Near-Field Ground Motion of the 2002 Denali Fault, Alaska, Earthquake Recorded at Pump Station 10

2004 ◽  
Vol 20 (3) ◽  
pp. 597-615 ◽  
Author(s):  
W. L. Ellsworth ◽  
M. Celebi ◽  
J. R. Evans ◽  
E. G. Jensen ◽  
R. Kayen ◽  
...  
Keyword(s):  
Ground Motion ◽  
Near Field ◽  
Free Field ◽  
Monitoring And Control ◽  
Peak Acceleration ◽  
Permanent Displacement ◽  
Soil Response ◽  
Denali Fault ◽  
Field Recording ◽  
Pump Station

A free-field recording of the Denali fault earthquake was obtained by the Alyeska Pipeline Service Company 3 km from the surface rupture of the Denali fault. The instrument, part of the monitoring and control system for the trans-Alaska pipeline, was located at Pump Station 10, approximately 85 km east of the epicenter. After correction for the measured instrument response, we recover a seismogram that includes a permanent displacement of 3.0 m. The recorded ground motion has relatively low peak acceleration (0.36 g) and very high peak velocity (180 cm/s). Nonlinear soil response may have reduced the peak acceleration to this 0.36 g value. Accelerations in excess of 0.1 g lasted for 10 s, with the most intense motion occurring during a 1.5-s interval when the rupture passed the site. The low acceleration and high velocity observed near the fault in this earthquake agree with observations from other recent large-magnitude earthquakes.

scholarly journals Study on the influence of seafloor soft soil layer on seismic ground motion

2020 ◽  
Author(s):  
Jingyan Lan ◽  
Juan Liu ◽  
Xing Song
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Sea Water ◽  
Response Spectrum ◽  
Soft Soil ◽  
Free Field ◽  
Soil Layer ◽  
Response Analysis ◽  
Peak Acceleration ◽  
Seismic Response Analysis

Abstract. In the complex medium system of sea area, the overlying sea water and the surface soft soil have a significant impact on the seafloor ground motion, which brings great seismic risk to the safety of offshore engineering structures. In this paper, four sets of typical free field models are constructed and established, which are land model, land model with surface soft soil, sea model and sea model with surface soft soil. The dynamic finite difference method is used to carry out two-dimensional seismic response analysis of typical free field based on the input forms about P and SV wave. By comparing the seismic response analysis results of four groups of calculation models, the effects of overlying seawater and soft soil on peak acceleration and acceleration response spectrum are studied. The results show that when SV wave is input, the peak acceleration and response spectrum of the surface of soft soil on the surface and the seabed surface can be amplified, while the overlying sea water can significantly reduce the ground motion. When P wave is used, the effect of overlying seawater and soft soil on peak acceleration and response spectrum of surface and seabed can be ignored. The peak acceleration decreases first and then increases from the bottom to the surface, and the difference of peak acceleration calculated by four free field models is not obvious. The results show that the overlying sea water and the surface soft soil layer have little effect on the peak acceleration of ground motion below the surface.

Attenuation relations for strong seismic ground motion in Canada

1981 ◽  
Vol 71 (6) ◽  
pp. 1943-1962
Author(s):  
H. S. Hasegawa ◽  
P. W. Basham ◽  
M. J. Berry
Keyword(s):  
Ground Motion ◽  
Near Field ◽  
Strong Motion ◽  
Alternative Methods ◽  
Western Canada ◽  
Peak Acceleration ◽  
Eastern Canada ◽  
Attenuation Relations ◽  
Seismic Ground Motion ◽  
Hypocentral Distance

Abstract Strong seismic ground motion attenuation relations based primarily on Western United States data, in conjunction with intensity data from eastern and western Canada, are employed to derive new attenuation relations for horizontal strong seismic ground motion for application throughout Canada. The following peak acceleration (ap) and peak velocity (vp) relations are proposed for use in western Canada a p ( cm sec − 2 ) = 10 e 1.3 M R − 1.5 v p ( cm sec − 1 ) = 0.00040 e 2.3 M R − 1.3 where M is magnitude and R hypocentral distance (km). The difference in the distance attenuation of Modified Mercalli intensity in eastern and western Canada, and an assumption of equivalent strong motion in the near field in the two regions, is applied to the western relations to derive the following relations proposed for use in eastern Canada a p ( cm sec − 2 ) = 3.4 e 1.3 M R − 1.1 v p ( cm sec − 1 ) = 0.00018 e 2.3 M R − 1.0 . The proposed relations are in reasonable agreement with the small amount of strong motion data available for western and eastern Canada. Within the accuracy justified by very scattered experimental data, peak vertical and sustained horizontal acceleration and velocity can be estimated as 23 of the peak horizontal values. The magnitude and distance dependence of acceleration and velocity parameters are sufficiently different that the relative levels of ground motion bounds in different frequency ranges will depend on the dominant magnitudes of, and distance ranges to, the earthquakes contributing risk in various regions of Canada. The results indicate the importance of mapping risk for parameters in addition to simple peak acceleration, and suggest alternative methods of deriving ground motion bounds required for the development of design response spectra.

