Time grammar¶

The time windows for measuring noise and signal for amplitudes used to compute magnitudes can be configured by the respective begin and end values. These window parameters are configured as global binding parameters specifically for a particular amplitude type, let’s say ML:

amplitudes.ML.noiseBegin
amplitudes.ML.noiseEnd
amplitudes.ML.signalBegin
amplitudes.ML.signalEnd

The configured values are added to the relative trigger time and the origin time for forming absolute times. The relative trigger time corresponds to the arrival of P waves for most applications. The configured begin and end values are therefore given as time differences relative to the absolute trigger time.

Example:

$absoluteSignalEnd =\ &originTime + relativeTriggerTime + amplitudes.ML.signalEnd \\ =\ &triggerTime + amplitudes.ML.signalEnd$

Important

Where travel times of a particular phase are estimated from distance measures such as D or h, the relative origin time, OT, must be added to get the time difference. In contrast, tt() returns the time difference to OT and tt() does not need to be corrected.

In SeisComP the configuration of the begin and end values is supported by a combination of functions, operators, variables and constant values. The combination of them allows setting up a flexible time grammar for time windows. You may use parentheses () to apply operations within the parentheses before operations outside of parentheses.

If the result of the final evaluation is unset, e.g., because required information are not available, then the processing receives an error and the amplitude will not be computed.

Examples¶

The details of the grammar elements used in the following examples are described below.

Return the signal end time to measure mB amplitudes:
```
min(D * 11.5, 60)
```
where function min() returns the minium from two parameters to, epicentral distance, D, is a variable and ‘*’ and ‘+’ are operators.

In this example, the minimum time from either epicentral distance in degree times 11.5 s/deg or 60 s is returned if epicentral distance is available. If epicentral distance is not available, 60 s is returned hence being the default.
Return the signal end time to measure amplitudes ending before the arrival of surface waves or 150 s:
```
min(OT + D * 35, 150)
```
where the epicentral distance, D, is multiplied by 35 s/deg. The relative origin time, OT, is either added in order to obtain the time relative to trigger time. The minimum of this value and 150 s is returned by min(). This means that 150 s it the default in case epicentral distance is not available.
Return the time difference as the minimum of predicted arrivals of S-waves adding 10 s or 150 s:
```
min(tt(S) + 10, 150)
```
where the function tt() returns the relative travel time of the argument, here the S phase, and ‘+’ is an operator.

In this example the minimum time from either the relative arrival time of S phase plus 10 s or 150 s is returned.

Similar to the statements above, the time windows for measuring amplitudes can be configured, e.g., for overriding default time for MLv amplitudes:

amplitudes.MLv.noiseBegin=-10
amplitudes.MLv.noiseEnd=-1
amplitudes.MLv.signalBegin=-1
amplitudes.MLv.signalEnd=tt(S)+10

Functions, Operators, Variables¶

Variables, operators and functions are available. Variables define standard values and function provide values based on a parameter given within parentheses like tt(). Find below their individual descriptions.

Functions¶

max(arg1, arg2)¶

Calculates the maximum of two values. If one value is unset then the other value is returned. If both values are unset then the result is unset, too.

Parameters:

arg1 – First value to consider
arg2 – Second value to consider

min(arg1, arg2)¶

Calculates the minimum of two values. If one value is unset then the other value is returned. If both values are unset then the result is unset, too.

Parameters:

arg1 – First value to consider
arg2 – Second value to consider

tt(phase)¶

Calculates the travel-time of the given phase relative to the trigger time. The result is unset if the travel time cannot be computed.

Parameters:: phase – Phase name available with the define travel-time interface and profile.

arr(phase, acceptAll)¶

Extracts the travel times of actually used arrivals relative to the trigger time. The arrivals with the given phase code must exist.

Parameters:

phase – Phase code of the arrival. The arrival must exist and the sensor location of the associated pick must match the sensor location of the target object.
acceptAll – Whether to accept all arrivals or only manually revised arrivals. The default is ‘true’ if not given. Allowed is either ‘true’ or ‘false’. If ‘true’ is given, then either the evaluation mode of the origin or the evaluation mode of the pick must be ‘manual’.

Operators¶

If either of the operands is unset then the result will be also unset.

+ : addition
- : subtraction
* : multiplication
/ : division
^ : power / exponentiation
|| : logical OR which returns the first set value if any
|. | : absolute value
% : modulo

Variables¶

Variables can take the value unset when required information is not available. The behaviour of operators and functions with variables of value unset depends on the operator and function itself.

OT¶

Relative origin time as difference from origin to trigger (originTime - triggerTime). For most amplitude types, the trigger is the measured or the predicted arrival time of the P phase.

Unit: s

D¶

Unit: km

Epicentral distance

Unit: deg

d, R¶

Epicentral distance

Unit: km

H¶

Hypocentral distance

Unit: deg

h¶