Up to date information can be found on http://www.nanoseismic.net.
Data is read in the Center for Seismic Studies (CSS) and MiniSEED format. In CSS data files must be referenced by an ASCII header file. It contains all necessary access information for each station and each component. The referenced time periods may range from some minutes for single events up to several hours or days for continuous recordings, there is no upper limit for the NanoseismicSuite. Furthermore parameters about the campaign and stations used for the data are stored in the knowledgebase.
We expect the signal output of geophones where voltage is proportional to ground velocity. Calibrating ADC counts to true ground velocity by the factor calib is based on a value which is specified in the plateau or at the corner frequency of the transfer function; in any case it must not be in the decaying part below the corner frequency. However, to conform to CSS header file definitions we demand the specification of a factor calibm [nm] which is valid for ground motion and got specified at period calper [sec]. The internally used calib is derived from calibm by multiplying the latter with and dividing it through calper. When any of these two values is zero, no calibration is performed; instead digital counts are displayed. [Optional: calib *= lsbfak to correct where 1 ADC count >1.0 of unscaled data, e.g. Lennartz M24.]
The header file can be created automatically from raw data in MiniSEED, SEG2 or Lennartz M24 digitizers and a default knowledgebase is created automatically on application startup if it does not exist. Changes to the knowledgebase can be made from the knowledgebase editor of SeisServ or directly in the corresponding XML files.
Furthermore IRIS (http://www.iris.edu) provides the tool rdseed (http://www.iris.edu/forms/rdseed_request.htm) which can convert SEED data records directly into the CSS format IRIS also provides multiple converters for ASCII, GGP, GSE, MARS, MT, SAC and SEISAN into the MiniSEED format (http://www.iris.edu/pub/programs/converters/) which in turn can be read by the NanoseismicSuite. This way it is possible to view almost all datasets in the NanoseismicSuite without the manual creation of a header file.
The header file must contain information about start time, station and component, #samples, sampling rate, calibration factor and period, type of binary data representation, filename and path. The byte offset is used to store two or more waveforms in one file. This feature is mostly used for bridging shorter data gaps or compiling three-component and small array data. The NanoseismicSuite supports the decoding of header files conforming to the standards of the Center for Seismic Studies (CSS) - now: Center for Monitoring Research (CMR) in Arlington, VA. Two slightly different database structures, Version 2.8 and Version 3.0, are supported as well as our own, non-standard format derived from it. The latter is called Short Format and restricts the header content to just the necessary information. An overview of the different header file types is given in table 4.1.
All header parameters are shown in listing 4.1. Table 4.2 shows an explanation of all short header parameters, 4.3 shows the supported binary file data types and listing 4.2 shows an example of all parameters. The entry for directory can be absolute as well as relative. All reference to time is exclusively done via epoch while the entry date is optional to ease human orientation. Some parameters in the original CSS header formats are of no interest here; they are marked by "-".
|date||Start day, first 4 digits (year), following 3 digits (day of the year)|
|epoch||Start time as unix timestamp (seconds after 1970/01/01)|
|nsamp||Number of samples|
|calibm||Amplitude scale factor|
|calper||Period scale factor|
|dattyp||Data type, see table 4.3|
|byte-offset||Byte offset in data file|
|i2||INTEL short integer||Little endian||CSS equivalent|
|i4||INTEL long integer||Little endian||CSS equivalent|
|s4||SUN long integer||Big endian||CSS equivalent|
|f4||INTEL single precision real||Little endian||CSS equivalent|
|t4||SUN single precision real||Big endian||CSS equivalent|
|d0||Ascii float numbers in columns||Offset: lines|
|m4||Mini-SEED format||Big Endian||Steim1-compressed 4kB blocks|
|m1||Mini-SEED format||Big Endian||Steim1-compressed 1kB blocks|
|m5,ms||Mini-SEED format||Big Endian||Steim1-compressed 512B blcks|
|m42||Mini-SEED format||Big Endian||Steim2-compressed 4kB blocks|
|m12||Mini-SEED format||Big Endian||Steim2-compressed 1kB blocks|
|m52,ms2||Mini-SEED format||Big Endian||Steim2-compressed 512B blcks|
|nx||Nanometrics X5 format||Little Endian||Steim1-compressed 4kB blocks|
|pd||Geotech PDAS 100||Little endian||14+2 bit gain ranged|
Further meta data of a measurement campaign is stored in the knowledgebase. The parameters of the knowledgebase are stored in the following two XML files in the subdirectory knowbase below the directory of the header file:
In table 4.4 are all campaign parameters explained. In listing 4.3 is the source of an example campaign.xml file with all parameters.
