Stress Drop, Slip Type, Earthquake Magnitude, and Seismic Hazard

2001 ◽  
Vol 91 (4) ◽  
pp. 694-707 ◽  
Author(s):  
B. Mohammadioun
Keyword(s):  
Seismic Hazard ◽  
Stress Drop ◽  
Earthquake Magnitude

Application of the bootstrap method to quantify uncertainty in seismic hazard estimates

1992 ◽  
Vol 82 (1) ◽  
pp. 104-119
Author(s):  
Michéle Lamarre ◽  
Brent Townshend ◽  
Haresh C. Shah
Keyword(s):  
Confidence Interval ◽  
Seismic Hazard ◽  
Statistical Method ◽  
Bootstrap Method ◽  
Earthquake Magnitude ◽  
Earthquake Catalog ◽  
Uncertainty Measure ◽  
Attenuation Models ◽  
The Bootstrap Method

Abstract This paper describes a methodology to assess the uncertainty in seismic hazard estimates at particular sites. A variant of the bootstrap statistical method is used to combine the uncertainty due to earthquake catalog incompleteness, earthquake magnitude, and recurrence and attenuation models used. The uncertainty measure is provided in the form of a confidence interval. Comparisons of this method applied to various sites in California with previous studies are used to confirm the validity of the method.

Large Uncertainties in Earthquake Stress-Drop Estimates and Their Tectonic Consequences

2020 ◽  
Vol 91 (4) ◽  
pp. 2320-2329 ◽  
Author(s):  
James S. Neely ◽  
Seth Stein ◽  
Bruce D. Spencer
Keyword(s):  
Seismic Hazard ◽  
Stress Drop ◽  
Hazard Analysis ◽  
Earthquake Hazards ◽  
Teleseismic Data ◽  
Tectonic Environment ◽  
Zero Correlation ◽  
Environment Stress ◽  
Stress Drops ◽  
Erroneous Inferences

Abstract Earthquake stress drop, the stress change on a fault due to an earthquake, is important for seismic hazard analysis because it controls the level of high-frequency ground motions that damage structures. Numerous studies report that stress drops vary by tectonic environment, providing insight into a region’s seismic hazard. Here, we show that teleseismic stress-drop estimates have large uncertainties that make it challenging to distinguish differences between the stress drops of different earthquakes. We compared stress drops for ∼900 earthquakes derived from two independent studies using teleseismic data and found practically zero correlation. Estimates for the same earthquake can differ by orders of magnitude. Therefore, reported stress-drop differences between earthquakes may not reflect true differences. As a result of these larger uncertainties, some tectonic environment stress-drop patterns that appear in one study do not appear in the other analysis of the same earthquakes. These large uncertainties in teleseismic estimates might lead to erroneous inferences about earthquake hazards. In many applications, it may be more appropriate to assume that earthquakes in different regions have approximately the same average stress drop.

Lessons from a Small Local Earthquake (Mw 3.2) That Produced the Highest Acceleration Ever Recorded in Mexico City

2020 ◽  
Vol 91 (6) ◽  
pp. 3391-3406
Author(s):  
Shri Krishna Singh ◽  
Luis Quintanar-Robles ◽  
Danny Arroyo ◽  
Victor Manuel Cruz-Atienza ◽  
Victor Hugo Espíndola ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Mexico City ◽  
Stress Drop ◽  
Seismic Waves ◽  
Earthquake Swarm ◽  
Site Amplification ◽  
Function Technique ◽  
Ground Acceleration ◽  
Crustal Earthquakes ◽  
Variable Site

