Strong Motion Data Products

Please note we are in the process of redeveloping our strong motion data products to improve data access and support for these services. We do not recommend building any automated requests off the current FTP service at this time.

Strong-motion accelerometers are located in major centres of population, near significant faults, or in different types of building structures. They are capable of measuring very strong shaking associated with damaging earthquakes.

The entire New Zealand collection of processed strong-motion data is available from:

There are also summary spreadsheets of the peak ground accelerations for earthquakes with significant ground motions.

Accelerations and spectra response file formats and descriptions are described here.

Descriptions of site conditions may be found in ftp.geonet.org.nz/strong/processed/Docs/site subsurface information.xls.

The New Zealand Strong Motion Database is a collection of strong motion data resources for significant New Zealand earthquakes. It contains source and site metadata, rupture models and strong motion records with component-specific processing. It is intended for scientist and enginneers who are interested in modelling large earthquakes.

Worldwide strong-motion data resources are centralised at the COSMOS Virtual Data Center. This gives access to a database of strong ground motion data parameters, and links to the data centres and web sites of the contributing agencies.

Raw Data

Strong motion is currently recording in a mixture of triggered and continuous modes. Continuous waveforms can be access in the same way as any other seismic data. Triggered data is available via the FTP site. Please note that we intend to move to streaming data at all sites continuously in the future however we intend to provide a way to access segmented data.

Raw data files are available from ftp.geonet.org.nz/strong/raw/Raw, specifically:

Data are organised into yearly directories, and within each year into ordinal date directories. The four-character station codes may be viewed on the network maps, and the site locations and operational dates may be found in DELTA. The data holdings are updated every hour with recent files received from our network. Please note that they may include data from non-seismic sources, such as bumps and electrical interference.

Processed Data

Four levels of processing are routinely carried out on the recorded acceleration time histories, as follows:

Vol1


A header containing information on the earthquake, the recording site and the recorded data is pre-pended, and the data unit is converted to mm/s/s using static sensitivity values. Records from film-recording accelerographs have also been corrected for cross-axis effects and deviations in the sensing-axis directions, which were significant for the mechanical accelerometer block used. Data files in ASCII format and plots, are provided.

Vol2


Full processing is carried out in the frequency domain and includes correction for the dynamic instrument response, high- and low-pass filtering, and integration to give velocities and displacements. Data files in ASCII format and plots are provided.

Vol3


Absolute acceleration response spectra are calculated from the peak responses of linear single-degree-of-freedom oscillators for damping values of 1, 2, 5, 10, and 20% of critical. Relative velocity and displacement spectra are calculated in a similar manner. Data files in ASCII format, and linear plots of the 5% damped spectra, are provided.

Vol4


Plots only of Fourier amplitude spectra.

Notes