Geography

A submarine landslide source for the devastating 1964 Chenega tsunami, southern Alaska

/ Matt Artz

epEarth and Planetary Science Letters, Volume 438, 15 March 2016, Pages 112–121

By Daniel S. Brothers, Peter J. Haeussler, Lee Liberty, David Finlayson, Eric Geist, Keith Labay, and Mike Byerly

“Highlights:

  • New geophysical evidence for a large landslide complex offshore Chenega Island.
  • Pervasive failure of glacimarine sediment along a perched sedimentary basin.
  • Earthquake-triggered submarine landslides are likely cause of tsunami in 1964.
  • Landslides display complex flow evolution from source area to deposition.

“During the 1964 Great Alaska earthquake (MwMw 9.2), several fjords, straits, and bays throughout southern Alaska experienced significant tsunami runup of localized, but unexplained origin. Dangerous Passage is a glacimarine fjord in western Prince William Sound, which experienced a tsunami that devastated the village of Chenega where 23 of 75 inhabitants were lost – the highest relative loss of any community during the earthquake. Previous studies suggested the source of the devastating tsunami was either from a local submarine landslide of unknown origin or from coseismic tectonic displacement. Here we present new observations from high-resolution multibeam bathymetry and seismic reflection surveys conducted in the waters adjacent to the village of Chenega. The seabed morphology and substrate architecture reveal a large submarine landslide complex in water depths of 120–360 m.

7.3-D perspective view of shaded relief bathymetry offshore Chenega village.

7.3-D perspective view of shaded relief bathymetry offshore Chenega village.

“Analysis of bathymetric change between 1957 and 2014 indicates the upper 20–50 m (∼0.7 km3) of glacimarine sediment was destabilized and evacuated from the steep face of a submerged moraine and an adjacent ∼21 km2 perched sedimentary basin. Once mobilized, landslide debris poured over the steep, 130 m-high face of a deeper moraine and then blanketed the terminal basin (∼465 m water depth) in 11±5 m11±5 m of sediment. These results, combined with inverse tsunami travel-time modeling, suggest that earthquake-triggered submarine landslides generated the tsunami that struck the village of Chenega roughly 4 min after shaking began. Unlike other tsunamigenic landslides observed in and around Prince William Sound in 1964, the failures in Dangerous Passage are not linked to an active submarine delta. The requisite environmental conditions needed to generate large submarine landslides in glacimarine fjords around the world may be more common than previously thought.”

U.S. lags behind the developed world with lack of national address database

/ Matt Artz / 1 Comment

NSGICOn October 27th, the White House released The Open Government Partnership – Third Open Government National Action Plan for the United States of America. The ‘pearl’ between the covers of this plan is item 4 on page 3. Its innocuous title – Launch a Process to Create a Consolidated Public Listing of Every Address in the United States – belies the importance of the following paragraph which states:

“Although address information for residential and commercial properties is collected across the United States by all levels of government and industry, it isn’t currently compiled in an open, easily accessible format. Additionally, much of the information collected at the Federal level is prohibited from public release due to various privacy laws. This non-private address information can be crucial to first responders and emergency service providers and can also be useful to innovators who might use it to build tools or launch services to improve communities. The Department of Transportation will begin coordinating across the public and private sector; connecting agencies, industry and innovators to gain consensus on an open standard for public address information; pursuing open data strategies for sharing certain address information — excluding names and other private information; and exploring uses of this information that drive innovation and inform the public.”

For over a decade, creating a national address point database has been at the top of NSGIC’s advocacy agenda. Chris Diller, President of the National States Geographic Information Council, stated “Address data are duplicated more often than any other type of data produced by government agencies, and the duplication happens at every level of government. We are hopeful that this Federal initiative will result in a coordinated effort to support state and local government addressing authorities in the compilation and maintenance of a National Address Database that provides open access to current and complete authoritative address data for every structure and landmark in the United States.”

In its February 2015 report on Geospatial Data, the U. S. Office of Management and Budget, brought its focus on the problems associated with creating a national address point database through the following recommendations.

