scmag

Calculates magnitudes of different types.

Description

The purpose of scmag is to compute magnitudes from pre-computed amplitudes. Instead it takes amplitudes and origins as input and produces StationMagnitudes and (network) Magnitudes as output. It does not access waveforms. The resulting magnitudes are sent to the “MAGNITUDE” group. scmag doesn’t access any waveforms. It only uses amplitudes previously calculated.

The purpose of scmag is the decoupling of magnitude computation from amplitude measurements. This allows several modules to generate amplitudes concurrently, like scautopick or scamp. As soon as an origin comes in, the amplitudes related to the picks are taken either from the memory buffer or the database to compute the magnitudes.

Relationship between amplitudes and origins

scmag makes use of the fact that origins sent by scautoloc, scolv or other modules include the complete set of arrivals, which reference picks used for origin computation. The picks in turn are referenced by a number of amplitudes, some of which are relevant for magnitude computation.

Read the scamp documentation for more details on amplitude measurements.

Primary magnitudes

Primary magnitudes are computed from amplitudes and station-event distances. Currently the following primary magnitude types are implemented.

Local distances

Md

Duration magnitude as described in HYPOINVERSE (Klein [19]).

Mjma

Mjma is computed on displacement data using body waves of period < 30s.

ML

Local (Richter) magnitude calculated on the horizontal components using a correction term to fit with the standard ML (Richter [25]).

MLc

Local custom magnitude calculated on the horizontal components according to Hessian Earthquake Service and Stange [29]

MLh

Local magnitude calculated on the horizontal components according to SED specifications.

MLv

Local magnitude calculated on the vertical component using a correction term to fit with the standard ML.

MLr

Local magnitude calculated from MLv amplitudes based on GNS/GEONET specifications for New Zealand (Ristau et al. [26]).

MN

Nuttli magnitude for Canada and other Cratonic regions (Nuttli [22]).

Teleseismic distances

mb

Narrow band body wave magnitude measured on a WWSSN-SP filtered trace

mBc

Cumulative body wave magnitude

mB

Broad band body wave magnitude after Bormann and Saul [14]

Mwp

The body wave magnitude of Tsuboi et al. [30]

Ms_20

Surface-wave magnitude at 20 s period

Ms(BB)

Broad band surface-wave magnitude

Derived magnitudes

Additionally, scmag derives the following magnitudes from primary magnitudes:

Mw(mB)

Estimation of the moment magnitude Mw based on mB using the Mw vs. mB regression of Bormann and Saul [14]

Mw(Mwp)

Estimation of the moment magnitude Mw based on Mwp using the Mw vs. Mwp regression of Whitmore et al. [31]

M

Summary magnitude, which consists of a weighted average of the individual magnitudes and attempts to be a best possible compromise between all magnitudes. See below for configuration and also scevent for how to add the summary magnitude to the list of possible preferred magnitudes or how to make it always preferred.

More details are given in the section Summary magnitude.

Mw(avg)

Estimation of the moment magnitude Mw based on a weighted average of other magnitudes, currently MLv, mb and Mw(mB), in future possibly other magnitudes as well, especially those suitable for very large events. The purpose of Mw(avg) is to have, at any stage during the processing, a “best possible” estimation of the magnitude by combining all available magnitudes into a single, weighted average. Initially the average will consist of only MLv and/or mb measurements, but as soon as Mw(mB) measurements become available, these (and in future other large-event magnitudes) become progressively more weight in the average.

If an amplitude is updated, the corresponding magnitude is updated as well. This allows the computation of preliminary, real-time magnitudes even before the full length of the P coda is available.

Station magnitudes

Station magnitudes of a particular magnitude type are calculated based on amplitude values considered by this magnitude type and the distance between the event and the station at which the amplitude was measured. Typically, epicentral distance is used.

Note

Usually station magnitudes use amplitudes of the same type. However, some magnitude consider amplitudes of another type. E.g. MLr uses amplitudes computed for MLv.

Network magnitudes

The network magnitude is a magnitude value summarizing several station magnitudes values of one origin. Different methods are available for summarizing the station magnitudes:

• mean: the usual mean value

• trimmed mean value: To stabilize the network magnitudes the smallest and the largest 12.5% of the station magnitude values are removed before computing the mean.

• median: the usual median value

• median trimmed mean: Removing all station magnitudes with a distance greater than 0.5 (default) from the median of all station magnitudes and computing the mean of all remaining station magnitudes.

Default values apply for each magnitude type. In scolv the methods, the stations magnitudes and other parameters can be selected interactively.

Summary magnitude

scmag can compute a summary magnitude as a weighted sum from all available network magnitudes. This magnitude is typically called M as configured in summaryMagnitude.type.

It is computed as a weighted average over the available magnitudes:

The coefficients a and b can be configured per magnitude type by summaryMagnitude.coefficients.a and summaryMagnitude.coefficients.b, respectively. Furthermore each magnitude type can be specifically added to or excluded from the summary magnitude calculation as defined in summaryMagnitude.whitelist or summaryMagnitude.blacklist, respectively.

Note

While the magnitudes are computed by scmag the decision about the preferred magnitude of an event is made by scevent.

Preferred Magnitude

The preferred magnitude of an event is set automatically by scevent or interactively in scolv. It can be any network magnitude or the summary magnitude.

Configuration

etc/defaults/global.cfg

etc/defaults/scmag.cfg

etc/global.cfg

etc/scmag.cfg

~/.seiscomp/global.cfg

~/.seiscomp/scmag.cfg

scmag inherits global options.

magnitudes

Type: list:string

Definition of magnitude types to be calculated from amplitudes. Default is MLv, mb, mB, Mwp.

connection.sendInterval

Type: int

Interval between 2 sending processes. The interval has influence how often information is updated. Default is 1.

connection.minimumArrivalWeight

Type: double

The minimum weight of an arrival to be used for magnitude calculations. Default is 0.5.

