SEISMIC HAZARD ASSESSMENT OF VIỆT NAM TERRITORY
ON THE BASIS OF DETERMINISTIC APPROACH

1CAO ĐÌNH TRIỀU, 2GIULIANO F. PANZA, 2A. PERESAN, 2F. VACCARI,
2F. ROMANELLI, 1NGUYỄN HỮU TUYÊN, 1PHẠM NAM HƯNG,
1LÊ VĂN DŨNG, 1MAI XUÂN BÁCH, 1THÁI ANH TUẤN, 3CAO ĐÌNH TRỌNG

1Institute of Geophysics, VAST, 18 Hoàng Quốc Việt, Cầu Giấy, Hà Nội;
2Dept of Earth Sciences, University of Trieste, Italy;
3Peoples Friendship University of Russia, Moscow

Abstract: The catalogue of earthquakes in the territory of Việt Nam established to the end of 2003 is based on the ISC, NOAA and NEIC databases. The total amount of 30 seismogenic zones could be determined on the territory of Việt Nam and surrounding areas. Among that, the high rank of the earthquake activity includes: Mường Tè (MS = 7.1), Sông Đà - Sơn La (MS = 6.7), Sầm Nưa - Thái Hòa (MS = 6.8), Sông Cả - Rào Nậy (MS = 6.8). The scenarios of seismic hazard pictures for the whole territory have been showed in this paper. The highest DGA value of Việt Nam mainland is the Northwest Region, Bình Thuận Province and a part of the Hà Nội Basin, with DGA in the range of 0.150-0.350 g which corresponds to the maximum earthquake intensity - VIII in MM scale.


I. INTRODUCTION

The bilateral project "Establishing approaches to increase earthquakes preparedness in Việt Nam (Index 10EE1)" between Department of Earth Sciences, University of Trieste, Italy and Institute of Geophysics, VAST, Việt Nam had been approved on July 10-11, 2002. The main objective of the Cooperation Project is to enhance the capability in decreasing vulnerability of Việt Nam to earthquakes by establishing appropriate approaches for data acquisition and their analysis. The Project includes the following three key elements necessary for the reduction of damage from earthquakes:

- Characterization of the seismotectonic framework of Việt Nam through data acquisition and building/updating of a seismological-geological-geophysical database;

- Realistic modelling of seismic ground motion as the base for pre-disaster activities (hazard prediction, risk assessment, and their mapping); and 

- Intermediate-term medium-range earthquake prediction, providing the base for earthquake preparedness.

This bilateral project brings a big long-term benefit in the field of seismic study in Việt Nam. More progress has been obtained in the last 3 years of time limit. But in this paper, the authors introduce some informations about seismic activity and seismic hazard parameters on the basis of neo-deterministic approach in the Việt Nam territory and surrounding areas. Specially to emphasize the following remarks:

- Establishing the Việt Nam catalogue of the earthquakes;

- Identification of seismic zones; and

- Seismic hazard assessment in Việt Nam.    

II. THE EARTHQUAKE CATALOGUE OF VIỆT NAM

1. The Catalogue of Earthquakes of the Institute of Geophysics to the end of 2003

The Catalogue of Earthquakes of the Institute of Geophysics (VNCAT), VAST to the end of 2003 was established on the basis of three data sources as follows:

- Catalogue of Historical Earthquakes up to 1900.

- Catalogues of Macroseismic Data, investigating in public documentation (1900-1976).

- Earthquakes recorded from seismic network of Việt Nam (since 1963).

The VNCAT catalogue reports an estimation magnitude for each event. Magnitudes can be of different type (from intensity, from surface waves, local magnitude, and duration magnitude) depending on the source data. The reference magnitude is MS.

2. Comparison of different catalogues for establishment the sufficient catalogue of earthquakes on the Việt Nam territory to the end of 2003

Sufficient catalogue of earthquakes on the Việt Nam territory established to the end of 2003 is based on documentary sources and methodology of comparison of different catalogues as follows [15, 16]:

A. Software used for comparison of different catalogues

The following softwares are used for comparison of different catalogues:

- EDCAT - to edit catalogue and transform it into standard format;

- CATAL - to select sub-catalogues, merge and compare catalogues;

- HIST - to make histograms for any parameter of catalogue.

These softwares provide various facilities for data analysis.