TO CONGRESS: To increase coordination between various levels of government and reduce duplication of effort, resources, and costs associated with collecting and maintaining accurate address data, Congress should consider assessing the impact of the disclosure restrictions …[and]… consider revising those statutes to authorize the limited release of addresses, without any personally identifiable information… Such a change, if deemed appropriate, could potentially result in significant savings across federal, state, and local governments.

TO THE FEDERAL GEOGRAPHIC DATA COMMITTEE: Create an address data theme with associated subcommittees and working groups to assist in furthering a national address database.

The authors of this OMB report visited five states across the nation to learn how they were using address data and coordinating the development of consistent address point data with their respective local governments that are responsible for assigning addresses. Local governments also have the most demanding requirements for accurate data to support 9-1-1 services that ensure police, fire and ambulance services get to the right location as quickly as possible – on a daily basis and during major disasters.

Nearly every aspect of government services depends on address data, and an authoritative national database will consistently improve the delivery of services in the public and private sectors. Imagine using your car’s GPS system to accurately navigate to a precise address and not just arriving in the approximate area. Accurate address data coupled with high quality transportation data can significantly reduce repair and fuel expenses for fleet managers. Other important improvements to service delivery can be found in NSGIC’s flyer title A National Address Point Database Will Improve Government Services.

For a detailed review of the issues associated with building a national address point database, refer to the NSGIC advocacy document Address Points for the Nation, Contrasting the functions of Address Points and Parcel Maps. For more information supporting NSGIC’s promotion of free access to open data, refer to the Danish government study The Value of Danish Address Data citing a potential 31:1 direct financial benefit from the sharing of national address data.

About half of the states indicate they are ready to effectively coordinate the development of a consistent national address database with their local governments, NSGIC believes a well-coordinated Federal effort would encourage the remaining states to establish similar programs. If you would like more information about a particular state’s program, you can access a 2013 summary of individual state programs here, or a summary of all states here. You can also directly contact NSGIC’s State Representatives.

The National States Geographic Information Council (NSGIC) is an organization committed to effective and efficient government through the prudent adoption and use of geospatial information and technologies. NSGIC’s members are interested in the coordination of state spatial data infrastructures. They represent state Geographic Information Officers (GIO’s), state agency GIS leads, leaders of the statewide coordination councils, federal agencies, tribal government, local government, the private sector, academia and other professional organizations. The NSGIC membership is a diverse group that includes nationally and internationally recognized experts in geospatial technologies, geospatial data creation and management, and information technology policy.

[Source: NSGIC press release]

Protected areas in Borneo may fail to conserve tropical forest biodiversity under climate change

/ Matt Artz

405853Biological Conservation, Volume 184, April 2015, Pages 414–423

By Sarah A. Scriven, Jenny A. Hodgson, Colin J. McClean, and Jane K. Hill

“Protected areas (PAs) are key for conserving rainforest species, but many PAs are becoming increasingly isolated within agricultural landscapes, which may have detrimental consequences for the forest biota they contain. We examined the vulnerability of PA networks to climate change by examining connectivity of PAs along elevation gradients. We used the PA network on Borneo as a model system, and examined changes in the spatial distribution of climate conditions in future. A large proportion of PAs will not contain analogous climates in future (based on temperature projections for 2061–2080), potentially requiring organisms to move to cooler PAs at higher elevation, if they are to track climate changes.

Map of Borneo showing location of refuge (n = 30) and source PAs (n = 210). Source PAs are shaded according to the minimum dispersal ability required for individuals to successfully reach target PAs (assuming 100% forest cover in PAs, a population density of 125 individuals per 250 m forest grid cell and using RCP8.5 temperature projections).

Map of Borneo showing location of refuge (n = 30) and source PAs (n = 210). Source PAs are shaded according to the minimum dispersal ability required for individuals to successfully reach target PAs (assuming 100% forest cover in PAs, a population density of 125 individuals per 250 m forest grid cell and using RCP8.5 temperature projections).