Note

summaryMagnitude.* The summary magnitude is building a weighted summary above all defined magnitude types. The single magnitude value is multiplied with the magnitude type specific weight. This is summed up for all magnitude types and the resulting sum is divided through the sum of all weights.

summaryMagnitude.enabled

Type: boolean

Enables summary magnitude calculation. Default is true.

summaryMagnitude.type

Type: string

Define the type/name of the summary magnitude. Default is M.

summaryMagnitude.minStationCount

Type: int

This is the minimum station magnitude required for any magnitude to contribute to the summary magnitude at all. If this is set to 4 then no magnitude with less than 4 station magnitudes is taken into consideration even if this results in no summary magnitude at all. For this reason, the default here is 1 but in a purely automatic system it should be higher, at least 4 is recommended. Default is 4.

summaryMagnitude.blacklist

Type: list:string

Define the magnitude types to be excluded from the summary magnitude calculation.

summaryMagnitude.whitelist

Type: list:string

Define the magnitude types to be included in the summary magnitude calculation.

Note

summaryMagnitude.coefficients.* Define the coefficients to calculate the weight of a magnitude. weight = a*magStationCount+b

summaryMagnitude.coefficients.a

Type: list:string

Define the coefficients a. Unnamed values define the default value. Default is 0, Mw(mB):0.4, Mw(Mwp):0.4.

summaryMagnitude.coefficients.b

Type: list:string

Define the coefficients b. Unnamed values define the default value. Default is 1, MLv:2, Mw(mB):-1, Mw(Mwp):-1.

magnitudes.average

Type: list:string

Defines the average method to use when computing the network magnitude. To define the average method per magnitude type append the type, eg: “magnitudes.average = default, MLv:median”

The default behaviour is to compute the mean if less than 4 contributed station magnitudes exist otherwise a trimmed mean of 25 percent is used.

Options are “default”, “mean”, “trimmedMean” and “medianTrimmedMean”. Default is default.

Command-line

Generic

-h, --help

show help message.

-V, --version

show version information

--config-file arg

Use alternative configuration file. When this option is used the loading of all stages is disabled. Only the given configuration file is parsed and used. To use another name for the configuration create a symbolic link of the application or copy it, eg scautopick -> scautopick2.

--plugins arg

Load given plugins.

-D, --daemon

Run as daemon. This means the application will fork itself and doesn’t need to be started with &.

--auto-shutdown arg

Enable/disable self-shutdown because a master module shutdown. This only works when messaging is enabled and the master module sends a shutdown message (enabled with –start-stop-msg for the master module).

--shutdown-master-module arg

Sets the name of the master-module used for auto-shutdown. This is the application name of the module actually started. If symlinks are used then it is the name of the symlinked application.

--shutdown-master-username arg

Sets the name of the master-username of the messaging used for auto-shutdown. If “shutdown-master-module” is given as well this parameter is ignored.

-x, --expiry time

Time span in hours after which objects expire.

Verbosity

--verbosity arg

Verbosity level [0..4]. 0:quiet, 1:error, 2:warning, 3:info, 4:debug

-v, --v

Increase verbosity level (may be repeated, eg. -vv)

-q, --quiet

Quiet mode: no logging output

--component arg

Limits the logging to a certain component. This option can be given more than once.

-s, --syslog

Use syslog logging back end. The output usually goes to /var/lib/messages.

-l, --lockfile arg

Path to lock file.

--console arg

Send log output to stdout.

--debug

Debug mode: –verbosity=4 –console=1

--log-file arg

Use alternative log file.

Messaging

-u, --user arg

Overrides configuration parameter connection.username.

-H, --host arg

Overrides configuration parameter connection.server.

-t, --timeout arg

Overrides configuration parameter connection.timeout.

-g, --primary-group arg

Overrides configuration parameter connection.primaryGroup.

-S, --subscribe-group arg

A group to subscribe to. This option can be given more than once.

--content-type arg

Overrides configuration parameter connection.contentType.

--start-stop-msg arg

Sets sending of a start- and a stop message.

Database

--db-driver-list

List all supported database drivers.

-d, --database arg

The database connection string, format: service://user:pwd@host/database. “service” is the name of the database driver which can be queried with “–db-driver-list”.

--config-module arg

The configmodule to use.

--inventory-db arg

Load the inventory from the given database or file, format: [service://]location

--db-disable

Do not use the database at all

Input

--ep file

Defines an event parameters XML file to be read and processed. This implies offline mode and only processes all origins contained in that file. It computes station magnitudes for all picks associated with an origin where amplitudes are available and the corresponding network magnitudes. Station and network magnitudes having the evaluation status set are ignored. Use the –force to include those magnitudes. It outputs an XML text adding the station- and network magnitudes to the input XML file.

--reprocess

Reprocess also station and network magnitudes with an evaluation status set but do not change weights and just add new contributions with weight 0.

Reprocess

--static

With that flag all existing station magnitudes are recomputed based on their associated amplitudes. If an amplitude cannot be accessed, no station magnitude is updated. Network magnitudes are recomputed based on their station magnitude contributions. No new objects will be created in this mode, it only updates values and weights. The method to accumulate the station magnitudes to form the network magnitude will be read from the existing object and replicated. If it cannot be interpreted then the configured default for this magnitude type will be used instead. Weights of station magnitudes will be changed according to the accumulation method of the network magnitude.

--keep-weights

Reuses the original weights in combination with –static.