Seismic Project Research Articles

Main geologic factors controlling site response during the 2009 L’Aquila earthquake

The analysis of the damage following the 2009 L'Aquila earthquake clearly indicates a strict control of the local geological conditions over the distribution of the effects.This paper briefly illustrates some of the most significant cases of local effects that have been observed and analysed during the seismic microzoning project promoted by the Italian Civil Protection Department.The observed local effects span over a wide range of typologies, such as classical 1D stratigraphic amplifications within wide extensional basins filled by Quaternary continental deposits, 2D amplifications within basins with horst-and-graben geometry of the bedrock, jointed rock-mass amplification and topographic amplification, though the latter was rarely observed. The paper also focuses on the meaning and significance in terms of site response of the geologicbedrock, which is formed by marine Meso-Cenozoic rocks underlying the Quaternary continental cover in the L'Aquila area, as well as the role of stiff rock bodies within the Quaternary continental succession behaving as a seismic bedrock. A certain number of slope and ground failure cases are also reported, prevailingly falls/topples with rolling and bouncing blocks and cave collapses, as well as co-seismic surface faulting cases. This latter aspect is discussed in the light of the lack of specific recommendations about surface fault-rupture hazard in the Italian regulations for building design in seismic areas.

Comment on "Earthquake Hazard Maps and Objective Testing: The Hazard Mapper's Point of View" by Mark W. Stirling

Article Commentary| September 01, 2012 Comment on “Earthquake Hazard Maps and Objective Testing: The Hazard Mapper's Point of View” by Mark W. Stirling Jens‐Uwe Klügel Jens‐Uwe Klügel Oberer Rainweg 13, 5070 Frick, Switzerland Search for other works by this author on: GSW Google Scholar Author and Article Information Jens‐Uwe Klügel Oberer Rainweg 13, 5070 Frick, Switzerland Publisher: Seismological Society of America First Online: 14 Jul 2017 Online ISSN: 1938-2057 Print ISSN: 0895-0695 © 2012 by the Seismological Society of America Seismological Research Letters (2012) 83 (5): 829–830. https://doi.org/10.1785/0220120051 Article history First Online: 14 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Jens‐Uwe Klügel; Comment on “Earthquake Hazard Maps and Objective Testing: The Hazard Mapper's Point of View” by Mark W. Stirling. Seismological Research Letters 2012;; 83 (5): 829–830. doi: https://doi.org/10.1785/0220120051 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search In his opinion paper “Earthquake Hazard Maps and Objective Testing: The Hazard Mapper’s Point of View,” Stirling (2012) makes the claim that probabilistic seismic hazard (PSH) maps “are tools developed to provide estimates of hazard for long return periods (e.g., hundreds to thousands of years)” (p. 231). He is referring to the applications of PSH models for nuclear facilities and hydro dam developments as successful examples of the probabilistic method. Stirling is recommending PSH applications such as the Yucca Mountain seismic project also for other areas. Despite Stirling’s opinion, PSH maps in use today obviously should not be used for... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Marine broadband case study offshore China

Dual tow-depth acquisition configurations are used to mitigate the band-limiting effect of the sea-surface ghost in marine streamer surveys. Here we report on the analysis of a 2D broadband marine seismic project acquired offshore China. The deployment configuration included over/under sources and three streamers towed at different depths (5, 17, and 23 m). This configuration allowed not only for analysis of dual tow depth as a method for increasing bandwidth, but also for evaluation of two distinct dual tow-depth combinations, over/under and sparse-under. The project provided the first opportunity to make this comparison. Evaluation of reflection images, filter panels, amplitude spectra, and signal/noise separations demonstrates that both techniques are effective at compensating for the filtering effect of the ghost response, but also suggest that the improved results from each dual tow-depth technique are very comparable. Given the operational advantages of the sparse-under technique, due to the reduced streamer requirements, we conclude that the sparse-under technique is an attractive option for 3D deployments.