Abstract A reliable estimation of seismic hazard-facing Mexico City from local earthquakes has suffered from poor seismic instrumentation, complex crustal structure, large and variable site amplification, and lack of knowledge of recurrence period of earthquakes on the mapped faults. Owing to recent improvement in local seismic networks, an earthquake swarm activity, which occurred in June–August 2019, was well recorded. The largest event of the sequence, an Mw 3.2 earthquake, caused panic in the city and produced peak ground acceleration (PGA) exceeding 0.3g at the closest station (MHVM) about 1 km away. An analysis of the event shows that it had normal-faulting focal mechanism, consistent with northeast–southwest-oriented mapped faults in the region. It was located at a depth of ∼1  km and had a low stress drop (∼0.1  MPa). We find that the high PGA for this low stress-drop event resulted from high-frequency amplification at MHVM (about factor of ∼6 around 13 Hz), likely due to topographic site effects, superimposed on a pervasive broadband amplification of seismic waves at hill-zone sites in the Valley of Mexico (up to ∼10 in the frequency band of 0.2–10 Hz). Simulation of ground motion for a scenario Mw 5.0 earthquake, using an empirical Green’s function technique, reveals that such an event may give rise to significant seismic intensities in the lake-bed zone of Mexico City. The results emphasize the need to re-evaluate the seismic hazard to Mexico City from local crustal earthquakes in the Valley of Mexico.

Geomechanical modeling of induced seismicity source parameters and implications for seismic hazard assessment

Geophysics ◽  
2013 ◽  
Vol 78 (1) ◽  
pp. KS25-KS39 ◽  
Author(s):  
Bettina P. Goertz-Allmann ◽  
Stefan Wiemer
Keyword(s):  
Seismic Hazard ◽  
Pore Pressure ◽  
Stress Drop ◽  
Induced Seismicity ◽  
Critical Stress ◽  
Source Parameters ◽  
Differential Stress ◽  
Geomechanical Properties ◽  
Stress Changes ◽  
Stress States

We simulate induced seismicity within a geothermal reservoir using pressure-driven stress changes and seismicity triggering based on Coulomb friction. The result is a forward-modeled seismicity cloud with origin time, stress drop, and magnitude assigned to each individual event. Our model includes a realistic representation of repeating event clusters, and is able to explain in principle the observation of reduced stress drop and increased [Formula: see text]-values near the injection point where pore-pressure perturbations are highest. The higher the pore-pressure perturbation, the less critical stress states still trigger an event, and hence the lower the differential stress is before triggering an event. Less-critical stress states result in lower stress drops and higher [Formula: see text]-values, if both are linked to differential stress. We are therefore able to establish a link between the seismological observables and the geomechanical properties of the source region and thus a reservoir. Understanding the geomechanical properties is essential for estimating the probability of exceeding a certain magnitude value in the induced seismicity and hence the associated seismic hazard of the operation. By calibrating our model to the observed seismicity data, we can estimate the probability of exceeding a certain magnitude event in space and time and study the effect of injection depth and crustal strength on the induced seismicity.

Earthquake Magnitude and Lg Q Variations between the Grenville and Northern Appalachian Geologic Provinces of Eastern Canada

2020 ◽  
Vol 110 (2) ◽  
pp. 698-714 ◽  
Author(s):  
H. K. Claire Perry ◽  
Allison L. Bent ◽  
Daniel E. McNamara ◽  
Stephen Crane ◽  
Michal Kolaj
Keyword(s):  
Seismic Hazard ◽  
Hazard Analysis ◽  
Vertical Component ◽  
Earthquake Magnitude ◽  
Waveform Analysis ◽  
Eastern Canada ◽  
Frequency Dependent ◽  
Motion Models ◽  
Anelastic Attenuation ◽  
Specific Frequency

ABSTRACT This article assesses the ability of regionally specific, frequency-dependent crustal attenuation (1/Q) to reduce mean magnitude discrepancies between seismic stations in the northern Appalachian and Grenville provinces (NAP and GP) of Canada. LgQ(f) is an important parameter in ground-motion models used in probabilistic seismic hazard analysis. Discrepancies in regional magnitude estimates have long been noted to exist between stations in the two provinces for common event origins. Such discrepancies could arise from systematic site condition variations between the geologic provinces or from varying crustal attenuative properties. To evaluate the effect of frequency-dependent anelastic attenuation, LgQ(f) on estimated magnitudes, we analyze Lg amplitudes from >6000 waveforms recorded by Grenville and northern Appalachian receivers from 420 natural earthquakes of MN magnitude 3–5.6. Waveform analysis is strictly limited to analyst-reviewed, vertical-component waveforms in which Lg is clearly identified, ensuring that the datasets exhibit dominant, high-frequency energy in the Lg velocity window. LgQ(f) is found to be higher in the GP than in the northern Appalachians. In the Grenville, Q(f)=761(±145)f0.25(±0.014), and in the northern Appalachians, attenuation is higher: Q(f)=506(±172)f0.33(±0.310). Earthquake magnitude determined using the peak amplitude of the Lg phase (mbLg) for eastern Canada is corrected to incorporate the frequency-dependent, regionally specific LgQ(f) determined in this study. Using the new LgQ(f) values diminishes and nearly resolves magnitude discrepancies between the provinces. Correcting regional magnitude discrepancies between provinces is critical for reliable regional seismic hazard estimates because magnitude error in a particular region could lead to increased uncertainty in seismic hazard models.

