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In this study, the three terms related to the seismic activities of the Sagaing Fault Zone (SFZ), central Myanmar, of the possible maximum magnitude, return period, and probability of exceedance (POE) of an earthquake of given magnitude were evaluated and mapped using an improved earthquake catalog (free of duplicate records, foreshocks, aftershocks and recording artifacts) and implementation of a statistical approach. As a result, the SFZ was separated into five segments with different seismicity levels. The highest hazard level was found for the segment between Myitkyina–Northern Mandalay, with a likely generation of an Mw 6.4–7.2 earthquake in the next 50 years. For the Naypyidaw–Bago segment, the hazard levels were in the comparatively medium range with a magnitude 6.0–7.0 Mw earthquake return period of 20–50 and 100–200 years, respectively. The Offshore Andaman Sea segment of the SFZ was defined to have the lower hazard, with only a 10% or lower POE of a 7.0 Mw earthquake within the next 50 years. Therefore, effective mitigation plans should be prepared for this area and in particular for the region nearby to the Myitkyina–Northern Mandalay segment as the highest earthquake-prone area.

The seismicity for 35 natural caves in Thailand was investigated probabilistically in order to provide information on their potential earthquake situation. All values representing the earthquake activities within a 300-km radius and the seismic hazard level at each cave were clarified. Seismotectonically, 28 of the 35 caves are situated within previously proposed seismic source zones and most of the seismogenic faults nearby each cave is presently still active, as determined by seismicity and paleoseismological evidence. For the present-day seismicity, the Pla cave in northwest Thailand (situated 0.3[Formula: see text]km from the Mae Hong Son-Tak fault) showed a comparatively high [Formula: see text]-value (4.16) suggesting a high entire seismicity rate, but a relatively high [Formula: see text]-value of 0.82. With respect to the [Formula: see text]-value, which inversely represents the accumulated seismotectonic stress, the caves at Pha Puang, Lom-Wang, Naresuan and Fha Mue Daeng in the Central-North regions had a comparatively low [Formula: see text]-value ([Formula: see text]), indicating a high accumulated stress. Based on the recognized earthquake sources and the utilized strong ground-motion attenuation model, the seismic hazard analyses revealed that the caves at Daowadeung, Phra Thart and Lawa in Western Thailand were in the highest seismic hazard areas. This new study contributes to important information for geotourism (e.g. mitigation planning) and selecting/prioritizing speleoseismological investigation sites.

In this study, the possibility of detecting a significant seismicity rate change prior to a hazardous earthquake was examined along the Indonesian Sunda margin (ISM), Indonesia, using the seismological Z value method. The completeness inter- and intraplate seismicity data with a Mw ≥ 4.0 recorded during 1980–2016 was the dataset analyzed in this study. Based on an iterative test with 13 major or great earthquake case studies, the most suitable free parameters for detecting the precursory seismic quiescence by Z value analysis along the ISM were N = 25 events and Tw = 2.5 years. Investigation of the Z value in both temporal variation and spatial distribution revealed at least seven areas along the ISM with prominent Z value anomalies that are still quiescent from any hazardous earthquake and so are potential earthquake sources. These are northern and southern Praya, northern and southern Bajawa, eastern Dili, southern Ambon and southeastern Palu. Three of these seven areas (northern Praya, northern Bajawa and southwestern Pala) conform fairly well to the previously proposed eight risk areas in the Indonesian island chain derived from analysis of the b value of the frequency–magnitude distribution model. Therefore, it is concluded that there is a high possibility in the near future of seismic and/or tsunami hazard impact in the Indonesian island chain due to ISM seismic activities.