“For the highest warming scenario (RCP8.5), few (11–12.5%; 27–30/240) PAs were sufficiently topographically diverse for analogous climate conditions (present-day equivalent or cooler) to remain in situ. For the remaining 87.5–89% (210–213/240) of PAs, which were often situated at low elevation, analogous climate will only be available in higher elevation PAs. However, over half (60–82%) of all PAs on Borneo are too isolated for poor dispersers (<1 km per generation) to reach cooler PAs, because there is a lack of connecting forest habitat. Even under the lowest warming scenario (RCP2.6), analogous climate conditions will disappear from 61% (146/240) of PAs, and a large proportion of these are too isolated for poor dispersers to reach cooler PAs. Our results suggest that low elevation PAs are particularly vulnerable to climate change, and management to improve linkage of PAs along elevation gradients should be a conservation priority.”

OGC Requests Comment on LandInfra Conceptual Model

/ Matt Artz

OGC_newThe Open Geospatial Consortium (OGC(R)) membership has issued a Request for Comments on the OGC LandInfra Conceptual Model.

This document, the first public draft of the OGC’s proposed UML conceptual model for land parcels and the built environment, communicates the proposed intent and content of a new candidate OGC standard to be called the OGC InfraGML Encoding Standard. The UML conceptual model establishes a single set of consistent concepts that could be implemented in GML (as InfraGML) or in other encoding mechanisms.

After reviewing the existing LandXML format, the OGC Land and Infrastructure Domain Working Group (LandInfraDWG) decided that a fresh start standard was warranted. The new standard would have a use case driven subset of LandXML functionality, but it would be consistent with the OGC standards baseline, implemented with the OGC Geography Markup Language (GML), and supported by a Unified Model Language (UML) conceptual model. Called InfraGML, this new standard would: be supported by a recognized Standards Developing Organization, OGC align with existing OGC (and TC211 and SQL/MM) standards, including the OGC Modular Specification benefit from functionality already supported by GML, including features, geometry, coordinate reference systems, linear referencing, and surface modeling (TIN) initially focus on alignments/roads, survey, and land parcels, the subject areas for which there are identified needs and committed resources for development using modular extensions, be able to expand into other areas (e.g., “wet” infrastructure pipe networks) as resources become available be use-case driven be based on a UML conceptual model developed prior to any encoding, such as GML have more up-to-date functionality be synchronized with the concurrent efforts by buildingSMART International in their development of Infrastructure-based Industry Foundation Classes (IFCs), and be more easily integrated with TransXML and OGC CityGML.

The work on buildingSMART International’s IFC Alignment Extension has been carried out by their P6 project team in strong collaboration with OGC Land&Infra Group. The use cases and the conceptual model are results of the joint work.

“This cooperation between buildingSMART International and the OGC will make it possible for software to directly map IFC alignment models to InfraGML and vice versa,” explained Richard Petrie, chief executive of buildingSMART International. “This represents an important milestone in reaching our shared goal of vendor-neutral standards that enable integration of geospatial information and information about the built environment.”

Scott Simmons, Executive Director of the OGC Standards Program, said, “The joint coordination of OGC and buildingSMART International in developing this conceptual model is an example of the benefits of proactive engagement between Standards Development Organizations. Our working together will result in a standard better suited to both communities and we’ll accomplish this much more quickly than if we worked separately now and harmonized later.”

The OGC LandInfra Conceptual Model and Request for Comment are available at https://portal.opengeospatial.org/files/61594.

[Source: OGC press release]

Geographically Weighted Regression to Measure Spatial Variations in Correlations between Water Pollution versus Land Use in a Coastal Watershed

/ Matt Artz / 1 Comment

OCMOcean & Coastal Management, Volume 103, January 2015, Pages 14–24

By Jinliang Huang, Yaling Huang,Robert Gilmore Pontius Jr., and Zhenyu Zhang

“Highlights

  • GWR reveals spatial variation in water pollution-land use linkages.
  • Water pollution is associated more with built-up than with cropland or forest.
  • More built-up is associated with more pollution for less urbanized sub-watersheds.
  • Forest has a stronger negative association with pollution in urban sub-watersheds.
  • Cropland has a weak association with water pollution among 21 sub-watersheds.

