obspy.io.zmap - ZMAP read and write support for ObsPy

This module provides read and write support for the ZMAP format.

copyright

The ObsPy Development Team (devs@obspy.org)

license

GNU Lesser General Public License, Version 3 (https://www.gnu.org/copyleft/lesser.html)

Usage Example

The ZMAP reader and writer hooks into the standard ObsPy event handling mechanisms including format autodetection.

>>> from obspy.core.event import read_events
>>> cat = read_events('/path/to/zmap_events.txt')
>>> print(cat)
2 Event(s) in Catalog:
2012-04-04T14:21:42.300000Z | +41.818,  +79.689 | 4.4  None
2012-04-04T14:21:42.300000Z | +41.822,  +79.684 | 5.1  None
>>> cat.write('example.txt', format='ZMAP')

Reading ZMAP

Reading ZMAP is lenient, i.e. obspy.io.zmap will try to import a file even if it doesn’t strictly conform to 10 or 13 column ZMAP. Namely the following deviations from standard ZMAP format are acceptable:

  • Less or more than 10 or 13 columns. Extra columns are ignored. Missing values are set to None.

  • Integer years without a fractional part. If the fractional part is present, the date/time is computed from the year column. All other date/time fields are ignored. If the year column is an integer number, date and time are computed from all date/time related fields.

Note that ZMAP format autodetection in read_events() only works with strictly 10 or 13 column files. To read non-standard ZMAP files, the format='ZMAP' keyword argument must be provided.

When reading ZMAP, the following mappings are used for uncertainties

  • Column 11 (Horizontal error): stored in origin.origin_uncertainty.horizontal_uncertainty with preferred_description set accordingly.

  • Column 12 (Depth error): stored in origin.depth_errors.uncertainty

  • Column 13 (Magnitude error): stored in magnitude.mag_errors.uncertainty

Writing ZMAP

When writing to ZMAP, the preferred origin and magnitude are used to fill the origin and magnitude columns. Any missing values are exported as 'NaN'.

Extended ZMAP

Writing extended ZMAP, is supported by using the keyword argument with_uncertainties.

If OriginUncertainty specifies a horizontal uncertainty the value for column 11 is extracted from there. Uncertainty ellipse and confidence ellipsoid are not currently supported. If no horizontal uncertainty is given, Origin’s latitude_errors and longitude_errors are used instead. Depth and magnitude errors are always read from the respective _errors attribute in Origin.

The ZMAP Format

ZMAP is a simple 10 column CSV file (technically TSV) format for basic catalog data. It originates from ZMAP, a Matlab® based earthquake statistics package (see [Wiemer2001]). Since ZMAP files are purely numerical they are easily imported into Matlab® using the dlmread function.

Column #

Value

1

Longitude [deg]

2

Latitude [deg]

3

Decimal year (e.g., 2005.5 for July 2nd, 2005)

4

Month

5

Day

6

Magnitude

7

Depth [km]

8

Hour

9

Minute

10

Second

CSEP (http://www.cseptesting.org) defines an extension to the format to include uncertainties. The extended CSEP format has the following extra columns:

Column #

Value

11

Horizontal error

12

Depth error

13

Magnitude error

Modules

core

ZMAP read/write support.