Nonlinear soil response in the vicinity of the Van Normal Complex following the 1994 Northridge, California, earthquake

1999 ◽  
Vol 89 (5) ◽  
pp. 1214-1231 ◽  
Author(s):  
Giovanna Cultrera ◽  
David M. Boore ◽  
William B. Joyner ◽  
Christopher M. Dietel
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Free Field ◽  
Strong Motion ◽  
High Amplitude ◽  
Amplitude Dependence ◽  
Spectral Ratios ◽  
Data Set ◽  
Soil Response ◽  
Equivalent Linear

Abstract Ground-motion recording obtaineds at the Van Norman Complex from the 1994 Northridge, California, mainshock and its aftershocks constitute an excellent data set for the analysis of soil response as a function of ground-motion amplitude. We searched for nonlinear response by comparing the Fourier spectral ratios of two pairs of sites for ground motions of different levels, using data from permanent strong-motion recorders and from specially deployed portable instruments. We also compared the amplitude dependence of the observed ratios with the amplitude dependence of the theoretical ratios obtained from 1-D linear and 1-D equivalent-linear transfer functions, using recently published borehole velocity profiles at the sites to provide the low-strain material properties. One pair of sites was at the Jensen Filtration Plant (JFP); the other pair was the Rinaldi Receiving Station (RIN) and the Los Angeles Dam (LAD). Most of the analysis was concentrated on the motions at the Jensen sites. Portable seismometers were installed at the JFP to see if the motions inside the structures housing the strong-motion recorders differed from nearby free-field motions. We recorded seven small earthquakes and found that the high-frequency, low-amplitude motions in the administration building were about 0.3 of those outside the building. This means that the lack of high frequencies on the strong-motion recordings in the administration building relative to the generator building is not due solely to nonlinear soil effects. After taking into account the effects of the buildings, however, analysis of the suite of strong- and weak-motion recordings indicates that nonlinearity occurred at the JFP. As predicted by equivalent-linear analysis, the largest events (the mainshock and the 20 March 1994 aftershock) show a significant deamplification of the high-frequency motion relative to the weak motions from aftershocks occurring many months after the mainshock. The weak-motion aftershocks recorded within 12 hours of the mainshock, however, show a relative deamplification similar to that in the mainshock. The soil behavior may be a consequence of a pore pressure buildup during large-amplitude motion that was not dissipated until sometime later. The motions at (RIN) and (LAD) are from free-field sites. The comparison among spectral ratios of the mainshock, weak-motion coda waves of the mainshock, and an aftershock within ten minutes of the mainshock indicate that some nonlinearity occurred, presumably at (RIN) because it is the softer site. The spectral ratio for the mainshock is between that calculated for pure linear response and that calculated from the equivalent-linear method, using commonly used modulus reduction and damping ratio curves. In contrast to the Jensen sites, the ratio of motions soon after the high-amplitude portion of the mainshock differs from the ratio of the mainshock motions, indicating the mechanical properties of the soil returned to the low-strain values as the high-amplitude motion ended. This may indicate a type of nonlinear soil response different from that affecting motion at the Jensen administration building.

Can We Trust High-Frequency Content in Strong-Motion Database Signals? Impact of Housing, Coupling, and Installation Depth of Seismic Sensors

2020 ◽  
Vol 91 (4) ◽  
pp. 2192-2205 ◽  
Author(s):  
Fabrice Hollender ◽  
Zafeiria Roumelioti ◽  
Emeline Maufroy ◽  
Paola Traversa ◽  
Armand Mariscal
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Free Field ◽  
Strong Motion ◽  
Response Spectra ◽  
High Frequencies ◽  
Field Recording ◽  
Seismic Motion ◽  
Free Data ◽  
Installation Depth

