scholarly journals Limits on the potential accuracy of earthquake risk evaluations using the L’Aquila (Italy) earthquake as an example

2015 ◽  
Vol 58 (2) ◽  
Author(s):  
John Douglas ◽  
Daniel Monfort Climent ◽  
Caterina Negulescu ◽  
Agathe Roullé ◽  
Olivier Sedan
Keyword(s):  
Strong Motion ◽  
Earthquake Risk ◽  
Calibration Data ◽  
Building Vulnerability ◽  
Potential Accuracy ◽  
Ground Shaking ◽  
Local Site ◽  
Damage States ◽  
Macroseismic Intensities ◽  
Strong Motion Network

<p>This article is concerned with attempting to ‘predict’ (hindcast) the damage caused by the L’Aquila 2009 earthquake (M<sub>w</sub> 6.3) and, more generally, with the question of how close predicted damage can ever be to observations. Damage is hindcast using a well-established empirical-based approach based on vulnerability indices and macroseismic intensities, adjusted for local site effects. Using information that was available before the earthquake and assuming the same event characteristics as the L’Aquila mainshock, the overall damage is reasonably well predicted but there are considerable differences in the damage pattern. To understand the reasons for these differences, information that was only available after the event were include within the calculation. Despite some improvement in the predicted damage, in particularly by the modification of the vulnerability indices and the parameter influencing the width of the damage distribution, these hindcasts do not match all the details of the observations. This is because of local effects: both in terms of the ground shaking, which is only detectable by the installation of a much denser strong-motion network and a detailed microzonation, and in terms of the building vulnerability, which cannot be modeled using a statistical approach but would require detailed analytical modeling for which calibration data are likely to be lacking. Future studies should concentrate on adjusting the generic components of the approach to make them more applicable to their location of interest. To increase the number of observations available to make these adjustments, we encourage the collection of damage states (and not just habitability classes) following earthquakes and also the installation of dense strong-motion networks in built-up areas.</p>

A case of the influence of radiation pattern on peak accelerations

1994 ◽  
Vol 84 (5) ◽  
pp. 1658-1664
Author(s):  
Livio Sirovich
Keyword(s):  
Radiation Pattern ◽  
Site Effects ◽  
Strong Motion ◽  
Historical Earthquakes ◽  
Macroseismic Data ◽  
Azimuthal Distribution ◽  
Local Site Effects ◽  
Ground Shaking ◽  
Local Site ◽  
Isoseismal Lines

Abstract The strong ground shaking of the 23 November 1980 earthquake in southern Italy seems to have been conditioned by the dimension of the source, its focal mechanism, and by the distance from the shallow portion of the source. There was only a low, and doubtful, directivity effect. These results come from a comparison of the azimuthal distribution of the recorded peak ground horizontal accelerations with that of the total, dimensionless, radiation pattern of S waves in the horizontal plane at each site (radiation from the closest point of the fault, and appropriate azimuth and take-off angles were considered). The recorded maxima were obtained from hodogram plots of each couple of automatically digitized horizontal components in 13 stations with negligible local site effects at a distance of up to 78 km from the epicenter. The analysis indicates the strong influence of the strike-slip component on the azimuthal distribution of motion. The fault mechanism best fitting the recorded maxima is as follows: strike 318°, dip 64°, rake 317°. This picture does not change if acceleration maxima in the frequency bands 0.1 to 5 Hz, 1 to 5 Hz, or 1 to 2 Hz are used. In a segment of the southern Apennines, where the strong-motion energy radiation in the near/intermediate field of a repetitive series of shocks from the seventeenth century up to 1980 seems to be controlled by the gross features of the source, it could be useful to include radiation patterns into algorithms for regional seismic hazard calculations. Conversely, because of the fact that drawing isoseismal lines results in a smoothing of at least the very local site effects, it might be possible to infer information about the gross features of the sources of historical earthquakes from macroseismic data.