“Land use can influence river pollution and such relationships might or might not vary spatially. Conventional global statistics assume one relationship for the entire study extent, and are not designed to consider whether a relationship varies across space. We used geographically weighted regression to consider whether relationships between land use and water pollution vary spatially across a subtropical coastal watershed of Southeast China. Surface water samples of baseflow for seven pollutants were collected twelve times during 2010–2013 from headwater sub-watersheds. We computed 21 univariate regressions, which consisted of three regressions for each of the seven pollutants. Each of the three regressions considered one of three independent variables, i.e. the percent of the sub-watershed that was cropland, built-up, or forest.

Local R2 values and local parameter estimates for GWR cropland models among three types of sub-watershed.

Local R2 values and local parameter estimates for GWR cropland models among three types of sub-watershed.

“Cropland had a local R2 less than 0.2 for most pollutants, while it had a positive association with water pollution in the agricultural sub-watersheds and a negative association with water pollution in the non-agricultural sub-watersheds. Built-up had a positive association with all pollutants consistently across space, while the increase in pollution per increase in built-up density was largest in the sub-watersheds with low built-up density. The local R2 values were stronger with built-up than with cropland and forest. The local R2 values for built-up varied spatially, and the pattern of the spatial variation was not consistent among the seven pollutants. Forest had a negative association with most pollutants across space. Forest had a stronger negative association with water pollution in the urban sub-watersheds than in the agricultural sub-watersheds. This research provides an insight into land-water linkages, which we discuss with respect to other watersheds in the literature.”

OGC Seeks Public Comment on the Earth Observation Metadata Profile of the OGC Observations & Measurements Standard

/ Matt Artz / 1 Comment

OGC_newThe membership of the Open Geospatial Consortium (OGC®) seeks public comment on the candidate Earth Observation Metadata Profile of the OGC Observations and Measurements (O&M) Standard.

The Earth Observation (EO) Metadata profile of Observations and Measurements is intended to provide a standard schema for encoding Earth Observation product metadata to support the description and cataloguing of products acquired by sensors aboard EO satellites.

EO products are differentiated by parameters such as the date of acquisition and the image footprint as well as characteristics pertaining to the type of sensor, the type of platform, the applied processing chain, and more. This candidate standard identifies the metadata elements that enable the robust description of general EO products and defines specialisations for specific thematic classes of EO products, such as optical, radar, atmospheric, altimetry, limb-looking and systematic/synthesized EO products. In addition, this document describes the mechanism used to extend these thematic schemas for specific EO missions.

Version 1.0 of the EO Metadata profile of O&M is an OGC Implementation Standard that was adopted in 2012. Since then the standard has been implemented by the EO ground segments of a number of EO missions. During these implementations, a number of improvements and corrections have been identified. The proposed version 1.1 addresses these corrections and improvements.

The documents for the candidate OGC Earth Observation Metadata profile of Observations & Measurements Standard are available for review and comment at (http://www.opengeospatial.org/standards/requests/127).

The OGC is an international consortium of more than 495 companies, government agencies, research organizations, and universities participating in a consensus process to develop publicly available geospatial standards. OGC Standards support interoperable solutions that “geo-enable” the Web, wireless and location-based services, and mainstream IT. OGC Standards empower technology developers to make geospatial information and services accessible and useful with any application that needs to be geospatially enabled. Visit the OGC website at http://www.opengeospatial.org.

[Source: OGC press release]

What’s the Deal with 3DEP?

/ Matt Artz / 3 Comments

USGSReplacing Outdated and Inconsistent Elevation Data Will Save Lives and Improve Prosperity Across Our Nation

The USGS, along with other federal, state, local and private agencies is establishing a new 3D Elevation Program (3DEP) designed to respond to the growing needs for three-dimensional mapping data of the United States. This coordinated partnership can help meet the country’s needs for high-quality, 3D elevation data.

Current and accurate 3D elevation data are essential to help communities cope with natural hazards and disasters such as floods and landslides, support infrastructure, ensure agricultural success, strengthen environmental decision-making and bolster national security.