B. Comparison of different catalogues and establishing the catalogue of earthquakes in Việt Nam to the end of 2003:

a. The comparison performed among the NOAA, ISC and NEIC data sets for the Việt Nam region. We had compiled an earthquake catalogue for Việt Nam bounded by the time interval: 1446-2003 and covers an area approximately within Lat: 4.63 - 23.30 N, Lon: 100 - 118 E.

In order to perform the magnitude comparison, the events common to different catalogues are identified according to the following rules: a) time difference Dt £ 1.00 Min; b) DLat = DLon £ 0.50 degree; and c) DM £ 9.00; DH £ 999.00 km (no limitation imposed on magnitude or depth differences).

- The ISC catalogue is preferable for the time interval after 1994, since it contains more events while only a few are missing with respect to the other data sets.

- Before 1994 NOAA is preferable to NEIC, since NEIC contains only 47 additional events, but all of them have epicenter outside Việt Nam.

- NOAA contains also information about historical events (before 1900 - 34 events).

b. Enlist all the data sets available and description (area, time interval, number of events, type of magnitude, etc.).

Description of the new VNCAT catalogue: by time interval from 1278 to 2003 and covering an area approximately within Lat: 4.63 - 23.30 N, Lon: 100 - 118 E. The catalogue contains about 2610 events with Ms: from 0 to 7.50; depth from 0 to 350 km.

Description of the NEIC-VNCAT catalogue NE20.dat (its format - 20), we have compiled an earthquake catalogue for Việt Nam bounded by the time interval: 1918-1999 and covering an area approximately within Lat: 4.63 - 23.30 N, Lon: 100 - 118 E. The catalogue contains 249 events with: magnitude - from 0 to 6.70; depth – from 0 to 350 km; in NEIC catalogue used kind of magnitude: Mb, Ms, Ml, and Mw. Since NEIC contains only 47 additional events, but all of them have epicenter outside Việt Nam.

Description of the ISC-VNCAT catalogue IS20.dat (its format - 20), we have compiled an earthquake catalogue for Việt Nam bounded by time interval: 1964-1997 and covering an area approximately within Lat: 4.63 - 23.30 N, Lon: 100 - 118 E. The catalogue contains 387 events with: magnitude - from 0 to 6.70, depth – from 0 to 350 km. In this catalogue used kind of magnitude: Mb, Ms, Ml, and Md (Md = duration magnitude).

Description of the VNCAT-NOAA catalogue: We compare the Việt Nam catalogue and NOAA one. The catalogue compiled for the Việt Nam territory spans the time interval 1137-2003 and covers an area approximately within Lat: 4.63 - 23.30 N; Lon: 100 - 118 E. The catalogue, structured according to the standard 20 binary format, is stored in the file NO20.DAT. The starting point has been provided by the Việt Nam catalogue, referred as VN hereinafter, has been checked and corrected for time ordering and formal mistakes (e.g. seconds = 60), events from the NOAA dataset (SEASIA) have been selected for the Việt Nam territory: Lat: 4.63 - 23.30 N; Lon: 100 - 118 E. The time interval covered by the NOAA data is 1900-1995. The catalogue is obtained adding the events from NOAA to those reported in the VN catalogue. Comparing the catalogues we observe that there are 793 events in NOAA that are not reported in VNCAT. In this catalogue used kind of magnitude: Mb, Ms, Ml, Mw and MR = Rautian magnitude Kondorskaya and Shebalin, 1982.

 Therefore a new catalogue has been then obtained adding the events from NOAA to those reported in the VNCAT catalogue. Formally identical events have been removed from the initial VNCAT and NOAA catalogues. Then the NOAA data are merged into the VNCAT data, giving the priority to the VNCAT catalogue. Practically, whenever similar events are found only events from the VNCAT catalogue are retained [1]. If for such events no magnitude is reported, then the maximum magnitude provided by NOAA is placed in the MP position. The analysis of the completeness of the resulting catalogue VNCAT-NOAA seems to indicate that it can be considered rather complete for magnitude of 3.0 and above.

The sufficient catalogue of earthquakes in Việt Nam to the end of 2003 contains 3044 records.

III. IDENTIFICATION OF SEISMIC ZONES

1. Distribution of earthquakes

Although some earthquake occurrences have been recorded at high magnitude, but research work was poorly conducted, in some cases, the seismic depth and magnitude could not be determined properly. Parameters of some earthquake events were determined at the highest reliability as follows [3, 9, and 10]:

1. Earthquake occurrence in the Điện Biên area (1935) - M=6.8, occurring in 23 h 22' (Hà Nội time) 1st Nov. 1935 in the southeast of the Điện Biên City. It damaged heavily living houses in the Điện Biên and Sơn La provinces.