Abstract Seismic hazard studies provide indicators of seismic motion that are expressed for “free-field,” that is, representative of the ground motion exactly at the free surface, without disturbances due to interactions between soil and buildings or other structures. Most of these studies are based on ground-motion prediction equations, which are, themselves, formulated to predict free-field motion, as they are derived from similarly free data. However, is this really the case? In this study, we use several examples to illustrate how small structures hosting permanent strong-motion stations (often anchored on small concrete slabs) generate soil–structure interaction effects that can amplify the high-frequency part of the earthquake signal (>10  Hz) by up to a factor of 2–3 for stations on soils. We also show that the installation depth of a station, even if very shallow (i.e., a few meters), can change the recorded response, mainly by deamplifying the signal in high frequencies (>10  Hz) by a factor up to 0.3. Such effects imply that there are actual differences between recorded and true free-field signals. Depending on the housing conditions, these effects can have significant impact on response spectra at high frequencies, and on measurements of the κ parameter. It is, thus, becoming clear that such effects should be taken into account in studies involving high-frequency seismic motion. To do so, scientists need a detailed description of the conditions of installation and housing of seismological and accelerometric stations, which often lacks from the metadata distributed through the various, commonly used web services. Increasing such information and facilitating the access to it would allow the identification of stations that are problematic and of those that are truly close to free-field recording conditions. In a subsequent step, it would be important to quantify the modification curve of the response of stations that experience such effects.

Characteristics of Free-Field Vertical Ground Motion during the Northridge Earthquake

1995 ◽  
Vol 11 (4) ◽  
pp. 515-525 ◽  
Author(s):  
Youself Bozorgnia ◽  
Mansour Niazi ◽  
Kenneth W. Campbell
Keyword(s):  
Ground Motion ◽  
Near Field ◽  
Free Field ◽  
Seismic Source ◽  
Spectral Ratio ◽  
Response Spectra ◽  
Northridge Earthquake ◽  
Attenuation Relationships ◽  
Vertical Ground Motion ◽  
Vertical Ground

Characteristics of response spectra of free-field vertical ground motion recorded during the 1994 Northridge earthquake are examined. Dependence of vertical and horizontal response spectra, and their ratio, on the site-to-source distance is investigated through development of attenuation relationships for vertical and horizontal spectral ordinates. The database includes 123 response spectra of the motions recorded at 41 alluvial sites. Vertical-to-horizontal (V/H) response spectral ratio is found to be strongly dependent on period and distance of site to the seismic source. V/H spectral ratio largely exceeds the commonly assumed value of 2/3, at short periods in the near-field region. The main characteristics of V/H spectral ratio for the Northridge earthquake are found to be qualitatively similar to those observed in the 1989 Loma Prieta, California, and in several other earthquakes recorded over the SMART-1 array in Taiwan. These characteristics are very likely to be universal.

Directivity Effect in the Peak Ground Acceleration Fields and Attenuation Relations - A Case Study of the Ms 8.0 Wenchuan Earthquake

2011 ◽  
Vol 250-253 ◽  
pp. 2554-2557
Author(s):  
Jin Jun Hu ◽  
Li Li Xie ◽  
Yong Qiang Yang
Keyword(s):  
Wenchuan Earthquake ◽  
Ground Motion ◽  
Near Field ◽  
Time History ◽  
Rupture Directivity ◽  
Peak Acceleration ◽  
Ground Acceleration ◽  
Attenuation Relations ◽  
Directivity Effect ◽  
Ground Motion Attenuation

We study the characteristics of ground motion fields and peak ground motion attenuation relations during the 2008 Ms 8.0 great Wenchuan earthquake by using 198 sets of three-component acceleration time history recordings. To provide a comparable result to other earthquakes, we first rotated the east-west (EW) and north-south (NS) orientated ground motion to fault strike normal (FN) and fault strike parallel (FP) directions. Through comparison of the near-field peak acceleration fields and peak acceleration attenuation relations, there obviously exists a rupture directivity effect in the peak ground accelerations. The amplitude in the rupture propagation direction is higher than that of the opposite direction. And the closer the station to the fault plane, the smaller the difference of ground motion amplitude between the two opposite directions.

scholarly journals Study on the influence of the seafloor soft soil layer on seismic ground motion

2021 ◽  
Vol 21 (2) ◽  
pp. 577-585
Author(s):  
Jingyan Lan ◽  
Juan Liu ◽  
Xing Song
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Response Spectrum ◽  
Soft Soil ◽  
Free Field ◽  
Soil Layer ◽  
P Wave ◽  
Response Analysis ◽  
Peak Acceleration ◽  
Seismic Response Analysis