Locating suitable caves and stalagmites for palaeoenvironmental and palaeoclimatic studies can be challenging. Isotopic geochemical analyses, albeit commonly performed for palaeoclimatic reconstruction, are also time consuming and costly. Therefore, petrographic and non‐destructive morphological studies on speleothems are desirable to facilitate sample selection for further analysis. In this study, 20 caves were surveyed in Ban Rai district, Uthai Thani province in western Thailand. After external physical observations in the field, three stalagmite samples were collected from Tham Nam Cave to test their potential for palaeoclimatic research. Firstly, the stalagmites were scanned by X‐ray computed tomography (CT scanning) and subsequently the CT images were compared with petrographic inspections. Columnar fabrics show the highest density, whereas closed and open dendritic fabrics have medium and the lowest densities, respectively. Layers near the top and bottom of the three stalagmites were dated by U‐Th mass spectrometric techniques. All three samples were deposited between c. 87 and c. 105 ka ago; therefore, they are probably the oldest stalagmites that have been reported so far from mainland Southeast Asia. However, their physical features indicate that all the samples have suffered from postdepositional dissolution, and are unlikely to be suitable for palaeoclimatic research. The internal dissolution feature of stalagmites, however, cannot be identified by visual inspection of uncut samples. We hereby argue that CT images are useful to characterize stalagmite petrography, in particular fabric, porosity and density. Such features can be used to select the ideal plane of a stalagmite for sectioning, to maximize the chances of robust climatic reconstruction. NRF (Natl Research Foundation, S’pore) Accepted version

To study the prospective areas of upcoming strong-to-major earthquakes, i.e., M w ≥ 6.0, a catalog of seismicity in the vicinity of the Thailand-Laos-Myanmar border region was generated and then investigated statistically. Based on the successful investigations of previous works, the seismicity rate change (Z value) technique was applied in this study. According to the completeness earthquake dataset, eight available case studies of strong-to-major earthquakes were investigated retrospectively. After iterative tests of the characteristic parameters concerning the number of earthquakes (N) and time window (T w ), the values of 50 and 1.2 years, respectively, were found to reveal an anomalous high Z-value peak (seismic quiescence) prior to the occurrence of six out of the eight major earthquake events studied. In addition, the location of the Z-value anomalies conformed fairly well to the epicenters of those earthquakes. Based on the investigation of correlation coefficient and the stochastic test of the Z values, the parameters used here (N = 50 events and T w = 1.2 years) were suitable to determine the precursory Z value and not random phenomena. The Z values of this study and the frequency-magnitude distribution b values of a previous work both highlighted the same prospective areas that might generate an upcoming major earthquake: (i) some areas in the northern part of Laos and (ii) the eastern part of Myanmar.

The earthquake activities along the Indonesian Sunda Margin, which is delineated parallel to the Indonesian Island chain, were statistically investigated. Utilizing the obtained completeness earthquake catalogue, the mapped spatial distributions of the (i) possible maximum magnitude, (ii) return period, and (iii) probability of exceedance of an earthquake of a given magnitude revealed that the Indonesian Island chain could be classified into three different hazard level groups. The highest hazard level was located along the segment of Padang to Jakarta, surrounding Ambon, and northeastern Palu, whereas the southwestern Yogyakarta, southwestern Bajawa, and Dili, were classified as an intermediate hazard level. Although Makassar, southern Praya, southern Bajawa, and southeastern Dili was classified as a relatively low hazard area (compared to the other areas in the Indonesian Island chain), a major earthquake (7.0 Mw) is still likely to occur with 10–20% probabilities in the next 50 years. Therefore, the contribution of suitable local mitigation plans for both seismic and tsunami hazards are strongly recommended for all the different regions within the Indonesian Island chain.

In this study, the quiescence stage of seismicity prior to seven strong-to-major earthquakes posed along the Sagaing Fault Zone (SFZ), Central of Myanmar were evaluated using the Region-Time-Length (RTL) algorithm. After improving the completeness of the earthquake catalogue, the suitable characteristics of RTL parameters were tested retrospectively with seven strong-to-major earthquakes available in the catalogue. According to the iterative test, the parameters r0 = 150 km and t0 = 3 y were suitable for detecting the precursory seismic quiescence along the SFZ. Consequently, with the implementation of these parameters and the present-day seismicity data of 1960–2015, the quiescence maps obtained indicated that western Myitkyina and the area in the vicinity of the Naypyidaw segments of the SFZ are at risk from future earthquakes. Therefore, effective mitigation plans should be developed.