2. Earthquake in the Lục Yên (Yên Bái) 1953-M=5.4.

3. Earthquake in the Lục Yên (Yên Bái) 1954-M=5.4, the earthquake epicenter was located quite near to that occurring in 1953. These two earthquake events occurred at the same seismic intensity but the width of isoseismic (1954) was narrower and its length was longer.

4. Earthquake in the Bac Giang, 1961-M=5.6, which occurred at 16 h 58' (Hà Nội time) in the 12th Jun, 1961 in the location 11 km of the Bắc Giang City to the northeast.

5. Earthquake in Sông Cầu, 1970-M=5.3. Sông Cầu earthquake occurred in 12th April, 1970 near the Sông Cầu Townlet, Nghĩa Bình Province. This was one of the two strongest earthquakes happening in the territory of South Việt Nam.

       6. Sông Cầu earthquake in 1972-M=5.3. The event happened on the 24th May, 1972 in the area near to the Sông Cầu Townlet. The earthquake epicenter nearly coincids with that happening in 1970 and they had the same seismic intensity.

7. Tuần Giáo earthquake 1983-M=6.7. It happened in 14 h of the 24th Jun., 1983, 11 km northeast of the Tuần Giáo Townlet, causing heavy losses to the Tuần Giáo district and surrounding areas (Nguyễn Đình Xuyên, Cao Đình Triều, 1990). After the event, series of aftershocks occurred. The strongest aftershock occurred in 15th July 1983 in the same place of maximum magnitude M = 5.4.

8. The Mường Luân Ms5.0 earthquake in the 23rd Jun., 1996. The epicenter of this event is 21o26¢08 N, 103°32 E, the focus depth is about 12 km.

9. The Thin Tóc Ms5.3 earthquake of the 19th Feb., 2001. The epicenter of this event is 21°39 N, 102°83 E; the focus depth is about 12.3 km.

2. Identification of various levels of the earthquakes

The level of the earthquake activity has been divided into 5 ranks:

1- Feeble, MS < 4.0;

2- Low, MS = 4.0 ¸ 4.9;

3- Moderate, MS = 5.0 ¸ 5.9;

4- High, MS = 6.0 ¸ 6.9; and

5- Large, MS ³ 7.0.

On the Việt Nam territory, there were only earthquakes of the first 4 ranks: feeble, low, moderate and high ones.

3. Identification of active fault zones and seismogenic fault zones

This analysis focused on determining active fault zones, which are earthquake sources. Six groups of seismogenic fault zones characterized by potential to generate earthquakes were determined. They are as follows:

1- Non-seismogenic fault zones, underneath that there had not been any earthquake generated so far.

2- Feeble seismogenic fault zones, that are active fault zones where earthquakes are generated with the magnitude less than 4.0 (MS < 4.0).

3- Low seismogenic fault zones, that are active fault zones where earthquakes are generated with the magnitude of from 4.0 to 4.9 (MS = 4.0 ¸ 4.9).

4- Moderate seismogenic fault zones, that are active fault zones where earthquakes are generated with the magnitude of from 5.0 to 5.9 (MS = 5.0 ¸ 5.9).

5- High seismogenic fault zones, that are active fault zones where earthquakes are generated with the magnitude of from 6.0 to 6.9 (MS = 6.0 ¸ 6.9).

6- Large seismogenic fault zones, that are active fault zones where earthquakes are generated with the magnitude equal or more than 7.0 (MS ³ 7.0).

The main seismogenic fault zones with the earthquake magnitudes more than 5.0 on the Việt Nam territory and surrounding areas have been determined.

4. Seismogenic zones on the Việt Nam territory and surrounding areas

a. Principles of identification of seismogenic zones

For identification of seismogenic zones the following principles are used:

1. The possible earthquake genesis zones are that active faults or a system of tectonic active faults where the tectonic movement was quite differentiated. The possibilities of earthquake occurrences in deep faults depend on their scope, characteristics and intensity of tectonic activities. The most likely earthquake occurrences (seismic activities are stronger, more regularly happened) are the marginal deep faults, which are bounded by the neotectonic structural zones. Earthquake could occur inside (internal part) of fault zones, but the intensity is weaker.