R&D on Campus: Evolving Operations Drive New Technologies

Editor’s note: JPT surveyed major universities around the world regarding their key upstream research and development projects and activities. The second installment of this series will be published in the July issue. The signposts ahead show that applied, improved technologies such as enhanced oil recovery (EOR), nanotechnology and state-of-the-art reservoir treatment, monitoring and modeling, and unconventional extraction will define the future of the oil and gas industry. As the demand and need for these techniques and technologies increase, research is under way at numerous universities on how to improve recovery factors to meet future world consumption. Institute of Petroleum Engineering, Heriot-Watt University, UK Petroleum engineering at Heriot-Watt University comprises eight general areas of expertise: geomechanics and rock physics, hydrates, hydrocarbon recovery mechanisms, production chemistry, reservoir description, reservoir fluids, reservoir geophysics, and uncertainty quantification. Patrick Corbett, Total professor of petroleum geoengineering, said the reservoir description group is a coming together of joint industry projects at the university. Furthermore, this kind of collaborative, interdisciplinary model is evolving into research networks among multiple universities working on the same project, he said. Industry collaborators with the institute include Shell, ExxonMobil, BG Group, Weatherford, Wintershall, PetroChina, Schlumberger, BP, Chevron, Conoco Phillips, Hess, Landmark, Maersk Oil, Marathon Oil, Petrobras, Statoil, Total, Anadarko, Saudi Aramco, and Eni. The reservoir description group specializes in the integration of geology and engineering for improved quantitative reservoir performance characterization. The reservoir geophysics group’s seismic history matching project uses Schlumberger’s Eclipse, Frontsim and Petrel reservoir data software, Roxar RMS process management software, and Malcolm Sambridge’s NA Algorithm, approaching the subject with geological modeling. The group’s Edinburgh Time-Lapse Project develops reservoir analysis tools for quantitative seismic data interpretation. The main consortium of the production chemistry group is a flow assurance and scale team joint industry project that develops software used to design field scale inhibitor treatments. The reservoir fluids group collaborates with carbon dioxide injection research in partnership with the European Carbon Dioxide Thematic Network, the European Network of Excellence on Geological Storage of Carbon Dioxide, the UK Carbon Capture and Storage Edinburgh Consortium, and the Scottish Centre for Carbon Storage. The uncertainty quantification group is in its third phase, addressing problems of uncertainty and error modeling in production. The geomechanics and rock physics group developed the true triaxial Smart Cell for measurement of stress-sensitive petrophysical and rock property data, and created the spinout company PetroMagnetics.

Crustal velocity structure of the southern Nechako basin, British Columbia, from wide-angle seismic traveltime inversion1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

In the BATHOLITHSonland seismic project, a refraction – wide-angle reflection survey was shot in 2009 across the Coast Mountains and Interior Plateau of central British Columbia. Part of the seismic profile crossed the Nechako Basin, a Jurassic–Cretaceous basin with potential for hydrocarbons within sedimentary strata that underlies widespread volcanic rocks. Along this 205 km-long line segment, eight large explosive shots were fired into 980 seismometers. Forward and inverse modelling of the traveltime data were conducted with two independent methods: ray-tracing based modelling of first and secondary arrivals, and a higher resolution wavefront-based first-arrival seismic tomography. Material with velocities less than 5.0 km/s is interpreted as sedimentary rocks of the Nechako Basin, while velocities from 5.0–6.0 km/s may correspond to interlayered sedimentary and volcanic rocks. The greatest thickness of sedimentary rocks in the basin is found in the central 110 km of the profile. Two sub-basins were identified in this region, with widths of 20–50 km and maximum sedimentary depths of 2.5 and 3.3 km. Such features are well-defined in the velocity model, since resolution tests indicate that features with widths greater than ∼13 km are reliable. Beneath the sedimentary rocks, seismic velocities increase more slowly with depth — from 6.0 km/s just below the basin to 6.3 km/s at ∼17 km in depth, and then to 6.8–7.0 km/s at the base of the crust. The Moho is found at a depth of 33.5–35 km beneath the profile, and mantle velocities are high at 8.05–8.10 km/s.

Ground motion studies for microzonation in Iran

An important step in effectively reducing seismic risk and the vulnerability of a city located in an earthquake prone area is to conduct a ground motion microzonation study for the desired return period. The International Institute of Earthquake Engineering and Seismology (IIEES) initiated a number of seismic microzonation projects for Iran. This paper presents the steps followed by IIEES in ground motion microzonation. IIEES performs both probabilistic and deterministic seismic hazard analysis. IIEES uses his own fault map for seismotectonic studies and develops modulus and damping curves for the soils in the study area. The experience of ground motion microzonation shows that in almost all cases, the estimated 475-year peak ground acceleration (PGA) values are higher than the PGA proposed by the Iranian seismic code. Although ground motion microzonation in Iran has some shortcomings, IIEES is making new improvement. This includes development in deterministic seismic hazard analysis, two-dimensional and three-dimensional modelling of basin and topographical effects, using microtremor measurements to find shear-wave velocity profiles in high-density urban areas and providing maps for spectral acceleration in the study area.