scholarly journals Macroseismic intensity attenuation equations for Central Asia earthquakes

2021 ◽  
Vol 929 (1) ◽  
pp. 012029
Author(s):  
T U Artikov ◽  
R S Ibragimov ◽  
T L Ibragimova ◽  
M A Mirzaev
Keyword(s):  
Seismic Hazard ◽  
Central Asia ◽  
Seismic Intensity ◽  
Macroseismic Intensity ◽  
Earthquake Magnitude ◽  
Source Depth ◽  
Strong Earthquakes ◽  
Intensity Attenuation ◽  
Hazard Assessments ◽  
Macroseismic Survey

Abstract Based on macroseismic survey data for strong earthquakes in Central Asia, the coefficients of attenuation of seismic intensities with distance in the Blake-Shebalin- and Kovesligethy -type equations were refined. A new generalized dependence of macroseismic intensity attenuation on distance, taking into account the depth of the earthquake hypocentre, were obtained. Relations between the minor and major axes of the ellipse approximating real isoseists depending on the shaking strength, source depth and earthquake magnitude were found. With the example of the territory of eastern Uzbekistan, the influence of the choice of the law of seismic intensity attenuation with distance on the obtained seismic hazard assessments is investigated.

scholarly journals Seismic hazard and seismicity parameters in southwestern Alborz

2021 ◽  
Vol 34 (02) ◽  
pp. 661-670
Author(s):  
Fereshteh Pourmohammad ◽  
Mehdi Zare ◽  
Arezoo Dorostian ◽  
Bahram Akasheh
Keyword(s):  
Seismic Hazard ◽  
Return Period ◽  
Earthquake Magnitude ◽  
Seismic Sources ◽  
Maximum Magnitude ◽  
Seismic Belt ◽  
The South ◽  
Seismic Zones ◽  
Seismicity Parameters ◽  
Tehran Province

Alborz Province is located west of Tehran Province on the South Alborz seismic belt. Geological and seismological analyses within a radius of 200 km from the center of Karaj identified five seismic zones and seven linear seismic sources. The maximum magnitude was calculated for the seismic zones using available correlations. The Kijko and Sellevoll (1992) method was used to calculate seismicity parameters, and the graphs of the return period and the probability frequency of recurrence of the earthquake magnitude in each zone were plotted for the 475-year return period. According to the calculations, the highest and lowest earthquake magnitudes of 7.6 and 6.2 were respectively obtained in Zones 1 and 4.

Stress drop in earthquakes

1968 ◽  
Vol 58 (1) ◽  
pp. 249-257 ◽  
Author(s):  
Chi-Yu King ◽  
Leon Knopoff
Keyword(s):  
Stress Drop ◽  
Earthquake Magnitude ◽  
Dislocation Theory ◽  
Energy Formula ◽  
Fault Trace ◽  
Fault Length

abstract A correlation is made between earthquake magnitude and parameters of fault trace on the basis of dislocation theory. For earthquakes with magnitudes M between 5.5 and 8.5, the correlation with fault length L and the maximum horizontal or vertical offset D (both in cm) is approximately log L D 2 = 2.24 M − 4.99. Combining this result with a magnitude-energy formula, it is found that the stress drop is dependent upon magnitude, with the fractional stress drop increasing with magnitude.

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