The primary goal of the 3DEP partnership is to systematically collect 3D elevation data across the Nation, using lidar, a remote sensing detection system that works on the principle of radar, but uses light from a laser.

A comparison of an air photo and a lidar image of an area along Secondary Road and Camp Creek, 12 miles north of John Day, OR. The lidar image allows identification of landslide activity that is otherwise masked by trees. (Photo courtesy of the Oregon Department of Geology and Mineral Industries).

A comparison of an air photo and a lidar image of an area along Secondary Road and Camp Creek, 12 miles north of John Day, OR. The lidar image allows identification of landslide activity that is otherwise masked by trees. (Photo courtesy of the Oregon Department of Geology and Mineral Industries).

“We are excited about working with partners to apply the game-changing technology of lidar to benefit many critical needs of national importance,” said Kevin Gallagher, USGS Associate Director of Core Science Systems. “For example, FEMA and NOAA are some of our strongest partners because they rely on this type of data to significantly improve floodplain mapping and to better communicate flood risks to communities and citizens.”

The 3DEP initiative is based on the results of the National Enhanced Elevation Assessment that documented more than 600 business and science uses across 34 Federal agencies, all 50 States, selected local government and Tribal offices, and private and nonprofit organizations.  The assessment also shows that 3DEP would provide more than $690 million annually in new benefits to government entities, the private sector, and citizens.

A recent White House fact sheet described how accessibility of accurate, high-quality 3D elevation data provides the foundation to the Administration’s overall plan to assist populations in the areas of flood risk management, water resource planning, mitigation of coastal erosion and storm surge impacts, and identification of landslide hazards.

The USGS will host a briefing on Capitol Hill on July 25 to further describe the importance, benefits and growing needs for 3D elevation data.

More information about 3DEP and state specific fact sheets is available online.

[Source: USGS press release]

Group on Earth Observations (GEO) Sessions and Special Exhibit at the 2014 Esri User Conference

/ Matt Artz / 1 Comment

Esri logoGroup on Earth Observations (GEO) Special Exhibit

Come learn about the Group on Earth Observations (GEO). Comprised of 90 member nations, the European Commission and 77 Participating Organizations who are working together to unleash the power of open Earth observation data.

Designed to improve the quality of life of people everywhere, GEO focuses putting sound science to work across nine essential areas: agriculture, biodiversity, climate, disasters, ecosystems, energy, health, water and weather.

GEO’s mandate is to drive the interoperability of many thousands of space-based, airborne, and in situ Earth observations around the globe.

Esri in cooperation with Institute of Atmospheric Pollution Research of the National Research Council of Italy (CNR-IIA) have team together to make it easy for the Esri user community to benefit from and to contribute to GEO. Esri has also supported the work of the Open Geospatial Consortium (OGC) in their contributions to the work of GEO.

Come see the GEO Data Access Broker of CNR-IIA Florentine Division and Esri Community Portal for GEO to see how you can participate; and to learn about the good work of GEO.


GEO Sessions

“Introduction to GEO”
Tuesday: 3:15 p.m. – 4:30 p.m., Room 29 A/B (SDCC)

  • Hear from the Director of GEO-Dr. Barb Ryan
  • Panel of GEO activist
  • See Demonstration of Esri Community Portal for GEO

“Esri Community Portal for GEO”
Thursday: 1:30 p.m. – 2:45 p.m., Room 3 (SDCC)

  • Tech Workshop
  • Learn about GEO Appathon

What Do Maps Reveal in the Fight to Eradicate Polio?

/ Matt Artz

Esri logoThe World Health Organization and the Bill & Melinda Gates Foundation will share their stories at the 2014 Esri User Conference.

Dr. Bruce Aylward from the World Health Organization (WHO) and Dr. Vincent Seaman from the Bill & Melinda Gates Foundation will share their stories with an audience of more than 16,000 attendees at the Opening Session of the 2014 Esri User Conference (Esri UC) on Monday, July 14. As experts in the Global Polio Eradication Initiative, they will describe the challenges and opportunities involved in bringing fundamental healthcare to impoverished regions. They’ll also talk about the importance maps have in pinpointing where help is needed most around the world.

