INTERNATIONAL SEISMIC CAPACITY-BUILDINGTO ENHANCE EVENT LOCATION AND REGIONAL TECTONIC UNDERSTANDING

Rengin Gök1, Stephen Herzog2, Michael E. Pasyanos1, Rob J. Mellors1, David B. Harris1, Keith Nakanishi1, and Eileen S. Vergino1

Lawrence Livermore National Laboratory1 and the National Nuclear Security Administration2

OMANThe SCP’s work with Oman has been ongoing since 2004, when LLNL began cooperating with the Earthquake Monitoring Center of Sultan Qaboos University (SQU) on an analysis of the Masa� earthquakes. Collaboration continued through a determination of the crustal structure of Oman using Oman Seismological Network data. The SCP was also a sponsor of the March 2013 Gulf Seismic Forum conference in Muscat, which highlighted Oman’s regional leadership on seismological issues.

LLNL and SQU are now working on a joint project to deploy Oman’s �rst high-frequency seismic array under an existing Letter of Intent (LOI) for scienti�c cooperation. This project will involve the deployment of high-quality instrumentation and substantial observational seismology research to improve seismic hazard estimates in the Sultanate. The array will consist of a central broadband element surrounded by eight short-period stations. It will follow the classic short-period array design for regional event detection, phase identi�cation, and backazimuth estimation—similar to many International Monitoring System (IMS) arrays. The aperture will be about 3.5 kilometers, with minimum element spacing of 500 meters.

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ABSTRACTLawrence Livermore National Laboratory (LLNL) works through the National Nuclear Security Administration’s (NNSA) Seismic Cooperation Program (SCP) to train and pursue joint studies with seismologists in the Middle East and Southeast Asia. These activities o�er a model for capacity-building that strengthens regional scienti�c communities and monitoring of the Comprehensive Nuclear-Test-Ban Treaty (CTBT).

Collaborative projects include operating high-quality seismic instrumentation, sharing data using seismological tools (e.g., Seisan and SeisComp3), developing regional lithospheric models, and producing seismic hazard maps. While these projects are beginning in Southeast Asia, in the Middle East they show important �ndings. For example, studies reveal fundamental di�erences in the velocity structure of the uppermost mantle of the Arabian Shield and Arabian Platform. The earth’s crust is relatively thicker in the Mesopotamian Foredeep, characterized by thick sediments. Further, coda magnitude calibration of small- and moderate-size events is conducted on a local/regional scale.

The knowledge and analytical techniques gained by National Data Center (NDC) sta� and a�liated scientists are used in earthquake hazard mitigation, tsunami warning, and CTBT monitoring. Data from national seismic networks and derived measurements are integrated into lithospheric velocity, attenuation, and source models to increase resolution, improve event location accuracy and source parameter determination, and advance regional tectonic understanding.

SOUTHEAST ASIAFrom November 26-28, 2012, an NDC Development Workshop for the Association of Southeast Asian Nations (ASEAN) was held in Chiang Mai, Thailand. The workshop was jointly organized by the NNSA, LLNL, and the IDC’s Capacity Building and Training Section. It was hosted by Thailand’s O�ce of Atoms for Peace (OAP) and funded by the U.S. Department of State through U.S. Voluntary Contributions to the Preparatory Commission. Seven ASEAN States were represented: Cambodia, Indonesia, Malaysia, Myanmar, the Philippines, Thailand, and Viet Nam. Also in attendance were regional neighbors Australia, Japan, and Mongolia. This workshop will be followed by a more advanced training opportunity for ASEAN NDCs in 2014—addressing seismic hazard assessment, data sharing, and use of IDC data products.

LLNL seismologists built upon the success of the Chiang Mai workshop by conducting attenuation and coda magnitude studies to improve regional models. Preliminary results for the attenuation of various phases are show at right. The �gure shows the path coverage and inversion results. Data availability in the region from open global networks is modest, but this can be signi�cantly enhanced by sharing of data among regional networks. The path coverage clearly indicates the need for data exchange in the region.

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The �gure above shows the estimated paths of the Green’s functions between stations, as determined by ambient noise correlation using a preliminary data set. Each Green’s function represents the surface wave response of the path. These functions will be used to determine the crustal and upper mantle structure of Oman, either by directly inverting the Green’s function, or constructing a dispersion curve and inverting it.

There is variation in the Moho thickness between the northern and southern parts of Oman. We observed thicker crust around mountains in Oman, where the crust is dominated by ophiolites and hawasina sediments (Al-Hashmi et al., 2011).

Lawrence LivermoreNational Laboratory

LLNL and KISR analyzed KNSN recordings of nearly 200 local events to improve understanding of seismic events and crustal structure in Kuwait. We obtained an optimized one-dimensional velocity model for the region using reported KNSN arrival times and routine locations. The model is consistent with a recent model obtained from joint inversion of receiver functions and surface wave group velocities. Crustal structure is capped by the thick (approximately 7 kilometers) sedimentary rocks of the Arabian Platform, underlain by normal velocities for stable continental crust. The new model has a crustal thickness of 44 kilometers, supported by an independent study of receiver functions and surface wave group velocities by Pasyanos et al. (2006). Locations and depths of events after relocation with the new model are consistent with those reported by KISR, although a small number of events move more than a few kilometers.