This study focused on the seismic activities in the Philippines Islands and the adjacent areas where the inter- and intra-plate seismic sources are prevalent. To access this, the frequency-magnitude distribution model was employed with the completeness seismicity data. Then, the possible maximum magnitude, return period and probability of earthquake occurrence, including the prospective areas of upcoming earthquakes, were evaluated. The results indicated that eastern Taiwan is among the most seismic-prone areas. The most probable largest magnitude of earthquakes was estimated to be up to 8.0 Mw in a time period of 50 years, giving return periods of

In this study, the seismic quiescence prior to hazardous earthquakes was analyzed along the Sumatra-Andaman subduction zone (SASZ). The seismicity data were screened statistically with mainshock earthquakes of M w ≥ 4.4 reported during 1980–2015 being defined as the completeness database. In order to examine the possibility of using the seismic quiescence stage as a marker of subsequent earthquakes, the seismicity data reported prior to the eight major earthquakes along the SASZ were analyzed for changes in their seismicity rate using the statistical Z test. Iterative tests revealed that Z factors of N = 50 events and T = 2 years were optimal for detecting sudden rate changes such as quiescence and to map these spatially. The observed quiescence periods conformed to the subsequent major earthquake occurrences both spatially and temporally. Using suitable conditions obtained from successive retrospective tests, the seismicity rate changes were then mapped from the most up-to-date seismicity data available. This revealed three areas along the SASZ that might generate a major earthquake in the future: (i) Nicobar Islands (Z = 6.7), (ii) the western offshore side of Sumatra Island (Z = 7.1), and (iii) western Myanmar (Z = 6.7). The performance of a stochastic test using a number of synthetic randomized catalogues indicated these levels of anomalous Z value showed the above anomaly is unlikely due to chance or random fluctuations of the earthquake. Thus, these three areas have a high possibility of generating a strong-to-major earthquake in the future.

The seismic activity and hazard level in northern Thailand, including at the Mae Moh Coal Mine (MMCM), were clarified. For the probability of exceedance (POE), Chiang Mai, Lamphun, and Lampang provinces have a 70–90% and 20–40% POE of a MW-5.0 and MW-6.0 earthquake, respectively, in the next 50 y. In the case of a MW-7.0 earthquake, the POE is less than 10% in the whole study area. Regarding the probabilistic seismic hazard analysis, the ground shaking maps indicated that the southeastern part of the MMCM and northwestern part of Phayao provinces were high hazard areas, with an earthquake ground shaking of around 0.28–0.32g and 0.18–0.24g for a POE of 2% and 10%, respectively, in the next 50 y. In addition, the probability maps revealed that these high hazard areas showed a 60–80% and 30–40% POE of a modified Mercalli intensity (MMI) level III and IV, respectively, in the next 50 y. The low hazard areas of Chiang Mai and Uttaradit provinces had a ground shaking level for a 2% and 10% POE in the next 50 y of around 0.16 and 0.08, respectively, with a POE of a MMI level III or IV of less than 20% each.

In this study, the seismicity rate changes that can represent an earthquake precursor were investigated along the Sagaing Fault Zone (SFZ), Central Myanmar, using the Z value technique. After statistical improvement of the existing seismicity data (the instrumental earthquake records) by removal of the foreshocks and aftershocks and man-made seismicity changes and standardization of the reported magnitude scales, 3574 earthquake events with a M w ≥ 4.2 reported during 1977–2015 were found to directly represent the seismotectonic activities of the SFZ. To find the characteristic parameters specifically suitable for the SFZ, seven known events of M w ≥ 6.0 earthquakes were recognized and used for retrospective tests. As a result, utilizing the conditions of 25 fixed earthquake events considered (N) and a 2-year time window (T w), a significantly high Z value was found to precede most of the M w ≥ 6.0 earthquakes. Therefore, to evaluate the prospective areas of upcoming earthquakes, these conditions (N = 25 and T w = 2) were applied with the most up-to-date seismicity data of 2010–2015. The results illustrate that the vicinity of Myitkyina and Naypyidaw (Z = 4.2–5.1) cities might be subject to strong or major earthquakes in the future.

