This document summarizes a macroseismic survey of the 2014 M6.3 Mae Lao Fault earthquake in northern Thailand. A total of 331 data points were collected through field surveys, interviews, and media reports to create an isoseismal map with 8 intensity levels. The maximum Modified Mercalli Intensity was IX, covering 163 square km. The felt area encompassed 10 provinces over 147,900 square km. The survey characterized ground shaking effects to understand damage patterns from the largest earthquake to hit Thailand since instrumental records began.

1. Macroseismic Survey of the M6.3, 2014 Mae Lao Fault Earthquake
Aomboon Naksawee and Anchalee Laddakul
Panya Consultants Co. Ltd., Bangkok, Thailand
E-mail: aomboon_n@panyaconsult.co.th, anchalee_l@panyaconsult.co.th
Abstract
Macroseismic survey was performed after the M6.3 earthquake on 5th
May 2014 on Mae Lao fault in northern
Thailand. Isoseismal map that developed gave total 8 levels of Modified Mercalli Intensity. The maximum MMI is IX.
The affected area covered total 10 provinces about 147,900 square kilometers of Chiang Rai, Chiang Mai, Nan,
Uttaradit, Phrae, Maehongson, Lamphun, Lampang, Tak and Phayao province. This earthquake produced shaking
intensity that a specially designed structure can shifted off its foundations, partial collapse and ground cracked.
Key word: macroseismic, isoseismal map, Modified Mercalli Intensity, Mae Lao Earthquake.
INTRODUCTION
Thailand has no large earthquake in the past,
however at 18:08 local time on the 5th of May 2014,
the largest earthquake in Thailand since her first
instrumental recorded has occurred, which an epicenter
at latitude 19.75 N and longitude 99.69 E of Ban Dong
Mada, Mae Lao District, Chiang Rai Province. The
magnitude was reported by Thai Meteorological
Department to be 6.3 ML and 7 kilometer depth. The
earthquake affected habitats, roads, temples, schools,
official places and other buildings. The felt area
covered total 7 provinces, 7 districts, 50 sub-district
and 609 villages of Northern part of Thailand. This
earthquake caused two casualties which is the first
dead toll directly effect by earthquake. This large
earthquake is an important event for Thai peoples, its
rises the awareness and becomes the best case study for
seismologist into development.
GEOLOGY AND SEISMOTECTONIC
SETTING OF THE STUDY AREA
The study area is located in the northern part
of Thailand, covering Chiang Rai, Phayao, Chiang
Mai, Mae Hong Son, Nan, Lampang, Lamphun and
Phrae Provinces. Geologic map scale of 1:500,000
(DMR, 2007) shows high mountain ranges in N – S
and NE – SW direction. The rock units in the area
consist of Precambrian which included high grade
metamorphic rocks (orthogneiss, paragneiss, schist,
calc-silicate and marble), Lower Paleozoic which
included Cambrian to Devonian, Upper Paleozoic
which included Carboniferous to Permian, Mesozoic
which included Triassic to Cretaceous, Cenozoic which
included Tertiary to Quaternary and finally, Igneous
rock which included intrusive and extrusive rock
,Figure 1.
Fig.1 Geology around study area show classified
rocks unit (modified DMR, 2007)
Tectonic setting of Thailand is a consequence
of the interaction between South China block in the
northeast, Eurasian plate in the north, Philippine Sea
plate in the east, Indian plate and Australian plate in the
west and southwest respectively. The study area locates
in the northern part of the Sundaland block, as shown
in Figure 2.

2. Fig.2 Location of Sundaland block shows
topography and main active faults in South East Asia
(Metcalfe, 2011)
The areas located in the Northern region
which is 1 of the 3 of high seismicity zone of Thailand
beside the Western region and Southern peninsular
region. Thailand consists of 14 active fault zones
(DMR, 2012), in which the study area located on
Phayao fault zones (Figure 4). The total length of this
fault is approximately around 70 kilometer. The
direction is NE - SW trending and left – lateral strike
slip fault. This fault can generate a maximum
earthquake of Mw 5.5-7.0 with a recurrent interval of
5,300 years (DMR, 2009). Phayao fault zones can
divided further into 2 segments: the southern segments
and northern segments which named the Mae Lao
fault segment and is believed to be the source of this
earthquake event.