Enhancing dynamic interpretation at the Valhall Field by correlating well activity to 4D seismic signatures

Sequences of 4D seismic changes extracted over different time intervals from multiply repeated seismic surveys are correlated with the identical time sequences of cumulative fluid volumes produced from or injected into wells. Maps of these cross-correlations have previously been shown to produce a localized signal in the connected neighbourhood of individual wells. The technique is applied to the frequently repeated seismic surveys from the life of field seismic project in the Valhall Field, for which the 4D seismic signature is dominated by compaction-assisted pressure depletion. For these data, both acoustic impedance and time-shift attributes are found to have a remarkably consistent correlation with the well activity from selected groups of wells. Furthermore, maps of these results have sufficient fine scale detail to resolve interfering seismic responses generated by closely spaced wells and discrete zones of gas breakout along long horizontal producers. We conclude that uniting well data and 4D seismic data using our proposed method provides a new attribute for dynamic interpretation of the producing reservoir.

Shell's integrated quantitative interpretation workflow

Shell Development Australia is a major asset holder in the Browse Basin and the Carnarvon Basin in the North West Shelf of Australia. In 2007, Shell Development Australia embarked on an integrated quantitative seismic interpretation project related to the Triassic Mungaroo Formation in the Carnarvon Basin. The main objective was to constrain the uncertainties in using seismic data as a predictor for rock and fluid properties of fields and prospects in the basin. This project followed a workflow that has been proven in other basins around the world, whereby the vertical and lateral variability of rock properties of both reservoir and non-reservoir lithologies are captured in general trends. The calculated trends are based on well log extractions of end member lithologies and the input of petrographic information and forward modelling. In combination with a regionally consistent 3D burial model for the estimation of remaining porosity, these established rock trends then allow for a prediction of various acoustic responses of reservoir and pore fill properties. The comparisons between the pre-drill predicted rock properties and the properties encountered after drilling at different reservoir levels have lead to a general confidence that the reservoir properties can be derived from seismic data where well data are not abundant. This increased confidence will play a major part in Shell’s attitude towards appraisal activities and decisions on various development options.

Optimal planning model for school buildings considering the tradeoff of seismic resistance and cost effectiveness: a Taiwan case study

Level of seismic resistance in building design typically correlates negatively with project cost effectiveness as the two objectives of seismic resistance and cost control often conflict. As architects must regularly address this trade-off between degree of seismic safety and project cost, it is an issue that deserves to be explored further. This paper presents a methodology that uses fuzzy theory to determine architect preference functions with regard to seismic resistance and cost effectiveness, and then combine such with an indifference curve to deduce planning weights. This paper also employs the efficient frontier theory to determine the most efficient plans to serve as the basis for architects to apply this model in their own projects. Finally, this paper uses school buildings in Taichung City, Taiwan as the sample to elaborate the developed research method. Optimal planning model for school buildings was achieved to provide a paragon for architects to plan future school buildings.

Geophysics applied to nuclear waste disposal investigations in Switzerland

T. Spillmann, P. Blümling, E. Manukyan, S. Marelli, H. R. Maurer, S.A. Greenhalgh and A.G. Green discuss Swiss research programmes to develop safe solutions for the longterm disposal of high-level radioactive waste in which geophysics plays an important role with respect to site characterization and development of monitoring techniques. Several seismic projects are highlighted in the report.

State-of-the-art of the historical seismology in Colombia

In Colombia are available a discreet number of historical seismology investigations, dating back 50 years. This paper reviews basic information about earthquakes studies in Colombia, such as primary sources, compilation of descriptive catalogues and parametric catalogues. Father Jesus Emilio Ramirez made the main systematic study before 1975. During the last 20 years, great earthquakes hit Colombia and, as consequence, historical seis- mology investigation was developed in the frame of seismic hazard projects.

Seismic Survey of the Locked and Unlocked Sumatra Subduction Zone

The Sumatra subduction zone is the most seismically active region on Earth. In the past 5 years, it has been the site of three great earthquakes, including the 26 December 2004 Sumatra‐Andaman earthquake. That event produced a devastating tsunami around the Indian Ocean that claimed approximately 230,000 lives and caused terrible damage and destruction.Part of the subduction zone still is locked and is likely to break in the next decade or so. To study the seismic and tsunami risk in this locked region, a deep seismic reflection survey, the Tsunami Investigation—Deep Evaluation Seismic (TIDES) project, was carried out in May 2009 using a CGGVeritas vessel towing a 15‐kilometer‐long streamer, the longest ever used during a seismic survey. The survey should provide the first ever seismic images of the locked zone from the seafloor down to a depth of 50 kilometers.