Earthquake activities along the Sumatra-Andaman Subduction Zone (SASZ) were clarified using the derived frequency-magnitude distribution in terms of the (i) most probable maximum magnitudes, (ii) return periods and (iii) probabilities of earthquake occurrences. The northern segment of SASZ, along the western coast of Myanmar to southern Nicobar, was found to be capable of generating an earthquake of magnitude 6.1–6.4 Mw in the next 30–50 years, whilst the southern segment of offshore of the northwestern and western parts of Sumatra (defined as a high hazard region) had a short recurrence interval of 6-12 and 10-30 years for a 6.0 and 7.0 Mw magnitude earthquake, respectively, compared to the other regions. Throughout the area along the SASZ, there are 70– almost 100% probabilities of the earthquake with Mw up to 6.0 might be generated in the next 50 years whilst the northern segment had less than 50% chance of occurrence of a 7.0 Mw earthquake in the next 50 year. Although Rangoon was defined as the lowest hazard among the major city in the vicinity of SASZ, there is 90% chance of a 6.0 Mw earthquake in the next 50 years. Therefore, the effective mitigation plan of seismic hazard should be contributed.

In this study, the earthquake hazard was evaluated for all of 19 of the proposed or built dams along the Mekong River. All values representing a potential indication of hazardous earthquakes, such as the closest earthquake and seismogenic faults and including the seismic parameters required for a seismic safety evaluation, were clarified. The results will be useful in reviewing the safety of existing dams and for the design of suitable earthquake resistant specifications for any currently or future planned dam construction in this area. Seismotectonically, 14 of the 19 proposed Mekong River dams are located within an earthquake source zone. Most of faults are potentially still active, according to both seismicity and paleoseismological evidence. In addition, the maximum credible earthquakes were estimated to be in the range of 7–8 Mw for the closest fault zone of each dam. Previous isoseismal maps indicated a risk of shaking intensities of around scale III–IV (Modified Mercalli Intensity Scale) for the dams. According to the preliminary ranging of the International Commission on Large Dams, 9 of these 19 dams are classified as in an extreme hazard class and so need careful observation and monitoring of hazardous earthquakes. An effective mitigation plan should also be prepared for each operating dam.

The characteristics of tropical storm washover deposits laid down during the years 2007 to 2011 along the southern peninsular coast of the Gulf of Thailand (GOT) were described in relation to their different geomorphic conditions, including perched fan, washover terrace and sheetwash lineations preserved behind the beach zone within 100 m of the shoreline. As a result, washover terrace and sheetwash lineations were found where the beach configuration was uniform and promoted an unconfined flow. Non-uniform beach configurations that promoted a confined flow resulted in a perched fan deposit. Washover sediments were differentiated into two types based on sedimentary characteristics, including (i) a thick-bedded sand of multiple reverse grading layers and (ii) a medium-bedded sand of multiple normal grading layers. In the case of thick-bedded washover deposits, the internal sedimentary structures were characterized by the presence of sub-horizontal bedding, reverse grading, lamination, foreset bedding and wavy bedding, whereas, horizontal bedding, normal grading, and dunes were the dominant structures in the medium-bedded washover sand. Rip-up clasts were rare and recognized only in the washover deposits in the bottom unit, which reflects the condition when a mud supply was available. All washover successions were found in the landward inclined-bedding with a basal sharp contact. A high elevated beach ridge associated with a large swale at the backshore proved suitable for a thick-bedded washover type, whereas a small beach ridge with uniformly flat backshore topography promoted a medium-bedded washover sediment.

