QuakeML: fix a bug in reading QuakeML (empty stub MomentTensor added)

obspy/io/quakeml/core.py

@@ -696,11 +696,11 @@ def _nodal_plane(self, parent, name):
         :param name: tag name of sub nodal plane
         :rtype: :class:`~obspy.core.event.NodalPlane`
         """
-        obj = NodalPlane()
         try:
             sub_el = self._xpath(name, parent)[0]
         except IndexError:
-            return obj
+            return None
+        obj = NodalPlane()
         # required parameter
         obj.strike, obj.strike_errors = self._float_value(sub_el, 'strike')
         obj.dip, obj.dip_errors = self._float_value(sub_el, 'dip')
@@ -715,11 +715,11 @@ def _nodal_planes(self, parent):
         :type parent: etree.Element
         :rtype: :class:`~obspy.core.event.NodalPlanes`
         """
-        obj = NodalPlanes()
         try:
             sub_el = self._xpath('nodalPlanes', parent)[0]
         except IndexError:
-            return obj
+            return None
+        obj = NodalPlanes()
         # optional parameter
         obj.nodal_plane_1 = self._nodal_plane(sub_el, 'nodalPlane1')
         obj.nodal_plane_2 = self._nodal_plane(sub_el, 'nodalPlane2')
@@ -738,11 +738,11 @@ def _source_time_function(self, parent):
         :type parent: etree.Element
         :rtype: :class:`~obspy.core.event.SourceTimeFunction`
         """
-        obj = SourceTimeFunction()
         try:
             sub_el = self._xpath('sourceTimeFunction', parent)[0]
         except IndexError:
-            return obj
+            return None
+        obj = SourceTimeFunction()
         # required parameters
         obj.type = self._xpath2obj('type', sub_el)
         obj.duration = self._xpath2obj('duration', sub_el, float)
@@ -759,11 +759,11 @@ def _tensor(self, parent):
         :type parent: etree.Element
         :rtype: :class:`~obspy.core.event.Tensor`
         """
-        obj = Tensor()
         try:
             sub_el = self._xpath('tensor', parent)[0]
         except IndexError:
-            return obj
+            return None
+        obj = Tensor()
         # required parameters
         obj.m_rr, obj.m_rr_errors = self._float_value(sub_el, 'Mrr')
         obj.m_tt, obj.m_tt_errors = self._float_value(sub_el, 'Mtt')
@@ -807,11 +807,11 @@ def _moment_tensor(self, parent):
         :type parent: etree.Element
         :rtype: :class:`~obspy.core.event.MomentTensor`
         """
-        obj = MomentTensor(force_resource_id=False)
         try:
             mt_el = self._xpath('momentTensor', parent)[0]
         except IndexError:
-            return obj
+            return None
+        obj = MomentTensor(force_resource_id=False)
         # required parameters
         obj.derived_origin_id = self._xpath2obj('derivedOriginID', mt_el)
         # optional parameter
@@ -1525,9 +1525,11 @@ def _nodal_planes(self, obj, element):
         """
         Converts a NodalPlanes into etree.Element object.
 
-        :type pick: :class:`~obspy.core.event.NodalPlanes`
+        :type obj: :class:`~obspy.core.event.NodalPlanes`
         :rtype: etree.Element
         """
+        if obj is None:
+            return
         subelement = etree.Element('nodalPlanes')
         # optional
         if obj.nodal_plane_1:
@@ -1561,7 +1563,7 @@ def _principal_axes(self, obj, element):
         """
         Converts a PrincipalAxes into etree.Element object.
 
-        :type pick: :class:`~obspy.core.event.PrincipalAxes`
+        :type obj: :class:`~obspy.core.event.PrincipalAxes`
         :rtype: etree.Element
         """
         if obj is None:
@@ -1605,7 +1607,7 @@ def _moment_tensor(self, moment_tensor, element):
         """
         Converts a MomentTensor into etree.Element object.
 
-        :type pick: :class:`~obspy.core.event.MomentTensor`
+        :type moment_tensor: :class:`~obspy.core.event.MomentTensor`
         :rtype: etree.Element
         """
         if moment_tensor is None:
@@ -1671,9 +1673,11 @@ def _focal_mechanism(self, focal_mechanism):
         """
         Converts a FocalMechanism into etree.Element object.
 