KUWAITIn May 2010, LLNL worked through the SCP to begin a cooperative project with the Kuwait Institute for Scienti�c Research (KISR). The partners built on years of scienti�c collaboration and interaction in regional workshop settings by deploying two Guralp CMG-3EPS broadband, three-component seismic stations with Quanterra 330S digitizers in the existing vaults of Kuwait National Seismic Network (KNSN) sites MIB (Mutribah) and UMR (Umm ar Rimam). Operation of these stations took advantage of the strong noise reduction and thermal isolation properties of the KNSN’s deep permanent vaults. On May 8, 2010, the broadband instruments began operation. They have provided high-quality data that is a qualitative improvement over prior data recorded in Kuwait.

These stations have been integral to enhancing scienti�c knowledge of the crustal structure of Kuwait and improving understanding of the regional seismic structure. The Mesopotamian Foredeep—represented by thicker sediments—seems to be the signi�cant feature that a�ects the regional crustal thickness. This indicates that the crystalline crust in the region is �at from north to south (Gök et al., 2007).

IRAQTo improve scienti�c understanding of the Arabian Platform, LLNL partnered with the University of Arkansas at Little Rock (UALR) and the Iraq Seismological Network (ISN) to temporarily deploy two seismic stations in Iraq in 2006. The stations were located at Baghdad (BHD) and Mosul (MSL) and were equipped with Streckeisen STS-2 sensors.

SAUDI ARABIAKing Saud University (KSU) and LLNL have conducted an extensive amount of collaborative research since 1998. Five peer-reviewed papers focusing on the lithospheric structure of Saudi Arabia were published using local station data. The �gure at left shows results from P- and S-wave receiver function analysis (Hansen et al., 2008). Topography, gravity structure, and lithospheric structure are displayed along cross-sectional pro�le AA.

The KSU Department of Geology established a small-aperture (approximately 3.5 km) seismic array at a hard rock site on the Arabian Shield (Al-Amri et al., 2012). The array elements are housed in well-constructed vaults in hard rock outcrops in an area with very low background noise. The deployment includes a central broadband element (Streckeisen STS-2) and eight short-period, three-component sensors as outlying elements (�gure below).

National Nuclear Security Administration

We conducted a preliminary frequency-wavenumber (FK) analysis (left) using broadband stations in Oman and the United Arab Emirates to illustrate the potential performance of the proposed high-frequency array.

Seismic Cooperation ProgramThe SCP is a scienti�c outreach program of the U.S. Department of Energy’s National Nuclear Security Administration. The mission of the SCP is to provide capacity-building training in key seismological areas to government agencies and research institutes around the world. Training addresses civil-scienti�c concerns such as earthquake hazard mitigation, tsunami warning system operation, and building code development, as well as monitoring of the CTBT.

To assist partners address these issues, the SCP o�ers a variety of training courses involving such topics as: data sharing, event location, ambient noise correlation, seismic station and array deployment, NDC operations, lithospheric model development, and use of Regional Seismic Travel Time (RSTT) software. Courses are often conducted in partnership with the Capacity Building and Training Section of the Preparatory Commission’s International Data Centre (IDC). Trainees can employ skills learned from courses for national purposes, data sharing, and collaborative scienti�c studies with partners of their choice (examples of which are shown here).

a. Topography along the Red Sea Coast and Arabian Platform boundary

b. Comparison of observed gravity data from GRACE satellites (black dots) and calculated gravity (gray line) resulting from the structural model shown in c

c. Red dots mark nodes used in gravity modeling to constrain boundary depths and densities (p) of each layer; for stations along this pro�le, the Moho and Lithosphere-Asthenosphere Boundary (LAB) depths from strain reduction factor (SRF) analysis are shown by black squares with error bars (Hansen et al., 2008)

REFERENCESAl-Amri, A. M. S., D. B. Harris, M. Fnais, A. J. Rodgers, and M. Hemaida (2012). A Regional Seismic Array ofThree-Component Stations in Central Saudi Arabia, Seismol. Res. Lett. 83, 49–58, http://dx.doi.org/10.1785/gssrl.83.1.49.

Al-Hashmi, S., R. Gök, K. Al-Toubi, Y. Al-Shijbi, I. El-Hussain, and A. J. Rodgers (2011). Seismic velocitystructure at the southeastern margin of the Arabian Peninsula, Geophys. J. Int. 186, 782–792, http://dx.doi.org/10.1111/j.1365-246X.2011.05067.x.

Gök, R., H. Mahdi, H. Al-Shukri, and A. J. Rodgers (2007). Crustal structure of Iraq from receiver functions andsurface wave dispersion: Implications for understanding the deformation history of the Arabian–Eurasiancollision, Geophys J. Int. 172, 1179–1187, http://dx.doi.org/10.1111/j.1365-246X.2007.03670.x.

Hansen, S., J. Gaherty, S. Schwartz, A. Rodgers, and A. Al-Amri (2008). Seismic velocity structure and depth dependence of anisotropy in the Red Sea and Arabian shield from surface wave analysis, J. Geophys. Res. 113, B10307, http://dx.doi.org/10.1029/2007JB005335.

Laske, G., and G. Masters (1997). A Global Digital Map of Sediment Thickness, Eos Trans. Am. Geophys. Union.78, 483.

Pasyanos, M. E., H. Tkalčić, R. Gök, A. Al-Enezi, and A. J. Rodgers (2007). Seismic structure of Kuwait, Geophys.J. Int. 170, 299–312, http://dx.doi.org/10.1111/j.1365-246X.2007.03398.x.

Oman

UAE

S. Arabia

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344 and under the auspices of the U.S. Department of State under contract DOS_SIAA-11-AVC/NMA-1. Lawrence Livermore National Security, LLC. The views expressed here do not necessarily re�ect the views of the United States Government, the United States Department of Energy, the United States Department of State, or the Lawrence Livermore National Laboratory.

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