Comparison of earthquake and microtremor ground motions in El Centro, California

1973 ◽  
Vol 63 (4) ◽  
pp. 1227-1253 ◽  
Author(s):  
F. E. Udwadia ◽  
M. D. Trifunac
Keyword(s):  
Site Response ◽  
Ground Motions ◽  
Strong Motion ◽  
Site Conditions ◽  
Ground Shaking ◽  
Response Characteristics ◽  
Local Site ◽  
Simple Features ◽  
Low Amplitude ◽  
Local Site Conditions

abstract Strong earthquake ground shaking has been investigated by the study of 15 events recorded in El Centro, California. The strong-motion records analyzed show that no simple features (e.g., local site conditions) govern the details of local ground shaking. Any effects of local subsoil conditions at this site appear to be overshadowed by the source mechanism and the transmission path, there being no distinctly identifiable site periodicities. Microtremor measurements have been taken in the area surrounding the strong-motion site. The objective was an investigation of possible correlations with strong ground motions and the analysis of site-response characteristics. Basic difficulties in ascertaining local site conditions through such low-amplitude ground motions are illustrated. It has been found that in this area microtremor and earthquake processes are widely different in character, there being little to no correlation between the ground's response to earthquakes and to microtremor excitations. Microtremors have been found to be nonstationary over periods of about a day or so, introducing further uncertainties into inferences from such measurements.

EMS98 intensity estimation of the shallow Le Teil earthquake, ML 5.2, by Macroseismic Response Group GIM

2020 ◽  
Author(s):  
Antoine Schlupp ◽  
Christophe Sira ◽  
Emeline Maufroy ◽  
Ludmila Provost ◽  
Remi Dretzen ◽  
...  
Keyword(s):  
Online Survey ◽  
Insurance Coverage ◽  
Municipal Services ◽  
Ground Shaking ◽  
Local Site ◽  
Scientific Institutions ◽  
Macroseismic Intensities ◽  
Response Group ◽  
Short Time ◽  
Town Halls

&lt;p&gt;BCSF-R&amp;#233;NaSS (Bureau central sismologique fran&amp;#231;ais &amp;#8211; R&amp;#233;seau national de surveillance sismique) manages the collection of data from the field for any earthquake in mainland France of magnitude greater than 3.7 and ensures their interpretation in terms of macro-seismic intensities (severity of ground shaking) on EMS98, European Macroseismic Scale (Gr&amp;#252;nthal, 1998). Unlike the magnitude, which is calculated from seismological records, the intensity of the tremor is only known in each location by analysing the observable effects on people, objects and structures. In case of damage, the GIM (Groupe d'intervention macrosismique = Macroseismic Response Group), coordinated by the BCSF-R&amp;#233;NaSS, establishes EMS98 intensities within a short time after the occurrence of the earthquake. It gathers together scientists (researchers and engineers in tectonics, geology, civil engineering, etc.) from various French scientific institutions.&lt;/p&gt;&lt;p&gt;The 2019-11-11 Le Teil earthquake of magnitude ML 5.2 occurred at 10h52 UTC, 11h52 local time. It is a very shallow event, with hypocentre at about 2km depth and a fault rupture that reached the surface. More than 2000 people who felt the tremor responded to the online survey via the www.franceseisme.fr website, allowing a preliminary and rapid estimation of the intensity of the tremor. The day after the event, the BCSF-R&amp;#233;NaSS launched a survey toward the municipal authorities using a collective form designed for the town halls of the municipalities potentially affected. Given the damage described in the answers, the GIM was mobilized to accurately assess the EMS98 intensities of municipalities near the epicentre, based on the effects observed on buildings, people and objects, and taking into account their vulnerability.&lt;/p&gt;&lt;p&gt;Among the almost sixty experts that compose the GIM, seven from IRSN, ISTerre/RESIF-RAP, Cerema, Pacte/UGA, IPGS and EOST/BCSF-R&amp;#233;NaSS answered the call. Divided into teams of 2 or 3, they inspected 24 municipalities between November 18&lt;sup&gt;th&lt;/sup&gt;and 22&lt;sup&gt;nd&lt;/sup&gt;, assisted by mayors or municipal services and sometimes accompanied by the rescue brigade. Several hundred buildings of different vulnerabilities were inspected.&lt;/p&gt;&lt;p&gt;In most cases, many cracks, sometimes significant and open, were observed. Few of the oldest structures built mostly in the 19&lt;sup&gt;th&lt;/sup&gt;century, associated to vulnerability A, partially or totally collapsed in the most affected areas such as Le Teil and Viviers. For comparable buildings, more severe damages were observed on top of hills (Saint-Thom&amp;#233;) or on sedimentary filling (Savasse) which attests for local site effects.&amp;#160;&lt;/p&gt;&lt;p&gt;The highest intensities reach locally VIII in La Rouvi&amp;#232;re and M&amp;#233;las, two neighbourhood of Le Teil, that are located the closest to the Rouvi&amp;#232;re fault. These are the highest intensities observed in mainland France since the Arette earthquake in 1967 (Roth&amp;#233;, 1972).&lt;/p&gt;&lt;p&gt;The macroseismic intensities EMS98, estimated during the GIM's field missions, are one of the major input on which is based the decision of the French commission to classify municipalities in a state of natural disasters. &amp;#160;That decision triggers insurance coverage of damages. &amp;#160;Over the 24 analysed by the GIM, the commission classified 19 municipalities during their meetings of November 20&lt;sup&gt;th&lt;/sup&gt;and December 11&lt;sup&gt;th&lt;/sup&gt;. Following commission meetings will examine the other impacted municipalities.&lt;/p&gt;

