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The Thai Meteorological Department (TMD) seismic network began development in 2008. Currently there are a total of 71 seismic stations consisting of 26 borehole stations and 45 surface stations currently installed. The three-component data from the TMD seismic network have been widely used in a number of seismological studies. In a recent analysis, we have found that sensor orientation as reported in the site metadata is sometimes significantly incorrect, especially for borehole stations. In this study, we analyze P-wave polarization data from regional and teleseismic earthquakes recorded in the network to estimate the true instrument orientation relative to geographic north and compare that to station metadata. Of the 45 surface stations, we found that ~78% are well oriented (i.e. aligned within 0°-15° of true north). However 10 sites have sensors misoriented by more than 15° , and some stations had a temporal change in sensor orientation during an upgrade to the seismic system with replacement of the sensor. We also evaluated sensor orientations for 26 TMD borehole seismic stations, from 2018 to 2022. For many of the borehole stations, the actual sensor orientation differs significantly from the TMD metadata, especially at short-period stations. Many of those stations have sensor misorientations approaching 180°, due to errors in the ambient noise analysis calibration techniques used during installation. We have also investigated how this sensor misorientation affects previous seismic studies, such as regional moment tensor inversion of earthquakes sources and receiver function stacking. We have found that the large deviations in sensor orientations can result in erroneous results and/or large measurement errors. A cause of the orientation error for borehole sites could be a combination of strong background surface ambient seismic noise coupled with an incorrect reference instrument response.

On 5 May 2014, a Mw 6.2 strike-slip earthquake occurred in the Mae Lao region of Chiang Rai province in Thailand. This earthquake took place in a region of known faults and caused substantial damage and injuries, although the region had been previously identified as having a relatively low earthquake hazard. Detailed field reconnaissance and deployment of a dense, temporary, network of broadband seismometers allowed details of the damage and its relationship to seismicity to be analyzed. The aftershock sequence associated with this main shock occurs on two well-defined trends, reflecting the two potential fault planes in earthquake mechanisms for the main shock and the majority of the aftershocks. The damage area was relatively large for an event of this magnitude, but building damage was largely limited to the primary rupture region, while liquefaction and other ground failure is spatially associated with the rupture area and along regional rivers. Stress modeling, combined with the time-series and pattern of aftershock activity, lead us to propose that slip near the northern termination of the main shock rupture continued slightly onto a conjugate fault, helping to trigger the distinct pattern of two discrete, conjugate trends of aftershock activity that mirror the kinematics of the main shock fault mechanism

Summary Reanalysis of seismicity from the Thai Meteorological Department seismic network and 6 temporary seismic stations operated by Kasetsart University reveals a possible unknown active fault near the city of Chiang Mai in the northern Thailand. There are 50 small earthquakes occurred in San Sai districts during November 2018 to April 2019 while only 9 earthquakes were officially reported. There is a 3.2 ML occurring in San Sai district on 22 January 2019 which can be felt in many locations nearly the epicenter.

2-D seismic data from the top and the western slope of Mergui Ridge in water depths between 300 and 2200 m off the Thai west coast have been investigated in order to identify mass transport deposits (MTDs) and evaluate the tsunamigenic potential of submarine landslides in this outer shelf area. Based on our newly collected data, 17 mass transport deposits have been identified. Minimum volumes of individual MTDs range between 0.3 km3 and 14 km3. Landslide deposits have been identified in three different settings: (i) stacked MTDs within disturbed and faulted basin sediments at the transition of the East Andaman Basin to the Mergui Ridge; (ii) MTDs within a pile of drift sediments at the basin-ridge transition; and (iii) MTDs near the edge of/on top of Mergui Ridge in relatively shallow water depths (< 1000 m). Our data indicate that the Mergui Ridge slope area seems to have been generally unstable with repeated occurrence of slide events. We find that the most likely causes for slope instabilities may be the presence of unstable drift sediments, excess pore pressure, and active tectonics. Most MTDs are located in large water depths (> 1000 m) and/or comprise small volumes suggesting a small tsunami potential. Moreover, the recurrence rates of failure events seem to be low. Some MTDs with tsunami potential, however, have been identified on top of Mergui Ridge. Mass-wasting events that may occur in the future at similar locations may trigger tsunamis if they comprise sufficient volumes. Landslide tsunamis, emerging from slope failures in the working area and affecting western Thailand coastal areas therefore cannot be excluded, though the probability is very small compared to the probability of earthquake-triggered tsunamis, arising from the Sunda Trench.

The goal of this study is to identify Thai students ' prior knowledge about particle motion when P-waves arrive. This existing idea significantly influences what and how students learn in the classroom. The data were collected via conceptual open-ended questions designed by the researchers and through explanatory follow-up interviews. Participants (n = 171) were freshmen in science, engineering, agricultural sciences, and medicine fields enrolled in a university in Thailand. The major categories of Thai students ' prior knowledge about particle motion at P-wave arrival are (1) the belief that particles spread in all directions, like water waves, when P-waves arrive, (2) the belief that particles move forward with a sine wave motion, and that these particles travel with the propagating wave energy to the P-wave 's final destination, (3) the belief that particles vertically move back and forth at P- wave arrival. These beliefs are the alternative conception held by more than three-quarter of our study popul...