Abstract. In the complex medium system of the sea area, the overlying seawater and the surface soft soil have a significant impact on the seafloor ground motion, which brings great seismic risk to the safety of offshore-engineering structures. In this paper, four sets of typical free-field models are constructed and established, comprising a land model, land model with surface soft soil, sea model and sea model with surface soft soil. The dynamic finite-difference method is used to carry out two-dimensional seismic response analysis of a typical free field based on the input forms of P and SV waves. By comparing the seismic response analysis results of four groups of calculation models, the effects of overlying seawater and soft soil on the peak acceleration and acceleration response spectrum are studied. The results show that when an SV wave is input, the peak acceleration and response spectrum of the surface of soft soil on the surface and the seabed surface can be amplified, while the overlying seawater can significantly reduce the ground motion. When the P wave is used, the effect of overlying seawater and soft soil on the peak acceleration and response spectrum of the surface and seabed can be ignored. The peak acceleration decreases first and then increases from the bottom to the surface, and the difference of peak acceleration calculated by four free-field models is not obvious. The results show that the overlying seawater and the surface soft soil layer have little effect on the peak acceleration of ground motion below the surface.

The Borah Peak, Idaho Earthquake of October 28, 1983—Strong Ground Motion

1985 ◽  
Vol 2 (1) ◽  
pp. 51-69 ◽  
Author(s):  
Suzette M. Jackson ◽  
John Boatwright
Keyword(s):  
Ground Motion ◽  
Main Shock ◽  
Near Field ◽  
Free Field ◽  
Ground Level ◽  
Shock Acceleration ◽  
Epicentral Area ◽  
Floor Level ◽  
Ground Floor ◽  
Vertical Accelerations

The 1983 Borah Peak, Idaho Earthquake was the largest normal faulting event to occur in the last 20 years. There were no near-field recordings of ground motion during the main shock, however, thirteen accelerographs in a permanent array at the Idaho National Engineering Laboratory (INEL) recorded the event at epicentral distances of 90-110 km. Peak horizontal accelerations, or PGA, recorded at accelerographs above ground-floor level range from 0.037 to 0.187 g. Accelerographs at basement and free-field sites recorded as low as 0.022 g and as high as 0.078 g. Peak vertical accelerations range from 0.016 g at ground level to 0.059 g above ground-floor level. A temporary array of digital seismographs deployed by the U. S. Geological Survey (USGS) in the epicentral area recorded ground motion from six large aftershocks at epicentral distances of 4-45 km; the largest of these aftershocks also triggered four accelerographs in the INEL array. This paper presents our estimates of near-field ground motion derived from two separate analyses. The first analysis uses the attenuation of the aftershock PGA measurements to extrapolate the INEL main shock PGA measurements into the near-field. This estimates an upper limit of 0.8 g for near-field ground motion. In the second analysis, a set of main shock accelerograms were synthesized. Wave propagation effects were determined from aftershock recordings at one of the USGS portable stations and an INEL seismograph station. These effects were removed from one of the INEL main shock acceleration traces. The synthetic accelerograms were derived for a hypothetical station southwest of Mackay, Idaho. The PGA measured from the synthetic accelerograms were 0.08, 0.14, 0.15, 0.23 g. These estimates correlate well with ground motion expected for an area of intensity VII.

Strong-Motion Records of the 2002 Denali Fault, Alaska, Earthquake

2004 ◽  
Vol 20 (3) ◽  
pp. 579-596 ◽  
Author(s):  
Artak Martirosyan ◽  
Roger Hansen ◽  
Natalia Ratchkovski
Keyword(s):  
Near Field ◽  
Strong Motion ◽  
Fault Rupture ◽  
Ground Acceleration ◽  
Denali Fault ◽  
Motion Data ◽  
Field Recordings ◽  
Pump Station ◽  
Slip Event ◽  
Major Strike

The MW 7.9 Denali Fault earthquake on 3 November 2002 ruptured a 340-km section along the Susitna Glacier, Denali, and Totschunda faults in central Alaska. The earthquake was digitally recorded at more than 55 strong-motion sites throughout the state at distances up to 280 km from the fault rupture. The site closest to the fault, Trans-Alaska Pipeline Pump Station 10, is located about 3 km north of the surface rupture, where the observed maximum horizontal peak ground acceleration was about 0.35 g. The peak horizontal accelerations observed at the sites closest to the fault rupture were considerably smaller than those yielded by the ground-motion prediction equations. Although the earthquake provided a valuable set of strong-motion data, an important opportunity was missed to capture near-field recordings from such a major strike-slip event. A concerted national effort is needed to prioritize the instrumentation of faults that are likely locations of future great earthquakes.

Sign in / Sign up

Export Citation Format

Share Document