TREMOR: A Wireless MEMS Accelerograph for Dense Arrays

2005 ◽  
Vol 21 (1) ◽  
pp. 91-124 ◽  
Author(s):  
John R. Evans ◽  
Robert H. Hamstra ◽  
Christoph Kündig ◽  
Patrick Camina ◽  
John A. Rogers
Keyword(s):  
Spatial Resolution ◽  
Dynamic Range ◽  
Strong Motion ◽  
The United States ◽  
Companion Paper ◽  
Low Noise ◽  
Practical Reasons ◽  
Wireless Internet ◽  
Urban Centers ◽  
Strong Motion Network

The ability of a strong-motion network to resolve wavefields can be described on three axes: frequency, amplitude, and space. While the need for spatial resolution is apparent, for practical reasons that axis is often neglected. TREMOR is a MEMS-based accelerograph using wireless Internet to minimize lifecycle cost. TREMOR instruments can economically augment traditional ones, residing between them to improve spatial resolution. The TREMOR instrument described here has dynamic range of 96 dB between ±2 g, or 102 dB between ±4 g. It is linear to <1% of full scale (FS), with a response function effectively shaped electronically. We developed an economical, very low noise, accurate (<1%FS) temperature compensation method. Displacement is easily recovered to 10-cm accuracy at full bandwidth, and better with care. We deployed prototype instruments in Oakland, California, beginning in 1998, with 13 now at mean spacing of ∼3 km—one of the most densely instrumented urban centers in the United States. This array is among the quickest in returning (PGA, PGV, Sa) vectors to ShakeMap, ∼75 to 100 s. Some 13 events have been recorded. A ShakeMap and an example of spatial variability are shown. Extensive tests of the prototypes for a commercial instrument are described here and in a companion paper.

i1-net: The Iran Strong Motion Network

2021 ◽  
Author(s):  
Mohammad Pourmohammad Shahvar ◽  
Esmaeil Farzanegan ◽  
Attiyeh Eshaghi ◽  
Hossein Mirzaei
Keyword(s):  
Earthquake Engineering ◽  
Strong Motion ◽  
Current Status ◽  
Primary Input ◽  
The Road ◽  
Leading Position ◽  
Hazard And Risk ◽  
Ground Motion Records ◽  
Strong Motion Network ◽  
Strong Ground

Abstract Strong ground-motion records are the primary input data in earthquake engineering studies to improve understanding of seismic hazard and risk. As the overseer of the Iran Strong Motion Network (i1-net), the Road, Housing, and Urban Development Research Center occupies the leading position in this field in the country. With more than 1260 active accelerometers and a collection of over 14,129 earthquake recordings since 1973, the Iran Strong Motion Network is the major Iranian source of information for engineering seismology and earthquake engineering. The present article describes the current status and developments of the i1-net in the last 46 yr.