Sequence mapping of industry seismic lines and their correlation to exposed stratigraphic formations enable a description of the evolution of the nonmarine Salar de Atacama Basin. This major tectonic basin, located in the present-day forearc of the northern Chilean Andes, was first defined topographically by late Cretaceous inversion of the Jurassic–early Cretaceous extensional Tarapaca backarc Basin. Inversion led to both the uplift of the Cordillera de Domeyko and subsidence of the Salar de Atacama Basin along its eastern flank. The basin evolved from a continental backarc in the Cretaceous and Paleogene to a forearc tectonic setting during the Neogene. The principal causes of basin-scale tectonic subsidence include late Cretaceous and earliest Paleocene shortening and Oligocene–early Miocene localized extension. The basin was not completely filled by late Cretaceous (Purilactis Group, sequence G) and Paleocene (sequence H) strata, and its empty space persisted through the Cenozoic. Eocene deformation caused long-wavelength rotation of a deeply weathered surface, generating an erosional unconformity across which coarse clastic strata accumulated (sequence J). Oligocene–early Miocene normal faulting, perhaps in a transtensional environment, repositioned the western basin margin and localized hangingwall subsidence, leading to the accumulation of thousands of meters of evaporitic strata (sequence K, Paciencia Group). By the close of the early Miocene, shortening resumed, first uplifting the intrabasinal Cordillera de la Sal and later generating Pliocene blind reverse faults within the topographically lowest part of the basin. Unequal deposition and tilting across the nascent Cordillera de la Sal induced diapirism of the Paciencia Group halite. In combination, inherited accommodation space and new tectonic subsidence, plus local salt-withdrawal subsidence, shaped the distribution of Upper Miocene–Recent ignimbrites, evaporites, and clastics (sequence M and Vilama Formation).

SUMMARY In the summer of 1998, a series of multichannel, deep seismic reflection tests were conducted in central Tibet around 89 ◦ E as part of the third phase of Project INDEPTH, a multidisciplinary study of the structure of the core of the Tibetan Plateau. Short seismic reflection sections from four locations spanning the Jurassic Banggong‐Nujiang Suture show several features: thin (

The 2004 tsunami caused by the great Sumatra earthquake devastated a large amount of the local communities along the coastline of the Andaman Sea in the southern Thailand. Since then most communities have been gradually recovered from this disaster through various restoration processes. This chapter presents a case study of the post-disaster recovery processes for two small local villages: the Nua and the Hat Sai Khao villages in Suk Samran district, Ranong province, compared with those of the government organizations, the Kasetsart University’s Andaman Coastal Research Station for Development that was also hit hard by this tragic incident. The recovery process of these two small villages can be used as proxies for many small local communities in the southern Thailand about how they have adapted themselves to restore their communities back to their normal stages and eventually to have a sustainable immunity to this natural hazard. The tsunami impacts and detailed restoration and reconstruction processes of these two villages are discussed from the day the disaster occurred until recently. It can be concluded that for small local communities, the external supports, either from central government or the private sectors, are as important as the wills of the residents to support themselves. Without the external help, it is extremely difficult for such small local communities in Thailand to get back on their feet within a short time. In addition, the large amount of the funding support must be distributed to the affected communities within a short time in order to provide effective recovery processes. It can be seen for this specific case study that the continuation of the long term support to the affected communities and the participation of the victims in the restoration and reconstruction processes are also very important in order to help the victims restore their lives and to avoid any social problems that may occur in the affected communities in the future.

Unexpected devastation of the Thai communities along the Andaman coast lines by the 2004 Sumatra tsunami have changed the Thai perception on the earthquake and tsunami disaster forever. This paper tells about the economic and social impacts of the 2004 tsunami that affected the Thai society and the lessons learned from these tragic incident. Since then, a large amount of money and effort have been invested in the tsunami research and development, earthquake and tsunami monitoring and warning systems and a large number of educational outreach to young generations. The proper tsunami and earthquake mitigations of the central government collaborated with local governments integrated with the people’s understandings of the nature of the earthquake and tsunami help increase the readiness of the Thai community for such disaster more than ever. Still, many issues remain to be resolved such as a lack of proper maintenance of the critical facilities for the earthquake and tsunami mitigation and inadequate research and development in earthquake and tsunami sciences in Thailand. It is very difficult to maintain the level of the awareness of the people about the great danger of the earthquake and tsunami and it is also a big challenge to increase the ability of the Thai society to have better critical scientific thinking about the natural disaster.

