A new method in volcano-morphology to investigate the tectonic constraints on the volcanism, case study of Harrat Al Sham volcanic field, Arabia plate: the interest of GIS and Relational Database

摘要

The volcanic activity of Arabian plate offers an attractive example of intraplate volcanism constrained by a complex tectonic setting. Harrat Ash Shaam volcanic field (HASV) is a basaltic province, extends widely at Arabian plate (over 50 000 km2), covers south of Syria, northeast of Jordan, north of Saudi Arabia, and contains hundreds of well- preserved monogenic volcanic cones.rnOur method aims to identify those cones volcanic, calculate its morphological parameters (heights, slopes, surfaces, volumes...etc.), and study their correlation. The farther intention of this study is to investigate the consequence of the tectonic events on the volcanic activity by testing the relations between the volcano-morphological parameters and the structure of the lithosphere (basement and moho surfaces).rnThe realization of these objectives is problematic and even impossible by using the traditional exploration methods. Thanks to the computing technology which offers a vast opportunity to develop a new digital method in order to achieve such complex geospatial study.rnWe suggest the integration and the exploitation of following primary data (so called to be distinguished from the extracted data): 1) the remote sensing (RS) technology provides several satellite scenes (Iandsat7, ETM+), 2) digital elevation models (SRTM data), 3) Digital earth application (by Cornell University), latter source offers internet based open access system of interpretation of geophysical data as estimation of crustalrnthickness and depth to Moho, 4) several geological maps of the study area,5) K-Ar ages.rnThe main challenges of this work are: a) building up geospatial database, geo-referencing and managing the primary data of different sources at same platform, b) treating the primary data to extract advanced levels of data, c) sustain the principle of "data independence" in order to protect the root of data from confusion after the process of extraction, which is imperative during the results interpretation (e.g. it must be specified if the volume parameter has been mathematically extracted based on the surface or independently).rnThis paper spotlights the role of GIS in our geospatial investigation, and explains techniques employed in our method: 1) processing the satellite images with the purpose of distinguish the cones volcanic at HASV (more than 800 cones have been detected), 2) using spatial analysis tools in order to obtain automatically the periphery and the virtual bases of each cones volcanic from the digital elevation model, and 3) using GIS platform as tools to manage multi sources- data efficiently.rnin addition to, we highlight the integration between GIS and Relational Database, that we redesigned the geospatial database and restructured the data tables according to the new defined objects (i.g. the volcanic cones). In addition we have been used SQL widely in order to extract the advanced data levels (e.g. the morphological parameters), and to develop an approach in order to protect data roots.rnOn other hand, the facility of exporting and importing the geospatial data tables between GIS and Microsoft application permitted us to reproduce easily and quickly the results of our research in form of maps (by using mapping tools based on geo-statistical methods of GIS). Consequently we propose an example of data streaming characterized by a gee-database system growing up in two directions (rows and columns). Our suggestion based on an observation; that in this case study, the geospatial database grows throughout a "looping process" between input and output data (i.g. the output data turn out to be a new batch of input data inserts again to the system). The probability of this looping process seems to be high and relates to the number of the scientific questions under investigation using the geospatial database system.rnOur prospective of the future challenge is to enhance the update links between the primary and the extracted data levels with the aim of bridging the gap created by high rate data streaming, as well as we proposed to develop the approach of "data independence".rnThis case study shows that the role of GIS and Relational Database in geospatial investigation is not only indispensable as tools to manage and manipulate multi sources data, but is also significant to answer composite scientific questions.rnThat our results demonstrate different spatial density zones contain clusters of hundreds of cones volcanic, in addition to considerable spatial differentiations of the morphological parameters. Consequently, we linked those variations to the lithosphere structures.rnOn other hand our results obtained by applying digital based-method to HASV are in agreement with our dating results (K-Ar ages) of the volcanic activity, and the petrologic evidences at the northern parts of HASV. That enhanced our understanding of the volcano-tectonic evolution of the study area and played key role to suggest a spatial-temporal model characterizes the tectonic alteration between the compression and the extension during the last 26 Ma.rnWe expect the mentioned harmony between results (i.e. direct method and digital based- methods) could reflect an important advantage in comparing the volcanism of HASV and other terrestrial planets.rnMoreover our results suggest a huge tectonic constrain on'the volumes of the volcanic activity; that is fundamental to manage the volcanic risks at active analog zones. Therefore, we concluded that the digital based- method is helpful for monitoring and predication the natural hazards at regional scales.rnIn the light of the previous facts building up the digital earth and developing its management tools are the future duties.