The frequency–magnitude distributions of earthquakes are used in this study to estimate the earthquake hazard parameters for individual earthquake source zones within the Mainland Southeast Asia. For this purpose, 13 earthquake source zones are newly defined based on the most recent geological, tectonic, and seismicity data. A homogeneous and complete seismicity database covering the period from 1964 to 2010 is prepared for this region and then used for the estimation of the constants, a and b, of the frequency–magnitude distributions. These constants are then applied to evaluate the most probable largest magnitude, the mean return period, and the probability of earthquake of different magnitudes in different time spans. The results clearly show that zones A, B, and E have the high probability for the earthquake occurrence comparing with the other seismic zones. All seismic source zones have 100 % probability that the earthquake with magnitude ≤6.0 generates in the next 25 years. For the Sagaing Fault Zone (zones C), the next Mw 7.2–7.5 earthquake may generate in this zone within the next two decades and should be aware of the prospective Mw 8.0 earthquake. Meanwhile, in Sumatra-Andaman Interplate (zone A), an earthquake with a magnitude of Mw 9.0 can possibly occur in every 50 years. Since an earthquake of magnitude Mw 9.0 was recorded in this region in 2004, there is a possibility of another Mw 9.0 earthquake within the next 50 years.

Seismic hazards in Thailand and adjacent areas were analyzed mainly on the basis of geological fault data. We identified 55 active fault zones using remote-sensing data on earthquake source parameters derived from both active fault data and earthquake catalogues. We selected strong ground-motion attenuation models by comparing the application of several candidate models with strong ground-motion data recorded in Thailand. Both deterministic (DSHA) and probabilistic (PSHA) approaches were used—DSHA for the design of critical construction and PSHA for the design of non-critical construction. We also applied two frequency-magnitude models in the PSHA approach: the exponential magnitude distribution model and the characteristic earthquake model. The seismic hazard results obtained using the deterministic and probabilistic approaches are not equivalent. The resulting DSHA map reveals extremely high seismic hazard levels in some areas of Thailand and in surrounding countries, while the PSHA map reveals a seismic hazard distribution similar to that of the DSHA but with lower seismic hazard levels. The areas of high seismic hazard include countries neighboring Thailand, such as Myanmar, Laos, Vietnam, and Indonesia (Sumatra Island), and areas within Thailand itself, primarily those areas in northern, western, and southern Thailand that are dominated by active fault zones.

In order to determine the prospective areas of the forthcoming earthquake sources, the [Formula: see text]-values of the frequency-magnitude earthquake distributions were analyzed spatially and mapped along the strike-slip fault system at the Thailand–Myanmar border. In order to constrain the relationship between the variation of [Formula: see text] and the following hazardous earthquake, the completeness of earthquake catalogue was manipulated into two datasets for (i) 1980–2000 and (ii) 1980–2005 and the [Formula: see text]-values mapped. Utilizing the suitable assumption of 30 fixed earthquake events, the following [Formula: see text] earthquakes illustrate a significant relation between their epicenter and the areas showing relatively low [Formula: see text]-values. By utilizing the most recent earthquake data (1980–2015), five areas exhibiting low [Formula: see text]-values (implying prospective earthquake sources) can be identified along the strike-slip fault system. Compared with earthquake activities evaluated previously along the strike-slip fault system, the data reveal that these five areas may potentially generate earthquakes up to 7.0[Formula: see text][Formula: see text] within the coming 50 years; the recurrence of the [Formula: see text]-5.0 earthquake is about 10 years and the probabilities of the [Formula: see text]-5.0 earthquake are about 40–95%, respectively. Since these prospective hazardous seismic zones are located close to cities, population centers and hydropower dams, an effective mitigation plan should be developed.

