scholarly journals Earthquake magnitude scaling using seismogeodetic data

2013 ◽  
Vol 40 (23) ◽  
pp. 6089-6094 ◽  
Author(s):  
Brendan W. Crowell ◽  
Diego Melgar ◽  
Yehuda Bock ◽  
Jennifer S. Haase ◽  
Jianghui Geng
Keyword(s):  
Earthquake Magnitude ◽  
Magnitude Scaling

Equivalent number of uniform cycles versus earthquake magnitude relationships for fine-grained soils

2019 ◽  
Vol 56 (11) ◽  
pp. 1596-1608
Author(s):  
Priyesh Verma ◽  
Ainur Seidalinova ◽  
Dharma Wijewickreme
Keyword(s):  
Large Earthquake ◽  
Earthquake Magnitude ◽  
Undisturbed Soil ◽  
Experimental Database ◽  
Cyclic Shear ◽  
Fine Grained ◽  
Evaluation Procedures ◽  
Magnitude Scaling ◽  
Equivalent Number ◽  
Time Histories

In current geotechnical seismic design practice, the empirical correlation between equivalent number of uniform cycles (Neq) of shaking and earthquake magnitude (Mw) forms an integral part of liquefaction potential evaluation. This relationship, in turn, is used to derive the magnitude scaling factors that are commonly used in field-based liquefaction evaluation procedures. The Neq versus Mw relationship for liquefaction assessment was examined for fine-grained soils using time-histories in the range 5 < Mw ≤ 9, especially including strong ground motion time-histories from the latest subduction zone earthquakes with Mw > 8.0. The experimental database available from cyclic direct simple shear tests conducted on natural fine-grained soils retrieved from undisturbed soil sampling was used to obtain the cyclic shear resistance weighting curves for the study. The work presented herein has contributed to further improving the current models used to represent magnitude scaling factor (MSF) values for large earthquake magnitudes and the functional dependency of this parameter on soil type. The MSF–Mw curve derived for low-plastic Fraser River Delta silt lies in-between the MSF curves derived for clean sand and clay, resonating with the inferences that have been made that the silt behavior can neither be considered sand-like nor clay-like.

Earthquake Magnitude Scaling Using Peak Ground Velocity Derived from High-Rate GNSS Observations

2020 ◽  
Vol 92 (1) ◽  
pp. 227-237
Author(s):  
Rongxin Fang ◽  
Jiawei Zheng ◽  
Jianghui Geng ◽  
Yuanming Shu ◽  
Chuang Shi ◽  
...  
Keyword(s):  
Rapid Determination ◽  
Seismic Station ◽  
Scaling Law ◽  
Large Earthquake ◽  
Earthquake Magnitude ◽  
New Method ◽  
High Rate ◽  
Peak Ground Velocity ◽  
Absolute Deviation ◽  
Magnitude Scaling

Abstract Rapid response to destructive tsunami and seismic events requires rapid determination of the earthquake magnitude. We propose a new method that employs peak ground velocities (PGVs) derived from Global Navigation Satellite System (GNSS) data to estimate earthquake magnitudes. With a total of 1434 records from 22 events as the constraints, we perform the regression and obtain a PGV scaling law for magnitude determination. The advantage of the new method is that the PGVs are extracted from the GNSS velocity waveforms, which can be easily computed using broadcast GNSS ephemeris. In contrast, the peak ground displacement (PGD) depends on a sophisticated high-precision GNSS-processing subject to external correction data, realization of which cannot be kept robust constantly, especially in real time. The results show that the PGV magnitudes agree with reported moment magnitudes with mean absolute deviation of 0.26 magnitude units for the 22 events and also agree well with the PGD magnitude. We further demonstrate that GNSS-derived PGV and the modified Mercalli intensity values can be consistent with their counterparts from the U.S. Geological Survey ShakeMap products and therefore the GNSS-derived PGVs have the potential to be included in the ShakeMap as a complementary constraint, especially in areas with sparse seismic station coverage for large earthquake.

scholarly journals Earthquake Magnitude Estimation using Precise Point Positioning

2021 ◽  
Vol 906 (1) ◽  
pp. 012107
Author(s):  
Jakub Nosek ◽  
Pavel Václavovic
Keyword(s):  
Ground Motion ◽  
Magnitude Estimation ◽  
Precise Point Positioning ◽  
Early Warning Systems ◽  
Earthquake Magnitude ◽  
Parameters Estimation ◽  
Moment Magnitude ◽  
Accurate Estimation ◽  
Magnitude Scaling ◽  
Point Positioning