“Polio, a terrible disease, is almost completely eradicated, but ‘almost’ isn’t good enough with a disease slated for complete eradication,” said Aylward.

Most of the world hardly remembers polio, which has been reduced by over 99 percent in the past generation by vaccination. However, the disease survives in parts of just a few countries, and has repeatedly spread back from these places to polio-free areas worldwide. The urgency of preventing such spread and protecting the polio-free world led the WHO Director-General to declare a public health emergency of international concern on May 5, 2014.

“The polio eradication program is an international effort to reach the most vulnerable people in the world, irrespective of geography, poverty, culture, and conflict,” said Aylward.

The Esri UC, to be held July 14–18, will bring together thousands of people from more than 90 countries, all unified by their use of Esri’s geographic information system (GIS) technology. Of particular interest to Esri UC attendees will be the use of GIS in the Global Polio Eradication Initiative. Aylward will explain how the people working at WHO identify where there are new outbreaks in the world, how the disease spreads, and where it has been eradicated. Seaman will share how the polio program uses GIS-based maps and analyses in high-risk areas to plan vaccination campaigns targeting every child under the age of five and to provide better tools to assess the effectiveness of these efforts.

BrAUOaCCYAIXTyY.jpg large

“At the Esri UC Plenary Session, we like to feature innovative people doing important work around the world,” said Esri president Jack Dangermond. “Dr. Aylward and Dr. Seaman certainly qualify. We are honored to welcome them and excited that GIS can help fulfill the mission of the Global Polio Eradication Initiative as the teams of humanitarians use maps to understand and solve problems.”

About the Esri UC Plenary Keynote Speakers

Dr. Bruce Aylward is a Canadian physician and epidemiologist and the assistant director-general for the WHO’s Polio and Emergencies cluster. He began his career with the WHO in 1992 as a medical officer with the Expanded Program on Immunization. Aylward worked in national immunization programs in developing countries, primarily those focusing on polio, and took assignments in Afghanistan, Cambodia, Egypt, Iraq, and Myanmar. After six years in the field, Aylward returned to the WHO in Geneva, Switzerland, in 1997 to lead the Global Polio Eradication Initiative.

Dr. Vincent Seaman is an American health scientist, educator, and a senior program officer for the Polio Country Support Team at the Bill & Melinda Gates Foundation. Before that, Seaman was a Centers for Disease Control (CDC) and Prevention secondee to the WHO in Nigeria for nearly 3 years, where he provided technical support to the Expanded Program on Immunization and worked on the polio eradication effort. He began his career at CDC as a Presidential Management Fellow in 2006, and continued on as an epidemiologist in the areas of environmental public health and vaccine-preventable diseases. In addition to leading health investigations at various Superfund sites in the U.S., Dr. Seaman supported the HIV/AIDS program in Mozambique in 2009, and was a STOP Polio volunteer in Liberia in 2010.

For more information about the Esri UC, visit esri.com/uc.

[Source: Esri press release]

Scientists Use LiDAR, 3-D Modeling Software to Intricately Map Active Chinese Fault Zone

/ Matt Artz / 1 Comment

Chinese and American scientists collaborating in the study of an active seismic fault that produced one of China’s most deadly earthquakes say their deployment of an airborne LiDAR system, which uses pulses of laser light to calculate distances and chart terrain features, has helped them produce the most precise topographical measurements ever of the fault zone.

“Light detection and ranging (LiDAR) presents a new approach to build detailed topographic maps effectively,” they report. They add that these high-precision three-dimensional models can be used to illustrate not only land surface changes following past quakes, but also features of past ruptures that could point to the possibility of future temblors.

Experts at the State Key Laboratory of Earthquake Dynamics and at the National Earthquake Infrastructure Service in Beijing, working with a colleague at the United States Geological Survey (USGS) in Pasadena, California, mounted a Leica ALS-60 LiDAR system aboard a Chinese Yun Five aircraft and then began scanning the Haiyuan fault zone in a series of flights over the course of a week. The fault zone is similar to the San Andreas fault in California, which has similarly been scanned and studied as a comparison.

