Selection of La Habra Ground Motion Observations

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The La Habra Earthquake was a well recored earthquake. We have selected a set of ground motion data for use in validation of our ground motion simulation results.

La Habra Data Sets

We have identified five possible sources of observational data for the La Habra Event. Current site list is based on the first two data sets. Additional data from the other data source may be added latter:

  1. StrongMotion.Org La Habra Data
  2. SCECDC Test Events For EEW and General Seismic Algorithm Testing

We are assuming the two data sets above include a high percentage of the available, high quality observations for this event. If additional observational data is need, places to check include:

  2. PEER Strong Motion Database
  3. IRIS Data Management Center

StrongMotion.Org (SMO) Observations

As of 28 March, the strong site has collection of strong motion data in Cosmos format for the La Habra Mw5.1 earthquake. They also have data for an aftershock.

  1. StrongMotion.Org La Habra Data
  2. La Habra Site Table SMO

The [] site gives a list of years, select 2014, and they give you a list of earthquakes. Pick the lower caps, lahabra event, and you get to a selection page, giving list of station, information about the records, and information about whether there are structure recordings.

When a station is selected, the users selects processed, or unprocessed. We select processed. When we get a Zip file, it typically contains two file V2 and V3. The V2 file contains a header indicating the instrument type. For all SCSN, we see HN data (example. SCSN Station WLT: HN data, SCSN Station: , indicating strong motion accelerometer data. The V2 files seem to contain the time series. However, parsing is complicated because the files may contain structure response information time series as well.

After processing the event data table:

Based on contents of .V2 files, these StrongMotion.Org data are accelerometer data, channel type HN, so we will assume any CI STAT HN data is a duplicate of what we have from strong This is an assumption of what we get from SMO. Once we retrieval all the seismograms, we do not know if this is a good assumption. If not, then some strong motion data are not HN, so we may want to include HN from SCECDC. For now, drop an SCECDC HN as duplicate of SMO data, if network, station match.

SCEC Data Center (SCECDC) Observations

We found another collection of La Habra data in the SCEC Data Center. This is data for EEW and Seismological Algorithm Testing. These station lists are broken out by network, station, instrument, component. We will do two passes to identify that channels this adds to the set.

Based the directory manifest file, this file has a header then list of network, channel, instrument. The channel naming used by SCECDC distinguishes between FBA channels (m/sec2) [HN] and velocity sensor (m/sec) [HH] by the first two characters. For the first pass, we will select only FBA channels for Caltech.

Merged (SMO + SCECDC) Observation Lists

Before reviewing each seismogram, we assume all stations have signal within the simulation region. Then, merging the SMO and SCECDC La Habra Event Data Set, using only acceleration instruments within the simulation region:

The sites were we have overlapping data, where we can get seismograms from both sources, gives us a way to cross check our ground motion processing is consistent. The overlapping stations are:

Comparing Ground Motion Data

This merged data set, we will require we manage two types of observational data. The SMO data will be in the processed V2 cosmos format. The SCECDC data will be in SEED format, probably unfiltered and in counts. SCEDC data in Counts will need to be converted to acceleration using a gain factor in a metadata file posted on the data download site.

We will consider all the SMO as consistently processed Observational Sites. We need to confirm our processing of the SCEDC event data, and compare our signal processing between data sets for some of the overlapping data sites where we have both SMO data and SCEDC data.

These data will be obtained from two data sources:

All the SMO La Habra sites (In Cosmos format): 309

SCECDC Only Sites: 47

Earlier La Habra Station Lists

Previously contributed station lists from earlier work. We've reviewed this lists to be sure all stations mentioned in these site lists are included in our merged list above:

An earlier site list, that provides station and location information.

Seismological Software Links

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