2. The width of earthquake genesis zones and relative location in comparison with the projection profile of the fault on the surface depend on the movement style, dipping direction of the faults and thickness of active layers.

3. Based on the extrapolation principles the faults are regarded as having the same characteristics and the possibility of earthquake genesis is the same.

The analysis resulted in classification of the study areas into seismogenic classes based on the combination of 4 factors, including: seismogenic fault zones, seismotectonic structure zones, focal source parameters, and seismic stream density zone [1-8, 17-28].

b. Seismogenic zones        

According to the study results obtained from the above-applied method 30 seismogenic zones could be determined on the Việt Nam territory and surrounding areas: 1. The strongest earthquake occurring in the Mường Tè seismogenic zone with the magnitude MS=7.1; 2. Phong Sa Li (MS=6.8); 3. Ou Dom Xai (MS=6.8); 4. Lai Châu - Điện Biên (MS=5.3); 5. Xiao Jiang (MS=6.8); 6. Sông Hồng (Red River) (MS=5.3); 7. Sông Đà - Sơn La (MS=6.7); 8. Sam Nua - Thái Hòa (MS=6.8); 9. Sông Cả - Rào Nậy (MS=6.8); 10. A Lưới - Tha Khet (MS=6.0); 11. Gia Lam - Đồng Hới (MS=5.1); 12. Bắc Giang - Hải Dương (MS=5.6); 13. Quản Bạ - Bắc Cạn (MS=5.2); 14. Cao Bằng - Lộc Bình (MS=5.8); 15. Nam Ninh (MS=5.9); 16. Lingshan - Hạ Long (MS=6.8); 17. Huyền Nhai - Vạn Ninh (MS=7.5); 18. Châu Giang (MS=5.4); 19. North Hoàng Sa (MS=6.8); 20. Hoàng Sa (MS=5.9); 21. Ba Tơ - Củng Sơn (MS=6.0); 22. Thuận Hải - Minh Hải (MS=7.0); 23. South Côn Sơn (MS=6.1); 24. East Phú Khánh (MS=5.8); 25. East Biển Đông (MS=5.9); 26. Guangzhou (MS=6.4); 27. Shabah (MS=6.0); 28. Kiên Giang (MS=5.5); 29. Southeast Thailand (5.0); and 30. Malaysia (4.9).

IV. SEISMIC HAZARD ASSESSMENT OF VIỆT NAM TERRITORY ON THE BASIS OF NEO-DETERMINISTIC APPROACH

In Việt Nam, for seismic hazard assessment, the method of shake-ability (Riznichenko Yu.V., 1968) and the Cornell method of probabilistic analysis have been used. Seismic hazard is the probability of occurrence of seismic intensity I (shaking intensity I, PGA, PGV or displacement D). It may be expressed by the maps of seismic intensity zoning with different recurrence periods or with the probability of accidence within different period of time [10-14].

Microseismic map for urban area has been only established for Hà Nội area. In this project the calculation and mapping of seismic hazard parameters are carried out by using the probabilistic analysis method (Cornell & Allin model) and Mc Guire program EQRISK to estimate PGA values (with probability 10 % of exceed within 20, 50, 100 years).

The international cooperation activities have been carried out on dealing with SHA in region is the "Global Seismic Hazard Assessment Program in Continental Asia - GSHAP" which has been accomplished for the whole Asia Continental region at large scale. As the primarily results, the Việt Nam territory has been roughly studied and estimated the SHA. In general, the GSHAP is almost concerned with the marine region and the northwest area of Việt Nam territory. The remained region of Việt Nam mainland is still not covered in this program. Besides, there are some projects dealing with SHA for a specific region in Việt Nam, such as: Seismic hazard assessment and seismic micro-zoning of the Hòa Bình hydropower station area (Steinberg V. V, Ersov I. A., Nguyen Dinh Xuyen, 1976), Seismic zoning of the territory of Việt Nam (V. N. Ibragimov, Nguyen Dinh Xuyen, Viet Nam - Uzbekistan Cooperation project 1980-1985) and other more projects concerned with SHA, but these studies were only applied for very specific areas in Việt Nam [11, 12].

The Neo-Deterministic Seismic Hazard Assessment (DSHA) is approached in Việt Nam in 2002 in order to fulfill the Bilateral Project cooperation between Việt Nam and Italian Scientists "Establishing approaches to increase earthquakes preparedness in Việt Nam – Index 10EE1".

