By Prof. Mehdi Zare & Farnaz Kamranzad

7.3 magnitude quake in Sarepol-e Zahab

November 19, 2017

On November 12, 2017, at 18:18 UTC (21:48 Iran Standard Time), a major earthquake with the moment magnitude of 7.3 occurred in Kermanshah province, western Iran.

According to the National Center of Broadband Seismic Network of Iran, the epicenter of the earthquake was located at 34.88°N and 45.84°E near the Iran–Iraq border with a depth of 23 km.

The focal mechanism solutions for this earthquake indicate a fault dipping shallowly to the east-northeast, or on a fault dipping steeply to the southwest.

Based on the active fault map of Iran, this earthquake can be triggered by the movement of the Zagros Mountain Front Fault (MFF) in the Sarepol-e-Zahab region.

The event taking as long as 30 seconds was felt in an extended area in Iran, Mesopotamia, the Caucasus, eastern Turkey, Iraq and Syria.

Until November 17, 2017, about 345 aftershocks with magnitudes over 2.5 have been recorded by the Iranian Seismological Center (IRSC) (Fig 1).

The largest magnitude of the earthquake's aftershock sequence was 4.7, which occurred on November 13th.

The strong motion of the November 12, 2017, Mw7.3 mainshock has been recorded by 98 stations of the Iran Strong Motion Network (ISMN) (Table 1).

Among these records, the highest value corresponds to the Sarepol-e Zahab station with an uncorrected PGA of about 684 cm/s2 (Fig 2). The corrected PGA values of the important records will be soon released in subsequent studies.

Based on the preliminary assessments, the maximum intensities and most of the destructions have been reported in the Sarepol-e-Zahab and Qasr-e Shirin cities of Kermanshah province. Until today (Nov. 17), 436 people are killed and over 7,500 injured. Most of the destructions have been reported in the Sarepol-e Zahab and Qasr-e Shirin.

Previous important earthquakes in this area

Farsinaj Earthquake of 13 December 1957, Ms7.1

An earthquake of magnitude Ms=7.6 and mb=6.5 occurred in the Farsinaj region of Kermanshah province on Friday morning, Dec. 13, 1957, at 5:15:00 a.m. local time, (1:45:00 GMT). 

The epicenter of the earthquake was located at 34.35°N and 47.67°E with about 35 km depth. A filed investigation carried out 16 years later (Ambraseys et al, 1973) shows that this earthquake caused heavy damages within an area of 2,800 square kilometers in which 1,119 people were killed and 900 injured and 15,000 left homeless.

Macroseismic evidence suggests a somewhat more moderate epicentral intensity of VII+ (MMI). With the exception of a single aftershock which preceded the main earthquake by about 26 hours and was strongly felt at Kangavar, records of the nearest seismological stations show no trace of important seismic activity in this part of the Zagros during the preceding four months.

The earthquake and its numerous aftershocks destroyed or damaged beyond repair 5,000 housing units out of a total of about 9,000 (more than 55%). Most of the local types of dwellings were one-storey adobe or rubble masonry houses set in mud and covered with heavy flat roofs of tamped earth.

In the larger villages there were a few two-storey adobe houses as well as some one-storey brick masonry buildings covered with Iranian jack-arches or with light roofs of galvanized iron sheets.

A reconnaissance survey disclosed a fracture between Karaj Olia and Karkasar, probably of tectonic origin. As a matter of fact, there was linear topographic features in the form of terraces bearing 130°E. These fractures, which are mainly in alluvium, suggested very recent normal faulting and showed no evidences of lateral motion.

Fig 1. Aftershocks of the 2017 Iran-Iraq earthquake

Table 1. Strong motion records of the 2017 Iran-Iraq earthquake

No

Station Name

Record No

Un. PGA (cm/s2)

