The Searchable Product Depository (SPUD) is the IRIS DMC's primary data
product management system. Complementing the DMC's SEED and assembled
data archives, which contain time series recordings, the SPUD system
primarily contains derivative data products of other types (images,
movies, etc.) created either at the DMC or by members of the community.
For users SPUD is the query and access point for these products. The
web interfaces allow users to search for products using customized queries
across product and event details. Users can search across all product
types at once or within specific product types. SPUD also has web service
interfaces for programmatic discovery and access to the data products.
If any products from SPUD are used in your research please be sure to cite
the identified author of the product and the IRIS DMS
[Citation Information].
About EMTF products
The EMTF data product contains magnetotelluric (MT) transfer functions (TFs), which
define the frequency dependent linear relationship between
components of electromagnetic (EM) field variations measured at a single
site. Two sorts of TF are provided for most sites: 2x2 impedance tensors,
and vertical field TFs, which respectively relate
horizontal electric and vertical magnetic components (the
outputs in the TF relationship) to
the horizontal magnetic field vectors (the corresponding inputs).
Note that for some sites only impedances are provided.
All of the TFs, which can be justified
if external source fields are quasi-uniform (varying over length scales that
are long compared to the skin depth), provide input data for
subsequent MT inversion and interpretation.
They are estimated from the raw EM time series
by (a) Fourier transforming data in a series of
short overlapping time windows, and (b) applying robust regression methods
to the resulting sequence of Fourier coefficients. For remote reference
estimates data from a second site are used for noise cancellation, and to
reduce bias due to noise in the predicting magnetic channels. Apparent
resistivities and phases, which can be computed from the off-diagonal components of
the impedance tensors, are frequently used in 2D interpretations.
The EMTF data product includes estimates of the TFs for a range
of periods (which may vary, depending on instrumentation and deployment
time), as well as estimation error covariances.
Product Query Help
This page queries for EM Transfer Function products.
Click on row in query results to view item detail.
Column headings control sort order of results.
Use map to constrain latitude and longitude.
Max and min latitude and longitude can be entered in the corresponding text fields.
Markers on map can be clicked for details and will link to item detail page.
Start and end dates are specified by clicking on date entry fields to enable date selector.
Or use popup calendar to select date by clicking on calendar icon next to date fields.
Clear button removes all selection criteria
Download button will return a zip file containing all items matching current
criteria or only selected items (if any are selected via leftmost column)
Citing EM_TF Products
When citing this particular Magnetotelluric Transfer Function, please cite based on the "Citation Info" panel of this page.
To cite the Magnetotelluric Transfer Function database at IRIS, please use the instructions at:
