ISIS station review meeting on May 19, 2011. Jim, Chris, Dave, Holly, and Mitch.

Many components for the current ISIS hardware are no longer obtainable and many of the stations are showing signs of their 15+ year age. That combined with the loss of 9 stations to the 2011 flood compels us to develop a next generation ISIS shortperiod analog station.

Some requirements for ISIS3 include:

Flooded stations are the priority for repair/upgrade. They are EPRM, CATM, GOBM, CWPT, HDBT (anss freefield/reference site), MIST, MORT, TNMT, and HCAR.

This is the list of stations with number of p and s arrivals used in NM catalog locations since 2000.

Map of NMAD area stations with number arrivals used in NM catalog locations since 2000.

Map of LNXT area stations with number arrivals used in NM catalog locations since 2000.

Map of MKTA area stations with number arrivals used in NM catalog locations since 2000.

Summary of stations to be decommissioned, moved, or investigated:

Jim also pointed out that the repeater for HOVM, BFAR, and DLAR is now located on the luxo tower so the map should be updated.

When asked for advice on the upgrade, and gain ranging specifically, Bob Smalley had this to say:

One has to answer the question "What does one want to do with seismic data from New Madrid" to answer the question of how to "fix" the network. One could join the rest of the seismological community "group think" - that we know everything there is to know from small events, recorded on low dynamic range, analog systems and put in one "real" seismic station for each 10 ISIS stations that need repair. This will also reduce the number of events to locate and stations to maintain, requiring less staff.

One could go with a non-gain ranged ISIS to solve the problem of not being able to signal process the gain ranged data (but I don't know how to signal process clipped data either). The gain ranging was introduced to allow S readings to obtain higher quality locations over a wider magnitude range of events than was available without gain ranging. With the existing broadband component of the network, this may not be necessary as one can get a some S information from the broadbands when the ISIS stations clip. It depends on how important one thinks locating the earthquakes are. Do we know everything about the fault geometries, activity rates, etc. that the smaller events tell us?

As for autopickers - sounds like a job for a graduate student. It should not be that hard.

As for serving up data to the world - offer it both ways - raw and degained and make it very clear that the degained data is not valid for signal processing (at least around the gain steps).

We locate about 200 events a year (at least that's the number I hear Gary bandy about). If we do away with the gain ranging, how will that impact this number? If we set a single gain at the lower gain setting, we will loose the (assumed unimportant) small events, which are the most numerous. If we set a single gain at the higher gain setting, we get all the little events well located, but have poorer locations for the more important larger events.

It is probably a waste to put a 24 bit digitizer on an L-28 anyway since an L-28 only has ~90 db of dynamic range.