Nonlinear behavior of soil sediments identified by using borehole records observed at the Ashigra Valley, Japan

1995 ◽  
Vol 85 (6) ◽  
pp. 1821-1834
Author(s):  
Toshimi Satoh ◽  
Toshiaki Sato ◽  
Hiroshi Kawase
Keyword(s):  
Shear Strain ◽  
Main Part ◽  
Nonlinear Behavior ◽  
Strong Motion ◽  
S Wave ◽  
Ground Shaking ◽  
Wave Velocities ◽  
The One ◽  
Soil Sediments ◽  
Strong Ground

Abstract We evaluate the nonlinear behavior of soil sediments during strong ground shaking based on the identification of their S-wave velocities and damping factors for both the weak and strong motions observed on the surface and in a borehole at Kuno in the Ashigara Valley, Japan. First we calculate spectral ratios between the surface station KS2 and the borehole station KD2 at 97.6 m below the surface for the main part of weak and strong motions. The predominant period for the strong motion is apparently longer than those for the weak motions. This fact suggests the nonlinearity of soil during the strong ground shaking. To quantify the nonlinear behavior of soil sediments, we identify their S-wave velocities and damping factors by minimizing the residual between the observed spectral ratio and the theoretical amplification factor calculated from the one-dimensional wave propagation theory. The S-wave velocity and the damping factor h (≈(2Q)−1) of the surface alluvial layer identified from the main part of the strong motion are about 10% smaller and 50% greater, respectively, than those identified from weak motions. The relationships between the effective shear strain (=65% of the maximum shear strain) calculated from the one-dimensional wave propagation theory and the shear modulus reduction ratios or the damping factors estimated by the identification method agree well with the laboratory test results. We also confirm that the soil model identified from a weak motion overestimates the observed strong motion at KS2, while that identified from the strong motion reproduces the observed. Thus, we conclude that the main part of the strong motion, whose maximum acceleration at KS2 is 220 cm/sec2 and whose duration is 3 sec, has the potential of making the surface soil nonlinear at an effective shear strain on the order of 0.1%. The S-wave velocity in the surface alluvial layer identified from the part just after the main part of the strong motion is close to that identified from weak motions. This result suggests that the shear modulus recovers quickly as the shear strain level decreases.

scholarly journals The 30 October 2020 Samos (Eastern Aegean Sea) Earthquake: effects of source rupture, path and local-site conditions on the observed and simulated ground motions

2021 ◽  
Author(s):  
Aybige Akinci ◽  
Daniele Cheloni ◽  
AHMET ANIL DINDAR
Keyword(s):  
Ground Motion ◽  
Structural Damage ◽  
Ground Motions ◽  
Aegean Sea ◽  
Peak Ground Velocity ◽  
Ground Shaking ◽  
Local Site ◽  
Eastern Aegean ◽  
Motion Characteristics ◽  
Eastern Aegean Sea

Abstract On 30 October 2020 a MW 7.0 earthquake occurred in the eastern Aegean Sea, between the Greek island of Samos and Turkey’s Aegean coast, causing considerable seismic damage and deaths, especially in the Turkish city of Izmir, approximately 70 km from the epicenter. In this study, we provide a detailed description of the Samos earthquake, starting from the fault rupture to the ground motion characteristics. We first use Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) data to constrain the source mechanisms. Then, we utilize this information to analyze the ground motion characteristics of the mainshock in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and spectral pseudo-accelerations. Modelling of geodetic data shows that the Samos earthquake ruptured a NNE-dipping normal fault located offshore north of Samos, with up to 2.5-3 m of slip and an estimated geodetic moment of 3.3 ⨯ 1019 Nm (MW 7.0). Although low PGA were induced by the earthquake, the ground shaking was strongly amplified in Izmir throughout the alluvial sediments. Structural damage observed in Izmir reveals the potential of seismic risk due to the local site effects. To better understand the earthquake characteristics, we generated and compared stochastic strong ground motions with the observed ground motion parameters as well as the ground motion prediction equations (GMPEs), exploring also the efficacy of the region-specific parameters which may be improved to better predict the expected ground shaking from future large earthquakes in the region.

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