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Here are some of the articles that have been recently posted to the PASSCAL website:

August/September 2009 New Mexico Earthquake Swarm in the Central Rio Grande Rift

Courtesy Jana Pursley, NMT

Seismicity in central New Mexico, southwestern United States, is dominated by earthquakes occurring above the mid-crustal Socorro Magma Body (SMB). The SMB is a sill-like feature ≥ 3400 km2 in area, with a top surface at 19-km depth spanning the inner Rio Grande rift half-graben system. Inflation of the magma body at rates of several mm/year, perhaps coupled with shallow transport of aqueous fluids, is the prevailing model for the region’s long-standing and anomalous seismicity. Clustered swarms of small magnitude earthquakes have been noted since the 1860s throughout this region, and have been recorded instrumentally since the early 1960’s (Figure 1, blue squares, Sanford et al., 20021).

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Batholiths Onland 2009 Photo Recap

In July 2009, several IRIS/PASSCAL scientists assisted with the Batholiths Onland project. This large group effort involved over 50 scientists and grad students, for the purpose of making "a seismic refraction and wide-angle reflection survey across the Coast Mountains batholith of British Columbia, Canada."

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Workshop Agenda

PASSCAL Data Archiving Workshop San Francisco, California Gallery Room, Palomar Hotel December 13, 2009 Preliminary Agenda Agenda contents and schedule subject to change. updated 9/18/09

Morning Session: Passive-Source Processing and Data Archiving

Nanometrics Trillium 240 Polar Sensor

Nanometrics Trillium 240

The Nanometrics Trillium 240 is a symmetric triaxial broadband instrument that has a flat response to ground velocity between 240s and 200Hz, and has a low self-noise, below the New Low Noise Model between 100s and 10Hz.  The manufacturer specifications of operating temperatures are between -20C and +50C, but the Trillium 240 has operated reliably for us to temperatures below -60C.  The power consumption at low seismic noise conditions and with the instrument well leveled is about 650mW.  The Trillium has a +/-1deg tilt tolerance, is fairly sensitive to varying temperature, but was designed to be insensitive to atmospheric variations.

The Trillium 240 is well suited for medium to long term experiments in the Arctic and Antarctic supported by the IRIS PASSCAL Polar Program.

Logpeek Example Illustrating the SiRF Timing Problem

Example of LOGPEEK display of a recent RT130 logfile with a SiRF clock attached, illustrating the timing problem. Note the DSP-CLK DIFF and JERKS/DSP SETS points.

DSP CLOCK DIFFERENCE -1 SECS and 0 MSECS messages mark the beginning of timing errors in the RT130 data, due to the SiRF clock’s erroneous time shift. The SiRF goes back and forth between correct and incorrect time over periods of hours or days. The RT130, and hence your data, will follow suit, generally with a lag of 4 hours.


‘POSSIBLE DISCREPANCY’ messages will be produced whenever the SiRF and the RT130 are not in sync. Four consecutive ‘POSSIBLE DISCREPANCY’ messages will reset (JERK) the RT130 time.

If the clock is being power cycled, the clock is locking and the RT130 is phase locking with the SiRF each time it is powered, the 4-hour lag is produced.

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Polar Project Sample Deployments

Here are articles on several recent Polar Project Deployments: Polenet Mevo

Summer Only Enclosure for Polar Projects

Here are several documents regarding summer-only equipment for Polar Projects. Batteries DAS Power Sensors Solar Station Enclosure Vaults

Specialized Polar Equipment

The Polar Program of IRIS/PASSCAL is dedicated to supporting with seismological research in the Arctic and Antarctic.  As opposed to traditional seismic stations installations around the world, instrumenting the Arctic or Antarctic require special consideration due to the extreme nature of the climatic conditions, temperature being the primary challenge.


A datalogger (also know as data acquisition system or DAS) is piece of electronic equipment which converts an input into a digital time series representation. Immense care should be taken when setting up and programming a datalogger. It is highly recommended that only experienced users program their own dataloggers and all others should consult a PASSCAL staff member for assistance.

While specific procedures and programming details will vary between the various types of dataloggers, there are several things that hold true when working with any datalogger.

The datalogger should be:

Governing Policies

A variety of policies govern the use of PASSCAL and EarthScope Flexible Array equipment, and the support provided by the PASSCAL Instrument Center. These policies are vetted by the PASSCAL Standing Committee and the USArray Advisory Committee (see for more information about IRIS govenance and committee membership and charge). Links to PASSCAL policies are listed below:

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