WP 4.3 Surface fractures in the source region of the June 2000 events

Start date or starting event:

M0

Lead contractor:

SIUI

Participants:

SIUI, NVI

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Objectives:

1. Cast light on the relationship between surface faulting and faulting at depth during the June 2000 events.

2. Map the surface fractures in the area surrounding the two main faults active in the earthquakes.

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Inputs:

1. Data from previous fracture-mapping projects in the area.

2. Aerial photographs.

3. Historical data.

Methodology / work description:

The epicentral zone of the SISZ shows widespread evidence of recent faulting. Historical documents mention surface faulting during some of the earthquakes, and in the case of the events of 1630, 1784, 1896 and 1912 the fractures have been located and mapped in detail. Most of the fractures of 2000 have been mapped as well. The fractures are grouped into regular arrays, each with N to NE orientation. The arrays are 0.3-3 km long and consist of tension fractures in en echelon arrangement. The tension fractures may be up to a few tens of meters long and have a more easterly orientation than the arrays themselves.  Push-up structures are often found between the tips of adjacent fractures.  The arrays are lined up in a N-S direction, and are interpreted to reflect underlying right-lateral strike-slip faults. The faults can be traced up to a distance of more than 15 km. Splay faults are sometimes found, branching off from the main faults. Structures resembling those of the 1912, 1896 and 1630 ruptures are found throughout the seismic zone.   They can be grouped into systems interpreted to represent faults, more than 25 of which have been identified so far. The faults are transverse to the seismic zone and are arranged side-by-side with spacing of about 1 km between them.

We propose to use differential GPS instruments to map in detail the remaining fractures of 2000 as well as all older fractures in the surrounding areas. The maps will be compared with the results of other workpackages, in particular WP, especially 4.1 and 4.4.

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Deliverables including cost of deliverable as percentage of total cost of the proposed project:

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Milestones: Delivery of the above items at the date indicated.