# EARTHWORM Status Report

##### `Alex Bittenbinder (alex@gldage.cr.usgs.gov) Sep. 9, 1998`

#### Previous Status Notes are available for:
Sep 1998
Feb 12, 1998
May 5, 1998
May 19, 1998.

## I. Event Archiving - so what are we going to do about it?

Earthworm started life as a rapid notification system. The objective was to produce the fastest and most reliable notification of a significant event. As a result, we labored to get ever closer to 'the now' - seconds became crucial, and hours became irrelevant. However, this was not to last. Our mission has changed, and we're being urged to extend Earthworm's attention span back into time to include processing of late-arriving data, event archiving, and interactive analysis. One obvious approach is to attach a commercial data base management system (DBMS) to Earthworm, and use it to store the various real-time outputs; then attach an interactive analysis system to the DBMS. The argument for using a full-blown, commercial DBMS is that these products have matured and have solved the basic problems associated with handling large sets of data (performance, crash recovery, distribution, web access, concurrency, integrity, archiving, platform independence, etc). This has been done as part of our DBMS PhaseII effort, using Earthworm, Oracle, and SAC. (see below).

Another approach is to say that DBMS's are overkill: They're complex, expensive, hard to understand, require overpriced specialists, and devour valuable personnel time. Other than in areas of very high seismicity, commercial DBMS's are an exotic solution to a not-so- exotic problem. In response to this argument, We have worked toward making the DBMS "removable", in that it can be replaced by a 'flat-file' scheme using the operating system's file system. The result is that Earthworm then creates an archive of event directories in a chosen format(s). Two such systems are in operation, producing UW2, SAC and AH archives.

## II. The Earthworm and the Database:

A subset of the Earthworm development team has been playing with data bases. The effort is structured into three phases: PhaseI (completed) was an exploration of various products. PhaseII (mostly completed) was to produce a minimalist but functioning lashup involving Earthworm, an Oracle DBMS, and an interactive analysis system (SAC). PhaseIII, (about to start) is to produce a full-featured multi-node system capable of serving an extended geographic area with a variety of features for strong and weak motion.

PhaseII has been in testing for over a month, and appears to be doing well. Briefly, it consists of an Earthworm inserting hypoinverse parameters and the associated trace data segments into an Oracle DBMS in real-time (as outlined below). It also offers a web-based interface which allows the user to specify and view event lists, event maps, event parameters, and soon, images of trace data. The user may select events for further analysis via checkboxes on the web page. This causes the system to retrieve the specified event data from the DBMS, generate the implied SAC directories, and create some SAC macros which offer a modest quick-look, production environment. SAC has been used as a demonstration analysis system. Other analysis systems can be integrated, as outlined below. A more comprehensive PhaseII document is being prepared.

## III. Dawn at Memphis:

CERI at Memphis recently received a massive infusion of energy in the form of Mitch Withers. The result has been that CERI is now our most active 'power user', rapidly moving toward operating several remote unattended Earthworm nodes communicating with a central site, using the distributed feature of CarlTrig (below), and about to become the first customer/patron of the PhaseII effort. Mitch was kind enough to respond to a request for a brief statement of his status and plans:

    Center for Earthquake Research and Information (CERI)
    University of Memphis                Ph: 901-678-4940
    Memphis, TN 38152                   Fax: 901-678-4734

CERI has recently upgraded their DOS/Solaris earthworm to NT/Solaris v3.2. Significant changes were made to the pick_ew and binder config files to reflect the geology and seismicity of the Central U.S. They have also employed carltrig and are nearing completion of a trig2disk module that listens for trigger messages and writes appropriate waveform files to disk in either sac or ah data format. This provides three methods for recording waveforms: event and waveforms produced by eqproc->arc2trig->trig2disk; more conservative triggered data produced by carltrig- >trig2disk; infinitely conservative continuous waveforms produced by wave_serverV and accessible via earth2sac (earth2ah is under development). CERI will deploy the Guralp to earthworm module, soon to be released by UofA, to integrate data from a network of 11 CMG40t's

Telemetry limitations require CERI to operate multiple, autonomous, remote processing nodes. Conversion of these nodes to earthworm is ongoing. The final configuration will consist of at least three nodes and a central processing facility at Memphis. TCP/IP communications between the nodes and Memphis is established via ISDN telephone. Thus communication must be minimized to avoid excessive long-distance charges (e.g. trace_buf packets are not continuously fed the central facility). Only least conservative event and waveform information is transferred to Memphis for rapid review and dissemination (more conservative triggers are transferred using alternate methods). Node processing systems are robust, start earthworm at boot, and allow remote reset. Plans are in development to operate these nodes as a National Seismic System prototype. The eastern Tennessee network is operated jointly with UNC Chapel Hill and forms another leg to the prototype.

## Earthworm Enhancements:

We've been working on a number enhancements to Earthworm to support event processing:

### 1. Wave Server:

As documented elsewhere, this module maintains a circular, disk-based memory of trace data, and provides a multi-user TCP service on the Internet. This module is capable of serving selected segments of trace data up to weeks into the past (two Gigabytes per channel). It can be run as part of any earthworm system, and can be accessed by any client software anywhere on the Internet. A set of client-side routines are available to ease the chore of writing client software.

### 2. Event Triggers:

We have instituted the idea of an 'event', and a trigger message type (TYPE_TRIGLIST). The idea is that some 'trigger' module (or interactive program) can decide that an event has occurred and broadcast such a message. The message specifies the "Event Number", the "Author" of the event, the event time, and a list of participating trace channel names ( 's). For each such participating channel, a station trigger time, and the time interval of interest ('snippet') is specified. See "sample_trig.txt". At present there are three such trigger modules: 'arc2trig', which generates a trigger message when it receives a hypoinverse 'arc' message, 'CarlTrig', which is a distributed version of Carl Johnson's venerable STA/LTA trigger algorithm, and 'EvansTrig', a port of John Evans' long-period volcanic trigger.

The "Author" of an event is an ASCII string identifying the creator of the event. It solves (postpones?) the problems of tracking multiple sources of events. In the case of trigger messages, the "Author" is the ASCII representation of the logo ( ) of the module (STA/LTA, hypoinverse...) which created this event.

The "Event Id" of a message is a sequential integer maintained by the module creating the event. Event numbers are written to disk, and continue sequentially across system restarts.

Note that the station name in a 'snippet' specification may include wildcards (*'s) in any of the three fields. The result is that all channels of that descriptions (available from the WaveServer's at the time of the event) will be incorporated into the event archive, as described below.

### 3. xxTraceSave:

We have also produced a module called 'xxTraceSave'. This module listens for TYPE_TRIGLIST messages produced by some trigger module, retrieves the trace data 'snippets' specified in the trigger message, and calls a set of standard (almost) routines to reformat and store this data (the PutAway routines). The idea was that one could then write a set of such 'PutAway' routines for a given format, and thus create a new variant of xxTraceSave. To date this has been done for SAC, Oracle DBMS, UW2, and AH.

On startup, xxTraceSave is given a list of WaveServer addresses via its configuration file. When it receives a trigger message, it calls the 'PutAway' initialization routine with the Event Number and Author found in the trigger message. This routine presumably does whatever is required to create a new event in the 'xx' format. After that it runs down the list of participating stations in the trigger message, and attempts to retrieve the specified 'snippet' of trace data from the WaveServer's it was told about. When it receives such a snippet, it calls the 'PutAway' routine for adding another trace to that event. Presumably, this routine tacks this piece of trace, and the associated parameters, onto the event in 'xx' format. When all such snippets have been processed, the 'PutAway' end-of-event routine is called, which does whatever is required to 'close' the event in 'xx' scheme.

The current version of this module has the ability to wait for data. Conceivably, a trace snippet from a distant station (at some network far away) may be requested before the seismic waves have reached the sensors. The strategy is to obtain all possible trace snippets as soon as the message is received, to then wait for the 'stragglers' to come in, and to then retrieve the 'stragglers'. There is a timeout which will close the event unconditionally. There are also timeouts to prevent a sluggish WaveServer from paralyzing the process.

At one point there was the hope that the 'PutAway' routines could be standardized, and that merely linking in a new set would result in a new member of the 'xxTraceSave' family. This did not happen. There were enough idiosyncrasies amongst the various formats so that defining an all-inclusive set of 'PutAway' calls got to be more trouble than it was worth. The result is that the xxTraceSave family now enjoys a correct degree of diversity. As mentioned above, versions for Oracle (ora_trace_save), UW2 (earth2uw), SAC (earth2sac), and SAC-AH (trig2disk) are currently in operation at Seattle, Menlo Park, and Memphis.

### 4. CarlTrig

This is a port of Carl Johnson's venerable STA/LTA trigger algorithm. It generates events based on coincidence of station triggers based on STA/LTA ratios, as per Carl's thesis. It's main virtues are a long and stable history, the ability to detect most any kind of event, and considerable flexibility in tuning. We've added the ability to operate the algorithm on a network with distributed Earthworm nodes: The algorithm consists of two modules: CarlStaTrig computes the STA/LTA averages for a set of local stations, and generates station trigger messages when a station detection occurs. These messages can then be shipped to a central Earthworm, where they are listened to by the CarlSubTrig module. This module receives the individual station trigger messages and performs the sublet-coincidence logic. When this logic declares a network-wide event, a trigger message (TYPE_TRIGLIST) is broadcast.

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