Fig.4 Active fault map in Thailand (DMR, 2012)
INTENSITY SCALES
Intensity is a qualitative measure of the
strength of ground shaking at a particular site. Seismic
intensity is based on direct effects of the shock, such as
on hanging objects, buildings, topography, human
being etc. It is called Macroseismic effects. The
intensity varies with the position of the observation
point. It is greatest within the epicenter area, and from
there it usually decreases in all directions. Isoseismal
map is used to shown lines of felt seismic intensity and
characterize the severity of felt earthquake. In this
study use to modified Mercalli 12-value scales which
uses Roman numerals from I to XII to rank relative
levels of destruction, ground motion, and impact on
humans.
METHODOLOGY
In an exhaustive archival study, 331 original data
of the earthquake were compiled from: newspaper: ASTV
Manager online (2014, May 7), Matichon Online (2014,
May 7), TMD website (http://www.seismology.tmd.go.th/),
actual field survey and phone interview. The area covered
Chiang Rai, Chiang Mai, Nan, Uttaradit, Phrae,
Maehongson, Lamphun, Lampang, Tak and Phayao. All
together total 8 data were download from Thai
Methodological Department (TMD) website, total 50 data
from newspapers, total 28 data from field investigation and
245 data by phone interview , as shown in Table 1 .
Overall data were obtained at 331 locations as shown in
Figure 6.
The geographic coordinates of the survey points
from a handheld GPS unit and Google Map from actual
field survey data will be used. Where the highest intensity
level obtained for data from phone interview, based on
the questionnaire (Harnpattanapanich, T., 2006), that
each question that specified of earthquake effect based
on some specific indicators, of the whole district was
assigned to the centroid of the district. For example,
maximum MMI value of IX was assigned to Mae Lao
district, Chiang Rai province. (UTM: 575872, 2187021)
based on record affected data that described: damage
considerable in specially designed structure such as
buildings shifted off foundations or partial collapse and
ground cracked such as shown in Figure 7.
The method and procedure used in this study
is summarized in the following step:
1.Complied 331 original data of the
earthquake intensity from newspaper, actual field
survey, phone interview (Table 1) and interpreted
original data to modified Mercalli intensity (MMI)
values, followed the scheme of Brazee (1979)
2. Assigned a MMI values for average data for
each district
3. Total 64 MMI data points were obtained.
The results are summarized by in Table 2
3. All data was calculated by kriging
interpolation method using a commercial graphing
program Suffer v.10

3. 4. However, information from the program is
subject to mathematic limitation, thus required some
adjustment by human to conform to the actual field
data.
Table 1 Amount of data collected.
No. Source of data Amount of data collected
1 newspaper 50
2
TMD website
(http://www.seismology.tmd.go.th/)
8
3 actual field survey 28
4 phone interview 245
331Summary of all data
Fig.6 331 original macroseismic survey sites of the
M6.3, 2014 Mae Lao fault Earthquake from
newspaper, TMD website, actual field survey
and phone interview.
Table 2 Parameters of the macroseismic survey sites of
the M6.3, 2014 Mae Lao Fault Earthquake.
