≥ 6.0, the MBT & MCT region shows highest conditional probability among all twelve seismic source zones and it reaches 0.88 to 0.91 after about 6-7 (2022-2023) years and in the same year (2022-2023) Sylhet zone shows lowest conditional probability and it reaches 0.14-0.17. However, we proposed Artificial Neural Network (ANN) technique used to predict the possible magnitude of future earthquake in the identified seismic source zones is based on feedforward backpropagation neural network model with single hidden layer. For conditional probability of earthquake occurrence above 0.8, the neural network gives the magnitude of future earthquake as Mw 6.6 in Churachandpur-Mao fault (CMF) region in the years 2014 to 2017 and for Myanmar Central Basin (MCB) region it gives magnitude of future earthquake as Mw 7.0 in the years 2013 to 2016 and for Eastern Boundary Thrust (EBT) & Kabaw region it gives magnitude of future earthquake as Mw 6.4 in the years 2015-2018. The epicentre of recently occurred 4 January 2016 Manipur earthquake (M 6.7), 13 April 2016 Myanmar earthquake (M 6.9) and the 24 August 2016 Myanmar earthquake (M 6.8) are located in Churachandpur-Mao fault (CMF) region Myanmar Central Basin (MCB) region and EBT & Kabaw region, respectively and that are the identified seismic source zones in the study area which show that the ANN model yields good prediction accuracy.

Near‐prospective test of Coulomb stress triggering

AbstractNumerous studies retrospectively observed a strong association between earthquake location and increased static Coulomb stress. In addition to confirming these results for southern California seismicity, we observed prospective forecasting potential in static stress evolution. With 141 seismic and 98 aseismic stress sources, we considered alternate choices of stress components and receiver fault orientations, examined the effect of Coulomb triggering on earthquake magnitude, calculated stress histories for receiver quakes to see if some occurred after their stress had peaked, examined whether stress changes from the Hector Mine earthquake alone changed the earthquake rate as expected, and estimated the conditional distribution of earthquake occurrence given resolved Coulomb stress change. We found that with 95% confidence, M ≥ 2.8 receiver earthquakes nucleate in areas of shear or Coulomb stress change increase. On average, 59% of earthquakes occurred within stress‐enhanced zones, regardless of the choice of rupture plane or type of stress change. The 1999 Hector Mine, California, earthquake increased the seismicity in regions of positive and negative stress change but more so in the positive regions. Earthquakes frequently occur after their calculated peak stress has occurred, indicating that elastic calculations do not tell the whole story. We found no significant evidence that stress change affects the magnitude of receiver quakes. Thus, instantaneous Coulomb and shear stress change apparently influence the locations but not the magnitudes of future earthquakes.

Recent Efforts in Earthquake Prediction (1990–2007)

From an emergency-management and hazard-preparedness perspective, long-term seismic risk analysis of a region is of utmost importance. There have been a good number of efforts during the past 15 years or so in earthquake prediction, and this paper is an attempt to present a state-of-the-art review of the subject. The most significant recent efforts in predicting the three earthquake parameters, namely, the time of occurrence, epicentral location, and the magnitude of future earthquakes are reviewed. Prediction studies can be broadly grouped based on the basic approach, which vary from purely theoretical geophysics, to genetic mutations and biology, to statistical, mathematical, and computational modeling of earthquake parameter data recorded in historical catalogs of seismic regions. The papers reviewed in this article are classified into two groups: (1) studies based on recording and analyzing earthquake precursors (seismic monitoring); and (2) studies based on historic earthquake data analysis. The complexity of the earthquake prediction problem notwithstanding, the authors believe that the scientific community should pursue research on the subject vigorously. It is hoped that this article fuels additional interest in the subject.

Seismic hazard analysis in low and moderate seismic region-Korean peninsula

In low and moderate seismic regions, seismic activities have not been well defined. Unexpected large future earthquakes might occur in these regions, and structures can be severely damaged and collapsed since most structures in these regions were designed by considering only gravity loads. The objective of this study is to construct a uniform hazard response spectrum (UHRS) and to generate synthetic uniform hazard ground motions at a site with low and moderate seismicity for evaluating seismic performance of structures located at the site. The Seoul city hall was chosen as a site to simulate ground motions and construct a UHRS. To achieve this objective, this study simulates the epicenters and magnitudes of future earthquakes within 50,000 years based on those of past earthquakes recorded during the last 614 years. This study assumes that the site is affected only by earthquakes that occur within 100 km from the site. For 50,000 years, 36,645 earthquakes occur on the Korean peninsula, of which 4288 occur within 100 km of the selected site. Thus, 4288 ground motions are generated at the site considering earthquake attenuation and soil profiles at the site. Then uniform hazard response spectra (UHRS) are constructed at the site for 10% and 2% probabilities of exceedance over the next 50 years. This study also selects 10 ground motions for a response history analysis of structures, which best fit the UHRS.