The advanced characters of applying the DSHA approach possibly address aspects largely overlooked in the probabilistic seismic hazard assessment (PSHA) ones, such as:

- Direct evaluation of resulting maps in term of design parameters, without requiring the adaptation of probabilistic maps to design ground motions;

- Effect of crustal properties on attenuation;

- Derivation of ground motion parameters from synthetic time series, instead of using only simplified attenuation functions; and

- Generalization of design parameters to locations where there is little seismic history.

The procedure of Neo-Deterministic Seismic Hazard Assessment (DSHA) is based on the computation of synthetic seismogram by the modal summation technique and has been applied for several countries in the world. The hazard is computed in terms of peak ground displacement (D), peak ground velocity (V) and design ground acceleration (DGA) using the neo-deterministic approach (Costa et al., 1993). The numerical synthesis of the ground motion, taking into account the source, the wave propagation path and the local site geology, represents the key element for the ground motion predictions. Complete P-SV and SH seismograms are generated by modal summation technique (Panza, 1985; Florsh et al., 1991) on a regular grid covering the whole Việt Nam territory. The synthetic signals are computed with the cut-off frequency of 1 Hz in the point source approximation. The signals are properly scaled to the finite dimension sources. The effect of the source focal mechanism is taken into account. As the primarily results applied the DSHA has been established to generate the ground-shaking scenario, the distribution of peak values of displacement (D), velocity (V) and design ground acceleration (DGA).

*** Preparing the parameter of Fault Plane Solution file (*.fps),

Normally we define the seismogenic zones basing on fundamental data, such as: crustal structure, tectonic, seismotectonic and earthquake distribution in regarding to select one the most appropriate solution focal mechanism in each zone. In fact, to select the focal parameter that is extracted directly from detailed study on fault parameters. In this field, the active fault (seismic fault) is considered as the dominating the dynamics parameters of earthquake (focal mechanism), in addition of the experience and expert's mindset in considering the data set.

In order to define focal parameters, there are some of these parameters extracted through seismograph by the wave-form inversion program, but these results are not specific enough to present for entire seismogenic zones in Việt Nam territory.

*** Preparing the catalogue (*.dat)

It is established based on the basically source of Việt Nam in caparisoning and combining between variant sources, such as: NOAA, NEIC, ISC and USGS. Generally, all these procedures are executed on the softwares EDCAT, HIST, CAT cause of editing, combining, merging and caparisoning between data sources. The detailed results have been mentioned in the above.

*** In order to define the seismogenic zones (*.pos) we almost use the most recently upgraded date form Geological, Geophysical, Seismic, Seismotectonic database. For identification of seismogenic zones, the following principles are used:

- Possible earthquake genesis zones, that were the active faults or a system of tectonic active faults where the tectonic movement is quite differentiated. The possibilities of earthquake occurrences in deep faults depend on their scope, characteristics and intensity of tectonic activities. The most likely earthquake occurrences (seismic activities are stronger, more regularly happened) are marginal deep faults, which are bounded by neotectonic structural zones. Earthquake could occur inside (internal part) of faulted zones but the intensity is weaker.

- Width of earthquake genesis zones and relative location in comparison with the projection profile of the fault on the surface depending on the fault movement style, dipping direction of the faults and thickness of the active layers. Based on the extrapolations principle the faults are regarded as having the same characteristics and the same possibility of earthquake genesis.

- Analysis resulted in classification of the study areas into seismogenic classes based on the combination of 4 factors, including: seismogenic fault zones, seismic tectonic structure zones, focal source parameters, and seismic stream density zone. According to the studied results obtained from the above-applied method 30 seismogenic zones could be determined in the territory of Việt Nam and surrounding areas as the above mentioned.

Figure 1. Maximum displacement (Dmax) in the mainland of Việt Nam territory

Figure 2. Maximum velocity (Vmax) in the mainland of Việt Nam territory


Figure 3. Design Ground Acceleration (component for max between .sns and .sew)


V. DESCRIPTION OF SOME PRIMARY NEW RESULTS ABOUT SEISMIC ZONING FOR VIỆT NAM TERRITORY BASED ON THE NEO-DETERMINISTIC APPROACH

Design Ground Acceleration (DGA) values are computed using synthetic response spectra together with design response spectra (the default is EC8) for A, B and C. Structural models in a default run are by definition soils A, since the lowest velocities are anyway larger than 900 m/s (other important factor such as PGV, PGD). The results showed in the Figs. 1, 2 and 3, where: D-Pick ground displacement; V- Pick ground velocity; and DGA- Design ground acceleration.