Epicentral Distance

Station Code

1

Sarpol-e Zahab

7384/01

684

39

SPZ

2

Goorsefid

7377/01

309

66

GRS

3

Kerend

7302/01

261

66

KRD

4

Loomar

7385

139

161

LUM

5

Eslamabadqarb

7313

123

96

ELA

6

Ravansar

7296

120

70

RVN

7

Homail

7294

93

125

HML

8

Arkvaz-e-Malek Shahi

7378

91

170

AVZ

9

Shoeisheh

7317

88

93

KAT

10

Mahidasht

7295

86

101

MHD

11

Dinevar1

7304

81

143

DIN1

12

Marivan

7287

70

83

MAR

13

Degaga

7310

70

67

DGG

14

Ilam1

7341

69

138

ILA1

15

Badreh

7315

64

197

BDR

16

Soomar

7375

61

106

SUM

17

Kermanshah1

7292

55

120

KRM1

18

Lenjab

7376/01

55

125

LJA

19

Sarv Abad

7290

54

70

SVA

20

Nosood

7297

53

47

NSD

21

Palangan

7279

50

70

PAG

22

Sahne

7303

45

166

SHN

23

Sar Dasht

7289

40

155

SRS

24

Firoozan

7284

36

208

FRA

25

Kamyaran

7278

35

93

KYN

26

Aran

7301

35

163

ARA

27

Pol Dokhtar

7351

35

248

PDK

28

Naqadeh

7291

33

244

NAG

29

Deh Golan

7311

33

146

DGO

30

Holilan

7320

32

161

HEL

31

Dasht-e-Abbas

7332

32

320

DAS

32

Shahin Dej

7293

30

216

SHJ

33

Chalan Choolan

7350

29

304

CHL

34

Sanandaj1

7280

28

114

SAN1

35

Chaghalvandi

7344

28

275

CLV

36

Piranshahr

7288

26

222

PRS

37

Dezaj

7316

26

189

DZJ

38

Dareh Shahr

7298

25

230

DAH

39

Pahle

7314

25

220

PHL

40

Noor Abad

7347

24

206

NRA

41

Eyvan

7338

23

116

EYN

42

Armordeh

7277

22

125

ALV

43

Moosiyan

7381

21

289

MOS

44

Saqez

7318

19

162

SAG

45

Divandarreh

7312

18

159

DIV

46

Shoosh

7356

18

363

SUS

47

Ebrahim-Abad

7299

17

154

EBH

48

Saleh Abad

7309

17

151

SLA

49

Bisheh-Deraz

7372

17

242

BIS

50

Khosro Abad

7300

16

175

KSA

51

Sonqor

7307

16

154

SON

52

Famenin

7283

15

282

FMN

53

Darbastaneh

7333

15

294

DRB

54

Giyan

7286

14

225

GYN

55

Sanandaj2

7281

14

113

SAN2

56

Bagh-Malek

7352

14

518

BGM

57

Shool Abad

7349

14

352

SUL

58

Aleshtar

7343

14

240

ALR

59

Sarab Doreh

7348

14

239

SRD

60

Andimeshk

7371

14

344

AND

61

Dorood

7345

13

325

DRD

62

Kangaver

7306

12

192

KNG

63

Khoram Abad1

7335

12

269

KRA1

64

Mehran

7340

11

189

MER

65

Haftgel

7346

11

504

HFG

66

Kohnoosh

7285

10

217

KNS

67

Mamolan

7336

10

247

MAL

68

Boroojerd

7331

10

278

BRO

69

Abadan

7342

10

543

AAD

70

Ajin

7282

9

185

AJN

71

Kouhdasht

7334

9

212

KDT

72

Qom2

7321

8

456

QOM2

73

Hersin

7305

5

162

HES

74

Mehtarlo2

7319

3

413

MTL2

75

Chahardangeh2

7324

3

498

TH015

76

Tehran69

7367

3

507

TH008

77

Tehran79

7328

2

509

TH010

78

Garmsar1

7326

2

586

GMS1

79

Tehran74

7358

2

510

TH013

80

Tehran26

7362

2

504

TH009

81

Fasham1

7323

1

525

FSH1

82

Tehran90

7329

1

506

TEH90

83

Eyvanaki1

7327

1

564

EYK1

84

Tehran93

7353

1

489

TH018

85

Tehran91

7354

1

506

TEH91

86

Tehran82

7355

1

506

TH001

87

Tehran78

7368

1

508

TH004

88

Tehran70

7360

1

525

TEH70

89

Tehran76

7359

1

509

TH007

90

Tehran47

7361

1

502

TH005

91

Tehran73

7363

1

507

TH014

92

Tehran84

7364

1

499

TH016

93

Tehran85

7365

1

495

TH017

94

Tehran86

7366

1

495

TH019

95

Firoozkooh2

7369

1

631

FRK2

96

Tehran71

7370

1

510

TH003

97

Mosha2

7325

0.86

567

MOA2

98

Bojnoord1 (University)

7330

0.33

1063

BOJ1

Fig 2. The maximum PGA of the 2017 Iran-Iraq earthquake recorded at the Sarpol-e Zahab Station. (record No:7384/01)

*******

Mehdi Zare is a Professor of Engineering Seismology, International Institute of Earthquake Engineering and Seismology (IIEES), and Associate member of Academy of Sciences of Iran.

Farnaz Kamranzad is a PhD Student of Mineral Exploration Engineering, Department of Mining Engineering, College of Engineering at the University of Tehran.

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