No. Location Amount MMI
1 Mae Lao, Chiang Rai 29 IX
2 Mueang, Chiang Rai 13 VII
3 Thoeng, Chiang Rai 18 IV
4 Khun Tan, Chiang Rai 7 III
5 Chiang Khong, Chiang Rai 25 IV
6 Chiang Saen, Chiang Rai 4 IV
7 Phan, Chiang Rai 10 VIII
8 Mae Suai, Chiang Rai 2 VIII
9 Mae Chan, Chiang Rai 1 VI
10 Wiang Pa Pao, Chiang Rai 1 VI
11 Chiang Dao, Chiang Rai 46 IV
12 Mae Taeng, Chiang Mai 4 IV
13 Mae Rim, Chiang Mai 4 IV
14 Mae Wang, Chiang Mai 3 III
15 Mae Ai, Chiang Mai 3 IV
16 Chai Prakan, Chiang Mai 3 V
17 Doi Saket, Chiang Mai 3 IV
18 Doi Lo, Chiang Mai 3 V
19 Mae On, Chiang Mai 3 III
20 Wiang Haeng, Chiang Mai 3 IV
21 Mae Chaem, Chiang Mai 3 IV
22 Omkoi, Chiang Mai 3 II
23 Fang, Chiang Mai 1 III
24 Mueang, Chiang Mai 2 V
25 Phrao, Chiang Mai 1 V
26 San Sai, Chiang Mai 1 VI
27 Chiang Klang, Nan 22 II
28 Tha Wang Pha, Nan 3 III
29 Wiang Sa, Nan 3 IV
30 Mae Charim, Nan 3 III
31 Na Muean, Nan 3 I
32 Na Noi, Nan 4 III
33 Santi Suk, Nan 4 III
34 Phu Phiang, Nan 1 V
35 Mueang Nan, Nan 3 IV
36 Pua, Nan 1 IV
37 Tha Pla, Uttaradit 3 I
38 Lablae, Uttaradit 1 I
39 Mueang, Uttaradit 3 IV
40 Nam Pat, Uttaradit 1 IV
41 Den Chai, Phrae 3 I
42 Song, Phrae 8 IV
43 Long, Phrae 25 II
44 Mueang, Phrae 9 II
45 Wang Chin, Phrae 1 II
46 Mueang, Mae Hong Son 4 III
47 Pai, Mae Hong Son 4 IV
48 Pang Mapha, Mae Hong Son 1 IV
49 Khun Yuam, Mae Hong Son 2 III
50 Mae La Noi, Mae Hong Son 2 III
51 Mae Sariang, Mae Hong Son 1 II
52 Sop Moei, Mae Hong Son 2 IV
53 Ban Hong, Lamphun 3 III
54 Mae Phrik, Lamphun 2 III
55 Mae Sot, Tak 1 I
56 Mueang, Tak 1 I
57 Wang Chao, Tak 1 I
58 Ban Tak, Tak 1 I
59 Chun, Phayao 2 VII
60 Chiang Kham, Phayao 2 VII
61 Mueang, Phayao 1 VI
62 Mae Chai, Phayao 2 VIII
63 Phu Sang, Phayao 1 VII
64 Pong, Phayao 1 VII
Fig.7 Damage that described in MMI value of IX
assigned to Mae Lao district, Chiang Rai
province (UTM: 575872, 2187021).
RESULT

4. The isoseismal map from the M6.3, 2014 Mae
Lao fault Earthquake is shown by isoseismal lines at 8
levels that is: IX, VIII, VII, VI, V, IV, III, and II
respectively.
The felt area covered total 10 provinces about
147,900 square kilometers of Chiang Rai, Chiang Mai,
Nan, Uttaradit, Phrae, Maehongson, Lamphun,
Lampang, Tak and Phayao province.
The maximum intensity level IX is covered in
some part of Mae Lao and Phan district, Chiang Rai
province. The total area of this intensity level is
approximately 163 square kilometer.
The intensity level VIII that covered in some
part of Chiang Rai and Phayao province. The total area
of this level is approximately 1,642 square kilometer.
The intensity level VII which is covered in some part
of Chiang Rai, Phayao and Lampang province. The
total area of this intensity level is approximately 5,607
square kilometer. The intensity level VI covered total 4
provinces. The area covered some part of Chiang Rai,
Chiang Mai, Phayao and Lampang province. The total
area of this level is approximately 10,685 square
kilometer. The intensity level V covered total 6
provinces. The affected area covered most area of
Chiang Rai and Chiang Mai province including some
part of Phayao, Nan, Lampang and Phare province. The
total area is approximately 18,612 square kilometer.
The intensity level IV that covered total 8
provinces, is covered most areas of Chiang Rai and
Chiang Mai province including some part of Phayao,
Mae Hong Son, Nan, Lampang, Phare and Lamphun
province. The total area is approximately 36,366 square
kilometer. The intensity level III covered total 9
provinces is covered most areas of Chiang Rai and
Chiang Mai province including some part of Phayao,
Mae Hong Son, Nan, Lampang, Phare, Lamphun and
Tak province. The total area of this intensity is
approximately 78,902 square kilometer. The
intensity level II covered across total 10 provinces such
as Chiang Rai, Chiang Mai, Nan, Lamphang,
Lamphun, Phare, Mae Hong Son, Uttaradit, Tak and
Sukhothai province. Because data cannot be collected
from neighboring countries and the information at this
level is too low, so that the isoseismal lines for this
level cannot be closed properly.
Fig.8 Isoseismal map of the M6.3, 2014 Mae Lao
Fault Earthquake
ACKNOWLEDGEMENTS
The authors would like to thanks all survey
participants and community officials for the interview
conducted. Thank also going to Khun Anuthep
Chaovanalikit, Executive Director of Panya Consultants
Co., Ltd. for supporting provided for time and data for
this work and to Dr. Thanu Harnpattanapanich, Advisor of
Panya Consultants Co., Ltd. for helpful comments,
suggestions and improving the manuscript and Mr.
Kaisorn Sarapakdee, Mr. Putpong Supawong, Geologist
of Panya Consultants Co., Ltd. and 2 student trainees for
helpful making macroseismic interviews (phone
interview). The data used is part of the earthquake
database, of Geotechnical Engineering division, Panya
Consultants Co., Ltd.
REFERENCES
Brazee, R. J. (1979). Reevaluation of Modified Mercalli
intensity scale for earthquakes using distance as
determinant. Bulletin of the Seismological
Society of America 69, 911–924.
Bunopas, S. (1981). Paleogeographic history of western
Thailand and adjacent parts of south–east Asia: a
plate tectonics interpretation. Doctoral
dissertation, Victoria University of Wellington,
New Zealand.
Chaodumrong, P. (1992). Stratigraphy, Sedimentology
and Tectonic Setting of the lamphang group,
Central North Thailand: University of
Tasmania, Ph.D. thesis, 230p.
Department of Mineral Resources, 2007, Geological
Map of Thailand, Scale 1: 500,000
Department of Mineral Resources, 2009, The study of
earthquake recurrent interval along the Mae
Chan and Pha Yao active faults in Chiang Rai,
Chiang Mai, and Pha Yao provinces (Mae
Chan and Pha Yao Fault Zone)
(in Thai).
Department of Mineral Resources, 2014, Aftershock
and focal mechanism of the M6.3, 2014 Mae
Lao Earthquake.
Online:http://www.dmr.go.th/download/article
/article_ 20140922090746.pdf
Harnpattanapanich, T., 2006, Engineering Geology
Technical Report on Macroseismic Study.
Engineering Geology Division, Office of
Topography and Geology Surveys and Soil and
Geology Group, Office of Irrigation Region 3,
Royal Irrigation Department (in Thai).
Harnpattanapanich T., 2006, Engineering Geology
Technical Report on Macroseismic of Amphoe
Nam Pad, Uttaradit earthquake of June 5,
2005. Engineering Geology Division, Office
of Topography and Geology Surveys and Soil
and Geology Group, Office of Irrigation
Region 3, Royal Irrigation Department (in
Thai).

5. Metcalfe, I. (2011). Tectonic framework and Phanerozoic
evolution of Sundaland. Gondwana Research.
19, 3–21.
Polachan, S., Pradidtan, S., Tongtaow, C., Janmaha, S.,
Intrawijitr, K. and Sangsuwan, C. (1991).
Development of Cenozoic basins in Thailand,
Marine and Petroleum Geology, 8, 84-97.