[1] Since 90 Ma, the nonmarine Salar de Atacama Basin has been the largest, deepest, and most persistent sedimentary basin of northern Chile. Integration of 200 km of two-dimensional seismic reflection data with surface geological data clarifies Oligocene and Neogene evolution of the northern part of the basin. A normal fault with 6 ± 1 km of vertical separation controlled the western boundary of the basin during the accumulation of the Oligocene–lower Miocene Paciencia Group. The combination of this structure, a similar one in the Calama Basin, and regional structural data suggests that localized extension played an important role within a tectonic environment dominated by margin-perpendicular compression and margin-parallel strike-slip deformation. Seismic data substantiate the surface interpretation that much of the Cordillera de la Sal ridge resulted from diapiric flow of the Paciencia Group. Diapiric flow initiated during the late early Miocene or middle Miocene, associated with a deep reverse fault.

Summary In the summer of 1998, project INDEPTH recorded a 400 km long NNW–SSE wide-angle seismic profile in central Tibet, from the Lhasa terrane across the Banggong-Nujiang suture (BNS) at about 89.5°E and into the Qiangtang terrane. Analysis of the P-wave data reveals that (1) the crustal thickness is 65 ± 5 km beneath the line; (2) there is no 20 km step in the Moho in the vicinity of the BNS, as has been suggested to exist along-strike to the east based on prior fan profiling; (3) a thick high-velocity lower crustal layer is evident along the length of the profile (20–35 km thick, 6.5–7.3 km s−1); and (4) in contrast to the southern Lhasa terrane, there is no obvious evidence of a mid-crustal low-velocity layer in the P-wave data, although the data do not negate the possibility of such a layer of modest proportions. Combining the results from the INDEPTH III wide-angle profile with other seismic results allows a cross-section of Moho depths to be constructed across Tibet. This cross-section shows that crustal thickness tends to decrease from south to north, with values of 70–80 km south of the middle of the Lhasa terrane, 60–70 km in the northern part of the Lhasa terrane and the Qiangtang terrane, and less than 60 km in the Qaidam basin. The overall northward thinning of the crust evident in the combined seismic observations, coupled with the essentially uniform surface elevation of the plateau south of the Qaidam basin, is supportive of the inference that northern Tibet until the Qaidam basin is underlain by somewhat thinner crust, which is isostatically supported by relatively low-density, hot upper mantle with respect to southern Tibet.

Aerial photographic maps and landsat image interpretations suggest the major fault segments of the Three PagodaFault (TPF) Zone and Sri Swat Fault (SSF) Zone are oriented parallel or sub-parallel in the same NW-SE directions. The KwaeNoi River is running along the TPF in the south whereas the Kwae Yai River is running along the SSF in the north. Thesoutheastern continuation of both faults is obscured by thick Cenozoic sediments. Hence, surface lineaments cannot betraced with confidence. However, based on some interpretations of the airborne magnetic survey data, the trace of such faultsare designated to run through the western part of Bangkok and the northern end of the Gulf of Thailand. Paleo-earthquakesand the presence of hot springs along the fault zones indicate that they are tectonically active. The changes of both physicaland chemical properties of the water from Hin Dart Hot Spring and those of the surface water from a shallow well at Ban KhaoLao during the Great Sumatra–Andaman Earthquake on 26th of December 2004 clearly indicated that the southeastern continuation of the TPF is at least as far south as Pak Tho District, Ratburi. Our new evidence of the alignment of the high heatflow in the upper part of the Gulf of Thailand verified that the TPF also extend into the Gulf via Samut Songkhram Province.Studies of the seismic data from two survey lines along the Western part of the upper Gulf of Thailand acquired by BritoilPlc. in 1986, namely Line A which is approximately 60 km long, starting from Bang Khen passing through Bang Khae andending in Samut Songkhram and Line B is approximately 30 km long starting from Samut Sakon ending in Samut Song Khramsuggest that all the faults or fractures along these seismic profiles are covered by sediments of approximately 230 m thickwhich explain that the fault underneath these seismic lines is quite old and may not be active. The absent of sign or trace ofthe TPF Path to the west suggested that there is no segment of such fault along these seismic lines.

Seismic activities in Kanchanaburi Province of the western Thailand have been a major concern among the Thai publicdue to the fear that a big earthquake caused by the Three Pagodas Fault Zones (TPFZ) and the Sri Sawat Fault Zone (SSFZ), oneof the largest active fault zones in Thailand, could damage the large dams and generate a great disaster to the communities.Four hundred and thirty seven earthquakes that occurred in Kanchanaburi since 1983 have been analyzed for the time andlocation distributions along with the frequency magnitude relationship. There are no clear correlations between the epicentersof these earthquakes and the known locations of the active faults in the region. The seismic catalog used in this study iscomplete for Mw=3.0 for Kanchanaburi region. The analysis of G-R relationship yields a-value of 5.15 and b-value of 0.86. Adeterministic seismic hazard analysis of the TPFZ and SSFZ suggests that the characteristic earthquakes magnitudes of theTPFZ and the SSFZ are 7.3 and 7.0, respectively, with a maximum PGA of 0.31 and 0.28 g at the faults lines for the earthquakeoccurring at 15 km depth.