Forecasting rupture dimension using the pattern informatics technique

The Pattern Informatics (PI) technique [Tiampo, K.F., Rundle, J.B., McGinnis, S., Gross, S., Klein, W., 2002. Mean-field threshold systems and phase dynamics: An application to earthquake fault systems, Europhys. Lett., 60, 481–487] is founded on the premise that changes in the seismicity rate are a proxy for changes in the underlying stress. This new approach to the study of seismicity quantifies its local and regional space–time patterns and identifies regions of local quiescence or activation. Here we use a modification of the PI method to quantify localized changes surrounding the epicenters of large earthquakes in California in an attempt to objectively quantify the rupture zones of these upcoming events. We show that this method can be used to forecast the size and magnitude of future earthquakes.

Developing stress-monitoring sites using cross-hole seismology to stress-forecast the times and magnitudes of future earthquakes

A new understanding of rockmass deformation suggests that changing stress in the crust modifies the geometry of the distributions of fluid-saturated grain-boundary cracks and pores pervading almost all rocks in the crust. These stress-aligned micro cracks cause the widely observed splitting of seismic shear-waves, which are sensitive to the details of the microcrack geometry. This means that analysing shear-wave splitting along appropriate ray paths above small earthquakes can monitor the build up of stress before large earthquakes. This allowed the time and magnitude of an M=5 earthquake in Iceland to be successfully ‘stress-forecast’. Such forecasting, using small earthquakes as the source of shear-waves, is possible only on those rare occasions when the comparatively severe restrictions on the geometry of source, receiver, and large earthquake, allow shear-wave splitting to be analysed along appropriate ray paths. This paper suggests that in the absence of such pronounced local seismicity and optimum recording geometry, the time and magnitude of future earthquakes can be estimated by analysing shear-wave splitting in controlled-source cross-well seismology between three boreholes. We suggest that stress-forecasting at such stress-monitoring sites (SMSs) is the best deterministic option for reliable forewarning of large earthquakes near any earthquake-vulnerable township, or vibration-sensitive installation. A preliminary stress-monitoring site is currently being set up in Northern Iceland.

Earthquakes Cannot Be Predicted

Can the time, location, and magnitude of future earthquakes be predicted reliably and accurately? In their Perspective, Geller et al .'s answer is “no.” Citing recent results from the physics of nonlinear systems “chaos theory,” they argue that any small earthquake has some chance of cascading into a large event. According to research cited by the authors, whether or not this happens depends on unmeasurably fine details of conditions in Earth's interior. Earthquakes are therefore inherently unpredictable. Geller et al . suggest that controversy over prediction lingers because prediction claims are not stated as objectively testable scientific hypotheses, and due to overly optimistic reports in the mass media.

Discussion on uncertainties, attenuation of ground motion and aseismic design criterion

The usually calculated exceedance probability curves of ground motion are reduced as cumulative probability curves of normal distribution on some assumptions in this paper. These curves clearly displayed the variation of curve shape with the variance of attenuation relation and its physical implication. Similar investigation is also made on uncertainties of hypocenter locations and magnitudes of future earthquakes. The larger the uncertainty, the flatter the exceedance probability curve is. In a broad sense, the less people know future earthquakes, the flatter is the curve. Due to the rich or poor data sets available, the uncertainties of attenuation relation are different from region to region. The acceleration attenuation relations in these regions with no enough strong earthquake records can be obtained by conversion from other region, but with larger uncertainty. The uncertainty contains systematic difference between the two regions in addition to common stochastic error. A method to check and adjust the converted attenuation relation by using the local data is proposed in this paper. If the uncertainty of attenuation relation is too large, the result of seismic hazard assessment may be unaccepted sometimes. In order to realize that the structures do not collapse in large earthquakes, be repairable under moderate ones and without destruction in small earthquakes, this paper suggests that it may be reasonable to get the first and the third levels of aseismic design parameters by some empirical relation on the basis of the second level not by fixing the risk probability levels (63%, 10% and 3%). A particular aseismic design criterion is not only a balance between economic cost and seismic risk but also suited to the human’s knowledge of nature.

Cautious neotectonic hypotheses for assessing the seismic hazard in northeastern Italy

A simplified tectonic scheme for hazard purposes was recently adopted for northeastern Italy, introducing large generalized seismogenic areas containing systems of complex geometry faults. This scheme considers only major faults with documented seismic activity. In the present analysis, a different tectonic scheme, with linear elements as seismogenic sources, is presented. The assessment of the regional seismic hazard is done with the fault rupture model, its most important advantage being the recognition that the length of fault rupture during an earthquake is an important consideration in probabilistic calculations of seismic hazard. Moreover, some structures with no associated seismicity but with notable neotectonic activity are considered, and their contribution to the results investigated. Important uncertainties such as those in the maximum possible magnitude of future earthquakes, in the location of the fault, in the focal depth, and in the attenuation law are accounted for in the calculations and their influence studied. The results identify a seismic belt running from Lake Garda to Friuli and along the Yugoslav coast and are very similar to those already known for Friuli, with the largest values corresponding to the zone around Gemona. Some slight differences in the shape of the areas of equal acceleration are probably due to the delineation of the seismic sources of the proposed model. For a cautious elaboration, some neotectonic lines without present seismicity were added into the fault model. Their contribution is negligible in the areas of highest acceleration, but increases remarkably in the areas where acceleration is not expected to exceed the medium values.