Towards cost-effective permanent seismic reservoir monitoring

One of the challenges faced by reservoir engineers is to understand the way fluid saturation, pressure and compaction change between wells during production of a hydrocarbon reservoir. The optimum placement of infill wells and the identification of new step-out opportunities to maximise recovery of hydrocarbons relies on such information. Time lapse (or 4D) seismic is acknowledged as being the only direct wide-scale reservoir management tool that is capable of revealing these important details about a producing reservoir. The Life of Field Seismic (LoFS) project at the Valhall field on the Norwegian continental shelf illustrates the technical and economic success of reservoir monitoring using 4D seismic data. Today, as the industry explores, drills and produces deeper and/or more challenging targets, reliable and consistent reservoir monitoring is becoming even more essential. A new fibre optic seafloor seismic acquisition system ? with high dynamic range, low background noise, low cost per channel and a long operational life ? is leading the way towards cost-effective permanent seismic reservoir monitoring.

Stress sensitivity of sandstones and 4D applications

Variation of reservoir properties over production time frames is a complex superposition of pore pressure and saturation changes. For this reason, time-lapse (4D) seismic projects to monitor reservoir changes are always subject to the nonuniqueness of interpretation, even if the quality of the 4D signal is good and the magnitude of stress/saturation change is strong. While saturation variations can be adequately handled by Gassmann's theory, stress changes due to pore-pressure depletion within the reservoir are less well understood and multiple conceptual models exist to account for this effect on seismic rock properties.

Deep crustal structure of the Paraná Basin from receiver functions and Rayleigh‐wave dispersion: Evidence for a fragmented cratonic root

The deep crustal structure of the Paraná Basin of southern Brazil is investigated by analyzing P‐ and PP‐wave receiver functions at 17 Brazilian Lithosphere Seismic Project stations within the basin. The study area can be described as a typical Paleozoic intracratonic basin that hosts one of the largest Large Igneous Province of the world and makes a unique setting for investigating models of basin subsidence and their interaction with mantle plumes. Our study consists of (1) an analysis of the Moho interaction phases in the receiver functions to obtain the thickness and bulk Vp/Vs ratio of the basin's underlying crust and (2) a joint inversion with Rayleigh‐wave dispersion velocities from an independent tomographic study to delineate the detailed S‐wave velocity variation with depth. The results of our analysis reveal that Moho depths and bulk Vp/Vs ratios (including sediments) vary between 41 and 48 km and between 1.70 and 1.76, respectively, with the largest values roughly coinciding with the basin's axis, and that S‐wave velocities in the lower crust are generally below 3.8 km/s. Select sites within the basin, however, show lower crustal S‐wave velocities slightly above 3.9 km/s suggestive of underplated mafic material. We show that these observations are consistent with a fragmented cratonic root under the Paraná basin that defined a zone of weakness for the initial Paleozoic subsidence of the basin and which allowed localized mafic underplating of the crust along the suture zones by Cenozoic magmatism.

The role of rock physics for the Enfield 4D seismic monitoring project

The Enfield rock physics model was constructed to enable 4D feasibility studies and interpretation of the 2007 Enfield 4D seismic monitor survey. The rock physics model links reservoir static and dynamic parameters to impedances, using log data from five wells in the field, laboratory core measurements taken from cores on Enfield and neighbouring fields, and theoretical rock models from the literature. The reservoir is modelled by a sand-shale mix: sand properties are described using a modified critical porosity model whereas shale properties are generated from log data averaging. The dynamic properties in the model include saturation and pressure. Saturation is modelled using Gassmann’s formula assuming homogeneous mixing. The reservoir sand velocity-pressure relationship is described by an empirical model fitted to dry core plug measurements. An assessment of the effect of uncertainty is included for both the saturation and pressure elements of the model. The resultant rock physics model was used before the acquisition of the seismic monitor survey to assess the likelihood of detecting a 4D seismic signal only 7 months after production start-up. Our modelling results indicate that the strong pressure build-up around the water injectors would result in a detectable 4D seismic signal and this prediction is confirmed by the successful 4D seismic monitor data acquired in 2007. The rock physics model has been validated against the 4D monitor data and is being used to quantify the 4D interpretation, linking the observed 4D response back to predicted pressure and saturations changes in the field.

Operational implementation of full-azimuth, high-density land acquisition survey in Algeria

In this case study of a complex 3D land seismic project, Marc Girard* (Total), Denis Mougenot (Sercel), Christophe Paulet (Total), Athman Rhamani (Sonatrach), José-Juan Griso (Cepsa), and Youcef Boukhalfa (Enageo) show how today’s high channel counts enable previously unachievable dense spatial sampling and wide aizimuth acquisition.