-        :type pick: :class:`~obspy.core.event.FocalMechanism`
+        :type focal_mechanism: :class:`~obspy.core.event.FocalMechanism`
         :rtype: etree.Element
         """
+        if focal_mechanism is None:
+            return
         element = etree.Element(
             'focalMechanism',
             attrib={'publicID': self._id(focal_mechanism.resource_id)})
@@ -1688,10 +1692,8 @@ def _focal_mechanism(self, focal_mechanism):
         self._str(focal_mechanism.misfit, element, 'misfit')
         self._str(focal_mechanism.station_distribution_ratio, element,
                   'stationDistributionRatio')
-        if focal_mechanism.nodal_planes:
-            self._nodal_planes(focal_mechanism.nodal_planes, element)
-        if focal_mechanism.principal_axes:
-            self._principal_axes(focal_mechanism.principal_axes, element)
+        self._nodal_planes(focal_mechanism.nodal_planes, element)
+        self._principal_axes(focal_mechanism.principal_axes, element)
         self._str(focal_mechanism.method_id, element, 'methodID')
         self._moment_tensor(focal_mechanism.moment_tensor, element)
         self._str(focal_mechanism.evaluation_mode, element, 'evaluationMode')

obspy/io/quakeml/tests/test_quakeml.py

@@ -1009,6 +1009,59 @@ def test_read_same_file_twice_to_same_variable(self):
         # No warning should have been raised.
         self.assertEqual(len(w), 0)
 
+    def test_focal_mechanism_write_read(self):
+        """
+        Test for a bug in reading a FocalMechanism without MomentTensor from
+        QuakeML file. Makes sure that FocalMechanism.moment_tensor stays None
+        if no MomentTensor is in the file.
+        """
+        memfile = io.BytesIO()
+        # create virtually empty FocalMechanism
+        fm = FocalMechanism()
+        event = Event(focal_mechanisms=[fm])
+        cat = Catalog(events=[event])
+        cat.write(memfile, format="QUAKEML", validate=True)
+        # now read again, and make sure there's no stub MomentTensor, but
+        # rather `None`
+        memfile.seek(0)
+        cat = read_events(memfile, format="QUAKEML")
+        self.assertEqual(cat[0].focal_mechanisms[0].moment_tensor, None)
+
+    def test_avoid_empty_stub_elements(self):
+        """
+        Test for a bug in reading QuakeML. Makes sure that some subelements do
+        not get assigned stub elements, but rather stay None.
+        """
+        # Test 1: Test subelements of moment_tensor
+        memfile = io.BytesIO()
+        # create virtually empty FocalMechanism
+        mt = MomentTensor(derived_origin_id='smi:local/abc')
+        fm = FocalMechanism(moment_tensor=mt)
+        event = Event(focal_mechanisms=[fm])
+        cat = Catalog(events=[event])
+        cat.write(memfile, format="QUAKEML", validate=True)
+        # now read again, and make sure there's no stub subelements on
+        # MomentTensor, but rather `None`
+        memfile.seek(0)
+        cat = read_events(memfile, format="QUAKEML")
+        self.assertEqual(cat[0].focal_mechanisms[0].moment_tensor.tensor, None)
+        self.assertEqual(
+            cat[0].focal_mechanisms[0].moment_tensor.source_time_function,
+            None)
+        # Test 2: Test subelements of focal_mechanism
+        memfile = io.BytesIO()
+        # create virtually empty FocalMechanism
+        fm = FocalMechanism()
+        event = Event(focal_mechanisms=[fm])
+        cat = Catalog(events=[event])
+        cat.write(memfile, format="QUAKEML", validate=True)
+        # now read again, and make sure there's no stub MomentTensor, but
+        # rather `None`
+        memfile.seek(0)
+        cat = read_events(memfile, format="QUAKEML")
+        self.assertEqual(cat[0].focal_mechanisms[0].nodal_planes, None)
+        self.assertEqual(cat[0].focal_mechanisms[0].principal_axes, None)
+
 
 def suite():
     return unittest.makeSuite(QuakeMLTestCase, 'test')