The southern part of the Việt Nam mainland region (from Binh Trị Thiên structure unit to the south) is a quite stable region with the lower DGA values (£ 0.020g) which correspond to the IV-Earthquakes Intensity in MM scale. The highest DGA values in this region belongs to the north part of the Hà Tiên structure zone with the maximum DGA values of about 0.015-0.020 g (corresponding to earthquake intensity-IV in MM scale). The southeast part of the Kon Tum and Đà Lạt zone are slightly higher DGA values, which is approximately 0.040 g. The maximum DGA values of Bình Thuận Province is about 0.300 g. The other remaining units have the lowest value with DGA values of 0.005-0.015 g.

The Northeast Việt Nam region is quite stable area also with the DGA value of in range 0.005-0.015 g. The highest DGA value in the Việt Nam mainland is the Northwest Việt Nam Region and a part of the Hà Nội Basin structural unit, with the DGA values in range of 0.150-0.35 g, which correspond to the maximum earthquake intensity-VIII in MM scale.

VI. CONCLUSIONS

The used documents for this work are the latest data that have been possessed by the Institute of Geophysics, VAST. The above said results show that:

1. The catalogue of earthquakes on the territory of Việt Nam established to the end of 2003 is based on the ISC, NOAA and NEIC databases and the softwares EDCAT, CATAL and HIST. For the first time, the sufficient catalogue (VNCAT catalogue) of earthquakes has been established in Việt Nam. This is the very important and fundamental documentary source for seismic hazard and risk assessments. 

2. The Điện Biên 1935-M=6.8 and Tuần Giáo 1983-M=6.7 earthquakes are the two strongest ones that happened in the Việt Nam mainland in the 20th century. These events caused heavy losses to the Điện Biên and Sơn La provinces.

3. The total amount of 30 seismogenic zones could be determined on the territory of Việt Nam and surrounding areas; among that, the high rank of the earthquake activity are: Mường Tè (7.1), Xiao Jiang (MS=6.8), Sông Đà - Sơn La (MS=6.7), Sam Nua - Thái Hòa (MS=6.8), Sông Cả - Rào Nậy (MS=6.8), Lingshan - Hạ Long (MS=6.8), Huyền Nhai - Vạn Ninh (MS=7.5), Guangzhou (MS=7.3), and North Hoàng Sa (MS=6.8).

4. The scenarios of seismic hazard pictures for the whole territory are showed including: Mo-Magnitude distribution, M- Magnitude of seismogenic zones (after discrimination and smoothing), PGD- Pick ground displacement, PGV- Pick ground velocity, DGA- Design ground acceleration. The highest DGA value of the Việt Nam mainland is the Northwest Region, Bình Thuận province and a part of the Hà Nội Basin, with DGA in range of 0.150-0.350 g which correspond to the maximum earthquake intensity-VIII in the MM scale.

The authors would like to express special thanks to the Italian Ministry of Foreign Affairs, Italian Embassy in Hà Nội, SAND of ICTP, DST of University of Trieste, Việt Nam Ministry of Foreign Affairs, MOST, VAST and IGP of VAST for the help and facilities provided in the process of the project implementation. 

REFERENCES

1. Cao Dinh Trieu, 1997. Structure and stress pattern of the Earth crust of Việt Nam territory. Contr. Inst. of Geophysics from 1987 to 1997, p. 322-352 Hà Nội (in Vietnamese).

2. Cao Đình Triều, Nguyễn Danh Soạn, 1998. Fault system of Việt Nam territory from gravity, magnetic and satellitte data. J. of Geology, A/247 : 17-27. Hà Nội (in Vietnamese).

3. Cao Đình Triều, 1999. Seismic active faults of Central Region of Việt Nam. Contr. of Oceanic geol. and geoph., V : 234-248, Hà Nội (in Vietnamese).

4. Gatinsky Yu. et al., 1984. Tectonic evolution of Southeast Asia. Tectonic of Asia, 27th  IGC, 5 : 225-241. Moscow.

5. Flower M. F. J. et al., 1992. Magmatism in the South China Sea Basin, 2. Post-Speeding Quaternary basalts from Hainan Island, South China. Chem. Geol., 97.