We conducted probabilistic seismic hazard analysis for Thailand and adjacent areas using a method proposed by Cornell (1968). We produced seismic hazard maps showing peak ground acceleration (PGA). Twenty-one seismic source zones covering all of Thailand and extend into adjacent areas were employed. The seismicity data used in this study was a merged data set covering 1963 - 2007 from several international earthquake catalogues and a single Thai catalogue. We selected the strong ground-motion attenuation model for this study by applying several existing attenuation models to recorded strong ground-motion data and choosing the model that best fit our data. Seismic hazard analysis was carried out for 2521 grid points on a 0.25¢X ¡_ 0.25¢X mesh within a rectangle defined by longitudes 92 - 106¢XE and latitudes 0¢X - 21¢XN. The resulting PGA maps for a 2% probability of exceedance for a 50-year time period suggest that ground motion of 0.3 to 0.4 g may occur in northern and western Thailand and from 0 to 0.2 g in other parts of Thailand. The seismic hazard analysis presented here is an important step toward an accurate evaluation of a seismic hazard potential in Thailand and adjacent areas. Further work is needed to refine the analysis. More observations of strong ground motion in the region are needed and further seismo-tectonic research should be encouraged.

Sets of beach ridge plains located as far as ten kilometres inland at the Chumphon estuary area, southern peninsular Thailand, provide evidence of an ancient sea-level change. Relict coastal landforms including former beach ridge plains, old lagoons, swales, and former tidal flats between beach ridges are found inland at elevations of 1-5 m above the present sea level. Ancient beach ridges here comprise three sets and all are inferred to have been deposited during the Holocene. The orientation of the inner beach ridge plains confirms their deposition by south to north longshore currents, whereas the middle and outer ridges were probably formed by north-to-south currents. Grain size analysis shows that all ancient beach ridge deposits are similar and are composed of fine- to medium-grained sand with high sphericity. Likewise, the compositions are similar, with quartz as a major component and feldspar and ferromagnesian minerals as minor components, reflecting the same sediment provenance. Marine fossils found in the former tidal deposit indicate intertidal and mangrove environments. Optical stimulating luminescence dating of three sets of beach ridge plains indicate that deposition occurred 8900-5600, 5900-2700, and 3800-1600 years ago for inner, middle, and outer beach ridge plains, respectively.

In this study, I investigated qualitatively the earthquake catalogue of the Thai Meteorological Department (TMD), Thailand, with respect to the seismicity patterns of Thailand. The readymade relationships between the different magnitude scales were derived to allow their convenient interconversion. Earthquake declustering was performed in order to screen the main shocks from the foreshocks and aftershocks, reducing the 1998–2009 records from ~48,900 to 2,620 main events. Man-made changes in the seismicity rate were carefully checked for, but only some minor changes were found and these were not related to any network improvements. In order to assess the limit of the earthquake detection in the catalogue the criterion of the magnitude of completeness (Mc) was employed, revealing a high efficiency of earthquake detection at a low Mc (3.0–3.5 Mw), especially for the inland active fault zone that dominates in Southeast Asia. Thus, the TMD's catalogue is one of the alternative catalogues for seismicity investigation of inland earthquakes. Meanwhile for the area surrounding the Sumatra Island and Northern Myanmar, the TMD's network is sufficient only for earthquakes with a Mw> 5.4–6.0 Mw. Thus, some additional seismic recording stations are needed in the Southern and Northern parts of Thailand.

In this study, an open source MATLAB software, called CU-PSHA, is developed in order to analyze probabilistic earthquake hazards. This software aims to provide a user friendly and flexible tool for evaluating reliable earthquake hazard estimates. With the CU-PSHA, the probability of distances between the earthquake sources and the study site can be estimated. Two choices for the estimation of earthquake frequency–magnitude distribution, the exponential magnitude distribution and the characteristic earthquake models, are provided. Some strong ground–motion attenuation models are available for both shallow crustal and subduction zone earthquakes. The probability of exceedance of any individual given ground shaking value can be obtained, allowing the display of a seismic hazard curve. In addition with the supplementary MATLAB scripts, this CU-PSHA software can be employed in general seismic hazard mapping, for both ground shaking level and probability of occurrence, in any specific given time span.

