Units and very large values in deq_n100a15 (and meaning of ieq_n100a15)

GEMS Prize Challenge
1

Hi

While exploring the numerical features I found something I could not explain in the seismic bands, and I would appreciate a clarification.

Band deq_n100a15 is described as “Distance to earthquake (n=100km radius, a=15° azimuth parameters)”. Inside the valid study area, its values are distributed like this:

  • 1st percentile: 118
  • median: 623
  • 75th percentile: 1,685
  • 99th percentile: 50,237
  • 99.9th percentile: about 1.97 million
  • maximum: about 4.96 million

So 99% of the pixels are below about 50,000, which would fit distances in metres within a 100 km radius. However, about 14,000 pixels (roughly 0.3% of the valid area) are above 500,000, and the maximum would be close to 5,000 km if read as metres, while the study area is roughly 330 x 373 km.

Could you clarify:

  1. What is the unit of deq_n100a15, and how is it computed? In particular, what do the n=100km and a=15° parameters mean?
  2. Are the very large values expected (for example, a fill value for pixels with no earthquake within the radius), or could they be a data issue?
  3. What does ieq_n100a15 (“Earthquake intensity or density”) measure, and in what unit?

Thanks!!

1 Like
2

Hi @Pablo_Sicilia -

Those bands are the INGENIOUS earthquake rate density layers that have been clipped to the GeoDAWN area and re-gridded to 100m. For more detailed information, you can look at the original dataset on the INGENIOUS site (download “Earthquake Density Models.zip”, extract it, then look at eq_rate_density_details.docx).

-Chris