Abstract An accurate estimation of an earthquake magnitude plays an important role in targeting emergency services towards affected areas. Along with the traditional methods using seismometers, site displacements caused by an earthquake can be monitored by the Global Navigation Satellite Systems (GNSS). GNSS can be used either in real-time for early warning systems or in offline mode for precise monitoring of ground motion. The Precise Point Positioning (PPP) offers an optimal method for such purposes, because data from only one receiver are considered and thus not affected by other potentially not stable stations. Precise external products and empirical models have to be applied, and the initial convergence can be reduced or eliminated by the backward smoothing strategy or integer ambiguity resolution. The product for the magnitude estimation is a peak ground displacement (PGD). PGDs observed at many GNSS stations can be utilized for a robust estimate of an earthquake magnitude. We tested the accuracy of estimated magnitude scaling when using displacement waveforms collected from six selected earthquakes between the years 2016 and 2020 with magnitudes in a range of 7.5–8.2 Moment magnitude MW. We processed GNSS 1Hz and 5Hz data from 182 stations by the PPP method implemented in the G-Nut/Geb software. The precise satellites orbits and clocks corrections were provided by the Center for Orbit Determination in Europe (CODE). PGDs derived on individual GNSS sites formed the basis for ground motion parameters estimation. We processed the GNSS observations by the combination of the Kalman filter (FLT) and the backward smoother (SMT), which significantly enhanced the kinematic solution. The estimated magnitudes of all the included earthquakes were compared to the reference values released by the U. S. Geological Survey (USGS). The moment magnitude based on SMT was improved by 20% compared to the FLT-only solution. An average difference from the comparison was 0.07 MW and 0.09 MW for SMT and FLT solutions, respectively. The corresponding standard deviations were 0.18 MW and 0.22 MW for SMT and FLT solutions, which shows a good consistency of our and the reference estimates.

scholarly journals Frictional properties of anorthite (feldspar): implications for the lower boundary of the seismogenic zone

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Koji Masuda
Keyword(s):  
Dominant Role ◽  
Lower Boundary ◽  
Earthquake Magnitude ◽  
Seismogenic Zone ◽  
Effective Pressure ◽  
Velocity Dependence ◽  
Brittle Deformation ◽  
Frictional Properties ◽  
Depth Extent ◽  
Mineral Constituents

Abstract Earthquake magnitude is closely related to the depth extent of the seismogenic zone, and higher magnitude earthquakes occur where the seismogenic zone is thicker. The frictional properties of the dominant mineral constituents of the crust, such as feldspar-group minerals, control the depth extent of the seismogenic zone. Here, the velocity dependence of the steady-state friction of anorthite, the calcic endmember of the feldspar mineral series, was measured at temperatures from 20 to 600 °C, pore pressures of 0 (“dry”) and 50 MPa (“wet”), and an effective pressure of 150 MPa. The results support previous findings that the frictional properties of feldspar play a dominant role in limiting the depth extent of the seismogenic zone. This evidence suggests that brittle deformation of anorthite may be responsible for brittle fault movements in the brittle–plastic transition zone.

The Validity of Computer-Controlled Magnitude Scaling to Measure Emotional Impact of Stimuli

1984 ◽  
Vol 21 (3) ◽  
pp. 325-331 ◽  
Author(s):  
Bruno Neibecker
Keyword(s):  
Structural Equation ◽  
Discriminant Validity ◽  
Rating Scales ◽  
Emotional Impact ◽  
Equation Approach ◽  
Validity And Reliability ◽  
Magnitude Scaling ◽  
Attitude Measures ◽  
Computer Controlled ◽  
Experimental Findings

A computer-controlled facility is tested which operationalizes magnitude scaling (psychophysics) directly over a CRT screen. The author reports experimental findings comparing magnitude scaling with rating scales as attitude measures of advertisements and erotic pictures. Also, validity and reliability are examined by means of the structural equation approach. On the basis of the level of reliability and the degree of convergent/discriminant validity, magnitude scaling appears to be a valid and reliable alternative to rating scales.

Proposed methodology for estimating the magnitude at which subduction megathrust ground motions and source dimensions exhibit a break in magnitude scaling: Example for 79 global subduction zones

2020 ◽  
Vol 36 (3) ◽  
pp. 1271-1297
Author(s):  
Kenneth W. Campbell
Keyword(s):  
Ground Motion ◽  
Subduction Zones ◽  
Ground Motions ◽  
Seismic Source ◽  
Scaling Relations ◽  
Megathrust Earthquakes ◽  
Source Dimensions ◽  
Magnitude Scaling ◽  
Aspect Ratios ◽  
Source Scaling

In this article, I propose a method for estimating the magnitude [Formula: see text] at which subduction megathrust earthquakes are expected to exhibit a break in magnitude scaling of both seismic source dimensions and earthquake ground motions. The methodology is demonstrated by applying it to 79 global subduction zones defined in the literature, including Cascadia. Breakpoint magnitude is estimated from seismogenic interface widths, empirical source scaling relations, and aspect ratios of physically unbounded earthquake ruptures and their uncertainties. The concept stems from the well-established observation that source-dimension and ground motion scaling decreases for shallow continental (primarily strike-slip) earthquakes when rupture exceeds the seismogenic width of the fault. Although a scaling break for megathrust earthquakes is difficult to observe empirically, all of the instrumentally recorded historical [Formula: see text] mega-earthquakes have occurred on subduction zones with [Formula: see text] (8.1–8.9), consistent with an observed break in source scaling relations derived from these same events. The breakpoint magnitudes derived in this study can be used to constrain the magnitude at which the scaling of ground motion is expected to decrease in subduction ground motion prediction equations.

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