In this study, the geospatial frequency–magnitude distribution (FMD) b-value images of the prospect sources of upcoming earthquakes were investigated along the Indonesian Sunda Margin (ISM) that strikes parallel to and near the Indonesian Island chain. After enhancing the completeness and stability of the earthquake catalogue, the seismicity data were separated according to their seismotectonic setting into shallow crustal and Intraslab earthquakes. In order to verify the spatial relationship between the b-values and the occurrence of subsequent major earthquakes, the complete shallow crustal seismicity dataset (1980–2005) was truncated into the 1980–2000 sub-dataset. Utilizing the suitable assumption of fixed-number of earthquakes, retrospective tests of both the complete and truncated datasets supported that areas of comparatively low b-values could reasonably be expected to predict likely hypocenters of future earthquakes. As a result, the present-day distributions of b-values derived from the complete (1980–2005) shallow crustal and Intraslab seismicity datasets revealed eight and six earthquake-prone areas, respectively, along the ISM. Since most of these high risk areas proposed here are quite close to the major cities of Indonesia, attention should be paid and mitigation plans should be developed for both seismic and tsunami hazards.

We applied remote sensing and aerial photographic techniques to a study of the Mae Hong Son Fault (MHSF), located in the Mae Hong Son region, northern Thailand. Several fault lines are recognized in the region, trending mainly NE–SW, NW–SE, and N–S. The main morphotectonic landforms associated with the MHSF are fault scarps, offset streams, linear valleys, triangular facets, offset ridge crests, hot springs, and linear mountain fronts. A trench, a quarry, and a road cut in Caenozoic strata were used to analyze fault geometries in the area. We identified eight paleoearthquake events from trenching, quarry, and road-cut data, and from optically stimulated luminescence (OSL) and thermoluminescence (TL) dating. The OSL and TL ages of the events are: (1) 78,000 yr BP; (2) 68,000 yr BP; (3) 58,000 yr BP; (4) 48,000 yr BP; (5) 38,000 yr BP; (6) 28,000 yr BP; (7) 18,000 yr BP; and (8) 8,000 yr BP. The recurrence interval of seismic events on the MHSF appears to be ca. 10,000 years, and the slip rate was estimated as ca. 0.03–0.13 mm/yr. There is a low possibility of a large earthquake on the MHSF in the near future.

In this study, the b-values of frequency-magnitude earthquake distributions were mapped spatially along the sagaing fault zone (SFZ), central Myanmar. Three sub-datasets of the complete earthquake catalogue were tested in order to ensure the applied assumption. Using the present-day dataset (1980–2010), two areas of low b-values, which are prospective potential earthquake sources, were identified at the Naypyidaw-Mandalay and southwestern part of Myitkyina in the central and northern part of the SFZ, respectively. To assess the possible earthquake magnitudes, the b-values were mapped in the cross-section dimension along the SFZ. The obtained areas of low b-values, referred to as the fault asperity regions, conformed to those illustrated in the surface map. The asperity's sizes, examined from specific low b-values of ≤ 0.65 and ≤ 0.060 were quantitatively estimated and empirically converted to the potential earthquake magnitudes. This analysis revealed three prospective areas surrounding the Myitkyina regions capable of generating earthquakes in the future with a possible magnitude of 8.6 Richter. The contribution of effective mitigation plans are, therefore, urgently needed for Myanmar and the adjacent area.

The potential areas of upcoming earthquakes were investigated along the Northern segment of the Sumatra–Andaman Subduction Zone according to the b-value of the frequency-magnitude distribution. After enhancing the completeness of the earthquake catalogue, two datasets, those recorded during (i) 1980–1994 and (ii) 1980–2003, were tested in order to verify the effective correlation between precursory b-values and the location of subsequent earthquakes. The results confirmed that areas with low b-values agreed well with the locations of the subsequent earthquakes in that region. Accordingly, the present-day dataset from 1980–2010 was carefully evaluated to determine the b-values across the region. Within this spatial investigation, three areas of low b-values and so potential hazards were found. These consisted of the (i) West coast of Myanmar, and (ii) North and (iii) South of the Nicobar Islands. From 2010–2012, a major earthquake with magnitude 7.5 mbwas recorded as being generated in the region South of the Nicobar Islands. Thus, attention should be paid to the remaining two until now quiescent areas, and mitigation plans should be raised for both seismic and tsunami hazards.