|campaign name||The name of the campaign|
|campaignstart||The date and time of the campaign start (format: yyyy/mm/dd hh:mm:ss)|
|campaignend||The date and time of the campaign end (format: yyyy/mm/dd hh:mm:ss)|
|globalsamplerate||The sample rate which should be used in all applications|
|latitude||The latitude of a reference point used later for the positions of the stations|
|longitude||The longitude of a reference point used later for the positions of the stations|
|height||The elevation of a reference point used later for the positions of the stations|
|halfsize||Scale of epimap in HypoLine|
|x-offset||The longitude offset for the campaign location|
|y-offset||The latitude offset for the campaign location|
|layerModel name||The name of the layer model|
|layerModel ratio||P-velocity to V-velocity ratio of layer model (vP/vS)|
|layer vP||P-velocity of layer|
|layer d||Thickness of layer|
|layer wavetype||Wavetype of layer (Pg, Pn, Unknown)|
In table 4.5 are all stations parameters explained. In listing 4.4 is the source of an example stations.xml file with all parameters.
|sns id||The SNS name|
|north,west,east,center id||The station name (must be the same as stat from header file)|
|x||The longitude position relative to the referencepoint + offset|
|y||The latitude position relative to the referencepoint + offset|
|z||The elevation relative to the referencepoint|
|static||Not used yet|
|clock||Not used yet|
|traceZ||The vertical component of a station|
|traceEW||The horizontal east-west component of a station|
|traceNS||The horizontal north-south component of a station|
|active||switch to turn station/SNS on (true) or off(false) in SonoView|
If data is already available in the CSS format, the header file can be directly loaded from within SeisServ with the Load Data button. If data is available in MiniSEED, SEG-2 or Lennartz M24 data format, a header can be created within the same dialog. For further information see the SeisServ section 5.0.1.
If the data is successfully loaded, SeisServ shows for every trace the name, start and end time as in figure 5.2.
After loading data, SonoView can be started from Menu Tools SonoView. SonoView is shown in figure 5.3. From within SonoView, TraceView can be started from Menu View Show TraceView. TraceView is shown in figure 5.4. Both SonoView and TraceView are by default started automatically. HypoLine can be started from Seisserv Menu Tools HypoLine and is shown in figure 5.5.
Configurations of all applications are saved in the user directory of the current user in a subfolder nanoseismicsuite.
SeisServ reads seismic data and meta-data, it provides this data to the other modules and allows editing of the meta-data, e.g. the geometry of seismic stations.
SeisServ supports two modes of header loading, database and file based. Furthermore, headers for raw data in MiniSEED, SEG2 or Lennartz M24 digitizers can be created. All of the above are available from the "Load Data" dialog.
Figure 5.6 shows SeisServ with some explanations. In figure 5.7 and figure 5.8 the campaign and stations knowledge base editor is shown. SeisServ provides data for SonoView and TraceView and manages the knowledge base. It is possible to change or create a knowledge base in SeisServ with the knowledge base editor accessible from the button Knowledgebase.
Configure and test connection as shown in Figure 5.9 with appropriate values.
Explanation of options is as follows:
Load data as shown in Figure 5.9. The data from the database can be filtered by dates, campaigns and stations:
After loading the data, SonoView is the first application to use in a typical event screening scenario. It visualizes super-sonograms in a manner to maximize the visible data on one screen. An arbitrary amount of SNSs and time spans can be loaded. An analyst can scroll fast through the continuous data in SonoView and mark suspicious events for further processing steps. Figure 5.11 shows SonoView with some explanations.
The preferences dialog can be reached from the Main Menu File Preferences. It is shown in 5.12.
The preferences are:
The View options are in the Main Menu View.
All options can also be called with keyboard shortcuts which are also shown in the help menu (reachable by F1), see figure 5.13.
All options can be called with keyboard shortcuts which are shown in the help menu (reachable by F1), see figure 5.15.
HypoLine allows a detailed analysis of events.
It is used for the localization and magnitude estimation. Localization is
done by time difference of arrival (TDOA) hyperbolae and S-P distance circles
based on one-dimensional velocity models. HypoLine supports at the moment the processing
of data from up to six SNSs which it gets from TraceView.
This subset of SNSs is no restriction for weak events because they are anyway only visible
at the surrounding stations. For further processing of single events tools as
e.g. Geotools, Seisan, Pitsa or SeismicHandler can be used. HypoLine allows
a first coarse localization and identification with interactive and graphical techniques
for very weak events.
Screenshots are given in figure 5.16, 5.17 and 5.18.
All options can be called with keyboard shortcuts which are shown in the help menu (reachable by F1).
For further information on HypoLine:
In figure 6.1 the typical layout of one SNS is shown. One three-component station in the center and three one-component vertical stations deployed as a tripartite array. This guarantees the optimal recording.
Sonograms are spectrograms of seismic signals with the following properties:
In figure 6.2, the processing steps of a sonogram are shown. The horizontal axis is the time domain and the vertical axis is the frequency domain. The frequency domain is logarithmically scaled. As the spectrogram is a 3-dimensional plot, the power of each pixel is shown as a coloring based on the shown color map.
SonoView shows super-sonograms, which are explained in figure 6.3. The super-sonograms combine all four vertical traces of one SNS into one diagram. It uses each pixel of the normal sonograms to form a super-pixel. With these super-pixels a new sonogram is built. This allows to see the recording of one SNS in one row and check on array wide signal coherency.
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