* HK shares ease 0.5 percent, materials counters outperform
* Shanghai shares flat, steel and coal plays support
* Nuclear power companies lower after Japan quake
* Turnover thin as market players resist big bets (Updates to midday)
By Vikram S.Subhedar and Emma Ashburn
HONG KONG, March 14 (Reuters) - Hong Kong shares had eased while China's benchmark was flat by midday on Monday in low trading volume as investors resisted making big bets in the aftermath of Japan's massive earthquake.
Japanese stocks fell as much as 6 percent, keeping investors in Asia on the back foot, as automakers, electronics companies and oil refiners shuttered factories to deal with severely damaged infrastructure.
Coal and steel-related issues outperformed in Hong Kong, where the benchmark Hang Seng Index fell 0.51 percent to 23,132.1. The China Enterprises Index of top locally listed mainland companies fell 0.28 percent, helped by a relatively resilient mainland market.
Turnover remained light in Hong Kong at just over HK$30 billion, suggesting investors were still wary.
"It seems the market is getting increasingly sensitive to even the slightest news," said a head trader at an Asian bank in Hong Kong.
The Shanghai Composite Index was flat by the midday trading break as expectations of increased demand for building supplies and better pricing lifted construction-related stocks.
Inner Mongolia Baotou Steel Union Co Ltd jumped by the daily maximum of 10 percent. Yantai Wanua Polyurethanes Co Ltd climbed 4.3 percent.
In Hong Kong, Yanzhou Coal Mining Co Ltd rose 3.2 percent, while China Shenhua Energy Co Ltd was up 2.5 percent on expectations of heavy demand for coal from steel producers.
The sub-index for the materials sector, which includes metals mining companies and steel producers, outperformed with a 0.32 percent gain.
Nuclear power companies were weaker, however. Investors shied away from the sector as the Japanese authorities battled to prevent a nuclear catastrophe following explosions at a power plant.
"People are scared this will affect domestic nuclear power plant-related construction in China," said Cheng Yi, analyst at Xiangcai Securities in Shanghai.
In Shanghai, Dongfang Electric Corp Ltd, a leading nuclear power generation equipment manufacturer, was down 5.7 percent in the heaviest trading volume since October last year. Shanghai Electric Group Co Ltd, another large nuclear power equipment manufacturer, lost 3 percent.
Financials continued to face profit-taking pressure that started in middle of last week, with Bank of China Ltd down 1 percent. China Construction Bank Corp, one of the top performers in the sector over the past month, fell 0.6 percent.
Ping An Insurance (Group) Co of China Ltd shares were suspended in Hong Kong and Shanghai. A source told Reuters the company planned to raise funds via a placement of new shares in Hong Kong. (Editing by Chris Lewis)