6. Hall R., 1996. Reconstructing Cenozoic SE Asia. Tectonic evolution of SE Asia. Geol. Soc. Spec. Publ., 106.

7. Keilis-Borok V.I., Rotwain I.M., 1990. Diagnosis of time of increased probability of strong earthquakes in different regions of the world. Algorithm CN, PEPI, 61 : 57-72.

8. Lê Duy Bách, 1986. Tectonic evolution of the Earth's crust in Indochina. J. of Geology, A/176-177 : 25-39. Hà Nội (in Vietnamese).

9. Lê Tử Sơn, Nguyễn Thị Cẩm, 2002. Re-evaluation of the depth and the magnitude of earthquakes detected by macroseismic investigations (1903-1962). J. of Sci. of the Earth, 24/3 :  227-232 (in Việt Nam).

10. Nguyễn Đình Xuyên, 1992.  Seismic zoning of the territory of Việt Nam. Proc. of the NCSR of Việt Nam, 4/2 : 105- 110.

11. Nguyễn Đình Xuyên (Ed.), 1992-1996. Seismic hazard assessment of the territory of Việt Nam  (scale 1/1.000.000).  National Proj., VN NCST.

12. Nguyễn Đình Xuyên, Trần Thị Mỹ Thành, 1999. A formula for estimation of Seismic Peak Ground Acceleration (PGA) in Việt Nam. J. of Sci. of the Earth, 21/3. Hà Nội.

13. Nguyen Hong Phuong, 1991. Probabilistic assessment of earthquake hazard in Việt Nam based on seismotectonic regionalization. Tectonophysics, 81-93.

14. Nguyễn Hồng Phương, 1997. Probabilistic earthquake hazard assessment for Việt Nam and adjacent regions. Proc. of the NCST of Việt Nam, 9/1 : 115-130. Hà Nội.

15. Peresan A., I.M. Rotwain, IC/98/97. Analysis and definition of magnitude selection criteria for NEIC (PDE) data, oriented to the compilation of a homogeneous updated catalogue for CN monitoring in Italy. Preprint.

16. Rotwain I., O. Novikova, 1999. Performance of the earthquake prediction algorithm CN in 22 regions of the World. PEPI, 111 : 207-213.

17. Tapponier P. et al., 1982. Propagating extrusion tectonics in Asia: New insights from simple experiments with plasticen. Geology, 10.

18. Tapponier P. et al., 1986. On the mechanics of the collision between India and Asia. In : M.P. Coward and A.C. Ries (Eds). Collision tectonics. Geol. Soc. Lond., Spec. Publ. :115-157.

19. Taylor B., Hays D.E., 1980. The tectonic evolution of the South China Sea Basin. In : The tectonic and geologic evolution of SE Asian seas and islands ". Geoph. Mon., 23.

20. Tija H.D., Liew K.K., 1996. Changes in tectonic stress field in northern Sunda Shelf basins. In: Tectonic evolution of SE Asia.

21. Trần Văn Trị et al., 1986. The main tectonic features of Việt Nam. Proc. 1st Conf. Geol. Indoch., I : 363-376, GDG Việt Nam, Hà Nội.

22. Tran Van Tri, 1987. Tectonic evolution of the Indosinian epoch of Việt Nam and neighbouring regions. Rep. 2, IGCP-24, p. 67-74, Osaka.

23. Trifonov V.G., Machette M.N., 1993. The World Map of major active faults project. Annali di Geoph., XXXVI /3-4 : 225-236.

24. Van De Mene E.A., 1982. An evaluation of Quaternary geological investigations for the development of SE Asia countries. Proc. 4th  Conf. Geol. SE Asia, p. 1-8. Manila.

25. Workman D.R., 1975a. Tectonic evolution of Indochina. J. Geol. Soc. Thailand, 1 : 3-19, Bangkok.

26. Workman, D.R., 1975b. Extent of Mesozoic marine sedimentation and Indosinian (Triassic) fold-belts in Eastern Thailand and Indochina. Dept. Geol. Sci. Univ., Chiang Mai, Spec. Pub., 1/2 : 51-60. Bangkok.

27. Workman D.R., 1977. Geology of Laos, Cambodia, South Việt Nam and Eastern part of Thailand. Overseas Geol. Min. Res., 50, 33 p.. London.

28. Yang Zigeng, Lin Hemao, 1993. Proposals for Quaternary correlation in China and adjacent areas. ESCAP Atlas of strat. XIII. UN, New York.