Engineering · Engineering-seismological studies & MASW geophysics

Every structure in Albania is designed for an earthquake. The question is which one. Our engineering-seismological study measures how the ground at your site actually behaves and turns that into the seismic parameters and design spectra your structural engineer needs, to Eurocode 8 and KTP-N2-89.

We measure the shear-wave velocity of the ground on site with a 24-channel MASW survey, classify the ground, assess the seismic hazard for the required return periods and deliver a signed report ready for the building permit. Our seismologist runs the fieldwork and analysis, and the report goes through technical review and approval under our ISO/IEC 17025-accredited laboratory’s quality system.

Vs,30shear-wave velocity measured on site, not assumed from tables
EC8 + KTP-N2-89design spectra to both codes in one report
95 / 475 yearsdamage-limitation and no-collapse hazard levels
VKM 1162/2020the seismic study required for the development permit

Who needs a seismic study

  • Developers applying for a building permit. Under VKM no. 1162 of 24.12.2020, new developments need a seismic risk assessment of the site before the permit is issued.
  • Structural designers. They need site-specific design input: ground type, design acceleration and response spectra, instead of conservative defaults.
  • Owners of existing buildings. A change of use, extension, purchase or post-earthquake check needs a seismic assessment, which starts with the site’s seismic action.
  • Infrastructure and industrial projects. Tanks, bridges and plants are sensitive to the site period and spectral shape.

What you receive

A complete engineering-seismological report, coordinated with the geological-engineering (borehole) report for the same site. It contains:

Result What the designer uses it for
Shear-wave velocity profile Vs(z) and Vs,30 Ground stiffness with depth, correlated with the borehole logs
Ground type to EN 1998-1 (A–E) and KTP-N2-89 category (I–III) Selects the soil factor S and the corner periods of the spectrum
Reference peak ground acceleration agR on rock, 95 and 475 years The damage-limitation and no-collapse seismic action, from probabilistic (Cornell–McGuire) hazard analysis consistent with the IGJEO 2021 national hazard maps
Horizontal and vertical elastic spectra to EC8 (S, TB, TC, TD, ag·S, Se,max) Direct input to the structural model and the response-spectrum analysis
Spectrum to KTP-N2-89 (intensity, kE, β, kr, Sa,max) Comparison with the national code still referenced in Albanian practice
Predominant period of the ground TP Check for resonance between the building and the ground
Liquefaction screening Confirms whether the ground needs further liquefaction analysis
Regional seismotectonics and historical earthquakes Active faults, past events and expected maximum magnitude around the site
Guidance on the importance factor γI Values for importance classes II–III (housing, schools, public buildings), with the final choice left to the designer

How we work

  1. Desk study

    Regional geology and tectonics, active fault systems, the earthquake catalogue and previous microzonation studies for the area.

  2. Field survey (MASW)

    A 24-geophone line is laid out across the footprint and surface waves are generated with a hammer source.

  3. Processing

    Dispersion analysis and inversion give the 1D shear-wave velocity profile, which is checked against the borehole stratigraphy.

  4. Hazard analysis

    Probabilistic seismic hazard at rock level for the 95-year and 475-year return periods, with strong-motion records from Albania and the region.

  5. Design spectra

    Ground classification, soil factor and corner periods, then horizontal and vertical elastic spectra to EC8 and the KTP-N2-89 spectrum.

  6. Report & review

    A signed report with document control: prepared, checked and approved by named engineers, with revision history and limitations of use.

MASW: the equipment and the method

MASW (Multichannel Analysis of Surface Waves) records the Rayleigh waves produced by a hammer blow on a line of geophones. Waves of different frequencies travel at different speeds through different depths. Analysing that dispersion and inverting it gives the shear-wave velocity Vs with depth, the direct measure of ground stiffness on which Eurocode 8 classifies the ground. The active survey typically reaches about 30 m depth, exactly the depth Vs,30 requires.

Item Our setup
Seismograph 24-channel seismograph, PASI GEA 24
Geophones 24 geophones, 4.5 Hz natural frequency
Array Geophone spacing typically 1–2 m; line length set by the target depth and the space available; line ends surveyed with GPS coordinates
Source Sledgehammer blows, offset from the first geophone
Recording Typically 2,000 ms record length at 0.5 ms sampling
Processing SeisImager/SW (Geometrics): dispersion spectrum, fundamental-mode picking, inversion to a layered Vs model
MASW survey on site: 24-channel seismograph and geophone line with cable reels
MASW survey on a building site: the 24-channel seismograph in the foreground and the geophone line running across the footprint.
Seismograms recorded on 24 channels during a MASW survey
Raw field record: 24 seismograms showing the surface-wave train arriving later at each geophone along the line.
Dispersion spectrum with the picked fundamental-mode dispersion curve
Dispersion image: phase velocity against frequency, with the fundamental-mode curve picked (red dots).
Inverted layered shear-wave velocity model from MASW
Inversion: the layered shear-wave velocity model that best reproduces the measured dispersion curve.

Why the measured ground type matters

Eurocode 8 does not apply the same earthquake to every site. For the same design acceleration on rock, the soil factor S and the corner periods TB, TC and TD change with the ground type. That changes both the height and the width of the design spectrum. A ground type taken from tables or assumed “to be safe” can overstate the seismic forces and add cost to the structure. It can also understate them, which is worse. Measuring Vs,30 on site removes that uncertainty.

Eurocode 8 elastic response spectra for ground types A to E
Eurocode 8 Type 1 elastic spectra for ground types A to E, normalised to the same design acceleration ag. Softer ground amplifies the motion and stretches the plateau to longer periods, where taller buildings respond.

For every site our report states the measured Vs,30 and ground type and the full set of spectral parameters. It also gives the predominant period of the ground, so the designer can check that the building’s own periods do not coincide with it.

Seismic assessment of existing buildings

For an existing building, the site study is the first half of the job. We combine the site’s seismic action with a survey and testing campaign of the structure and an assessment to EN 1998-3 (knowledge level, confidence factor, linear or pushover analysis). That shows which members fall short and by how much. Where the building needs upgrading, we design and deliver the retrofit; see Structural Strengthening.

Standards and references

  • EN 1998-1 Eurocode 8: seismic actions, ground types and response spectra
  • EN 1998-3 Eurocode 8: assessment and retrofitting of buildings
  • KTP-N2-89 Albanian technical conditions for earthquake-resistant design
  • VKM no. 1162/2020 seismic risk certificate for development and building permits
  • IGJEO (2021) probabilistic seismic hazard maps of Albania
  • Park et al. (2007) MASW, active and passive methods
Planning a new building or checking an existing one?

Send us the site location and the planned building. We’ll confirm the scope, coordinate with the borehole investigation and schedule the MASW survey.

Request a seismic study