In this study, the seismic hazards of Myanmar are analyzed based on both deterministic and probabilistic scenarios. The area of the Sumatra–Andaman Subduction Zone is newly defined and the lines of faults proposed previously are grouped into nine earthquake sources that might affect the Myanmar region. The earthquake parameters required for the seismic hazard analysis (SHA) were determined from seismicity data including paleoseismological information. Using previously determined suitable attenuation models, SHA maps were developed. For the deterministic SHA, the earthquake hazard in Myanmar varies between 0.1 g in the Eastern part up to 0.45 g along the Western part (Arakan Yoma Thrust Range). Moreover, probabilistic SHA revealed that for a 2% probability of exceedance in 50 and 100 years, the levels of ground shaking along the remote area of the Arakan Yoma Thrust Range are 0.35 and 0.45 g, respectively. Meanwhile, the main cities of Myanmar located nearby the Sagaing Fault Zone, such as Mandalay, Yangon, and Naypyidaw, may be subjected to peak horizontal ground acceleration levels of around 0.25 g.

A large number of earthquakes have been recorded by instrument in the past along the Thailand-Laos-Myanmar border region. However, the locations of most of these earthquakes do not coincide with the location of morphological features which indicate seismogenic faults. Thus, a statistical evaluation of the earthquake record is focused upon in this earthquake hazard study. The spatial distributions of the a- and b-values from the frequency-magnitude distribution relationship were investigated from the complete earthquake catalogue.

A probabilistic seismic hazard analysis (PSHA) for Thailand was performed and compared to those of previous works. This PSHA was based upon (1) the most up-to-date paleoseismological data (slip rates), (2) the seismic source zones, (3) the seismicity parameters (a and b values), and (4) the strong ground-motion attenuation models suggested as being suitable models for Thailand. For the PSHA mapping, both the ground shaking and probability of exceedance (POE) were analyzed and mapped using various methods of presentation. In addition, site-specific PSHAs were demonstrated for ten major provinces within Thailand. For instance, a 2 and 10 % POE in the next 50 years of a 0.1–0.4 g and 0.1–0.2 g ground shaking, respectively, was found for western Thailand, defining this area as the most earthquake-prone region evaluated in Thailand. In a comparison between the ten selected specific provinces within Thailand, the Kanchanaburi and Tak provinces had comparatively high seismic hazards, and therefore, effective mitigation plans for these areas should be made. Although Bangkok was defined as being within a low seismic hazard in this PSHA, a further study of seismic wave amplification due to the soft soil beneath Bangkok is required.

The 2004 Sumatra and 2011 Tohoku earthquakes highlighted the need for a more accurate understanding of earthquake characteristics in both regions. In this study, both the a and b values of the frequency-magnitude distribution (FMD) and the fractal dimension (D C ) were investigated simultaneously from 13 seismic source zones recognized in mainland Southeast Asia (MLSEA). By using the completeness earthquake dataset, the calculated values of b and D C were found to imply variations in seismotectonic stress. The relationships of D C -b and D C -(a/b) were investigated to categorize the level of earthquake hazards of individual seismic source zones, where the calibration curves illustrate a negative correlation between the D C and b values (D c = 2.80 - 1.22b) and a positive correlation between the D C and a/b ratios (D c = 0.27(a/b) - 0.01) with similar regression coefficients (R2 = 0.65 to 0.68) for both regressions. According to the obtained relationships, the Hsenwi-Nanting and Red River fault zones revealed low-stress accumulations. Conversely, the Sumatra-Andaman interplate and intraslab, the Andaman Basin, and the Sumatra fault zone were defined as high-tectonic stress regions that may pose risks of generating large earthquakes in the future.