“During the past century,” they explain in a new study, “the Haiyuan fault zone produced two great earthquakes: the M 8.5 Haiyuan earthquake in 1920, along the eastern Haiyuan fault, and the M 8𔃆.3 Gulang earthquake in 1927.”

“The Haiyuan earthquake of 16 December 1920 is one of the largest intra- continental earthquakes ever documented in history,” they add, “and ruptured about a 237-kilometer-long ground surface, with a maximum left-lateral slip of 10.2 m, and claimed over 220,000 lives.”

In the new study, “Quantitative study of tectonic geomorphology along the Haiyuan fault based on airborne LiDAR,” lead scientist Jing Liu and her colleagues at the Earthquake Dynamics Lab, part of the China Earthquake Administration in Beijing, state their experiments with the LiDAR scanning system and related building of a high-resolution topographical model provide “an example of how LiDAR data may be used to improve the study of active faults and the risk assessment of related hazards.”

Sections of the 3D digital model generated with the LiDAR data are “intensively analyzed to demonstrate tectonic geomorphic feature identification and displacement measurement,” they state. The LiDAR data are also used, for example, to calculate horizontal and vertical coseismic offsets in one section of the fault zone.

LiDAR data can be used to verify measurements made during fieldwork on offsets of tectonic landform features, state co-authors Tao Chen, Pei Zhen Zhang, Jing Liu, Chuan You Li, and Zhi Kun Ren, along with Ken Hudnut at the USGS, who visited the China Earthquake Administration to participate in this study. “The offset landforms are visualized on an office computer workstation easily, and specialized software may be used to obtain fault displacement measurements quantitatively,” they explain.

With LiDAR-generated digital models of the topography across fault zones, the “link between fault activity and large earthquakes is better recognized, as well as the potential risk for future earthquake hazards,” says the team of scientists.

More precise measurements of the active fault zone made possible by the LiDAR system, and their depiction in sophisticated three-dimensional maps, are helping scientists not only in basic research, but also in terms of calculating the probability of a seismic shock recurring, say the co-authors of the new study, which was published online in the journal Chinese Science Bulletin by Science China Press and Springer-Verlag.

Airborne laser swath mapping helps scientists to virtually remove the vegetation covering from topographical models; this “bare earth” representation provides for more accurate identification of tectonic features and changes following a quake.

A LiDAR airborne scanning system of the Earth’s terrain was deployed over the section of the southwestern Chinese province of Sichuan that was the epicenter of a Mw7.9 earthquake that struck in May of 2008; LiDAR data were used to map the scale of landslides and ultimately to develop rescue schemes.

In the new study, the Chinese and American scientists say that digital models created using LiDAR data from the Haiyuan fault zone “have a much higher resolution than existing topographic data and most aerial photographs, allowing us to map the locations of fault traces more accurately than ever.”

The high level of precision of the digital models constructed with information from the LiDAR laser scans of the topography in this fault zone will encourage future “site-specific fault activity studies,” state the scientists.

“In the future,” they predict, “we can expect that more and more concepts or models of fault activity would benefit from this unprecedented survey technique.”

Along the Haiyuan fault zone in the western Chinese province of Gansu, LiDAR scans and related digital models have already been used to identify 600 channels and other linear geomorphic features slated for more comprehensive analysis.

“The next step is to measure the displacements along the whole Haiyuan fault and analyze the principle of the slip distribution,” states the team of scientists, “which would help people better understand the fundamental link between fault activity and large earthquakes and assess potential risk for future earthquake hazards.”

In places where slip during past earthquakes was less pronounced, it is possible that future earthquakes could have greater slip in order to accommodate and equalize motions along the fault system. Alternatively, slip may be large repeatedly in some places and small elsewhere. Such variations in slip may help to assess future hazards, so observations of this kind are very important to answer unresolved questions that are central to research on hazards of earthquake fault zones around the world.

[Source: Science China Press]