Anisotropic correction of sonic logs in wells with large relative dip

Seismic reservoir characterization and pore-pressure prediction projects rely heavily on the accuracy and consistency of sonic logs. Sonic data acquisition in wells with large relative dip is known to suffer from anisotropic effects related to microanisotropy of shales and thin-bed laminations of sand, silt, and shale. Nonetheless, if anisotropy parameters can be related to shale content [Formula: see text] in siliciclastic rocks, then I show that it is straightforward to compute the anisotropy correction to both compressional and shear logs using [Formula: see text] and the formation relative dip angle. The resulting rotated P-wave sonic logs can be used to enhance time-depth ties, velocity to effective stress transforms, and low-frequency models necessary for prestack seismic amplitude variation with offset (AVO) inversion.

Chapter 4 Geophysical evidence for the structure of the crust and upper mantle of the Tanzania Craton and the Gregory Rift Valley

The past three decades have seen an upsurge in geophysical fieldwork across the East African Rift Valley in Kenya (KRISP: the Kenya Rift International Seismic Project; Prodehl et al . 1994; Fuchs et al . 1997) and in Ethiopia (Project EAGLE: the Ethiopia Afar Geophysical Lithosphere Experiment; Yirgu et al . 2006). In northern Tanzania, in 1994, A. A. Nyblade and co-workers established an array of broadband receivers in northern Tanzania, the Tanzania Broadband Seismic Experiment, TBSE (Nyblade et al . 1996) that, together with interpretation of earlier commercially acquired data, have provided new insights into the present-day structure of the Tanzania Craton and the Mozambique belt. Although in many experiments data have also been acquired for the Western Rift, attention will be confined in the following section to observations on the northern Tanzania and southern Kenya sectors of the Gregory Rift Valley. The interpretation of gravity data alone does not give a unique solution because Bouguer anomalies can reflect lateral changes in: (i) the density of the crust; (ii) the density of the upper mantle; (iii) the depth to the crust/mantle interface, the Moho; or (iv) a combination of these possible variables. Gravity measurements can, when combined with data from seismic experiments and measured rock densities, lead to integrated models for the structure of the crust and upper mantle, but it is relevant to discuss here the results obtained by individual disciplines. Northern Tanzania lies on the southern margin of a broad, regional, negative Bouguer anomaly around 350±50 km wide and with an amplitude of 800 g.u. relative to a background value of −1200 g.u. (Fig. 4.1). The anomaly, which is highest in Kenya and decreases southwestwards, lies slightly to the west of the present-day rift valley, strikes NNE and is superimposed on a wider 1000 km negative …

An integrated geophysical study of the northern Kenya rift

The Kenyan part of the East African rift is among the most studied rift zones in the world. It is characterized by: (1) a classic rift valley, (2) sheer escarpments along the faulted borders of the rift valley, (3) voluminous volcanics that flowed from faults and fissures along the rift, and (4) axial and flank volcanoes where magma flow was most intense. In northern Kenya, the rift faults formed in an area where the lithosphere was weakened and stretched by Cretaceous-Paleogene extension, and in central and southern Kenya, it formed along old zones of weakness at the contact between the Archean Tanzania craton and the Proterozoic Mozambique orogenic belt. Recent geophysical investigations focused on the tectonic evolution of the East African rift and on exploration for geothermal energy in the southern portion of the Kenyan rift provide considerable information and insight on the structure and evolution of the lithosphere. In the north, a variety of other data exist. However, the lack of an integrated regional analysis of these data was the motivation for this study. Our study began with the collection and compilation of gravity data, and then we used the seismic refraction results from the Kenya Rift International Seismic Project (KRISP), published seismic reflection data, aeromagnetic data, and geologic and drilling data as constraints in the construction of integrated gravity models. These models and gravity anomaly maps provide insight on spatial variations in crustal thickness and upper mantle structure. In addition, they show the distribution of basins and help characterize the distribution of magmatism along the axis of the northern sector of the rift. Our main observations are the following: (1) the region of thinning and anomalous mantle widens northward in agreement with previous studies showing that the crust thins from about 35 km in the south to 20 km in the north; (2) as observed in the south, gravity highs observed along the axis are due to mafic bodies associated with the main volcanic centers, densification of the upper crust due to diking, and horst blocks where Precambrian basement has been brought to or near the surface; (3) the axis of the rift is marked by a series of high amplitude magnetic anomalies whose wavelengths are less than 2.5 km, the positive anomalies coinciding closely with known Quaternary volcanoes.