demos/event_based_hazard/source_model.xml:
demos/event_based_hazard/source_model.xml:

Added a multi-surface characteristic source.


Former-commit-id: 5c39d46f5c2d402c8db60ec2d9e8fac24156b5f3
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine