We held a workshop on high resolution topography applied to earthquake studies as part of the Virtual Institute for the Study of Earthquake Systems (VISES) activity lead by the Southern California Earthquake Center at the Earthquake Research Institute in Tokyo, Sept. 18-20, 2013.
The planners of the workshop were me and Koji Okumura from Hiroshima University along with Chris Crosby (UNAVCO), Mike Oskin (UC Davis), Edwin Nissen (Colorado School of Mines), and Shinji Toda (Tohoku University).
I just completed the workshop report pdf link.
We came up with a few recommendations that are worth pulling out of the report:
- There has been an interesting evolution of methodology for study of active faulting and topography. LiDAR has revolutionized many tasks and our ability to measure surface features at the fine scale at which the surface processes and earthquake deformation operate.
- The challenge of identifying active faults in topography (especially in areas of low fault slip rates and high surface process rates and heavy vegetation) remains. A standardized approach of morphology delineation followed by detailed surficial geologic mapping should yield defendable fault traces and indication of potential detailed study sites.
- Once faults are identified, reconstructing offset and deformed features is necessary. A combination of field and virtual approaches was advocated. Uncertainty assessment in the reconstructions is an active area.
- A substantial emphasis has been on surface rupture characterization in high resolution topography acquired shortly after an earthquake. This effort includes airborne and terrestrial laser scanning data integration. Examination of tilted trees in the vegetation (Yoshimi) was a clever use of the three dimensional data to characterize surface deformation along the earthquake rupture.
- High relief areas such as parts of Japan and southern California are susceptible to landslides and their interaction with active faults is notable. In addition, their methods of study using high resolution topography are similar.
- Topographic differencing along Japanese and the El Mayor Cucupah earthquake ruptures is yielding exciting results that seem to document variable continuity of slip along fault surfaces in the upper several hundred meters below the Earth surface. These results are complementary with the wide aperture INSAR results typically coming from earthquake studies. The various approaches for differencing (Iterative closest point, image correlation, pixel matching, particle image velocimetry, etc.) should be systematically compared.
- Ongoing training and knowledge exchange of the sort done here is valuable.
- It is important to facilitate community access to high-resolution, Earth science-oriented, topography data, and related tools and resources. This is the mission of OpenTopography. We discussed these ideas and that open access was desirable, but topographic data in particular in Japan tends to be difficult to obtain for scientists without purchasing it (despite the data having been paid for initially by public funds).
Here are a few pictures from the trip (note that all were taken by Koji Okumura):